In the years 1921 and 1922 a series of experiments on the rearing and hatching of the species of Rays and Skates occurring on the English side of the western end of the English Channel was carried out at the Laboratory of the Marine Biological Association, Plymouth. The egg-capsules were collected from fish landed at the Barbican at Plymouth and from fish captured by the Research steamers, Oithona and Salpa. The egg-capsules were kept in the circulation of sea-water in the tanks at the Laboratory, and for six species the period of incubation under these artificial conditions was determined.

As the processes by which epiphytic bryozoans become established in aggregations on intertidal algae become more clearly understood, it is necessary to consider some of the ecological consequences of non-random settlement. The adaptive significance of aggregation in epiphytic bryozoans has been discussed recently by Hayward & Ryland (1974), who also showed how the worst effects of overcrowding are mitigated. Acorn barnacles and spirorbine tubeworms have evolved a specific behavioural pattern which results in regular, spaced-out settlement within aggregations, thus allowing room for each individual to become established and begin growing. By contrast, epiphytic bryozoans do not exhibit this kind of behaviour (Harvey, Ryland & Hayward, in preparation). Al-though a minimum size is probably required before the colony is able to breed, the pattern of growth observed for Alcyonidium hirsutum shows that this can be achieved through lability of growth direction. The linear relationship found to exist between colony size and fecundity shows that no advantage is conferred by increased size; the smaller colony is as effective in reproduction as the larger. In the present paper two other ecological consequences of aggregated settlement are considered: mortality and size.

In order to examine the variation of migratory histories in the Japanese eel, Anguilla japonica, we measured otolith strontium (Sr) and calcium (Ca) concentrations by X-ray electron microprobe analysis in A. japonica collected in a coastal brackish water lake in the northernmost part of its distribution. Two migratory types that were categorized as river eels and estuarine eels were found. Estuarine eels were dominant (85%), while ordinary diadromous eels that had entered the freshwater habitat made up only 15% of the population. The low proportion of river eels suggested that the estuarine eels that inhabit the nearby coastal areas might make a larger reproductive contribution to the next generation in this area. There was no significant difference in growth between the river and estuarine eels, which suggested that the limited carrying capacity of the adjacent river and geographical features might be more effective in determining the habitat use of the Japanese eel than the genetic feature and food abundance at the northern edge of its distribution.

Two species of the genus Pseudopolydora, Ps. dayii, sp. nov. and Ps. antennata, were associated with gastropods on the south and south-east coasts of South Africa. Pseudopolydora dayii is characterized by prominent post-chaetal notopodial lobes on chaetiger 1 with very long chaetae, a prominent occipital tentacle, having hooded hooks that start on chaetiger 9, branchiae that start on chaetiger 6, stout hooks and lobes placed latero-posteriorly to the hooded hooks in posterior chaetigers. It is a surface-fouler and was found on several species of wild gastropods at four of the five sites sampled and from additional material from the south-west coast and on cultured abalone (Haliotis midae) at a farm on the south-west coast. Three individuals of Ps. antennata were found only with oysters at the easternmost site. This was the first record of this species outside of the Western Cape Province and it is possible that their association with the oysters was fortuitous.

A cumulative species description curve (from 1830 to 1995) is given for open water marine fauna in excess of 2 m long in the major axis of the body. This curve has not yet closely approached its asymptote. Estimation by maximum likelihood fit of a hyperbola suggests a maximum of some 47 species awaiting formal scientific description and an approximate current rate of description of one new species every 5·3 years. Consideration of the most recently described species and recent observations by field workers suggests that any imminent species descriptions are most likely to be cetaceans.

The hindgut caecum of the deposit-feeding echinoid Echinocardium cordatum harbours a symbiotic bacterial microflora, organized into layered mats around detrital particles owing to the proliferation of filamentous bacteria. The bacterial community was analysed using 16S rRNA gene analysis and fluorescence in situ hybridization. The purpose was to characterize its biodiversity and to identify its predominant members. The majority of the 16S sequences belong to the δ-Proteobacteria (61.5%), the Bacteroidetes and the Firmicutes constitute the two other main bacterial groups (respectively 23.1% and 15.4%). A total of 41% of the δ-Proteobacteria clones isolated belong to a bacterium of the genus Desulfonema for which a specific oligonucleotide probe was designed, enabling identification of its distribution in the nodules.

In recent years attention has been given to the influence of electrical currents as fish deflectors or screens, and experiments have been made to determine the magnitude of the currents which are sufficient to paralyse or act as deterrents to fish which may enter the electrical field, but in such strong fields the perception of the mechanism by which fish respond to electric currents is masked by the paralysis produced. It seemed possible that experiments with very weak currents might give fuller information concerning the mechanism by which fish respond to electrical stimulus than those made in strong fields. There is also the possibility that weak electric currents may occur in nature to which fish respond, but before exploring that field of phenomena it is necessary to observe the behaviour of fish under the influence of very weak fields. McMillan found that the field (volts per inch) required to paralyse young salmon varied with the resistivity of the water; thus when the latter was 10,000 ohms per inch cube the paralysing voltage was about 1·5, so that a current density of ampere per square inch was sufficient to cause paralysis, whereas when the resistivity was twelve ohms per inch cube the current required was ·03 ampere. In the former case the conductivity of the fish was greater than that of the water, in the latter case less.

Studies on the opisthobranch molluscs inhabiting the continental platform in areas not accessible by SCUBA diving are rare in the subtidal bottoms of the Iberian Peninsula. Data obtained from trawls are not adequate for quantitative analysis, due to the indirect method used and the high number of variables which affect the capture of the samples. However, with the aim of obtaining qualitative information on the opisthobranch molluscs inhabiting the subtidal trawling grounds off Blanes, we took more than 500 samples over a two-year period, on the non-commercial fraction of the trawling fisheries, finding opisthobranchs in 306 samples. We analysed samples from 16 trawling sites, at depths between 50 and 300 m, by using ten fishing boats of the ‘Confraria de Pescadors del Port de Blanes’. We obtained 4.295 specimens of opisthobranchs belonging to 29 species. From these, 4 are Cephalaspidea s.s., 1 Anaspidea, 1 Umbraculacea, 3 Pleurobranchacea and 20 Nudibranchia (3 Arminina, 3 Dendronotina and 14 Doridina). The most abundant species were Gastropteron rubrum and Scaphander lignarius, both cephalaspideans present during all seasons, and the dendronotacean Tethys fimbria. For Scaphander lignarius it was possible to distinguish three size-groups, from which the smallest one was usually found in summer. Other interesting species found were, among others, Armina tigrina, Baptodoris cinnabarina, Thordisa filix and Kaloplocamus ramosus. The richest trawling grounds in species numbers and abundances were La Planassa and Els Capets. The total number of opisthobranch species reported for the trawling grounds off Blanes is now 48.

Twenty-five years ago I published a note (Atkins, 1929) on a then unnamed member of the Saprolegniaceae, a destructive fungal parasite of the pea-crab, Pinnotheres; the name Leptolegnia marina is now proposed for this fungus.

The population structure and fecundity of the hermit crab Dardanus deformis were studied. Monthly samples were obtained between January and December 2003 at Costa do Sol, Maputo Bay, southern Mozambique. A total of 604 individuals was analysed of which 273 were males, 164 non-ovigerous females and 167 ovigerous females. The overall size–frequency distributions were unimodal, with males reaching larger sizes than both ovigerous and non-ovigerous females. Females were slightly more abundant than males, but the overall sex ratio did not differ significantly from 1:1. Dardanus deformis showed continuous reproduction throughout the study period. A small number of juveniles was obtained, suggesting that recruitment may take place in a different habitat than that occupied by the adults. The egg number increased with female size, and the high incidence of ovigerous females, may suggest a higher reproductive activity probably as a result of the rapid embryonic development in the study area.

Ciliates are a primary component of the periphyton microfauna and play a crucial role in the functioning of microbial food webs. Seasonal variation in community structures of periphytic ciliate communities was studied, using glass slides as an artificial substratum, during a 1-year cycle (August 2011–July 2012) in coastal waters of the Yellow Sea, northern China. Samples were collected monthly at a depth of 1 m from four sampling stations. A total of 144 ciliate species representing 78 genera, 43 families, 17 orders and eight classes were recorded. Among these species, 31 distributed in all four seasons, while 11, 11, 13 and two forms occurred only in spring, summer, autumn and winter season, respectively. The species number and total abundance peaked in spring and autumn, with minimum values in winter. Ciliate community structures differed significantly between seasons, and were significantly correlated with the changes in environmental variables, especially temperature, pH, dissolved oxygen (DO) and the nutrients. Of 36 dominant species (top 15 ranked contributors in each season), nine (e.g. Pseudovorticella paracratera, Trochilia minuta and Zoothamnium sp.) were significantly correlated with pH, DO or nutrients. Species richness, evenness and diversity measures were significantly correlated with temperature, pH, DO or soluble reactive phosphates. Results demonstrated that periphytic ciliates exhibited a clear seasonal variation in community structures in response to environmental conditions and potentially might be used as a robust bioindicator for assessing environmental quality status in coastal waters.

When the mean adult length and mean clutch volume of marine turtles are examined, a clear pattern for larger species to lay larger clutches is evident, in accord with predictions that female size constrains the available space for carrying eggs. However, when compared with this general trend, the volume of clutches laid by flatback turtles (Natator depressa) are smaller than expected. The implication is that the unusually flat morphology of flatback turtles, provides an additional constraint on their egg carrying capacity.

The effects of pentoses, hexoses and uronic acids upon the temporary adhesion of cypris larvae of five barnacle species from four families has been studied. A common, concentration dependent, inhibitory effect of D-glucose was observed for the five species, with maximum inhibition (to 60% of control levels) occurring at 10−8M glucose. Using Balanus perforatus larvae, glucose was shown to be acting at the antennular surface, most probably by interacting with polar groups associated with the temporary adhesive. The pentose, D-arabinose, was less active than glucose, reducing temporary adhesion to only ∞80% of control levels. D-glucuronic acid was more active, decreasing adhesion to 60% at 10−9M, whilst two other hexoses, D-mannose and D-galactose, showed similar activity to glucose. We suggest that hexoses interact with the same polar groups in the adhesive, glucuronic acid with the higher activity because of its more polar nature. The pentose possibly interacts with a different, less common, group. Our results suggest that the chemical identity of bacterial exopolymers, particularly in respect of their pentose: hexose and neutral suganuronic acid ratios, may be an important factor in determining the strength of temporary adhesion shown by barnacle cyprids towards bacterial films.

It is our aim in this paper to answer three questions. All of them relate to the well-known ability of lugworms to act as isosmotic osmo-conformers over a wide range of salinities. When exposed to diluted sea water, the body fluids come into osmotic equilibrium with the lowered external concentration, and considerable amounts of water enter the body of the worm. There is no evidence of weight or volume regulation in dilute media, as assessed by a return of the body weight towards its original value. The processes of osmotic adaptation down to the lowest salinity limits for survival include, therefore, tolerance of a lowered osmotic concentration of the body fluids, and of the retention of increased amounts of water in the body. The evidence on which this view of osmotic adaptation in lugworms is based is reviewed by Oglesby (1969, 1973). Additional information on Arenicola marina is provided by Freeman & Shuttleworth (1977).

In order to find the most suitable parameter for measuring the nereidid Laonereis acuta, correlations between total length or weight and eight morphological measurements: width of prostomium and 2nd, 6th, 13th and 19th setigers, length of the prostomium, length through segment 6th and length through segment 13th, were established. The width measurements showed the highest values of r, and were the most reliable indicators of size. Comparisons between weight and morphological measurements showed a similar pattern as well as negative allometric growth.

The sea stickleback, Spinachia spinachia, lives in shallow coastal and estuarine waters where the male builds a nest and undergoes a protracted period of parental care. The accumulation of silt in the nest has been suggested as one of the environmental factors that regulate nest-directed activities during the parental phase. Experiments have quantified the behaviour of the male fish before and after the application of silt to the nest and shown that some behaviours are affected. The fanning activity, attendance at the nest and other nest-directed activities were examined and it was found that nest inspection and nest pushing increased significantly following the application of silt. Fanning activity, a major part of the parental behaviour of the sticklebacks, was unaffected by the experimental treatment and seems to be unresponsive to environmental changes. The results are discussed in relation to the functional significance of parental behaviour, and compared with a closely related species.

The effects of sublethal tributyltin (TBT) concentrations on the growth and development of Ruditapesdecussatus larvae were studied. Veliger larvae of R. decussatus were exposed to TBT nominal concentrations of 25, 50, 75 and 100 ng Sn l−1 in the water for a period up to 13 d. Larval growth and development were chosen as endpoints for evaluation of TBT toxicity. Growth of R. decussatus larvae was severely affected by TBT concentrations (25–100 ng Sn l−1). A 3- to 6-fold reduction growth was observed in these early larval stages. Furthermore, R. decussatus larvae exposed to TBT did not develop further than D-larvae while the unexposed ones reached the umbonated stage.

The effects of polychaete (Lysidice ninetta, L. collaris, Nematonereis unicornis (Annelida: Polychaeta)) and limnoriid isopod (Limnoria tuberculata (Crustacea: Isopoda)) borers in the Mediterranean sea grass Posidonia oceanica (Potamogetonaceae) were assessed in the meadows of Olbia and Genoa (western Mediterranean Sea). Borer invertebrates were mainly found into the old leaf sheaths of the sea grass. At Olbia, a mean density of borers (202.6±34.8 ind m−2) significantly higher than at Genoa (23.2±7.3 ind m−2) was observed. In 3.3% of samples from Olbia, large polychaetes and isopods were also observed boring into living plant tissues. Only fractions from 0.8—3.9% of the sheath production was actually removed by borers at the two studied meadows. The fact that sheath weight loss with time was higher at Genoa than at Olbia regardless of the presence of borers suggests that other factors than the activity of such organisms are important in the sheath decay process.

Hexactinellids or glass sponges constitute a predominantly deep-sea sponge group typically occurring at bathyal and abyssal depths. Some species form dense populations along the European and African continental slope but the distribution and extent of these populations remains ill known and the driving factors behind their occurrence poorly understood. Here we report an aggregation of the hexactinellid sponge Poliopogon amadou Thomson, 1878 at ~2700 m depth on the Great Meteor seamount, a large seamount located southern of the Azores archipelago. A description of the species, along with scanning electron microscopy of its spicules, is provided.

The aim of the study was to evaluate the effectiveness of the application of multiple environmental descriptors through an asymmetrical sampling design to detect possible impacts related to the Costa Concordia event on the coastal marine environment. The Costa Concordia shipwreck occurred on a submerged rocky reef in the north-western Mediterranean Sea and the wreck was removed 2 years later. To achieve the proposed objective two main coastal ecosystems, the seagrass Posidonia oceanica and coralligenous assemblages were studied using two ecological indices, PREI and ESCA, respectively. Both indices show a lower ecological quality in the disturbed sites compared with the control ones. Differences between the disturbed and control sites observed in both studied ecosystems would seem to indicate an increase of turbidity around the shipwreck as the most plausible cause of impact. The concurrent use of different ecological indices and asymmetrical sampling designs allowed detection of differences in ecological quality of the disturbed sites compared with the controls. This approach may represent an interesting tool to be employed in impact evaluation studies.