The development of the persistent suture tag has permitted the study of long-term migrations of large decapods like the European edible crab (Cancer pagurus L.). A tagging study of the growth and migrations of C. pagurus was part of a research project undertaken to provide advice on the effective management of the English Channel crab fishery. During the years 1968–74 a total of 15296 suture-tagged crabs was released; the majority in the main fishery off south Devon and Cornwall, but releases were also made in the eastern half of the Channel. The early releases were mainly inshore, within 22 km (12 nautical miles), but as the fishery expanded offshore releases were made in mid-Channel.

Most of the recaptures occurred within two years of release, with the highest recapture rates being in the most intensively fished areas during the main fishing season. From the total of 2714 crabs recaptured, 2255 had reliable recapture information. In the inshore release areas 90 % of the males and 76 % of the females were recaptured within 18 km (10 nautical miles) of their release position. Offshore the corresponding proportions were considerably lower at 76 % and 59%, with 11 % of the males and 21 % of the females having moved > 90 km (49 nautical miles).

When males did move > 18 km they were mainly the larger males and their mean displacements were 14–31 km in several directions. The offshore releases of males in the middle and eastern Channel showed more extensive movements, which appeared to be directed, most of them being in a westerly direction, with mean displacements of 41–114 km. With only one exception, the female inshore releases had a mean direction of movement of between south and west, with mean displacements of 12–84 km. Overall, those females making the more extensive movements were larger than those caught in the vicinity of the release positions. The last inshore release at Portland Bill gave the first indication of extensive westerly movements from the eastern part of the English Channel.

Movements of females released on the offshore Devon and Cornwall grounds were mainly in a westwards direction, although several inshore movements and longer distance movements of up to 302 km towards the French coast were recorded. The recaptured females from the middle and eastern Channel releases showed greater mean displacements (110–158 km), all in a westerly direction. Only 10% of the mid-Channel recaptures were made within 18 km, with 73% being caught > 90 km from their release position. The highest mean velocity was 23 km/week, with an individual maximum of 183 km/week.

Most of the recaptures of male C. pagurus released inshore were made near the release position, and those movements which were observed would appear to be the result of nomadism. Offshore males seemed to be more mobile, but a nomadic existence for larger male C. pagurus seems more likely than migration. Female C. pagurus in the English Channel are more mobile than males. Large, mature, female crabs leave the eastern Channel and congregate in the autumn off south Devon. During the winter and spring there may be some nomadic movements. These migratory movements are reflected in the size composition and sex ratio. The migrations seem to be related to the breeding behaviour, ensuring a suitable sea-bed substrate for berried crabs and/or allowing distribution of the larval phase on the easterly residual currents in the English Channel.

This paper reports a preliminary investigation into physiological and pharmacological aspects of the motor activity of the digestive tract of Octopus vulgaris, with reference tothe relevant anatomy. The results suggest that the octopus gut shows many similarities to somevertebrate guts in terms of functional morphology and motor control. Pharmacological experiments suggest that acetylcholine, noradrenaline and 5HT may act as neurotransmitters and probablyregulate the digestive activity by antagonistic actions, reminiscent of the classical divisions of the vertebrate autonomic nervous system. Histochemical evidence is presented that some ofthese substances are located in the nerves and ganglia of the digestive tract.

The movements, abundance, age composition and growth of bass, Dicentrarchus labrax (L.), in the Severn Estuary and inner Bristol Channel have been described from regular samples offish taken from power-station intake screens between 1972 and 1977. Bass began to move into the estuary during late August or September and reached peak abundance between September and early November. The tendency for fish to move seawards in the late autumn and winter may be related to declining water temperatures in the estuary. Likewise, differences in abundance between years appear to be related to annual differences in temperature. Although the populations were dominated by the 0 + age class, successively decreasing numbers of the next four age classes and occasional 5 + fish were also present. Respective mean standard lengths of bass in the estuary at the end of their first to fifth years of life were approximately 65 mm (≡ 4·5 g), 130 mm (≡ 37·9 g), 190 mm (≡ 121·1 g), 250 mm (≡ 280·4 g) and 290 mm (≡ 441.5 g). Growth occurred predominantly between May and September, with the mean standard length of 1 + fish increasing from approximately 65 mm (≡ 4·5 g) to 130 mm (≡ 37·9 g).

Unfertilized eggs in the oviducts of female lumpsuckers are exposed to low oxygen tension (ca. 40% air saturation). After spawning and fertilization water agitation aids percolation of water through Cyclopterus egg masses, but early in development oxygen tensions within non-ventilated egg masses fall slowly because of the eggs’ low metabolic rate (consistent with their slow development – 40 days to hatching at 5 °C). There is a considerable increase in oxygen uptake at hatching; in this respect the lumpsucker resembles the herring, Clupea harengus.

Early stage eggs are tolerant of hypoxic conditions and can even survive brief exposure to anoxic sea water. Later eggs and larvae are much more susceptible to oxygen lack. However, fanning behaviour by the brooding male parent (usually assumed to be designed to promote oxygen uptake by egg masses) is almost continuous at the beginning of development but becomes less frequent later. It is suggested that the initial intensive fanning helps to drive off ammonia which is released as the eggs stick together.

From works on the anatomy and ecology of dorid nudibranchs it has been assumed that they were capable of cutaneous respiration through their dorsal mantle. The present work has shown how the oxygen uptake is depressed when the dorids Onchidoris bilamellata and Archidoris pseudoargus are exposed to air and the gills collapsed into the body surface. The effect of ligaturing the gills of A. pseudoargus into the branchial pocket has enabled direct measurements to be made of the mantle respiration.

The effect of temperature on respiration was examined.

The effect of changes in particle size and sediment depth on byssal attachment was assessed in laboratory experiments. Mytilus edulis did not attach byssus pads to mud or silt less than 0·85 mm in diameter, but did attach pads to gravel. On gravel more pads were attached to the substrate (mean = 19·44 threads/mussel/week) than to other mussels in the group (mean = 7·34 threads/mussel/week). Because no byssal attachment to the finer substrates occurred and preference for other mussels in the groups rather than the plastic of the holding tank was shown, clumps, characteristic of mussel beds in the field, were formed. The clumps became increasingly well defined as the depth of the substrate increased. Few clumps were formed on the coarsest substrate as a result of preferential byssal attachment to gravel particles.

Spinal cords in deep sea fishes of 37 families have been examined for the presence and relative size of Mauthner axons. No correlation has been found between fish size, and the relative diameter of the Mauthner axon in different species. However, counts of primary motoneuron number and myotomal muscle fibre number in each segment suggest that Mauthner axon diameter is related to the numbers of these in each segment. The behavioural role of the Mauthner system is discussed, and it is concluded that in certain elongate-bodied fishes such as halosaurs and macrourids, a C-type startle response is unlikely.

The morphology and microanatomy of two different phases in the life history of a single new marine choanoflagellate (Proterospongia choanojuncta sp.nov.) have been documented and described with the aid of light microscopy and from electron microscopy of whole mounts and sections of material in clonal culture. Completion of the life-cycle has been repeatedly achieved in cultures established from single cells, regardless of which phase is used as a starting point. One phase is colonial and motile (the Proterospongia phase) and the other unicellular and sedentary (the Choanoeca phase). Taxonomic, nomenclatural and developmental problems are summarized and discussed.

A humoral immune response was elicited in adult dogfish by intramuscular injection of keyhole limpet haemocyanin (KLH). The antibody raised to this antigen was measured by an agglutination technique. The antibody-containing fraction of the serum was isolated in a two-step procedure utilizing gel nitration on Sepharose 6B and slab gel electrophoresis. A rabbit antiserum was then raised to the purified immunoglobulin. Further gel filtration studies revealed that the anti-KLH agglutinating activity was restricted to a highmolecular-weight serum fraction (approximately 800000) in fish immunized for up to 18 months. No anti-KLH precipitating activity was detected in fish at any stage of immunization; however immunodiffusion studies with the rabbit antiserum raised against dogfish antibody confirmed the existence of an 800000 molecular weight form and also a lighter species weighing 160000 daltons in both normal and immunized fish. The antigenic specificity of this latter molecule was not demonstrated. Immunoelectrophoretic analysis of the antibody revealed a neutral/slight anodic mobility, and after reduction and alkylation the presence of two polypeptide chains weighing 18200 and 75 860 daltons was demonstrated by thin-layer gel chromatography. These physicochemical characteristics make dogfish antibody analogous to mammalian immunoglobulin M (IgM).

A new ascothoracid, Isidascus bassindalei gen.nov., sp.nov., has been discovered in the north-east Atlantic Ocean at a depth of over 2000 m. It forms permanent galls on the branches of Acanella arbuscula, a gorgonian of the Family Isidae (Octocorallia, Coelenterata). The new genus is related to Gorgonolaureus, species of which form galls on paramuriceid gorgonians. The gall of the present form unlike that of Gorgonolaureus incorporates a cup of host calcite. Twenty-three adult female specimens and one male were examined in this study. The adult parasite is characterized by elevated humps in a median dorsal position on each of thoracomeres 2,3 and 4. A further feature is a tapering filamentary appendage arising near the base of first thoracopod. The parasite apparently feeds on its host's coenosarc. The likely function of the first and second antennae and each of the three pairs of stylet-form mouth parts is suggested. A case is made for interpretting the species as a protandrous sequential hermaphrodite. Whilst still immature, protanders apparently seek out and settle alongside an adult female. Later, following growth and sexual maturation they again become mobile and after copulation with the nearby female depart to prepare for sex change on a separate branch of the host.

Mytilus edulis attached more byssus threads to slate than to glass and more to glass than to p.t.f.e. in a given time period. This coincided with the order of polarity of the surfaces. On p.t.f.e., a non-polar plastic, the animals were most mobile, and were found to move off the surface in 3–5 days. Whilst on the polar surfaces, the animals clumped on glass, and remained relatively immobile on slate.

When a choice of surface for byssal attachment was provided, the largest number of pads was always attached to the more polar surface. The preference was as follows: slate/glass 2·80 : 1·00; slate/ 5·38 : 1·00; glass/wax 5·97 : 1·00. Although the preference for slate and glass over wax was numerically similar, there is a clear preference for slate over glass.

Rapid fixing of skeletal muscle by a ‘freeze-clamp’ technique results in up to a 3-fold lower lactate, a slightly higher pyruvate concentration and a 2- to 4-fold decrease in lactate/pyruvate ratio, to the lowest value yet recorded for fish muscle, when compared with the more usual method of direct immersion in liquid nitrogen. This is attributed to the faster cooling rate of freeze-clamped muscle minimizing ‘sampling anoxia’. Immobilizing fish either by anaesthetic or stunning produces no significant change in metabolite levels. It is concluded that it is relatively easy to handle quiescent flatfish, but light anaesthesia ensures no muscular activity.

Of a wide range of algae tested, juvenile Convoluta roscoffensis ingested only Platymonas convolutae, the natural symbiont; related species of the genera Platymonas, Prasinocladus and Tetraselmis; and Chlamydomonas coccoides. Platymonas convolutae was not ingested to a greater extent than Prasinocladus marinus, Tetraselmis tetrathele and Tetraselmis verrucosa, or taken up in preference to T. verrucosa when animals were exposed to a choice between the two species. Convoluta ingested fewer cells of C. coccoides than P. convolutae and related species. Uptake of P. convolutae was not affected by pretreatment of the cells with lectins or proteases, incubation in media of pH 5·0–9·0 or inhibition of algal photosynthesis, but was substantially reduced if the algae were killed.

Cells of P. convolutae, Pr. marinus, T. tetrathele and T. verrucosa persisted and divided in juvenile Convoluta. The algal population in the worms started to increase 2–3 d after ingestion and within 15–20 d the animals were uniformly green. These algae formed a viable symbiosis with Convoluta and promoted the growth of the animals. In contrast, C. coccoides cells did not persist in Convoluta for more than 12–24 h a nd were probably disrupted.

P. convolutae cells lost their thecae within a few days of ingestion and before migration from the central to sub-epidermal region of the animal. Animal vacuoles surrounded recently ingested thecate algae. Structural studies of the adult symbiosis suggest that the algae were also intracellular and enclosed in vacuoles.

It is proposed that Convoluta discriminates against algae unrelated to P. convolutae on initial contact and in the central region of the host. The nature of the recognition mechanism(s) has not been established.

Body scales in dinoflagellate species belonging to Heterocapsa developed in vesicles derived from the Golgi apparatus, but did not appear within the stacked Golgi cisternae. The membranes of the scale vesicles functioned as molds for the developing scales. Mature scales within expanded vesicles moved to the flagellar area, the site of release. Body scales were seen within the cytoplasm of Heterocapsa spp. fixed at various times in the light: dark cycle, suggesting that scales are formed and probably released continuously.

Specimens of Littorina littorea from unpolluted (Menai Bridge) and metal polluted (Restronguet Creek) sites have been analysed for ten metals in eight different tissues. The concentrations of metals in whole animals and in individual tissues have been subjected to linear correlation analysis to establish metal/metal and tissue/tissue interactions. The results indicate that copper and magnesium are accumulated independently by specific connective tissue cells. Group A metals are largely accumulated by the digestive gland whereas group B metals are concentrated by the kidney. At low levels of metals there may be competition for particular ligands but at higher levels of pollution new ligands may be induced in particular cells. The implications of these interactions are discussed in terms of cell physiology and related to the significance of the use of biological organisms as indicators of metal pollution.

The attachment capabilities of a brown seaweed, Sargassum muticum (Yendo) Fensholt were investigated in the laboratory on both smooth and rough substrata and in surging water motion reaching flow velocities of 57 cm s and 90 cm s.

Newly released zygotes have no means of adhesion until they develop rhizoids, which can adhere on contact with the substratum. Attachment tenacity, as measured by the germling's ability to withstand dislodgement at a given velocity of water flow, is slight at first, but increases with time. This is not simply a function of time spent in residence on the substratum, for germlings cultured suspension stick very quickly and tenaciously when allowed to settle. Tenacity of adhesion seems to be a reflexion of the amount of mucopolysaccharide adhesive present. This increases gradually during the first few days of the germling's life, regardless of whether it is attached or not.

Once secure attachment is achieved it is not weakened even by the death of the germling. A film of bacteria and micro algae on the surface of the substratum is not a requirement for germling adhesion, but its presence enhances the tenacity of adhesion.

Smooth substrata are the least favourable for germling survival in flowing water. On rough substrata the ‘peaks’ of the microtopography and surfaces facing into the current are much less favourable than the troughs between the ‘peaks’, or surfaces in the lee of ‘peaks’. Germling survival increases with increasing substratum roughness up to an optimum rugosity at which the mean depth of the depressions on the surface is 420 μm, and the vast majority are deeper than the height of the germlings.

Uptake and incorporation of [3H]glycine from 1 μM solutions was observed in the tissues of larval oysters, Crassostrea gigas, Ostrea edulis, and mussels, Mytilus edulis. In all cases, radiolabel first appears in the larva's velum. Following increasing exposure time, label begins to appear in other organs. In newly settled larvae of the oyster, C. gigas, and the scallop, Pecten maximus, uptake occurs via the developing gill buds. All experiments provide evidence of direct epidermal uptake of soluble nutrients without any participation of the digestive tract. Scanning electron micrographs show that there is no bacterial population visible on the surface of the velum that might act as an intermediate step in nutrient transport. These studies on veligers, pediveligers and settled larvae link the phenomenon of larval uptake with the extensive literature on the direct uptake of soluble nutrients by adult bivalves.

Uric acid is an excellent nitrogen source for the growth of cultures of Platymonas convolutae, the symbiotic alga from Convoluta roscoffensis, and related Platymonas and Tetraselmis species. Nitrate-grown cells of P. convolutae and T. tetrathele have two uptake systems for uric acid, which conform to Michaelis–Menten kinetics; a high-affinity system operating in the concentration range 0·2–4·5 μM a nd a low-affinity system operating at higher concentrations of uric acid. Uric acid uptake by P. convolutae is abolished by uncouplers of phosphorylation. In darkness, intact cells of P. convolutae metabolize [2-14C]uric acid to [14C]carbon dioxide. These results are consistent with the proposal that the algal symbionts of C. roscoffensis utilize uric acid, received from the host, as a nitrogen source.

Aposymbiotic juvenile and symbiotic adult C. roscoffensis under standard culture conditions contain uric acid. The solid uric acid content of juveniles declines on establishment of symbiosis with P. convolutae and the endogenous uric acid is utilized in the adult symbiosis under conditions of nitrogen demand. However, adult C. roscoffensis do not utilize exogenous uric acid. The growth of adult but not juvenile C. roscoffensis is dependent on nitrogen enrichment of the medium, and it is proposed that uric acid utilization is of significance to the growth of the developing symbiosis in a nitrogen-poor environment.

Serial-section electron micrographs have been obtained of the phagocytosis of Prochloron cells by amoebocytes of the ascidian Lissoclinum voeltzkowi (Michaelsen). This may answer the hitherto puzzling question of how the host tunicate benefits from photosynthetic symbionts situated in an excurrent water flow.

Atrispinum labracis (Van Beneden & Hesse) n.comb. syn. Microcotyle labracis Van Beneden & Hesse, 1863, parasitizes the bass Dicentrarchus labrax but almost only in the open sea; the very low prevalence of parasites on juvenile estuarine hosts was not due to intolerance of lower salinities in this habitat. The intensity of infection on open-sea bass was rarely more than 2 per fish but the strict localization of the habitat to the outer hemibranch of the ventral end of the first gill arch is thought to enhance the mating opportunities. The parasite attaches itself asymmetrically to the gill by a permanent morphological inclination of the body with respect to the haptor which is itself symmetrically aligned on a single primary lamella.

Substantial differences between the copulatory apparatus of A. labracis and that of Microcotyle donavini Van Beneden & Hesse, 1863, the type of Microcotyle, have made necessary the transfer of the parasite from Dicentrarchus labrax to Atrispinum Maillard & Noisy, 1979 and a consequent amendment to the diagnosis of the subfamily Atriasterinae Maillard & Noisy, 1979.