Age structure and hatchling dates of the squid Illex argentinus collected by bottom-trawl fishery in southern Brazilian waters were assessed by the analysis of statolith growth increments. Catches occurred between 2001 and 2002, from 23° to 32°S at depths of 100–700 m. Squid from juvenile to post-spawning stages were collected year round, with age estimated from 98 to 320 days and mantle lengths ranging from 112 to 376 mm. Duration of life cycle events based on statolith growth zones revealed that squids can spend about 14% of their lifespan as paralarva (~30 days), 70% as juvenile (~130 days), leaving maturity and spawning condition to the terminal 10–20% (~30–60 days). The results suggest that, unlike estimates available for Patagonian populations, a general 0.5 year lifespan is predicted for I. argentinus off Brazil. The wide range of size-at-ages implied that catches of shortfin squid off southern Brazil probably include squid hatched throughout the year. Mature and spawning squid caught in summer months hatched in winter and spring, while winter catches revealed mature-spawning individuals hatched both in summer/autumn (~6 months of age) and winter/spring periods (~10–11 months of age). It has been argued that such groups may combine both squid resident of Brazilian outer shelf and slope (22°–34°S) with a six months' lifespan and migrating squid originated from the northern Patagonian shelf (~42°S) with 10–11 months' lifespan.

An account is given of the mortality of Ostrea edulis at the Tal-y-foel oysterage from 14 days to 11½ years after metamorphosis. In the first year after settlement most of the deaths occur in the late summer, autumn and spring, and few during November-February. A survival curve has been drawn up and shown to correspond with Pearl's ‘positive skew rectangular type’. On the average, from 1000 14-day-old spat, 78 survive for 6 months, 18 for 18 months and 7 for 11 ½ years. At this oysterage the major predators are rare or absent, and the cause of most of the mortality is unknown.

Bioassays designed to test the effect of single or some combination of environmental factors or pollutants on aquatic organisms are usually performed in constant levels of the imposed conditions and commonly in static rather than flowing water. The reason for this is usually one of convenience and practical simplicity and the results are valid for the set of conditions imposed. However, since aquatic organisms are rarely exposed to constant and static conditions, the results of such tests cannot with confidence be extrapolated to field conditions. This is particularly true in the case of estuarine organisms for which, change is the rule.

The larval development of the Russell's snapper Lutjanus russellii is described and illustrated for the first time. Fertilized eggs, with a mean diameter of 0.80 ± 0.04 mm and a range from 0.71 to 0.84 mm, were spherical, transparent, buoyant and unpigmented. Embryonic development lasted 26 hours 50 minutes at 24.7°C. Newly hatched larvae were 1.86 ± 0.10 mm in total length (TL) with 24 (10 + 14) myomeres and had an oil globule in the ventroanterior area of the yolk sac. Two days after hatching (DAH, 2.61 mm TL), the mouth opened. Early larvae had melanophores scattered on the head, body and yolk surface. Thirteen DAH (2.74 mm TL), the buds of the second dorsal and pelvic-fin spines had appeared. At 5.81 mm TL, the notochord was slightly flexed, and the hypural bones and caudal-fin rays had begun to develop. The ratios of the second dorsal and pelvic-fin spine lengths to TL attained their maximum, 40% and 36%, respectively. At 14.02 mm TL, all fins had the adult complement of rays and spines. The characteristic of this species, with four black stripes on the sides and with a round black spot on the upper back, was completed in juvenile of 23.1 mm TL. The larval habitat shifted from the surface and middle layers to the tank bottom. A statistical model: Y equals 2.18e0.06X, where Y is mean TL (mm) and X represents DAH, explained 99.34% of variation in growth (P < 0.001, R2 = 0.9934).

In most fish groups, a large pair of Mauthner neurons provides a distinctive and conspicuous pathway linking the motoneurons of the cord to nerve VIII input. Physiological studies have been almost entirely on the apparatus in teleosts (review by Diamond, 1971), but its morphology is essentially similar in other groups, and it seems likely that wherever found in gnathostomes, its function is the same: to mediate a startle response involving a single rapid tail flip. It is therefore, as Whiting (1957) has emphasized, an important part of the reflex system in those lower chordates in which the myotomal musculature is used in locomotion. Not surprisingly, where locomotion is carried out in a different way (as for example in adult anura), the Mauthner neurons of the larva degenerate and disappear, as they do in a variety of teleosts where a tail flip startle response is inappropriate in the adult.

Novel predator–prey interactions are becoming increasingly relevant to investigate in the context of current geographical range expansions and biological invasions. This study describes a vigorous attack by a muricid whelk, Thais gradata on a mud-inhabiting mytilid mussel, Musculista senhousia, following new colonization of the mussel in the Brunei estuarine system (Borneo, South-East Asia). This represents only the second reported attack by a gastropod on this globally important invasive mussel species, and the first such attack in its native environment. Whelks migrated from their typical hard surface habitat and barnacle feeding to the sediment, where they aggregated and fed on the mussels. Field data suggest no selection by the whelks of the part of the mussel bed colonized or of the prey size attacked (median shell length = 21 mm). In addition to forming feeding aggregations, the whelks formed non-feeding resting aggregations off the mussel bed (sometimes of more than 80 individuals). These apparently facilitated synchronized mating and consequently the formation of large communal nests of egg capsules (involving approximately 3500 contributing females). During the investigation, the newly-formed mussel colony underwent mass mortality, and the whelks either redistributed on the sediment or returned to feeding on barnacles. The population-level response by the whelks described here maximizes energy transfer from prey resource to whelk propagation. In addition to the whelk's generality of habitat use and feeding behaviour, this is likely to contribute to sustaining populations in a system where prey abundance and distribution is limited by highly variable and extreme physicochemical conditions.

The prosobranch limpet Patella vulgata is an intertidal grazer performing looped excursions centred on a home scar. Foraging within each excursion is mostly concentrated around the point of maximum distance from home. The orientation of the foraging excursions in a group of limpets was analysed on a vertical substrate on a sheltered shore in North Wales. The spatial relationship between different excursions of the same individual was also analysed. A total of 174 complete excursions from 47 adult limpets were obtained using the LED (light emitting diode) tracking technique. In particular, the leaving direction and the direction of the main foraging area of each excursion were computed. When considering the foraging strategy over five consecutive days, a substantially radial cropping pattern was evident at both the population and individual level, with no evident directional preference. However, when considering consecutive excursions of the same individual a concordance in leaving directions was evident in about 40% of cases. The high overlap between the outward branch of the trajectory of one night and the homing branch of the previous one suggests that the directional decision can be based on a trail-following mechanism. Moreover, our data suggest that directional decisions are taken at the beginning of each excursion when leaving home.

A method for a qualitative analysis of sea urchin diet is based on the characterization of the photosynthetic pigment indices of the major algal groups in the sea urchin gut. The pigments were separated by reverse-phase high performance liquid chromatography (RP-HPLC). This study demonstrated that HPLC is a better method to estimate chlorophyll-a in the gut contents than the conventional spectrophotometric methods which overestimate the amounts by including chlorophyll-a breakdown products. Three sea urchins species, Paracentrotus lividus, Psammechinus miliaris and Sphaerechinus granularis, settled on the loose-lying coralline algae (maerl) in the Bay of Brest (France), were used in this study. The algal pigments identified within the gut contents included chlorophylls-a, -b, -c, fucoxanthin, lutein, βε-carotene and ββ-carotene. The presence of chlorophylls and carotenoid biomarkers was used to characterize the three algal groups: Rhodophyceae, Chlorophyceae, Phaeophyceae in estimating sea urchin diet. The pigment analysis reported here demonstrated that the three species of sea urchins investigated mainly consumed Rhodophyceae which dominate the epibenthic flora in the study area.

Knowledge of bio-physicochemical variables is essential to better understand the functioning of tropical marine ecosystems, which are rich in biodiversity and provide nutrition and livelihoods to billions of people in the developing countries. This study analysed the spatial and temporal variability of phytoplankton and zooplankton with chlorophyll, primary productivity, temperature, salinity, oxygen and nutrients in the Bay of Bengal (BoB), collecting data from the World Ocean, and COPEPOD and Aqua MODIS records. The results indicated a strong gradient in bio-physicochemical conditions of the BoB, from the coast to the open sea. Specifically, the spatial variability in chlorophyll was negatively correlated (R2 = 0.59) with temperature and zooplankton, while a positive correlation (R2 = 0.70) was noted between chlorophyll and silicate, nitrate, phosphate, dissolved oxygen and salinity. All the variables exhibited a strong vertical gradient at depths up to 500 m. Temperature, nutrients, zooplankton and to a lesser extent salinity and rainfall had an influence on the annual abundance of phytoplankton. Over the long term, a significant positive trend in temperature and a significant negative trend in primary productivity were observed in the BoB. The findings of this study will be useful to draw insights on the state of fisheries habitats and the overall environmental conditions of the BoB in response to future climate changes.

This study describes the spatio-temporal distribution, population biology, and diet of the puffer fish Lagocephalus laevigatus in Caraguatatuba Bay, south-eastern Brazil. Monthly samples were taken between August 2003 and October 2004 by trawls in two areas, south and north, at depths of 1 to 4 m. The fish were measured and their sex and reproductive stage determined. The abundance of this species was compared between areas and among months, and the items in the diet were identified and quantified. Lagocephalus laevigatus was rare in Caraguatatuba Bay, where only 199 small individuals (4.8 to 15.4 cm) were obtained in the entire study period, suggesting that this species uses the estuary as a nursery. None of the specimens of L. laevigatus captured in Caraguatatuba Bay were sexually mature. Higher densities of L. laevigatus in the bay were recorded in the south area and between October and December 2003, i.e. in the spring, suggesting that spawning may occur from late winter to spring (August through to November). The diet items consumed by L. laevigatus in Caraguatatuba Bay were, as expected from the current literature, crustaceans, mainly amphipods, and fish. However, the most-consumed item was the sea whip Leptogorgia setacea (Cnidaria). This feeding habit may be related to the presence of toxins (tetrodotoxin and saxitoxin) that are frequently found in the skin and viscera of L. laevigatus, which may be sequestered from the sea whip, which possibility still needs to be specifically evaluated.

The effects of algal diet on larval survival and growth of the barnacle Amphibalanus improvisus was for the first time examined under controlled laboratory conditions. Larvae were obtained by dissecting egg lamellae at later developmental stage out of the adults. Hatched nauplii were reared in 0.6-l glass beakers (200 larvae l-1) on a monoalgal diet of Chaetoceros calcitrans, Chlorella vulgaris and Scenedesmus quadricauda at 1x105 and 2x105 cells ml-1, under continuous light at 25 ±1°C. The rate of development, survival and size (at Stage V) of the larvae were measured for each diet. The majority of nauplius II larvae (~70%) fed with Cha. calcitrans and Chl. vulgaris developed into cyprids within seven days while those fed with S. quadricauda remained at Stage II. A shorter time interval for Stage II to III was observed in larvae fed with a Chl. vulgaris monoalgal diet than Cha. calcitrans. Larvae fed with Cha. calcitrans had shorter developmental intervals for later larval stages (Stages IV–VI). The highest mortality was observed in the treatment with a monoalgal diet of S. quadricauda, while the highest survival was achieved with a diet of Cha. calcitrans. The mixed diet of Cha. calcitrans, Chl. vulgaris and S. quadricauda resulted in a shorter developmental duration of larval cycle (six days). Both food type and food concentration significantly affected the length and width of the nauplius larvae.

The marked pattern of vertical zonation in the nearshore distributions of benthic fauna in sea-lochs seems to be controlled by the degree of fluctuation and extent of depression in salinity (Gage, 1974). The different vertical patterns in the abundances of species can be related to their known tolerances to reduced and fluctuating salinity. An overall faunal discontinuity seems to occur at a depth which roughly corresponds to the maximum depth to which markedly brackish conditions are experienced.

Located at 22°N on the northern shore of the South China Sea, Hong Kong experiences a seasonal, monsoonal climate and its resident scleractinian corals, comprising some 50 species, live here at the limit of their ranges. Summers are hot and wet, winters cold and dry and this study was initiated to determine the effects of bioerosion and periodic episodes of strong wave action on coral death and beaching. Coral rubble washed up on Telecom Bay Beach in the Cape d'Aguilar Marine Reserve was collected every month from January 1996 until December 1997, inclusive. Quantities were greatest after typhoons and storms, with the average monthly weight of recently-living corals accounting for approximately 0.007%, by weight, of the total live coral in the bay. Seventeen species of Mollusca were recorded from within the skeletons of this rubble and included a new record for Hong Kong, Anchomasa yoshimurai (Pholadidae). Species of Lithophaga dominated, with highest mean abundances recorded from within Goniastrea aspera, the most abundant living coral in the bay and from within the heaviest fragments. The overall incidence of borers was, however, low although it appears that dead coral borers, notably the basally boring Lithophaga lima, act to weaken coral attachment resulting in dislodgement and beaching during and after storms. At this relatively unperturbated site, therefore, the significance of borers in weakening coral attachment with subsequent detachment and beaching during and after storms, respectively, is low, a situation also seen elsewhere.

The optic cushion of Marthasterias glacialis is seen to contain yellowish orange and reddish orange pigments. The former occurs throughout the cushion, the latter is confined to the wall of the optic cups and a few scattered, irregular patches. Both pigments occur in the cytoplasm of long and narrow or irregular cells, some in the form of granules or vacuoles.

Optic cushions yield an orange extract in methanol which decomposes in light.

The behaviour of methanolic extracts after partitioning, saponification, chromatographic separation and spectrophotometric examination indicates the presence of β-carotene and esterified astaxanthin.

The significance of the results in relation to previous findings and their possible bearing on photoreception is discussed.

INTRODUCTION

Detailed studies of the vertical distribution and migration of the micronekton, plankton and sonic scattering layers in an oceanic environment off Fuertaventura in the Canary Islands were made from R.R.S. ‘Discovery’ during September to December 1965. A general account, including a statement of the objectives of the cruise, has been given by Currie, Boden & Kampa (1969). Foxton (1969) has described the biological sampling methods and techniques utilized. Results of sonic scattering investigations have been published by Blaxter & Currie (1967) and Boden & Kampa (1967). The present study deals only with the pelagic amphipods, and forms a contribution to a series (Angel, 1969; Clarke, 1969b; Baker, 1970; Foxton, 1970a, b; Badcock, 1970; Roe, 1972a, b, c, d; Pugh, 1974) dealing with the distribution and migration of the major taxa sampled during the investigation. An objective summary of the plankton data utilizing factor analysis and cluster analysis has been provided by Angel & Fasham (1973, 1974).

The scaleworm genus Pholoe (formerly referred to Sigalionidae) is common and often abundant in marine benthos. In northern Europe, 1–3 species may be present in a single sample but not recognized as distinct, or one species may be reported under different names in different studies. This results in an underevaluation of diversity and precludes comparison between data sets. Four valid species of Pholoe are common in nearshore European waters, but inadequate descriptions and species misinterpretation have resulted in most of these being misidentified as the western North Atlantic P. minuta, not known to occur in European waters. The present note attempts to resolve this confusion; it is based on examination of thousands of specimens, many of them alive, from northern Europe and elsewhere. An illustrated key and notes with brief synonymies for four nearshore northern European species are provided; use of Shirlastain A for temporarily darkening protruding structures is described. Pholoe inornata (type species of the genus), P. baltica and P. assimilis (resurrected) are briefly characterized.

Records are given of the numbers of barnacle larvae obtained from samples of water pumped through a plankton net. Several series of hauls were made at intervals over the time of year when barnacle larvae are abundant.

The numbers of the cyprid larvae of Balanus balanoides in the surface waters show a diurnal variation, being markedly less during the hours of darkness. This conclusion may also apply to the cyprids of B. crenatus and Verruca stroemia, but the numbers of these larvae were too small to permit reliable conclusions to be drawn. There is some evidence that similar diurnal variations occur in larval stages other than the cyprid.

Experiments are described which suggest that Calliactis behaves as a closed animal in its movements, although its stomodaeum appears to be widely open to the exterior.

Observations of the movements of the animal are correlated with variations of the internal pressure. It is shown that expansion is not merely ‘passive relaxation’, but is generally accompanied by a rise in pressure which is, however, much lower than that which accompanies rapid closing.

It is concluded that the fluid-muscle system of Calliactis behaves in a similar way to that of other soft-bodied invertebrates, but that the system works at a much lower pressure.

During the Joint Chilean–German–Italian Magellan ‘Victor Hensen’ Campaign in 1994 an epibenthic sledge (EBS) was used to catch the epibenthic and benthic-boundary-layer macrofauna.

Eighteen EBS samples were taken at 12 locations on a transect through the Beagle Channel. The aims of the study were to describe the epibenthic molluscan species, to quantify their abundances and to describe their distribution. In total 35,087 specimens were collected, yielding 107,223 ind 1000 nr−2. Bivalvia were most abundant 78,615 individuals (52 spp.) followed by Gastropoda (17,289, 52spp.), Aplacophora (4745, 9 spp.), Polyplacophora (4665) and Scaphopoda (1909,5 spp.). The molluscan abundance of the hauls were strikingly different, between 3 and 37,927 ind 1000 m−2 haul. Only stations off the eastern entrance showed high abundances, which was represented at all depths and sediments. Elsewhere the abundances were low. Species richness was highest in shallow water (< 100 m) with 69 species and decreased with depth. But at the deepest station 37 species were found.

The tiny bivalve mollusc Montacuta (Tellimya) phascolionis (Dautzenberg & Fischer) belongs to the family Montacutidae, which is usually classified in a grouping of a superfamily rank, the Galeommatacea (= Erycinacea, Leptonacea or Leptonoidea) and includes many small and rather obscure species that are found associated with a wide variety of usually burrowing marine invertebrates (see Boss, 1965). M. phascolionis recently has been referred to the genus Tellimya (Chavan, 1960, 1969; Bowden & Heppell, 1968) or removed from the Montacutidae altogether and put into a new monospecific genus, Phascoliophila (Nordsieck, 1969). It is clear that a comprehensive revision of the Montacutidae is badly needed in order to establish the correct position of the present species within the family. However, the present author feels it justified in the interim to follow Ponder (1968) in recognizing Tellimya as a subgenus of Montacuta that includes the species phascolionis.