Marine Crustacean Species Research Articles

Biosynthesis of sterols in the lobster, Panulirus japonica, the prawn, Penaeus japonicus, and the crab, Portunus trituberculatus

1.1. In the present study, the sterol-synthesizing abilities of the lobster, Panulirus japonica, the prawn, Penaeus japonicus, and the crab, Portunus trituberculatus, were investigated by using acetate-1-14C.2.2. It was found that the three species of marine crustaceans are capable of synthesizing fatty acids and some non-saponifiable materials. However, under the present experimental conditions, these animals did not incorporate acetate-1-14C into sterols.

PHOSPHORUS EXCRETION BY ZOOPLANKTON

The excretion of dissolved inorganic and organic phosphorus by several species of marine crustaceans and a planktonic rotifer was measured under laboratory conditions. The rate of excretion decreased as bacterial activity and duration of experiments increased and was directly related to temperature and salinity. Excretion rates were higher in early evening than at other times of day.The daily phosphorus requirements of the phytoplankton, calculated from 14C measured rates of production and an assumed C : P ratio of 40 : 1, were compared with phosphorus released by zooplankton. The rates of excretion and the abundance of zooplankton were used to calculate an average daily addition of inorganic phosphorus to the photic zone. In Bras d’Or Lake, zooplankton released twice the average daily phytoplankton phosphorus requirement; in Morrison’s Pond, only one‐fifth was supplied by animal excretion. Microzooplankton excretion (not considered in this study) may explain the discrepancy between phytoplankton requirements and regeneration rate in Morrison’s Pond. Phosphorus supplied from the hypolimnion by eddy diffusion in Bras d’Or Lake was one‐tenth that regenerated by the zooplankton.

Fatty Acid Composition of Some Marine Animals from Various Depths

The fatty acid composition of 20 species of marine animals, primarily fishes and crustaceans, was determined by gas–liquid chromatography. The species came from various depths down to 4400 m. The results showed that the medium-chain saturated and the long-chain polyunsaturated acids decreased with increasing depth, while oleic acid increased. It was thought that this indicated the presence of large amounts of wax esters. A benthic, mud-feeding holothurian Scoloplanes theeli was shown to have a fatty acid composition markedly different from that of pelagic species. This was attributed in part to the bacterial components of its diet.

THE OCCURRENCE OF THE HUMORAL CHROMATOPHORE ACTIVATOR AMONG MARINE CRUSTACEANS

The chromatophore-activating principle of the crustacean eye-stalk has been found in Palcwmonetes by Perkins (1928), in Crangon and several species of Leander by Koller. (1928), in Macrobrachium by Smith (1930), in Praunus by Koller and Meyer (1930), and in Callinectes by Perkins and Kropp (1932). Already indicated as present in several families of decapods, the hormone was looked for in as great a variety of crustaceans as could be obtained in the vicinity of the Mt. Desert Island Biological Laboratory, at Salisbury Cove, Maine. We had available seven different species of marine crustaceans belonging to as many different families. Six were decapods-Crago ( Crangon) boreas, Pandalus montagui, Homarus americanus, Pagurus longicarpus, Libinia emnarginata, and Cancer irroratus; one was a schizopod -Mysis stenolepis. The eyes were extracted in sea water as has been described previously. Unfortunately, the extracts could not in all cases be tested on the species from which they were derived. This was impracticable with Homarus, Libinia and Cancer because of the lack of external chromatophores that undergo readily observable changes. Pandalus and Pagurus did not remain alive long enough under laboratory conditions to permit adequate tests, and Mysis was too small for injection in addition to being very fragile and non-resistant. Therefore, Crago boreas was used as a test animal for all extracts. Measured amounts of the extract in question were injected into two sets of Crago which had previously been adapted to white and black backgrounds respectively. In all cases the chromatophores of Crago were examined microscopically before and after the eye extract was injected in order to determine the degree of contraction or expansion. Control animals, similarly adapted, received like amounts of sea water, and still others received the same amount of the donor's abdominal muscle similarly extracted in sea water. Following injections, the animals were returned to the background on which they had become adapted; i.e., white-