Ten species of deep-water Pycnogonida are recorded, mainly from the north-eastern Atlantic Basin. Of particular interest are Ascorhynchus abyssi Sars (new to the British Isles), Colossendeis arcuata A. Milne Edwards (northernmost record in European waters), C. bicinc0ta Schimkewitsch (third Atlantic record, depth range increased), C. macerrima Wilson (new records from the English Channel), Nymphon laterospinum Stock (new to the Indian Ocean), Pallenopsis (Bathypallenopsis) oscitans (Hoek) (new to the English Channel and bathymetrical range extension), P. (B.) tritonis Hoek (extension of depth range), P. (B.) tydemani caraibica Stock (second European record, now found at the entrance of the English Channel), and Anoplodactylus arnaudae Stock (range extended to the Rockall Trench).

The reproductive cycles of four widely separated Modiolus modiolus populations from W. Sweden, W. and N. Norway, and Northern Ireland were examined in relation to their contrasting temperature regimes. Reproductive condition was analysed on the basis of the degree of development and numerical density of the gametes, and on size-frequency distributions of oocytes.

All the Scandinavian populations had well defined spawnings, those of W. Sweden and W. Norway occurring in June and followed by a period of redevelopment and further gamete release. The N. Norway population spawned in July and subsequent redevelopment was not accompanied by further spawnings. Both Norwegian populations overwintered in a relatively ripe condition, but that from W. Sweden spent the winter in a low state of reproductive development. The N. Ireland population contrasted with the others in being continuously ripe and having no overt spawning, but rather a slow, constant release of gametes throughout the year.

These differences are assessed in terms of the effects of the local temperature regimes on the interacting processes of gametogenesis and spawning. It is concluded that seasonal variability in temperature plays a major role in determining the extent and duration of gametogenesis, whilst spawning is more dependent upon the attainment of a limited range of minimum temperatures. The northern limit of M. modiolus is therefore more likely to be determined by failure of conditions suitable for spawning and larval development than by a failure of gametogenesis.

Samples collected regularly from the intake screens of power stations between July 1972 and June 1977 demonstrate that the Gadidae is the most abundant and diverse teleost family in the inner Bristol Channel and Severn Estuary. The first records for the Severn Estuary of two cold water species, northern rockling and Norway pout, which were present in appreciable numbers, may be related to the effects of the changes that commenced in south-western English waters during the 1960s. Maximum numbers of the five most abundant gadoids were attained in different years, with the greatest catches being recorded for whiting and poor cod in 1975/6, bib and pollack in 1974/5 and northern rockling in 1976/7. Peak abundance in the middle estuary was reached by whiting, bib, poor cod and pollack in the autumn and by northern rockling in the winter or early spring. The 0 + age class of these species, which was always by far the most predominant category, showed increases in mean length during their relatively short stay in the estuary. Movement out of the shallows of the inner Severn Estuary by whiting and also apparently by some other gadoids occurred when salinities fell below 10‰. The size of poor cod and pollack in the autumn was not as great in 1974 as in 1975 and 1976, presumably reflecting the effect on growth of lower summer temperatures in the first of these years. Poor cod was represented by five age classes and attained at the end of the first to fifth years of life standard lengths of approximately 80 mm (≡4.8 g), 110 mm (≡11.7g), 140 mm (≡23.0 g), 170 mm (≡39.6 g) and 210 mm (≡71.6 g) respectively.

The annual cycles of the Abra tennis populations in the Plym Estuary and the Fleet (Dorset) were studied from March 1980 to June 1982. In the Plym Estuary the highest numbers occurred in autumn following juvenile recruitment and the lowest numbers were recorded in mid-summer. In the Fleet such an annual cycle in numbers was not apparent since juvenile recruitment in 1980 was very high but in 1981 it was very low. The recruitment failure in 1981 may have resulted, at least in part, from the heavy summer infection of A. tenuis by digenean parasites that destroy the gonads of the host, thereby reducing the population fecundity.

A. tenuis spawns in July and August: the mature egg has a diameter of 140 μm and is enclosed in a sticky gelatinous envelope. Females produce 450–1800 eggs which, when fertilized, are laid in a mass within the sediment and, following a direct development, the juveniles hatch as miniature adults after 2–3 weeks. This non-pelagic, lecithotrophic development is interpreted as being a means of ensuring the maintenance of populations within restricted estuarine habitats. Data suggest A. tenuis lives for 1 or 2 years and that the species is monotelic.

In Carcinus maenas haemolymph, zinc is almost entirely bound to the respiratory pigment, which is the copper-protein haemocyanin (Hc). Zinc ions are loosely bound, as indicated by the low value of the association constant (k = 1.7 × 105 M-1 at pH = 8.0). The number of binding sites N is equal to 4 per minimal functional subunit (75000 Dalton). No co-operativity has been found between the different metal sites. Data reported in this paper support the hypothesis that haemocyanin can act as metal carrier in the haemolymph of C. maenas.

Incubated embryos are here recorded from the Sabellinae Amphiglena mediterranea, Potamilla neglecta and Perkinsiana antarctica, and the Fabriciinae Fabricia sabella, Fabriciola chilensis, Oriopsis alata and Oriopsis ehlersi, but incubation has not been observed in most species of Sabellinae, nor in any Myxicolinae. Natural fission (as opposed to regeneration following damage or autotomy) is also rare in Sabellidae, but a Scilly Isles tube worm identified as Sabella variabilis Langerhans, multiplies by fission from the posterior end, like the Filograninae amongst serpulids.

Light and electron microscopical reinvestigation of Polyoeca dichotoma Kent revealed that Acanthoecopsis spiculifera Norris, the type species of the genus, is a synonym for Polyoeca dichotoma. Since this step invalidates the use of the name Acanthoecopsis, a new genus Acanthocorbis was established for the three species formerly included in Acanthoecopsis.

The three dimensional arrangement of costal strips forming the loricae of Polyoeca dichotoma and Acanthoeca spectabilis Ellis were examined by scanning electron microscopy. The arrangement of costal strips were similar in both species. The longitudinal costal strips and those forming the spines were arranged outside the supplementary costae and those of the transverse bonds.

The vertical distribution of Decapoda (Crustacea) at deep-water stations in the Rockall Trough and the Porcupine Seabight is discussed and compared to the near-bottom distribution of Decapoda on the continental slope of the Seabight. The vertical distribution of some species is unaffected by the shallowing of the sea floor in the slope area. Other species are found in much higher concentrations near-bottom over the slope than at similar depths at the adjacent deep-water stations and at least one species extends its lower vertical range. It is suggested that the increased food availability near-bottom may be the principal factor influencing aggregation.

Available data on the size distribution of particles captured by Mytilus indicates that a somewhat leaky, but non-sticky, filter with a minimum mesh size of a little over 1.0 μm is present. The side branches of the latero-frontal cirri have such a mesh and are positioned so as to filter water passing between the gill filaments. Information on the pressure distribution within the water circulation, and calculations of the pressure required to pass watet ihrough the latero-frontal filter at observed speeds, suggest that a little more than half the pressure generated by the lateral ciliary pump is required to overcome resistance in the latero-frontal filter and the remainder is required to circulate water in through the inhalant opening and out in an exhalant jet. The lateral cilia appear theoretically capable of generating sufficient power to produce the required pressures. Calculations indicate that although hydro-mechanical shear forces are unlikely to provide a significant contribution to particle capture, they may provide a means of keeping particles within the frontal current without a need for mucus, after filtration and transfer of particles to the frontal surface by the latero-frontal cirri.

The Plymouth Marine Fauna (Marine Biological Association, 1957) list of monogenean parasites of fishes has been increased from 39 to 58 species and in addition 2 species have been recorded from a cephalopod host. The increase in listed species represents an increased ‘parasitological effort’ rather than an influx of new species into Plymouth waters.

A numerical model is used to demonstrate wave trapping of the diurnal tides on Porcupine Bank and Rockall Bank. These waves have wave lengths of about 300 km and travel along the sloping topography with shallow water on their right. On the slopes of Porcupine Bank the shorter period K1 wave has a longer wavelength than the O1 wave and so here the trapped diurnal spring-neap signal propagates in a direction which is opposite to the phase velocity.

Nephtys pente sp.nov. is described. The species is known to occur in shallow waters from the western Baltic to Greenland. It may occur with Nephtys ciliata, which it closely resembles. An amended definition for N. ciliata is proposed. A key is provided for the northern European species of Nephtys.

The eyes of characins (Characidae), pike, pickerel (Esocidae) and wrasses (Labridae) have a red pigment epithelium. There is no melanin, the epithelial cells containing red particles (erythrosomes). These are tiny cylinders in the cell processes, and spherules in the cell bases. In characins and pike, the red cylinders participate in retinomotor activity. Cylinders are birefringent and act as waveguides; they transmit long wavelengths (> 550 nm). The red pigment has been extracted and purified. It appears to be the same in the three families. Ultraviolet, visible and infra-red spectra are presented.

Brumptiana lineata n.gen. et sp., from oro-nasal region of Raja, has a subcylindrical body, 2 pairs of eyes, 13 or 14 annuli per mid-body somite, 12 pairs of small pulsatile vesicles, 5 postcaecal fenestrae, 5 or 6 pairs of testes, a large muscular atrium with accessory glands, a thick-walled vagina and no receptaculum, conducting tissue or spermatheca.

Using vital staining of neuromasts, followed by recovery, cupular growth rates of 1.4–4.1 μm/h were found in herring (Clupea harengus L.) larvae and 4.0 μm/h in juveniles. It seems likely that the cupulae are continually being shed and replaced.

Cytokinesis is described for the first time in a pelliculate dinoflagellate that retains its thecal plates during cell division. In Heterocapsa niei cytokinesis proceeded in a manner that differed from that described for other dinoflagellates. The thecal plates separated along the fission line before the development of a cleavage furrow. A distinct cleavage furrow developed as cytokinesis progressed. The outer membrane and the outer plate membrane expanded during division to enclose the enlarging cell undergoing cytokinesis; however, as the cleavage furrow deepened, these membranes were not continuous with the cytoplasm. The pellicle was occasionally intermittent in the region of the cleavage furrow, possibly facilitating movement of material from the cytoplasm to the developing outer membranes. Thecal plate formation occurred within the thecal vesicle from unrecognizable precursors.

The maximum habitation depths of chambered cephalopods are dictated by the mechanical properties of the shell. All chambered cephalopods have a depth at which ambient pressure is sufficient to implode the gas-filled shell portions. Experiments on Sepia elegans D'Orbigny, S. officinalis Linne and S. orbignyana Férussac from the Mediterranean Sea show these three species to have differing depth limits and modes of shell implosion. Large S. officinalis implode between 150 and 200 m, whereas newly hatched and advanced embryonic specimens implode between 50 and 100 m. The larger S. officinalis are occasionally caught at depths greater than the implosion depth of the juvenile shell parts. They apparently avoid implosion of the early shell portions by refilling these first-formed chambers with cameral liquid later in life. Implosion in S. officinalis generally resulted in the crushing of all or most of the septa in a band extending from the embryonic region to the anterior part of the shell. Implosion was generally accompanied by fatal rupture of underlying tissue into the implosion zones. Implosion of S. orbignyana occurred between 550 and 600 m and was very different in form from that in S. officinalis, occurring mostly within the smooth zone of the last-formed several chambers, and rarely extending back into the siphuncular region (striae zone). Increasing depth caused episodic implosion of sequentially older chambers in the smooth zone. The shallower implosions were accompanied by little soft-tissue damage. Massive internal injury only occurred in the deepest implosions (700 m or greater). Implosion in S. elegans occurred betw en 400 and 600 m. Too few specimens were available to allow generalizations about morphology of implosion in this species.