The physiological basis for the previously reported differences in the rate of respiration between high-shore-level and low-level populations of Patella vulgata in the summertime has been investigated in relation to distribution differences between this species and P. aspera.

The respiration rate of both P. aspera and low-level P. vulgata is low in the winter but increases in the spring to a level which is maintained until the post-spawning period in the autumn. The respiration rate of high-level P. vulgata does not increase in the spring but remains at the low winter level. The inter-population difference in rate of respiration therefore appears in the spring and is maintained until the autumn.

The difference in rate of respiration cannot be accounted for by differences in the amount of non-respiring tissue in equal weight individuals and is phenotypic and not genotypic, as indicated by transplantation experiments. These experiments also rule out the possibility of differences in age of equal weight individuals from the two populations being responsible.

Respiration rate was found to be a function of both intertidal height and of the abundance of algal food in the habitat. It is suggested that the low-level population of P. vulgata should be regarded as the normal form and that the low respiration rate of high-level limpets in the summer represents a form of adaptation to the stresses of their habitat. It is possible that both nutritional level and temperature acclimation are important in this, and it is speculated that inability to reduce the level of metabolism may be one factor preventing the colonization of high-shore-level habitats by P. aspera.

An important function of the gastropod shell is to protect the body against attack by predators. If the shell of a whelk is broken away and the soft animal is then offered to a hungry cod, it is eaten readily. Many successful gastropods, however, lack an external shell as adults (although it is certain that all have evolved from shelled ancestors) and might be expected to be eaten by fish as readily as is the naked body of a broken whelk. The purpose of this paper is to describe part of an investigation into whether this is in fact true.

An acute toxicity threshold of 0·09–0·10 ppm added copper was determined for specimens of Mytilus edulis from the Menai Strait which were exposed to copper (as CuSO4) in a flowing sea-water system.

Results are presented which show that the closure response of the mussel to added copper is a three-part process. First, a sharp adduction of the shell valves is seen at a mean total copper concentration of only 0·021 ppm, then as the copper concentration rises, ‘testing’ behaviour is observed and finally the shell valves close to isolate the animal from its environment. The complete valve closure mechanism only operates at added copper concentrations of 0·2 ppm or more. The initial behavioural reaction of valve adduction at low concentration occurred at a significantly higher mean total copper concentration (0·16 ppm) in mussels which had been previously acclimated to 0·02 ppm total copper in sea water for 10 days.

Dissolved amino acids, in both the free state and combined as polypeptides, play an important part in the marine biochemistry of nitrogen. These compounds are excreted by phytoplankton (Fogg, 1962, 1966; Stewart, 1963; Hellebust, 1965) and zooplankton (Johannes & Webb, 1965; Webb & Johannes, 1965) and are utilized by algae (Syrett, 1962), bacteria (Proom & Woiwood, 1949) and marine invertebrates (Stephens & Schinske, 1961). Experiments with cultures have shown, indeed, that some species of phyto-plankton will not grow, or grow only with difficulty, if certain amino acids are absent (Harvey, 1938; Provasoli & Gold, 1957; Droop, 1957, 1959, 1962). In addition to their direct biochemical role, amino acids may also serve to complex trace metals, such as copper and iron, and keep them readily available for assimilation by marine organisms (Harvey, 1938; Fogg, 1959; Provasoli, 1963; Kent & Hooper, 1965; Saunders, 1957).

Ten stations, from high water to low water, were investigated along a mud-flat in the Bristol Channel.

The mud was analysed for water content and grade. The values suggested, with other observations, that the stations were distributed over two different areas.

Quantitative analysis of both macrofauna and microfauna revealed a dense mud population.

The operative ecological factors, including the food cycle, are defined.

Oil/water extraction systems have been devised to study the lipid solubility of metal ions in sea water. Group B metals such as Cu, Zn, Cd, Hg appear to form inorganic complexes in saline solutions that are very lipid soluble. The implications of this are discussed in terms of the penetration of metals across cell membranes.

The conchocelis-phase of Porphyra tenera Kjellman has been grown in in vitro culture, and subjected to a variety of daylength treatments.

Details of the culture apparatus designed for these treatments are given, and quantitative techniques, which have been devised for estimating the growth and reproduction of the alga, are described and discussed.

Growth was found to be directly proportional to daylength within the range 8–16 h, but abundant sporangia were only formed in daylengths of 10 h or less. The interruption of a 16 h dark period by 1 h of light completely inhibited the production of sporangia, but exposure to 8 short-day cycles, followed by long days, induced the formation of as many sporangia as were found after 25 short days. These results are discussed with reference to the photoperiodic responses of flowering plants.

On hatching, larvae of herring, Clupea harengus L., showed increased activity to washings and extracts of the nauplii of Balanus balanoides and to glycine and proline whichare major constituents of the free amino acid pool of Balanus. Older larvae, which were fed on the nauplii of Anemia salina, showed a response to extracts, but not to washings, of this prey; they also responded to six amino acids. The active constituents of prey extracts were found to be dialysable. Surgical section showed the olfactory system was responsible for behavioural responses in herring larvae of 21 mm (total length) to extracts of Anemiasalina. At all stages of larval life, herring showed increased activity to washings of other herring larvae. Juvenile herring showed a preference for a part of a tank containing water in which other juvenile herring had been held.

Enclosures of various sizes and configurations have been employed to maintain natural planktonic communities and to examine their responses to pollutants (e.g. Menzel & Steele, 1978; Steele, 1979). Studies on feeding, growth, and mortality of larval fishes, at times conducted in conjunction with pollution experiments, have also been successfully conducted in large enclosures (Koeller & Parsons, 1977). Implicit in these and other comparable studies has been the expectation (or hope) that a balance could be achieved between the advantages and difficulties inherent in more traditional field and laboratory studies. Field studies offer the realism of working with the natural assemblage with its many interacting components and links, but also suffer the disadvantage associated with a turbulent and advective system, which generally makes the repetitive sampling of the same populations impossible. Laboratory studies reverse the balance; control and definition of the components are gained at the expense of realism. The use of large containers represents a hybrid approach characterized by a partial control over a moderately realistic ecosystem. In the ideal case, the use of large containers allows sufficient control to permit experimental manipulation of (and the testing of hypotheses concerning) planktonic assemblages which are sufficiently realistic to permit extension of the experimental results to the ‘real world’.

In the Celtic Sea, to the south of Ireland, water in some winters becomes sufficiently cooled and heavy to flow to the edge of the continental shelf and to run down the continental slope to a depth of several hundred metres. A theory of the phenomenon, termed ‘cascading’, has been developed. Three winters have been examined in detail.

In February 1927 much water, heavy enough to cascade, was present in the Celtic Sea and also in the English Channel. A probable course and speed of the cascading water over the shelf has been established. Since there were few observations of salinity and temperature over or beyond the slope, and none of oxygen anywhere, the theory cannot be completely established on the basis of the 1927 observations, full though they were.

A detailed illustrated key to the identification of the European species of the genera Palaemon and Palaemonetes is provided. This key has been elaborated taking into account recent changes in the species composition of both genera for European waters, such as the invalidity of Palaemon garciacidi, which is a synonym of P. longirostris, and the presence of an introduced species, Palaemon macrodactylus that has been recently recorded at different localities along the Atlantic coast. The key is based on external morphological characters to facilitate its use by non-specialists. Data on the coloration, habitat and distribution of all species are also given.

Ten species of marine strombidiid ciliates were identified after protargol staining plankton samples. The taxonomic redescriptions include a diagnosis for Tontonia gracillima Faure-Fremiet, 1924, Strombidium wulffi (Wulff, 1919) Kahl, 1932, Strombidium acutum Leegaard, 1915, Strombidium constrictum (Meunier, 1910) Wulff, 1919, Strombidium compressum (Leegaard, 1915) Kahl, 1932, and Strombidium sulcatum Claparede & Lachmann, 1858. Four new species, Strombidium dalum n.sp., Strombidium epidemum n.sp., Strombidium rhynchum n.sp., and Strombidium tressum n.sp., are defined based primarily on the characteristics of the anterior oral polykinetids, numbers of oral polykinetids, and presence of anterior protuberance.

Hermit crab populations have been described in different habitats and latitudes but few studies focused on coexisting populations. Such information is especially important to evaluate the effect of coexistence in the population biology of such organisms. This study was done in the intertidal region of Pernambuco Islet, São Sebastião Channel, south-eastern Brazil. Random samples of crabs were taken monthly during one year to evaluate their size and sex. The three coexisting Clibanarius populations (C. antillensis, C. sclopetarius, and C. vittatus) showed similar patterns of sex ratio (skewed for females), sexual dimorphism (males larger than females), recruitment (February to June) and population growth but differed in size structure (Cs>Cv>Ca) and reproductive activity over the year. Population growth was estimated using the von Bertalanffy growth function (VBGF) and revealed that the growth of these three populations was strongly reduced from August to January and that longevity varied from 42 to 48 months. Clibanarius antillensis showed continuous reproduction with high frequency of ovigerous females over the year while C. sclopetarius and C. vittatus had a reproductive peak in April and absence of ovigerous females in August/September. Coexistence seemed to influence population biology of these hermit crabs, given the relationship of their reproductive periods and growth patterns to the shell adequacy to the crabs. The overlap in reproductive peaks and recruitment periods may strengthen competition for shells. Comparisons of the reproductive patterns of the hermit crab populations recorded to date emphasize that reproduction and, consequently, life strategies of hermit crabs are not directly dependent on taxonomic or geographical proximity, but on their evolutionary histories and on local processes acting on each assemblage or population.

In work performed during the period February–October 1996, about 47 species of ciliates were detected in the communities of Aufwuchs, or periphyton, colonizing glass substrates submerged in three sites in the Lagoon of Venice, two in the urban area of Chioggia and one at a mussel-farming site. The ciliate communities were composed of sessile forms of Peritrichia and Suctoria and of motile ciliates, belonging especially to Hypotrichia and Karyorelictea. Four species of the peritrich Zoothamnium and the suctorians Acineta tuberosa and Ephelota gemmipara are reported here for the first time in the Lagoon of Venice. The richest ciliate communities were recovered at 60 cm from the bottom. Processed by multivariate analysis, data of samplings performed up to day ten from the positioning of glass slides indicated significant differences in biotic and physico-chemical parameters, according to season. The first data did not give definite indications on the possibility of using ciliates colonizing solid surfaces to assess the quality of this peculiar environment.

Yellow-phase American eels, Anguilla rostrata, were displaced 10–17 km between tidal fresh water and salinity-stratified water and followed to determine the degree of home site fidelity, swiftness of homing and whether environmental factors affect orientation or homing behaviour. Twenty-one eels were tracked continuously (eight eels displaced up the estuary, eight down the estuary and five controls) in the Penobscot Estuary, Maine, USA for 4–80 h each, while recording position every 20 min. Nine of the 16 displaced eels (56%) returned to their capture site either during the track or shortly afterwards. Three of the remaining seven eels made substantial progress towards their capture site within the time observed. Eels homed with equal frequency whether displaced up or down the estuary in an average of 220 h ±87 (SE). After release, no eel moved farther away from its capture site. The eels were active mostly at night but used only the appropriate tidal currents rather than directed swimming to move about their home range and to home. Control tracks provided a home-range estimate in this habitat of 6.7 ±1.6 km of estuary or 325 ±64 ha. Lunar phase or position of the moon did not appear to influence either homing behaviour or activity patterns. This study shows that orientation and homing to a specific site in eels occurs relatively quickly and with no initial errors in orientation.

Reproductive cycles are described for subtidal and intertidal populations of the, starfish Asterias rubens L. and for a subtidal population of the starfish Marthasterias glacialis L. on the south-west coast of Britain. Intertidal A. rubens had a clearly defined reproductive cycle with spring-early summer spawning. Pyloric caecum indices were inversely related to gonad indices. Subtidal A. rubens had lower gonad indices and less seasonal variation in the pyloric caecum indices. Gonad indices of M. glacialis suggest few animals in the population studied were breeding, but it is likely that this species also spawns in summer.

Plankton samples and larval rearing studies suggest a planktotrophic pelagic life of approximately 90 days for A. rubens. Field observations and laboratory experiments show larvae settle on a wide range of substrata. Recruitment to an intertidal population of A. rubens at Hollicombe Reef occurred in July 1980 and September 1981. Growth of juvenile starfish was followed for 17 months. Juvenile starfish feed carnivorously at the completion of metamorphosis. Early growth is rapid; however, there is a reduction in the growth rate during winter months. Feeding and growth of juvenile A. rubens is compared with published data on juvenile starfish of other species.

The deep sea prawn, Pandalus borealis Krayer, is fished extensively in Norwegian, Swedish and Greenland waters, some 4000 metric tons being caught annually, having a value of about £800,000. Its biology has been investigated by various workers in these countries. Comprehensive accounts have been given by Wollebaek (1903), Hjort & Ruud (1938), Rasmussen (1953)and Horsted & Smidt (1956). Despite this, relatively few populations have been sampled at regular intervals throughout a year. In high latitudes where much work has been carried out, ice, for varying lengths of time, prevents stocks from being sampled. Rasmussen (1942, 1949, 1953) has shown that the life history of P. borealis varies with locality in a range from southern Norway to Spitsbergen. When P. borealis was found in numbers in deep water off the Northumberland coast advantage was taken to investigate the biology of the species at the southern limit of its eastern Atlantic distribution and to compare the results with those of other workers. Knowledge of the biology of the prawn now covers the whole of its north-south distribution and some account of this is given. In addition, the study gives information on a population that has not been fished commercially and provides a more complete picture of sex reversal than has been obtained hitherto.

The seasonal changes in the respiration of Calanus are considerable and are, on the whole, related to size and therefore to weight. Length alone is not enough to account for the differences since ripe females, although the same length as unripe, have a markedly higher respiration. In addition, by taking samples of large and of small Calanus of a single stage, it was shown that the difference in respiration was small. Neither is weight by itself enough to account for the difference between groups. Stage V Calanus are, for a given length, heavier even than ripe females and yet their oxygen utilization is low. In this instance, however, an important part of the weight consists of fat which is a food reserve and not actively metabolizing. The difference of weight between ripe and unripe females is not known, but ripe females must be heavier and this will account for their higher oxygen consumption.

Although the oxygen and therefore the food required during the spring months is high, at that time the phytoplankton is at its maximum and is probably sufficient to fulfil all needs. Egg-laying depends on the food supply and it is then that Calanus starts breeding. In winter, on the other hand, the Calanus is present as Stage V and oxygen consumption is little more than half what earlier figures suggested. No ‘hibernation’ seems to take place but the population is living in an economical way for Stage V use little oxygen, live in deep water and do not undertake diurnal vertical migration.

At 10° C ripe female Calanus will require daily from 3·9–7·2% of their body weight as dry matter in summer and from 2·8–6·7% in winter. Stage V will require 2·3–3·1% in summer and 1·4–3·3% in winter. The higher values are for carbohydrate and the lower for fat.

It is difficult to believe that Calanus in winter will be able to find enough food by filtration alone. The fact that in the winter months it depends more on predation may account for its survival.

INTRODUCTION

Ecological studies of Eider Somateria mollisima, Shelduck Tadorna tadorna, Redshank Tringa totanus [Aves], and Flounder Platichythys flesus [Osteichthys], in the estuary of the River Ythan, Aberdeenshire, have entailed investigations of their food requirements, and there is evidence to suggest that Hydrobia ulvae [Gastopoda], as a numerous food item common to all, may in some instances have influenced their breeding success and numbers in some years. In order to get an index of abundance of Hydrobia, the Ythan population has been sampled four times a year since May 1963. The full results of this sampling programme are being published separately. At the same time data on the annual cycle of Hydrobia were collected from one area (transect number 3, Fig. 1), on the assumption that breeding onset and intensity would be the same in other parts of the estuary in any one year.

A comparison of body size and flipper size was carried out on green turtle (Chelonia mydas) hatchlings produced from natural nests at two beaches on Ascension Island, South Atlantic and one beach in northern Cyprus in the Mediterranean (N=18 nests; N=180 hatchlings). Hatchlings from Ascension Island were significantly larger and heavier than hatchlings in Cyprus, a likely consequence of maternal size effects. Incubation temperature appeared to influence body size of hatchlings on Ascension Island with higher temperatures producing smaller hatchlings. Both hind and fore-flipper area scaled positively with body size. In proportion to body size, hind-flipper area appears relatively consistent among the Atlantic populations but is smaller than hatchlings measured in Hawaii.