Adult female Calanus helgolandicus Claus immersed for 24 h in sea-water solutions of [1-14C]naphthalene accumulated a detectable quantity (3.6 pg/animal) from concentrations as low as 0.10 μg/1.

Feeding experiments using barnacle nauplii or diatoms as foods showed that the dietary route of entry was more important quantitatively than direct uptake from solution in that in order to ensure that the same quantity of radioactivity in the animals was attained by the two routes the level of hydrocarbon in solution had always to be far greater than that present as paniculate food. Relevant to these observations was the further finding that after naphthalene had been accumulated directly from solution in sea water depuration was rapid and only a small fraction, less than 5%, of the original radioactivity could be detected after 10 days: by contrast, when the hydrocarbon was taken up by way of the food depuration was much slower, so that at the end of 10 days about a third of the original level of radioactivity still remained in the animals. Short-term experiments in which Calanus were fed on labelled diets for 24 h under bacteria-free conditions showed that at the end of this period over 90% of the radioactivity in the animals was present as unchanged naphthalene. However, more than two thirds of that released by the animals was in some form other than the hydrocarbon, a finding consistent with the view that Calanus is able to metabolize it.

INTRODUCTION

Molluscan age determination has long been the subject of both biological and paleonto-logical research (Mossop, 1922 a, b; Haskin, 1954; Merrill, Posgay & Nichy, 1965; Andrews, 1972). Several workers have listed difficulties associated with traditional methods of determining the age of an organism based upon surface shell morphology (Pannella & MacClintock, 1968; Farrow, 1971, 1972; Berry, 1971). Others, such as Craig & Hallum (1963) have attempted, with moderate success, to circumvent these problems statistically by using size-frequency relationships, but such methods are of little value in age analysis of isolated individuals. The principal difficulty encountered in shell surface analyses arises from an inability to distinguish spawning and disturbance lines from annual marks. Problems associated with this separation have been reduced over the past decade by the discovery of daily and tidal periodicity structures within the shells of numerous Recent and fossil species of pelecypods (Barker, 1964,1970; Pannella & MacClintock, 1968; Clark, 1968; House & Farrow, 1968; Farrow, 1971, 1972). The biological and paleontological significance of such growth increments have been discussed at length by Pannella & MacClintock (1968), Barker (1970), and Clark (1974). When present in continuous sequences, these periodicity structures facilitate an accurate age determination of individual specimens.

INTRODUCTION

The herring Clupea harengus L. and sprat Sprattus sprattus (L.) are physostomatous teleosts with narrow ducts connecting the swimbladder to both the gut and cloaca. With other clupeoids these two species were of great interest to the anatomists of previous generations because of the further tubular connexions between the swimbladder and air-filled otic bullae close to the labyrinth of the inner ear. Together with the Ostariophysi, which have a chain of Weberian ossicles between the swimbladder and the inner ear, the clupeoids were thought to have enhanced hearing compared with many other teleosts as a result of coupling the ear to the swimbladder.

Despite such interest in the system the earlier literature is very fragmented, with the descriptions ranging over at least a dozen clupeoid species, and much of the work was done on fairly advanced juvenile or on adult fish. Ridewood (1891) examined the swimbladder-inner ear relationship in adult herring, pilchard Clupea pilchardus, sprat, shad C. alosa, twaite C. finta and anchovy Engraulis encrasicholus; Tracy (1920) made a similar study of the American Atlantic clupeoids – the shad Alosa sapidissima, alewife Pomolobus pseudoharengus, summer herring P. aestivalis, fall herring P. mediocris and menhaden Brevoortia tyrannus and O'Connell (1955) of the Pacific sardine Sardinops caerulea and anchovy Engraulis mordax. Wohlfahrt (1936) considered the total swimbladder-inner ear-lateral line relationship in 100–120 mm pilchards, recognizing the much less obvious connexion between the perilymph and the lateral line through a membrane in the skull. The presence of such a connexion had been suggested earlier by Tracy (1920).

Many types of plankton net have evolved for various sampling needs, but in the main they are designed for sampling in mid-water, or over fine particulate substrates where they can operate within a sledge frame. The conventional plankton nets are mostly towed behind a boat and can only be used in areas where there are no obstacles to impede their course. Many nets are described in the literature and the reviews by Tranter et al. (1966) and the UNESCO monograph on zoological sampling methods (Tranter, 1968) give further details. Nets for taking benthic plankton are generally mounted on a sledge frame and either towed behind a boat (Russell, 1928; Wickstead, 1953), towed in shallow water by persons wading and pulling the net behind them (Colman & Segrove, 1955) or pushed by SCUBA divers (Fager et al. 1966). However, all these methods still leave the need to sample rocky areas and irregular substrates where conventional methods are not possible. Such areas are often extremely rich in planktonic organisms which appear to accumulate within the shelter offered by gulleys and depressions in the bottom topography (personal observation). Often species associated with inshore algal belts are poorly represented in conventional offshore plankton samples (Russell, 1973), and it may be that such species spend much of their larval existence close in shore or in association with shallow water reefs. The present paper describes a diver-controlled plankton net which has been designed to sample rocky areas. By having direct diver control this plankton net can be used to sample other areas where conventional methods are not appropriate.

It has long been known that the corneas and lenses of some vertebrates are yellow in colour, and therefore affect the spectral quality of the light that reaches the retina. Various functions have been attributed to such intraocular yellow filters, such as the reduction of scattered light, chromatic aberration, and ‘glare’; and also possibly an increase in the contrast of some objects viewed against certain backgrounds (see Walls & Judd, 1933; Muntz, 1972, for reviews). It is of course likely that the yellow filters of different animals serve different functions, but it is also clear that in all cases, by absorbing a proportion of the incident illumination, they must reduce the animal's absolute sensitivity. In agreement with this, there is a general tendency for animals with yellow filters to be diurnal, and occupy brightly lit environments. Among the fishes in particular, there is a tendency for yellow lenses and corneas to be especially common among diurnal groups, which avoid the consequences of the inevitable loss of sensitivity by remaining inactive at night (Muntz, 1973).

INTRODUCTION

This analysis of cephalopod remains, particularly the mandibles or beaks, from sperm whales caught off Iceland is one of a series made by the authors on remains from various geographical regions including Madeira (Clarke, 1962a), Spain (Clarke & MacLeod, 1974), Western South America (Clarke, MacLeod & Paliza, 1976, South Africa, Western Australia, the Antarctic and the South Atlantic (Clarke, 1976, 1977). Other workers have described similar collections from New Zealand (Gaskell & Cawthorne, 1967; see also Clarke, 1976, 1977) and the North Pacific (Akimushkin, 1954; Betesheva & Akimushkin, 1955; Tarasevich, 1963). The present analysis has depended upon a development in the technique of identification of cephalopod lower beaks from an early search for criteria (Clarke, 19626) to a point where many species can be identified from lower beaks (Mangold & Fioroni, 1966; Iversen & Pinkas, 1971; Clarke, 1977).

INTRODUCTION

The preceding paper (Allen, Blaxter & Denton, 1976) describes the development of the swimbladder-inner ear-lateral line system of the herring.

In the larval stage of herring the pro-otic bullae start to develop at a body length of about 18 mm. Between 18 and 30 mm the bullae become filled with gas. At 26 mm the lateral recess membrane starts to develop, becoming silvered at about 42 mm. The lateral line develops between 19 and 45 mm. The swimbladder silvers and contains gas from about 38 mm. The adult system is complete at 50–60 mm body length, some four months after hatching.

This paper concerns the system in its intermediate stages of development. It examines the problems of how the bullae are filled with gas and how the gas spaces are maintained. It gives evidence on the possible roles of the gas-filled spaces as hydrostatic pressure receptors and as aids to buoyancy and discusses the limitations of the system before it can gain or lose gas to a gas-filled swimbladder.

The salinity preferences of the amphipods studied were found to correlate with distribution. Marinogammarus marinus, a marine species, showed a strong preference for higher salinity levels, the estuarine Gammarus duebeni showed little avoidance of any particular sea water concentration, and the freshwater Gammarus pulex displayed strong preference for dilute media

Tolerance experiments showed that the preference behaviour of M. marinus was not caused by lethal effects of salinity.

Observations on M. marinus suggested that the behaviour involved components of both preference and avoidance.

In M. marinus the choice is made on the basis of total osmolarity of the medium, not on its organic or ionic content alone.

Ablation of the upper and/or lower antennae had no effect on salinity choice in M. marinus, and acclimation to 50% sea water did not alter the preference for full sea water.

It is suggested that behavioural responses which confine animals to areas well within their physiological salinity limits promote survival in aquatic environments which may undergo fluctuations in salt concentration.

We frequently require sensitive bioassay techniques with which to study the effects of marine contaminants at environmentally realistic concentrations. Unfortunately, it is difficult to achieve sensitivity and precision in an organism amenable to indefinite periods of laboratory culture. Results from different laboratories are often extremely variable: LC50 values for the same substance, using the same organism, may differ by two or even three orders of magnitude (Wilson, Cowell & Beynon, 1975). Moreover, some of the most sensitive bioassay organisms require nutrient media, which may alter the availability and toxicity of metals by complexing them (Jones, 1964; Kamp-Nielsen, 1971; Hannan & Patouillet, 1972) and often contain metal impurities at significant levels (Albert, 1968; Steeman Nielsen & Wium Anderson, 1970). The object of the work reported here has been to develop a technique by which these problems might be minimized or avoided. Hydroids were chosen as bioassay organisms for a variety of reasons. They are tolerant but sensitive to small variations in their chemical environment. Techniques for growing hydroids are simple and they can be cultured under conditions of near optimal temperature, salinity and food supply, thus minimizing the errors frequent in bioassay work arising from variations in the history of the test organisms, their size, sex or physiological state. An important source of variability in all work with organisms is that inherent in the genetic material, but with hydroids this can be avoided by the use of a single clone.

INTRODUCTION

Ascidian tadpoles are short-lived, actively swimming larvae. On attachment to their preferred substrates they absorb the tail, and with it all their locomotory equipment. The behaviour is in general geared to the short-term problems of dispersion and settlement (Crisp & Ghobashy, 1971).

The small size of these tadpoles (2 mm in Dendrodoa grossularia, van Beneden, the species used) makes them difficult to handle. Surgical operations on the nervous system (Kasas, 1940), such as we were able to perform on the tadpole-like but larger Oikopleura (Bone & Mackie, 1975) are scarcely feasible here. Nevertheless, it is desirable to know more about the tadpoles’ locomotory organization if only because their possession of the chordate type of locomotory equipment raises interesting questions concerning possible functional parallels and evolutionary origins.

INTRODUCTION

Parasite-induced excess growth, or gigantism, has been reported in several mammals (reviewed by Cheng, 1971) and a fish (Summerfelt & Warner, 1970). Work on invertebrates has centred on size increase in gastropod molluscs associated with infections by larval trematodes (reviewed by Cheng, 1967, 1971). Among these the results have been variable, with some host species showing real gains in body size (soft tissue) (Rothschild & Rothschild, 1939), others initial gains with later stunting (Pan, 1965), and still others gains only in shell thickness (Cheng, 1967). Parasitic castration in other invertebrate groups, not necessarily accompanied by gigantism, has been reviewed by Kuris (1974).

Two new gammaridean amphipods, Crybelocephalus birsteini sp.nov. and Halicoides discoveryi sp.nov., and a new subspecies of hyperiid amphipod, Scina wagleri atlantis subsp.nov. are described from oceanic plankton samples taken off Fuertaventura, Canary Islands.

INTRODUCTION

During the production of china clay, a waste of fine quartz, sand kaolin and mica flakes in suspension is produced. Until recently, only a small proportion of this fine material was retained and settled in lagoons and consequently most of the effluent was discharged. Waste produced in the St Austell area was carried by the Par and White Rivers into Mevagissey Bay (see Fig. 1). In 1968 the china clay industry considered a proposal to combine all its wastes arising in the area and to discharge them into the sea via the White River or if necessary further out to sea by a pipeline. The precise location of the pipeline was not denned at that time but, irrespective of position, deterioration of conditions in St Austell and Mevagissey Bays seemed inevitable.

It is known that vertebrate lysosomes can sequester and concentrate metal ions including copper, mercury (and organic mercurials), lead, zinc, tellurium, iron, nickel, silver and plutonium (Koenig, 1963; Rahman & Lindenbaum, 1964; Scheuer, Thorpe & Marriott, 1967; Vaughan, Bleaney & Williamson, 1967; Verity & Reith, 1967; Barrett & Dingle, 1967; Abraham, Morris & Smith 1967; Slater, 1969; Brun & Brunk, 1970). Allison (1969) states that the accumulation of certain metal ions within lysosomes may labilize the membranes under certain conditions. Furthermore, Goldfischer (1965) suggests that the toxicity of copper may not be fully manifested while it is contained within the lysosomes, but overloading of the storage capacity, or damage to the lysosomal membrane, resulting in liberation of copper into the cytoplasm could lead to cell injury. The haemocytes of Ascidia pygmaea have also been shown to accumulate pentavalent vanadium in a process involving sequestration by lysosomes (Kalk, 1963). It follows that quantitative cytochemical measurements of certain aspects of lysosomal function might permit the detection of responses to toxic materials at concentrations below those to which the whole organism would respond.

The acoustic measurements made during the SOND cruise are presented in the form of vertical profiles of relative scattering coefficient at day and night and its time dependence over sunrise and sunset for the four echo-sounders used. These profiles are compared with the scattering which is calculated would be returned from the vertical distributions of biological samples reported by other workers, but particularly from the distribution ofswimbladder fish analysed by Badcock. The similarities between the calculated and measured profiles support the assumption that swimbladder fish dominate the scattering due to their high target strengths, particularly at frequencies up to and including 36 kHz. By correlating fish sizes, daytime depth, migration behaviour and acoustic scattering several of the layers may be tentatively attributed to particular species. A calibrated echo-sounder in the frequency range up to 36 kHz is size selective, but can nevertheless be useful for looking at broad distributional features. However, because the numerically more abundant small planktonic animals are inadequately represented by the sounder the records are little more than a guide to net sampling programmes.

During his studies on the Cirripedia Darwin (1854) gave much attention to the Chthamalidae, and his views of the species remained unchallenged for many years. Darwin's attitude to speciation appears to have been coloured by his concurrently developing theories of natural selection, and he was especially interested in the existence of wide variation within species. Thus Chthamalus stellatus as described by Darwin consisted of a number of races or varieties, and was of almost worldwide distribution (‘southern England, Ireland, Isle of Man, Mediterranean, Madeira, Cape Verde Is., southern United States, West Indies, Brazil, Rio Plata, Red Sea, Philippines, China, Gulf of Korea, Oregon or N. California’). This distribution has been considerably narrowed in the last 60 years, and recent investigators have raised varieties to specific rank, or described new species and subspecies. In North California and Oregon we now have the full species C. dalli (Pilsbry, 1916); along the eastern coast of U.S.A. we now have C.fragilis (Pilsbry, 1916); in the Caribbean and along the east coast of South America we have C. angustitergum and C. bisinuatus (Pilsbry, 1916; Ross, 1969; Southward, 1975); for the Indopacific region there are now the species C. challengeri and C. malayensis (Hoek, 1883; Pilsbry, 1916); and in the Mediterranean, C. depressus (Poli), which was reduced by Darwin to a variety of C. stellatus, has been raised again to specific rank (Barnes, 1956; Utinomi, 1959; Southward, 1964; Klepal & Barnes, 1975) and is now assigned to the genus Euraphia (Newman & Ross, 1976). Thus except for a few dubious records what remains of Darwin's C. stellatus is confined to Europe, N. Africa and W. Africa (Southward, 1964; Stubbings, 1967). Nevertheless, even such a reduced distribution encompasses several distinct climatic zones, and seems more extensive than the individual ranges of the three species (C. dalli, C. fissus and C. panamensis) found in comparable climatic regions of the N.E. Pacific.

INTRODUCTION

Several authors (Cable & Hunninen, 1942; Dogiel, Petrushevski & Polyanski, 1958) noted that fishes while being kept in aquaria, lose the intestinal parasites with which they had become infested in nature. Up to now no quantitative examinations have been made on this subject. A better knowledge of the behaviour of parasites of fish in captivity seems to be of interest for several reasons.

The possible elimination of intestinal parasites by quarantining the host fish would be of importance in case of parasites which are able to complete their life-cycle in the aquarium and which might provoke mass-infection.

The spatial pattern of the ostracod Cyprideis torosa (Jones, 1850) is aggregated and can be described by the negative binomial distribution. The fit of the observed distribution to the negative binomial is less well for the total number of females because females that are not carrying eggs tend to be independently distributed from both females carrying eggs and males. The aggregations are roughly circular with a radius of about 13 cm and may be themselves aggregated. A method to picture the aggregations is described.