Lecithotrophic Larvae Research Articles

On the larva and the zooid of the pterobranch Rhabdopleura recondita Beli, Cameron and Piraino, 2018 (Hemichordata, Graptolithina)

Hemichordates (Enteropneusta and Pterobranchia) belong to a small deuterostome invertebrate group that may offer insights on the origin and evolution of the chordate nervous system. Among them, the colonial pterobranch Rhabdopleuridae are recognized as living representatives of Graptolithina, a taxon with a rich fossil record. New information is provided here on the substrate selection and the life cycle of Rhabdopleura recondita Beli, Cameron and Piraino, 2018, and for the first time, we describe the nervous system organization of the larva and the adult zooid, as well as the morphological, neuroanatomical and behavioural changes occurring throughout metamorphosis. Immunohistochemical analyses disclosed a centralized nervous system in the sessile adult zooid, characterized by different neuronal subsets with three distinct neurotransmitters, i.e. serotonin, dopamine and RFamide. The peripheral nervous system comprises GABA-, serotonin-, and dopamine-immunoreactive cells. These observations support and integrate previous neuroanatomical findings on the pterobranch zooid of Cephalodiscus gracilis. Indeed, this is the first evidence of dopamine, RFamide and GABA neurotransmitters in hemichordates pterobranchs. In contrast, the lecithotrophic larva is characterized by a diffuse basiepidermal plexus of GABAergic cells, coupled with a small group of serotonin-immunoreactive cells localized in the characteristic ventral depression. It is envisaged the use of R. recondita as a novel and easily accessible hemichordate model organism to shed light on the evolution of hemichordates and more generally on the origin of deuterostome developmental mechanisms.

FoxA expression pattern in two polychaete species, Alitta virens and Platynereis dumerilii: Examination of the conserved key regulator of the gut development from cleavage through larval life, postlarval growth, and regeneration.

foxA orthologs are involved in various processes from embryo patterning to regulation of metabolism. Since foxA conserved role in the development of the gut of errant annelids has never been thoroughly studied, we used a candidate gene approach to unravel the molecular profile of the alimentary canal in two closely related nereid worms with a trochophore-type lecithotrophic larva. The character of foxA expression in the two polychaetes was similar but not identical. The genes were successively activated first in blastoporal cells, then in the stomodeum, the midgut, and hindgut primordia, and in the cells of central and peripheral nervous system. Before the start of active feeding of nectochaetes, we observed a short phase of foxA expression in the entire digestive tract. After amputation of posterior segments, foxA expression was established de novo in the new terminal part of the intestine, and then in the developing hindgut and the anus. We discovered an early marker of endoderm formation previously unknown in errant annelids. Its expression dynamics provided valuable insights into the gut development. Comparative analysis of foxA activity suggests its primary role in gastrulation morphogenesis independently of its type and in midgut and foregut specification. Developmental Dynamics 248:728-743, 2019. © 2018 Wiley Periodicals, Inc.

Coastal biophysical processes and the biogeography of rocky intertidal species along the south‐eastern Pacific

AbstractAimWe assess the spatial distribution of a suite of coastal biophysical characteristics and how their variability is related to the distribution and geographic range of a diverse assemblage of coastal benthic species with different larval dispersal strategies.LocationSouth‐eastern Pacific (SEP) coast between 18°20′S and 42°35′S.MethodsBiophysical variability was assessed using chlorophyll‐a concentration, sea surface temperature and the signal of turbid river plumes derived from MODIS onboard the Aqua satellite. We established the dominant spatial components using wavelet and coherence analysis, and evaluated the biogeographic structure of 51 rocky intertidal species sampled over ~2,600 km along the SEP using multivariate classification and regression trees.ResultsBiogeographic breaks detected here were consistent with recent biogeographic classification schemes. Distribution breakpoints for species with lecithotrophic larvae clustered around 30°S. We observed a previously unreported break in the distribution of species with planktotrophic larval dispersal strategies around 35°S. These breaks are related to coherence in the spatial structure of sea surface temperature, chlorophyll‐a and river outflow over different temporal scales. Regions with similar biophysical characteristics, and the breaks the separate them, are in striking agreement with the biogeographic patterns revealed by the multivariate classification trees.Main conclusionsOur results reconcile patterns of biogeographic structure reported for other groups of species along the SEP coast. We suggest that river outflow, a poorly studied coastal environmental forcing, may play an important role in determining the geographic distribution of rocky shore species, probably through its effects on larval dispersal patterns.

Nervous system characterization during the development of a basal echinoderm, the feather star Antedon mediterranea.

Neural development of echinoderms has always been difficult to interpret, as larval neurons degenerate at metamorphosis and a tripartite nervous system differentiates in the adult. Despite their key phylogenetic position as basal echinoderms, crinoids have been scarcely studied in developmental research. However, since they are the only extant echinoderms retaining the ancestral body plan of the group, crinoids are extremely valuable models to clarify neural evolution in deuterostomes. Antedon mediterranea is a feather star, endemic to the Mediterranean Sea. Its development includes a swimming lecithotrophic larva, the doliolaria, with basiepithelial nerve plexus, and a sessile filter-feeding juvenile, the pentacrinoid, whose nervous system has never been described in detail. Thus, we characterized the nervous system of both these developmental stages by means of immunohistochemistry and, for the first time, in situ hybridization techniques. The results confirmed previous descriptions of doliolaria morphology and revealed that the larval apical organ contains two bilateral clusters of serotonergic cells while GABAergic neurons are localized under the adhesive pit. This suggested that different larval activities (e.g., attachment and metamorphosis) are under the control of different neural populations. In pentacrinoids, the analysis showed the presence of a cholinergic entoneural system while the ectoneural plexus appeared more composite, displaying different neural populations. The expression of three neural-related microRNAs was described for the first time, suggesting that these are evolutionarily conserved also in basal echinoderms. Overall, our results set the stage for future investigations that will reveal new information on echinoderm evo-devo neurobiology.

The Larval Development of the Chiton Deshayesiella curvata (Carpenter in Dall, 1879) (Mollusca: Polyplacophora)

Chronological study of the larval development of the chiton Deshayesiella curvata with sketching of the first stages of egg division and embryos up to the seven-valved shell stage is presented for the first time. D. curvata exhibits pelagic development with lecithotrophic larvae. Larval eyes form at the age of 3 days; at the age of 6 days, a Schwabe organ appears near the eyes in the form of two pigmented spots. Chitons at the stage of seven-valved shell have larval eyes, as well as the Schwabe organ.

Origin of the trochophora larva

The trochophora larva, which is so well known from the marine plankton, is central to our understanding of the evolution of a large branch of the bilaterians. Two theories for this larval type have been prevalent, the trochaea theory and the theory proposed by Ivanova-Kazas. The embryology, or more precisely the cell-lineage, of these larvae seems to be central for our understanding of their origin, but important details have been missing. According to the trochaea theory, a circumblastoporal ring of blastomeres differentiates to follow the convoluted shape of the conspicuous ciliary bands of the larvae, with prototroch and metatroch around the mouth, forming a filtering system, and telotroch around the anus. According to the Ivanova-Kazas theory, the blastomeres with the ciliary bands develop through specialization of rings of cells of the general ciliation in a lecithotrophic larva. Now, a new cell-lineage study of the gastropod Crepidula has shown that the ring of cells at the edge of the blastopore develops into the band of cells carrying prototroch and metatroch, characteristic of the trochophora. This gives strong support to the trochaea theory.

Hydrological features above a Southern Ocean seamount inhibit larval dispersal and promote speciation: evidence from the bathyal mytilid Dacrydium alleni sp. nov. (Mytilidae: Bivalvia)

The Maud Rise seamount (65°07.80′S 2°39.60′E), a distinct habitat in the Southern Ocean, was studied during the ANDEEP-SYSTCO expedition in 2007–2008 to describe its unique benthic assemblage, characterised by higher biomass and lower diversity than other SO locations. Epibenthic sledge deployments during the expedition revealed exceptionally high abundances of the small bivalve genus Dacrydium with a total of 516 specimens collected from this seamount, resembling up to 1860 bivalve individuals per 1000 m−2. The Dacrydium specimens were examined for taxonomic identification, population and reproductive biology. Shell and soft part morphology as well as life history characteristics were compared with all known congeners for which data are available. Hinge dentition, prodissoconch size and adult gill structure are notably different, supporting classification as a separate species, herein formally described as Dacrydium alleni sp. nov. Dacrydium alleni sp. nov. produces lecithotrophic larvae, capable of long-distance dispersal, yet is apparently restricted to the Maud Rise area, supporting the hypothesis that larval dispersal at isolated seamounts may be constrained by hydrographic rather than biological features. In addition to providing insight into the benthic assemblage at Maud Rise, this work also summarises the current taxonomic status of the genus Dacrydium in the Southern Ocean.

Ontogenetic variation in photosensitivity of developing echinoderm propagules

Swimming behaviours and sensory abilities of early pelagic stages play a prominent role in the life history and ecology of sessile/sedentary benthic species, with implications for settlement, recruitment and dispersal. Light is a particularly important driver of navigational behaviour in the ocean, as a signal of key habitat characteristics (e.g., depth, shelter). Work to date on phototaxis has largely focused on planktotrophic larvae that feed during development, and much less on the larger lecithotrophic larvae that rely on maternal provisions (yolk). It remains unclear how responses to light might differ among ciliated propagules of different sizes and nutritional modes. The present study explored if/how phototactic responses are modulated by ontogeny (from embryo to larva), nutritional mode and light colour (wavelength) in ciliated propagules using four co-occurring species of echinoderms: the sea stars Asterias rubens and Crossaster papposus, the sea urchin Strongylocentrotus droebachiensis and the sea cucumber Cucumaria frondosa. Two types of behavioural responses to stimuli (white, red, and blue light) were examined: 1) taxis when the light stimulus was placed at one end of the chamber (net movement towards or away from the light stimulus) and 2) activity level, using a suite of swimming metrics, under uniform illumination. All four species consistently displayed some level of photosensitivity to white light and responses varied intra- and interspecifically. When the stimulus was red or blue light, planktotrophs modified their phototactic responses in a species- and stage-specific manner, while lecithotrophs generally displayed responses without a clear net direction. Swimming speeds displayed stage and species-specific variation under constant red or blue light, but swimming trajectories were consistently straighter under red light, resulting in greater displacement. Taken together, the results suggest that propagules of species with different life-history strategies respond to light stimuli in distinctive stage-wise manners. Interestingly, ontogenetic patterns were not conserved within nutritional modes or taxa. Further investigations of species-specific responses to light might help clarify its roles, in combination with factors such as buoyancy and gravity, in the ecology of propagules of benthic invertebrates.

How the position of mussels at the intertidal lagoon affects their infection with the larvae of parasitic flatworms (Trematoda: Digenea): A combined laboratory and field experimental study

In the complex trematode life cycle, cercariae transmit infection from the first to the second intermediate host. These short-lived lecithotrophic larvae possess a complex of behavioural responses for finding and infecting the host. We studied strategies used by cercariae of Himasthla elongata and Cercaria parvicaudata (Renicola sp.) infecting mussels Mytilus edulis at the White Sea intertidal. Laboratory and field experiments were conducted in parallel. Geotactic response of cercariae was tested in an experimental chamber. Their distribution in nature was studied by counting larvae infecting mussels in cages installed in pairs (a ground and a suspended cage) in an intertidal lagoon. In the chamber H. elongata cercariae concentrated at the bottom, C. parvicaudata cercariae aged 1h mostly concentrated near the surface and those aged 6h sank to the bottom. A few larvae of both species (“evaders”) showed behavioural patterns antithetic to the prevalent ones. Infection was the highest in mussels in ground cages. In suspended cages mussel infection with H. elongata cercariae was much lower than with C. parvicaudata cercariae. Our study confirmed that results of experiments on cercarial behaviour could be extrapolated to natural conditions. Cercariae of two species using the same intermediate hosts and co-occurring in a biotope implemented dramatically different strategies. This might be associated with differences in cercarial output by parthenitae groups. The presence of “evaders” might be useful for successful transmission. Our results indicate that mussels cultivated in suspended cultures are at the least risk of infection with trematode larvae.

Reproduction of the cold-water coral Primnoella chilensis (Philippi, 1894)

This study examined the reproduction of a cold-water coral, Primnoella chilensis (Philippi, 1894) from the Comau and Reñihué fjords in Chilean Patagonia. Samples were collected in September and November of 2012 and April, June, and September of 2013 from three sites within the two fjords. The sexuality, reproductive mode, spermatocyst stage, oocyte size, and fecundity were determined using histological techniques. This species is gonochoristic with one aberrant hermaphrodite identified in this study. Reproduction was found to be seasonal, with the initiation of oogenesis in September and suggested a broadcast spawning event between June and September. The maximum oocyte size was 752.96µm, suggesting a lecithotrophic larvae. The maximum fecundity was 36 oocytes per polyp. Male individuals were only found in April and June. In June, all four spermatocyst stages were present. This suggests that spermatogenesis requires less time than oogenesis in P. chilensis.

Ontogenetic shifts in swimming capacity of echinoderm propagules: a comparison of species with planktotrophic and lecithotrophic larvae

While developmental strategies can modulate the dispersal and recruitment of marine benthic species, the significance and drivers of propagule motility throughout ontogeny remain incompletely understood. Species with lecithotrophic (non-feeding) development are rarely studied, despite their predominance in some taxa, including echinoderms. Quantification of the swimming capacity (i.e. speed and trajectory) of early life history stages and its variability with environmental factors is required to improve the ability to predict population connectivity and assess trade-offs associated with complex life histories. In general, lecithotrophic larvae of echinoderms are ascribed weak swimming abilities relative to planktotrophic larvae, although explicit measures are scarce. Here, we explored selected metrics of swimming capacity in four co-occurring species of North Atlantic echinoderms displaying different types of pelagic development: planktotrophs represented by the sea star Asterias rubens and the sea urchin Strongylocentrotus droebachiensis, and lecithotrophs represented by the sea star Crossaster papposus and the sea cucumber Cucumaria frondosa. Swimming was characterized in still water based on the horizontal speed and path straightness of early life-history stages, from late blastula (hatched embryo) to late-stage larva. We tested the hypotheses that swimming capacity of propagules increases with progression through developmental stages and with increasing seawater temperature. Swimming speed increased with ontogeny in two of the four species (A. rubens and C. papposus) and with temperature in all species, although the effects of temperature were not uniform across life stages. The fastest swimming speeds across all species and temperatures were recorded in lecithotrophic propagules (i.e. max speed 1.2 mm s− 1 in the brachiolaria of C. papposus), whereas propagules of species with planktotrophic development displayed faster relative speeds (body lengths s− 1). Relative speeds increased with temperature in all tested species except C. papposus. Swimming paths typically increased in straightness from early to later developmental stages, and also became straighter with increased temperature in most species, except in C. papposus where they became more circular and complex. In general, planktotrophic and lecithotrophic propagules had similar swimming capacities when tested at the same level of increased temperature, though several stage-specific differences were detected; propagules of species with planktotrophic development had greater relative speeds at the gastrula stage and greater path-corrected speeds at the larval stage. Swimming paths and swimming speeds were similar between propagules of species with planktotrophic development and lecithotrophic development, suggesting that phylogenetically conserved, ontogenetic patterns of swimming capacity (seen here between two sea stars) may supersede the contribution of larval nutritional mode.

Carry-over effects of ocean acidification in a cold‑water lecithotrophic holothuroid

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 557:189-206 (2016) - DOI: https://doi.org/10.3354/meps11868 Carry-over effects of ocean acidification in a cold‑water lecithotrophic holothuroid Katie Verkaik1, Jean-François Hamel2, Annie Mercier1,* 1Department of Ocean Sciences, Memorial University, St John’s, Newfoundland and Labrador, A1C 5S7 Canada 2Society for the Exploration & Valuing of the Environment (SEVE), St Philips, Newfoundland and Labrador, A1M 2B7 Canada *Corresponding author: amercier@mun.ca ABSTRACT: Ocean acidification (OA) due to anthropogenic CO2 emissions is predicted to affect the world’s oceans in the near future. To date, knowledge remains limited on the response of species that are weakly calcified, produce lecithotrophic (non-feeding) larvae and live in polar/subpolar environments. The cold-water sea cucumber Cucumaria frondosa represents an ideal model for such investigations. One of the most abundant echinoderms in the world, it is annually-spawning, slow-growing and has been commercially exploited in the North Atlantic for over 35 yr. The present study examined the effects of predicted near-future OA scenarios on gametogenesis, spawning and embryonic development of C. frondosa, as well as on processes that may compete or coincide with reproductive effort such as ossicle formation and lipid synthesis. Sea cucumbers were exposed to a 0.4 unit pH decrease over 19 wk using a fully open flow-through design allowing for natural fluctuations in pH, light, temperature, salinity and nutrient levels. There were 2 treatment groups, ambient pH (7.9–8.2; pCO2 430–470 µatm) and low pH (7.5–7.7; pCO2 1330–1530 µatm). Results indicate that low pH/high pCO2 interferes with gamete synthesis, leading to discrepancies in oocyte/embryo buoyancy and morphology and developmental tempo, translating into 100% mortality before the blastula stage. Differences in the microstructural appearance of ossicles and the lipid contents of muscles, gonads and spawned oocytes were also highlighted. Such findings draw attention to previously understudied impacts of OA, including transgenerational effects in cold-water species with maternally provisioned eggs, and the resulting implications for temperate, subpolar and polar ecosystems. KEY WORDS: Ocean acidification · pH · Sea cucumber · North Atlantic · Reproduction · Lecithotrophic development · Polar environments Full text in pdf format Supplementary material PreviousNextCite this article as: Verkaik K, Hamel JF, Mercier A (2016) Carry-over effects of ocean acidification in a cold‑water lecithotrophic holothuroid. Mar Ecol Prog Ser 557:189-206. https://doi.org/10.3354/meps11868 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 557. Online publication date: September 28, 2016 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2016 Inter-Research.

Low genetic diversity and recent demographic expansion in the red starfish Echinaster sepositus (Retzius 1816).

Understanding the phylogeography and genetic structure of populations and the processes responsible of patterns therein is crucial for evaluating the vulnerability of marine species and developing management strategies. In this study, we explore how past climatic events and ongoing oceanographic and demographic processes have shaped the genetic structure and diversity of the Atlanto-Mediterranean red starfish Echinaster sepositus. The species is relatively abundant in some areas of the Mediterranean Sea, but some populations have dramatically decreased over recent years due to direct extraction for ornamental aquariums and souvenir industries. Analyses across most of the distribution range of the species based on the mitochondrial cytochrome c oxidase subunit I gene and eight microsatellite loci revealed very low intraspecific genetic diversity. The species showed a weak genetic structure within marine basins despite the a priori low dispersal potential of its lecithotrophic larva. Our results also revealed a very recent demographic expansion across the distribution range of the species. The genetic data presented here indicate that the species might be highly vulnerable, due to its low intraspecific genetic diversity.

Investigation of population structure in Gulf of Mexico Seepiophila jonesi (Polychaeta, Siboglinidae) using cross-amplified microsatellite loci.

BackgroundVestimentiferan tubeworms are some of the most recognizable fauna found at deep-sea cold seeps, isolated environments where hydrocarbon rich fluids fuel biological communities. Several studies have investigated tubeworm population structure; however, much is still unknown about larval dispersal patterns at Gulf of Mexico (GoM) seeps. As such, researchers have applied microsatellite markers as a measure for documenting the transport of vestimentiferan individuals. In the present study, we investigate the utility of microsatellites to be cross-amplified within the escarpiid clade of seep vestimentiferans, by determining if loci originally developed for Escarpia spp. could be amplified in the GoM seep tubeworm, Seepiophila jonesi. Additionally, we determine if cross-amplified loci can reliably uncover the same signatures of high gene flow seen in a previous investigation of S. jonesi.MethodsSeventy-seven S. jonesi individuals were collected from eight seep sites across the upper Louisiana slope (<1,000 m) in the GoM. Forty-eight microsatellite loci that were originally developed for Escarpia laminata (18 loci) and Escarpia southwardae (30 loci) were tested to determine if they were homologous and polymorphic in S. jonesi. Loci found to be both polymorphic and of high quality were used to test for significant population structuring in S. jonesi.ResultsMicrosatellite pre-screening identified 13 (27%) of the Escarpia loci were homologous and polymorphic in S. jonesi, revealing that microsatellites can be amplified within the escarpiid clade of vestimentiferans. Our findings uncovered low levels of heterozygosity and a lack of genetic differentiation amongst S. jonesi from various sites and regions, in line with previous investigations that employed species-specific polymorphic loci on S. jonesi individuals retrieved from both the same and different seep sites. The lack of genetic structure identified from these populations supports the presence of significant gene flow via larval dispersal in mixed oceanic currents.DiscussionThe ability to develop “universal” microsatellites reduces the costs associated with these analyses and allows researchers to track and investigate a wider array of taxa, which is particularly useful for organisms living at inaccessible locations such as the deep sea. Our study highlights that non-species specific microsatellites can be amplified across large evolutionary distances and still yield similar findings as species-specific loci. Further, these results show that S. jonesi collected from various localities in the GoM represents a single panmictic population, suggesting that dispersal of lecithotrophic larvae by deep sea currents is sufficient to homogenize populations. These data are consistent with the high levels of gene flow seen in Escarpia spp., which advocates that differences in microhabitats of seep localities lead to variation in biogeography of separate species.

Expression of GATA and POU transcription factors during the development of the planktotrophic trochophore of the polychaete serpulid Hydroides elegans.

The expression of transcription factors with endodermal and mesodermal roles in bilaterians is characterized during the development of Hydroides elegans, a serpulid polychaete with planktotrophic trochophore. GATA 4/5/6 is expressed in endodermal and mesodermal precursors during embryogenesis and in the midgut of trochophore larvae. HeGATA1/2/3a is expressed in animal hemisphere blastomeres 1d121 and 1d122, in dorsal ectoderm and in 4d endomesodermal derivatives that maintain their expression in trochophore larvae. HeGATA1/2/3b is not expressed during embryogenesis, but in several regions of the larva during postembryonic development. During very early gastrulation, Brn1/2/4 is first expressed in cells associated with the prospective oral/foregut side of the blastopore, and during larval development in 4d blastomere descendants. Comparison with orthologs in other metazoans suggests ancestral expression of GATA4/5/6 in the midgut of the last common ancestor of protostomes and deuterostomes. The conserved expression of Brn1/2/4 in the foregut precursors of Hydroides and sea urchins suggests an ancestral role in patterning the tripartite gut of planktotrophic larvae. Broader analysis of these and other regulatory genes reveals variability of developmental gene expression among polychaetes with lecithotrophic larvae, suggesting that they are evolutionarily derived from polychaetes with planktotrophic larvae.

Do benthic meiofaunal and macrofaunal communities respond to seasonality in pelagial processes in an Arctic fjord (Kongsfjorden, Spitsbergen)?

This study explores whether the marked seasonality in pelagic productivity and phytodetritus fluxes to the sea bottom in an Arctic fjord is reflected in variability of benthic communities in terms of taxonomic composition and standing stocks. Three stations located along the Kongsfjorden (west Spitsbergen) axis were visited in four seasons (May, August, October and January), and meiofauna and macrofauna was sampled. The elusive seasonal variability in benthic attributes contrasted with the clear seasonal effects in organic matter productivity and vertical fluxes (with diatom bloom-related peak in spring). No consistent differences in meiofaunal and macrofaunal density, diversity or composition among the four seasons were detected by PERMANOVA tests. Possible responses to spring food supply in meiofaunal reproduction timing were demonstrated in variability in individual size of Nematoda (decline in October after the maximum in August), Harpacticoida (decline in May and increase till October) and macrobenthic Crustacea (minimum in May). The spatial patterns shaped by the environmental gradients related to glacial inputs, the faunal impoverishment in inner basin and a shift in dominants along the fjord axis, were clearly designated and stable throughout the year. The resilience of Arctic fjordic benthic community to marked seasonality in pelagic phytodetritus fluxes may be related to organic matter reserves in sediments (large enough to sustain the detritus feeders on a year-round basis), inclusion of macroalgal carbon into the diet and common employment of lecithotrophic larva or direct development by polar benthos.

Development of the Sea Star Echinaster (Othilia) brasiliensis, with Inference on the Evolution of Development and Skeletal Plates in Asteroidea.

We describe the development and juvenile morphology of the sea star Echinaster (Othilia) brasiliensis in order to explore evolutionary developmental modes and skeletal homologies. This species produces large, buoyant eggs (0.6 ± 0.03 mm diameter), and has a typical lecithotrophic brachiolaria larva. The planktonic brachiolaria larva is formed 2-4 days after fertilization, when cilia cover the surface. Early juveniles are completely formed by 18 days of age. Initial growth is supported by maternal nutrients while the stomach continues to develop until 60 days after fertilization, when juveniles reach about 0.5 mm of radius length. The madreporite was observed 88 days after fertilization. In the youngest juvenile skeleton of E. (O.) brasiliensis, the madreporite and odontophore are homologous to those of other recent, non-paxillosid asteroids, and follow the Late Madreporic Mode. The emergence of plates related to the ambulacral system follows the Ocular Plate Rule. The development and juvenile skeletal morphology of this species are similar to those of the few other studied species in the genus Echinaster. This study corroborates the notion that the mode of development--including a short-lived lecithotrophic brachiolaria larva--in all Echinaster species shares a similar pattern that may be conserved throughout the evolutionary history of the group.

Spatio-temporal patterns of demographic and genetic structure in the red starfish Echinaster sepositus

Event Abstract Back to Event Spatio-temporal patterns of demographic and genetic structure in the red starfish Echinaster sepositus Creu Palacín1*, Alex García-Cisneros1, Marta Arjona1, Owen S. Wangensteen2 and Rocío Pérez-Portela3 1 University of Barcelona, Department of Animal Biology, Spain 2 University of Salford, School of Environment & Life Sciences Salford, United Kingdom 3 University of Miami, Marine Biology & Ecology Rosenstiel School of Marine & Atmospheric Science, United States Population structure has two different, but related, components: demographic structure and genetic structure. The first one is determined by all life-history processes, such as birth, death, reproduction and dispersal. The genetic structure is shaped by demographic structure, but also by other genetic processes such as selection, recombination and mutation. The spatial and temporal patterns of genetic variability in benthic invertebrates with pelagic larval stages determine the genetic structure of the cohorts at small scales. In this work, we analyzed the size structure as well as the genetic variability at spatial and temporal scales between different putative cohorts of the red starfish Echinaster sepositus. This species has lecithotrophic larvae, with limited dispersion capacity. Its populations show a typical patchy distribution at large scales, being locally abundant in some localities, while it can be absent from nearby areas. Assessment of population density and size structure was carried out in Sant Feliu de Guíxols (Girona, NW Mediterranean) every 6 months along 5 years, at two different depths. Furthermore, we studied the genetic structure at the same locality using eight polymorphic microsatellite markers on the first, third and fifth years. Two different cohorts (classified using the arm size of the individual) were genotyped separately in order to assess temporal patterns of genetic structure. For assessment of the genetic spatial variability, we genotyped twice another population from Blanes (Girona, NW Mediterranean), 35 km away. We did not find significant differences in population densities along the five years, nor between depths. The size structure followed a normal distribution. Arm sizes between 40 and 60 mm were the most abundant. Some differences in size were found between the two depths, with a trend of individuals from the deepest area being bigger. We did not found significant genetic differences between years for the two analyzed cohorts (< 30 mm and > 60 mm in arm size). However, observed heterozygosis was higher in small individuals from the two localities, indicating that the effective number of reproductive individuals may be increasing in these populations. Acknowledgements This work has been funded by project ChallenGen (CTM2013-48163) from the Spanish Ministry of Economy and Competitiveness. Keywords: Echinaster sepositus, Spatio-temporal patterns, Genetic structure, size structure population, Asteroidea Conference: XIX Iberian Symposium on Marine Biology Studies, Porto, Portugal, 5 Sep - 9 Sep, 2016. Presentation Type: Oral Presentation Topic: 1. ECOLOGY, BIODIVERSITY AND VULNERABLE ECOSYSTEMS Citation: Palacín C, García-Cisneros A, Arjona M, Wangensteen OS and Pérez-Portela R (2016). Spatio-temporal patterns of demographic and genetic structure in the red starfish Echinaster sepositus. Front. Mar. Sci. Conference Abstract: XIX Iberian Symposium on Marine Biology Studies. doi: 10.3389/conf.FMARS.2016.05.00011 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 29 Apr 2016; Published Online: 02 Sep 2016. * Correspondence: Dr. Creu Palacín, University of Barcelona, Department of Animal Biology, Barcelona, Barcelona, 08028, Spain, cpalacin@ub.edu Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Creu Palacín Alex García-Cisneros Marta Arjona Owen S Wangensteen Rocío Pérez-Portela Google Creu Palacín Alex García-Cisneros Marta Arjona Owen S Wangensteen Rocío Pérez-Portela Google Scholar Creu Palacín Alex García-Cisneros Marta Arjona Owen S Wangensteen Rocío Pérez-Portela PubMed Creu Palacín Alex García-Cisneros Marta Arjona Owen S Wangensteen Rocío Pérez-Portela Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Interacting environmental stressors modulate reproductive output and larval performance in a tropical intertidal barnacle

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 532:161-175 (2015) - DOI: https://doi.org/10.3354/meps11377 Interacting environmental stressors modulate reproductive output and larval performance in a tropical intertidal barnacle Florian Freuchet1, Réjean Tremblay1, Augusto A. V. Flores2,* 1Institut des sciences de la mer-Université du Québec à Rimouski, 310 allée des Ursulines, Rimouski, Québec G5L3A1, Canada 2Universidade de São Paulo, Centro de Biologia Marinha (CEBIMar/USP), Rod. Manoel Hipólito do Rego, km 131.5, 11600-000, São Sebastião, São Paulo, Brazil *Corresponding author: guca@usp.br ABSTRACT: Tropical intertidal filter-feeding invertebrates often face thermal stress and oligotrophic nearshore conditions, which may modulate reproductive responses. In order to investigate how these stressors affect resource allocation for reproduction, we first acclimated experimental populations of the higher shore barnacle Chthamalus bisinuatus to different levels of food supplies, to obtain baseline reproductive parameters, and then submitted them to consecutive stress events, by transferring populations to chambers where temperature was either unchanged (25°C) or increased to critical levels (45°C). Thermal stress decreased overall adult survival by 15% and overall larval release by 53%, while no significant effects of food shortage were detected. Experimental populations after moderate short-term stress events (transfer to control chambers) showed anticipatory fitness effects by increasing both the quantity and the quality of larvae, which survived longer without an exogenous food supply. After severe stress, parents first decreased larval release rate (thermal stress) and then produced lower-quality larvae (thermal stress plus food shortage), compatible with a selfish strategy. Lipid analyses showed that adults are very efficient in retaining essential fatty acids (EFAs) and capable of fast accumulation of reserve lipids shortly after stress, which however decreased over the experiment. Chronic stress led to decreased transfer of reserve lipids to larvae, and increased transfer of EFAs, suggesting a compensatory effect on larval quality. Populations exposed to both stressors lacked these temporal trends and produced low-quality nauplii. Unexpectedly, parental manipulation seems to involve the allocation of EFAs, not reserve lipids, as usually reported for lecithotrophic larvae. KEY WORDS: Parental effects · Reproductive investment · Planktotrophic larvae · Life-history tactics · Reproductive strategy · Offspring manipulation · Rocky shore Full text in pdf format Supplementary material PreviousNextCite this article as: Freuchet F, Tremblay R, Flores AAV (2015) Interacting environmental stressors modulate reproductive output and larval performance in a tropical intertidal barnacle. Mar Ecol Prog Ser 532:161-175. https://doi.org/10.3354/meps11377 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 532. Online publication date: July 21, 2015 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2015 Inter-Research.

Nervous system development in lecithotrophic larval and juvenile stages of the annelid Capitella teleta.

BackgroundReconstructing the evolutionary history of nervous systems requires an understanding of their architecture and development across diverse taxa. The spiralians encompass diverse body plans and organ systems, and within the spiralians, annelids exhibit a variety of morphologies, life histories, feeding modes and associated nervous systems, making them an ideal group for studying evolution of nervous systems.ResultsWe describe nervous system development in the annelid Capitella teleta (Blake JA, Grassle JP, Eckelbarger KJ. Capitella teleta, a new species designation for the opportunistic and experimental Capitella sp. I, with a review of the literature for confirmed records. Zoosymposia. 2009;2:25–53) using whole-mount in situ hybridization for a synaptotagmin 1 homolog, nuclear stains, and cross-reactive antibodies against acetylated α-tubulin, 5-HT and FMRFamide. Capitella teleta is member of the Sedentaria (Struck TH, Paul C, Hill N, Hartmann S, Hosel C, Kube M, et al. Phylogenomic analyses unravel annelid evolution. Nature. 2011;471:95–8) and has an indirectly-developing, lecithotrophic larva. The nervous system of C. teleta shares many features with other annelids, including a brain and a ladder-like ventral nerve cord with five connectives, reiterated commissures, and pairs of peripheral nerves. Development of the nervous system begins with the first neurons differentiating in the brain, and follows a temporal order from central to peripheral and from anterior to posterior. Similar to other annelids, neurons with serotonin-like-immunoreactivity (5HT-LIR) and FMRFamide-like-immunoreactivity (FMRF-LIR) are found throughout the brain and ventral nerve cord. A small number of larval-specific neurons and neurites are present, but are visible only after the central nervous system begins to form. These larval neurons are not visible after metamorphosis while the rest of the nervous system is largely unchanged in juveniles.ConclusionsMost of the nervous system that forms during larvogenesis in C. teleta persists into the juvenile stage. The first neurons differentiate in the brain, which contrasts with the early formation of peripheral, larval-specific neurons found in some spiralian taxa with planktotrophic larvae. Our study provides a clear indication that certain shared features among annelids - e.g., five connectives in the ventral nerve cord - are only visible during larval stages in particular species, emphasizing the need to include developmental data in ancestral character state reconstructions. The data provided in this paper will serve as an important comparative reference for understanding evolution of nervous systems, and as a framework for future molecular studies of development.Electronic supplementary materialThe online version of this article (doi:10.1186/s12983-015-0108-y) contains supplementary material, which is available to authorized users.