Patella vulgata were excluded from barnacle dominated areas at Port St Mary, Isle of Man by wire fences attached to the rock in September 1977, December 1977, April 1978 and July 1978. The sequences of algal colonization of these exclusion areas differed markedly with season: in autumn diatoms were followed directly by Fucus, in winter and spring diatoms were followed by green algae and then Fucus, and in late summer Fucus sporelings arose directly on the barnacles. There was no evidence that the initial stages were necessary for the subsequent recruitment of Fucus.

The climbing behaviour of the gastropod Hydrobia ulvae (Pennant) and its relationship with flotation/dispersal were investigated by field observations and experiments in Norfolk, U.K. and by laboratory experiments. Field experiments of the type used by previous authors were discontinued when it was observed that counts at low tide of snails which had climbed objects the previous high tide did not reflect adequately climbing activity during that period of tidal cover. Both field and laboratory studies yielded five general results: (i) snails climbed only when covered by tidal water; (ii) climbing activity was not related to population density; (iii) climbing activity, under conditions of constant population density, varied markedly during the cycle of spring tidal cover, reaching a peak after the first few tides and declining rapidly thereafter; (iv) maximum numbers of snails were present on submerged structures relatively early in any given period of cover and declined (snails crawled downwards off the structure) as the period of cover continued; and (v) rarely were large proportions of climbed Hydrobia floated off their support by the incoming tide; this was associated only with conditions of extreme calm.

The effects of nutrient additions and zooplankton excretion products upon carbon fixation rates in the phytoplankton present at Station L 4 in the English Channel during the summer and autumn of 1979 have been studied. Nitrate, ammonium, urea, phosphate, glucose-6-phosphate and the excretion products when added individually all caused photosynthesis to be stimulated, and the result of the simultaneous addition of nitrate and phosphate indicated that their effects were additive. Germanic acid, which inhibits photosynthesis mainly in diatoms, removed the stimulatory effect of the nitrogen supplements, indicating that they were utilized mostly by the diatoms; the higher fixation rates caused by the phosphate enrichments were, however, decreased by the same proportion as the unenriched controls when germanic acid was present, suggesting that the whole of the phytoplankton population was phosphorus-limited. This was supported by the finding that glucose-6-phosphate stimulated carbon fixation in all of the phytoplankton.

The excretion products, even at concentrations likely to be produced in the sea, stimulated carbon fixation, and it has been calculated that zooplankton-regenerated nitrogen and phosphorus compounds could supply the amounts needed to maintain primary production during the summer period.

Nutrient additions and zooplankton excretion products had little effect upon carbon fixation in the autumn samples, presumably because the higher nutrient levels then present in the water exceeded the requirements of the phytoplankton.

It has been concluded that the predominance of the sub-10 μ microflagellates in the summertime is probably due to their ability to utilize more efficiently than the other types of phytoplankton the low levels of nutrients which become available due to regeneration.

The genus Circeis St-Joseph was based upon C. armoricana St-Joseph (1894), but Caullery & Mesnil (1897) suggested that the latter is a mere variety of Spirorbis spirillum (L.), which Chamberlin (1919) therefore regarded as the type of the genus. These two species are indeed closely related to each other, but distinguished by the sculpturing of the collar setae (Knight-Jones, Knight-Jones & Al-Ogily, 1975). They belong to a genus which is very distinct from Spirorbis, as was pointed out by Knight-Jones, Knight-Jones & Kawahara (1975), who regarded C. armoricana as the type species.

In a series of laboratory experiments designed to create conditions under which the dispersal and feeding hypotheses of climbing in Hydrobia ulvae would predict opposing results, significantly larger numbers of snails climbed (a) food-bearing sticks than non-food-bearing sticks, (b) in 100% sea water than in 41% sea water, and (c) in the dark than in the light. The first two of these results are in accordance with the hypothesis that climbing is not a distinct behavioural activity but is merely normal crawling/browsing behaviour carried out in a vertical plane; they are in disagreement with the hypothesis that climbing is undertaken in order to facilitate dispersal away from unfavourable conditions. The third result is neutral in respect of the two hypotheses, but is explicable in terms that activity during the night is advantageous because of lowered rates of vertebrate predation.

Phytoplankton data collected between 1964 and 1974 at three stations in the western English Channel were analysed by the multivariate method of correspondence analysis. The data comprised counts, logarithmically transformed, of 126 taxonomic groups in 700 samples from different depths. The first three axes from the correspondence analysis explained only 17% of the total variation, but the sample positions on these axes showed a clear mean seasonal cycle, slightly different at each station. The species fell into ten groups according to their position on the axes and to their seasonal occurrence. Differences in the position on the axes of samples from different depths on the same occasion correlated well with the temperature structure of the water column. No clear long-term trends were apparent although there were obviously large differences from year to year. The results provide a mean seasonal pattern of species succession on a quantitative basis which can be used to compare counts from different areas or to identify changes in the same area.

Ergenstrema mugilis Paperna, 1964, the only member of the genus, has been collected in the Mediterranean from the gill rakers of the thin-lipped grey mullet Liza ramada (Risso, 1810) by Paperna (1964) and Lambert & Sanfilippo (1977); this parasite, under the name of ‘Dactylogyridea sp.’, was collected also from the same microhabitat of the same host from the coast of Albania by Ergens (1960). At Plymouth, parasites clearly belonging to the genus Ergenstrema have been collected from both the gill rakers and lamellae of a different host, the thick-lipped grey mullet Chelon labrosus (Risso, 1826).

A new species of Chrysochromulina Lackey with exceptionally long cylinder-scales distributed evenly over the cell is described and illustrated with electron micrographs of shadowcast whole mounts of wild material from the Galapagos Islands, South Africa and the English Channel. In all cells, the cylinder-scales are underlain and outnumbered by highly characteristic plate-scales, each with a conspicuous infra-marginal ridge on the distal face. Some consistent dimensional and other differences between periplasts from Africa and the Galapagos Islands are noted, with the British equivalents approximating more closely to the former though with minor differences from both. The observations are interpreted in a preliminary way, but further comment including comparisons with other taxa will follow.

Large numbers of Micromesistius poutassou were caught in the English Channel during the spring of 1979. Later in 1979 and in the early months of 1980 smaller numbers were recorded from the southern North Sea where this species has rarely been recorded before. The M. poutassou were accompanied by small numbers of T. esmarkii in the eastern English Channel but no T. esmarkii were found in the southern North Sea. T. esmarkii were taken off Plymouth on two occasions in 1977 and more regularly since 1979. M. poutassou has been recorded there sporadically since 1957. Both species were caught in considerable numbers around the Scillies in 1977 and 1978. The invasion of the English Channel by M. poutassou in 1979 may have come from the Bay of Biscay rather than the Celtic Sea, but the appearance of T. esmarkii in the Plymouth area since 1977 may be a result of changes in the ecosystem since 1964.

In a search for phytoplanktonic algae which may condition water masses by excreted metabolites monocultures of 29 species of diatoms and flagellates, also of one sedentary alga, were tested with developing eggs and larvae of two species of sea-urchin and of a polychaete. Results indicated that about half of the algal species examined, using both unfiltered cultures and filtrates from them, probably do not produce metabolites affecting development of the three animal species employed in this work. Others were harmful or favourable to them in various ways. One flagellate species in particular, Olisthodiscus luteus N. Carter was of outstanding interest, with effects on larvae varying from toxic to favourable according to culture density and amount of dilution with normal sea water. Ancillary experiments eliminated the possibility that excessively high or low pH could be responsible for observed effects, while others showed that in a semi-toxic environment crowding of eggs and larvae can be beneficial but not in non-toxic media. In the main experimental search for possible effects of metabolites, eggs and larvae were never crowded.

In investigating the parasites of adult thick-lipped grey mullets Chelon labrosus (Risso, 1826) at Plymouth these fishes were found to be infected exclusively with an ancyrocephaline gill monogenean identified as Ligophorus angustus Euzet & Suriano, 1977. When, at a later date, some juvenile C. labrosus were examined ancyrocephalines were again collected; however, quite unexpectedly, these parasites were not juvenile L. angustus but belonged exclusively to a new species of ancyrocephaline subsequently reported as Ergenstrema labrosi Anderson, 1981.

It seemed then that there might be a situation of considerable biological interest in which young fishes were characterized by one host-specific monogenean and older mullets by another. Although a change in the species composition of the total parasite fauna of mullets with age has been reported previously by Reshetnikova (1955) for golden grey mullet Liza aurata of the Black Sea, a change of monogenean species has never previously been recorded.

From an examination of the literature (e.g. Hickling, 1970) on the life history of the British thick-lipped grey mullet it was inferred that the situation described above might be associated with the migratory habits of the fish and in particular the different environments inhabited by young and old mullets; while there may be many factors (e.g. oxygen, temperature, pH, etc.) which differ between the open sea and tidal pools, inhabited by old and young fishes respectively, the most obvious one is that of salinity. Hence, in addition to establishing the identity and frequency of the ancyrocephaline infections with host age, it was decided to make investigations on the salinity tolerances of L. angustus and E. labrosi.

As aids to the phyletic interpretation of the newly described Chrysochromulina pachycylindra Manton et al., some hitherto unrecorded gatherings of C. microcylindra Leadbeater and C. cyathophora Thomsen, from South Africa and South Alaska respectively, are introduced, thereby amplifying the type descriptions of both species, which were previously known only from Europe. Characters shared between C. pachycylindra and C. microcylindra are numerous, including a capacity for transverse fracture of their cylinders not previously noted in the latter. This suggests an exceptional degree of affinity between these two species in spite of gross differences in relative dimensions of different parts of their respective cylinder scales. On the other hand the general resemblance between C. microcylindra and C. megacylindra (Leadbeater, 1972), previously noted, is unaffected by these findings and it is concluded that all three species could be treated as a closely related subgroup within the genus Chrysochromulina. In contrast, C. cyathophora is shown to be so different as to be interpretable only in terms of parallel evolution from a separate prototype source, the plate-scales in particular being so far unique in the genus in being thin, rimless, peculiarly patterned and convex when seen in section. The mere presence of cylinder-scales is thus seen to be insufficient evidence of phyletic affinity unless confirmed by other characters, among which the details of the plate-scales are probably the most important.

A numerical model is used to derive both the S2 and M3 tides for the shelf seas around the British Isles. The M2 tide was run with the S2 tide in the presence of quadratic friction. It was found that quadratic friction marginally overdamps the S2 tide. A further approximate representation of the S2 tide was obtained from a model in which the quadratic friction term was replaced by a linear frictional coefficient in a tensor form based upon the M2 tidal currents derived from the spring-neap simulation. These simulations form the basis for interpreting the M2/S2 ratios and phase differences that occur on the north-west European shelf.

The sterol biochemistry of the highly advanced molluscan class – the cephalopods – is poorly understood. Few analyses of their component sterols have been published in which GC-MS has been employed (Voogt, 1973; Idler et al. 1978; ApSimon & Burnell, 1980) and these have only involved 5 species.

From the available data the cephalopods appear to have a much simpler sterol make-up than the other less-advanced molluscs. Cholesterol appears to be easily the predominant sterol (ca. 90%) with minor amounts of up to 10 other common marine sterols. Of the species analysed, four (Sepia officinalis, Octopus vulgaris, Eledone aldrovandi and Illex illecebrosus) had a very similar major and minor sterol composition. Only the more primitive Nautilus sp. (Idler et al. 1978) had a noticeably different minor sterol composition.

Voogt (1973) reported cephalopods to be able to synthesise sterols though molluscs generally appear only to be able to carry out this biosynthesis slowly (Goad, 1978). Cephalopods are extremely active carnivores and thus would be expected to have a diverse diet. If their component sterols are of a dietary origin, a considerable variation in their minor sterol composition might be expected on the basis of the range in sterol composition reported for pelagic organisms (e.g. Morris & Culkin, 1977), many of which may be possible dietary components.

Detailed knowledge however of cephalopod diets is limited. Quite apart from the fact that healthy specimens are rarely caught in nets, those that are caught often feed voraciously on the other organisms trapped in the net prior to being brought on board for examination.

It is suggested that the cumulative view of growth in which some index of biomass is plotted against time tends to obscure temporal variations in the growth process that might provide evidence of how it is controlled. Experiments with the colonial hydroid Campanularia flexuosa show that the action of a growth control mechanism can be demonstrated by considering changes in specific rates of growth determined at frequent intervals in time. However, it is also necessary to disturb the growth process slightly in order to initiate the action of the control mechanism, and having done so, to isolate the effect of the disturbance on growth and thus the action of the control mechanism. This is done by expressing the specific growth rate of organisms whose growth is disturbed as a percentage of that of control organisms of the same age.

Herring larvae, when they are about 30 mm long, swallow air and fill their auditory bullae with gas. It has been shown earlier that this is associated with a great increase in sensitivity to changes in hydrostatic pressure. Here we show that it is also associated with the appearance of a startle response to noises.

At this stage of development, the utricular maculae are fully developed. However, the bullae are bounded by thin walls which are poorly calcified and the bulla membranes are thin and contain little elastic tissue. None the less the high-frequency cut-off in the mechanical responses to oscillating pressures is as high as that of the adult.

Valve structure was investigated using light and scanning electron microscopy and each valve was found to comprise four layers; periostracum (dorsal), tegmentum, articulamentum and hypostracum (ventral). The penetration of the valves by the aesthetes within channels is described and three distinct types of aesthete channels are identified, namely, multiple branch aesthete channels, slit ray aesthete channels and jugal sinus aesthete channels. The distribution of the different aesthete channels within the various valves is defined and their relationship with the valve external sculpturing is described. The process of valve growth by marginal increment is discussed in relation to the formation of the aesthetes.

The behavioural experiments described in this paper were carried out to complement earlier physiological work on the acoustico-lateralis system of the clupeid fishes. Previous work, summarized by Blaxter, Denton & Gray (1981a), has shown that the sense organs of the clupeid utriculus are highly sensitive to alternating pressures. Since the utriculus signals the polarity and amplitude of each peak in a complex pressure wave form separately, independently of the rate of change of pressure over a range equivalent to a frequency band of 30–800 Hz, it is well suited to give information on brief noises. In the clupeids the lateral line is hydrodynamically connected with the ear and we have suggested that the signals arising from the inner ear and the neuromasts of the lateral line are used in conjunction to provide information about direction and range.

A numerical model is used to derive the N2 tide around the British Isles. The model can derive any semidiurnal astronomical constituent in about 5 tidal cycles to > 90% accuracy. This simulation demonstrates the importance of quadratic friction and frequency in determining the relative positions of the N2, M2 and S2 amphidromes.

The mantles of the small squid Alloteuthis, the larger Loligo, and the cuttlefish Sepia contain an elaborate framework of connective tissue fibres running in different planes. Some of these fibres are apparently elastic. The circular muscle fibres which provide the power stroke in mantle contraction are of two types. Inner and outer mantle zones consist of well-vascularized mitochondria-rich fibres, whereas the central zone contains only mitochondria-poor fibres with a sparse vascular bed. Nerve terminals on the two fibre types are similar. The radial fibres opposing the circular fibres are of the same type as the central fibres, at least in the mid-region of the mantle. It is suggested that the central fibres are involved in escape jetting contractions, and that the fibres of the inner and outer zones are used during rhythmical respiratory contractions.