Vesicomyid clam species are abundant in many deep-sea chemosynthetic communities, including cold seeps. They rely primarily on thiotrophic (sulphide-oxidizing) gill symbionts for nutrition and thus require sulphide-rich environments. Submersible surveys of megafaunal distributions at the Blake Ridge Diapir, a deep-sea methane-hydrate seep located ∼200 miles off the coast of Charleston, South Carolina, documented massive mortalities of vesicomyid clams. The cause of these mortalities is unknown, but sulphide deprivation, sulphide toxicity, and disease are possible agents of mortality in this system. Similar redox profiles in sediment cores from live and dead clam beds do not support the hypothesis that there has been a transient shift in the flux of sulphide. To address the potential for disease as a cause of mortality, we undertook a histological survey of microparasites and other indications of disease in clam tissues. Six morphological types of parasites were identified using light microscopy, including two viral-like inclusions, Rickettsia-like gill inclusions, possible bacterial gut inclusions, bacterial gill infections, and a protistan inclusion. Of these parasites, two were pathogenic: viral-like inclusions in mantle tissues caused tissue degradation; bacterial gill infections resulted in localized disruption and degradation of gill filaments. Infection prevalence and densities were low for all parasites observed. The majority of clams examined showed intense haemocytic responses in the absence of any obvious etiologic agent, suggesting the presence of parasites not detectable by our methods. Our findings indicate that the clam population at the Blake Ridge seep was in relatively good health at the time of sampling.

Crepipatella fecunda is a benthic, primarily suspension-feeding gastropod that occurs in great abundance along the Chilean coast. It is a protandrous species whose reproduction involves brooding of an encapsulated embryonic stage followed by the release of free-living planktotrophic larvae. Because its close sister species, C. dilatata, co-occurs with C. fecunda, understanding the details of reproduction in this species might shed light on differences in reproductive features that correlate with divergences in mode of development. In southern Chile, brooding occurs throughout the year except for May and June, and each female produces 3–7 broods. The smallest brooding female was 28·2 mm in shell length and the largest was 56·3 mm. All full-grown eggs from the ovary are deposited at one time in a single brood, and only smaller oocytes remain in the gonad after the female finishes ovopositing. Those females that host pinnotherid crabs do not deposit eggs. All the eggs develop into embryos whose intracapsular development is similar to Crepidula fornicata and Crepipatella lingulata. Planktotrophic larvae hatch at a mean shell length of 329·5 μm (SD=27·09) after 4–5 weeks. During the pelagic stage the shell and velum of the larvae grow, but little other morphological development is visible externally. The pelagic stage lasts for 15–16 days at 17°C, during which the larvae grow ∼20·7 μm d−1. Observations of cultured larvae and protoconchs of field-collected juveniles show that settlement occurs when the larvae reach a shell-length of 650 μm (SD=28·3 μm).

Life cycle, population dynamics and productivity of the larviparous mudsnail species Ventrosia maritima were investigated at low salinities (0·3–6 psu) in differentiated parts of a Mediterranean lagoon (Monolimni Lagoon). Monthly samples were collected during the period from February 1998 to February 1999 in both parts of the lagoon. Ventrosia maritima displayed an annual life cycle. Recruitment occurred in summer and autumn at the outer part of the lagoon and additionally in late winter at the innermost part. A positive correlation was found between the percentages of small individuals and salinity or sediment organic matter at the outer part. Growth practically ceased in winter. The mudsnail displayed remarkable densities and an increase in growth in spring at <1 psu indicating that it is highly tolerant to extremely low salinities. Population density showed a significant seasonal variation; it increased from early summer to autumn (30,000–40,000 individuals m−2) following the summer and autumn recruitment. No significant correlation between the density of V. maritima and several examined physicochemical variables was found; a negative correlation was observed between the density of the mudsnail and that of the co-occurring polychaete Streblospio shrubsolii. Secondary production calculated by the size–frequency method gave a mean annual density (N) of 9740 ind m−2, a mean biomass (B) of 1·66 g ash-free dry weight (AFDW) m−2 y−1, a production (P) of 4·51 g m−2 y−1 and a P:B ratio of 2·72 at the outer part of the lagoon and a N of 14,570 ind m−2, a B of 3·2 g AFDW m−2 y−1, a P of 9·9 g m−2 y−1 and a P:B ratio of 3·09 at the innermost part. At the innermost part of the lagoon, where the seawater renewal rate and hydro-dynamism were lower and the sediment finer and organically richer, V. maritima displayed more recruitment pulses, a larger body size and a denser and more productive population than the one at the outer part. Our findings are compared to published data for the direct-developing congeners V. ventrosa and V. truncata.

Reproductive phenology among temperate hermit crabs, reproductive seasons of nine sympatric species and some reproductive characteristics of four Pagurus species were investigated in Tosa Bay, southern Shikoku, Japan. Females of P. filholi, P. maculosus, P. minutus and P. nigrivittatus had clutches mainly in winter and were found to breed multiple clutches within each reproductive season while four Diogenidae species and P. japonicus mainly reproduced in summer, suggesting that interspecific variation in reproductive phenology of temperate hermit crabs might be determined by allopatric adaptation with phylogenic constraints. There was interspecific variation in the length of reproductive seasons among the four Pagurus species and the variation was considered to reflect the interspecific difference in the number of clutches per reproductive season, not in the ovigerous period per clutch. The length of reproductive seasons among the four species seemed to relate to maturity size and/or interspecific differences in thermal adaptation.

the taxonomy of the genus centrophorus (squaliformes: squalidae) is currently in a great deal of uncertainty. the characteristics of the species subject to the present study most closely resemble those of centrophorus uyato, hence the use of centrophorus cf. uyato, though the species in question may be a species of centrophorus that has not been described previously. specimens were obtained via vertical and horizontal longline at depths of 250–913 m. the reproductive biology of 51 female and 8 male centrophorus cf. uyato were examined. this species is sexually dimorphic, with females attaining a larger size than males. the smallest mature male was 81.2 cm total length whereas the smallest mature female was 91.5 cm total length. females are aplacentally viviparous, with the pups acquiring nutrition via large external yolk sacs, and there was a maximum of two pups per litter. oocytes continued to develop throughout gestation. most females carrying developing embryos had two large (>3.3 cm), equally developed ovarian oocytes, which leads us to believe that they ovulate soon after parturition. this species seems to exhibit complete sexual segregation during the non-breeding season, with mature males absent from the study site during summer months. centrophorus cf. uyato may have one of the lowest fecundities among sharks, giving birth to a maximum of two pups every three years. all species in genus centrophorus have small litters (<6) making them vulnerable to over-exploitation.

This brief review discusses the different ways in which the study of gelatinous plankton has contributed to an understanding of the physiology and evolutionary relationships of other animals.

Embryos of Crepidula dilatata develop within egg capsules where they feed on nutritive eggs also deposited within the capsules. Nutritive eggs permit the embryos to develop to a juvenile stage at hatching without passing through a pelagic larval phase. The juveniles enter the local population in posession of a well developed radula and gill filaments covered by lateral, ventral, and dorsal cilia. Initial feeding by the juveniles, employing both the radula and the gill, occurs from the first day of release from the capsule. The radular band of recently hatched snails is functional from the first day in the benthos, and is used for grazing the substrate, driving the mucus cord from the neck-canal to the mouth, and also for extracting mucus balls produced in the food pouch. The gill is active in particle collection from the first day of the free living juvenile, and is noted by the presence of well developed dorsal and ventral ciliature, active in moving mucus and particles over the gill lamellae to form the mucus string at the extreme ends of the gill filaments. The food pouch becomes active two to three days after initiation of production of mucus cords. All the functions associated with feeding, such as the numbers of mucus cords, radular strokes, and mucus balls increase in activity with progressive development of the juveniles.

The mole crab Emerita talpoida occurs in the swash zone of sandy beaches. Although crabs move with the tide, field studies found that the smaller crabs are distributed higher intertidally than the larger crabs. The present study tested the hypothesis that the rhythm, timing of activity, and activity amplitude with respect to tides would be different among megalopae, juveniles, small females, small males, mature males and large ovigerous females and underlie the observed field distributions. Activity of individuals in columns was observed under constant conditions with a video system and quantified as the number of ascents from the sand each 0·5 h. All life history stages had a circatidal rhythm in vertical swimming with median free running period lengths near 12·4 h and activity peaks after the time of high tide. Period length and time of activity peaks did not differ significantly among the life history stages. Activity amplitude was related to tidal amplitude of consecutive high tides at the collection site. Larger crabs had greatest activity after the lower amplitude high tides whereas small crabs had equal activity amplitude on consecutive tides. The test hypothesis was partially supported because the difference in activity amplitude predicts an oscillation between overlapping distributions of small and large crabs after low amplitude high tides, with the smaller crabs distributed higher on the beach after high amplitude high tides. The rhythm was not affected by a light:dark cycle and could be entrained by mechanical agitation.

In the pelagic habitat, the bodies of resident animals provide much of the ecological substrate available for other organisms to attach, find shelter, and seek food. In Monterey Bay, California, the doliolid Doliolula equus provides substrate for multiple symbionts. These include a mutualist hydroid, commensal ciliates, and a parasitic amphipod. This new doliolid is described based on in situ observations from a remotely operated vehicle, and from the laboratory examinations of 43 colonies comprising hundreds of living, individual blastozooids. Doliolula equus differs from other members of the suborder Doliopsidina in the shape of its body, the length and configuration of its third muscle band, the size of its buccal siphon, and the position of the spiral gland. The new doliolid was found principally at depths between 300 and 400 m. This species is bioluminescent, hermaphroditic, and about one zooid in ten is peppered with orange pigment spots. A variety of other, obviously related, yet undescribed forms has been observed in the eastern Pacific.

An optimized method, using polyclonal antibodies in an immunoassay, for prey detection in the diet of paralarvae of South African Loligo reynaudii is described. The study has increased the specificity of the antisera by determining the optimum antiserum dilutions and the detection limits of the antisera. Unfed laboratory-hatched paralarvae (negative control) were exposed to antisera and showed cross-reactions with polychaete antiserum.

The animal communities associated with the deep-sea reducing environment have been studied for almost 30 years, but until now only a single species of ophiuroid, Ophioctenella acies, has been found at both hydrothermal vents and methane cold seeps. Since the faunal overlap between vent and seep communities is small and many endemic species have been found among other taxa (e.g. Mollusca, Crustacea), additional species of ophiuroids were expected at previously unstudied sites. Chemical compositions at reducing sites differ greatly from the nearby bathyal environment. Generally, species adapted to chemosynthetic environments are not found in non-chemosynthetic habitats, but occasional visitors of other bathyal species to vent and seep sites have been recorded among many taxa except ophiuroids. This paper presents an analysis of the ophiuroid fauna found at hydrothermal vents and non-reducing nearby sites on the Mid-Atlantic Ridge and on methane cold seeps in the Gulf of Mexico, at Blake Ridge off South Carolina and south of Barbados. In addition to O. acies, four species were found at vents, Ophiactis tyleri sp. nov., Ophiocten centobi, Ophiomitra spinea and Ophiotreta valenciennesi rufescens. While Ophioctenella acies appears to be restricted to chemosynthetic areas, the other four species were also found in other bathyal habitats. They also occur in low numbers (mostly single individuals), whereas species adapted to hydrothermal areas typically occur in large numbers. Ophioscolex tripapillatus sp. nov. and Ophiophyllum atlanticum sp. nov. are described from nearby non-chemosynthetic sites. In a cold seep south of Barbados, three species of ophiuroids were found, including Ophioctenella acies, Amphiura sp., Ophiacantha longispina sp. nov. and Ophioplinthaca chelys. From the cold seeps at Blake Ridge and the Gulf of Mexico, Ophienigma spinilimbatum gen. et sp. nov. is described, likely restricted to the reducing environment. Ophiotreta valenciennesi rufescens occurred abundantly among Lophelia corals in the Gulf of Mexico seeps, which is the first record of this species from the West Atlantic. Habitat descriptions complement the taxonomic considerations, and the distribution of the animals in reducing environments is discussed.

the population structure and reproductive biology of mustelus schmitti was analysed during autumn (1994, 1995) and spring (1994) in the rio de la plata oceanic front. the samples consisted mainly of adult males and immature females, indicating that nursery areas are situated elsewhere. in autumn, the highest female densities occurred between 36°s and 35°s, with densities decreasing further south, and high male densities occurred over all latitudes of the study area. in spring, both sexes occurred north of latitude 36°30′s. males attained maturity at 59 cm total length (tl), and females at 72 cm tl. litter size varied from one to ten in spring and two to nine in autumn, with embryos ranging from 9 to 26 cm and 7 to 26 cm tl respectively. the mean tl of embryos was significantly higher in spring (22 cm), suggesting that parturition occurs in late spring and summer. litter size was found to increase with female tl.

Adult Polinices pulchellus were collected from the field and held in aquaria under ambient conditions. Egg collars laid by P. pulchellus were cultured at 14°C and 20°C and larval development after hatching was documented photographically. Planktotrophic Polinices pulchellus veligers hatched from egg collars cultured at 20°C after nine to ten days and after 14 to 15 days at 14°C. Veligers spent most of their time close to the water surface and began feeding within one hour of hatching. Repeated attempts to raise larvae to metamorphic competency at 14°C were unsuccessful. Morphological changes, most notably in the colour and size of the velum and foot, were observed in larvae raised at 20°C. During the first 25 days of larval development the velum broadened and bifurcated into four velar arms, the distal regions of which acquired a deep red coloration. By day 40 the foot had increased considerably in size and the degree of black pigmentation. By day 45 pediveligers were competent to metamorphose to the juvenile stage. Exposure to sediment from the adult habitat induced metamorphosis, larvae lost their vela and became benthic juveniles. Within three days of metamorphosis, juvenile snails drilled the bivalve Lasaea adansoni (∼2 mm), later drilled Cerastoderma edule (∼4 mm), and displayed cannibalistic behaviour. Larvae survived for ∼6 months in the absence of a suitable settlement cue.

Larvae of Ibla cumingi from Daya Bay, China were cultured in the laboratory. Larval development includes six naupliar stages and a non-feeding cypris stage following the ground patterns of cirripeds. Larvae reached the cypris stage in nine days at ∼25°C after hatching. Morphological features including the cephalic shield, frontal horns, labrum, abdominal process, antennules, antennae and mandibles in all nauplii were described and illustrated using light microscopy. A full morphological description of cyprid larvae was provided using scanning electron microscopy. Attempts were made to compare the difference between the larval development model of I. cumingi and that of Ibla species.

The development and growth of a feather star Decametra tigrina from Notojima Island, Japan, is reported. This is the first record describing the complete development, from early embryos to juveniles, in the family Colobometridae. Their larval development was observed to progress independently from the adults, and was similar to other feather star species. Embryos hatched as uniformly ciliated gastrulae, which turned into doliolaria larvae when four narrow circumferential ciliated bands were formed. Skeletal ossicles began to form inside the doliolaria larvae, which subsequently settled to the substrate, proceeding to the cystidean stage. The protrusion of the arms from the oral opening marked the beginning of the pentacrinoid stage. About 45 days after hatching, they autotomized their stalks and became juvenile comatulids with arms about 6 mm long. These early juveniles apparently differ from the adults in morphological characters, such as having no pairs of tubercles or spines on the dorsal of their cirrals, and no proximal pinnules except for the first pinnule (P1). Both features are prominent in adults and are used for the classification of D. tigrina. Morphological differences between juveniles and the adults may also occur in other feather star species. A revision of the classification of comatulids, which considers morphological changes with growth, is required.

Three new species of Fritillaria are described from specimens collected by a remotely operated vehicle (ROV) between 180 and 735 m depth in Monterey Bay, California. Fritillaria rex becomes the largest species now described for this genus (trunk length up to 10 mm, tail length up to 18 mm). This species is characterized by five or six narrow muscle bundles on each side of the tail, slit-shaped spiracles, a spherical ovary and a cylindrical testis. Fritillaria amphigonadis (trunk length up to 5.2 mm, tail length up to 7.5 mm) is characterized by two narrow muscle bundles on each side of the tail, slit-shaped spiracles, paired spherical ovaries, and a unique pi-shaped testis. Fritillaria lucifer (trunk length up to 4.1 mm, tail length up to 7.0 mm) has 12 extremely thin muscle bundles distributed broadly across the tail, rounded spiracles, a spherical ovary and a U-shaped testis. An additional mesopelagic Fritillaria appears to be consistent with the description of the Mediterranean F. fage, but specific differences in pharyngeal cells, cellular patterns on the tail, and gonadal morphology suggest that the specimens from Monterey Bay are a new variety, F. fagei mbarii. Based on the relatively limited number of collections (i.e. only 20 specimens yielding four unique taxa), it would appear that the possible diversity of larvaceans that live below the surface mixed layer is significantly underestimated.

tagged with an electronic data storage tag on 6 october 1999 in the thames estuary (uk), a thornback ray, raja clavata, was recaptured after 504 days at liberty, 276 km north-west of release. the tag recorded 423 days of data. the migration was reconstructed using the tidal location method, and illustrates seasonal migration out of the thames estuary to the central southern north sea during autumn and winter, then a return to the thames to spawn during spring. this is the first direct evidence of repeated seasonal migration outside the area commonly thought of as the species home range, an observation with significant implications regarding the applicability of closure management as a conservation measure for this species.

The solitary ascidian Styela clava is recorded for the first time in Portuguese waters. It was found at three sites on the west coast of Portugal. This represents the southern limit of its recorded distribution in European waters. The Portuguese specimens are described and compared with UK specimens.

Repopulation by green sea urchins Strongylocentrotus droebachiensis of a steeply sloping rock bottom was monitored at a wave-exposed headland (Chebucto Head) following a disease outbreak that caused mass mortality in September 1999. Density and size of urchins were sampled in four depth strata: at 8–10 m in an urchin grazing aggregation (front) along the lower margin of a kelp bed, at 12 m and 16 m on a bedrock ramp, and at 24 m on a cobble and boulder field where urchins were unaffected by the disease. Shoreward migration of adults along the ramp from the surviving population at 24 m was the primary means of repopulation, which was augmented by recruitment via planktonic larvae. At 16 m, urchin density stabilized (at ∼50 urchins m−2) within six months of the die-off while repopulation at 12 m took more than eight months. A grazing front of large urchins (40–60 mm, test diameter) had formed along the lower edge of a kelp bed by January 2002, which reached densities of up to 284 urchins m−2. Video surveys at Chebucto Head and two adjacent locations of similar bathymetry revealed an extensive urchin population between 25 and 55 m depth, with a mean density on rocky substrata of 73 urchins m−2.

Published behavioural, DNA sequence, and morphologic data on six populations of Mastigias, five from marine lakes and one from the lagoon, in Palau are summarized. Each marine lake population is distinguished from the lagoon population and from other lake populations by an unique suite of characteristics. Morphological differences among Mastigias populations in Palau are greater than those recorded between any previously described species of Mastigias, whereas molecular differences are far less (≤2.2% in COI and ITS1) than those found between medusae identified in the field as Mastigias papua (>6% in COI and ITS1). Thus, each marine lake population in Palau is described as a new subspecies of Mastigias cf. papua: remengesaui (in Uet era Ongael), nakamurai (in Goby Lake), etpisoni (in Ongeim'l Tketau), saliii (in Clear Lake), and remeliiki (in Uet era Ngermeuangel).