Results from recent biological studies (including three Alvin dives in July 1997) of the southernmost deep-sea hydrothermal area known on the Mid-Atlantic Ridge (MAR), the Logatchev hydrothermal area, are described. The Logatchev area includes three vent fields, each with a different geological setting corresponding to: (1) a large sulphide mound with ‘smoking craters’; (2) an active chimney complex (known as ‘Irina-2’); and (3) a diffuse flow through soft sediment (‘Anya's Garden’). Hydrothermal communities found at these fields differ considerably: Anya's Garden is dominated by vesicomyid clams, Ectenagena sp. aff. kaikoi, Irina-2 by mytilid mussels, Bathymodiolus sp. aff. puteoserpentis, with swarms of shrimps and other rich associated fauna, whereas on the main mound the fauna as a whole is less abundant and less diverse. This is the first record of a living clam population on the MAR. Other bivalves found on the clam field included thyasirids, Thyasira (Parathyasira) spp., not reported previously from deep-sea hot vent communities. The biomass on the mussel bed at Irina-2 exceeds 70 kg m−2 (wet weight with shells) and is the highest known on the MAR. The large shrimp population at Irina-2 includes swarms of Rimicaris exoculata. A diverse shrimp fauna (including a new species Alvinocaris sp. aff. muricola) on the mussel bed is dominated by Mirocaris keldyshi. Overall the Logatchev area is dominated by mussels which may be attributable to the presence of both methane-oxidizing (dominant type) and sulphur-oxidizing bacterial symbionts in their gills. The diversity of vent organisms and biotopes at Logatchev appears to be the highest on the MAR.

Biomass measurements (AFDW) of both subtidal and intertidal macrofauna of the ‘Abra de Bilbao’ embayment were used within a pilot study in a four step strategy of analysis, which consisted of: (1) representing communities; (2) discriminating sites or conditions; (3) determining levels of ‘stress’; and (4) linking to environmental variables. Univariate (number of species, diversity indices) as well as multivariate (clustering, MDS, SIMPER, BIO-ENV) techniques from the PRIMER package were employed. Several data aggregation levels were proposed in the analyses with the aim of selecting cost-effective procedures. The results suggested a good integration of environmental conditions by subtidal samples, which were close to constant on all different taxonomic aggregation levels. The abiotic parameter which best ‘explained’ the biotic pattern of subtidal samples in the investigated area was turbidity measured as total suspension solids and nephelometric units on the water surface. In conclusion, we recommend monitoring rocky substrates by using more extensive biomass sampling surveys of subtidal areas followed by a less time-consuming treatment of the samples (identification by high taxonomic categories or by trophic groups).

Protozoan communities at three beaches on the Cantabrian Sea were studied. Four stations along a transect of 150 m at each beach were chosen for this study. The following parameters were measured: temperature, pH, oxidation–reduction potential, dissolved oxygen, conductivity, salinity, nitrate, phosphate, granulometry and amount of organic matter. Four groups of protozoa (ciliates, non-dinoflagellate flagellates, dinoflagellates and sarcodines) were analysed for their abundance and diversity, as well as the influence of the measured parameters on the communities. Temperature, pH, and dissolved oxygen were the main factors responsible for seasonal differences. Temperature increased at the beginning of spring and summer, coinciding with growth of the protozoan community. Flagellates and dinoflagellates increased during spring and early summer. The amount of organic matter subsequently rose. The final step of this succession was the development of the ciliate community. A comparison between the same areas in 1989 and in the present study was carried out.

In work performed during the period February–October 1996, about 47 species of ciliates were detected in the communities of Aufwuchs, or periphyton, colonizing glass substrates submerged in three sites in the Lagoon of Venice, two in the urban area of Chioggia and one at a mussel-farming site. The ciliate communities were composed of sessile forms of Peritrichia and Suctoria and of motile ciliates, belonging especially to Hypotrichia and Karyorelictea. Four species of the peritrich Zoothamnium and the suctorians Acineta tuberosa and Ephelota gemmipara are reported here for the first time in the Lagoon of Venice. The richest ciliate communities were recovered at 60 cm from the bottom. Processed by multivariate analysis, data of samplings performed up to day ten from the positioning of glass slides indicated significant differences in biotic and physico-chemical parameters, according to season. The first data did not give definite indications on the possibility of using ciliates colonizing solid surfaces to assess the quality of this peculiar environment.

Investigations were made on spatial and temporal variation, population structure, growth, recruitment and mortality in the intertidal flats of Kunsan (Korea, Yellow Sea) of an inarticulate brachiopod Lingula unguis. Statistical analysis indicates significant spatial differences and a significant relationship between density and ratio of sands to silts, suggesting that the distribution and density of this species were related to particle size. The population consisted of three year-classes, with a similar size composition each year, of which the second year-class was a major component. From estimation of parameters of growth monthly length–frequency was analysed by ELEFAN. Parameters of growth were estimated, using the modified von Bertalanffy growth function (VBGF) model incorporating seasonal variation in growth. The growth parameters are: L∞=44.00 mm SL, K=0.88 y−1, C=0.90, WP=0.48. The recruitment pattern shows two major recruitments per year. The maximum life span is estimated as 3.45 y. Total mortality (Z) by length-converted catch curve was estimated at 3.65 y−1. The population mainly occurred in fine sands and exhibited patchy distribution.

Populations of Caryophyllia smithii were studied at three sites of differing sedimentation regime in Lough Hyne, Ireland. The height, length, width and density of individuals were measured along with the depth of accumulated sediment on the rock substratum at each site. Calyx size was largest at the site of least sedimentation and smallest at the site of most sedimentation. In contrast, height of individuals was greatest at the site of most sedimentation and smallest at the site of least sedimentation. The height of individuals was correlated with the level of surrounding sediment (Pearson's correlation 0.836 P<0.05). The uppermost limit of C. smithii corresponded with the downward limit of the infralittoral zone at each site; 15, 13, and 12 m at the low, mid and highly sedimented site respectively. Density averaged over depth was greatest (70 ind m−2) at the site of moderate sedimentation and lowest (13 ind m−2) at the site of least sedimentation. Density was also found to increase with depth at the sites of moderate and high sedimentation.

A total of 11 polydorid species of the family Spionidae were extracted from non-calcareous substrata from Japan. The polydorids were: one Polydora sp., Polydora cornuta; three Dipolydora spp., Dipolydora quadrilobata, D. cardalia, D. socialis; one Carazziella sp., Carazziella spongilla; one Boccardiella sp., Boccardiella hamata; two Boccardia spp., Boccardia perata, B. proboscidea; three Pseudopolydora spp., Pseudopolydora cf. kempi, P. antennata, P. paucibranchiata. All inhabited mud deposits including mud in crevices of calcareous substrata, sponge and sandstone rocks, and were never found in self-excavated burrows in calcareous substrata. This study attempts to summarize and discuss the taxonomic, morphological, and behavioural characteristics of these non-boring species inhabiting Japanese waters and to compare them with the previously known boring species. The 11 non-boring species belonged to six genera. Thus their taxonomic and morphological variability was higher than those of boring species, which belonged only to three genera. A generic overview suggests that some genera contain many species capable of boring and others contain many species incapable of boring. Branchial blood vessels were thick and conspicuous in non-boring species. Moreover, they showed high crawling activity and a strong, vigorous palp movement. These observations suggest a possible link between boring activity and the morphology and behaviour in polydorids. In addition, Polydora cornuta, Dipolydora quadrilobata, D. cardalia, D. socialis, Boccardia perata and Pseudopolydora cf. kempi are new to Japan.

Larval development of Capitulum mitella (Cirripedia: Pedunculata) comprises six nauplius stages and a cyprid. Unilobed labrum, a larval trait of pedunculate and chthamalid barnacles, bears two groups of slender hairs and two pairs of strong teeth on the distal labral margin, and a pair of teeth on the lateral labral margin. Frontolateral horns extended under the anterior cephalic shield margin are diagnostic features through all nauplius stages. The posterior border of the cephalic shield bears a pair of distal cephalic shield spines in nauplius stages II and III, and a pair of long posterior shield spines in nauplius stages IV, V and VI. A hispid seta is consistently found at the fourth group of the antennal endopodite through stages II–VI. The dorsal thoracic spine, abdominal process and the paired posterior shield spines have numerous small spines. Morphological features such as the cephalic shield, labrum, abdominal process, antennules, antennae and mandibles in all nauplius and cyprid stages are illustrated and described. In this species, the numerical setations of the antennule are found to be beneficial for intra-specific identification of barnacle nauplius stages without the need for dissection.

The present work provides a first description of three planktonic larval stages of Chorismus tuberculatus which were obtained from plankton samples collected in the south-western Atlantic during the expeditions of the RVs ‘Walther Herwig’ and ‘Shinkai Maru’ in 1978 and 1979, respectively. Three early developmental stages of C. tuberculatus are described and compared with those of the second species of this genus, C. antarcticus which is known to be distributed in the southern Atlantic Ocean and Antarctica. Both species are distinguishable by the presence/absence of supraorbital spines at the carapace, an anal spine and the exopodite on pereiopod 4. The rostrum is less developed in C. tuberculatus, the shape of the somites is less pronounced, and the number of posterior spines at the telson is lower than in C. antarcticus. Due to an abbreviated larval development as a physiological adaptation to it wider distribution into the Polar region, we assume C. antarcticus to have phylogenetically separated from C. tuberculatus, represented by the well developed first larval stages in contrast to that of the species described herein.

The caridean shrimp Rimicaris exoculata, Chorocaris chacei and Mirocaris fortunata, together with bathymodiolid mussels, dominate the vent fauna along the Mid-Atlantic Ridge. Vent shrimp show the characteristic reproductive patterns of caridean decapods. The gonads are paired organs overlying the digestive gland under the carapace. In the ovaries, the oogonia (∼20-30 μm diameter) proliferate in the germinal epithelium at the periphery of the gonad, developing into previtellogenic oocytes. The previtellogenic oocytes grow to 70-100 μm before undergoing vitellogenesis. The maximum size for mature oocytes ranged between 200 and 500 μm depending on the species and the sample. The oocyte size–frequency data show no evidence of synchrony in oogenesis at population level for any of the species studied. Mirocaris fortunata is the only species where gravid females are commonly collected. The brood is carried on the pleopods, and the number of eggs per female ranges from 25 to 503, with a mean egg length of 0.79±0.14 mm. There is a positive correlation between fecundity and body size, characteristic of crustaceans. One ovigerous C. chacei and two R.exoculata have been studied. The former was carrying 2510 eggs and the later 988 small eggs in an early stage of development. The fecundity of M. fortunata, C. chacei and R. exoculata is significantly higher than that of species from the Acanthephyra group collected in the north-east Atlantic.

Five species of bresilioid shrimp were investigated at seven hydrothermal sites on the Mid-Atlantic Ridge: Menez Gwen, Lucky Strike, Rainbow, Broken Spur, TAG, Snake Pit and Logatchev. Samples were prepared for analysis of stable isotopes, elemental composition and lipids. Shrimp behaviour was observed from the submersible ‘Alvin’ and in the laboratory aboard RV ‘Atlantis’. The distribution and zonation of the shrimp species was recorded. Juvenile shrimp of all species arrive at the vents carrying reserves of photosynthetic origin, built-up in the pelagic larval stages. These reserves are used while the shrimp metamorphose to the adult form and, in Rimicaris exoculata and Chorocaris chacei, while they develop epibiotic bacteria supporting structures, the modified mouthparts and the inside of the carapace. The main food of adult R. exoculata is filamentous bacteria that grow on these structures. The intermediate sizes of C. chacei also feed on such bacteria, but the final stage gets some food by scavenging or predation. Mirocaris species scavenge diverse sources; they are not trophically dependent on either R. exoculata or mussels. Adults of Alvinocaris markensis are predators of other vent animals, including R. exoculata. The dense swarms of R. exoculata, with their exosymbionts, can be compared to endosymbiont-containing animals such as Bathymodiolus and the vestimentiferan tube-worms of the Pacific vents. Such associations, whether endo- or ectosymbiotic, may be necessary for the development of flourishing communities at hydrothermal vents.

The movement of juvenile Iceland scallops, Chlamys islandica, was quantified in an inshore bed in the Mingan Islands, northern Gulf of St Lawrence, to examine whether the size partitioning over depth in this location, increasing scallop size with depth, results from a gradual downslope movement as scallops increase in size. Scallops of 30.0-44.9 mm and 45.0-59.9 mm in shell height were collected using SCUBA, tagged, and released in the centre of two 0.4-km2 grids at 15 m in depth. After 7 d and 48 d, the net distance moved by the scallops from the release points did not vary between the two size groups but varied significantly between grids. The majority of scallops (70-94%) moved downslope and the mean movement vectors were not orientated in the direction of tidal currents, but rather towards increasing depth. The downslope movement of the scallops was possibly explained by more prolonged swimming bouts when scallops swam downslope. The results suggest that the spatial size partitioning of Iceland scallops at this location is caused by a gradual downslope movement as the scallops increase in size. This study provides the first experimental evidence supporting the controversial hypothesis of recruitment into adult scallop populations involving swimming of juveniles from nursery areas.

Early life growth of the short-finned squid, Illex illecebrosus (Mollusca: Cephalopoda), was reconstructed from periodic increments deposited on the gladius structure of squid collected in the Gulf Stream/Slope Water front and the Scotian Shelf. The general effects of environmental changes and lifestyle transitions in the variation of size-specific gladius growth was investigated. The offshore growth was exponential and at least six size-specific growth phases were distinguished. Paralarval growth ended at approximately 10 mm gladius length (GL). An important change in growth at 30–40 mm GL was associated with the shift from the macroplanktonic to micronektonic habitats and the transition from the Gulf Stream to Slope Water. The approximation to the Scotian Shelf/Slope Water Front was suggested as related to a growth transition at 68 mm GL. A change to linear growth occurred after the nektonic lifestyle was attained on shelf waters (90 mm GL).

The ascidian Corella inflata (Chordata, Ascidiacea) is common in many areas of Puget Sound, Washington, USA. However, it occurs only in habitats where it is protected from direct sunlight. Previous experiments with artificial lights showed that UV irradiation kills all life stages of this animal. The effects of natural sunlight exposure (measuring survival of adults, juveniles, larvae, and embryos) were compared. We partitioned the light spectrum to separate the effects of UVB, UVA, and visible light (PAR). Natural sunlight severely damaged C. inflata. Adults and juveniles died after 2-5 d. Exposed embryos failed to develop normally and larvae did not settle. As expected, UVB had significant effects, but pronounced effects were also seen when the animals were exposed to longer wavelengths alone (UVA and PAR). Thus, the distribution of C. inflata may be determined largely by exposure to light. Understanding the basic ecology of this species requires consideration of its vulnerability to sunlight damage and the effects of UVB, UVA, and PAR.

This note examines the way the pharyngeal feeding filter is constructed within the salp endostyle. Three salp species (Pegea confoederata, Thalia democratica and Salpa fusiformis) have been examined: results from each are essentially similar. The endostyle is a deep ventral groove in the pharynx, divided by a line of long basal cilia. These are flanked by gland cells which secrete the ‘mucus” which forms one of the sets of filaments of the filter. Beside the openings of this basal row of gland cells (marked by bumps of curious ‘mucus’ rodlets), there is a fence of two adjacent rows of cilia. The first of these two rows, (nearest the basal mid-line), whose tips lie next to the rodlet bumps, are regularly spaced 1.0 μm apart along the endostyle, whilst the cilia of the second row are at around half this spacing. Passing upwards in the endostylar groove, this first ciliary fence is followed by a ciliated zone, and then a second row of glandular cells is linked to a second ciliary fence with a single row of cilia only.

Filaments derived from the first set of gland cells pass obliquely over the ciliated zone, and continue over the second ciliary fence. The cilia of the second fence are often surrounded by very striking borders or curtains of rodlets which appear to dissolve, run down the cilia and pass off the tips as filaments, when they are joined by the first set of filaments to form a net with an elongate rhomboidal mesh. As this passes upwards, the mesh changes to become more or less square by the time it comes to overlie a striking asymmetrical band of cilia arranged in columns, when it is now composed of two sets of filaments running vertically and horizontally, spaced some 1.3 μm apart.

Various aspects of the formation of this filter net are considered.

The velocity of sound through spermaceti oil from the melon of two Kogia sima specimens, stranded in Florida in 1995, was determined across a range of temperatures between 7 and 38°C and at pressures between 0 and 90 atm. Sound velocity values ranged between 1395-1669 m s−1, increasing linearly with increasing pressure but decreasing non-linearly with increasing temperature. Polynomials were generated to describe sound velocity as a function of temperature and pressure for the core and peripheral lipids of the melon. The results suggest that, at normal body temperature, sound travelling from the back to the front of the melon would have a tendency to focus during dives to any depth, largely due to heat exchange across the periphery of the melon. Effects of changes in ambient temperature and pressure are described and discussed in relation to anatomy.

The sea anemone Anemonia viridis is one of the most common species of the North Aegean Sea. The variety in colour morphs exhibited by this species, causes problems to taxonomy and ecology, and suggests that A. viridis should be subdivided into two distinct species according to the colour of the individuals. The approach used in this study was based on the biometrical cnidae characteristics of the two colour morphs (rustica and smaragdina), as it is known that cnidae biometry has been used as a taxonomic tool for the phylum Cnidaria. More than 20,000 nematocysts were measured to try and find a correlation between these measurements and some body parameters indicative of the maturity grade of the individuals, as potential taxonomic characteristics. Stable cnidae characteristics of the two different colour morphs were compared. However, they differed only in the biometry of the tentacles' a-basitrichs. This slight difference does not support the proposal to subdivide Anemonia viridis into two different species.

To examine the effects of submergence time, free-space availability, and larval supply on height-related differences in settlement density of Semibalanus cariosus, we monitored the daily settlement density in plots where all benthos were removed daily and in natural-community plots, which were left undisturbed, at two sites with different tidal heights: the centre and the upper limit of S. cariosus zone, during one settlement season. Settlement density was higher at the low-tidal site, where settler mortality was low, than at the mid-tidal site, where settler mortality was high. The between-site differences in settlement was determined by larval preference for height and not immersion time. The settlement preference for height was masked on days with high larval supply, since suitable settlement sites in lower height were saturated by settlers.

The occurrence of developmental abnormalities in two ovoviviparous littorinids (Littorina neglecta and a barnacle-dwelling form of L. saxatilis) inhabiting the barnacle zone at Peak Steel, Ravenscar on the north-east coast of England was investigated. In general developmental abnormalities appeared to be a rare occurrence in both taxa. However, L. neglecta was found to have a significantly greater proportion of deformed embryos in their brood pouches than L. saxatilis B (Figure 1). A distinct seasonal variation in the number of developmental abnormalities was observed in L. neglecta, and it is suggested this is a result of broods developing outside of the main reproductive season being more prone to deformity.

The occurrence of the aristeid shrimp Hymenopenaeus debilis in the Mediterranean Sea is reported from two individuals collected in the Alborán Sea and off Eivissa (western Mediterranean) from depths of 668-679 and 1109-1140 m, respectively. Comments on the origin of the populations and biogeography of the species are related to the Mediterranean pseudopopulations hypothesis.