The rations removed by adult and stage V Calanus helgolandicus (Claus) feeding on large cells of the diatom Biddulphia sinensis Grev. were measured using an apparatus especially designed to keep the plant cells in suspension and estimated to reach a maximum of 1800 cells/animal/day at a food concentrationof 11,300 cells/1. A continual flow method was used to study feeding at very low algal concentrations and it was found that the animals still captured Biddulphia at a food level of only 270 cells/1.The animals in the feeding experiments were used at a very low population density (6 copepods/1350 ml.) and the maximum value found for the volume of sea water swept clear – 700 ml./animal/day - was unusually high.The maximum daily rations consumed by each animal were also high, being equivalent to 47–5 % of the body nitrogen and 46–4 % of the body phosphorus. The number of faecal pellets released by the animals increased with the size of ration captured, but the percentage of the ration lost as faecal pellets was fairly constant. In terms of dietary nitrogen the average value was 65–9% and that for dietary phosphorus 59·6%.The percentage of the daily ration of nitrogen excreted in soluble form was 266% and that of phosphorus 41–2%, these values being significantly higher than those found using unfed animals. Nearly 90 % of the nitrogen excreted by the animals, whether feeding or unfed, was in the form of ammonia. The amounts of excreted ammonia and total soluble phosphorus increased significantly when the animals fed; but the small quantities of nitrogen released in forms other than ammonia did not change.

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.

Many of the calanoid copepods contain large amounts of neutral lipid that is predominantly wax esters (Lee, Hirota & Barnett, 1971; Lee & Hirota, 1973; Sargent & Garten, 1976). The role of these compounds in the life-history of copepods is particularly well documented for the large Northern Pacific calanoid Euchaeta japonica Marukawa. These animals have their highest levels of total lipid (50% of the dry weight) at stage V, up to 80% being wax esters (Lee, Nevenzel & Lewis, 1974). Wax ester levels are lower in adult females but are high in the eggs, the contents of which are subsequently used during the naupliar stages (Lee et al. 1974). Thus, wax esters accumulated during the later developmental stages provide a fuel for the developing eggs and embryos; from which it follows that the amounts of these lipids present in mature animals are likely to be critical in determining the brood size and survival of the ensuing generation. So far, however, the factors controlling lipid levels in copepods have been poorly understood.

No abstract

Studies were made relating to the problem of how Calanus feeds during winter in the Clyde sea-area. Different diets were assessed in terms of sustaining the levels of body nitrogen and phosphorus in Calanus helgolandicus (Claus) over a period of several days. The test diets, all equivalent to the same level of particulate nitrogen in sea water, were: (1) suspended matter collected from the Clyde sea-area in winter; (2) particulate material produced in a foam-tower by bubbling sea water enriched with soluble extracts of plant cells; (3) living nauplii of the barnacle Elminius modestus Darwin; (4) dead nauplii of this species.It was found that neither body nitrogen nor body phosphorus was sustained by diet 1; that body nitrogen, but not body phosphorus, was sustained by diet 2; that both were sustained by either of diets 3 and 4.With living Elminius nauplii as the food, each Calanus captured the equivalent of 25 % of its body nitrogen and 47·3 % of its body phosphorus daily: with dead nauplii as the food the corresponding values were 34·4 and 44·5%. These rations are much higher than those found in an earlier study of Calanus grazing on a spring diatom increase in the Clyde (Butler, Corner & Marshall, 1970) and demonstrate that animal diets are readily captured.In general, the results indicate that Calanus could survive the winter in the Clyde sea-area by feeding carnivorously.

A steroid that binds with mammalian oestradiol-17β antibody has been detected in Calanus helgolandicus Claus, collected from Plymouth Sound, and in Calanus finmarchicus Gunnerus captured off the coast of Norway. The specificity of the antibody, together with the chromatographic behaviour of the steroid on Sephadex LH-20, supports the view that the compound is the sex hormone oestradiol-17β (E2). The antibody has been used in measuring the amounts of E2 in the animals by radioimmunoassay, a technique not previously employed in studies with zooplankton and therefore described in detail.

No abstract

Many studies have been made on the metabolism of polycyclic aromatic hydrocarbons in mammals and it has been shown that these animals can convert compounds such as naphthalene into several metabolites (see, for example, Corner & Young, 1955). Baldwin (1957) has remarked on the ability of mammals to metabolize substances that they are unlikely to meet ‘except through the medium of the laboratory’. Marine animals, how-ever, can encounter these compounds in their normal environment, considerable quantities of polycyclic aromatic hydrocarbons being present in crude oil (Boylan & Tripp, 1971), in which form substantial amounts must be released into the sea annually.Little work has been done on the metabolism of naphthalene in marine animals, apart from studies confined – as far as we are aware – to experiments with three species of fish (Lee, Sauerheber & Dobbs, 1972) and the mussel Mytilus edulis L. (Lee, Sauerheber & Benson, 1972). Data obtained using fish were consistent with those of earlier studies with mammals in showing that the hydrocarbon is converted into hydroxylated derivatives: but no evidence of naphthalene metabolism was found in the experiments with Mytilus. Indeed, until the present work, the only species of invertebrate that has been found to metabolize the compound is the housefly Musca domestica L. (Terriere, Boose & Roubal, 1961).The present study, using Maia squinado (Herbst), has been carried out as part of a general investigation of the accumulation of polycyclic aromatic hydrocarbons in marine food chains and was designed to establish whether a marine crustacean possesses a means of metabolizing naphthalene by converting it into soluble excretion products.