Deep or subsurface chlorophyll-a maximum (DCM) was studied at one station in the middle Adriatic from December 1996 to June 1998. Chlorophyll-a concentration, abundance, volume carbon concentration, size-fraction of phytoplankton and phytoplankton community structure were determined. In addition, physical and chemical factors as well as nutrients were determined. The DCM occurs during both the vertical mixing and stratification period in the middle Adriatic Sea. It is most frequent between 50 and 75 m. It is located below the pycnocline and it is associated with the nutricline. Phytoplankton size-fraction and community structure vary seasonally. The DCM is most pronounced during spring phytoplankton blooms with diatom dominance. Procaryotic picoplankton Synechococcus sp. was abundant in DCM during summer stratification. The DCM represents both a biomass maximum and a phytoplankton adaptation to low irradiance.

Temporal evolution of the ingestion and absorption rates of organic matter and biochemical components in the filter-feeding bivalve Cerastoderma edule (Mollusca: Bivalvia) fed for 12 d on the same ration (1.5 mm3 l−1) of the microalgae Tetraselmis suecica (Chlorophyta: Prasinophiceae) having different biochemical composition, were measured. Cockles in group E were fed algal cells harvested at the exponential growth phase (55.5% of protein, 16.8% of carbohydrate and 27.6% of lipids) whereas cockles in group S were fed cells harvested at the stationary growth phase (45.3% of protein, 35.2% of carbohydrate and 20.0% of lipids). After the feeding period cockles were submitted to starvation and biochemical analysis of faeces produced during final steps of gut evacuation (after 24–96 h of starvation) was performed to estimate biochemical composition of metabolic faecal losses (endogenous matter lost during the process of digestion).

Ingestion rate of organic matter was found to gradually increase during the feeding period in both groups. Absorption efficiency of organic matter decreased but reached an asymptotic minimum with rising ingestion rate. This relationship resulted in a gradual enhancement of absorption rate of organic matter over the time. Lipid fraction of food was found to be absorbed with significantly lower efficiency (even negative values were recorded in group S) than proteins and carbohydrates irrespective of the diet. Endogenous faecal losses presented high proportion of lipids (up to 66%) and lower proportions of proteins (∼25%) and carbohydrates (∼9%). On the other hand, increasing carbohydrate abundance in the diet brought about no apparent enhancement of carbohydrates absorption efficiency. Results are discussed in relation to the time-course of digestive enzyme activities.

The paper on the ratio of nitrogen to phosphorus in the sea (Cooper, 1937) was written before it was realized that in phosphate determinations, using two ml. of molybdate reagent per 100 ml. of water, the magnitude of the salt error correction factor is changed by the use of a spectral filter. Due to the resulting uncertainty it was felt better to use uncorrected figures for phosphate content rather than to risk a correction which might later prove to be wrong.

The four species studied (Bledius spectabilis, Heterocerus fenestratus, Dichirotrichus pubescens and Cillenus lateralis) are most commonly found in a region delimited by the anaerobic mud of the lower bank and the dense marsh bordering the drainage channels in tidal salt-marshes at Scolt Head Island, Norfolk.

Experimental submersion of the beetles in sea water was found to induce an apparent anoxic condition which was associated with a drastic reduction in oxygen consumption. On return to air there was a large increase in oxygen consumption characteristic of an appreciable oxygen debt.

The use of the physiological responses to submergence as an indicator of effective contact with water revealed that their subterranean mode of life largely prevents direct exposure of the beetles to sea water in natural conditions. A significant proportion of Heterocerus fenestratus were, however, found to be vulnerable to flooding by sea water during tidal coverage of the burrow system.

These results are considered in relation to the observations made on the behaviour and burrowing activity of the various species.

An examination of the proportions of pedal disc colour and isozyme phenotypes, in samples of Actinia equina L. collected from around Britain, has shown that individuals which are heterozygous for a gene complex involved in morph determination occupy a habitat intermediate in position to those occupied by the two homozygotes. It is concluded that A. equina may best be considered as comprising three morphs, rather than two as had been distinguished previously.

As the abundance of anemones in samples displaying a particular pedal disc colour phenotype decreases, the proportion of these individuals which possess atypical combinations of colour and hexokinase-i phenotypes increases. This result is interpreted as indicating that individuals are subject to differential selection in different habitats, dependent upon their genotypes at hexokinase-i, or those at some other tightly linked locus.

Introduction

Our recent work on Actinia equina L. has revealed the existence of two morphs amongst anemones collected from British coasts, having column coloration ranging from red to brown (Quicke, Donoghue & Brace, 1983). One morph displays pedal disc colour (coloration) (PDC) ranging from red to pink (R), and occurs in the upper part of the intertidal range of this species, where it is commonly found firmly attached to vertical rock faces. The other has a grey (G) or green (H) pedal disc, which may sometimes display contrasting red or orange radial lines (L); these colour phenotypes will be collectively referred to as GHL. This latter morph occurs predominantly at a lower tidal level, where it usually occurs on horizontal surfaces to which it adheres relatively weakly.

Mesozooplankton was studied during 2008 in coastal waters of the İskenderun Bay in order to determine seasonal changes in abundance, biomass, community structure and their relationship with environmental factors. Samples were collected seasonally at five stations using WP-2 net of 200 µ mesh size by vertical hauls. A total of 23 planktonic groups including 30 copepod species, 4 cladocerans and 4 chaetognaths were identified. Copepods were the most important group during the whole period of survey. Penilia avirostris was found to be dominant in spring, while Paracalanus parvus in summer and winter, and Acrocalanus gibber in autumn. Mesozooplankton abundance varied from 438 ind m−3 (autumn) to 7163 ind m−3 (spring), while biomass varied between 2.2 mg m−3 (summer) and 52.9 mg m−3 (autumn). Differences in abundance and biomass between seasons were statistically significant (P < 0.01). Clear seasonal distribution patterns were observed in the area. Two peaks in abundance were defined: a major peak in spring and a second minor one in autumn. It seems that the trophic element was the main factor affecting the density distribution of zooplankton populations, whereas species distributions were more affected by hydrographical parameters, namely: seawater temperature and salinity.

The population biology of the crab Liocarcinus depurator was studied for one year in the mussel raft culture areas of the Ria de Arousa. The density and biomass of this species is much higher in the raft areas, especially in the outer part of the ria, than in the central channel area. Maximum abundance occurred during the winter months (up to 8-80 g wet weight m and 0-44 individuals m.

Maturity size in females was set at 28-30 mm carapace width, (based on ovigerous females) and is attained in the first year of life. The ovigerous females were most abundant in January (approximately 70% of the mature females), but another less important maximum value was observed in May, attributable to a second spawning. Modifications in the sex ratio from 1:1 affected individuals larger than the maturity size during the season when there was a greater number of ovigerous females present. Data on sex ratio and breeding cycle indicate that ovigerous females move towards the raft areas located in the outer part of the ria. Trawl recruitment took place in the stations located in the outer Ria, and mainly in August-September, although it continued to a lesser extent in autumn.

The Von Bertalanffy growth function was fitted to both sexes in the two outer stations. Growth rate was higher in males than in females, while variability between stations was less important. However the growth rate and reproductive output of L. depurator in the Ria de Arousa was higher than in populations from other geographical areas, possibly because of the availability of food from the rafts and or the oceanographic conditions in the ria.

The adhesion of single podia of Asterias rubens (Echinodermata) was tested under different conditions in order to determine those factors which have an effect on the adhesive forces. In common with many other marine organisms, the adhesion of the podia is sensitive to surface properties of the substratum. The effect of immersion and emersion on tenacity (force per unit area) has been tested. Working with the asteroids completely immersed in sea-water appears to be the best technique to measure the adhesive forces of the podia. The mean tenacity of the podia of A. rubens on glass underwater is 1·98×105 Nm−2.

The measurement of the adhesion strength of marine invertebrates and of its variation under different conditions may give clues to how marine bioadhesives function. Adhesive forces have usually been measured in invertebrates using either permanent or transitory adhesion, but only rarely recorded in animals using temporary adhesion (for review see Walker, 1987).

Of all macrobenthic organisms, echinoderms have exploited temporary adhesion most efficiently. In echinoderms, adhesive systems are usually associated with the podia and are involved in locomotion, attachment, feeding, or burrowing (Flammang, 1996). The paucity of information regarding the adhesive strength of echinoderm podia is due possibly to the fact that these animals possess a multitude of podia that are not all attached at the same time, making it difficult to evaluate the exact number of podia involved in adhesion at any precise instant in time. For example, maximum detachment forces involving many podia have been measured for several asteroid species. Feder (1955) measured up to 4 kg (39·64 N) in Pisaster ochraceus, Lavoie (1956) over 3 kg (29·43 N) in Asterias forbesi, and Christensen (1957) 5 kg (49·05 N) in Evasterias troscheli. Unfortunately, the number of podia adhering to the substratum was not estimated in any of these studies. It is not possible, therefore, to calculate tenacity (adhesive force per unit of surface area) which makes comparisons impossible either between these different asteroids or with other marine invertebrates (see Walker, 1987). Tenacity has been considered in only one study (Paine, 1926) where the mean adhesive force using single podia of the asteroid A. vulgaris was 17·2 g (0·17 N), giving, when divided by a mean measurement of the surface area of the podial discs, a tenacity of 1·25×105 N m2.

Sex phenomena in molluscs have been widely investigated, and the relevant literature on the subject has been reviewed by Coe (1943,1944). Coe recognizes ambisexuality (monoecism, hermaphroditism) and unisexuality (dioecism, gonochorism) and further subdivides ambisexuality into functional ambisexuality (functional hermaphroditism), consecutive sexuality, rhythmical consecutive sexuality and alternative sexuality. Of these, functional hermaphroditism is of widespread occurrence: it is encountered in all the main groups, with the exception of scaphopods and cephalopods. Of the more than 20,000 species of living gastropods approximately half are functional hermaphrodites when fully adult (Coe, 1944). Limpets of the genus Patella are unisexual, though there is evidence that sex change may occur in some of the species (Orton, 1920, 1928, in Patella vulgata; Bacci, 1947, in P. coeruled). Little is known with certainty of the mechanism of sex-determination in these animals, but sexuality appears to be labile since it seems that more than 90% of individuals of P. vulgata change sex at some stage in their life history. Aberrant sexual forms might therefore reasonably be expected to occur. In the present paper thirty hermaphrodite gonads encountered in an examination of 64,576 limpets are described and their significance in the wider context of sexual phenomena in molluscs is discussed.

Humpback whales (Megaptera novaeangliae) have a worldwide distribution in the oceans and are known for their very long migratory potential. Their migration routes consist of productive feeding areas located in high-latitudes and to low-latitude areas used as breeding and calving grounds. Genetic studies in humpback whale populations consist mainly of nuclear and mitochondrial DNA. In general, these studies provide similar results to estimates of gene flow, but some discrepancies may be caused by gender-biased migration to breeding grounds and further dispersion by males. There is little evidence of trans-equatorial and inter-oceanic migrations, but those movements have been confirmed by both analysis of photo-ID of naturally marked individuals and also genetic analysis. The combination of migratory and genetic analyses suggest an overlapping of breeding grounds in low-latitude areas, where the gene flow among those oceanic populations is more likely to happen, despite the opposite seasons in the northern and southern hemispheres. These results have important implications in the conservation perspective, especially for the determination of protected areas and for development of international agreements.

Cliona delitrix is one of the most abundant and destructive coral-excavating sponges on Caribbean reefs. However, basic aspects of its reproductive biology, which largely determine the species propagation potential, remain unknown. A 2-year study (October 2009 to September 2011) was conducted to determine the reproductive cycle and gametogenesis of a C. delitrix population located in a shallow reef in Florida, USA. Mesohyl tissue collected from randomly chosen and tagged sponge individuals was sampled one to several times a month, and analysed by light and transmission electron microscopy (TEM). Cliona delitrix is oviparous and gonochoric, except for a few simultaneous hermaphroditic individuals. The C. delitrix reproductive cycle in Florida is from April to December, and is triggered by an increase in seawater temperature to 25°C. Oogenesis and spermatogenesis were asynchronous among individuals; with different cohorts of oocytes co-occurring in females, and spermatic cysts in males. Granulose cells acted as nurse cells, contributing to the growth and maturation of both female and male gametes. Spawning of gametes was not always synchronized with full moon phase. Unlike most other oviparous sponges, the reproductive cycle of C. delitrix is versatile and includes multiple spawning events during the summer of each year. This characteristic maximizes sponge propagation on coral reefs during the warmer months of the year, particularly when thermal stress induces coral mortality. This aspect, combined with its success on polluted areas, make C. delitrix a suitable bioindicator of coral reef health.

Sexual maturity of the spider crab Libinia ferreirae was assessed for each sex, based on body dimensions and observations of gonad condition. A total of 346 crabs were analysed, of which 68% were females. Immature and adult individuals were recognized based on their allometric growth and gonad development. Abdomen width (AW) vs carapace width (CW) and propodus length (PL) vs CW were the relationships that best separated allometric groups of females and males, respectively. For females, gonad and allometric morphological maturity were, respectively, 38.77 and 39.43 mm of CW, which is close to the carapace size of the smallest ovigerous female (38.08 mm). For males, gonad maturity was 34.86 mm of CW and three allometric phases were observed: immature (IM♂), adolescent (AD♂) and adult morphometrically mature (MM♂). The IM♂ phase showed lower values of CW and PL than the AD♂ phase, without spermatophores inside the vas deferens; the AD♂ phase exhibited higher CW values than IM♂, but lower CW and PL values than the MM♂ phase, and the presence of spermatophores in the vas deferens; the MM♂ phase had higher values of CW and PL than the AD♂ phase and spermatophores in the vas deferens. Therefore, females showed synchronic morphometric, gonadal and functional maturity, while in males, gonadal maturity was attained before morphometric maturity, which probably could be a reproductive strategy for this species.

Animals develop behavioural strategies throughout life to improve their survival in nature. Juvenile activity and behaviour of the commercial tropical sea cucumber Stichopus cf. horrens were examined considering factors that may influence survival at this critical developmental stage. Wild juveniles were observed in situ to describe diel activity and movement. Wild and hatchery-reared juveniles were observed in the laboratory to evaluate the influence of different light-dark cycles and microhabitats on feeding and sheltering behaviour. All juveniles (4–54 g) displayed a distinct nocturnal activity pattern both in the field and laboratory. Nocturnal activity was strongly associated with feeding and locomotion. Wild and hatchery-reared juveniles were most active at night, displayed intermediate activity during twilight, and minimal to no activity during daytime. Movement rates of wild juveniles in situ were significantly influenced by time and size to a lesser extent. Under constant light and constant dark for 48 h, juvenile feeding rhythm was endogenously controlled and strongly entrained to natural light-dark cycles. Sheltering was directly affected by light and linked to strong phototactic and thigmotactic reflexes. Juveniles preferred vegetation as shelter compared to coral, sand or open space, and showed equal preference for seagrass and macroalgae. Deviations in behaviour of hatchery-reared juveniles under laboratory conditions indicate some degree of acclimation to an artificial environment with minimal threats and a decreased sensitivity to light. The implications of nocturnal feeding, light-induced sheltering, shelter preferences and acclimation to artificial conditions are discussed in relation to juvenile survival in nature and potential restocking of the species.

A total of 17,651 km of sailboat survey effort obtained with very good sighting conditions was pooled over the period 1995 to 2007 to provide an insight into Cuvier's beaked whales' (Ziphius cavirostris) distribution in the western and central Mediterranean Sea. Although only six confirmed sightings were obtained under such conditions, complementary sightings made a total of eleven confirmed records. Their distribution showed that only slope habitat, and its close proximity, was favourable to the species. In contrast to regions pointed out in the recent literature, such as the Alboran, Ligurian and Ionian Seas, it appeared that the Tyrrhenian Sea was likely to be an important area for Cuvier's beaked whales in the Mediterranean. Sighting rates of 0.1–0.25 sighting/100 km and sighting rates for individuals of 0.2–0.5 individual/100 km were obtained in favourable regions. When compared to sighting rates obtained on Risso's dolphins Grampus griseus during the same surveys, the Cuvier's beaked whale appeared to be quite a frequent species in its favoured habitats. The present study contributes a better knowledge of this poorly-known species, in the context of increasing and threatening anthropogenic noises.

The squid Loligo vulgaris has an extended spawning season within the upwelling system off north-west Portugal, and its paralarvae may thus develop under a wide range of environmental conditions. Both temperature and salinity are expected to affect the metabolism of young squid and we tested their effects on growth during the embryonic and post-hatching phase, based on measurements of growth increments in statoliths of juveniles and adults, using generalized additive models. There was no evidence that statolith increments representing early growth become unreadable in adult statoliths. Variability in the statolith size at hatching was weakly but significantly related to the variables in the model. On the other hand, the effects on statolith growth of both sea surface temperature and of sea bottom temperature were significant during early post-hatching life. Thicker increments are deposited in the statoliths of squid living under higher temperatures, which results in summer hatchers having larger statoliths at the age of 90 days. Inspection of the statolith accretion pattern, using a piecewise linear regression method, revealed an ontogenetic shift in increment width, which may be an indication of the age of transition from paralarva to juvenile. On this basis, it is suggested that the planktonic stage lasts 60 or 90 days, depending on whether the paralarvae lived at higher (>15°C) or lower (<15°C) sea surface temperatures. The life strategy under warmer conditions potentially favours survival by reducing the duration of the vulnerable planktonic phase.

Cochlodesma praetenue is well adapted for a sedentary life in sheltered conditions in soft substrata at low-water mark to a depth of 60 fathoms.

The habits, morphology and ciliary feeding and cleansing mechanisms are described and compared with those of members of the related families Thraciidae, Pandoridae and Lyonsiidae.

The complex ligament is described. The mantle edges are extensively fused. The detailed structure of the siphons is described and related to their function of laying down mucus-lined inhalant and exhalant tubes.

The morphology and ciliary currents of the stomach show modifications similar to those previously described for Pandora. These modifications involve the extent of the major typhlosole and the replacement of an intestinal groove by lateral rejection grooves.

Analysis of three large samples shows that Cochlodesma from the Northumberland coast live for a maximum of 5 years. These animals become mature in their third year, spawning in early November.

The embryonic and larval development of the pipefish Nerophis lumbriciformis is described. The full development sequence lasted 30 d (at 14–15°C), being shortened to 25–26 d at higher temperatures (16–17°C), and hatching occurred throughout a 2–3 d period. Unlike species of the genus Syngnathus, the newly hatched larvae presented a functional mouth apparatus and the yolk sac completely absorbed.

The effect of dredging on bottom structure was assessed, to estimate the damage inflicted on the benthic macrofauna left on the dredge path and to evaluate aggregations of scavengers within the track. Sediment suspended during dredging rapidly resettled both on sand and sandy-mud bottoms. Dredge tracks were deeper on sandy-mud sediments and persisted longer than in sandy sediments. The disappearance of tracks in both sediment types depended both on current strength and wave action. Damage and mortality induced by dredging on the macrobenthic animals left on the dredge path was relatively low. Post-fishing SCUBA diver observations showed that damaged animals left on the dredge path rapidly attracted scavengers, mainly Ophiura albida. Immediately after the tow ophiuroids reached densities eight times greater in the track region than in the background. However, they dispersed again rapidly because only few damaged fauna were available on the dredge tracks. Undamaged or slightly damaged shellfish started to rebury immediately after escaping from the dredge.

Competent larvae of the commercially important marine gastropod Concholepas concholepas (Gastropoda: Muricidae) ‘loco’, were collected in the field and exposed in the laboratory to adult conspecific shells with and without barnacle epibionts. Settlement and metamorphosis was induced by the presence of barnacles on shells of live or dead conspecifics, but not by C. concholepas shells without barnacles. Results from laboratory experiments agreed well with field surveys showing the presence of recruits on conspecific shells overgrown with barnacles in shallow subtidal habitats (∼3–30 m deep), suggesting the potential importance of barnacles in inducing settlement and metamorphosis of locos under natural conditions. Most loco recruits were found below the C. concholepas shell apex, feeding on barnacles, inhabiting crevices among them, and inside dead barnacles. The mean size of recruits on locos' shells increased over four months from the beginning of the settlement season and no individual larger than 1·5 cm was observed, suggesting that they abandon adult loco shells at this size, roughly 5–6 months after settlement.

The copepods described in this paper come from two sources, the Firth of Clyde and the St Lawrence River. Several new species were collected from Balloch Bay on the Greater Cumbrae in 1935 and 1936 during an attempt to obtain some of the early species described from Scottish waters. The remainder were collected while working at the Biological Station at Trois Pistoles, Quebec, during a visit to Canada in 1937. The environment in Balloch Bay is composed of a fine muddy sand, strewn with boulders. The bay is on the eastern side of the island and therefore in a sheltered position. A description is given in Appendix III of The Biology of the Sea Shore, by Flattely & Walton (1922). The conditions under which the Canadian material was found will be dealt with in a later paper describing the remainder of the collection from the St Lawrence; it will be sufficient here to state that the conditions are essentially marine.

Copepods from three allied genera are included here: Paramesochra T. Scott, 1892; Leptopsyllus T. Scott, 1894; and Remanea Klie, 1929. The first two have for some time been in a state of considerable confusion and it has been a matter of some doubt into which genus the various species should be placed. Several efforts have been made to clarify the position (notably by Klie, 1929 and Monard, 1935) but the more recent work of Kunz (1938) has produced a clear separation based on the presence or absence of an endopod on the second leg.