Darina solenoides (Mactridae), a common intertidal bivalve in the Argentine Patagonian coast, serves as both first and second intermediate host for the gymnophallid Bartolius pierrei (Trematoda: Digenea). Cercariae enter the clams actively by piercing the mantle border; young metacercariae ascend along the space between the outer mantle epithelium and shell and they settle in the dorsal general extrapallial space just ahead of the posterior adductor muscle. Host reaction comprises mantle tissue alterations (hyperplasia and metaplasia) leading to the encapsulation of the metacercariae by the formation of a one-cell-layer thick sac, which progressively detaches from the mantle epithelium. Sacs containing fully developed metacercariae, which are surrounded by a hyaline non-cellular envelope, become internal and are found in the postero-dorsal region of the visceral mass. Two sacs usually containing from two to 44 metacercariae, one at each side of the clam, were observed. In some cases, in which the infection seems not to proceed as usual, dead and dying metacercariae and their debris were found in the same position within the extrapallial space where the host reaction usually starts. In these cases, the mantle reaction is accompanied by an inner shell surface alteration consisting of calcium carbonate deposits partially surrounding the reaction complex or other abnormal calcifications in the form of loose mineral concretions.

Cold vapour atomic absorption spectrophotometry (CV-AAS) was used to evaluate total mercury concentrations in Posidonia oceanica, after initial mineralization of the samples in a microwave oven. Measurements were taken of three leaf tissue types: the adult leaf blade, the adult leaf sheath, and the intermediate leaf blade. Plants were sampled monthly over a one year period at two sites presenting different degrees of pollution: Rosignano (Tuscany, Italy) and Tonnara (Corsica, France).

The mercury concentrations recorded in the different P. oceanica tissues were systematically higher at the more contaminated of the two sites, thus confirming the value of this plant as a biological indicator. The mercury concentrations observed exhibit seasonal variations, with higher concentrations recorded in winter than in summer. These variations seemed to be negatively correlated to the plant's phenology. Also, the mean mercury concentrations were generally lower in young tissue (intermediate leaf blade) than in the older tissue (adult leaf blade).

The state of the knowledge about the marine alien molluscan species from Italy is provided based on a critical review of records compiled from an extensive literature survey and from unpublished data obtained from 2005 to 2010. Based on the IUCN definition of ‘alien’, 35 molluscan taxa (18 Gastropoda, 16 Bivalvia and 1 Cephalopoda) are reported here, for each of which the following data (collected up to December 2010) are provided: published and unpublished records from the coastal and offshore territorial seawaters of Italy, including lagoons, within the 14 biogeographical sea divisions covering the Italian shores, date of first record, most plausible vector(s) of introduction and establishment status. The southern Ionian Sea, the northern Adriatic Sea and the eastern-central Tyrrhenian Sea resulted to be the areas most affected by alien molluscan introductions. The rate of records of new alien species (evaluated on the basis of live findings) is quite uniform over five decades, with six to eight species recorded per decade. The analysis of the vectors showed shipping/maritime transport to be the most common vector of introduction (40%), followed by trade (24%). Nineteen alien molluscan species (54%) were considered as established in Italy.

The feeding successes of four species of crabs (Crustacea: Brachyura) which are potential predators of the scallop Pecten maximus (L.) were studied under laboratory conditions. When provided with scallops of 4 and 5 cm shell height, Liocarcinus depurator (L.) did not consume any scallops whereas Liocarcinus puber (L.), Carcinus maenas (L.) and Cancer pagurus L. ate both size groupings but with varying success. The differences in the number of scallops eaten paralleled crab size such that C. pagurus, the species with the largest individuals (ca. 10.4 cm carapace width), ate the most, and small crabs (< 5.5 cm carapace width), irrespective of species, ate none or very few scallops. Further experiments with C. pagurus and a wider size range of scallops (3–9 cm shell height) revealed the following trends: as prey size increased, the proportion of crabs feeding decreased and there was minimal predation on scallops > 7 cm shell height; male and female crabs showed similar predatory behaviour; and marine fouling on scallop shells had no significant effect on crab feeding (X2 test, P > 0.05). These findings are discussed in relation to the potential for bottom culture of P. maximus.

Changes in the reproductive strategy of Sphaerechinus granularis (Echinodermata: Echinoidea) according to food availability were examined by comparing gonadal index changes from two populations with different food conditions. The better nutritional situation was confirmed by a repletion index always higher without significant inverse relationships with the gonadal index. The two populations exhibited a different reproductive strategy during their life cycle. The food limited population showed a delay in reproductive competence, a lower gonadal index and an increase in relative gonadal growth with age. This population showed a seasonal inverse relationship between the consumption index and the gonadal index during the spawning period. A discussion based on the variations in the main life history parameters between the two populations: reproduction, somatic growth, longevity, underlines the plasticity of this species which must maximize its reproductive output in terms of changes in food availability. The adaptive value of this plasticity was observed by the reduction in somatic growth which decreases the energetic cost of maintenance and by the increase in size of the feeding structure (Aristotle's lantern) which improves food acquisition.

Analysis of the carotenoid pigment and lipid concentrations of groups of the smaller zooplankton organisms from different depths has suggested a midwater maximum for carotenoid concentrations and a slight depth-related increase in lipid content. Similar analysis of seventeen species of euphausiid has not indicated similar trends, but has shown a close relationship between size and pigment content in all species other than those of Stylocheiron, which have significantly lower pigment concentrations. Comparisons of the data of Fisher, Kon & Thompson (1964) on the pigment and lipid concentrations of copepods with the known depth ranges of the various species have suggested a midwater maximum in pigment concentrations, but no consistent trends in the lipid concentrations. A midwater pigment peak is explicable in terms of pigment accessibility and requirement for protective coloration, and the significance of the pigments is discussed.

In Balanus balanoides (L.) several abrupt physiological changes occur after the breeding season in November. They include loss of gonads and associated organs, the acquisition of a high degree of cold tolerance (Crisp & Ritz, 1967), interruption of the regular sequence of moulting cycles (Crisp & Patel, 1960) and the reduction in feeding activity.

In a previous paper (Journ. Mar. Biol. Assoc., Vol. XVII, No. 1, Sept., 1930) I described in detail a series of experiments on Growth and Maintenance in the Plaice which were carried out during 1928 and 1929 at Cawsand, near Plymouth, and at Lympstone, near Exmouth. The purpose of the present paper is to present and discuss data collected at the above places during 1930 in continuing the experiments. The conditions under which the last experiments were carried out were identical with those of 1929, i.e. refined with reference to those of 1928. Several additions were made, however, to the series of 1929. Two fish of each sex were supplied with maximum rations while living under the conditions maintained during 1928 and were segregated in a box, which had the original ½″ mesh wire-netting windows but which was divided up into compartments. This experiment was arranged in order that we might ascertain the possibility of food leakage due to tidal action during the course of the earliest experiments, but it also enables us to compare the results obtained under slightly different conditions of water circulation, which is important in view of the fact that the windows of the modified boxes were of necessity minimal in area.

Many workers have considered the possibility of hydroids being potentially somatically immortal, largely because of the continued production of interstitial cells which can differentiate and migrate to replace cells in other parts of the hydroid (Schmid, Schmid & Tardent, 1974). In addition, many thecate hydroids show an orderly regression and replacement of their hydranths (see review by Toth, 1969) and this led Crowell (1953) to suggest that by this means hydroids might avoid senescence. Such considerations are undoubtedly fostered by the lack of evidence for senescence of hydroids which, although sometimes showing a cycle of degeneration followed by regrowth from a dormant stolon, may live for many years in the laboratory (Strehler, 1961; Brock, 1974). Only recently has the senescent death of a hydroid (Corymorpha nutants (L.)) been recorded (Svoboda, 1973).

Skeletal growth banding has been studied in the vertebral arm ossicles of the shallowwater brittle stars Ophiothrix fragilis, Amphiura filiformis, A. chiajei, Ophiura ophiura and O.

albida collected from near Oban. Scanning electron microscopy of ossicle microstructure show the bands reflect differences in stereom porosity and surface relief on the surface of the wing-like fossae of the ossicle. The evidence supports the interpretation of the bands as annual growth markers, with coarse-pored stereom laid down during periods of active growth in summer/autumn whilst finer-pored stereom, that often forms ‘breaking wave’- like ridges, is formed during periods of slow or negligible skeletal growth during the rest of the year. Growth curves fitted to growth ring measurements indicate three contrasting growth strategies amongst the species examined. These data generally support recent interpretations of demographic structure reached from studies of size frequencies in samples collected from other areas in the NE Atlantic range of these species.

Dredging activity poses an environmental risk to sponges as sediments from the dredge or disposal site may smother the sponge surface, potentially affecting water filtration and light penetration. Dredge-related sedimentation effects may also vary between sponge morphologies, potentially impacting community structure and functioning. To test this, 10 sponge species encompassing four different morphologies (massive, erect, cup and encrusting), were exposed to a single pulse treatment of three different sediment concentrations (0, 250 and 500 mg l−1) and followed over 2 weeks, in 1000 l tanks. Total suspended solids (TSS) and sedimentation rates (SR) were recorded throughout the study. A sharp decrease in TSS was recorded within the first 2–3 h and a total settlement of sediments occurred within the first 48 h of the pulse exposure (0, 8 and 16 mg cm−2 in the control, medium and high sediment treatments, respectively). The effects of high sedimentation included mortality of cup-shaped Callyspongia confoederata and small areas of tissue necrosis in other species, with massive, encrusting and wide cup morphologies particularly affected. However, the sediment concentrations tested in this experiment did not cause changes in the concentration of sponge pigments or the structure of the symbiotic microbial community in any species. These results indicate that a single pulse of sediments less than 16 mg cm−2 is not detrimental to most of the sponge species studied.

The statoliths of 14 species (193 right statoliths from subadult to adult individuals), belonging to five Cephalopoda families (Sepiidae, Loliginidae, Enoploteuthidae, Ommastrephidae and Octopodidae) were analysed using morphometric methods based on landmarks (geometric morphometry). The aim of the current study is to determine the discriminating power of statolith shape analysis in species identification of Mediterranean cephalopods. Discriminant analyses of the partial warps were able to fully identify (100% discrimination) the species of all families, except Octopodidae which showed some misclassification (correctly classified about 68–90%). These results were also shown by relative warp analysis. Octopodidae statoliths were studied for the first time using geometric landmark-based methods. Greatest differences in statolith shape between Octopodidae species, were in the area that unites the statolith dome with the flat wing. Landmark analysis applied to statoliths can be a useful taxonomic tool in the identification of closely related species.

L. pallidula is more or less confined to Fucus serratus. L. vincta is common on F. serratus but is also found on Halidrys, Laminaria and various Rhodophyceae. Neither species occurs in the absence of these weeds on which they both feed and spawn. Lacuna species are the dominant gastropods on weed at M.L.W.S. at Whitburn, County Durham.

Both species are annuals. In L. pallidula the growth rates of females and males are markedly different, the former growing both faster and over a longer period. Females attain a mean maximum size of 8–4 mm compared with 45 mm for males. L. vincta males and females grow at approximately the same rate, though females usually attain a greater size.

Males predominate in L. pallidula at all times of the year, comprising between 55% and 75% of the population with a mean of 68–6%. Males die slightly sooner than females but there is no more than 4 weeks difference in longevity. Copulation in L. pallidula begins in November and continues to April, with two peaks in January and March.

Spawning commences in January in both species and reaches its peak by April in L. pallidula and by June in L. vincta. Hatching occurs in L. pallidula from April to July. The time of first hatching in L. vincta is not certain but is probably about March. Larval settlement occurs from June to October with a maximum in September.

Density is high following hatching in L. pallidula (> 2000/m2) and settlement in L. vincta (> 300/m2). Dispersion is similar in the two species, being aggregated at high density and more or less random at low density.

It is usually very difficult to obtain knowledge of predator-prey relationships in the marine plankton. However, because of the very specialized nature of this relationship, where the copepod spends part of its life as a parasite and part of its life as a predator, detailed understanding of the relationship has been obtained from both laboratory and field observations.

The usual concept of predation involves a predator which is the same size or larger than its prey. This prompted Foxton (1966), in discussion of the large salp Salpa thompsoni, to consider only the gut contents offish, sea birds, seals, etc., when analysing data on predation. He noted that considerable mortality occurred between the embryos and the adult stages which did not appear to be explained by the data on predators which he considered. He concluded that ‘further study is necessary before (the salp's) true role can be defined’.

Copepods and amphipods are often associated with salps in distribution (Hardy, 1936), usually being regarded as parasites (Furuhashi, 1966; Wolfenden, 1911). Amphipods which lay their eggs directly into the living tissue of salps have been described (Haruhiko, 1967), while the use of the salp test as a protective house by the amphipod Phronema is well known (Hardy, 1956).

Dense swarms of Thalia democratica occurring in S.E. Australian waters are often associated with high densities of Sapphirina copepods (Dakin & Colefax, 1940; Thompson, 1948; Sheard, 1965). Observations of these swarms underwater, by the author, show the presence of many Sapphirina copepods inside salps in the undisturbed state, as in Plate I (A).

The family Otinidae is the smallest and probably the least known among the pulmonates. Thiele (1931) places it at the base of the Basommatophora, the more primitive order of the subclass Pulmonata, in the Stirps Actophila. It contains a single species, Otina otis Turton, with a geographical range confined to the coasts of the British Isles and north-west France. Its northern distribution reaches as far as the Firth of Clyde, according to Jeffreys (1869), and over the greater part of its British range it appears to follow fairly closely the distribution of the barnacle Chthamalus stellatus, which here reaches its northern limit. Otina otis is a tiny snail, and its external form is limpet-like. The shell, which is well described by Jeffreys (1869), and also by Ellis (1926), measures up to 2*5 mm in length, with a short apical visceral coil at the posterior end. It is dark chestnut brown in colour, and most resembles a minute Haliotis.

Light and electron microscopical studies were carried out in order to characterize the blood cells of the bivalve mollusc, Scapharca inaequivalvis (Bruguière). Cytochemical techniques were also used to investigate peroxidase, phenol oxidase and lysosomal enzyme activity in the cells. Four types of blood cell were found: the more numerous erythrocytes and three populations of white blood cells. The red blood cells were found to be nucleated and contained dense cytoplasmic granules and various organelles; a well-developed Golgi apparatus, rough endoplasmic reticulum, variable numbers of mitochondria and fine cytoplasmic microtubules were observed. The white blood cells were generally smaller and less frequent. The type 1 cells possessed variable numbers of acidophilic, cytoplasmic granules and showed a high degree of vacuolation. The highly granular cells showed more extensive pseudopodia, perhaps indicative of intense phagocytic activity. The type 2 cells were basophilic and possessed few or no cytoplasmic granules. The type 3 cells were infrequently seen; they were relatively large and packed with large, dense, acidophilic, membrane-bound granules. Peroxidase and arylsulphatase activity was found to be present in the type 1 and 2 white blood cells and in the cytoplasmic granules of the erythrocytes. No phenol oxidase activity was detected.

Stable carbon and nitrogen isotopes and fatty acid compositions of Aurelia aurita, Stomolophus meleagris and Cyanea nozakii collected from the Yellow Sea in August 2009, were analysed. δ13C and δ15N values of the jellyfishes were in the range of −22.0‰ to −17.4‰ and 4.8‰ to 10.6‰, respectively, which indicated that jellyfishes in this study area were mainly dependent on marine-based carbon. The trophic levels of jellyfishes were estimated as between zooplanktons and high level carnivorous fishes. Low C18:1n-7/n-9 ratios and high C20:1 (n-11 and n-9) and C22:1 (n-11 and n-9) concentrations suggested jellyfishes in the Yellow Sea were carnivorous and zooplanktons were an important diet for them. Fatty acid compositions of jellyfishes were characterized by high C20:4n-6 concentration (>10%), with ratios of C20:5n-3/C22:6n-3 >1. Specific fatty acids (C20:1 + C22:1 and C20:4n-6) indicated that both pelagic-derived material and benthic detritus-derived food were diet of jellyfishes. Variations of certain biomarkers (C15:0 + C17:0, C20:1 + C22:1 (n-11 and n-9) and C20:4n-6) in jellyfishes of different body sizes suggested that ontogenetic diet shifts may take place during the growth of jellyfishes. Larger individuals with higher C20:1 + C22:1 (n-11 and n-9) concentration, tended to consume more zooplanktons; while the detritus-derived material made a more significant contribution to the small individuals, as suggested by higher C15:0 + C17:0 and C20:4n-6 concentrations. According to our study, besides the diet, species seemed to influence variations in stable isotopes and fatty acid compositions in jellyfishes.

The free-swimming young of the Rissoidse are particularly important in the plankton for there is always one or more species present in any month and they usually occur in great abundance. The various species live between tide-marks, in the laminarian and coralline zones and in deeper water in several fathoms depth; wherever tow-nettings are taken they usually contain some species of this family. The inshore waters, however, are the richest in rissoids. Even in winter certain species are common round the Plymouth coasts. Some years ago it was found that very young herring just before losing the yolk-sac and about a fortnight old had been eating small rissoids, evidently almost newly hatched (Plate I, Fig. 1). The herring up to a length of about 12 mm. and just after the yolk-sac had disappeared altogether continued to eat them but usually after this size they ate only small Crustacea. From 1917 to 1921 it was found that out of 140 young herring examined, 91 had fed on these small gastropods. In later years they were also found feeding on them (Lebour, 1921, 1924). Other minute planktonic organisms were eaten, including algæ, tintinnids, copepod and cirripede nauplii and very small adult copepods; also a minute bivalve larva but no other gastropod, although other veligers were present in the plankton, Patella being specially common. The young herrings hatch out from December to February, therefore these little gastropods must also hatch at this time and this proves to be the case for in the plankton there are large numbers of these very young veligers (Plate I, Figs. 7–8). Later on, in spring, older stages of the same mollusc abound and are quite the commonest veligers in the plankton near the coast (Plate I, Figs. 17–19). In the summer they have almost entirely disappeared.

In July 2002 the southern hemisphere ascidian Corella eumyota was detected in the northern hemisphere for the first time, attached to floating docks in two harbours in north-western France: Perros-Guirec and Camaret-sur-Mer. Most individuals in the large clumps of tightly packed aggregations contained a clutch of brooded embryos in the atrial cavity, resting on the posterolateral epithelium overlying the ovotestis very close to the openings of the sperm duct and oviduct which are immediately adjacent to each other on the surface of the ovotestis, a morphological peculiarity not previously reported. These openings are far from the atrial siphon; it is possible that the species routinely self-fertilizes. The larvae are retained after hatching until they are competent to settle, resulting in a very short free-swimming larval period, limited dispersal, and a tendency for the larvae immediately after release to settle on the parent tunic or adjacent adults. It is hypothesized that individuals attached to some type of hard substrate were transported anthropogenically to France. Because the two harbours in which these nonindigenous ascidians were living are small, they probably represent secondary sites of invasion into France; the primary sites have not yet been identified.

Despite the hydroid fauna of the Mediterranean Sea being considered one of the best known in the world, the eastern basin of the Mediterranean Sea remains nearly unexplored. This paper reports on 38 species collected along the Levant Sea coast (mainly Lebanon), of which three are new records for the Mediterranean and nine for the Levant Sea. Six alien species, i.e. Eudendrium carneum, Sertularia marginata, Sertularia techocarpa, Macrorhynchia philippina, Diphasia digitalis and Dynamena quadridentata, are described in detail and illustrated on the basis of Levant Sea material. The last four species are considered as immigrants from the Red Sea. The synonymy of Sertularia stechowi, described from Japan, with S. techocarpa is established. Taken as a whole, the collection comprised a majority of circum-(sub)tropical species, and a reduced proportion of Atlantic–Mediterranean elements and Mediterranean endemics. The ecology (seasonality, depth distribution and habitat preference) of the indigenous species resulted similar to what is known for the more studied western Mediterranean, with some exceptions. Adding the present species inventory to the scanty published information, the total of hydroid species known from the Levant Sea rises to 70, indicating the need for future investigation in this sector of the Mediterranean Sea.