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Members of the family Lamippidae are obligate endoparasitic copepods that typically associate with octocorals. In the present work, the association between Lamippe bouligandi and its bathyal sea pen host Anthoptilum grandiflorum was examined. A total of 1463 females and 23 males of L. bouligandi were collected from 195 colonies of A. grandiflorum. Details of the external morphology and digestive organs of the female copepod are used to refine our understanding of its feeding strategy and relationship with the host, and a preliminary overview of the male is provided for the first time. A combination of histology, scanning electron microscopy and laboratory monitoring of live sea pens hosting L. bouligandi were used to elucidate aspects of its life history, including the reproductive cycle, brooding strategy, and embryonic and larval development.

Gersemia rubiformis is a soft coral belonging to the family Nephtheidae, known to provide habitat for many organisms and to play an essential role in benthic ecosystems. The present study examined the relationship between G. rubiformis and the epibiotic amphipod Stenula nordmanni in the coastal waters of eastern Canada. The prevalence of the association was 100% with an average burden of 35 amphipods (mostly juveniles) per coral host. The sex ratio in the amphipods was female-biased and there was a distinct sexual dimorphism, males being significantly larger than females. In a single coral colony, about 38% of female amphipods were found to brood propagules at various stages of development up to juveniles. Upon release, juvenile amphipods were transparent and acquired the pink color characteristic of the adult by feeding on the coral tissues, thereby mimicking the coloration of the host. Ingestion of coral tissues was confirmed by the presence of host sclerites in the digestive tract of amphipods. In turn, amphipods were seen to protect their host by repulsing predatory nudibranchs approaching the coral colony. Together, findings suggest that the amphipods display a specific and obligate mutualistic association with their coral host, considering that they benefit from shelter and food, and the host benefits from active protection against potential predators. The apparent trophic relationship does not appear to generate any detriment to the host. In addition, some of the symbiotic amphipods examined were found to be hosts themselves, to chytrid fungi attached to their exoskeleton.

The demand and high market price for sea cucumber has led to the collapse of wild stocks for many traditional species in Asia and the Indo-Pacific. New species have therefore been introduced to the...

While so-called brown bodies were first defined in the 1950s as colorful aggregates of cells in the general cavity of echinoderms and other marine benthic taxa, their distribution and role have not yet been fully clarified. This work characterized free coelomocytes and corresponding aggregates ("bodies") in the hydrovascular system and perivisceral coelom, as well as those attached on the membranes of the viscera, in the holothuroid Cucumaria frondosa. Responses to the presence of foreign particles were investigated, providing novel insights on the immune system. A total of eight coelomocyte cell types was detected, while aggregates were formed of three to six types of coelomocytes. Only red-colored aggregates were found in the hydrovascular system, whereas brown aggregates were confined to the perivisceral coelom. The encapsulation mechanism of foreign particles injected in the hydrovascular system was monitored. Particles were first gathered by phagocytes and vibratile, crystal, and morula cells into a whitish aggregate that was then covered by hemocytes, imparting a red color to the aggregates. After their transfer to the perivisceral coelom, aggregates became brown and were ultimately expelled through the anus. Finally, a range of stressors (i.e., harvesting method, presence of a predator, and physical injury) was found to increase the abundance of aggregates, thus highlighting the role of these bodies in the immune response of C. frondosa.

Deep-sea nudibranchs (Mollusca: Gastropoda: Heterobranchia) have rarely been reported from eastern Canada. Here we describe range extensions for two species found in the northwest Atlantic Ocean. Tritonia newfoundlandica Valdés, Murillo, McCarthy & Yedinak, 2017 was originally collected on the Flemish Cap off Newfoundland, Canada, and Doridoxa ingolfiana Bergh, 1899 was originally found off western Greenland with further records in Iceland, northern Norway, and southeastern Canada. We extend the northern range of T. newfoundlandica 1067 km along the eastern coast of North America and add occurrences of D. ingolfiana in the Labrador Sea, bridging a 2044 km gap between previous records in Greenland and southern Newfoundland. The latter species thus exhibits a continuous distribution from Svalbard, the Faroe Islands, Greenland, down to the southern tip of the Grand Banks in eastern Canada. Tritonia newfoundlandica was collected in its known depth range, whereas the depth distribution of D. ingolfiana was extended by 30 m to a maximum depth of 1375 m. Both species were collected with numerous nephtheid corals, suggesting that there may be a functional relationship, where the nudibranchs find refuge or food on them.

Methods have been proposed to mitigate the environmental footprint of aquaculture, including co-culture of species occupying different trophic levels. In this study, sea cucumbers Cucumaria frondosa, either from production tanks fed with effluent water from land-based salmon culture over 4 yr or collected from the field, were compared using stable isotope, lipid and fatty acid (FA) signatures as indicators of waste assimilation, health and biochemical composition. Enrichment of δ13C in muscle bands and intestine and of δ15N in muscle bands, gonad and intestine was detected in captive individuals relative to wild individuals, suggesting the uptake and assimilation of waste from salmon culture. The higher levels of FA biomarkers typical of salmon feed (18:1ω9, 18:2ω6 and 20:1ω9) and lower ω3/ω6 ratio in the captive sea cucumbers were also in line with assimilation of the waste. However, male and female sea cucumbers from the co-culture became smaller with time, their organ indices were lower than those of wild individuals (e.g. poorly developed gonad), and their biochemical composition differed: triacylglycerol content was greater in wild individuals and phospholipid content was greater in captive individuals. Also, FA profiles of all tissues differed between the 2 groups, whereas total lipid in muscle bands and gonad remained similar. Overall, results support that co-culture with suspension-feeding sea cucumbers may help mitigate the salmon industry footprint. In turn, the biochemical composition of the sea cucumbers changed, and their reduced size and body indices suggest that this food source does not provide suitable nutrients to sustain growth and reproduction.

Holothuroids (sea cucumbers) are one of the most ubiquitous groups of benthic animals found across diverse marine ecosystems. As echinoderms, they also occupy an important place in the evolutionary hierarchy, sitting close to vertebrates in the deuterostome clade, making them valuable multidisciplinary model organisms. Apart from being ecologically and phylogenetically important, many species are commercially exploited for luxury seafood markets. With the global rise of aquaculture and fisheries, management and protection of these valuable species relies on a better understanding of how their immune systems respond to environmental and anthropogenic stressors. Here, the cellular, hormonal and behavioral indicators of stress in the North Atlantic sea cucumberCucumaria frondosawere examined. The immediate and carry-over (post recovery) effects of a 1-hour exposure to low salinities or to emersion (at two temperatures) highlighted that morphoplasticity inC. frondosawas accompanied by shifts in all monitored indicators. From baseline levels measured in controls, densities of free coelomocytes increased, showing successions of specific cell types and subsequent coelomocyte aggregations, combined with a rise in cortisol levels. These responses mirrored increased fluctuations in cloacal opening rates, decreased force of attachment to the substrate, and enhanced movements and active buoyancy adjustment with increasingly severe stressors. The findings suggest that many systems of sea cucumbers are impacted by stresses that can be associated with harvesting and handling methods, with likely implications for the quality of the processed products. Gaining a deeper understanding of immune and hormonal responses of sea cucumbers is not only of broad ecological and evolutionary value, but also helpful for the development of sustainable fisheries and aquaculture practices, and conservation programs.

Velvet shell, Velutina velutina (Müller, 1776), is a specialist predator of ascidians, like other members of the gastropod family Velutinidae. Globally, invasive ascidians have become problematic, ecologically and economically, yet ecological knowledge of velutinids remains limited. This study outlines the life history and feeding ecology of V. velutina in eastern Canada based on laboratory work complemented by field observations. The life history of V. velutina is closely linked with ascidians, which serve as prey and protection for their egg capsules. Egg capsules were embedded within tunics of Aplidium glabrum (Verrill, 1871) and Ascidia callosa Stimpson, 1852, with a preference for the latter. Seasonal behavioural shifts were consistent annually and corresponded with seawater temperature cycles. Feeding dominated during the coldest months (January–May), growth occurred as water temperature increased to the annual maximum (June and July), transitioning to mating during the warmest period (July–August), and egg capsule deposition dominated as water temperature declined (November–January). Larvae hatched between January and July after 2–4 months of development. Velutina velutina preyed on all ascidian species presented during this study, including golden star tunicate, Botryllus schlosseri (Pallas, 1766), and vase tunicate, Ciona intestinalis (Linnaeus, 1767), two non-indigenous species, although solitary species were preferred.

The environmental control of reproductive processes is central to both fundamental and applied aspects of animal ecology. The present study experimentally assessed how environmental factors modulate gametogenesis and spawning and impact embryo development and survival in the holothuroid Cucumaria frondosa, a cold-water echinoderm with lecithotrophic development. Adults were exposed to three seawater temperatures, four photoperiod regimes, and two food concentrations during 120 days overlapping the natural gametogenic and spawning periods. Among all the treatments tested, exposure to ambient conditions of water temperature (−1 to 3 °C), photoperiod (8 to 13 h of light) and food concentration (3 × 103 ± 896 rotifers g−1 of sea cucumbers d−1) yielded the greatest reproductive output and embryo survival. At pre-spawning, males and females had the highest gonad index (~33%) and where filled with mature gametes. At spawning, females in ambient conditions released the highest number of oocytes (1.2 × 103 oocytes female−1) and yielded the highest embryo survival rates (21% at 20 days post fertilization). Individuals exposed to warmer water temperatures (6 and 12 °C) experienced delayed gametogenesis and did not spawn. Individuals under 24-h light, 24-h dark, and advanced (4 months) photoperiods showed delayed gametogenesis and low numbers of oocytes released; moreover, embryos died within 10 days post fertilization. Individuals fed with high food concentration (6 × 103 ± 982 rotifers g−1 of sea cucumbers d−1) showed similar results to ambient conditions, suggesting that increased food supply neither decreased nor enhanced reproductive output over the experimental period. This study sheds new light on the environmental drivers of reproductive success in C. frondosa, which is of value for developing conservation strategies and mariculture protocols in cold-water holothuroids with lecithotrophic development.

While the study of dispersal and connectivity in the ocean typically centres on pelagic species and planktonic larval stages of benthic species, the present work explores an overlooked locomotor means in post‐settlement benthic stages that redefines their dispersal potential.Members of the echinoderm class Holothuroidea colonize a diversity of marine environments world‐wide, where they play key ecological and economical roles, making their conservation a priority. Holothuroids are commonly called sea cucumbers or sea slugs to reflect their slow movements and are assumed to disperse chiefly through pelagic larvae.The present study documents and explores their unexpected ability to actively modify their buoyancy, leading them to tumble or float at speeds orders of magnitudes faster than through benthic crawling. Two focal species representing different taxonomic orders, geographic distributions and reproductive strategies were studied over several years.Active buoyancy adjustment (ABA) was achieved through a rapid increase in water‐to‐flesh ratio by up to 740%, leading to bloating, and simultaneously detachment from the substrate. It occurred as early as 6 months post settlement in juveniles and was recorded in wild adult populations. In experimental trials, ABA was triggered by high conspecific density, decreasing salinity and increasing water turbidity. Based on field video footage, ABA‐assisted movements generated speeds of up to 90 km/day.These findings imply that displacement during planktonic larval stages may not supersede the locomotor capacity of benthic stages, challenging the notion of sedentarity. Combining the present results and anecdotal reports, ABA emerges as a generalized means of dispersal among benthic animals, with critical implications for world‐wide management and conservation of commercially and ecologically significant species., This study documents the unexpected ability of so‐called sessile or sedentary benthic marine animals (e.g. sea cucumbers) to actively modify their buoyancy to tumble or float at speeds orders of magnitudes faster than anticipated. These findings redefine the locomotor capacity of benthic animals, challenging the notion of sedentarity, with critical implications for worldwide management and conservation of commercially and ecologically significant species.

The present study investigated methods to trigger spawning and artificially induce oocyte maturation in the commercial cold-water suspension-feeding sea cucumber Cucumaria frondosa. Spawning occurred after exposure to live phytoplankton, commercial phytoplankton paste, and conspecific sperm. Live phytoplankton at 1 × 105 cells ml−1 induced the highest proportion of females to spawn (mean of 56%); promoted the greatest oocyte release (mean of 19,200 oocytes female−1), best quality of eggs and highest survival of embryos (65%; 20 d post fertilization). More concentrated live phytoplankton (1 × 106 cells ml−1) triggered 43% of the females to release ~16,100 oocytes female−1 and survival rates 20 d post fertilization were lower (50%). Both phytoplankton paste treatments (1 × 105 and 1 × 106 cells ml−1) yielded intermediate results in terms of percent spawning females (26%), abundance of oocytes released (11,000 and 7300 oocytes female−1, respectively), quality of eggs, and survival of embryos (44 and 50%, respectively). Sperm from conspecific (2 and 10 × 106 spermatozoa ml−1) induced the lowest proportion of females to spawn (16%) with release of 3000 and 1700 oocytes female−1, respectively; furthermore, all embryos died within 10 d post fertilization. Results for males were slightly different: spawning was more frequent (63%) in the sperm treatment at 2 × 106 spermatozoa ml−1 followed by live phytoplankton at 1 × 106 and 1 × 105 cells ml−1 (43%), and phytoplankton paste at 1 × 105 cells ml−1 (46%); the lowest spawning success was observed for phytoplankton paste at 1 × 106 cells ml−1 and conspecific sperm at 10 × 106 spermatozoa ml−1 (26%). Thermal shock, desiccation, potassium chloride (injection or bath), and serotonin (injection) did not induce spawning in C. frondosa. When oocytes isolated from mature ovaries were exposed to three different concentrations of 1-Methyladenine (1-MA), Dithiothreitol (DTT), 2,3-Dimercapto-1-propanol (BAL), and L-cysteine (L-cyst), DTT at 10−1 M induced the highest proportion of oocytes (48%) to shed follicle cells (i.e. ovulate); whereas other treatments induced only 2–6% of ovulation, similar to the control (seawater). All oocytes that shed follicle cells remained unfertilizable. Overall, live phytoplankton emerged as the most suitable spawning trigger for C. frondosa, a Dendrochirotida that produces maternally-provisioned oocytes. In the context of expanding sea cucumber aquaculture, this finding provides a tool to maximize the availability of gametes in this cold-water species, with possible applicability to similar commercial dendrochitotids.

Recent efforts have been devoted to the link between responses to non-physical stressors and immune states in animals, mostly using human and other vertebrate models. Despite evolutionary relevance, comparatively limited work on the appraisal of predation risk and aspects of cognitive ecology and ecoimmunology has been carried out in non-chordate animals. The present study explored the capacity of holothuroid echinoderms to display an immune response to both reactive and anticipatory predatory stressors. Experimental trials and a mix of behavioural, cellular and hormonal markers were used, with a focus on coelomocytes (analogues of mammalian leukocytes), which are the main components of the echinoderm innate immunity. Findings suggest that holothuroids can not only appraise threatening cues (i.e. scent of a predator or alarm signals from injured conspecifics) but prepare themselves immunologically, presumably to cope more efficiently with potential future injuries. The responses share features with recently defined central emotional states and wane after prolonged stress in a manner akin to habituation, which are traits that have rarely been shown in non-vertebrates, and never in echinoderms. Because echinoderms sit alongside chordates in the deuterostome clade, such findings offer unique insights into the adaptive value and evolution of stress responses in animals.

Sea anemones are often presented as a major component of benthic communities and described as ecologically important in benthic food webs. However, studies on the trophic ecology of deep-sea species are rare. Here, the feeding habits and dietary sources of three species of bathyal sea anemones (Actinostola callosa, Actinauge cristata, Urticina sp.) from the Northwest Atlantic were studied in a multi-faceted approach including stable isotopes, gastrovascular contents, lipid and fatty acids analysis and observations in a mesocosm. Stable isotope analysis showed that A. callosa sits at a slightly lower trophic level than A. cristata and Urticina sp. and that the two latter species rely on different carbon sources at roughly the same trophic level. The gastrovascular cavity contents and mesocosm study revealed that all three species ingest a variety of food items, from inorganic materials to a diversity of metazoans, including whole large prey. Total lipid content varied across species and was highest in Urticina sp. Phospholipids constituted the main lipid class in all three species, with consistently high levels of wax ester storage lipids. All sea anemones were also characterized by high proportions of mono and polyunsaturated fatty acids (MUFA and PUFA) as well as ω3 and ω9 FAs, and strikingly low proportions of 20:4ω6 (ARA). High values of 20:5ω3 (EPA), 20:1ω9 and 22:1ω11(13) evoke a diet centered on zooplankton, with notable particularities. For instance, Urticina sp. had the highest PUFA to saturated FAs ratio, indicative of carnivory. Overall, results suggest that the three sea anemone species occupy different niches in the spectrum of opportunistic polyphagous predation/feeding, with Urticina sp. relying chiefly on more energetic and larger prey and A. cristata targeting smaller zooplankton, foraminifera and particulate food, highlighting that large actinians play diverse roles in benthic food webs.

As deep-sea benthic ecosystems of continental margins provide numerous functions and services to humans, a better understanding of these key habitats and their communities is needed to help predict climate-driven shifts and support conservation efforts. Here stable isotope (δ13C and δ15N), elemental (%C, %N, and molar C:N), and fatty acid (FA) composition of 50 different deep-sea species, belonging to 7 major taxa, were analyzed in order to characterize their diet and trophic position, and to study the fate of energy and essential nutrients in the food web. In addition, relationships between depth and biochemical signatures (δ13C, δ15N, %C, %N, C:Nmol, and FAs) were also investigated. In this regard, %C, oleic acid (18:1ω9), and arachidonic acid (ARA, 20:4ω6) increased with depth. While the increase of %C was likely due to the preferential assimilation of the more nutritious N along the gradient, that of 18:1ω9 was presumed to reflect the need for longer-term energy reserves in deeper organisms, and that of ARA to indicate a higher reliance on the benthic trophic pathway at greater depth. Analyses also revealed that the focal deep-sea invertebrates occupied three trophic levels, whereas the weak correlation between δ13C and δ15N indicated that two or more trophic pathways were represented. Several feeding modes were also recognized within the assemblage. The lowest trophic positions were occupied by sponges most likely feeding on bacteria. Intermediate positions were mainly occupied by suspension feeders (e.g. sea anemones, corals), detritivores (e.g. the sea urchin Phormosoma placenta), and predators on small infaunal animals (e.g. the sea star Leptychaster arcticus). Conversely, predator/scavengers (e.g. various sea stars, gastropods, polychaete worms) occupied the highest trophic positions, together with sponges that were determined to be either carnivorous (e.g. Iophon piceum), or to feed on 15N- and 13C-enriched organic matter. Energetic compounds (i.e. 20:1ω11(13), 20:1ω9, and 22:1ω7) and essential nutrients (i.e. ARA) increased in proportion across the trophic levels of this food web, emphasizing the importance of certain dietary FAs for optimal organism health, and the key role of benthic communities in carbon cycling.

This study presents new records for 4 eulimid species (Gastropoda, Eulimidae) including Melanella eburnea (Megerle von Mühlfeld, 1824), Melanella hypsela (Verrill & Bush, 1900), Melanella sp., and Eulimostraca encalada Espinosa, Ortea & Magaña, 2006 found on the body wall of the sea cucumber Holothuria mexicana in Belize. Three of these records (M. hypsela, M. eburnea, and E. encalada) represent a first for the Western Caribbean ecoregion and close a distributional gap for these species in the Caribbean. The geographic distribution of M. eburnea is thereby expanded by ~800 km; M. hypsela by ~1,200 km and E. encalada by ~970 km in the Tropical Northwestern Atlantic province. This article presents for the first time H. mexicana as a new host record for E. encalada.

While sea cucumbers have been fished in Belizean waters for ∼ 20 years for trade through Guatemala and the local Asian market in Belize, harvesting for export to international markets only started with the establishment of the sea cucumber fishery regulations in 2009. The fishery included two main species, Holothuria mexicana and Isostichopus badionotus but only the former was legally managed by the Belize Fisheries Department through a closed season and catch reporting. By 2016, H. mexicana was considered overfished and in 2017, the entire fishery was closed. Here we provide a comprehensive analysis of this fishery in Belize from 2009–2016 with the goal to make recommendations for policy development. This study combined key informant interviews with secondary data collection and observation of sea cucumber fishing, landing and processing. Fishers hand-picked sea cucumbers using mask and snorkel and sold their catch to exporters or middlemen. Sea cucumber harvesting increased fishers’ income to 154 times the minimum wage in 2010 and 5 times the minimum wage in 2016, concurrent with a drastic decline of stocks. Some fishers rated sea cucumber harvesting as their primary fishing activity but knew very little about their biology or ecology. They were concerned about the decrease in catch that forced them to fish in deeper waters and about the illegal fishing by Guatemalan and Honduran fishers in Belizean waters. Sea cucumbers sold locally since 2009 were neither reflected in the market economy nor used to adjust the Total Allowable Catch by the Belize Fisheries Department. Maintaining the long-term sustainability of this fishery will rely on greater investments in enforcing fisheries regulations, in scientific research to determine the viability of sea cucumber fishing, and in the education of fishers. A closer collaboration with fishers is necessary to adequately inform future management decisions on the socioeconomic consequence of overfishing.

The present study examined morphological and behavioural development in post-settled juveniles of the commercial sea cucumber Cucumaria frondosa, in an effort to assist captive breeding and conservation initiatives. Juveniles developed all 10 tentacles within 16 months; they had 9 podia and measured 4.6 mm in length after 21 months. Scaling between body length and number of podia was isometric, whereas dorsal tentacle metrics showed negative allometric scaling, indicating that growth was accompanied by a decreasing tentacle to body size ratio. Dorsally-oriented tentacles developed and ramified faster, showing 6 ramifications after 21 months, when ventrally-oriented tentacles only displayed one. This asynchrony underlines the distinctive roles of dorsal vs. ventral tentacles during the early months. The former were strictly used to capture plankton from the water column; whereas the latter were used for anchorage and feeding on deposited material. Ossicles of the body wall increased in length and thickness, and became slightly curved and rounded in older juveniles. Light intensity and water flow tolerance increased with age; from 25 lx and 5 cm s−1 in 1-month-old individuals, to >50 lx and 10 cm s−1 in 6, 12, and 21-month-old individuals, consistent with migration from sheltered to more exposed locations. Moreover, 1 and 6-month-old juveniles preferred rock substrates and black or red background colours; whereas 12 and 21-monthd-old individuals favoured substrates of coralline algae and a red background, also indicative of increasing affinity with sunlit environments and a shift from benthic to planktonic feeding. Juveniles of all age classes were feeding (i.e. had deployed tentacles) 24 h a day and commonly sought vertical surfaces. Together, the findings shed light on the early juvenile ecology of this cold-water suspension-feeding sea cucumber. Considering the expansion of sea cucumber fisheries and growing interest in the aquaculture of C. frondosa, this work also provides a framework for improved stock management and culture protocols.

Background Electromagnetic pulses that precede earthquakes, and the ensuing crust deformations and vibrations, have been associated with unusual animal behavior (UAB), most commonly in terrestrial species but also in certain marine species, chiefly in the Chordata phylum (eg fish, cetaceans). Goals . The present study explored the occurrence of earthquake-related UAB in an entirely new marine phylum, the Echinodermata. Methods. Formal and informal surveys conducted by fishing vessels and pre- and post-earthquake along the southern coast of Belize (Central America) were collated. Results The first cases of post-earthquake UAB in echinoderms were documented. They involved thousands of individuals of the holothuroidsIsostichopus badionotus and Holothuria mexicana spawning on May 29 2009 and January 10 2018, respectively. These rare accounts represent the first direct correlation between an earthquake and spawning activity, which occurred outside the normal spawning season and at an unusual time of day. Conclusion. While a growing number of reports indicate that many terrestrial and a smaller number of marine species can change their behavior before and during an earthquake, post-earthquake effects related to reproduction have apparently never been reported before in the animal kingdom. While underlying mechanisms remain unclear, holothuroid echinoderms may be reacted directly or indirectly to seismic activity, or the pressure change generated by it.

Among arthropods, pycnogonids are generally considered of minor ecological significance in marine ecosystems. However, the fact that they can host a wide diversity and high abundance of epibiotic organisms suggests that their role in benthic communities may be underestimated. The present study characterized the diversity, dynamics and role of the epibiotic community associated with deep-sea pycnogonids (Nymphon hirtipes). Despite their small size, they hosted a mean of 62 macro-organisms belonging to at least 26 species from 11 different phyla. Foraminifera was the dominant phylum while other phyla, such as Bryozoa, Cnidaria (Hydrozoa), Porifera and Brachiopoda were common. The macro-epibiont burden varied from 1 to 235 organisms per pycnogonid; it was consistent across depths and locations but fluctuated as a function of sex and of the reproductive state in males. Specifically, most colonized individuals were females, which are larger and thus offer more surface for epibionts. Among males, burdens peaked in those carrying larvae. Maximum epibiont burden and coverage was correlated with the cessation of grooming at the beginning of the breeding period. Micro-epibionts consisted of bacterial mats covering most body parts. Several epibionts were estimated to have negative effects on their host (e.g. increasing drag, preventing mating, decreasing limb mobility and impeding feeding). However, because this species dies after reproducing, epibiosis may be considered as a positive trade-off since it may provide food to the mobile juveniles living on the male for several months. Furthermore, epibionts could be used as camouflage during this period. N. hirtipes has been identified as a common component of the benthofauna in the deep sea of the North Atlantic and Arctic Oceans, and the present study indicates that it displays the greatest diversity and burden of associates ever reported among pycnogonids.

13 pages, 8 figures, 1 tables, aupplementary data https://doi.org/10.1016/j.jembe.2021.151607, The feeding behaviour of deep-sea animals is largely understudied despite being of relevance to assess changes in ecosystems functioning in the face of anthropogenic impacts and climate regime shifts. Here, time-lapse videography in dark, cold-water, flow-through laboratory settings was used to study the behaviours of a gastropod (Buccinum scalariforme) and three sea stars (Ceramaster granularis, Hippasteria phrygiana, Henricia lisa) from the bathyal Northwest Atlantic, to build knowledge on their foraging strategies (i.e. food search, assessment and handling). In all species tested, the presence/absence of a palatable food source modulated the speed and directionality of movements. Approach paths were erratic in the absence of palatable food and targeted in its presence: B. scalariforme, C. granularis and H. phrygiana, moved in straight line to the food, while H. lisa moved either in straight line or counterclockwise loop. The four species traveled at mean speeds of 2.9, 0.2, 0.7, and 0.6 cm min−1, respectively. At the finer scale, unprecedented pulses in displacement speed were detected, varying in amplitude and frequency depending on the food item. The results also support more generalist diets and broader scavenging habits in deep-sea sea gastropods and sea stars than assumed from previous studies and knowledge of shallower-water counterparts. Depth-related food limitation may drive greater flexibility in foraging strategies and acceptable food items, This work was supported in part by the Natural Sciences and Engineering Research Council of Canada (NSERC) via grants awarded to A.M., J.A. is a member of the Tecnoterra Associated Research Unit (ICM-CSIC/UPC) and supported by the Spanish Government through the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000928-S)

In shallow benthic communities, sponges are widely recognized for their ability to contribute to food webs by cycling nutrients and mediating carbon fluxes through filter feeding. In comparison, little is known about filter feeding in deep-sea species and how it may be modulated by environmental conditions. Here, a rare opportunity to maintain live healthy deep-sea sponges for an extended period led to a preliminary experimental study of their feeding metrics. This work focused on demosponges collected from the continental slope of eastern Canada at ~ 1000 m depth. Filtration rates (as clearance of phytoplankton cells) at holding temperature (6 °C) were positively correlated with food particle concentration, ranging on average from 18.8 to 160.6 cells ml −1 h −1 at nominal concentrations of 10,000–40,000 cells ml −1 . Cell clearance was not significantly affected by decreasing seawater temperature, from 6 °C to 3 °C or 0 °C, although two of the sponges showed decreased filtration rates. Low pH (~ 7.5) and the presence of a predatory sea star markedly depressed or inhibited feeding activity in all sponges tested. While performed under laboratory conditions on a limited number of specimens, this work highlights the possible sensitivity of deep-sea demosponges to various types and levels of biotic and abiotic factors, inferring a consequent vulnerability to natural and anthropogenic disturbances.

As increasing anthropogenic CO2 emissions are absorbed by the oceans, a decrease in seawater pH is expected to occur, causing what is now termed ocean acidification (OA). Deep-sea species have been greatly understudied with respect to OA, even though their response may differ from those evidenced so far in shallow-water taxa. The polychaete worm Ophryotrocha sp. collected at bathyal depth was held and reproduced for several years, offering a rare opportunity to study environmental effects in a member of a deep-sea community. This hermaphroditic species exhibits well defined seasonality in feeding and reproduction and its development and growth have been characterized. The purpose of the present study was to explore the effects of OA on gametogenesis following exposure to a 0.4 unit pH decrease under realistic conditions over 26 weeks. Opportunistic assessments of spawning and development were also conducted. A flow-through design allowing for natural fluctuations in pH, temperature and salinity was used. Individuals exposed to low pH/high ρCO2 produced larger and more abundant oocytes but fewer spermatozoa, compared to individuals in ambient conditions. However, lower effective fecundity (number of eggs laid) was ultimately recorded under low pH conditions, together with slower development of the embryos and larvae. Microstructure of the body wall, and appearance and elemental composition of chaeta were not affected. Despite its ability to live and reproduce normally for years in the laboratory, a realistic decrease of pH in the environment of Ophryotrocha sp. led to reproductive disruption, highlighting its potential vulnerability to OA.

Specimens of the neogastropod Buccinum scalariforme (60–70 mm shell height) collected between 700 and 1450 m depth along the continental slope of eastern Canada were kept for 4 years in mesocosm settings. Their mating, spawning and development were assessed, thereby generating the first complete life cycle account of a deep-sea gastropod. Egg laying occurred in March and September, with a total of 9 egg masses laid in 2013 and 2015, coinciding with periods of maximum deposition of particulate organic matter (phytodetritus). Oviposition lasted 2–3 days and the female protected the egg mass for ~3 more days until it had hardened. Typically, egg masses contained 50–75 egg capsules, each measuring 5–8 mm in diameter. A capsule contained between 100 and 150 spherical eggs (300–500 µm) of which ≤50 developed into embryos. Potential fecundity calculated from the entire egg mass at spawning was between 1500 and 2250 propagules; it drastically decreased over ~4–5 months of development to an effective fecundity of 30–50 juveniles emerging from the mass (0–2 juveniles per capsule). Development went through early embryonic stages in ~15 days and reached the trocophore in 15–21 days, followed by intracapsular veliger larva (480 µm) and intracapsular pediveliger (~1000 µm) after ~90 days. Completion of development relied on oophagy and adelphophagy. The juveniles hatched at a shell height of 1–2 mm and consumed the capsule membrane. Over 2.5 years, they reached a maximum size of ~8–10 mm shell height at an average of 9.8 µm day −1 . Estimations indicate that B. scalariforme could require between 20 and 50 years to reach maximum adult size. Large gastropods like B. scalariforme are among the most abundant motile benthic invertebrates of the bathyal zone of eastern Canada. Knowledge of their reproductive biology constitutes a first step in assessing their vulnerability and resilience to ever growing anthropogenic pressures, including fisheries, and oil/gas exploration and exploitation.

Objectives Pasteurella bacteraemia is rare, but has been associated with a high mortality rate. The aim of this study was to estimate the impact of comorbidities on patients with Pasteurella bacteraemia. Methods All cases of Pasteurella bacteraemia in adults treated in our centre between January 2008 and December 2017 were included retrospectively and compared with cases identified in a systematic review of the literature via MEDLINE covering the years 1951–2017. The epidemiological, bacteriological, and clinical data were collected, as well as the instances of death after 30 days. Results Twenty cases of Pasteurella bacteraemia identified in our centre and 99 cases from the literature review were included. A major comorbidity was found in 80/119 (67.2%) patients. The death rate at 30 days was 31.1%. The most common comorbidities were cirrhosis, immunosuppressive therapy, and malignant diseases. Age was not associated with mortality. On multivariate analysis, the only factor associated with mortality was a major comorbidity (odds ratio 2.78, 95% confidence interval 1.01–7.70; p = 0.04). Conclusions This study confirms the high mortality rate and highlights the importance of the host background, independent of age, in Pasteurella bacteraemia. Clinicians should be aware of the comorbidities in cases of Pasteurella infection, due to the poor prognosis of bacteraemia.

Echinoderms are favored study organisms not only in cell and developmental biology, but also physiology, larval biology, benthic ecology, population biology and paleontology, among other fields. However, many echinoderm embryology labs are not well-equipped to continue to rear the post-embryonic stages that result. This is unfortunate, as such labs are thus unable to address many intriguing biological phenomena, related to their own cell and developmental biology studies, that emerge during larval and juvenile stages. To facilitate broader studies of post-embryonic echinoderms, we provide here our collective experience rearing these organisms, with suggestions to try and pitfalls to avoid. Furthermore, we present information on rearing larvae from small laboratory to large aquaculture scales. Finally, we review taxon-specific approaches to larval rearing through metamorphosis in each of the four most commonly-studied echinoderm classes—asteroids, echinoids, holothuroids and ophiuroids.

The suspension-feeding sea cucumber Cucumaria frondosa is widely distributed in cold waters and is commercially exploited in the North Atlantic. While the species is considered to have potential for aquaculture, its feeding and reproductive biology differs markedly from that of currently cultivated sea cucumbers. Here, for the first time, the influence of food sources on the condition of C. frondosa was experimentally tested. Individuals were fed with either diatoms or fish eggs for 3 months. Specific growth rate (SGR), organ indices, fecundity, gonad maturity and profiles of lipids and fatty acids (FA) in tissues were compared among treatments and with sea cucumbers collected from the field. Individuals fed with fish eggs showed higher SGR and organ indices than all other treatments. The highest proportion of large oocytes was also found in gonad tubules of females from the fish egg treatment, although individuals fed with diatoms were the only ones in which spontaneous spawning occurred. Moreover, gonad and muscle tissues of sea cucumbers from the fish egg treatment presented the highest levels of lipids and essential FA. In contrast, non-fed sea cucumbers showed negative SGR, relatively low female fecundity and low concentrations of lipids and FA in tissues. While the fish egg diet presented several obvious benefits, phytoplankton remains an important source of carotenoids, which are vital for vitellogenesis in echinoderms. This indicates that mixed diets rich in lipids, essential FA and carotenoids can be further investigated to optimize growth and reproductive output of this species in captivity.

Sea cucumber is one of the top five luxury seafoods in Asia and its commercialization primarily revolves around the processed body wall. Hence, live transport and storage of sea cucumbers prior to processing must preserve the condition of the body wall and underlying muscles. Unlike most commercial shellfish on which industry standards are chiefly based, sea cucumbers lack a protective exoskeleton and have the ability to autolyze. Here, we tested the efficacy of different live storage methods on Cucumaria frondosa , a commercial species that is widely distributed in the North Atlantic and the Arctic. Current technologies and low-cost variants were experimentally tested under conditions prescribed for the transport of seafood in Canada. Markers of post-storage health, body wall condition and muscle integrity were compared among treatments. The most common method currently in use (icing and salting) yielded the highest rates of mortality and skin necrosis, whereas iced seawater emerged as the best storage condition. These findings should help stakeholders adapt their methodologies to optimize the exploitation of temperate and cold-water sea cucumber resources.

While the suspension-feeding sea cucumber Cucumaria frondosa is commercially exploited in the North Atlantic and is considered to have potential for integrated aquaculture, the impact of environmental conditions on its behaviour and population structure remains incompletely understood. The present study showed that adults are not photosensitive; they do not exhibit any preference for either illuminated or shaded areas. Within each photoperiod treatment, analyses of the daily activity cycle revealed that the proportion of individuals with feeding tentacles deployed did not change over time; however, the proportion of moving individuals increased in the dark phase under the 12 h light/12 dark regime, but remained constant under continuous light or darkness. Hence, from an aquaculture perspective, long days (i.e. summer photoperiod) might decrease the time spent moving in favour of feeding, potentially shifting the energy budget toward faster growth. Variations in phytoplankton concentration modulated the deployment of tentacles but did not trigger any displacement toward the food source, indicating that feeding responds directly to the presence of food. Moreover, C. frondosa exhibited a clear preference for substrates composed of bare rocks and rocks with coralline algae and displayed a weak preference for darker substrate backgrounds. Together, these findings highlight how some key environmental factors can govern the feeding, locomotor activities, and eventual distribution of cold-water suspension-feeding sea cucumbers.

While reproduction in deep-sea corals remains incompletely understood, there is a particularly crucial shortage of information related to corals living in deep waters of the Arctic Ocean. In the present study, colonies of the deep-sea pennatulacean coral Umbellula encrinus were collected in Baffin Bay (High Canadian Arctic) at bathyal depths between 2006 and 2010. From examination of gamete sizes, maturity levels and densities at several time points, U. encrinus was determined to be a gonochoric species with an equal sex ratio and a broadcast-spawning strategy. Fully mature oocytes measured between 800-950 μm in diameter, consistent with lecithotrophic larval development. Potential fecundity was ∼4200 mature oocytes colony−1 and ∼5300 mature spermatocysts colony−1. Gametogenesis was synchronous between sexes; a single main cohort of oocytes and spermatocysts was seen to increase in size throughout the year. Gametogenetically mature colonies were detected in late June during the earliest possible spring samplings. Spent colonies were detected in July and August. Early stages of gametogenesis appeared in early September shortly after the spawning months and more advanced growth stages occurred in late September and early November, after which time sampling was prevented by ice cover. The spawning season in U. encrinus appears to occur once a year, closely following the disappearance of the ice cover in early spring, when chlorophyll-a in Baffin Bay increases. The initiation of gametogenesis coincides with a period of sustained phytoplankton production and continues until the entire bay freezes over in fall. Since mature gametes were found in both male and female colonies just after the spring melt, gamete maturation likely continues under the ice. Both depth and latitude were shown to impact gamete development and fecundity in U. encrinus, with more advanced and fertile colonies occurring in deeper water and at higher latitudes.

The population and reproductive biology of the commercial sea cucumber Holothuria mexicana (Ludwig, 1875) was studied in Southern Belize (Caribbean Sea), including the sex ratio, size at sexual maturity and reproductive cycle, as well as the size structure among habitats located inside and outside protected areas. Individuals found inside marine protected areas were consistently larger than individuals found outside these boundaries. The male:female sex ratio was 1.1:1.0 with a unimodal size distribution composed mainly of sexually mature individuals (87 %). Size at sexual maturity was established to be ~10 cm based on measures of gamogenetically mature individuals during the peak of the gametogenic maturity period. Juveniles and small adults measuring ≤ 15 cm (13 %), were collected exclusively in sandy and muddy areas of seagrass habitats associated with mangroves. Larger adults were commonly found on hard substrates in both seagrass-associated and coral-reef-associated habitats. Based on histology and gonad indices, the first sign of early gametogenesis was detected in August in both sexes. Gametes developed and matured throughout the colder months between November and February. Decreases in gonad index in both years suggest annual spawning, starting in March-April 2014 (single major event) and March-April and July-August 2015 (two smaller events) for both males and females. The spawning periods were correlated with warmer or increasing temperatures, low rainfall and increasing or high chlorophyll-a concentrations. These data will hopefully guide management and protection of the natural populations of H. mexicana, which are already suffering from overfishing in Belize and neighboring countries.

Although hydrostatic pressure is one of the most prominent abiotic drivers of faunal bathymetric ranges, it is one of the least understood. To better understand hyperbaric constraints on depth distributions, we explored responses to high pressure of adult echinoderms from eastern Canada. The sea urchin Strongylocentrotus droebachiensis, the sea star Leptasterias polaris and the sea cucumber Cucumaria frondosa were exposed to various pressures within and beyond their known bathymetric distribution (i.e. surface pressure; pressure at the midpoint in bathymetric distribution; pressure at twice the maximum depth in the species bathymetric distribution) for different durations (24 h, 72 h, 9 days). Survival was compromised by exposure to the highest pressure levels, with the sea urchin exhibiting the highest mortality. After 72-h exposure, mortality was observed for sea urchin and sea cucumber individuals while all sea star individuals survived. Following 9-day exposure of sea star individuals to high pressure, 100% mortality occurred. Exposure to pressures typical of natural distributions had little effect on the selected health and motor metrics. Pressures atypical of natural ranges negatively affected the motor functions of all species, irrespective of exposure duration. During and after 24-h exposure, feeding was reduced in sea urchin and sea cucumber individuals, but was unchanged in sea star individuals. Overall, there were no clear signs of acclimation to high pressure following sustained periods of exposure in any species. These results highlight constraints applied by hydrostatic pressure beyond current bathymetric ranges on life-sustaining behaviours in echinoderms. The potential of long-lived echinoderms to survive downward migration to greater depths is species-specific, suggesting there may be winners and losers in the face of near-future climate-driven migration patterns.

Although movement in response to environmental conditions represents a fundamental link between animal behaviour and population ecology, it is rarely investigated in suspension feeders because they are generally perceived as sessile. Here, the interplay between water flow and fine locomotor and feeding behaviours was experimentally investigated for the first time in a free-moving suspension-feeding sea cucumber ( Cucumaria frondosa ; Echinodermata, Holothuroidea) using time-lapse videography in a mesocosm setting. Individuals moved away from static conditions in the weakest flow treatment and fled the strongest flows (>40 cm s −1 ) in the more dynamic treatments. The tentacles of individuals located in areas with flows of ≥40 cm s −1 was aligned with the direction of the current, whereas in flows −1 , they were typically perpendicular to the direction of flow. Tentacle deployment and insertion rates (i.e. feeding rate) increased with flow, from 0.95 min −1 at 10 cm s −1 to 1.13 min −1 at 40 cm s −1 . Three modes of locomotion were detected. Forward crawling was most frequent at flows ≤40 cm s −1 , passive rolling dominated at flows >40 cm s −1 and active rolling occurred randomly at flows between 0 and 120 cm s −1 . Overall, the flow regime favoured by C . frondosa was determined to be between 21 and 40 cm s −1 , under which an optimal balance between efficient food capture and energy expenditure for attachment to the bottom was presumably found. These findings provide insight into the distribution and population dynamics of suspension-feeding holothuroids, and may also assist the fisheries management and aquaculture development of commercial species.

Whole-body chimaeras (organisms composed of genetically distinct cells) have been directly observed in modular/colonial organisms (e.g. corals, sponges, ascidians); whereas in unitary deuterostosmes (including mammals) they have only been detected indirectly through molecular analysis. Here, we document for the first time the step-by-step development of whole-body chimaeras in the holothuroid Cucumaria frondosa , a unitary deuterostome belonging to the phylum Echinodermata. To the best of our knowledge, this is the most derived unitary metazoan in which direct investigation of zygote fusibility has been undertaken. Fusion occurred among hatched blastulae, never during earlier (unhatched) or later (larval) stages. The fully fused chimaeric propagules were two to five times larger than non-chimaeric embryos. Fusion was positively correlated with propagule density and facilitated by the natural tendency of early embryos to agglomerate. The discovery of natural chimaerism in a unitary deuterostome that possesses large externally fertilized eggs provides a framework to explore key aspects of evolutionary biology, histocompatibility and cell transplantation in biomedical research.

Pycnogonids (sea spiders) are commonly collected at bathyal and abyssal depths all around the world; however, little is known about species from deep-water habitats. The present study explores the life history of Nymphon hirtipes collected in northeastern Newfoundland between 700 and 1450 m depth and monitored in mesocosms for over 2 years. The pycnogonids were found in association with octocorals, hydrozoans and sea anemones. Adult females developed mature oocytes between June and August. Paired mating followed by oviposition occurred between early July and mid-October. Up to three egg masses were brooded by each male. It took a maximum of 4 months for the propagules to hatch from the egg mass. Offspring developed from walking leg-bearing larvae to early juveniles over the next ~5 months before leaving the male’s protection. Mating and oviposition coincided with the highest water temperatures of the annual cycle and dispersal of juveniles occurred in spring, when phytodetritus deposition was high and as ocean temperature rose markedly. All the females died after oviposition and the males ~9 months later, after juvenile dispersal. The sex ratio of mature individuals (~55–60 mm leg span) was 2 males for 3 females. Fecundity was estimated to be 184–288 eggs per adult female. Adults of N. hirtipes were seen feeding on hydrozoan polyps, small sea anemones (Stephanauge nexilis) and nudibranchs. Larvae and early juveniles did not feed while brooded by the male. Upon dispersal, their feeding apparatus became functional and they began feeding on hydrozoan polyps. After 13 months of growth post hatching, the juveniles reached ~21 mm leg span. Curve fitting estimated that ~7 years are required to reach the adult size of 55 mm leg span.

Our study focused on the precise reproductive behavior of the starfish Leptasterias polaris (Muller and Troschel) before and during spawning--a subject of much speculation and evident ecological importance. Between the third week of December 1992 and mid-January 1993, we observed spawning in the laboratory that roughly corresponded to field observations in the Lower St. Lawrence Estuary. In experimental tanks provided with natural environmental conditions, the spawning was preceded by 7 to 8 weeks of complex aggregative interactions among the starfish. The individuals, which usually avoid each other, began to make discreet arm contact, which intensified with time and eventually led to the superposition of two or more starfish, independently of sex. The interactions seem to be associated with decreasing temperature, because aggregative and spawning behaviors were not observed under stable temperature conditions. Male spawning is first initiated when the temperature falls to about 2{deg}C during minimum daylength (9 h.d-1). In seawater, the spermatozoa are negatively buoyant and tend to deposit as a sticky film on the substrate, where they enter a state of low activity. Stimulated by male spawning, females spawn on the layer of sperm, which is reactivated by contact with the oocytes, ensuring fertilization. In the laboratory, the fertilized eggs undergo first cleavage in 45 h, become brachiolaria in 40 days, and form fully developed young starfish within 5.5 to 6 months, synchronously with populations in the field. The embryos develop at the same rate even when not brooded, suggesting that the brooding behavior in L. polaris serves mainly to keep the eggs clean, healthy, and protected against predation.

In spite of increasing naval activities and petroleum exploration in cold environments, there is currently a paucity of tools available to monitor oil contamination in boreal marine life, especially in sedentary (non-fish) species that dominate benthic communities. This research aimed to identify biotic sources of variation in biomarkers using subarctic echinoderms, and to identify suitable biomarkers of their exposure to hydrocarbons. The focal species included the sea star Asterias rubens, the brittle star Ophiopholis aculeata, the sea urchin Strongylocentrotus droebachiensis, and the sea cucumber Cucumaria frondosa, which are among the most abundant echinoderms in the North Atlantic and Arctic Oceans. The latter two species are also commercially exploited. A series of 96-h acute exposures of the water-accommodating fraction (WAF) of used lubricating oil (ULO) were performed in different seasons (i.e. distinct reproductive stages). Digestive and reproductive tissues were analyzed for baseline and response levels of glutathione peroxidase (GPx) and ethoxyresorufin-O-deethylase (EROD). GPx activity was detected in the pyloric caecum, stomach, and gonad of sea stars, the intestine and gonad of sea cucumbers, and the gonad of brittle stars and sea urchins. No seasonal variation in baseline GPx activity occurred. Upon exposure to the ULO WAF, sex-based differences were elicited in the GPx activity of sea star stomachs (lower in females than males). EROD activity was present in the pyloric caeca of sea stars, and the gonads of brittle stars and sea urchins. An interaction between season and sex on baseline EROD activity was measured in the gonads of sea urchins. Ovaries exhibited significant seasonal variation in EROD activity and had greater activity than testes during the spawning and post-spawning seasons. Seasonal variation in EROD activity also occurred in sea star pyloric caeca and brittle star gonads. Furthermore, testes of sea urchins exposed to the ULO WAF exhibited suppressed EROD activity compared to baseline levels. The nearly universal presence of GPx activity highlights its potential as a useful biomarker, while EROD activity was much more limited. Findings suggest a complex relationship between temporal and biotic factors on both the baseline and response levels of enzymatic activity, emphasizing the need to consider sex and sampling season in studies of biomarkers of hydrocarbon exposure in boreal indicator species that display annual reproductive cycles.

Apart from sharing common ancestry with chordates, sea cucumbers exhibit a unique morphology and exceptional regenerative capacity. Here we present the complete genome sequence of an economically important sea cucumber, A. japonicus, generated using Illumina and PacBio platforms, to achieve an assembly of approximately 805 Mb (contig N50 of 190 Kb and scaffold N50 of 486 Kb), with 30,350 protein-coding genes and high continuity. We used this resource to explore key genetic mechanisms behind the unique biological characters of sea cucumbers. Phylogenetic and comparative genomic analyses revealed the presence of marker genes associated with notochord and gill slits, suggesting that these chordate features were present in ancestral echinoderms. The unique shape and weak mineralization of the sea cucumber adult body were also preliminarily explained by the contraction of biomineralization genes. Genome, transcriptome, and proteome analyses of organ regrowth after induced evisceration provided insight into the molecular underpinnings of visceral regeneration, including a specific tandem-duplicated prostatic secretory protein of 94 amino acids (PSP94)-like gene family and a significantly expanded fibrinogen-related protein (FREP) gene family. This high-quality genome resource will provide a useful framework for future research into biological processes and evolution in deuterostomes, including remarkable regenerative abilities that could have medical applications. Moreover, the multiomics data will be of prime value for commercial sea cucumber breeding programs., Author summary Echinoderms, ubiquitous in the marine environment, are important from evolutionary, ecological, and socioeconomic perspectives. Together with chordates and hemichordates, they form the deuterostome clade, making them a crucial node in the study of chordate ancestry. Within echinoderms, class Holothuroidea is unique; its members (the sea cucumbers) display remarkable regenerative abilities and play key roles as sediment bioturbators and symbiotic hosts, and many are prized in the seafood and pharmaceutical industries. The sea cucumber genome therefore has the potential to significantly contribute to our understanding of important evolutionary and biological processes and help enhance aquaculture programs. Here we present a high-quality genome sequence for the economically important species Apostichopus japonicus. Through comparative analyses, we identified 763 echinoderm-specific gene families enriched in genes encoding membrane proteins, ion channels, and signal transduction proteins. Marker genes associated with the notochord and gill slits were also found, providing valuable insight into the origin of chordates. The reduced number and low expression levels of biomineralization genes reflect the skeletal degeneration seen in sea cucumbers. Importantly, 2 gene families appeared to be expanded in A. japonicus and may play crucial roles in its heightened regenerative potential. Together, findings from the sea cucumber genome provide important and novel insights into echinoderm and deuterostome biology.

Understanding the trophic ecology of deep-sea communities provides valuable insight into deep-water ecosystem functioning, and can help inform fisheries management and conservation initiatives. However, few deep-sea food webs have been studied so far in the Northwest Atlantic. Here, stable isotope, gut content, and morphometric analyses were combined to explore trophic relationships in a deep-water fish assemblage off eastern Canada. While a weak depth effect was found on the isotopic composition of the species analyzed, isotopic and dietary records revealed the existence of two main, strongly coupled trophic pathways. The pelagic pathway either comprised pelagic fishes (e.g., meso- and bathypelagic species), primarily feeding on zooplankton and fish, or benthopelagic predators that showed a more pelagic-oriented diet. Such fishes displayed the lowest values of stable N and C isotope ratios. In contrast, demersal fishes representing the benthic trophic pathway had significantly higher values of δ15N and δ13C, and a taxonomically more benthic-oriented and diverse diet. Furthermore, smaller body sizes, larger mouths, and adaptations (e.g., bioluminescent structures and lures) prevailed in the pelagic species, consistent with living in a relatively food-poor environment. The largest average body sizes were found in the demersal fishes suggesting enhanced food intake and growth investment for the species. Only juvenile individuals of threatened species, such as Coryphaenoides rupestris and Rajella fyllae were caught, providing evidence of the vulnerability of such species to commercial fishing.

Halipteris finmarchica is one of the most common species of deep-sea pennatulacean corals in the Northwest Atlantic; it was recently determined to act as a biogenic substrate for other species and as a nursery for fish larvae. Its reproductive cycle was investigated in colonies sampled in 2006 and 2007 along the continental slope of Newfoundland and Labrador (Canada). Halipteris finmarchica exhibits large oocytes (maximum diameter of 1000 lm), which are consistent with lecithotrophic larval development. Female potential fecundity based on mature oocytes just before spawning was ~6 oocytes polyp 1 (500– 6300 oocytes colony 1 ); male potential fecundity was 16 spermatocysts polyp 1 (5500–57,400 spermatocysts colony 1 ). Based on statistical analysis of size-probability frequency distributions, males harboured one cohort of spermatocysts that matured inside 8–11 months, whereas females harboured two distinct cohorts of oocytes; a persistent pool of small ones (≤400 lm) and a small number (~20%) of larger ones that grew from ~400 to >800 lm over a year. Despite this difference in the tempo of oogenesis and spermatogenesis, a synchronic annual spawning was detected. A latitudinal shift in the spawning period occurred from south (April in the Laurentian Channel) to north (May in Grand Banks and July–August in Labrador/Lower Arctic), following the development of the phytoplankton bloom (i.e. sinking of phytodetritus). Prolonged oogenesis with the simultaneous presence of different oocyte classes in a given polyp is likely not uncommon in deep-sea octocorals and could hamper the detection of annual/seasonal reproduction when sample sizes are low and/or time series discontinued or brief.

Shallow-water annelids of the genus Ophryotrocha have become a popular biological system for exploring ecological, behavioral, developmental, and toxicological questions. Here we report on the successful maintenance in holding tanks, complete life cycle, and reproductive phenology of a first deep-water representative that could be used as a model species. This Ophryotrocha , which has yet to be formally described, is large (12–16 mm long) and exhibits simultaneous hermaphroditism. Specimens collected off northeast Newfoundland (eastern Canada) between 500 and 1500 m depth were monitored under flow-through laboratory conditions for over three years. They consistently exhibited seasonal feeding from April to February, followed by a reproductive season between February and May. Gametogenesis was initiated in early January and completed in early to mid-February, followed by courtship, which mainly involved pairs of individuals attached head to tail for hours to days. Transparent gelatinous masses containing 80–110 eggs were laid from mid-February to late-March. Propagules developed in the mass to the 1-chaetiger stage and, at an ambient temperature of ~1–4 °C, offspring emerged 30–45 days post-laying. Only ~40–45% of the eggs laid developed to the 1-chaetiger stage, with evidence of adelphophagy. After emerging from the gelatinous mass, 1-chaetiger stages remained aggregated and were guarded by adults for a few days before dispersing. All parents died following the dispersal of their offspring. The new generation reached sexual maturity in 8–9 months and was ready to reproduce the following January–February. A few cases of segmenting adult worms were also observed. Three complete generations developed successively to sexual maturity over the course of this study.

There is increasing evidence that spatial factors modulate reproductive processes over large (>150 km) and medium (10–100 km) scales in marine taxa, but few studies have explicitly determined the degree of inter-individual synchrony in gamete development at smaller scales within benthic populations. Using a ubiquitous broadcast-spawning species, the brittlestar Ophiopholis aculeata, we assessed variations in gametogenic activity over the annual reproductive cycle at various scales. Quantitative indices of oogenic maturity were compared in females collected: (1) in two substrata at a given site (distant ∼200–300 m), (2) among clusters of individuals living in relatively close proximity (∼10–50 m), and (3) within each cluster of individuals collected under/inside a given substratum (∼2–20 cm). Gametogenic maturity was also examined in females collected from distant sites (∼50–150 km). At the main study site, oogenic cohesion was greater within and among clusters of a given substratum than between substrata, and differences in reproductive output and spawning periods occurred between individuals from the two substrata studied. At the finest scale (within clusters of individuals) oogenic synchrony was maximal just before spawning. Comparing samples from distant geographic locations (>50 km) showed significant asynchrony outside the pre-spawning period. The present study shows that relatively high levels of asynchrony in gamete maturation may exist among conspecifics of a seemingly homogeneous population, except at the closest scale (within clusters) at the culmination of the reproductive cycle (near spawning). This emphasizes the likely interplay of inter-individual exchanges and small-scale distribution on the fine coordination of reproductive events.

Orange-footed Sea Cucumber (Cucumaria frondosa; Echinodermata: Holothuroidea) is a dark-brown species that is broadly distributed in North Atlantic and Arctic waters. Here, we document the rare occurrence of colour morphs showing various degrees of albinism, from totally white to faint orange pigmentation. These unusually coloured individuals were found across a broad distribution range in eastern Canada and northeastern United States, with their occurrence in Newfoundland samples ranging from 0.2% to 0.5%. Two fully albino individuals were noticeably smaller than other colour morphs. The occurrence of rare, unusually coloured sea cucumbers is important from an ecological standpoint and may also have commercial implications.

While age is fundamental in animal biology, forming the basis of critical concepts such as life-history strategies, longevity and population structures, measuring this variable in some taxa remains problematic. Such is the case of holothuroid echinoderms, which play key roles in marine benthic communities from the shore to the abyss, and which are extensively fished in many regions across the globe. Here, we present and validate a promising ageing technique using the cold-water species Psolus fabricii . The method involves the extraction of the oldest dermal plates (largest dorsal ossicles) to preserve their original pigments and structure. While plates initially appear to have a uniform texture, polishing and dying them reveals layered ring patterns. A study of laboratory-reared juveniles, from settlement to 40 months of age, confirmed that one layer is added annually, making plates both larger and thicker, and generating successive light and dark rings, the latter representing the transition (overlap) between two layers. Therefore, each pair of rings represents an annual growth band. Size-at-age data obtained using this method revealed that growth of P. fabricii is slow and that wild individuals collected at diving depths had reached an age of several decades.

When modeling life-history evolution of marine benthic invertebrates, it has been common to assume constant mortality rate of offspring during the pre-settlement phase and greater propagule vulnerability in the pelagic than in the benthic habitat. However, recent findings have challenged these assumptions, emphasizing the need for further empirical tests. Here we present the results of a multifactorial experimental investigation of predation rates on propagules of various taxa by benthic invertebrates. Planktotrophic and lecithotrophic propagules of echinoderms, cnidarians and annelids (i.e. sea cucumbers, sea stars, sea urchins, corals, sea anemones, jellyfishes, and polychaetes) were tested at various stages of development to examine the effects of ontogeny, size and behavior on predation rates by common filter feeders (mussels, tunicates) and suspension feeders (sea anemones). Overall, propagule survival was positively correlated with their size, although on closer inspection this was essentially due to the size difference between developmental modes (larger lecithotrophic propagules being less vulnerable). A slight inverse relationship between survival and age was detected in both lecithotrophic and planktotrophic propagules; however ingestion rates were not systematically higher on more advanced life stages within prey species due to predator-specific responses to ontogenetic changes. Filter feeders were generally more effective predators than suspension feeders. Tunicates expressed greater selectivity based on size and age of propagules than on their behavior, while the inverse occurred in the two other predators. A combination of factors, i.e. size, buoyancy and chemical defenses, presumably underlie overall higher survival rates in lecithotrophic than in planktotrophic propagules, supporting the hypothesis that the former but not the latter may have evolved due to increased epibenthic predation.

While conditions in shallow-water and deep-sea environments differ markedly, it remains unclear how eurybathic species adapt their life histories to cope with these changes. The present study compared indicators of maternal reproductive investment of three common echinoderms collected shallower than 20 m and deeper than 850 m: Cucumaria frondosa (Holothuroidea), Solaster endeca and Henricia sanguinolenta (Asteroidea). Depth-specific and species-specific differences were found in gonad indices (GI), potential fecundity, oocyte size frequency, as well as lipid classes and fatty acids measured in gonad tissue and oocytes. The asteroids, S. endeca and H. sanguinolenta , exemplified the interspecific trade-off between size and number of oocytes: the former had fewer larger oocytes than the latter, with higher total lipid proportions in them. However, intraspecifically, larger oocytes found in deep specimens of S. endeca did not translate into lower fecundity but rather into a seemingly higher GI, indicating greater investment per oocyte without reducing fecundity. Oocytes were absent in specimens of C. frondosa sampled in deep water, suggesting delayed or impaired maturation at the limit of their depth tolerance. Analysis of S. endeca sterol proportions in gonads and oocytes across depths showed higher sterol input into oocytes in females from the deep. Gonads of S. endeca and H. sanguinolenta contained similar essential fatty acids, but showed significant differences in major fatty acids and some of the less dominant ones, indicating diet specificities. Analyses within S. endeca showed evidence of similar feeding mode (carnivory) at both depths, but suggested shifts in the diet or synthesis of fatty acids, presumably reflecting differences in available food sources and/or adaptations to their respective environments.

Penilpidia desbarresi sp. nov. was collected in the Desbarres Canyon at a depth of 525 m, off the southeastern coast of insular Newfoundland, eastern Canada. The new species differs from the type species Penilpidia ludwigi (von Marenzeller, 1983) in having larger middle spines on arched rod-type ossicles on the dorsum and by having the lobe around the posterior body end formed by six pairs of very small tube feet. Penilpidia desbarresi sp. nov was photographed in situ and sampled on a single occasion in July 2007. This gonochoric species (1� 2 cm long) was found on a muddy substrate and individuals were aggregated, reaching a density of 50 ind. m � 2 . Preliminary evidence points to brooding, which would be a first for the family Elpidiidae. Penilpidia ludwigi, not recorded for more than 100 years after its first description, is re-described.

As a consequence of the decline of numerous commercial fish populations, an ecosystem-based approach to fisheries management, which includes the protection of essential fish habitat (EFH), has emerged. Cold-water coral (CWC) sites are recognized as biodiversity hotspots, but numerous examples of CWC destruction and degradation as a result of anthropogenic activities are well documented. However, although functional connections between CWCs and fish stocks are suspected, based on correlative evidence, proof of any close or direct relationship identifying CWCs as EFH is still lacking. Here, we provide evidence of the utilization of CWCs by fish larvae, mainly those of redfish (Sebastes spp). In multiyear surveys, fish larvae were consistently found closely associated with five species of sea pen (Octocorallia: Pennatulacea) in April and May. Prevalence and/or yields of fish larvae varied with coral host species, depth, location, and colony size. Evidence of the role of CWCs in the early life history of some...

This study developed an objective quantitative method for detecting small-scale temporal or spatial differences in gametogenesis in echinoderms. The method was applied to conventional monthly samples of the planktotrophic brittle star, Ophiopholis aculeata, collected at a single site in Newfoundland (eastern Canada) at 10–15 m depth. The samples were analysed to determine gonad index, oocyte size and gonadal stage using histology. The maturity stage index (MSI) was developed to integrate a measure of brittle star size (disc diameter), oocyte size and oocyte density. The MSIs ranged from 0 to 800 and had significantly different means among the four gametogenic stages (early growth, growth, mature and spent). The MSI was more sensitive in revealing significant differences between consecutive stages than any of its individual constituents. The MSI was also applied to gametogenic data from the lecithotrophic holothuroid, Mesothuria lactea, again revealing significant differences between successive oogenic stages. This method is expected to be useful in field and experimental studies of gametogenesis in echinoderms (and possibly other taxa), where it is important to detect not just the timing of annual peaks in reproduction but small differences in reproductive status among individuals or populations (e.g. from different habitats or feeding regimes).