This is the first comprehensive check-list of the diatoms of the British Isles to cover all currently reported taxa from freshwater, brackish and marine habitats. It contains a classification of the genera in order of families, followed by a complete list of species and lower taxa set out in alphabetical order within each genus.

The two main orders of the British Diatomaceae are represented in:- 5 sub-orders, 20 families, 3 sub-families, 152 genera, 1798 species, 6 sub-species, 745 varieties and 73 forms.

The check-list also includes 2048 synonyms formerly in common use, together with 512 cross references to the names of taxa in current use.

A survey of the gastropod Nucella lapillus around the south-west peninsula of England has revealed that the incidence of ‘imposex’, the induction of male sex characters in the female, is widespread, that all populations are affected to some degree and that the phenomenon is most prevalent along the south (Channel) coast. Populations close to centres of boating and shipping activity show the highest degrees of imposex, especially those within the vicinities of the Helford, Fal, Salcombe and Dart estuaries and in Plymouth Sound and Tor Bay. Within Plymouth Sound the degree of imposex increased markedly between 1969 and 1985, coinciding with the introduction and increasing usage of antifouling paints containing tributyltin (TBT) compounds.

The long-term monitoring of two stations, 55 and 80 m depth, from 1971 to 1985 shows clear evidence of periods of stability interspersed with periods of change. These periods were identified by several different multivariate methods and persistence stability was quantified by the use of a between years similarity index. A short period of change at the shallow station, 1972–3, was followed by a prolonged period of stability 1974–80. The period 1981–3 witnessed a second period of change with rising total numbers and biomass with some evidence of a downward reversal in 1984–5. The deep station exhibited an essentially similar response except that the stable period 1974–80 was broken into two sub-periods 1974–6 and 1978–80 due to sequential changes in the dominant species which were regarded as evidence of biological interaction with the activities of the polychaete Ophelina acuminata possibly playing a key role. The shallow station showed little evidence of biological interaction and the majority of the species have exhibited similar responses throughout. The general rise in numbers and biomass at both stations is regarded as evidence of intermittent changes in organic flux to the bottom from the water column. The winter temperature fluctuations were shown to have short-term, but significant, effects on the diversity of the communities, bringing about year to year changes in the equitability and dominance.

In the period 1973–80, the infauna at the standard 55 m station exhibited a high degree of persistence stability. The period was characterized by a stable biennial cycle in total numbers of individuals and substantial stability in species ranking. The biennial cycle was associated with density dependent mortality which appears as the principal controlling factor of the community. Evidence is discussed in support of the hypothesis that the density dependent mortality is due to interspecific and intraspecific competition, in a food limiting environment, between species with rather broad niche overlaps.

Measurements of gill dimensions in relation to body weight have been carried out in a mudskipper, Boleophthalmus boddarti. The data was analysed with respect to body weight using logarithmic transformations (log Y = log a + b log W). The slope (b) of the log/log regression lines for the gill area, total filament length, average number of secondary lamellae/mm, bilateral area of an average secondary lamella, and total gill area/g were 1·0496, 0·427, -0·229, 0·851 and 00496 respectively.

These results indicate variations in growth patterns for the different dimensions of the gills. The analysis shows that the increase in gill surface area with the body size is mainly due to an increase in the area of individual secondary lamellae and, to a lesser extent, an increase in filament length and total number of lamellae.

The average weight-specific area for 14 specimens measured (3·6–35·4 g) was 108–15 mm2/g. This value is consistent with results obtained with some other intertidal species.

Marked differences were found in the thickness of the water/blood barrier, which is thinner around the marginal channels. Morphometric diffusing capacity taking this heterogeneity into account was estimated as 0·0208 ml O2 min1 mmHg−1 kg−1.

INTRODUCTION

Morphological studies on the gills of many fish have shown adaptations of the basic structure which can be related to the particular mode of life. Among these adaptations, air-breathing species show many remarkable structural modifications (Munshi, 1976), which extend to the gills forming air sacs in species such as Heteropneustes fossilis (Hughes & Munshi, 1979). Fish which inhabit the intertidal zone, like other seashore animals, are subjected to periodic exposure to air, which may produce problems of water loss and reduction in support for the gills, with consequent collapse and restriction of gas exchange surfaces.

The distribution of free neuromasts and the formation of the lateral line canals are described for two species of flatfish (plaice, Pleuronectes platessa L., and turbot, Scophthalmus maximus L.) during development from the bilaterally symmetrical larva to the bilaterally asymmetrical adult. On hatching plaice have three free neuromasts per side compared with six in turbot. After feeding is established plaice have 40–60/side compared with 20–25 in turbot. During development the ‘hillock’ of sensory cells increases in size and the cupulae grow in length. Canal formation starts later in plaice than in turbot. During metamorphosis the canal system becomes more concentrated in the upper (eyed) side of both species, but lateral line canals occur both on the head and body regions of the blind side. In plaice the tubes leading from the canals to the surface have typically one pore/tube, whereas in turbot there is much branching with 8–10 pores/tube.

A rare physonect siphonophore, Lychnagalma utricularia (Claus, 1879), is redescribed from 24 specimens collected in the region of the Bahamas by the submersible D.S.R.V. ‘Johnson-Sea-Link II’. It was the most common siphonophore collected by the submersible, using its sophisticated sampling techniques. The paucity of previous records for the species, and thus its apparent rarity, is probably due to the extreme fragility of the animals which causes them to disintegrate on contact with nets. The status of the second species, L. vesicularia Haeckel, 1888, is reviewed and it is concluded that it should be reduced to a junior synonym of L. utricularia.

The effect of two 70 W underwater electric lamps on the catch rate of a commercial bottom otter trawl was determined by comparative trials both at night and in daylight. It was found that, although the overall numbers and weights of fish caught did not differ, most of the species which were caught in large enough numbers for a judgement to be made showed a reaction to light. Three species, Trachurus trachurus, Merlangius merlangus and Trisopterus minutus were attracted and four species, Eutriglagurnardus, Micromesistius poutassou, Merluccius merluccius and Limanda limanda were scared off by light.

The possible use of lights to further the development of selective commercial bottom trawling by attracting or scaring particular species is discussed.

The alimentary tract of the common dogfish, Scyliorhinus canicula L. was examined for the presence of gut associated lymphoid tissue (GALT). GALT was present in the buccal cavity, oesophagus, pyloric stomach, intestine containing the spiral valve, rectum and cloaca, but absent from the cardiac stomach. In the intestine containing the spiral valve the highest levels of GALT were recorded. The GALT occupied three tissue niches: as individual leucocytes in the lamina propria as accumulations in the lamina propria and as individual leucocytes in the ephithelium. Four leucocyte types were identified lymphocytes, granular cells, macrophages and plasma cells. The presence of lymphoid tissue at such high levels in the gut suggests it has a potentially important immunological function.

Killary Harbour is a fjord-like inlet on the west coast of Ireland and is an important site for suspended culture of mussels. As part of a study of the production ecology of the inlet, the zooplankton fauna was sampled quantitatively at two week intervals, between February 1981 and January 1982 using nets with mesh apertures of 90 and 335 μm. The dominant holozooplankton species of Killary Harbour are typical of inshore or neritic waters but there are also representatives of estuarine and oceanic faunas. Inflow of water into the bay below the surface layer of low salinity apparently maintains conditions suitable for neritic species and accounts for similarities between the zooplankton faunas inside and outside the bay. Large populations of estuarine species presumably do not develop because of the variability of freshwater discharge. During September 1981 there was evidence of an intrusion of oceanic water into the bay.

The post-larval shell and hinge development of the bivalves Abra alba (Wood), Tellina fabula Gmelin and Donax vittatus (da Costa) from the recently metamorphosed size to a juvenile size of 1·2–1·4 mm shell length has been examined using scanning electron microscopy. Early post-larval development in the stages up to 1·0–1·2 mm size can involve considerable morphogenetic change and requires careful description with photographic developmental series. The form of the pediveliger larva is present in the early post-larval shell and confirms the identity of the larvae of A. alba and T. fabula. The veliger and pediveliger larvae of A. alba are described. The similar larval form of the tellinacean bivalves is modified by differential margin growth early in post-larval development. Comparison of these bivalves with allied species reveals that the post-larvae are distinguishable at even the smallest sizes by the shell and hinge form. The metamorphic size of A. alba ranges from 0·26 to 0·31 mm, of T. fabula from 0·25 to 0·28 mm and of D. vittatus from 0·25 to 0·35 mm. The bivalve post-larvae were collected from the shallow sublittoral of Oxwich Bay, Bristol Channel, U.K., and the larvae from the overlying waters, during the years 1980–2.