The spawning period of the nudibranch mollusc Onchidoris bilamellata (L.), although generally extending from December to May, has occasionally been reported to occur also in summer and early autumn. Preliminary data are presented here on the larval development of summer and early autumn spawnings and compared to previous studies of the larval development of ‘normal’ (winter-spring) spawnings. The possible causes and consequences of the rare summer and early autumn spawnings are discussed.

The nudibranch mollusc Onchidoris bilamellata is distributed around the British Isles, the Atlantic coast of France, Iceland, Greenland, and the coasts of North America and Japan (Thompson & Brown, 1976). It exhibits an annual life cycle with a single spawning season, generally extending from December to May in which the adults spawn repeatedly. At the end of May/June the post-spawning mortality of the adults is usually complete (Todd, 1979). Summer and early autumn spawnings have been recorded in intertidal populations only occasionally (Todd, 1979 and references therein; present study). Larval development has been studied previously on larvae hatching from eggs laid during the ‘normal’ spawning season. No information is available on the larval growth and development of summer and early autumn spawnings. In the present study two key points were addressed: the occurrence of individuals and spawn masses in the field throughout the year; and the identification of any distinctive traits of the July and September offspring.

The field observations were carried out on the south-eastern coast of Scotland (56°18′N 2°39′W) from July 1993 to August 1994. The surface sea-water temperatures were recorded from January 1993 to August 1994 in St Andrews (56°20′N 2°47′W), seven miles from the location under study (Figure 1).

Two aspects of the physiology of the burrowing shrimp Caliianassa tyrrhena (Decapoda: Thalassinidea) were studied in order to investigate the effects of the general pollution load: total (TRR) and weight-specific respiration rate (SRR) as well as the digestive enzyme activity of the digestive gland.

Caliianassa tyrrhena exhibited a very low respiration rate (mean TRR=64-29 μl 02 animal−1h−1, N=60; mean SRR=0·18 μl 02mg DW−1h−1, N=61).

The slope of the TRR-DW logarithmic regression (b=0·64) showed that respiration in C. tyrrhena is proportional to body surface. Size is the dominant factor (among size, sex, season and locality) determining the variation in respiration rate. Comparison between the two sites with the different pollution load showed that there were no significant differences in the respiration rates of the same size class and season, except for the youngest animals in summer which showed a significant decrease in their respiration rate at the polluted site.

A similar ‘inhibitory’ effect of pollution has been observed in the activity of the majority of the 19 digestive enzymes tested. Only three e.g., trypsin, β-galactosidase and α-glucosidase showed an increase in polluted waters.

One could suggest, therefore, that C. tyrrhena can be considered to be preadapted to the low oxygen conditions encountered in the sediments, because of its burrowing mode of living.

During high-tide, the majority of Gobius cobitis exhibit a microhabitat shift, moving up to the mid-intertidal walls and cliffs, a typical blenniid habitat that is not used by this species during low-tide. Observations on feeding behaviour that showed that fish behave as an ambush predator, being capable of hunting fish of considerable size, combined with its movements to typical blenniid habitats, suggest that this species may have a predatory role as a fish predator on the rock intertidal.

We investigated the population dynamics of the spider crab Libinia ferreirae, focusing on the frequency distribution of individuals in size classes, sex ratio and the action of environmental variables (temperature, salinity, texture and organic matter content in the sediment) on reproduction and recruitment. Monthly collections were made in the Ubatuba region from January 1998 to December 2000. A total of 222 individuals were collected, including 123 juveniles (males and females), 43 adult males, 25 non-ovigerous adult females and 31 ovigerous females. Unlike most adult brachyurans, there was no significant size difference between sexes, and sexual dimorphism seems to be a varying characteristic for this crab genus. The reproductive period and recruitment were continuous with peaks that could be related to water mass dynamics and higher food availability in the Ubatuba region. In addition, our results increase knowledge about part of the life cycle of L. ferreirae, which could be useful for comparative studies.

The general composition and abundance of microalgae in sediment, water column and stomach contents of scallops were studied at two Euvola ziczac beds on the south-eastern inner Brazilian continental shelf. These areas, which support an extensive demersal fishery, are hydrologically dominated by Tropical and Subantarctic Waters and exhibit a summer water intrusion of South Atlantic Central Water (SACW). The same genera of benthic diatoms, mainly <30 μmm, were found on sediment and scallop stomach samples. Despite the seasonal variation of hydrographic conditions, the composition and abundance of main benthic diatoms from sediment and stomachs did not change throughout the year. On the other hand, phytoplankton from the water samples collected above the seabed (mainly pelagic diatoms >30 μm and dinoflagellates) was composed of distinct taxa and presented a high seasonal variation in abundance. The prevalence of microphytobenthos in the scallop diet suggests the importance of this community to the sustainability of this valuable demersal fishery resource.

The nomenclature follows André (1946). No Acarina were listed in the Plymouth Marine Fauna (Mar. Biol. Assoc., 1931), but Hydrogamasus littoralis, Rhombbgnathus pascens, R. seahami, and Halacarus basteri have since been recorded from Wembury (Colman, 1940).

During recent cruises of R.R.S. ‘Discovery’ in the eastern North Atlantic an investigation has been made of the depth distribution and diurnal migration of the pelagic fauna in selected oceanic areas. This continuing programme has entailed intensive mid-water sampling with opening-closing nets, fishing discrete depth horizons mainly within the upper 1000 m but also on occasion at greater depths. Hauls made during the cruise of January-April 1968 in a position 11°N, 20°W, south-east of the Cape Verde Islands, yielded 43 specimens of an apparently new species of the genus Acanthephyra. A further 113 specimens were taken during a subsequent cruise to the same area and the species has also been recorded in a sample collected in the Indian Ocean during the International Indian Ocean Expedition.

Having examined the literature and concluded that the species was undescribed the author referred to the large collection of decapod Crustacea that had been amassed as a result of cruises of ships of the Discovery Committee made prior to 1939. This material, together with that taken on the Dana Expeditions, had formed the subject of Dr Stanley W. Kemp's extensive studies on the Oplophoridae (Kemp, 1939), consequently the carefully preserved, labelled, and identified specimens represent a unique reference collection. It proved to contain five specimens identical to those taken at 11°N in 1968. Not unexpectedly Kemp had realized their uniqueness and had not only designated the type but named it. A description, however, was never published although it was prepared and has in part survived.

The published observations of other workers, on samples of herrings taken from the area under consideration, whether they relate to the study of such morphological characters as the number of vertebræ and keeled scales, or are chiefly concerned with the examination of the growth of the fishes as indicated by their scales, demonstrate very clearly that the eastern, central and western sectors of the area are visited by herrings which differ in character. It will be convenient to summarise the opinions of these workers under the headings of the statistical regions in which the samples were taken. The reader is referred to the chart on page 269, which shows the geographical extent of the regions dealt with.

Postmarsupial development and growth of Natatolana borealis were studied from Skogsvåg and Raknesvåg on the western coast of Norway. Growth was determined from size and instar stage distributions. Growth was also examined in laboratory kept isopods that were collected from Skogsvåg. The postmarsupial instar stages were identified using the number of articles and the position of setae on the flagellum of the first antenna and other morphological features. The mean size of isopods in instar stages 1—3 did not show any significant seasonal variation in Raknesvåg. The estimated growth and mortality rates of males and females were not significantly different. Nine and 11 postmarsupial instar stages were found in material from Skogsvåg and Raknesvåg, respectively. The life span from instar stage 1 to 9 of male and female N. borealis from western Norway was estimated to be 3—4 y. Mortality rate increased significantly from instar stage 9 to 10 of both sexes. Isopods that attained instar stage 10 and instar stage 11 in Raknesvåg, may have lived 4—5 y. The mean size of instar stages 8 and 9 and the size-to-weight relationships were significantly higher in material from Raknesvåg relative to that from Skogsvåg and may have been caused by differences in food access and predation pressure at the two study sites. Specimens sampled from the Bay of Monaco attained smaller adult size than the isopods from the Norwegian population.

The octopus fishery in the southern tip of South America is based on Enteroctopus megalocyathus. It is fished on both the Atlantic and Pacific coasts, but no study has yet investigated the genetic variability of this octopus, which is frequently collected as bycatch. The genetic identity and diversity of E. megalocyathus from specimens caught by the king crab fishery along the Beagle Channel in southern Chile was investigated using sequences of three mitochondrial (16S rRNA, COI and COIII) and one nuclear (rhodopsin) markers. Homologous sequences from other Enteroctopodidae were included to determine the genetic variability of E. megalocyathus. In addition to E. megalocyathus, genetic data allowed us to identify Muusoctopus eureka, a species also collected by the king crab fishery. Enteroctopus megalocyathus was found to be genetically similar to E. zealandicus; the genetic distances between these two species were low, 0% (16S rRNA), 0.2% (COI) and 0.6% (COIII), which was also confirmed by the phylogenetic topologies, as both species are in the same clade. Enteroctopus megalocyathus has low levels of genetic diversity, as shown by haplotype and nucleotide diversity values for the mitochondrial markers (Hd = 0.06–0.32; π = 0.0001–0.003), and null diversity for the nuclear marker. All the haplotypic networks resolved with the mtDNA markers showed shared haplotypes among E. megalocyathus, E. magnificus and E. zealandicus. The low genetic diversity of E. megalocyathus can be attributed to both the geological history of South America and the life history of the species, rather than to the king crab fishery.

Mitochondrial dehydrogenases, antioxidant enzymes, transaminases and cytochrome P450 activity have been studied from the digestive gland of Mytilus galloprovincialis, reared in a non-polluted area of the Mar Grande of Taranto (Ionian Sea, Mediterranean).

A new species of Cerapopsis (Cerapopsis takamado) is described from the Atlantic coast of Morocco. The genus Cerapopsis, synonymized with Photis Kröyer for nearly a quarter of a century is re-established and now known to contain two species.

Decapoda taken in Continuous Plankton Recorder (CPR) samples from the Pacific in 1997 and 2000–2003 have been identified and measured. Some previously un-described larval stages were referred to species and characteristics of these are described. Distributions and seasonal occurrence of decapod taxa in the samples are described and discussed with particular emphasis on the dendrobranchiate shrimp Sergestes similis and the brachyurans Cancer spp. and Chionoecetes spp. There is a prolonged larval season at low levels of abundance off the Californian coast but in the more northern waters there is a shorter productive period but numbers of larvae per sample are high, particularly in June. Larvae of Chionoecetes and other Oregoninae were found only from May to July.