Series of sequences of SEM micrographs are presented to elucidate species-specific shell features in larval and post-larval stages of four Ostreidae (Bivalvia) species (Crassostrea gigas (Thunberg), C. virginica (Gmelin), Ostrea edulis L., and O. equestris Say). The diagnostic characters, including hinge structure, shell shape, and the dimensions of the prodissoconch, are identified and summarized in a key at both generic and species levels. In larval Crassostrea the skewed, backwards-pointed umboned shells with two hinge teeth on each side of the provinculum are significantly different from the round, dorsally-directed umboned shell with fewer, remarkably asymmetric teeth of larval Ostrea.In C. gigas the dimensions of the provinculum are longer and narrower (56x10 µrn) than those of C. virginica (50x14 µm); the lengths of prodissoconch I and the provinculum are greater in O. edulis (168 µm and 86 µm, respectively) than in O. equestris (120 µm and 74 µm, respectively). The present study suggests that precise quantitative measurements are needed for differentiation of the studied congeneric oyster species.

The small bivalve Abra tennis (Montagu) (Bivalvia: Semelidae) reaches the north-eastern edge of its range in the Wadden Sea near the Dutch/German border. In the Wadden Sea it is restricted to a narrow intertidal zone close to the high-water level. Data are reported from a population at Balgzand, in the south-westernmost part of the Wadden Sea, which has been monitored for two decades. This population showed a strongly fluctuating density and was seemingly absent for more than three years following three severe winters in succession. Over-winter survival in adults was greater during mild than cold winters, and close to zero during all winters that were colder than average. Recruitment was higher in warm than in cold summers. Growth was more rapid in warm than in cold spring-summer periods. In warm years growth rates were higher than in more southern locations, and values for maximum size and life span were relatively high.

Seasonal and annual variations in the distribution and abundance of echinoderm larvae (early to post-larvae of principally echinoids and ophiuroids), were determined from a series of plankton net tows taken at three stations in the Bay of Villefranche (France) and along a radial transect of 28 nautical miles (52 km), from the Bay to half-way to Corsica, between 1984 and 1988. Spatial distribution of six echinoderm species have been mapped. For the echinoids, Paracentrotus lividus and Arbacia lixula, spawning takes place twice a year and appears to be synchronous because larval cohorts were comprised of distinct age-classes both near and far from the coast. Recruitment for these species is, therefore, thought to occur at well-defined periods. In contrast, the ophiuroid species studied (Amphiura filiformis, Ophwthrix fragilis, Ophiopluteus bimaculatus and O. compressus) spawn several times per year with a relatively short period in late spring and a prolonged spawning between the end of autumn and winter. These later results are consistent with the presence of mixed size-classes of larvae either from the nearby coast or offshore. Recruitment for these ophiuroids appears to be much more variable and spread over time.

The reproductive biology of two epizoic deep-sea anemones reveals contrasting reproductive strategies. Amphianthus inornata (Cnidaria: Anthozoa) lives attached to the bathyal gorgonian Acanella arbuscula (Cnidaria: Anthozoa). Females of A. inornata increase in wet body weight as a result of increased oocyte production until 40% of the body weight is reproductive tissue. The anemone reproduces on a seasonal basis, releasing eggs in the early spring of each year. By contrast, Kadosactis commensalis (Cnidaria: Anthozoa) lives attached to the body wall of the abyssal holothurian Paroriza prouhoi (Echinodermata: Holothurioidea). This anemone is a protandric hermaphrodite, females being found only at the anterior end of the holothurian, whilst males are found at any point on the host. Females have a significantly higher wet weight than males and neither sex shows any reproductive seasonality.

One hundred and twelve Pycnogonids belonging to 18 species are recorded from waters of 12–490 m depth on both sides of the Straits of Gibraltar. Twenty-three specimens are Mediterranean (8 species) and 89 are Atlantic (14 species).

Hannonia stocki and Ammothella gibraltarensis are new species. Pentapycnon geayi is new to European waters and Pycnogonum nodulosum, Ammothella biunguiculata and Callipallene spectrum are new from southern Spanish waters.

A total of 38 species has now been reported for southern Spain.

INTRODUCTION

There are only two published papers on pycnogonids from southern Spanish waters: Munilla (1988) reported on mediolittoral and shallow-water taxa (0–12 m), with 11 species collected, while Stock (1987) recorded 20 species from deeper waters (135–2110 m).

The present collection of 112 specimens, from shallow to moderately deep waters, was carried out in July 1989 aboard the B/O ‘Garcia del Cid’ during the Project FAUNA 1, conducted by the Museo Nacional de Ciencias Naturales in Madrid (CSIC).

Rock pools are unique and complex habitats in intertidal areas. Quantitative studies of assemblages in pools are few. Abundances and distributions of species in pools on a rock platform near Sydney (Australia) were sampled for two years. Pools of four different depths (5, 15, 30 and 40 cm deep) and up to four strata within each pool (0–5, 5–15, 15–30 and 30–40 cm, from the top of the pool) were sampled, replicated at four sites. The abundances and distributions of most species of plants and animals in pools did not differ between strata nor at different depths in the pools. Abundances of only three species, the encrusting alga, Hildenbrandia prototypus Nardo, the trochid snail, Austrocochlea constricta (Lamarck) and the limpet, Cellana tramoserica (Sowerby) varied significantly between strata and depths. In contrast to other studies on rock pools, most species showed no significant temporal variations in mean abundances in the sites sampled. Significantly large, spatial and temporal, random fluctuations did, however, occur in abundances in individual pools. The consistency of abundances at larger spatial scales indicated that disturbance in these habitats may not be an important structuring process. The large variation between pools does, however, suggest that the history of each pool may have a more significant role in the character of its assemblage. Some implications of small-scale variability are discussed.

The stomachsof 23 striped dolphins (Stenella coeruleoalba Meyen, 1833, Cetacea), stranded along the Ligurian coast (western Mediterranean Sea), contained 32 species of cephalopods, crustaceans and fishes, totalling an estimated 2,723 prey specimens representing about 36 kg in weight. Cephalopods and bony fishes were equally important in the diet (50%). Todarodes sagittatus (34.5%) and Micromesistius poutassou (25.9%) were found to be the most important food species. Other species belonging to six cephalopod families, three crustacean families and nine bony fish families, contributed to the diet with variable numbers, weights, and occurrences, demonstrating the opportunistic character of striped dolphin feeding.

The species-specific abundance and biomass of marine planktonic ciliates were determined at monthly intervals at two stations in Southampton Water between June 1986 and June 1987. The two stations, an outer one at Calshot and an inner one at north-west Netley, were subject to differing marine and terrestrial influences. A total of 55 ciliate taxa were recorded during the sampling period; of these 34 taxa were identified to genus and 16 to species. The heterotrophic ciliate community at both stations was dominated by aloricate taxa which comprised >90% of the community abundance and biomass during some months. The loricate tintinnids were also common, especially at Calshot, during winter months. Oligotrichs dominated the aloricate community at both stations with haptorids prominent at north-west Netley. At Calshot, Strotnbidium sp. dominated the heterotrophic community abundance and biomass throughout the study period, while Askenasia sp., Strobilidium sp. and Tintinnopsis sp. were also common. Strombidium sp. also contributed most to heterotrophic community abundance at north-west Netley. Balanion sp. and Tintinnopsis sp. were also abundant. However, Cydotrichium sp. and Didiniunt sp. dominated community biomass at this station. Most taxa exhibited a seasonal cycle with low winter and high spring and summer abundances. Some taxa reached abundances of >2000 l1 However, maximum abundance of one species of Tintinnopsis was found during winter months. The autotrophic ciliate, Mesodinium rubrum, was also recorded at both stations achieving densities >105l1 at north-west Netley during ‘bloom’ conditions.

A new species of the genus Clausophyes (Siphonophora, Calycophora) is described from four anterior nectophores collected in the Southern Ocean. This species is distinguished from others in the genus by the presence of a large, undivided mouth plate on the anterior nectophore. However, in order to establish the distinctiveness of two other species in this genus, namely C. moserae and C. galeata, which a recent author has suggested should have only sub-specific ranking, the anterior and posterior nectophores of those species are redescribed.

Notice is given of the presence of a previously un-reported oedicerotid amphipod species, Pontocra tes arcticus Sars, in the shallow sublittoral zone of the sandy beach at Kames Bay, Millport (Scotland). Distinguishing features from P. arenarius are the parallel-sided second coxal plates, strongly deflexed narrow rostrum and lack of sternal dark pigmentation patterns in both sexes. A key to the three species in the genus is provided.

The genus Xenuraega Tattersall, 1909, has been overlooked for most of this century. The rediscovery of Xenuraega now brings the number of genera of Aegidae to six. The genus and the type species X. ptilocera Tattersall, 1909, are described in detail. Xenuraega is characterized by the following apomorphies: antennal flagellum extending beyond pleotelson; mandibular incisor absent, distal mandibular margin fused to cephalon; pleon abruptly narrower than pereon, pleotelson small, not concealing pleopods; uropod exopod reduced to short stub, endopod elongate, styliform, nearly as long as body; pleopods 1–5 not contained within or concealed by pleon and pleotelson.

A new species of mouthless and gutless free-living marine nematode, Astomonema southwardorum sp. nov., the dominant species from a methane seep pockmark in the North Sea, is described and illustrated. The new species is distinguished by its combination of short cephalic and cervical setae, with the latter being sparsely and irregularly distributed, and also in male specimens by its arrangement of precloacal and caudal setae and its postcloacal papillae. The genus Astomonema Ott, Rieger, Rieger & Enderes, 1982, is rediagnosed. Astomonema brevicauda (Vitiello, 1971) Vidakovik & Boucher, 1987, is considered to be a species inquirenda.

A new genus, Mesoikopleura, in the family Oikopleuridae (Lohmann, 1915), is described from several specimens collected at low mesopelagic depth (710–860 m) during different cruises using the ‘Johnson-Sea-Link’ submersibles, and from one collected by the ‘Cyana’ submersible during the ‘Gyrocean’ cruise. Three species of this new genus are described: M. enterospira, M. youngbluthi and M. gyroceanis. One of the species already described as belonging to the genus Pelagopleura is moved to the genus Mesoikopleura. Consideration of the genera closely related to Mesoikopleura leads to the division of the subfamily Oikopleurinae into two groups at the level of super genera: Labiata and Alabiata.

A cohort of newly settled Mytilus edulis (L.) (Mollusca: Bivalvia) spat (mean shell length 530 µm) was collected from red filamentous algae at a site on the North Wales coast. After a period of growth in the laboratory, cellulose acetate and starch gel electrophoresis were used to investigate genotype frequencies at the Gpi, Odh, Lap, Pgm, Idh and Mpi loci. Individual testing of each locus, using the X2 test revealed significant deficiencies of heterozygotes at the Pgm, Mpi and Idh loci. However, further testing using a sequential Bonf erroni test, designed to assess the probability of observing at least one significant result from a number of tests by chance alone, revealed that only the deficiency of heterozygotes at Pgm and Mpi loci was significant at the table-wide 95% level. Since post-collection mortality was <3%, these heterozygote deficits must have existed at the time of collection. The conclusion drawn is that heterozygote deficiencies in mussels are generated during the larval stage or at early settlement.

Tissues of Littorina littorea (Mollusca: Gastropoda) were processed for electron microscopy with an aqueous fixative which included hydrogen sulphide to precipitate intracellular cadmium. The procedure retained cadmium in the cytosol, where it was below the detection limit for x-ray microanalysis, but it did not increase the retention of the metal within lysosomes and other sites of accumulation where it was detectable. Aqueous fixation caused extraction of labile elements, particularly magnesium and potassium, and this effect was increased by the use of hydrogen sulphide. Cadmium and hydrogen sulphide had disruptive effects on the fine structure of cells. It is concluded that cytological fixatives should not include hydrogen sulphide, and that cryo-fixation is required for x-ray microanalysis of intracellular elements.

Tributyltin (TBT) pollution has exterminated populations of the dog-whelk Nucella lapillus along most of the north Kent coast (Thames Estuary) but the species survives as a small enclave around the North Foreland. Males in this enclave exhibit an unusual defect involving the non-development or partial development of the genital system: about 10% lack penes, or have undersized penes, and their gonoducts (vas deferens and prostate) are incompletely developed; in some cases, spermatogenesis appears to be retarded. Laboratory-bred animals display the same characters. This deficiency (‘Dumpton Syndrome’) is manifest also in the atypical development of male sex organs on the females (‘imposex’) induced by exposure to tributyltin (TBT). The evidence points to Dumpton Syndrome being a genetic disorder which has lessened the sterilizing effect of imposex and thereby has permitted the survival of this isolated enclave in an area of high TBT pollution.

The retina of larval herring (Clupea harengus L.) contains only cones, with rods recruited progressively from about eight weeks onwards. The molecular species composition of phospholipids from the eyes of herring of different ages was determined to find whether the appearance of di-docosahexaenoyl molecular species (di22:6n-3) of phospholipids, which are characteristic of rod outer segment membranes in higher vertebrates, coincided with the appearance of rods. In the eyes of larval herring (cone-only retina) di22:6n-3 molecular species comprised 25.9% of phosphatidylethanolamine (PE), 22.9% of phosphatidylserine (PS) and 4.2% of phosphatidylcholine (PC). In the eyes of adult herring (rod:cone ratio of about 20:1) the proportion of di22:6n-3 molecular species had increased to 49.5%, 39.0% and 16.8% in PE, PS and PC, respectively. Juvenile herring had intermediate values of di22:6n-3 phospholipids. The results confirm the hypothesis that the amounts of di22:6n-3 molecular species of phospholipids in retina increase during development as rods appear, and also show that cones contain smaller amounts of these unique lipids. Three other molecular species containing docosahexaenoic acid, 16:0/22:6n-3, 18:1/22:6n-3 and 18:0/22:6n-3 were also major components of eye phospholipids, emphasizing the important role of 22:6n-3 in vision.

Solidified adhesive (cement) of three balanid barnacles (Crustacea: Cirripedia) was dissolved using different concentrations of sodium dodecyl sulphate containing a reducing agent. The proteins were separated using SDS-PAGE and blotted onto polyvinylidene difluoride membrane for sequencing. Commonly occurring bands in the cement of each species were identified. One particular protein of 39 kD, found in the cement of Balanus perforatus, has the following N-terminal sequence: TYFPVLSYG?SSSLAPVI, where the? is most likely cysteine. Quinones were not identified in the cement by either infra-red, ultraviolet-visible or solid-state nuclear magnetic resonance spectroscopy and the successful dissolution and sequencing of cement proteins mitigates against their presence. Cement contains a mixture of highly hydrophobic proteins which are cross-linked through cysteine residues. It is the combination of these two components which makes cement highly resistant to chemical degradation. As a result bacteria are usually absent from the cement, possibly further excluded from the porous core of the cement by its smooth outer crust.

In contrast to the situation found in the bivalves Barnea Candida and Spisula solidissima prophase arrested oocytes of Ruditapes philippinarum cannot be fertilized when extracted from the ovary. They must first undergo germinal vesicle breakdown (GVBD) under the influence of the neurohormone serotonin (5-HT) which drives them to a second block occurring in metaphase of the first maturation division. We used Fluo-3 to investigate the possibility that calcium was involved as a second messenger in controlling this first step in meiosis reinitiation. Our data showed that, in addition to 5-HT, ionophore, thapsigargin and the weak bases ammonia and procaine could induce prophase-arrested oocytes of Ruditapes to resume meiosis.

Circumstantial evidence of mobility by the lepadomorph barnacle genus Pollicipes in the literature is supported by observations at Menai Bridge which indicate that the phenomenon is real. Although slow, movement may be in response to gravity, as a positive taxis, or light, as a negative taxis.