Dispersal strategies in sponge larvae: integrating the life history of larvae and the hydrologic component

While known to be uniformly non-feeding, short-lived, and potentially short dispersing, sponge larvae display different behaviours (swimming ability and taxis). Our aim was to show whether sponge larvae with different behaviours exhibit different dispersal strategies under variable intensity of water movements. We first assessed the distribution of larvae of six taxa: Dictyoceratida spp., Dysidea avara, Crambe crambe, Phorbas tenacior, Scopalina lophyropoda, and Cliona viridis, collected through plankton sampling, and the abundance of the corresponding adult sponges across three hard bottom communities and a sandy bottom from a north-west Mediterranean rocky shore. We then tested adult–larvae couplings (abundance of larvae vs abundance of adults) under increasing levels of water movements (surge) to assess the importance of this environmental factor in driving differences in dispersal strategies. Adults of Dictyoceratida spp., D. avara, and P. tenacior were most abundant in semi-dark caves (SDC), C. crambe and C. viridis in communities of sciaphilic algae (SA), whereas the distribution of S. lophyropoda was extremely patchy, being present almost only in the SA community of one of the five stations studied. Larvae of Dictyoceratida spp. and P. tenacior were more abundant in the SDC, whereas D. avara and C. crambe were homogeneously distributed across the communities. The larvae of C. viridis were more abundant in the SA communities and the S. lophyropoda larvae were mostly present in one station and one community (SA). Increased water movement did not modify the adult–larvae coupling for Dictyoceratida spp., D. avara, and C. crambe, whereas it broke up the positive association for P. tenacior and to some extent S. lophyropoda. For C. viridis, possible variability in adult–larvae coupling was not tested because the larvae were collected on only one day under calm sea conditions. We confirm that efficient-swimming larvae with some cue response can actively counteract hydrodynamic forces and highlight the importance of both larval behaviour and environmental conditions in determining small-scale patterns of dispersal.     

Relationship between swimming capacities and morphological traits of fish larvae at settlement stage: a study of several coastal Mediterranean species

Experimental measurements were made in the laboratory to determine the swimming capacities of settlement-stage fish larvae of several Mediterranean coastal species collected from the nearshore waters of Corsica, France. Critical swimming speed (U_crit, cm s⁻¹) was measured to provide a realistic laboratory estimate of in situ swimming speed. Morphometric traits were measured to assess potential predictors of a species’ swimming ability and, when possible, daily otolith increments were used to estimate age. Observed swimming speeds were consistent with other temperate species and demonstrated that the tested species are competent swimmers and not passive components of their environment. Morphological traits varied in their correlation with U_crit across groups and species. Direct measurements of morphological traits were better predictors than calculated ratios. Pelagic larval duration had little relationship with swimming speed among species for which daily otolith increments were counted. In addition to expanding the database on swimming capacities of settlement-stage fish larvae in the Mediterranean Sea, this study also developed methods that simplify the assessment of larval fish swimming ability. Swimming speed data are essential for improving larval dispersal models and for predicting recruitment rates in coastal fish populations.     

Copepods of the genus Asterocheres (Copepoda: Siphonostomatoida) feeding on sponges: behavioral and ecological traits

Abstract. Four copepod species of the genus Asterocheres (A. echinicola, A. latus, A. suberitis and A. complexus ) are recorded for the first time as associated with Mediterranean sponges of the classes Calcarea and Demospongiae (orders Dictyoceratida, Dendroceratida, and Poecilosclerida). Individuals of A. suberitis are described for the first time as inhabiting sponges other than Suberites domuncula . The copepods seemed to use their trunk to suck the material (cuticles or excreted cells) produced at the sponge periphery (ectosome), which indicates that their feeding habits are similar to those observed in species of the same genus that feed on exfoliated tissues of echinoderms. In the laboratory, copepods fed on young sponges (rhagons) of the species Crambe crambe, Cacospongia mollior , and Dysidea avara without reducing the rhagon biomass. In contrast, rhagons of the species Haliclona sp., Hymedesmia spp., and Phorbas tenacior were consumed and their biomass reduced. This may be because the latter group does not produce external proteinaceous material. Copepod offspring were continuously released (∼6 nauplii every 48 h) and the larval stages were capable of limited swimming. We found significantly more copepods over the surface of the sponges than inside them. Copepod abundance was positively correlated with the sponge surface area while not with the sponge biomass. These results indicate that the copepods live preferentially over the sponge surface and that their abundance is surface-area dependent. The behavioral traits described here indicate that the interactions between asterocherid species and sponges are worthy of future study.     

Temporal Patterns of Larval Fish Occurrence in a Large Subtropical River

Knowledge of temporal patterns of larval fish occurrence is limited in south China, despite its ecological importance. This research examines the annual and seasonal patterns of fish larval presence in the large subtropical Pearl River. Data is based on samples collected every two days, from 2006 to 2013. In total, 45 taxa representing 13 families and eight orders were sampled. The dominant larval family was Cyprinidae, accounting for 27 taxa. Squaliobarbus curriculus was the most abundant species, followed by Megalobrama terminalis, Xenocypris davidi, Cirrhinus molitorella, Hemiculter leuscisculus and Squalidus argentatus. Fish larvae abundances varied significantly throughout the seasons (multivariate analyses: Cluster, SIMPROF and ANOSIM). The greatest numbers occurred between May and September, peaking from June through August, which corresponds to the reproductive season. In this study, redundancy analysis was used to describe the relationship between fish larval abundance and associated environmental factors. Mean water temperature, river discharge, atmospheric pressure, maximum temperature and precipitation play important roles in larval occurrence patterns. According to seasonal variations, fish larvae occurrence is mainly affected by water temperature. It was also noted that the occurrence of Salanx reevesii and Cyprinus carpio larvae is associated with higher dissolved oxygen (DO) concentrations, higher atmospheric pressure and lower water temperatures which occur in the spring. On the other hand, M. terminalis, X. davidi, and C. molitorella are associated with high precipitation, high river discharge, low atmospheric pressure and low DO concentrations which featured during the summer months. S. curriculus also peaks in the summer and is associated with peak water temperatures and minimum NH₃–N concentrations. Rhinogobius giurinus occur when higher atmospheric pressure, lower precipitation and lower river discharges occur in the autumn. Dominant fish species stagger their spawning period to avoid intraspecific competition for food resources during early life stages; a coexistence strategy to some extent. This research outlines the environmental requirements for successful spawning for different fish species. Understanding processes such as those outlined in this research paper is the basis of conservation of fish community diversity which is a critical resource to a successful sustainable fishery in the Pearl River.     

Ontogeny and distribution of Hygophum benoiti(Pisces, Myctophidae) of the North Western Mediterranean

Two species of the lanternfish genus Hygophum, H.benoiti andH.hygomii, are present in the Mediterranean. Differentiationof the larvae from these two species has been problematic. Anattempt to identify such larvae in the plankton samples of theNorth Western Mediterranean led to a broader study that includedthe examination of a large number of plankton samples collectedin the region since 1976. The large number of Hygophum larvaeobtained during July 1992 in the North Western Mediterranean(that proved to be H.benoiti), together with collections oflarvae from different geographic areas (especially H.hygomiifrom the Southwest Indian Ocean), allowed a detailed morphometriccomparison of the larvae of H.benoiti and H.hygomii. Developmentalstages of H.benoiti from yolk sac to post-flexion larvae aredescribed. Information on the temporal occurrence of H.benoitiin the plankton, as well as the spatial distribution of thisspecies during the survey of peak abundance (June/July 1992)in the North Western Mediterranean, is presented.     

Descriptions of some planktonic larvae of the Calappidae (Crustacea: Decapoda; Brachyura)

Some unidentified planktonic larval stages have been assignedto the Calappidae using Rice's key of Brachyura families. Zoeastage I from the eastern region of the Algerian coast (westernMediterranean Sea) has been attributed, according to Manningand Holthuis (1980), to Calappa granulata (L.), the only recordedrepresentative of the family from the Mediterranean Sea. Zoealstages 1-lV from the Jordanian coast of the Gulf of Aqaba, NorthernRed Sea, have been reported to the subfamily Matutinae. Comparisonsof larvae of Calappa and of Hepatus and then, of larvae of Hepatusand of Matuta, show that Hepatus larvae are more closely relatedto those of Calappa, while those of Matuta are clearly distinct.It s suggested to place the genus Hepatus with the Calappinae.Guinot (1966. 1978) placed some genera, including Hepatus. ina 'unit parthenoxystomienne, lea Aethrinae'. Larval developmentis unknown for Aethra, Actaeomorpha. Hepatella andOsachila.However, comparison of Hepatus larvae with those of Parthenopidaeshows that larval characters, particularly the setation of theendopod of the first maxilliped, are not conclusive for supportingsuch a regrouping. Moreover, the Calappidae have a combinationof primitive and advanced features which suggest that theirgrouping in the Oxystomata seems more likely to be an adaptationto a similar way of life. The morphotypal taxon Oxystornatahas been definitively rejected by Guinot (1978).     

The surf zone: a semi-permeable barrier to onshore recruitment of invertebrate larvae?

The supply of larvae to the shore is important for population replenishment and intertidal community dynamics but its variability at most scales is not well understood. We tested the relationship between nearshore mussel larval abundance and intertidal settlement rates over several years at multiple spatiotemporal scales in Oregon and New Zealand. Abundance of competent larvae nearshore and intertidal recruitment rates were simultaneously quantified using collectors mounted at different depths on moorings 50-1100 m from shore, and at adjacent rocky intertidal sites. Total mussel larval abundance and oceanographic conditions were also measured in some locations. At all scales, abundance of nearshore mussel larvae was unrelated to intertidal recruitment rates. In the intertidal, patterns of mussel recruitment were persistent in space, with sites of consistently high or low recruitment. In contrast, nearshore competent larval abundance showed generally similar abundances among sites except for a high, and spatially-inconsistent, variability in Oregon during 1998 only. On moorings, recruitment tended to be greater on midwater collectors than shallower or deeper. Finally, on moorings larval abundance in traps and recruitment on collectors was unrelated. These results suggest that (1) among sites, the size of the nearshore larval pool is relatively uniform while onshore recruitment varies and is unrelated to larval abundance, (2) temporal variability in nearshore larval availability is not strongly expressed onshore, (3) vertical stratification of competent larvae nearshore is strong and may influence transport and recruitment, and (4) within-coast variability in onshore recruitment is strongly driven by processes occurring locally within the surf zone that need to be studied to understand coastal recruitment dynamics.     

Temperature-dependent stage durations of Irish Sea Nephrops larvae

The relationships between temperature and stage duration ofthe three zoea stages of Irish Sea Nephrops norvegicus wereinvestigated by culturing individual larvae at five differenttemperatures. The relationships are required for estimatingdaily larval production from survey data on abundance. The survivalof cultured larvae was relatively high. Estimates of the temperature–stageduration relationships from data of individual larvae were differentfrom a previous Irish Sea study. However, using the averageduration at each temperature gave relationships that were notsignificantly different from previous studies in the Irish Seaand Clyde. No larvae were successfully reared to stage IV (post-zoea)at lower temperatures, so it was impossible to assess the relationshipbetween stage III larval duration and temperature.     

Seasonal dynamics in the abundance of Micromonas pusilla (Prasinophyceae) and its viruses in the Gulf of Naples (Mediterranean Sea)

To assess the role of viruses in the bloom dynamics of Micromonaspusilla in the Gulf of Naples (Mediterranean Sea), variationsof host and virus abundance were followed over one annual cycleand in late winter–spring of three consecutive years.Micromonas pusilla was recorded from autumn to spring, withpeak values up to 6.6 x 10³ cells ml^–1, but was undetectablein summer. Free M.pusilla viruses were detectable in all seasons,with concentrations from 0.02 viruses ml^–1 to 1.9 x 10³viruses ml^–1, exceeding host abundances only in one case.We found a great intraspecific variability in host susceptibilityto viruses present in natural samples, with viral titres rangingover one or two orders of magnitude for the same samples incubatedon different M.pusilla strains. Over the winter–springperiods, a highly dynamic situation was evident, with wide fluctuationsfor both host and virus abundances from one week to another.In some cases, peak host concentrations were accompanied byan increase in viral numbers, whereas in other cases the respectivefluctuations were uncoupled. Although fluctuations of M.pusillaabundance could be influenced by viral infection, there wasno evidence that viruses were able to terminate host blooms.The summer decline of M.pusilla populations did not appear tobe related to the impact of viral infection.     

Larval fish variability in response to oceanographic features in a nearshore nursery area

The influence of oceanographic features on ichthyoplankton assemblages in the warm temperate nearshore region of Algoa Bay, South Africa, was assessed. The nearshore ichthyoplankton comprised 88 taxa from 34 families. Samples were collected at six stations between August 2010 and July 2012 using a plankton ring net of 750 mm diameter and 500 µm mesh aperture. The majority of larvae collected were in a preflexion stage, indicating the potential importance of the nearshore for newly hatched larvae. Engraulidae dominated the catch (38·4%), followed by Cynoglossidae (28·1%) and Sparidae (8·4%). Larval fish abundance was highest during austral spring and summer (September to February). Unique patterns in responses of each dominant fish species to oceanographic features in the nearshore indicate the sensitivity of the early developmental stage to environmental variables. Using generalized linear models, ichthyoplankton abundance responded positively to upwelling and when warm water plumes originating from an Agulhas Current meander entered Algoa Bay. Highest abundances of Engraulis encrasicolus and Sardinops sagax were observed during Agulhas Plume intrusions into Algoa Bay. When a mixed and stratified water column persisted in the nearshore region of Algoa Bay, larval fish abundance decreased. The nearshore region of Algoa Bay appears to serve as a favourable environment for the accumulation of ichthyoplankton.     

Locomotion in Amphibian Larvae (or "Why Aren't Tadpoles Built Like Fishes?")

SYNOPSIS. A variety of morphological features that affect locomotiondistinguish larvae of the three living amphibian orders fromfishes and their larvae. The oddest amphibian larvae are anurantadpoles. With their globose bodies, concealed forelimbs, abruptlycompressed and terminally tapered tails, tadpoles not only differradically from fishes but they—unlike caecilians or salamanders—alsodiffer radically from their adults. Tadpoles typically haveless axial musculature and much simpler myotomes than fishes.Surprisingly, in terms of mechanical (propeller) efficiencyand maximum sprint speeds, tadpoles still perform as well asmany teleosts of comparable sizes. From a consideration of hydromechanics,no amphibian larvae appear to be designed for sustained swimmingat high speeds. High maneuverability, rather than sustainablespeed, are important for amphibian larval survival.Two key featuresof tadpoles are the absence of caudal vertebrae and unexposedpectoral appendages. With only a notochord to serve as a skeleton,the tadpole tail is extremely flexible. Because of this exceptionalflexibility, tadpoles can fold their tails up against the bodyand turn rapidly with virtually no displacement of their centerof mass. Caudal flexibility can be regulated by muscle activityin the tadpole to effect turning. Lateral appendages are notneeded for this movement and are free to develop directly intotheir adult morphology; the anterior ones develop under coverof an opercular fold where they do not contribute to drag. Acase is presented, based on the ecology of metamorphosis, thatanuran transformation should be as brief as possible. With nobone to resorb, metamorphosis of the anuran caudal appendagecan, indeed, be very rapid.The basic kinematics of constantvelocity straightforward swimming for tadpoles and salamanderlarvae is reviewed, as well as the kinematics and electromyographyof starting, stopping, and turning in tadpoles. An attempt ismade to relate swimming kinematics to the characteristic morphologiesof amphibian larvae. Swimming speed in Rana, Bufo and Aynbystomalarvae, which swim only intermittently, is modulated by changingtail beat frequency. However, Xenopus, which swims constantlyby sculling with its tail, regulates swimming speed (at lowto intermediate velocities) by varying the length of the propulsivewave in its tail. Xenopus and Rana differ in the morphologyof their notochord, spinal cord, spinal nerves, and spinal motorpool distribution within the spinal cord. These differencesmay underlie the different way these larvae regulate swimming.They may also reflect their phylogenetic history.     

The importance of life-history stage and individual variation in the allorecognition system of a marine sponge

In marine invertebrates with complex life cycles, it may often be the case that trade-offs and behaviors differ between adult and larval stages. In this study, I examined the effects of life-history stage on allorecognition system function in the sponge, Haliclona sp. For sedentary marine invertebrates, allorecognition systems allow individuals to distinguish between genetically similar and distinct tissue they may encounter and are thought to reduce costly tissue fusion with individuals other than self or kin. Although it was found that sessile adults fused preferentially with self-tissue and exhibited a functioning allorecognition system, free-swimming larvae fused equally with sibling and non-sibling larvae resulting in swimming chimeras capable of successful metamorphosis, suggesting a stage-activated allorecognition system. In addition, adult sponges differed significantly in the propensity of their larvae to fuse suggesting variation in parental strategies. Analysis of larval swimming behavior indicated that larvae aggregate and are capable of increasing their encounters with other larvae and perhaps their probability of fusing in nature. The pursuit of fusion at this motile stage, along with evidence of a functioning adult allorecognition system, suggests that larvae may not express a recognition system, or that factors other than relatedness such as benefits to larval or adult chimeras, are involved in larval fusion and a stage-activated allorecognition system. In addition, this study demonstrates the presence of variation among individuals in the allorecognition system's ontogeny in the sponge Haliclona sp.     

A recurrent and localized dinoflagellate bloom in a Mediterranean beach

A recurrent, prolonged and singular bloom of Alexandrium tayloriBalech in an open beach (La Fosca, Spain, NW Mediterranean)is described. Alexandrium taylori appears at several placesalong a wide area of the NW Mediterranean (Costa Brava) duringthe summer, reaching concentrations up to 10⁵ cells l^–1,but it only proliferates persistently, massively (densities>10⁶ cells l^–1) and recurrently during August in LaFosca beach. The A.taylori bloom can be considered a manifestationof large-scale proliferation in a restricted area, where couplingbetween resting cysts in the sediment and bloom outbreak isnot a major factor compared to the interaction of local environmentalconditions with the planktonic organism's life history. Fromobservations of environmental conditions (the environmentalwindow) and the multiscale spatio-temporal distributions andlife history of A.taylori, we describe the bloom dynamics andanswer some critical questions about the different phases ofthe bloom. Some of these answers are: (i) the source of theA.taylori population is widespread offshore and is not locateddirectly at the beach; (ii) high cell densities are reachedand maintained with a moderate in situ growth and low loss rates;(iii) temporary cysts act as a reserve of the population.     

Abundance, frequency of dividing cells and growth rates of Synechococcus sp. (cyanobacteria) in the stratified Northwest Mediterranean Sea

The abundance, frequency of dividing cells and growth ratesof the planktonic cyano bacteria Synechococcus sp. during thesummer of 1995 and 1996 were estimated in the Northwest MediterraneanSea to test whether depth-dependent growth rates of this speciesexplain its dominance in the deep chlorophyll maximum (DCM)layer formed during summer thermal stratification in the NWMediterranean, compared to the surface layer. Abundance at theDCM layer (50–70 m) was up to two orders of magnitudegreater than that at the surface, with values ranging from 1.7to 13x10⁶ cells I-¹ and from 4 to 175 x 10⁶ cells I-¹ at thesurface and in DCM waters, respectively. Gross growth rates,however, were much higher at the surface than in the DCM layer(surface: 0.76–1.07 day DCM: 0.30–0.47 day-¹ Thehigher gross growth rates at the surface layer were supportedby a higher frequency of dividing cells (surface: 0.09–0.24;DCM: 0.01–0.12). The negative correlation between theabundance or standing stock and growth rates of these planktonicpicocyanobacteria points to losses, and not growth rate, asthe main control on the abundance of Synechococcus. Althoughwe provide some evidence that grazing alone may be able to accountfor these losses, further, direct determinations are clearlyneeded to elucidate the regulation of the abundance of Synechococcusin the NW Mediterranean.     

Seasonal abundance and distribution of Caridea larvae in Isafjord-deep, north-west Iceland

The abundance and distribution of Candea larvae was studiedin Ísafjord-deep, north-west Iceland, at approximatelymonthly intervals from February 1987 to February 1988 Zooplanktonsampling was made at nine stations along the length of the fjord,while temperature and chlorophyll a measurements from one ofthe stations are also presented Larvae of six species occurredin the samples, Eualus pusiolus and Pandalus borealis were mostnumerous, constituting 62 8 and 25 9% of the larvae respectively.The other species were, in declining order of abundance, Pandalusmontagui, Spirontocaris spp. (S spinus and s lilljeborgii) andSabinea septemcarinata. Eualus pusiolus was of highest abundancein the outer and middle parts of the fjord, while P.borealiswas most common in the middle and inner parts The onset of hatchingof all species in April–May appeared closely linked tothe phytoplankton spring bloom, while the temperature in thefjord was by then near the annual low (2–3°C). Exceptfor E pusiolus, of which a small part of the population produceda second brood during the summer, most of the larvae had disappearedfrom the plankton by the middle of August The monthly carapacegrowth of P.borealis larvae during the summer months was estimatedto be 1.0 mm.     

Composition and seasonality of nocturnal peracarid zooplankton from coastal New Hampshire (USA) waters, 1978-1980

Seasonal changes in the nocturnal peracarid zooplankton froma nearshore area of the Gulf of Maine were studied from January1978 through December 1980 as a requirement of an ecologicalmonitoring program for the Public Service Company of New Hampshire'sSeabrook Generating Stanon. Numerically dominant species includedthe mysids Michteimysis mixta and Neomysis americana. the amphipodsPontogeneia inermis, Themisto gaudichaudi and Monoculodes edwardsi.and the cumaceans Diastylis polita and Lamprops quadriplicata.A general seasonal cycle was documented with a more abundantand speciose assemblage during fall and winter than summer.Peak abundance occurred during spring months prior to emigrationof juvenile M.mixta from the study area. Abiotic and bioticfactors which may affect the structure and composition of thisassemblage are discussed.     

Embryonic development of verongid demosponges supports the independent acquisition of spongin skeletons as an alternative to the siliceous skeleton of sponges

Approximately 85% of extant sponges (phylum Porifera) belong to the class Demospongiae, which contains 14 taxonomic orders. In the orders Verongida, Dictyoceratida, and Dendroceratida, jointly referred to as 'keratose demosponges', the skeleton does not contain siliceous spicules but only spongin fibres. This shared trait has encouraged placement of these orders together within Demospongiae, although their relationships remain uncertain. The present study documents for the first time embryo development in the order Verongida ( Aplysina aerophoba ), providing some clues for phylogenetic inference. Spawned eggs were enveloped by a follicle of maternal cells. Embryos and larvae were chimeric organisms, the blastocoel of which was filled with symbionts and maternal cells migrated from the follicle. The ultrastructure of epithelial larval cells revealed: (1) a basal apparatus characterized by a peculiar, angling accessory centriole; (2) a pear-shaped nucleus with a protruding beak connected to the rootlets of the basal body; and (3) a distinctive Golgi apparatus encircling the nuclear apex. Developmental and ultrastructural findings support the concept, in congruence with recent molecular studies, that Verongida are more closely related to Halisarcida (askeletal sponges) and Chondrosida (askeletal sponges + sponges with spongin + spiculate sponges) than to the remaining 'keratose' orders, making a monophyletic 'supra-ordinal unit' equivalent to a subclass (Myxospongia, new subclass). Hence, spongin skeletons have evolved at least twice in Demospongiae. Independent acquisition of 'corneous' materials as an alternative to silica could have been stimulated by the radiation of diatoms at the Cretaceous–Tertiary boundary (approximately 65 Mya), which depleted silicon in the photic zone of the world's ocean.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 97 , 427–447.     

Seasonal and tidal abundance patterns of decapod crustacean larvae in a shallow inlet (SW Spain)

Planktonic larvae of decapod crustaceans were collected monthlyfrom July 1991 to June 1992 by pumping during nocturnal floodand ebb tides to establish seasonal larval abundance patternsin an inlet of the Bay of Cdiz. Additional 24 h series of sampleswere collected seasonally (July 1991, October 1991, January1992 and May/June 1992) during spring and neap tides to analyselarval abundance in relation to the main environmental cycles(diel, tidal and lunar phases) and vertical position in thewater column. First zoeae were the most abundant stage for mostspecies, representing 97.6% of all individuals collected. ZoeaI abundance was higher in spring and swmner and, on most samplingoccasions, there was a net output from the inlet to the bay.Five species (Liocarcinus arcuatus and Liocarcinus vernalis,Uca tangeri, Diogenes pugilator and Panopeus africanus) represented60% of total individuals caught. The seasonal occurrence offirst zoeae of the most abundant species indicated two differentreproductive patterns: species with a short reproductive periodand species spawning year round. Zoea I of several species (Panopeusafricanus, Uca tangeri, Pachygrap sus marmoratus, Processa spp.)were significantly more abundant during ebb tides and theirlater larval stages were scarcely collected, suggesting thatthese larvae are released in the inlet and exported to the bay.Conversely, a net input of first zoeae was observed for otherspecies (D.pugilator and Pinnotheres pinnotheres), but theirlater larval stages were also scarcely collected. Such importationcould be a larval rhythm artifact due to release of larvae inthe bay that drifted into the inlet by tidal currents. The crabIlia nucleus, whose later larval stages were collected frequently,was the only species that seemed to complete its life cyclewithin the bay. These results suggest that the studied inletwas primarily used by decapods as an adult habitat and spawningground, while larval development occurred in open sea. Sincevertical migration was not observed for exported larvae, thetidal synchronization of female release seemed to be the mostprobable mechanism of larval exportation. There were no significantdifferences between larval release during spring and neap tides.     

Genetic Diversity and Local Connectivity in the Mediterranean Red Gorgonian Coral after Mass Mortality Events

Estimating the patterns of connectivity in marine taxa with planktonic dispersive stages is a challenging but crucial task because of its conservation implications. The red gorgonian Paramuricea clavata is a habitat forming species, characterized by short larval dispersal and high reproductive output, but low recruitment. In the recent past, the species was impacted by mass mortality events caused by increased water temperatures in summer. In the present study, we used 9 microsatellites to investigate the genetic structure and connectivity in the highly threatened populations from the Ligurian Sea (NW Mediterranean). No evidence for a recent bottleneck neither decreased genetic diversity in sites impacted by mass mortality events were found. Significant IBD pattern and high global F_ST confirmed low larval dispersal capability in the red gorgonian. The maximum dispersal distance was estimated at 20–60 km. Larval exchange between sites separated by hundreds of meters and between different depths was detected at each site, supporting the hypothesis that deeper subpopulations unaffected by surface warming peaks may provide larvae for shallower ones, enabling recovery after climatically induced mortality events.     

Mechanisms of propagule release in the carnivorous sponge Asbestopluma occidentalis

Carnivorous sponges characteristically inhabit the deep sea, so extensive observations of the biology of living specimens are rare. We report on newly discovered shallow‐water (<30 m depth) populations of the carnivorous sponge Asbestopluma occidentalis and on observations of living adults and larvae from this unique group of sponges. In the Salish Sea, British Columbia, Canada, populations of A. occidentalis exist at depths as shallow as 18 m, where they co‐occur with hexactinellid sponges. Adults with and without embryos (n =127) were collected and easily maintained in the laboratory for several months, allowing continuous examination of live specimens. Parent sponges naturally disassociated their tissue, facilitating larval release and dispersal. Dispersed larvae had actively beating cilia, but no swimming was observed. Larvae settled and attached from several hours to several days post‐release. After larval release, parent sponges reaggregated their disassociated bodies into spherical balls of apparently undifferentiated tissue, which could also disperse and settle. Sexually mature adults were sampled in the field from August to November, with a high proportion of adults containing mature embryos in late November. High‐resolution photography and electron microscopy verified that adults were covered with anisochelae spicules, and used these to capture nauplii of Artemia sp. under experimental conditions; however, time‐lapse photography showed that some captured prey could free themselves with vigorous swimming. The occurrence of abundant shallow‐water populations of A. occidentalis in the Salish Sea provides a rare opportunity to study the evolution and ecology of carnivory in the Porifera.