Search

Holothuria scabra is one of the most intensively studied holothuroids, or sea cucumbers (Echinodermata: Holothuroidea), having been discussed in the literature since the early 19th century. The species is important for several reasons: (1) it is widely distributed and historically abundant in several shallow soft-bottom habitats throughout the Indo-Pacific, (2) it has a high commercial value on the Asian markets, where it is mainly sold as a dried product (beche-de-mer) and (3) it is the only tropical holothuroid species that can currently be mass-produced in hatcheries. Over 20 years have elapsed since the last comprehensive review on H. scabra published in 2001. Research on H. scabra has continued to accumulate, fuelled by intense commercial exploitation, and further declines in wild stocks over the entire distribution range. This review compiles data from over 950 publications pertaining to the biology, ecology, physiology, biochemical composition, aquaculture, fishery, processing and trade of H. scabra, presenting the most complete synthesis to date, including scientific papers and material published by local institutions and/or in foreign languages. The main goal of this project was to summarize and critically discuss the abundant literature on this species, making it more readily accessible to all stakeholders aiming to conduct fundamental and applied research on H. scabra, or wishing to develop aquaculture, stock enhancement and management programs across its geographic range.

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...

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.

Biochemical markers developed initially for food-web studies of terrestrial and shallow-water environments have only recently been applied to deep-sea ecosystems (i.e., in the early 2000s). For the first time since their implementation, this review took a close look at the existing literature in the field of deep-sea trophic ecology to synthesize current knowledge. Furthermore, it provided an opportunity for a preliminary analysis of global geographic (i.e., latitudinal, along a depth gradient) trends in the isotopic (δ15N, δ13C) and fatty acid composition of deep-sea macro- and megafauna from heterotrophic systems. Results revealed significant relationships along the latitudinal and bathymetric gradients. Deep-sea animals sampled at temperate and polar latitudes displayed lower isotopic ratios and greater proportions of essential ω3 long-chain polyunsaturated fatty acids (LC-PUFAs) than did tropical counterparts. Furthermore, δ15N and δ13C ratios as well as proportions of arachidonic acid increased with increasing depth. Since similar latitudinal trends in the isotopic and fatty acid composition were found in surface water phytoplankton and particulate organic matter, these results highlight the link across latitudes between surface primary production and deep-water communities. Because global climate change may affect quantity and quality (e.g., levels of essential ω3 PUFAs) of surface primary productivity, and by extension those of its downward flux, the dietary intake of deep-sea organisms may likely be altered. In addition, because essential ω3 PUFAs play a major role in the response to temperature variations, climate change may interfere with the ability of deep-sea species to cope with potential temperature shifts. Importantly, methodological disparities were highlighted that prevented in-depth analyses, indicating that further studies should be conducted using standardized methods in order to generate more reliable global predictions.

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.

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.

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.

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.

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.

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.

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.

Spatial and temporal shifts in biometric features were examined in three common deep-water pennatulacean corals (sea pens) from the Northwest Atlantic: Anthoptilum grandiflorum, Halipteris finmarchica and Pennatula aculeata. These three species show different morphological characters and adaptations to their environment. Analyses of colony length, ratio of peduncle to colony length, weight/length ratio, polyp size and density as well as sclerite shape, location and abundance indicate that their phenotype is modulated by environmental factors (e.g. food availability, currents and sediment type) and antipredator strategies. Moreover, the three species had different carbon and nitrogen stable isotope signatures that could be explain primarily by their different polyp diameters and colony shapes, suggesting that they rely on slightly different food sources (varying proportions of phytodetritus and zooplankton). Finally, sclerites were found only in H. finmarchica and P. aculeata and are not known to occur in A. grandiflorum, except for minute oval bodies inside the peduncle. The Mg/Ca ratio of sclerites differed between the two species and, for P. aculeata, among types of sclerites, evoking different biomineralization pathways related to their functional roles (structural support or defence). Overall, this study provides new information on the ecology of poorly known species, which are ubiquitous and suspected to play an important ecological role in deep-water ecosystems.

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.

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.

Although continental shelf and slope environments typically exhibit high epifaunal biomass and have been subjected to increasing fishing pressure, ecological information on assemblages of non-commercial invertebrate species from subtidal and bathyal areas remains limited. Sea stars (Echinodermata: Asteroidea), which are known to influence communities through their feeding habits, have received less attention than structural taxa such as corals and sponges. To better understand the ecological roles of asteroids on continental shelves, we investigated ~30 species and assessed their distributions and co-occurrence with other benthic invertebrates on the shelf and slope of Eastern Canada. Using fisheries data and in situ video footage, we compiled a large dataset covering ~600,000 km2 that included over 350,000 individual asteroid records (37–2243 m depth). Multivariate analyses revealed geographically distinct asteroid assemblages, with a maximal overall density at 400–500 m and the highest diversity at 500–700 m. The most abundant and densely occurring species was Ctenodiscus crispatus. We found that asteroids associate with corals, sponges, bivalves, and other echinoderms, and that depth and substrate influence these assemblages. We identified species likely to affect coexisting organisms by their burrowing behavior that can disrupt epi- and infauna (C. crispatus) and through predation on ecologically important corals (Hippasteria phrygiana). In addition to providing baseline distribution and ecological information for many bathyal asteroid species in the Northwest Atlantic, this work highlights the abundance and diversified roles of asteroids within continental shelf and slope ecosystems.

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.

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.

Asteroids (sea stars) can be important predators in benthic communities and are often present in ecologically important and vulnerable deep-sea coral and sponge habitats. However, explicit studies on the trophic ecology of deep-sea asteroids are rare. We investigated the diets of seven species of deep-sea asteroid from the bathyal zone of Newfoundland and Labrador, eastern Canada. A multifaceted approach including live animal observations, stomach content analysis, and stable isotope analysis revealed the asteroids to be either top predators of megafauna or secondary consumers (mud ingesters, infaunal predators, and suspension feeders). The stable isotope signatures of Ceramaster granularis, Hippasteria phrygiana, and Mediaster bairdi are characteristic of high-level predators, having δ15N values 4.4‰ (more than one trophic level) above Ctenodiscus crispatus, Leptychaster arcticus, Novodinia americana, and Zoroaster fulgens. We present strong evidence that corals and sponges are common food items for two of the predatory species, C. granularis and H. phrygiana. During laboratory feeding trials, live H. phrygiana fed on several species of soft coral and C. granularis fed on sponges. Stomach content analysis of wild-caught individuals revealed sclerites from sea pens (e.g. Pennatula sp.) in the stomachs of both asteroid species; H. phrygiana also contained sclerites from at least two other species of octocoral and siliceous sponge spicules were present in the stomachs of C. granularis. The stomach contents of the secondary consumers contained a range of invertebrate material. Leptychaster arcticus and Ctenodiscus crispatus feed infaunally on bulk sediment and molluscs, Zoroaster fulgens is a generalist infaunal predator, and the brisingid Novodinia americana is a specialist suspension feeder on benthopelagic crustaceans. This study provides a foundation for understanding the ecological roles of bathyal asteroids, and suggests that some species may have the potential to be important modulators of deep-sea benthic communities.

The deep-sea pennatulacean coral Anthoptilum grandiflorum exhibits a cosmopolitan distribution and was recently determined to serve as habitat for other invertebrates and fish larvae in the northwest Atlantic. Colonies collected at bathyal depths between 2006 and 2010 in eastern Canada were analysed to determine their fecundity and characterize spatial and temporal trends in their reproductive cycle. Anthoptilum grandiflorum is a gonochoric broadcast spawner with a sex ratio that does not differ significantly from equality (although one hermaphrodite colony was observed). In male colonies, all the spermatocysts synthesized become mature over the annual cycle, while only ~21 % of the initial production of oocytes reaches maturity in female colonies. Female potential fecundity based on mature oocytes just before spawning was on average 13 oocytes polyp−1; male potential fecundity was 48 spermatocysts polyp−1. The spawning period of A. grandiflorum differs between geographic regions, from April (in southern Newfoundland) to July (in Labrador), closely following regional spring phytoplankton blooms after accounting for the deposition of planktic detritus. Release of oocytes by a live colony held in the laboratory was recorded in April 2011, coincident with field data for similar latitudes. Seawater temperatures at the time of spawning were around 3.6–4.8 °C in all regions and in the laboratory. Early stages of gametogenesis were detected in colonies collected shortly after the spawning season, and early and late growth stages occurred successively until December. Mature colonies were observed between April and July (depending on latitude). The diameter of mature oocytes (~1,100 μm maximum diameter) is consistent with lecithotrophic larval development.

Animals display diverse means of producing and provisioning offspring, from eggs to embryos and juveniles. While external development predominates, many forms of embryonic incubation have evolved, including placentation in mammals and a number of understudied variants in basal metazoans that could help understand evolutionary diversification. Here we studied the brooding sea anemone Aulactinia stella, using behavioural, morphological and biochemical indicators of offspring phenotype to characterize gestation and elucidate parental and sibling relationships. The pronounced variance in juvenile weight within broods was not strongly related to any of the typical external predictors (adult weight, clutch size, sampling date, environmental conditions). Lipid concentration was significantly higher in the tissues of the small juveniles than in those of large juveniles or adult, and fatty acid profiles tended to set small juveniles apart. Finally, intra-brood feeding on external resources was documented in larger juveniles. These results are consistent with ontogenetic shifts in nutrition, from vitellogenic provisioning to post-zygotic nourishment to a prenatal form of nursing upon acquisition of feeding organs, highlighting matrotrophic and conflict-driven mechanisms acting on offspring phenotype during gestation.

Aim As the main or sole motile stage of many aquatic taxa, propagules play a central role in their population dynamics, macroevolution and biogeography. The premises of studies concerned with dispersal, on issues as diverse as marine protected areas, sustainable fisheries and invasive species, commonly make simplified assumptions linking larval development mode (planktotrophic, lecithotrophic) and pelagic propagule duration (PPD) or pelagic larval duration. Because general empirical tests of these connections have yielded equivocal results, we critically examined the relationship between larval mode and PPD in light of regional and taxon-specific criteria. Location Oceans world-wide. Methods We collated data from 190 species from the phylum Echinodermata and used two-way and one-way ANOVA to compare PPD among larval modes, taxonomic classes, geographic regions and climate zones. We also assessed the contribution of egg size, temperature and other continuous predictors using multiple regressions and ANCOVA, and examined whether geographic range size differed among larval modes. Results Our results depart from the common assumption that planktotrophs have longer PPDs than lecithotrophs. Instead, we detected a synergistic influence of phylogeny and climate. No significant difference in PPD between planktotrophs and lecithotrophs occurred in two of the four classes and only four out of nine major ocean basins contained species with significantly different PPDs on the basis of larval mode. Species from colder climates displayed relatively constant PPDs regardless of larval mode, whereas temperate and warm-water species displayed a clearer dichotomy. PPD did not correlate with geographic range size nor did planktotrophs and lecithotrophs exhibit significantly different range sizes. Main conclusions Our findings indicate that larval mode is not a reliable predictor of PPD across broad geographic and taxonomic scales. Instead developmental strategies may instigate shorter or longer PPDs in schemes that are influenced by evolutionary and environmental pressures.

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).

Although the reproductive biology and early life-history stages of deep-sea corals are poorly understood, such data are crucial for their conservation and management. Here, we describe the timing of larval release, planula behavior, metamorphosis, settlement, and early juvenile growth of two species of deep-sea soft corals from the northwest Atlantic. Live colonies of Gersemia fruticosa maintained under flow-through laboratory conditions released 79 planulae (1.5–2.5 mm long) between April and early June 2007. Peak planulation in G. fruticosa coincided with peaks in the chlorophyll concentration and deposition rates of planktic matter. Metamorphosis and settlement occurred 3–70 d post-release. The eight primary mesenteries typically appeared within 24 h, and primary polyps grew to a height of ∼6–10 mm and a stalk diameter of ∼1 mm within 2–3 months. Planulae of Duva florida (1.5–2.5 mm long) were extracted surgically from several colonies and were successfully reared in culture. Primary polyps reached a height of ∼3–4 mm within 2–3 months. No budding of primary polyps was observed in either species over 11–13 months of monitoring, suggesting a very slow growth rate.

This study examined the influence of temporal and spatial factors on the determination of reproductive cycles in selected deep-water echinoderms. The prevalence of inter-individual synchrony in the gametogenesis of three ubiquitous species, Phormosoma placenta (Echinoidea), Hippasteria phrygiana (Asteroidea) and Mesothuria lactea (Holothuroidea) collected off the coast of Newfoundland and Labrador (eastern Canada), was determined. Analyses revealed diverse degrees of gametogenic asynchrony at the scales examined (within trawls, between trawls over similar or different periods, as well as among depths and locations over the same period). Taken as a whole, samples did not show any annual or seasonal patterns, whereas some sets of samples, taken over a particular time period in the same area and at the same depth, revealed well synchronized maturing and/or spawning periods in P. placenta and H. phrygiana. This study presents evidence that determination of reproductive cycles in many deep-sea species may be affected by low sampling resolution inherent to most deep-sea studies. More accurate assessments of reproductive patterns and periodicities may require much tighter collection designs as several species are likely to rely on long-term or transient pairing and aggregation to synchronize their breeding activities.

The patterns of genetic diversity and connectivity were investigated in Cucumaria frondosa, the most abundant sea cucumber in the North Atlantic, to assist in the management and conservation of this ecologically important marine invertebrate, which is the target of an emerging fishery. Mitochondrial DNA COI sequences of 334 C. frondosa were obtained and analyzed, mainly from its western North Atlantic range, where the commercial fishery is being developed, with complementary sampling in the mid- and eastern North Atlantic. Analysis of molecular variance showed no significant (P > 0.05) differences among subpopulations in the western region suggesting that it constitutes one panmictic population. The same analysis showed low, but significant differences between eastern and western Atlantic populations. Coalescent analyses using isolation with migration models and a Bayesian skyline plot indicated historical divergence and a general increase in population size prior to the last glacial maximum and highly asymmetric gene flow (nearly 100 times lower from west to east) between sea cucumbers from North America and Norway. Results suggest that subpopulations of C. frondosa within the western North Atlantic have been highly connected. We propose that aided by the high-connectivity local subpopulations can recover rapidly from natural (i.e., ice ages) or anthropogenic (i.e., overfishing) population declines through recruitment from deep refugia.

While epibiotic associations between macrobenthic invertebrates are common, the role they play in the feeding ecology of intervening species is often incompletely understood. The diets of epibiotic sea anemones Allantactis parasitica and their gastropod hosts were analyzed using digestive tract contents, lipid biomarkers and observations of live specimens in an attempt to detect dietary feedback from the facultative association. Comparisons were made using symbiotic individuals and asymbiotic counterparts collected at depths of 191–627 m from three neighbouring areas in the northwest Atlantic. Gastropods carrying one or two epibionts had higher stomach indices than those harbouring three epibionts or no epibiont. The diet of symbiotic gastropods was also more diversified based on stomach contents and lipid analysis. Among other things, symbiotic gastropods contained four times more lipids and a greater proportion of Σn−3 fatty acids. Gastrovascular cavity content indices of asymbiotic sea anemones were generally lower than those of symbiotic counterparts. Their cavities were more often empty, and their diet less diversified with fewer benthic items, suggesting that foraging of gastropods through the sediments makes more food available to sea anemones living as epibionts. Lipid analysis showed some disparities between symbiotic and asymbiotic sea anemones at the regional scale, including in percent phospholipids and in the proportion of certain fatty acids. Together these findings indicate that mutual protection against predators leads to prolonged and more efficient foraging for gastropods and increased time spent deployed (feeding) in food-rich areas for sea anemones, thus enabling both partners to fully exploit food resources that may be limited at bathyal depths.

Increasing threats to deep-sea corals highlight the need to expand knowledge of these taxa so that conservation measures can be developed. The present study focused on the reproductive patterns of the deep-sea solitary coral Flabellum angulare. A series of samples (n = 398) collected in 2006–2008 in the northwest Atlantic at depths of 925–1,430 m revealed that gametogenesis was synchronous among males and females and fluctuated seasonally. Initiation of gamete synthesis was estimated to be in August–September and spawning in June. Further analysis and daily monitoring of 30–60 individuals maintained in a flow-through mesocosm showed that gamete release occurred in March–June with a peak in May. Release of oocytes coincided with rising seawater temperatures and high deposition rates indicative of elevated water column productivity. Oocytes (900–1,200 μm diameter) were released through the oral cavity, generally in bundles of 3–5 surrounded by mesenterial filaments and attached to a thread (30–50 mm long). As oocytes became free in the water column, ovulation occurred followed by fertilization. Eggs/embryos initially remained on the tentacles of the spawner before either falling onto the substratum or floating to the surface. The embryos developed into planula larvae measuring 2–3 mm in length within about 24 h. Together, these findings shed new light on the strategies used by deep-sea corals to maximize their reproductive success.

Adaptations and life history strategies have rarely been studied in deep-sea corals. Here we present laboratory data on the timing of larval release, reproductive output, substratum selectiv- ity and growth of 2 alcyonaceans (Cnidaria, Octocorallia) from the bathyal zone of eastern Canada. Planulation patterns in 2 Drifa species were significantly influenced by seasonal productivity and the lunar cycle, and larval output was greater in larger colonies (from shallower depths). After release, planulae of Drifa sp. shifted their buoyancy to move between the bottom and the water column, whereas planulae of D. glomerata were largely demersal and crawled on the substratum until settle- ment (typically occurring after 1 to 30 d in both species). Settlement trials showed that planulae set- tled more readily on rough natural surfaces covered with biofilm than all other substrata tested and that larvae of colonies from deeper habitats were less selective than those originating from shallower habitats. In both species, the 8 primary mesenteries (and tentacle buds) appeared within 24 h post settlement, and polyps reached a maximum size after 2 to 3 mo. The first branching polyp was observed after ca. 9 mo of growth in D. glomerata, whereas no direct evidence of branching was detected in Drifa sp. over 21 mo of observation, although 2- and 4-polyp colonies were later discov- ered in the holding tank with adults. Together, these findings highlight dual traits of resilience (i.e. extended breeding period, long-lived larvae) and vulnerability (i.e. substratum selectivity, slow growth) in deep-sea corals.

While breeding synchrony among conspecifics is increasingly well understood with regards to the reproductive success of vertebrate and invertebrate taxa, the occurrence of simultaneous multispecies breeding events remains intriguing. The fairly recent discovery of mass annual spawnings in reef corals has provided a first glimpse at putative strategies of reproductive isolation during such events. However, the mechanisms and advantages of same-day heterospecific breeding are still poorly understood and have not yet been investigated in non-coral taxa with different life history strategies. In an effort to bridge this gap, we investigated spawning periodicity and synchrony among 26 sympatric species of free-spawning, capsule-laying, and brood-protecting macroinvertebrates belonging to six different phyla. Twenty-four of these species released gametes or larvae between early March and late April. We analyzed the events over fine temporal scales to test the hypothesis that breeding activities were not random in time or relative to each other. We found that the two main reproductive pulses followed a lunar periodicity and that consistent species- and gender-specific modulations in the timing of spawning occurred during same-day episodes involving up to six free-spawning species. Mass spawning accounts from the literature were reviewed and compared. This work suggests that many species participate in synchronous heterospecific spawning events either because they respond to the same environmental cues or rely on cross-cueing and that reproductive isolation is favored by species-specific circadian patterns, spawning behaviors and cross-gender signaling.

The present study examined the mode and timing of reproduction of poorly understood deep-water octocorals and the environmental factors that may influence their reproductive patterns. Data on reproductive characteristics of the octocoral Drifa glomerata (Alcyonacea: Nephtheidae) collected between 2004 and 2007 at ca. 100–330 m depth off Newfoundland and Labrador (eastern Canada) were compared among years, months and depth ranges. No male gonad was ever observed during the study. The ratio of fertile colonies possessing large pinkish polyps with oocytes/planulae was >50% throughout the year. The number of brooded planula larvae within a single fertile polyp varied between 1 and 10 for a total of approximately 40–3,000 in a whole colony. The size of oocytes and/or planulae was consistently greater in the polyps than in the branchlets, indicating that the development pathway of oocytes to planulae is from the branchlets to the polyps. Although larval production seemed to persist year round, the onset of major planulation events occurred in December–January of two consecutive years, when large mature planulae were released in correlation with the first increase of photoperiod and maximum temperature at 150 m. A second peak in planulation between April and early June followed the phytoplankton bloom. Seasonal trends were more apparent in colonies from

Sea anemones Allantactis parasitica Danielssen, 1890 (Actiniaria: Hormathiidae) living as epibionts on various gastropods were found at depths of ~725–1100 m off Labrador (eastern Canada). Live specimens collected with their hosts were studied in the laboratory to elucidate the role of the gastropod host in the reproductive and colonizing success of its actinian symbiont. Broadcast spawning occurred twice a year, in spring and late fall, in correlation with maximum phytoplankton or phytodetritus abundance, often during copulation of the gastropod hosts. The fully developed planula stage was reached after ~22 d. Settlement on the host’s shell generally occurred 40–44 d postfertilization, although some larvae delayed settlement for up to 22 weeks in the absence of a host. Independent and pairwise settlement trials showed that shells of live bathyal gastropods were highly favoured compared with shells of shallow-water gastropods, empty shells, pebbles, or sand. Juveniles developed 24 tentacles and reached ~10 mm in basal disk diameter and ~12 mm in stalk height after 21 months of growth. The estimated growth rates of A. parasitica suggest that symbiotic individuals would require 6–7 years to reach the mean maximum adult size (~35 mm, basal disk diameter), whereas asymbiotic individuals would need 11–12 years.

Combining field and laboratory work, this study investigated the reproductive cycle, aggregative behavior, spawning periodicity, development and early growth of the sea star Henricia lisa living at bathyal depths off eastern Canada. Marked differences were found between individuals from ~1,300 and ~600 m deep. The former had a male biased sex ratio and an aperiodic reproductive cycle, whereas the latter displayed an equal sex ratio and a biannual breeding pattern. Furthermore, the maximum size was larger and female fecundity roughly five times higher in shallower compared to deeper populations. In the tanks, aggregative behavior was recorded twice a year during the summer and winter breeding periods. The onset of aggregations and spawning coincided with a temperature of 3–4°C. Males spawned first and females typically responded inside 30–60 min. Between 12 and 20 eggs were retained to be brooded under the arched arms of the female, whereas the remainder were broadcasted and developed without parental care. The fertilized eggs underwent a first cleavage after 12 h, reached the brachiolaria stage in 1 month, became juveniles within 3–4 months and reached ~ 4 mm in diameter after 14–17 months of growth. The embryos and juveniles developed at the same rate whether brooded or not, and development of winter cohorts was typically slower due to lower prevailing temperatures. This study of H. lisa provides the first evidence of lecithotrophy in a seasonally breeding deep-sea echinoderm and of brooding in a deep-sea asteroid.

The hormathiid sea anemone Allantactis parasitica was found living as an epibiont on numerous species of gastropods at depths of 725–1100 m along the continental slope of eastern Canada. The proportion of bathyal gastropods hosting 1–6 sea anemones reached 72.5% in a single trawl. Although A. parasitica was occasionally found on other substrata (i.e. empty shells, pebbles), laboratory trials confirmed that they preferably associate with living gastropods. Settlement of planula larvae occurred significantly more often on the shells of live bathyal gastropods than on all other substrata present in the tanks. Juvenile sea anemones (∼ 1 mm diameter) readily moved from the mud or other inert substrata onto shells of burrowed bathyal gastropods. Conversely, larvae, juveniles and adults of A. parasitica never associated with any shallow-water gastropods when given the opportunity. Trials exposing predatory sea stars (Leptasterias polaris) from shallow and bathyal depths to bathyal gastropods (Buccinum undatum) with epibiotic A. parasitica, and to asymbiotic bathyal and shallow-water B. undatum, revealed adaptive behaviours in both prey and predator. Shallow-water gastropods (devoid of epibionts) reacted defensively to L. polaris, whereas bathyal gastropods relied mostly on their epibionts to protect them, thus falling prey to L. polaris when the epibionts were removed. L. polaris from bathyal depths typically ignored symbiotic gastropods, but they consistently preyed on asymbiotic ones, while L. polaris from shallow areas initially attempted to prey on all gastropods, but learned to avoid those harbouring sea anemones. Furthermore, living as epibionts afforded sea anemones a means to escape one of their own predators, the sea star Crossaster papposus. The mutualistic relationship between hormathiid sea anemones and bathyal gastropods from the NW Atlantic may have evolved in response to predation pressure.

Egg masses, juveniles and adults of the gastropod Palio dubia were found in shallow rocky habitats of eastern Canada dominated by the bryozoan Eucratea loricata. Multiple-choice experiments and direct field observations revealed that P. dubia prefers to feed on E. loricata. Courtship, copulation and egg-laying as well as hatching of P. dubia were closely related to the lunar cycle. Reproduction was preceded by increased pairing and aggregative behaviour. The duration of embryonic development in the capsules was 10–15 d. After hatching, most veligers were retained within the bryozoan branches during their pelagic phase (1–3 d). In multiple-choice experiments, settlement occurred preferentially on the bryozoan E. loricata. In the absence of the preferred substratum, the larvae continued to swim and died after a period that never exceeded 8 d. Juveniles remained associated with the bryozoans on which they settled and reached the adult size in ~3 months.

Annual and monthly patterns of gamete release by the sea cucumber Isostichopus fuscus on the coast of Ecuador were studied to determine the proximal spawning cue and variations in reproductive output throughout the year. Several hundred newly collected individuals were monitored nearly every month for 4 yr. I. fuscus displayed a lunar spawning periodicity: 0.7 to 34.9% of individuals consistently spawned 1 to 4 d after the new moon. Spawning mostly occurred within one evening; however, some gamete release was often recorded over 2 to 4 consecutive evenings. Individuals maintained in captivity for several months retained their spawning periodicity and timing with the lunar cycle. Conversely, newly caught individuals that were shaded from the moonlight did not spawn, thus demonstrating the apparent lack of endogenous rhythms and prevalence of lunar luminance over other cues (i.e. tidal cycle, fluctuations in barometric pressure). On a spawning night, males typically initiated gamete release around sunset; females spawned just after the peak male broadcast. The percentage of spawning individuals was higher and a greater overlap between male and female peak spawning activity was observed during clear conditions compared with overcast conditions. The gonads of individuals that did not spawn in a given month showed a variety of maturity levels, including post-spawning, growth and mature gametogenic stages. Hence, the individual reproductive cycle is apparently longer than the monthly spawning periodicity observed at the population level, enabling I. fuscus populations to be reproductive year round.

Summary The sea cucumber Apostichopus japonicus is an economically important species along the northwest Pacific Coast, including China, Democratic People’s Republic of Korea, Republic of Korea, Russia, and Japan. In the present chapter, we summarize knowledge on the embryonic and larval development of A. japonicus, as well as the impacts of various environmental factors on these processes. A. japonicus is a dioecious broadcast spawner. Its life cycle can be divided into eight major stages: fertilization, blastula, gastrula, auricularia, doliolaria, pentactula, juvenile, and adult. The fertilized, mainly demersal eggs measure ∼165 μm in diameter, and develop into freely rotating blastulae in 14 h at 20–21 °C. The embryos then develop into auricularia larvae over the following 34 h, at which time they gain the ability to feed. When the auriculariae grow to their maximum size of ∼800–950 μm, they shrink and transform into doliolariae, and subsequently into pentactulae after completion of metamorphosis. The development of buccal and ambulacral podia indicates the onset of the juvenile stage. It takes almost two years for A. japonicus to reach sexual maturity, and the life span of this species is commonly estimated to be at least five years. The influence of environmental factors, such as temperature, salinity, and planktic food, on larval development and growth, as well as substrate selection during metamorphosis are discussed. Transitional functions of locomotory and feeding organs in larvae, behavioral characteristics during settlement, and interindividual variations in early growth rates are also examined.