Sea trials, using baited pots (inkwell and French barrel) and nets (tangle and gill), were conducted for the spider crab Maia squinado off the west coast of Ireland from November 1978 to July 1980. A series of laboratory pot trials using inkwell pots were performed. Diving observations were made on the fishing grounds.

Catch per unit effort rose to a summer peak and decreased in autumn. There was no difference in size composition or sex ratio of the catch between the pots and nets. Mature males predominated in the catch with the highest male:female (M:F) ratios recorded in summer. Immatures were virtually absent from the catch. Segregation on the basis of sex and maturity appears to occur in summer. Mature males were found at about 10 m, in sandy areas with rocky outcrops. Mature females occurred at about 5 m, on a sand and shell gravel bottom with rock and weed (notably Laminaria). Immatures were rare and occurred just below the intertidal. The M:F ratio was lowest during the periods of the onshore and offshore migrations. Berried females were recorded from March to September with one brood produced each year.

Laboratory pot trials showed increased aggression among spider crabs in the presence of baited pots. Males drove other males away from pots and divided their time between agonistic encounters and searching. Females were not driven away and did not engage in aggressive encounters. This behaviour, and the observation that large males could reach the bait through the pot bars, possibly explains the absence of larger and smaller males from the pots.

Homogenates of pyloric caeca, gonads, spermatozoa and eggs from the starfish Asterias rubens were fractionated by gel filtration chromatography.

It appeared that a glycolipoprotein fraction, present in oocytes and gonads of female animals, is absent in spermatozoa and gonads of male animals.

The possible role in vitellogenesis of this fraction and of a more omnipresent one is discussed.

Material from Loch Fyne referable to Monoculodes gibbosus Chevreux (Oedicerotidae) has been discovered in the Reference Collection at Millport originally labelled by David Robertson as M. stimpsoni Bate. This is the first British record of this little known species. A detailed redescription is provided and comparison made with French material (including the holotype). A revised key to the British species is presented.

Aora spinicornis Afonso is recorded for the first time from the British Isles. Two species of Aora, A. gracilis (Bate) and A. spinicornis Afonso are now known from these waters. A. typica Krøyer, long considered a British and Irish species, is actually known only from the Southern Hemisphere. Figures and diagnoses of both species are provided together with a key to their identification.

Introduction

Lincoln (1979) records one species of Aora Kreyer from British and Irish waters. Due to an oversight (Lincoln, personal communication) he overlooked the paper by Myers (1973) (although listed in the bibliography) and attributed the single species to A. typica Krøyer, a species actually known only from the Southern Ocean between 20° S and 50° S (see Myers & Moore, 1983 which also includes a key to the world species). Two species of Aora are now known from the British Isles: A gracilis (Bate) which is widely distributed, and A. spinicornis Afonso, recently discovered in Lough Hyne, Co. Cork, and herein reported for the first time from these waters. This latter species has a Lusitanian distribution (Azores, Canaries, Mediterranean) and may occur in south-western England and Wales, but has been confused previously with A.gracilis (Bate). Both species have been described and figured by Myers (1973, 1982) and do not require further detailed analysis. However, since both species are now known to occur in these waters and are not both treated by Lincoln's widely used monograph, the two species are figured here as entire specimens (for details of appendages including mouthparts see Myers, 1982) and briefly diagnosed, and a key is provided to facilitate their identification by British and Irish workers.

A new species of a monogenean Isancistrum subulatae (Gyrodactylidae) has been discovered on the arms and tentacles of the cephalopod mollusc Alloteuthis subulata at Plymouth and I. loliginis, on the gills of the same host, has been re-discovered for the first time since its original description in 1912. I. subulatae, like other gyrodactylids, is viviparous, and has been shown by experiments to transfer to new hosts by contagion. In nature such transfers probably take place during copulation of the hosts and since the parasite may occur in numbers of several thousands per host, it may thereby constitute a venereal disease.

A multinucleate, monopodial, lobose amoeba from a Cornish rock pool was identified as Amoeba flavescens Gruber, 1889, originally described from the Mediterranean. It is the type species of a genus Gruberella. Although its locomotive form and activity resemble those of the uninucleate Vahlkampfiidae and its Golgi system, like that of the vahlkampfiids, is not organized into dictyosomes, its mitotic pattern differs from that of the vahlkampfiids. The presence of mitochondria and other characters distinguish it from Pelomyxa. The only other similar marine amoeba is Hyperamoeba fallax Seravin & Goodkov, 1982, from the Far East. The process of ‘paracopulation’ reported for H. fallax was not observed in the Cornish isolates. Pending more evidence of familial relationships, Gruberella remains incertae sedis within the suborder Gymnamoebia Haeckel, 1862.

By means of capillary gas chromatography (GC) and capillary gas chromatography'mass spectrometry (GC/MS), the aliphatic hydrocarbons, fatty acids, fatty alcohols and 3ß-sterols were identified in saponified lipid extracts of the green alga, Dunaliella primolecta, the copepod, Calanus helgolandicus, and faecal pellets released by the animal when fed in the laboratory on the algal diet. Comparison of the lipid data for faecal pellets with those for the plant showed that marked changes to dietary lipids occur during passage through the gut of the copepod: (1) 17:2, 17:1, and 17:0 hydrocarbons are completely eliminated; (2) polyunsaturated fatty acids (e.g. 16:4 and 18:3) are significantly reduced relative to total fatty acids; (3) evidence of the conversion of phytol to dihydrophytol is observed; (4) C28 and C29 sterols with Δ and Δ nuclear unsaturation are selectively removed from the diet relative to Δ components. The Δ sterols are released unchanged as faecal lipids. Cholest-5-enol, absent from the original diet, is also released in the faecal pellets. These observations illuminate the fate of specific dietary lipids in Calanus and the contribution copepod faecal pellets can make to the overall lipid composition of bottom sediment in many marine environments.

A further series of North Sea demersal fish surveys was carried out during the summers of 1981 and 1982. The remote headline camera was used and the benthos trawled was recorded. At stations of special biological interest the camera was adjusted to take from one to three frames per minute throughout the 1 h duration of the trawl. A successful series of underwater photographs were obtained at 95 stations throughout the North Sea.

Three species of salps (Pegea confoederata, Salpa maxima, and S.fusiformis) from the Western Mediterranean have been analysed for their general biochemical composition and their detailed sterol chemistry. In particular the distribution of saturated sterols in various tissues of the salps has been studied. The results suggests that dietary phytoplankton exerts a major influence on the tissue sterol composition of the salps, although the presence of occelesterol and saturated sterols in the salps cannot be explained on the basis of diet. Possible explanations for the occurrence and distribution of the saturated sterols are considered.

The brittle-star Ophiothrix fragilis forms dense aggregations on the sea bed off Plymouth, as well as in other parts of the English Channel. From about 1970 there was a marked decline in populations off Plymouth, and study of previous records suggests that there have from time to time been considerable fluctuations in abundance of this species — since beds were first reported by E. J. Allen in the 1890s. The decline did not extend to populations in the southern and eastern parts of the Channel. The distribution of Ophiocomina nigra, which sometimes occurs in mixed populations with Ophiothrix, is also described. This species is more or less limited to the western Channel, and populations, which are nowhere very dense, showed no decline comparable to that of Ophiothrix.

Predation by the starfish Luidia ciliaris and L. sarsi is thought to be a likely cause of the disappearance of Ophiothrix. Luidia spp. are active predators on ophiuroids and other echinoderms, and numbers of L. ciliaris were observed in the vicinity of the Ophiothrix beds at the time of the decline. Both species of Luidia have a ’western’ distribution in the Channel, and showed an increase in density off Plymouth after the late 1960s, which is probably related to a changeover from a Sagitta setosa to a 5. elegans plankton community from 1968 on. The distribution of these Luidia is confined to stratified waters in the western Channel, surviving stocks of Ophiothrix being limited to mixed waters in the southern and eastern Channel where Luidia does not occur.

Seven species of the amphipod genus Ericthonius are described and figured from the North-east Atlantic and associated seas and a key to their identification is provided. West Atlantic material is also considered where relevant to the taxonomy of East Atlantic species. Two species are re-established after a long period of submersion in synonymy, and one species new to science is described. The previous confusion in the literature of some of the species is discussed, and a synonymy of species described in key works is provided.

In experiments to investigate the effect of low salinity on growth in Mytilus edulis, unexpected depression of growth occurred, even in sinusoidal regimes falling to only 90% of the full salinity, when tap water was the diluting medium used. The effect of various additives to the domestic water supply on the growth of Mytilus was investigated. Chlorine and fluoride had no effect although fluoride (as sodium fluoride) inhibited faeces production in a 7-day experiment. Determinations of the level of copper in the laboratory's tap water showed these to be high enough to cause depression of growth even at low dilution levels. When distilled water or lake water was used to dilute the sea water, shell growth was not affected until a sinusoidal fluctuation reaching a minimum of 50% sea water was used. Such effect did not become significant until the mussels were kept in pure fresh water for an extended period in each cycle of sinusoidal salinity variations.

Annual cycles of development were studied in male and female Iceland scallops (Chlamys islandica). Volume fractions of each germ cell type and other gonadal tissue were determined by histological and stereological techniques. Spawning occurs during a short period in late June and early July.

The effects of copper and zinc on the daily shell growth of Mytilus edulis have been measured with a laser diffraction measuring technique accurate to 3 µm. The results show that within three days 10 ppb added copper has a significant inhibitory effect on shell growth. Longer term experiments have been undertaken which show that the effects of 10 ppb added copper become more severe as exposure time increases. Recovery of near normal shell growth does occur on transfer to clean sea water even after a 14 day exposure to this concentration. The effects of zinc on shell growth are less severe. Transferring animals from their natural environment to the laboratory causes a measurable disturbance of shell growth for up to a week.

The tenacity of the barnacle cyprids of Balanus balanoides (L.) during temporary adhesion to a variety of modified Perspex surfaces was tested using a sensitive microbalance. The Perspex panels were painted on the undersides with five colours of cellulose paint. Control measurements of the magnitude of temporary adhesion to clean slate panels were of the order of 2 × 10 N m. Untreated smooth Perspex panels and panels coated with an adsorbed layer of bovine serum albumen gave low figures of tenacity of the order of 0·8 × 10 N m. Roughening the panels with carborundum or treating with an adsorbed layer of barnacle extract protein resulted in higher tenacity measurements (1·0–1·8 × 10 N M), whereas the highest measurements were obtained when roughened Perspex panels were coated by an adsorbed layer of barnacle extract protein (1·6–2·2 × 10 N M). When the surfaces were made more attractive to barnacle cyprids by roughening or coating in barnacle protein the forces measured on dark coloured panels were higher than on lighter coloured panels. The results of the temporary adhesion measurements were closely paralleled by the numbers of cyprids found exploring the various surfaces during preference settlement experiments.

The herring is a physostome with no gas secretion mechanism in the swimbladder. The swimbladder volume was measured in fish from about 3–33 cm in length. It was rarely large enough to give the fish neutral buoyancy at the sea surface. Swimbladder volumes were also measured after periods of up to 1 week at pressures from 1·9 to 5·5 ATA (0·9–4·5atm above atmospheric pressure) in a laboratory pressure vessel and in a sub-surface cage in the sea. The swimbladder gas was lost within a few hours in the larval herring and in a few days in smaller juvenile fish; no change was found in older fish under experimental conditions. The findings were in accord with measurements of the guanine content of the swimbladder wall which was low in those fish which lost gas quickly. This supports the view that gas diffusion is limited by guanine crystals. While it seems likely that larger fish can exist for several weeks without the need to replenish the swimbladder gas some large spawning herring were caught at sea with empty swimbladders, suggesting a long stay near the sea bed. Analysis of swimbladder gas showed that oxygen tended to diffuse out more quickly than nitrogen. Behaviour experiments showed that fish with artificially emptied swimbladders could refill them by swallowing air at the surface, in some cases very quickly and efficiently. Fish with empty swimbladders and no access to the surface suffered a high mortality. The ecological implications of these results and their relevance to the interpretation of sonar ‘target strength’ measurements are discussed.

The gonadial, pyloric caecal and somatic cycles over three consecutive years in a subtidal population of the starfish Marthasterias glacialis from Plymouth Sound are described. The study area lies towards the eastern limit of the up-Channel range of this species, and this is reflected in only partial reciprocity between gonadial and pyloric indices, and also by the apparent utilisation of somatic material during the build-up of gametes. The sequence of events at the cytological level during gonadial build-up is described.

Gonadial, pyloric caecal and somatic indices and oocyte size-frequencies are compared over a 3-year period for the starfish Asterias rubens from an intertidal nutritionally rich site and a subtidal impoverished site from the English Channel off south-west Britain. The intertidal population showed significantly higher values for all three indices over most of the study period compared with the subtidal population, and its spawning occurred later. The somatic index of the subtidal population showed a steeper rise than the intertidal population over that part of the cycle in which the gonads were undergoing enlargement, which gives further support to the suggestion that starfishes deprived of sufficient food may give priority to maintenance of the body-wall over enlargement of either the food-storage tissues of the pyloric caeca or the gonads.

The mortalities and subsequent recolonization of a rocky shore in S.W. Ireland following a bloom of the toxic dinoflagellate, Gyrodinium aureolum in 1979 are described. Selective mortalities of key animal species notably grazing gastropods were followed by a marked increase in fucoid algae. Enteromorpha spp. blooms were a feature of vertical surfaces only. In general planktonic recruiting gastropods exhibited the most rapid recovery. Forty-two months after the red tide, fucoid algae still dominate both vertical and horizontal surfaces at the study area.

Introduction

Dinoflagellate blooms ('red-tides'), chiefly of Gyrodinium aureolum Hulburt have been recorded several times in Southern Ireland since 1976 (Ottway et al. 1979; Cross & Southgate, 1980; Jenkinson & Connors, 1980; Leahy, 1980; Roden, Ryan & Lennon, 1980; Wilson, 1982) and have resulted in mortalities of farmed rainbow trout in sea-cages in Dunmanus Bay (Parker, 1981). Other species of pelagic and demersal fish on the south coast were also affected by a toxic red-tide in 1976 (Ottway et al. 1979). Owing to the unpredictability of occurrence of dinoflagellate blooms, few studies on the effects of red tides on littoral fauna, and on the subsequent recolonization following the events have been carried out. Previous studies in Dunmanus Bay, Ireland (Leahy, 1980) suffered from a lack of the shores prior to the of information about the structure and dynamics occurrence of a red-tide.

Regular monitoring of the rocky shore biota at Dunmanus Bay (Myers, Southgate & Wilson, 1980) has been carried out since May 1978 and is continuing. The red tide of August 1979 caused dramatic mortalities of a wide range of taxa at Pointabulloge in Dunmanus Bay (Cross & Southgate, 1980).