Search

The polychaete Boccardia wellingtonensis is a poecilogonous species that produces different larval types. Females may lay Type I capsules, in which only planktotrophic larvae are present, or Type III capsules that contain planktotrophic and adelphophagic larvae as well as nurse eggs. While planktotrophic larvae do not feed during encapsulation, adelphophagic larvae develop by feeding on nurse eggs and on other larvae inside the capsules and hatch at the juvenile stage. Previous works have not found differences in the morphology between the two larval types; thus, the factors explaining contrasting feeding abilities in larvae of this species are still unknown. In this paper, we use a transcriptomic approach to study the cellular and genetic mechanisms underlying the different larval trophic modes of B. wellingtonensis. By using approximately 624 million high-quality reads, we assemble the de novo transcriptome with 133,314 contigs, coding 32,390 putative proteins. We identify 5221 genes that are up-regulated in larval stages compared to their expression in adult individuals. The genetic expression profile differed between larval trophic modes, with genes involved in lipid metabolism and chaetogenesis over expressed in planktotrophic larvae. In contrast, up-regulated genes in adelphophagic larvae were associated with DNA replication and mRNA synthesis.

The distribution range expansion of species mediated by natural or anthropic mechanisms is one of the main causes of changes in biodiversity patterns. Anemonia alicemartinae is a cryptogenic species found along the coasts of the Southeast Pacific Ocean. This species has expanded its range by >1900 km along the Chilean coast throughout the last 50 yr. A. alicemartinae cohabits with the native anemone Phymactis papillosa in the low intertidal zone, and given the limited mobility of both species, limited space could encourage aggressive behavior between them. P. papillosa shows different color phenotypes, and, as in other anemone species, color is associated with its level of aggressiveness. Here, we evaluated the aggressive behavior of A. alicemartinae on 2 color morphotypes of P. papillosa. Also, intraspecific agonistic interactions were considered in individuals of A. alicemartinae from 2 localities. Four experiments were conducted: (1) individual vs. individual, (2) individual vs. group forming a frontal line, (3) individual vs. group surrounding the individual and (4) group vs. group. Results showed A. alicemartinae to be a weak competitor against P. papillosa. The cryptogenic species lost more contests with green P. papillosa than with the red phenotype. Few aggressive interactions between conspecifics of A. alicemartinae were found. Results suggest that the expansion success of A. alicemartinae could be explained by alternative strategies, such as escape behavior, asexual reproduction and high dispersal potential.

Earthquake/tsunamis can have profound impacts on species and their genetic patterns. It is expected that the magnitude of this impact might depend on the species and the time since the disturbance occurs, nevertheless these assumptions remain mostly unexplored. Here we studied the genetic responses of the crustacean species Emerita analoga, Excirolana hirsuticauda, and Orchestoidea tuberculata to the 27F mega-earthquake/tsunami that occurred in Chile in February 2010. mtDNA sequence analyses revealed a lower haplotype diversity for E. analoga and E. hirsuticauda in impacted areas one month after the 27F, and the opposite for O. tuberculata. Three years after the 27F we observed a recovery in the genetic diversity of E. analoga and E. hirsuticauda and decrease in the genetic diversity in O. tuberculata in 2/3 of sampled areas. Emerita analoga displayed decrease of genetic differentiation and increase in gene flow explained by long-range population expansion. The other two species revealed slight increase in the number of genetic groups, little change in gene flow and no signal of population expansion associated to adult survival, rapid colonization, and capacity to burrow in the sand. Our results reveal that species response to a same disturbance event could be extremely diverse and depending on life-history traits and the magnitude of the effect.

Molluscan veliger larvae and some annelid larvae capture particulate food between a preoral prototrochal band of long cilia that create a current for both swimming and feeding and a postoral metatrochal band of shorter cilia that beat toward the prototroch. Larvae encountering satiating or noxious particles must somehow swim without capturing particles or else reject large numbers of captured particles. Because high rates of particle capture are inferred to depend on the beat of both ciliary bands, arrest of the metatroch could be one way to swim while reducing captures. Larvae in eight families of annelids arrest metatrochal cilia frequently during prototrochal beat, often over a large part of the metatrochal band and with the arrested cilia aligned near the beginning of the effective stroke. In contrast, metatrochs of veligers of gastropods and bivalves rarely arrested while the prototroch beat, and those arrests were more localized and variable in position. This difference in metatrochal arrest was unexpected under hypotheses of either a single origin of this feeding mechanism or multiple origins within each phylum. Although different in metatrochal arrests, larvae of both phyla can separate swimming from feeding while both prototroch and metatroch beat. One hypothesis explaining low rates of capture per encounter, without metatrochal arrest, is a change in adhesion of prototrochal cilia with algae. In a few observations, part of the velar edge was retained within the veliger's shell so that exposed prototrochal cilia contributed to swimming while the adjacent metatroch and food groove were sequestered.

Poecilogony is a type of reproduction in which a species produces different types of larvae. Boccardia wellingtonensis, is a poecilogonous polychaete with females producing planktotrophic and adelphophagic larvae, in addition to nurse eggs, in the same capsule that differ in feeding behavior. It is still unclear why planktotrophs do not feed on nurse eggs during the intracapsular development and arrest its growth, while adelphophagic larvae consume nurse eggs and planktotrophic larvae inside the capsule, hatching as advance larvae or as juveniles. Here we characterized the expression of selected miRNAs from these two types of larvae and from adults in order to begin to understand the molecular mechanisms that regulate expression in this type of poecilogony. Results showed that adults and pre-hatching adelphophagic larvae have high levels of expression of miR-125, miR-87a and let-7, while adelphophages at early developmental stage had low levels of expression of miR-87b. Planktotrophic larvae showed low expression level of let-7. This work represents the first step in understanding the role of miRNAs in the development of different larval types in a poecilogonous species. We also propose to B. wellingtonensis as an interesting biological model to study the evolution of larval modes and reproductive strategies of marine invertebrates.

In marine invertebrates, the modes of development at early stages are related to the type and capacity of larval feeding to achieve growth. Therefore, studying the factors that determine larval feeding strategies can help to understand the diversity of life histories and evolution of marine invertebrates. The polychaete Boccardia wellingtonensis is a poecilogonous species that encapsulates and incubates its offspring. This species produces two types of larvae: (1) larvae that do not feed within the capsule and hatch as planktotrophic larvae (indirect development), and (2) adelphophagic larvae that feed on nurse eggs and other larvae inside the capsule to hatch as advanced larvae or juveniles (direct development). Otherwise, the larval types are indistinguishable at the same stage of development. The non-apparent morphological differences between both types of larvae suggest that other factors are influencing their feeding behavior. This work studied the potential role of the activity of 19 digestive enzymes on the different feeding capacities of planktotrophic and adelphophagic larvae of B. wellingtonensis. Also, differences in larval feeding structures and the larval capacity to feed from intracapsular fluid were evaluated by electron and fluorescence microscopy. Results showed that both types of larvae present similar feeding structures and had the capacity to ingest intracapsular fluid protein. Adelphophagic larvae showed overall the highest activities of digestive enzymes. Significant differences between larval types were observed in nine enzymes related to the use of internal and external nutritional sources. Given that larval feeding is closely related to larval development in species with encapsulation, this work supports that the study of the digestive enzymatic machinery of larvae may contribute to understanding the evolution of developmental modes.

Many Caribbean nations lack information on the ecology and biology of marine species, which are essential for food security and livelihoods in the region. This study aimed to advance the knowledge of two commercially important fish species, lane snapper (Lutjanus synagris) and white grunt (Haemulon plumierii), using cost-efficient techniques. Specifically, geometric morphometrics was used to assess the presence of ecomorphological groups (characterized by body shape variation associated with local environmental variables) in the Honduran Caribbean continental platform. Photographs of 104 lane snapper and 99 white grunt adult individuals were taken and digitalized with 12 landmarks. Subsequently body shape patterns were related to environmental variables using Distance-based linear models and Partial Least Squares. Results enabled the identification of ecomorphological groups or fish stocks in the study region associated with the environmental conditions of each site. Distance to river mouth and Chlorophyll a, both indicators of land-based stressors, appeared as the primary driving force of body shape differentiation in the species. These results are key for the development of informed reef fisheries management policies in the Caribbean region.

Homing behaviour is frequently observed in marine intertidal invertebrate species. This behaviour may help species to deal with the environmental variability of the intertidal, providing shelter during low tides and areas to explore and search for food during high tides. The capacity of individuals to show fidelity behaviour should be an adaptive trait, due to the uncertainty that finding a new shelter in each tidal cycle implies. Chiton granosus is a common polyplacophora of the Southeastern Pacific rocky intertidal zone. During high tides, individuals move throughout the substratum in search of food; meanwhile, they are found within crevices in groups of variable sizes during low tides. According to previous works, this species shows some degree of fidelity to these shelters. Using field and laboratory experiments, we herein evaluate the factors determining the degree of site fidelity in C. granosus, taking into account the distance travelled from the shelter and food availability. Also, we evaluated the importance that chemical signs from the pedal mucus have in aiding C. granosus to return to its refuge. Field observations showed that C. granosus presents variable levels of site fidelity covering a maximum distance of 50 cm from its shelter. Laboratory results suggested that fidelity to shelters is related to the proximity of food sources. Chemical cues from the pedal mucus could be used to find the shelter after exploratory activities during high tides.

Due to climate change, numerous ice bodies have been lost in the West Antarctic Peninsula (WAP). As a consequence, deglaciation is expected to impact the marine environment and its biota at physiological and ecosystem levels. Nuculana inaequisculpta is a marine bivalve widely distributed around Antarctica that plays an important role for ecosystem functioning. Considering that N. inaequisculpta inhabits coastal areas under effect of glacial melt and retreat, impacts on its nutritional condition are expected due to alterations on its physiology and food availability. To test this hypothesis, biochemical composition (lipids, proteins, and fatty acids) and energy content were measured in individuals of N. inaequisculpta collected in a fjord at different distances to the retreating glacier in the WAP. Oceanographic parameters of the top and bottom-water layers (temperature, salinity, dissolved oxygen, and chlorophyll-a) were measured to investigate how the environment changes along the fjord. Results showed that surface oceanographic parameters displayed a lower temperature and dissolved oxygen, but a higher salinity and chlorophyll-a content at nearest compared to farthest sites to the glacier. In contrast, a lower temperature and chlorophyll-a, and a higher salinity and dissolved oxygen was measured in the bottom-water layer toward the glacier. N. inaequisculpta had a higher amount of lipids (17.42 ± 3.24 vs. 12.16 ± 3.46%), protein (24.34 ± 6.12 vs. 21.05 ± 2.46%) and energy content (50.57 ± 6.97 J vs. 39.14 ± 5.80 J) in the farthest compared to the nearest site to the glacier. No differences were found in total fatty acids among all sites. It seems likely that lower individual fitness related to proximity to the glacier would not be related to nutritional quality of sediment food, but rather to food quantity.

The slipper limpet Crepipatella dilatata, native to Chile and Argentina, was introduced in Spain in 2005. The species was thought to inhabit the region of Rias Bajas, yet recently, putative C. dilatata populations have been documented on the coast of north-central Spain and in the Ebro Delta of the Spanish Mediterranean. Here we undertook a multidisciplinary approach to study the invasion biology of this species. Specifically, two geographically distant populations, one being a successfully established population from O Grove and the other a declining population from Gijon, were studied over the course of four years. Analyses of morphological and developmental traits as well as genetic information confirmed the presence of C. dilatata in these sites. The results revealed polymorphism in anatomical traits and shell shape. Shell shape polymorphism was unevenly distributed among sites and among sexes. Males were monomorphic, while females were polymorphic. Of the female morphotypes encountered, one was absent in the declining population from Gijón. Size at first female maturation and female size were greater in the declining population than in the established population. Reproductive success varied seasonally but not spatially among populations. In the established population, gregariousness was significantly greater; the size when sex changes was found to be plastic and socially controlled. The sex ratio of the declining population was female biased while in the established population the sex ratio changed during the study period from being balanced to being female biased. This change in sex ratio was probably due to higher male mortality. Molecular analyses pointed to the localities of Corral Bay in southern Chile and Puerto Madryn in southern Argentina as potential population sources. The intercontinental import of fresh mussels cultivated in Chilean farms is a likely source of this mussel in Spain. Comparison with available data of native populations of C. dilatata strongly indicate that ecophenotypic plasticity, socially controlled sex change, high gregariousness, increased nurse egg supply to viable larvae during the encapsulated developmental period, later maturation and larger female sizes altogether enhance establishment success of this non-indigenous species. Human-mediated factors like the intraregional mussel trade and transplantation are also likely secondary dispersal mechanisms favouring the spread of this organism.

Marine gastropods show pronounced plasticity in shell morphology in response to local environmental risks such as predation and dislodgement by waves. Previous studies have focused on juvenile and adult snails; however, adaptive plasticity might be expected to begin dur- ing embryonic and early post-embryonic stages as a means of increasing survivorship when indi- viduals first become vulnerable. We tested the above hypothesis by measuring shell morphology of encapsulated embryos and hatchlings of Acanthina monodon exposed to predator odor and water turbulence. Subjects were assigned to 1 of 4 treatments: (1) predator odor + high water tur- bulence, (2) no predator odor + high water turbulence, (3) predator odor + low water turbulence, (4) no predator odor + low water turbulence (control). After approximately 1 mo, morphological traits of the shell were measured using geometric morphometrics. Hatchlings, but not encapsu- lated offspring, produced larger shells in the predator treatments. Encapsulated offspring and hatchlings produced thicker shells in the predator treatments, irrespective of water turbulence, whereas thinner shells were produced when high water turbulence acted alone. Even before hatching, A. monodon can, thus, respond adaptively to potential mortality factors characterizing the local external environment. Anticipating risk in this way should enhance survivorship from the point of hatching through the vulnerable juvenile phase to adulthood.

Poecilogony is the production of different larval types within the same species. Although rare, poecilogonous species are ideal systems for testing the evolutionary and ecological implication of different developmental modes in marine invertebrates. Here, we described a new case of poecilogony, the Southern Hemisphere spionid Boccardia wellingtonensis. We used a combination of common-garden experiments, video recordings, and in vitro manipulations of individuals from three sites to (1) document the type of poecilogony, the brooding behavior of the mother, and the hatching process; (2) experimentally measure the effect of nurse eggs on the growth and type of larvae produced; and (3) document variation in the length of the brooding period, number of capsules, larvae, and nurse eggs of mothers from three sites to explore the potential for plasticity in reproductive traits. These results were compared to the previously reported poecilogonous species B. proboscidea, which resembles B. wellingtonensis in size, morphology, ecology, and reproductive strategy but differs in capsule structure. We found that in contrast to B. proboscidea, B. wellingtonensis produced larvae that, in isolation and in the presence of nurse eggs, developed into a wide range of offspring sizes. Mothers brood and hatch the larvae with frequent partial hatching of the brood during the brooding period. Although larvae could not liberate themselves, larvae crossed to other capsules as interconnections between capsules broke during the developmental period, potentially affecting food availability, sibling competition for nurse eggs, and cannibalism. Variation in brooding time and number of capsules deposited among sites suggest local adaptations.

The diversity of free-living nematodes in the beaches of two Antarctic islands, King George and Deception islands was investigated. We used morphological and molecular (LSU, and two fragments of SSU sequences) approaches to evaluate 236 nematodes. Specimens were assigned to at least genera using morphology and were assessed for the presence of cryptic speciation. The following genera were identified: Halomonhystera, Litoditis, Enoploides, Chromadorita, Theristus, Oncholaimus, Viscosia, Gammanema, Bathylaimus, Choanolaimus, and Paracanthonchus; along with specimens from the families Anticomidae and Linhomoeidae. Cryptic speciation was identified within the genera Halomonhystera and Litoditis. All of the cryptic species identified live sympatrically. The two cryptic species of Halomonhystera exhibited no significant morphological differences. However, Litoditis species 2 was significantly larger than Litoditis species 1. The utility of molecular data in confirming the identifications of some of the morphologically more challenging families of nematodes was demonstrated. In terms of which molecular sequences to use for the identification of free-living nematodes, the SSU sequences were more variable than the LSU sequences, and thus provided more resolution in the identification of cryptic speciation. Finally, despite the considerable amount of time and effort required to put together genetic and morphological data, the resulting advance in our understanding of diversity and ecology of free-living marine nematodes, makes that effort worthwhile.

In poecilogony, different types of larvae are produced within the same species. Previous studies have suggested maternal control of the production of larval types; however, it is not clear which factors or mechanisms generate contrasting developmental patterns among siblings. The spionid polychaete Boccardia proboscidea produces within the same capsule adelphophagic larvae that eat nurse eggs and siblings and complete all or most of their development inside the capsule (Type A larvae), and larvae with little growth until they hatch as planktotrophic larvae (Type B larvae). In this study, we manipulated capsule content to explore the factors determining larval type in B. proboscidea and the role of extra-embryonic maternal nutrition and sib–sib interaction in the developmental fate of offspring. When early larval stages were grown individually in vitro, with nurse eggs as the only food source, some of them remained small, while others continue developing into larger pre-competent larvae by feeding on nurse eggs. This suggests that larval types in B. proboscidea are determined very early in development and are not solely the product of sib–sib interaction inside the capsule. However, our data also suggest that hatching size variability within larval types of a clutch depends on nurse egg availability. Type B larvae grew normally to metamorphosis when phytoplankton was available, but suffered high rates of cannibalism by Type A larvae. These results are consistent with the hypothesis that individual larval fates are determined very early in development and that once their fate is determined, hatching size and intracapsular survival are affected by maternal food provisioning and sibling interaction.

The geographical expansion of invasive species depends mainly on its dispersal potential, and the abiotic and biotic factors affecting it. Knowing the invasive dynamic of non-native species, as well as its behavior at different natural or anthropogenic scenarios, is fundamental for planning conservation management policies and control plans. The invasive sea anemone Anemonia alicemartinae in habits from the north (18°S) to the south-central (36°S) coast of Chile and its distribution range has expanded by approximately 1,928 km in the last 50 years. Previous works have proposed that human-mediated southward transport associated with regional-scale maritime activities could explain its rapid spread. To evaluate this hypothesis, we used ecological niche models (ENM) to evaluate the potential colonization of the southernmost area of South America. Additionally, we conducted a post hoc analysis to evaluate the relationship between the prediction of the ENM and human activity measured as the number of landings of ships in ports. The models were built based on presence records of A. alicemartinae, and oceanographic variables. Results showed that sea surface salinity and annual sea surface temperature (variance) are the best predictor variables to explain the distribution of A. alicemartinae. There was a positive and significant relationship between the geographical distribution of the sea anemone predicted by the ENM and the number of landings, as a proxy of anthropogenic activity. The most susceptible areas to invasion were those that showed the highest variability in both oceanographic predictors. These areas included the Biobío region, Chiloé´s inland sea, Aysén, and Chacabuco regions, which together comprise two biogeographical provinces. These results sustain the proposed hypothesis and, overall, the results suggest that along with the characteristics of the life history of A. alicemartinae, oceanographic conditions and maritime transport as vector contribute to the southern range expansion of this invasive cryptogenic species in the Humboldt-current large marine ecosystem.

The coastal pelagic fish Normanichthys crock- eri inhabits the southeast Pacific coast and is a monotypic species of the Normanichthyidae family. Its ecologically and economic importance, and the high fishing pressure it is subjected to make N. crockeri an ideal target species for conservation. Here, we present 12 new hypervariable loci for this species. Allelic richness varied between 2 and 8 alleles, and observed heterozygosity ranged between 0.059 and 1.00. Two loci showed significant deviations from Hardy-Weinberg and revealed the presence of null alleles. These new loci have a high potential to be used in popu- lation genetics studies and fishery management plans.

Shell morphology in marine gastropods exhibits high intraspecific variability. Plasti- city appears to be the most common response; however, additive genetic variance would explain a significant amount of morphological variance promoting local adaptations. The marine gastro- pod Acanthina monodon is a direct developer with a low dispersal potential and high variability in shell morphology. Previous studies suggest that adult shell morphology could have an adaptive value that responds to the degree of wave exposure. Given the low dispersal potential of A. mono - don and the high temporal predictability of wave exposure conditions at the local scale, it was expected that selection would favour local adaptations with an important component of heritabil- ity. To test this hypothesis we estimated shell morphology heritability of A. monodon using pre- hatching juveniles from wave-exposed and wave-sheltered sites along the Chilean coast and using a geometric morphometrics approach. In addition, we compared shell morphology and size of pre-hatching juveniles between exposed and sheltered sites. Heritability of shell morphology was highly variable, ranging between 0.2 and 0.6 among sites. Shell morphology of pre-hatching individuals did not differ between exposed and sheltered conditions. These results suggest that the diversity of shell morphology in adults of A. monodon could be explained by a complex inter- action between plastic and heritable responses.

Encapsulation is a common strategy observed among marine caenogastropods. Although the capsule confers protection for embryos, its rigidity and strength pose a significant challenge as the larvae hatch. The factors that drive hatching among these benthic marine gastropods have scarcely been studied. In this study, we experimentally evaluated whether the capsule plug opening and larval release processes were synchronised with day/night or tidal cycles in the muricid gastropod Chorus giganteus. In addition, we tested the effect of different levels of light intensity on the swimming behaviour of pre- and post-hatching larvae. The results showed that capsule plug rupture occurred in synchronous pulses of capsule groups during both day and night. A periodogram analysis did not show circatidal rhythmicity in either the plug rupture or total number of capsules hatched. The highest percentage of larvae hatched at sunset and during the night (82.9%), whereas only 17% of them hatched during the day. These results demonstrate a circadian pattern. The swimming activity of the larvae decreased significantly with light intensity. In the darkness, over 80% of the larvae actively swam in the tank and the majority of the larvae initially moved toward the water surface. No swimming activity was observed at 500 μE ∗ m− 2∗ s− 1 of photon flux density. These results suggest that C. giganteus larvae present negative phototropism behaviour and that capsule plug degradation occurs by other processes like internal physical enzymatic actions.

Crepidula coquimbensis is a protandric marine gastropod with direct development and restricted mobility, which only inhabits inside of empty shells of other marine gastropods cohabiting with hermit crabs of the genus Pagurus. In this study, we report potential dispersal mechanisms of C. coquimbensis and the effect on its population genetic distance and structure, using the gene COI, in three localities of northern Chile. The results suggested that C. coquimbensis shows high levels of genetic differentiation at local scale, and the association with P. edwardsi would be its only one mechanism of dispersal.

International audience; Many marine gastropod species brood their embryos in thin-walled capsules to protect them during development. Despite its beneficial effects, encapsulation has two major constraints, nutrition and oxygen supply, which affect embryo development and larval survival. Developing embryos usually rely on intracapsular food sources provided by the mother, in the form of yolk, nurse eggs and intracapsular fluid. However, it is still not clear if they are able to feed on extracapsular sources that may cross the capsule wall. We investigated this possibility in the calyptraeid species Crepidula fornicata. In this species, the internal capsule wall thickness sharply decreases during embryonic development, which might change wall permeability to small organic molecules, thus providing embryos with external dissolved organic matter. To test this hypothesis, encapsulated and excapsulated embryos of C. fornicata were placed for 48 h in a C-13-enriched amino acid (L-alanine) solution. Excapsulated embryos were enriched in C-13 (+5.75%), which suggested that they were able to assimilate the labelled amino acid. In contrast, encapsulated embryos were weakly enriched (+0.75%), suggesting that encapsulation greatly reduces the potential for the use of extracapsular amino acids and that encapsulated embryos mainly rely on maternal food.

The toadfish Aphos porosus is a coastal benthic-demersal fish from the Southeastern Pacific coast. This species exhibits parental care and low dispersal potential, and it is subjected to bycatch by artisanal and industrial fisheries, which make A. porosus a susceptible species in conservation terms. In this work we present 18 polymorphic microsatellite loci for this species. Allelic richness varied between 2 and 8 alleles and observed heterocigocity ranged between 0.026 and 0.737. Fourteen of the 18 loci were unlinked, polymorphic and in Hardy–Weinberg equilibrium. The non-exclusion probability over all loci was very low (0.0013). These loci show potential for population genetic analyses, for studying reproductive strategies and supporting conservation policies for this species.

Oxygen supply inside egg masses has been reported as a constraint of embryo development. Many species that enclose their eggs in jelly masses or ovicapsules have strategies to avoid or reduce intracapsular hypoxia. In some amphibian species, a decrease in the wall thickness of the egg capsule over time produces an increase in oxygen conductance of the wall, reducing the problem of intracapsular oxygen limitation. Previous studies of gastropods have reported a decrease in the thickness of the capsules during development. However, there are no studies relating capsule thinning to the oxygen limitation problem in this group. This study links the thinning of egg capsules with oxygen diffusion as a possible mechanism to reduce or avoid hypoxia inside the capsules of the gastropod Fusitriton oregonensis. Capsule thickness, capsule area, oxygen partial pressure inside and outside the capsule, and oxygen consumption of the embryos at early and late developmental stages were measured. The conductance and the diffusion coefficients of the capsule were estimated using these measurements. Results showed that (1) capsule thickness decreased throughout development by about 50%, (2) oxygen consumption of embryos increased from early to late stages, (3) oxygen partial pressure inside the capsule did not change during development, (4) conductance coefficient increased with time, and (5) estimation of diffusion coefficient was lower than amphibian egg jelly, shark capsules, egg fishes, and eggs of giant cuttlefish. The reduction in the thickness of the capsule wall and the associated increase in its conductance during embryonic development may reduce oxygen constraints, especially at late developmental stages.

Studying the mating system of obligate aquatic organisms that inhabit river ecosystems is important for understanding its evolution as well as the role of biological and environmental factors in modulating population dynamics and species distributional patterns. Here, we studied the reproductive strategy of the Chilean endemic freshwater snail, Chilina dombeiana, in the Biobío River, one of the largest rivers in Chile. This species has a low potential for dispersal given the absence of a free-swimming larval stage (benthic larval development) and given that adults have a low capacity for mobility. We hypothesized that: 1. Females would mate with different males (polyandry) resulting in intrabrood multiple paternity, 2. Individuals from closer sites would be more related than individuals from distant sites, and 3. Male parental contributions would be unevenly distributed within broods. Individuals from three different sites were sampled along the river: upper, mid, and river mouth. In the laboratory, hatching juveniles from a total of 15 broods were collected for paternity analyses. We used microsatellite markers and the programs GERUD and COLONY to determine whether multiple paternity exists and to estimate the contribution of different males to the brood. We found that multiple paternity was very common at all of the sites analyzed with as many as 8 males fertilizing a single female and a mean of 4.2 fathers per brood estimated by COLONY. Sire contribution was skewed to particular males in several broods. In addition, overall relatedness among broods for the three sites ranged from 0.17 to 0.45 with evidence of many half-siblings. Relatedness differed among the three sites. Particularly in upstream sites or in anthropogenically disturbed populations, the high levels of multiple paternity observed in C. dombeiana may be an efficient strategy to avoid inbreeding and prevent the loss of genetic diversity within populations.

The population dynamics of the carrageenophyte Sarcothalia crispatais described from subtidal beds at two localities in south-central Chile. Seasonal fluctuations in total density and biomass were not evident. Frondswere identified to phase by the presence of reproductive structures and theresorcinol reaction. The monthly changes in abundance of each kind offrond were determined. Permanent gametophytic or sporophyticdominance was not evident: the more exposed site showed a seasonal shiftfrom sporophytic dominance in summer to gametophytic dominance inwinter, whereas the more protected site showed an interannual shift fromgametophytic to sporophytic dominance. The differences between localitiesand years suggest a very local population dynamics with large contributionof self-seeding to the maintenance of the S. crispata beds.

The shore crab (green) Carcinus maenas com- monly occurs in tide pools and channels where temporary hypoxia is experienced. Under such conditions, aerobic meta- bolism is limited, with possible consequences to prey-han- dling behaviour. We investigated this possibility by measur- ing the prey-handling times of C. maenas fed mussels Mytilus edulis under normoxic (5.9 ± 0.1 mg O2 l -1 ) and hypoxic con- ditions (1.08 ± 0.12 mg O2 l -1 ). The prey-handling time of smaller crabs (5.0 to 5.3 cm carapace width) feeding on rela- tively small, medium and large mussels was increased by hypoxia. The prey-handling time of larger crabs (7.1 to 7.3 cm carapace width) was increased by hypoxia only when feeding on relatively large mussels. Increases in prey-handling time were largely due to increases in the time taken to glean and ingest flesh, except for large mussels, for which time taken to break the shell became more important. The results show that hypoxia reduces prey-handling efficiency, presumably by limiting the capacity to increase aerobic metabolism, and that susceptibility to this decreases with increasing body size. Reduced prey-handling efficiency could place individuals at greater risk to competition and predation when subjected to hypoxia in the field.

The precision of the natural mortality rate (M) for Chilean hake (Merluccius gayi) is evaluated using empirical models in which a parametric bootstrap resampling method is incorporated. The empirical models of Pauly (Pauly, D., 1980. J. Cons. Int. Explor. Mer. 39(2), 175–192.), Rikhter and Efanov (Rikhter, V.A., Efanov, V.N., 1976. ICNAF Res. Doc. 76/VI/8:12 p.), and Hoening (Hoening, J.M., 1983. Fish. Bull. US, 82(1): 898–902.) were used to estimate M. The model estimates of M were evaluated based on the error in the estimates of the input parameters and the degree of significant differences between males and females. The average of 3000 equally probable and alternative values of M obtained using the models of Pauly and Hoening were similar for males and females. However, these models produced significant differences between sexes only when the error in the estimates of the input parameters was taken into account. There were not significant sexual differences when the prediction error was included in the variance estimation procedure. The ability to determine significant sexual differences is an important aspect which is usually overlooked in evaluating estimates of male and female M obtained from empirical models.

International audience; Sibling cannibalism is commonly observed in marine species. For instance, intrabrood cannibalism has been documented in marine gastropods with direct development, suggesting a relationship between embryo behavior and the evolution of life history strategies. However, there has been little effort to document the factors driving sibling cannibalism in marine species. The kin selection theory suggests that the level of relatedness plays an important role in cannibalism patterns. We examined Crepidula coquimbensis, a marine gastropod that broods and encloses its brooded offspring in capsules. Encapsulated embryos show sibling cannibalism and high levels of intracapsular multiple paternity. Given these features, cannibalistic behavior may be driven by kin-relatedness. To test this hypothesis, we constructed artificial aggregations of embryos to mimic three levels of relatedness: high, medium and low. For each category of aggregation, the cannibalism rate and benefits (i.e. size at hatching of surviving offspring) were estimated. In addition, at the end of embryo development, we performed parentage analyses to determine if cannibalism was associated with the relatedness between cannibal and victim embryos. Our results show that the intensity of sibling cannibalism increased in aggregations characterized by the lowest level of relatedness. There were important benefits of cannibalism in terms of hatching cannibal size. In addition, cannibalism between embryos was not random: the variation in reproductive success between males increased over the course of the experiment and the effective number of fathers decreased. Altogether, these results suggest that polyandry may play an important role in the evolution of sibling cannibalism in C. coquimbensis and that kin selection may operate during early embryonic stages in this species.

Three biogeographic areas have been recognized along the Chilean coast, with biogeo- graphic breaks located at 30 and 42° S allowing us to test the concordance between biogeographic patterns and spatial patterns of genetic and morphological diversity in marine species. We examined the marine gastropod Acanthina monodon, whose range spans the 2 major biogeographic breaks detected in the South-Eastern Pacific (SEP) coast. This species exhibits high variability in the mor- phology of its shell and has a direct development cycle. Based on the analysis of mitochondrial sequences of 258 individuals from 9 locations in the 3 biogeographic areas, we found 3 clades with contrasting levels of genetic diversity and with spatial population genetic structure. A perfect match between biogeography and pylogeography was observed only at the 30° S break. In contrast, we did not find a clear genetic break in concordance with the 42° S phylogeographic break, although haplo- type distribution suggested a second phylogeographic boundary located between 45 and 53° S. Only one haplotype was observed in the most southerly location, which may be explained by the historical influence of glaciations. A break in shell morphology was evidenced only at around 40 to 46° S, with a group characterized by thinner shells and longer spires compared to the northern group. Our results supported the concordance hypothesis and indicated that the influence of life cycle strategy, habitat discontinuity and historical processes may determine the phylogeographical and shell mor- phology spatial pattern of A. monodon. In contrast to previous studies, our genetic analysis showed the presence of a single Acanthina species along the SEP coast.

Intracapsular oxygen availability is one of the main factors affecting embryo development of marine gastropod species with encapsulation. This is because the low solubility and diffusion rate of O2in water, plus the low oxygen diffusion rate that the capsule wall presents, reduces oxygen inside capsules. In addition, temperature affects embryo development inside capsules through its effect on embryo metabolic rate and oxygen availability. In spite of both factors being highly correlated and that a synergic effect on embryo development may be expected, there are few studies evaluating temperature and intracapsular oxygen availability simultaneously. In this work we evaluated the role of the capsule wall of the marine gastropodChorus giganteusas a barrier for oxygen diffusion and its interaction with temperature affecting intracapsular oxygen availability and embryonic development. For that, we cultivated capsules in seawater at three different temperatures, 9, 12 and 15°C, for a time to complete embryo development. Oxygen level was measured inside capsules with and without embryos, and outside capsules at all temperatures. The number of capsules successfully hatched at the end of the experiment, and early and late embryo mortality were recorded. Finally, we measured embryo metabolic rate at the three different temperatures assayed. We found that embryo mortality and abnormal morphological development were more frequent at higher temperatures. Intracapsular oxygen availability decreases at higher temperatures in capsules with and without embryos. These results may be explained by an increase in the total intracapsular embryo metabolic rate (per capsule) with temperature and an inadequate oxygen diffusion rate from seawater through the capsule wall and intracapsular fluid to the embryonic cells. Our findings suggest that encapsulation is constrained at high temperatures inC. giganetusaffecting significantly its reproductive success. This may have important consequences in a scenario of global warming.

International audience; In gregarious species with copulation and internal fertilization, male-male competition and female cryptic choice may affect reproductive success of both sexes. We carried out a molecular analysis to study paternity and sperm use by females in the protandrous marine brooding gastropod Crepidula coquimbensis. In the field, a single female inhabits an empty hosting shell with up to six males. This gregarious behavior may promote intra-brood multiple paternity if females can store sperm from several consecutive copulations with the surrounding males. To study female sperm usage, the males sharing shelters with five different adult females were collected and preserved for paternity analysis. Females were transported alive to the laboratory and isolated for six months. After that, an additional male was offered to each of the five study females. Once the females had laid capsules, a total of 528 embryos from the five females were assigned paternity based on five microsatellite loci. Paternity analysis showed that every male sharing the empty hosting shell of a female as well as the additional male were assigned fatherhood of embryos laid by this specific female. Females can thus use sperms from multiple males including sperms stored for at least six months. In addition, in four out of the five offspring arrays, a similar contribution of each male to the brood was observed, a pattern associated with the close relationship between the number of fathers observed and the effective paternity index calculated. These results contrast with those of paternity analyses carried out in another species of the same genus. C. fornicata which is characterized by a stacking behavior in which the closest male to the female achieves the highest reproductive success. Male reproductive success may be largely influenced by the aggregation pattern and male mating opportunities in the Crepidula complex, a hypothesis to be examined further by studying other species exhibiting different grouping behavior. (C) 2010 Elsevier B.V. All rights reserved.

SUMMARYEncapsulation is a common strategy among marine invertebrate species. It has been shown that oxygen and food availability independently constrain embryo development during intracapsular development. However, it is unclear how embryos of species with different feeding strategies perceive these two constraints when operating jointly. In the present study, we examined the relative importance of dissolved albumen, as a food source, oxygen condition and their interaction on embryonic growth and the survival of two calyptraeid species, Crepidula coquimbensis and Crepidula fornicata,exhibiting different embryo feeding behaviours (i.e. presence vsabsence of intracapsular cannibalism). Two oxygen condition treatments(normoxia and hypoxia) and three albumen concentrations (0, 1 and 2 mg l–1) were studied. In addition, albumen intake by embryos was observed using fluorescence microscopy. Our study shows that embryos of both species incorporated dissolved albumen but used a different set of embryonic organs. We observed that embryo growth rates in C. coquimbensis were negatively affected only by hypoxic conditions. Conversely, a combination of low albumen concentration and oxygen availability slowed embryo growth in C. fornicata. These findings suggest that oxygen availability is a limiting factor for the normal embryo development of encapsulated gastropod species, regardless of feeding behaviour or developmental mode. By contrast,the effect of dissolved albumen as an alternative food source on embryo performance may depend on the feeding strategy of the embryos.

Oxygen availability in the aggregation of offspring has been shown to be a critical fac- tor affecting the survival and development of embryos in aquatic systems. It is not yet known, how- ever, to what extent the capacity to provide O2 to embryo aggregations may act on the time of parental protection (here encapsulation), ultimately determining indirect and direct embryonic development. We assessed O2 conditions during encapsulation, the factors determining those condi- tions, and the consequences on embryo survival in 2 gastropod species with contrasting developmen- tal modes: Crepidula fornicata, an indirect developer, and Crepidula coquimbensis, a direct devel- oper showing adelphophagy. Results showed that intracapsular O2 conditions decreased to almost hypoxic conditions throughout development in C. fornicata, in contrast to the oxygenated conditions observed in C. coquimbensis during the entire encapsulation period. These contrasting patterns between species were explained by: (1) differences in metabolic rate of the embryos, (2) differences in total metabolizing material per capsule throughout development, and (3) differences in wall thick- ness and rates of decay throughout development, which may affect O2 diffusion. Moreover, when the low O2 conditions observed at the end of the encapsulation period were maintained after hatching by artificially extending encapsulation for 3 d, a dramatic negative effect on embryonic survival was observed in the indirect developer. In contrast, no effect on juvenile survival was observed in the direct developer. We suggest that hatching at intermediate stages of embryonic development in C. fornicata may be a response to increased O2 constraints during the encapsulated period.

Reproductive output (RO) is commonly used as a proxy for reproductive effort (RE) among Brachyuran crabs and other marine invertebrates, and so far no attempt has been made to incorporate the cost of brooding into RE to obtain a more reliable estimate of reproductive invest- ment, nor to compare it along a temperature (latitudinal) gradient. We compared RO among 3 sites (ca. 20, 30 and 40° S, reflecting mean annual sea-surface temperatures of 18, 14 and 10°C, respec- tively), and the cost of brooding (oxygen provision) at those temperatures, in order to obtain a more reliable pattern of reproductive investment along an extended latitudinal gradient. A total of 187 brooding females of Cancer setosus were collected to estimate RO. Fecundity, volume and weight of the embryos, and embryo losses were also estimated. Laboratory experiments were carried out at the characteristic temperatures of those sites (acclimating females from central Chile) to determine (1) patterns of oxygen provision to the embryos, (2) patterns of brooding behavior, and (3) to quantify the cost of embryo ventilation. Optic fibers, video recording and respiration chambers were used to meet these goals. Results showed that (1) RO, (2) fecundity, and (3) volume and weight of embryos varied with latitude, and that temperature affects (1) period of embryo ventilation (oxygen provision) events, (2) flapping frequency, (3) embryo losses throughout the brooding period, and (4) cost of embryo ventilation per unit of time. While RO increased with latitude, the cost of embryo ventilation decreased with temperature, suggesting a trade-off between investment in eggs and the cost of pro- viding oxygen to the embryos at different temperatures (latitudes). This pattern may not be exclusive to Brachyuran crabs, but may also apply to other marine invertebrates since oxygen limitation during early development occurs in other brooding species.