The aim of this study was to test the effective separation of shape indices of otoliths of three species belonging to the family Sciaenidae before and after in vitro digestion. We measured 328 sagittal otoliths and applied six shape indices. Before the experiment, the aspect ratio (otolith height/otolith length%), circularity, ellipticity and relative surface of the sulcus acusticus were suitable for differentiating the species of genera Paralonchurus and Stellifer. Among the species of Stellifer, the aspect ratio and rectangularity were suitable. Otoliths exposed to in vitro digestion showed no significant differences in their morphometry before and after the experiment. After in vitro digestion, the aspect ratio and circularity were effective in separating Paralonchurus and Stellifer. However, none of the indices used in the present study were efficient to separate otoliths of congeneric species after in vitro digestion.

Data are presented on the growth rate of Verruca stroemia under natural conditions and when exposed continuously and cleaned repeatedly. Several series exposed at different times of the year were followed.

Rapid growth takes place (under raft conditions) following settlement; the maximum size is virtually reached in one season's growth between spring and early winter. There is little growth in midwinter.

Differences between the mean specific growth rates of the various series can be ascribed to differences in the availability of food.

The question is discussed as to whether there is any seasonal rhythm; the evidence indicates that no marked rhythmic pattern of growth exists.

Observations on deep-water populations would be of value for comparison and to unmask any relatively weak rhythmic growth.

The mean specific growth rates at half their maximum size are compared for several species—Balanus balanoides, B. crenatus, B. balanus, Chthamalus stellatus and Verruca stroemia; it is similar for all species except Chthamalus stellatus. The high level barnacle may require stimulation such as is provided by wave action to elicit full metabolic activity.

Ascidian development is reviewed and a model is presented for specification of the larval body plan and cell fate during embryogenesis. The model involves the combined activity of determinants inherited from the egg and inductive cell interactions in the embryo. It is suggested that there are four determinant systems in the egg which are segregated to different blastomeres during cleavage. The ectodermal, endodermal, and muscle determinants specify cell fate autonomously, while the axial determinants initiate cell-shape changes at gastrulation and generate a cascade of inductive activities establishing the larval body plan. In the proposed signalling cascade, the endoderm induces notochord by generating a planar inductive signal late during the cleavage phase, and the notochord cells in turn induce the nervous system by generating a vertical inductive signal in the overlying ectoderm during gastrulation. Ultraviolet (UV) irradiation experiments are described which suggest that axial and muscle determinants exhibit UV-sensitive components resembling nucleic acids and proteins, respectively. The model is evaluated in terms of developmental changes during the evolutionary transition from indirect to direct development. This transition can be explained according to the model by loss or inactivation of the muscle determinants and modification of the inductive activities generated by the axial determinants. These changes are supported by recent studies of embryogenesis in direct-developing ascidians.

The relation of moisture content, temperature, nest depth, incubation, distance from sea and vegetation to hatching success of loggerhead sea turtles, Caretta caretta, in Turkey was studied. Nineteen randomly selected clutches were examined. Moisture was found to be negatively correlated with distance from the sea (P<0·05) but positively correlated with temperature (P<0·01). Temperature was negatively correlated with incubation time. Hatching success was not correlated with any of the environmental factors examined.

The relationship between the ciliate community and the environmental variables in Ushuaia and Golondrina bays (54°79′S 68°22′W and 54°85′S 68°36′W, respectively) in the Beagle Channel, Argentina was investigated. The study was performed in three zones within the bays, previously delimited on the basis of their water quality. The most perturbed sites were located inshore. In order to analyse the contribution of each species to the similarity or dissimilarity between zones, similarity percentages analysis was undertaken using the Bray–Curtis similarity index. The variations in species composition and dominance in the selected zones were examined by the abundance–biomass comparison plot. We also studied the relationship between environmental and ciliates variability. The ciliate community comprised a total of 43 species belonging to 15 genera. Ciliate abundance and biomass varied temporally and spatially. A more diverse community dominated by small and opportunistic species tolerant to environmental changes was found in the most perturbed zone, while in the less stressed zone the community comprised bigger species, probably adapted to more stable environmental conditions. A community comprising species from both zones was found in a transitional area. We conclude that the structure of the community varied closely with environmental conditions.

The observations of Schlieper (1929) established the lugworm Arenicola marina (L.) as an osmoconformer which remains virtually isosmotic with the external medium over a wide range of salinities. In a recent comprehensive review of salt and water balance in lugworms, Oglesby (1973) describes ‘the extensive swelling associated with transfer of lugworms to lower salinities’, and ‘when maintained in salinities lower than about 50% s.w. in the laboratory, lugworms are rendered incapable of such vital physiological activities as burrowing and burrow ventilation’. Under these conditions, lugworms exhibit little or no ability to regulate their volume or water content.

Geographical information system analysis was applied to assist in the re-identification of records of Chaetozone setosa from the north-east Atlantic. Previously this species was considered to have a world-wide distribution. The aim of this study is to clarify and illustrate the distribution patterns associated with sediment and water characteristics of C. setosa and other Chaetozone species.

Diversity is one of the most frequently used attributes of ecological communities, and there is a long-standing discussion about their adequate use, calculus and interpretation. One of the most conspicuous and simple diversity estimators is species richness, but it has been criticized by recurrent pitfalls, which has biased comparisons and the testing of hypotheses. Otherwise, synthetic ecological indices of diversity are difficult to interpret due to the underlying complex or cryptic concepts. Most of the studies in soft-bottom macroinvertebrate communities trying to estimate species richness, have actually quantified species diversity as species density; the number of species per unit area. In the present study, the diversity of a tropical Pacific soft bottom community is analytically decomposed using two null models to assess species richness and evenness, and the slope of species–area curves to estimate species density. A declining trend of species richness was observed along a 2-year period and could be related to the cumulative effects of interannual environmental variability and fishing disturbance. The species–area relationship could be considered a good indicator of spatial heterogeneity, specifically to illustrate the depth gradient. Local abundance was negatively correlated with evenness, showing that high-density communities are the result of increases in abundance of a few dominant species. Here we demonstrate that seasonality, depth and abundance could explain diversity in soft-bottom macroinvertebrate communities of coastal waters and propose a robust procedure to survey diversity as a part of monitoring programmes of coastal management.

The fecundity of Liocarcinus depurator (Decapoda: Brachyura) in the Ría de Arousa (Galicia, north-west Spain) and the reasons why it fluctuates were analysed, comparing the results with data available from other geographical areas. The incubation of L. depurator eggs in the Ría de Arousa generally takes place between January and September, although ovigerous females can be found all year round. The number of eggs per brood in L. depurator varied considerably in the Ría de Arousa and ranged from 5265 (carapace width (CW=31·3 mm, stage III) to 203,724 (CW=44·6 mm, stage I). The allometric equations adjusted to fit each egg development stage indicated that there was a strong positive correlation between female body size and the number of eggs the animal is able to bear. Female body size, measured as the carapace width, was the main factor causing variability in the fecundity of L. depurator. The second most important cause of variability in the development stages of the eggs was the number of eggs per brood, which may be due to the gradual loss of eggs that occurred during the incubation of these eggs in the female abdomen. Temporal changes constituted another significant factor in the variability of the fecundity of L. depurator. The allometric equations (log F=log a+b×log CW) fitted to each month and development stage I presented changes in the slope which point to the existence of a temporal evolution in the number of eggs. In the Ría de Arousa and for all the development stages, L. depurator was found to have a significant negative correlation between the number of eggs per clutch and egg volume. Egg volume also correlated negatively with the size of the female in stages I of the egg development. The degree of correlation between the volume and number of eggs was greater than the correlation between volume and size. The main cause of the variability in the egg volume of L. depurator in the Ría de Arousa may be attributed to the development stage (ANCOVA, P<0·001).

The ovary structure of the hermit crab Diogenes pugilator (Crustacea: Decapoda), is described in the different phases using electron microscopy. Sexual maturity was reached at a very small size; females from 0.74 mm shield length (SL) could be found in vitellogenesis stage and even 0.6 mm SL ovigerous females exist. The biometric study of the ovigerous females by independent size-class (non-accumulative) shows that 1.3 mm SL is the size at which 50% of females are ovigerous; this value is increased a little (1.7–1.8 mm) if the population of females, or ovigerous females, is analysed from an accumulative point of view. In addition, an optimal reproductive size (between 2.1 and 2.3 mm SL) and a reproductive decrease in the maximum size-classes have been detected. The relation between brood size (measured through egg number) and the hermit crab size follows a potential function. The number of eggs by brood varies in a wide range (9–2838), with a mean diameter of 0.35±0.03 mm. No relationship between egg size and shield length has been found.

A description is given of Alcyonidium reticulum sp. nov. (Bryozoa: Ctenostomatida), a smooth-surfaced species found encrusting intertidal stones and on Fucus serratus in south-west Britain. It is distinguished from two superficially similar congeners, A. gelatinosum and A. mytili.

Length composition, maturation and growth of the ommastrephid squid Todaropsis eblanae were studied using length–frequency distributions (LFDs) and statoliths of squid caught off the north-west African coast. Length–frequency distributions were quite similar in all seasons studied, indicating all year round spawning. However, both high proportions of mature squid in the winter and the hatching peak of squid from our sample in spring suggested the winter–spring peak of spawning. Immature and maturing squid had rather high growth rates, attaining 140—150 mm of dorsal mantle length (ML) by the age of 160—170 d. Todaropsis eblanae is likely to have an annual life cycle on the north-west African shelf.

Divisional morphogenesis of the marine hypotrichous ciliate, Tachysoma ovata was investigated based on protargol impregnated specimens. Its morphogenesis reveals the following peculiarities: (1) there is a definite period during which the anterior part of the newly formed adoral zone of membranelles (AZM) in the opisthe connects with the parental AZM which remains unchanged during the morphogenesis. (2) The anlagen of left and right marginal rows do not develop simultaneously. (3) The replication processes of macronuclear segments are not recognizable during cell division. It is likely that the replication takes place during the interphase. (4) The origin of the fronto-ventral-transverse (FVT) cirral anlagen in the opisthe is characteristic: in other Tachysoma spp. these primordia are generated either from differentiated parental ciliatures (or are orientated by pre-existent organelles), or by division of the proter's FVT-cirral primordia. (5) The primordium of the undulating membranes in the proter always keeps the form of two streaks (so-called ‘semi-anlagen’). There is no conspicuous dedifferentiation or reorganization of the undulating membranes. A morphogenetic comparison with other species of this genus was carried out.

Coxal plates 1–5 of Epimeria cornigera form a closely interlocking series keyed by the head such that ventral flexion of the peraeon is severely curtailed. The clamp formed by coxae 4 and 5 is interpreted as an adaptation facilitating copulation in a species with feeble gnathopods and non-prehensile antennae. The morphology of the posterior three pairs of peraeopods can also be regarded as an adaptation for gripping the female. Other possible functions (e.g. predator deterrence and feeding grip) of coxal structures are also examined.

Until recently there has been very little information on the quantities of phytoplankton nutrients in the Irish Sea. Slinn (1958–1966) has reported the weekly variations in the nutrient concentrations at a station off Port Erin, Isle of Man, and studies on the nutrient conditions in the Menai Straits have been carried out by Jones (unpublished) and Ewins & Spencer (1967). Liss (1969) has reported on the results of winter surveys of reactive silicate near the Irish coast, and from three stations near the Welsh coast (Anglesey, the Lleyn Peninsula and Fishguard). The present paper describes studies carried out in the inshore waters near Aberystwyth in Cardigan Bay during 1967 and 1968. This investigation formed part of a study of the seasonal occurrence of the phytoplankton and the growth conditions in this shallow, inshore region.

Analysis of the total copper and zinc content of four species of talitrid amphipods, Orchestia gammarellus, O. mediterranea, Talitrus saltator and Talorchestia deshayesii throughout a complete spring/neap tidal cycle failed to reveal any significant effects of moulting upon body copper or zinc in any species. Moulting was synchronized to the lunar cycle only in T. saltator, taking place 5–7 days prior to a new moon. The fact that no significant changes in body metal concentrations took place with the moult cycle is discussed in relation to the use of talitrid amphipods in copper and zinc biomonitoring programmes.

The results of analysis of sea water samples from the International Hydrographic Station E1 (500 02' N., 40 22' W.) are given in graphical form and as integral mean values for the water column of 70 m. Winter maximum values (in January) of 044/xg atom phosphate P/l. and 0-53^g atom ' T o t a l ' P/L, with 315/xg atom Si/1, were found. The phosphate and total phosphorus concentrations were unusually low. The spring decreases were 0-21/xg atom P/l. and 272 fig atom Si/1.

The collection of Decapoda made by the Huxley during her short cruise on the north side of the Bay of Biscay is an extensive one; it comprises no less than forty-nine species—a number which speaks well for the efficiency of the gear employed.

Haliotis tuberculata L. densities and population distributions were assessed for 13 sublittoral sites around the coasts of Jersey, Channel Isles using SCUBA techniques. Twenty 1 m2 quadrats were assessed at each site at 5 m below lowest spring tide level (LSTL). Mean densities at each site ranged from 0·05 animals m−2 to 2·35 animals m−2, while the overall mean for the whole island was 0·79 animals m−2 (s.e.=0·24). Population density (D) declined with increasing mean animal length (LTH). The slope of the equation relating loge D to loge LTH was -6·92. Data collected at 2 m, 5 m, 8 m and 10 m below LSTL at two sites showed no trend in mean animal length with depth at one of the sites, but it did increase slightly with depth (1·3 mm nr−1) at the other.

Taschenberg (1879) briefly described, under the name of Didymozoon scombri, a trematode which he recorded as occurring in pairs in cysts on the inside of the gill-covers of Scomber colias at Naples. Odhner (1907) found what he believed to be the same species not uncommonly in small specimens of S. scombrus off the west coast of Sweden, but was unable to find it in the larger fish taken in the early summer. He gives a minute description and excellent figures of the worm. Johnstone (1914) has also given a good, though diagrammatic, figure of its anatomy. Odhner describes the worm as occurring most commonly in paired cysts on the upper pharyngeal bones, but also in exceptional cases in cysts on the inside of the gill-covers and on the outside of the head, close behind the eye. About half the cysts examined by him contained two worms, the rest from three to seven. Johnstone describes the cysts as being most commonly situated ” “on the roof of the mouth beneath the pharyngo-branchials”, but also sometimes on the basi-branchials, on the external surfaces of other parts of the gill-bars, or on the internal surface of the operculum. One cyst contained as many as sixteen worms. According to Dollfus (1926), he and Monod found cysts containing one, two, three or more worms in the mucosa of the mouth, palate and gills of S. scombrus, and also single unencysted worms under the transparent skin behind the eye.

Thus at least two authors record the same worm as occuring both inside the mouth and on th e outside of the head, behind the eye.