To analyse temporal distributions of microplankton populations and relationships to environmental conditions in marine ecosystems, a dataset of microplankton communities was investigated using a range of statistical methods. A total of 164 microplankton species comprising 100 microalgae and 64 ciliates were identified from 120 samples, respectively. Both planktonic microalga and ciliate assemblages showed temporal patterns and were significantly correlated between their temporal variations in abundance. The microplankton communities were characterized by 14 ciliates (e.g. Strombidium sulcatum, Tintinnopsis tubulosoides and Strombidium cheshiri) and 18 microalgae (e.g. Skeletonema costatum and Alexandrium tamarense). Multiple regression analyses showed that the interspecies correlations among these dominant species represented a complex network with a clear seasonal shift. Temporal pattern of microplankton communities was significantly correlated with the environmental variables such as temperature, salinity and nitrate nitrogen. The results suggest the clear species distribution and temporal dynamics of microplankton communities in response to environmental changes, and multivariate statistical approaches were a useful tool to reveal the species distribution patterns and complex microplanktonic interspecies correlations in marine ecosystems.

Mysids have previously been shown to consume oxygen at much lower rates when in a swarm (cohesive group in which individuals are evenly spaced but not polarized) than when in uncohesive small groups. Thus the swarm represents a strategy for conserving energy. In this study different swarm sizes of mysids were forced to perform escape responses by exposing them to jets of ammonium hydroxide, while measuring their oxygen uptake. Swarms of 200 individuals showed no significant difference in oxygen consumption with or without the ammonium treatment. In contrast, swarms of 100 showed a significant increase of around 45% oxygen uptake when exposed to ammonium. In conjunction with earlier demonstrations of increased feeding success and lower oxygen uptake when aggregated, this work clearly confirms the energetic benefits of being in a larger social group rather than a smaller one or remaining solitary.

The reproductive biology of Scyllarides deceptor was studied along the southern Brazilian coast (27°S 48°W) from December 2002 to December 2003. Samples were collected monthly at Xavier Island, where animals were caught and marked. Fecundity and egg size were estimated from ovigerous females caught also in two adjacent islands, Arvoredo and Aranhas. A total of 98 females was recorded at Xavier Island during the sampling period, 24 of these were recaptured and presented time-at-liberty ranging from 14 to 297 days. Ovigerous females were observed during spring and summer, with the moulting period lasting from late winter to spring. Size at sexual maturity was assessed from 66 females caught during the breeding season and estimated in 85.33 mm of carapace length (CL). Mean fecundity of S. deceptor was estimated in 191,262 eggs (±17,811, SE) for females, on average, 94.74 mm long (±1.86 mm SE) (CL). Fecundity was significantly related to CL (R2 = 0.90) Mean egg size was 0.67 mm (±0.005 mm SE) and did not correlate significantly to CL (P = 0.78). The rocky bottom of Xavier Island was favourable for reproduction, presenting shelter and foraging grounds for the ovigerous females. For management purposes, our results suggest the closure of the S. deceptor fishery from November to January and the capture-size of females to be restricted to animals larger than 90 mm (CL).

The jumbo squid Dosidicus gigas is the only ommastrephid commercially caught in Mexico. Despite the economic and ecological importance of this species, little is known about its early life stages. The relationship between the presence of paralarvae and mesoscale oceanic features was investigated for the first time in the central Gulf of California, Mexico in February, April, June and September of 2008. A total of 86 paralarvae were found only in June and September (summer season), in the well-stratified column water where the thermocline was evident and warm sea surface waters (27.7° to 29.4°C) dominated. The greatest abundance of D. gigas paralarvae was observed within 2.23 to 3.48 km of the main front. The mantle length of the smallest paralarvae corresponded with the mantle length at hatching. The San Pedro Mártir Island–Santa Rosalia transect and Santa Rosalia–Guaymas transect were determined as the main hatching localities in June and September respectively. The number of paralarvae found in this study contrast with the potential fecundity of mature females which are found throughout the year.

Three new species, Paraserpula planorbis, Omphalopoma stellata and Spirorbis sarsiae, are described and three known species are redescribed. A list is given of the Serpulidae found between 100 and 1000 fm (approx.) and an appendix gives a key to genera of the sub-families Serpulinae and Filograninae

The chromatophore system of the small loliginid squid Alloteuthis subulata (Mollusca: Cephalopoda) is very simple and the repertoire of body patterns limited. There are red and yellow chromatophores only. On the dorsal mantle there are more yellows than reds; on the ventral mantle and there are more reds than yellows. The dorsal reds are larger than the yellows and bear more radial muscles. The significance of these findings is discussed.

Alloteuthis subulata Lamarck is a small loliginid, common in shallow water near Plymouth (Holme, 1974; Lipinski, 1985; Rodhouse et al., 1988). Little is known of its natural history and behaviour and chromatophores and body patterns of adults have never been described, although the skin of this species has been used in physiological studies of colour change (Messenger, 1991; Messenger et al., 1991; Cornwell & Messenger, 1995).

Over 100 adult animals of both sexes, caught by trawl at depths of 10–60 m, were examined; their mantle lengths ranged from 70 to 130 mm. Living animals were observed in large aquaria with circulating sea-water. Counts and measurements of chromatophores were made on colour photographs (taken through a Nikon dissecting microscope) of pieces of fresh skin (20×20 mm) dissected from animals killed by decapitation or after MgCl2 anaesthesia (Messenger et al., 1985). Chromatophores were counted first when fully retracted (by 1×10−3 M 5-HT) and then when fully expanded (with 1×10−3 M L-glutamate: Cornwell & Messenger, 1995). All measurements were made in the same area of the body: the central and anterior part of the mantle, dorsally and ventrally (Figure 2).

Stomach contents from an adult male sperm whale (Physeter catodori) stranded at Penzance, Cornwall, included a total of 125 upper and 110 lower beaks (mandibles) of cephalopods. All but two of the cephalopod species represented by lower beaks were oceanic squid belonging to four species in four families comprising: Histioteuthis spp. (44·5% by number and 10·7% by estimated wet weight); Architeuthis spp. (42·7% by number, 82·2% by weight); Todarodes sagittatus (7·3% by number, 6·0% by weight); Galiteuthis sp. (0·9% by number, 0·02% by weight); an oceanic octopod, Haliphron atlanticus (3·6% by number, 0·9% by weight) and one neritic species, Loligoforbesi (0·9% by number and 0·1% by weight). Mantle lengths of the squid were estimated to vary from 126 to 1056 mm.

In Tunisia, elasmobranch landings have decreased substantially in recent years. Generally, species-specific information is largely unavailable for artisanal fisheries, but it is essential to increase knowledge and to ensure proper management of these species. This study analysed elasmobranch catches with longline fishery in the Gulf of Gabès. In total, 21 and 20 pelagic and bottom longline fishing trips were conducted, respectively, from July to September in 2007 and 2008. A total of eight elasmobranch species were caught: four batoids and four sharks. Pelagic longline captures were hooked externally while a high number of individuals captured with bottom longline were hooked internally. Discards due essentially to low commercial value and size represented 7.6% of total number of elasmobranch specimens caught. Longline landings in the Gulf of Gabès were principally composed of sandbar shark, Carcharhinus plumbeus, representing, respectively, 94.14% and 21.17% in number of pelagic and bottom longline captures. The importance of rhinobatids and Mustelus capture with bottom longline reflect their abundance in this area compared to other Mediterranean zones. Juveniles, including neonates with umbilical scars, dominated carcharhnids specimens, while smoothhound and guitarfish captures were dominated by mature individuals. Mitigation measures based on gear modifications, size limits and delineated nursery areas in the Gulf of Gabès should be developed to protect these vulnerable species.

The first results of the females reproductive cycle of Maja brachydactyla (Braquiura: Majidae) off the coast of Asturias (north-west Spain) are presented. Mean size of mature females was 133·4 mm (N=1022) in 1997 and 125·0 mm (N=942) in 1998. Only one cohort is exploited each fishing season. This cohort passed through the terminal moult the year before and recruited in to the fishery beginning in June. The breeding cycle off the coast of Asturias begins in December and ends in November the following year. Results from this study indicate that females produce 3–4 broods per year in these waters, which is the highest reported number for M. brachydactyla. The results are discussed in terms of their importance for management of the fishery.

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.

The present report continues the series of observations on the seasonal abundance of the pelagic young of teleostean fish in the plankton off Plymouth (Russell, 1938b), and gives the results for the year 1938. These results are published in the same form as in previous reports. The dates on which collections were made with the 2 m. stramin ringtrawl are given in Table I, and the monthly average catches of the young fish per half-hour oblique haul in Table II.

Underwater ultrasonography is a useful tool for studying structure and mechanical events in live, fairly large marine animals that do not possess an unduly thick, calcified integument. The limit of discrimination with present technology is about 2 mm, so fine detail is absent; the transducer has to be within 1–2 cm of the animal being studied or attenuation of the ultrasound by sea-water will restrict penetration of tissues. The non-invasive nature of the technique makes it ideal for the study of valuable or particularly delicate animals (e.g. Eledone); there would also appear to be considerable potential for use of ultrasonography as a teaching/demonstration aid in marine biology.

The piddock, Pholas dactylus L., gives off a luminous secretion when irritated. The luminous glands which produce the secretion are two longitudinal stripes in the exhalant siphon, a pair of triangular organs in the mantle cavity near the base of the siphon, and a stripe around the ventral rim of the mantle (Panceri, 1872).

The histology of the light-organs has been described several times. A light-organ is covered by a simple columnar ciliated epithelium, below which are many glandular cells, which discharge through the surface epithelium. The outer part of the glandular layer consists of a mass of large mucus cells. Deeper lies a second glandular region containing large cells with long necks that extend to the external epithelial surface. Dubois (1892, 1914, 1928) believed that the photogenic tissue was made up of two kinds of secretory cells; these were the superficial ciliated cells, which possessed glandular bases (fixed secretory cells); and deeper lying glandular cells derived from clasmatocytes (migratory secretory cells). Rawitz (1891) clearly distinguished a mucous from an underlying photogenic layer. The latter, according to Förster (1914), contains pyriform cells with long necks. He believed that he could distinguish a secretory cycle in the photogenic cells. Exhausted cells at the beginning of the cycle possessed an alveolar cytoplasm; granules began to appear in the cytoplasm; the granules increased in number and stained intensely with iron haematoxylin. Those photogenic cells which were filled with granules were in the active secretory state. Transitional stages between the inactive (or depleted) cells and the active (granular) cells were rare.

The simplified text-book view holds that hydroids' soft body is composed of a branched double-layered tube, whose wall consists of two epithelial layers (the inner gastrodermis and the outer epidermis) separated by the mesoglea. Some hydroids are characterized by large, complex colonies and likely an even more complicated inner organization. By using three species from the thecate hydroids of the family Sertulariidae we investigated the soft body structure of such hydroids. The anatomical study revealed some new features of colonial hydroids. The double layered coenosarc fills the perisarc (outer skeleton) tube only at the endings of the branched colony. More proximally, the coenosarc tube becomes narrower and a thin epidermal lining covers the inner surface of the perisarc tube. In some species the soft tissues of the shoots form a network of anastomosing canals. The canals are formed by the gastrodermal epithelium and they are embedded in epidermal tissue. In the upper part of the shoot, these canals are located at the periphery, along the inner surface of the perisarc. In more proximal regions of the stem, the whole lumen of the perisarc tube can be occupied by gastrodermal canals; the canals are enclosed in a parenchyma-like epidermal tissue. The organization of the soft tissue in these thecate hydroids is a striking example of structural complexity that does not contravene the limits of the ground plan of the phylum.

The purple sea urchin P. lividus is a marine resource greatly valued for its highly nutritious roe. The objective of this work is to analyse the spatial distribution pattern and population structure of this species in the region of Cantabria (Bay of Biscay) in order to identify the most appropriate zones for sustainable harvesting and for the establishment of adequate management strategies. Two depth ranges were studied (<5 and 5–10 m) in five coastal areas. The available stock of commercial individuals (size >55 mm) was estimated based on the density of individuals and biometric parameters. Significant differences were found among areas but not among depth ranges. Three areas showed low densities with large individuals, whereas two areas showed high densities with small individuals. Despite the average smaller size of the individuals, these high-density areas accumulated 76% of the commercial stock, making these the most suitable zones for the sustainable harvesting of P. lividus in the region. The high variability of the observed density values resulted in elevated uncertainty in the estimation of stocks. However, the high sea urchin densities together with the high percentages of commercial individuals suggest that the resource is currently underexploited. Further studies should be carried out, and precautionary measures should be adopted before opening the fishery. The suitability of many of these measures is discussed in the present work, as a necessary step in the management of the P. lividus fishery in Cantabria.

Deep-water trawling for fish species on the shelf slope off Scotland results in a by-catch of rare cephalopod species. The cirrate octopus Opisthoteuthis grimaldii is normally present below 800 m; at least one other species of cirrate and five species of incirrate octopus are found; significant extensions of range and depth are recorded. An incidental catch of the ommastrephid squid, Todarodes sagittatus, included a fully mature specimen and is indicative of its probable breeding locations. The results highlight the many taxonomic and systematic uncertainties surrounding the rarer cephalopod forms, and emphasize the utility of the fishing by-catch.

It is widely assumed that optimal timing of larval release is of major importance to offspring survival, but the extent to which environmental factors entrain synchronous reproductive rhythms in natural populations is not well known. We sampled the broods of ovigerous females of the common shore crab Pachygrapsus transversus at both sheltered and exposed rocky shores interspersed along a 50-km coastline, during four different periods, to better assess inter-population differences of larval release timing and to test for the effect of wave action. Shore-specific patterns were consistent through time. Maximum release fell within 1 day around syzygies on all shores, which matched dates of maximum tidal amplitude. Within this very narrow range, populations at exposed shores anticipated hatching compared to those at sheltered areas, possibly due to mechanical stimulation by wave action. Average departures from syzygial release ranged consistently among shores from 2.4 to 3.3 days, but in this case we found no evidence for the effect of wave exposure. Therefore, processes varying at the scale of a few kilometres affect the precision of semilunar timing and may produce differences in the survival of recently hatched larvae. Understanding the underlying mechanisms causing departures from presumed optimal release timing is thus important for a more comprehensive evaluation of reproductive success of invertebrate populations.

The resting spores of Ditylum are formed as a result of a peculiar kind of plasmolysis of the protoplast (Gross, 1939); they are small spherical bodies lying inside the old cell wall. Since one-half of the cell wall is only slipped over the other half it is likely that in the sea they might become separated and the resting spore proper would drop out of the shell. In a previous paper (Gross, 1937) it was stated that in old cultures a considerable number of resting spores could be found outside the parental shells, and when transferred into fresh culture medium they only expanded in volume. Since then more attention has been paid to such isolated resting spores and the formation of new cell walls has been frequently observed.

Relative growth and reproductive biology of Munida rutllanti were investigated for the first time in the Adriatic Sea. A total of 938 individuals were analysed. Sex-ratio differed statistically from the expected 1:1. Six individuals exhibited secondary sex characteristics of both males and females. Carapace length of males ranged from 10.5 to 21.5 mm, while in females it ranged from 11.2 to 19.4 mm. Sexual dimorphism was observed in seven morphometric characters. Ovigerous females were first observed in summer and later in autumn with higher frequency. Realized fecundity showed wide variation (273–3250 eggs) and positive correlation between the brood and female size. An epicaridean isopod Pleurocrypta sp., parasitizing the gill chamber of both sexes was isolated and its effect on the oogenesis was studied by histological examination of host reproductive system. Growth inhibition, modification of secondary sex characteristics, as well as retardation of oogenesis and failure of oviposition, are repercussions of bopyrid infestation. Given the small prevalence (7.85%) of the bopyrid in the M. rutllanti Adriatic population, we assume that for the moment there is no severe effect on the host population dynamic.

In 1962, 1964 and 1966 the author collected four species of marine triclads, viz. Procerodes littoralis (Ström), P. ireneae sp.nov., P. lobata (O. Schmidt) and Uteriporus vulgaris Bergendal in the Plymouth neighbourhood. Each species is fully described. Attention has been given not only to internal characters, as the structure of the genital apparatus, but also to external features such as the shape of the head and the pattern of pigmentation, because these external characters are sufficient for the identification of the species. Further, the geographical distribution and ecological data have been recorded for each species.