Assimilation efficiency of the antarctic marine isopod Glyptonotus antarcticus

When fed shrimp every 2 days, the isopod Glyptonotus antarcticus Eights assimilated over 90% of the ingested food. Errors in this estimate due to loss of food material during maceration by G. antarcticus were investigated and allowed for. These results are discussed in relation to data for other isopods and marine invertebrates.     

Effect of carbon dioxide concentration on calcification in the red coralline alga Bossiella orbigniana

The relationship between various experimental concentrations of CO₂ and calcification in Bossiella orbigniana (Decaisne) was studied by measuring Ca-45 incorporation into the crystalline matrix. Air containing CO₂ at partial pressures (P_{CO 2}) of 0.04 to 5.5% was bubbled through synthetic seawater in incubation vessels. The resultant pH values in the presence of plants ranged from 6.5 to 8.7. The maximum calcification rate appears to lie between 0.11 and 1.05% P_{CO 2}. The data suggest that calcification is controlled by a biological process that may be sensitive to pH and/or to the relative bicarbonate concentration. The data also suggest that a severalfold increase in CO₂ over the present atmospheric level might lead to increased calcification in this marine alga.     

Fluxes of dissolved and particulate calcium in selected tissues of Crassostrea virginica

Rates of calcium incorporation by selected tissues of Crassostrea virginica increased in a step-wise fashion from lowest values among organisms exposed to ambient total calcium concentrations of 45 mg l^-1, intermediate values among oysters exposed to 135, 225, and 315 mg l^-1, to highest rates for oysters exposed to 360 mg l^-1. Although excised visceral mass tissue had highest rates of calcium incorporation relative to mantle, muscle, and both organic and inorganic portions of the shell, mantle tissue appeared to have the most dynamic response to changes in ambient calcium concentrations. Rates of dissolved calcium incorporation from ambient water were approximately two to three orders of magnitude higher than comparable rates from ingested algal food. Behavioral response to concentrations of selected inoic, species in the ambient environment may have been responsible for observed differences in rates of calcium incorporation.     

Biosynthesis of trimethylamine oxide in calanoid copepods. seasonal changes in trimethylamine monooxygenase activity

Live copepods, Calanus finmarchicus (Gunnerus) and C. hyperboreus (Krøyer), exposed to dissolved ¹⁴C-labeled trimethylamine (TMA) in seawater, oxidized TMA to trimethylamine oxide (TMAO), which accumulated in the organisms. The amount of TMAO synthesized was dependent on the time of exposure to TMA and the concentration of TMA in the seawater. It was inferred that copepods can produce TMAO by oxidation of TMA found in their plant food. Choline and methionine did not appear to be of importance as precursors of TMAO. There were large seasonal changes in TMA monooxygenase activity of both copepods. The activity was high in spring, and decreased through summer and autumn to a winter low in October to March. The changes in TMAO content of C. finmarchicus were, in comparison, small (this aspect was not tested for C. hyperboreus).     

Method for indirectly defining optimum temperatures of inhabitancy for marine cold-blooded animals

Investigations on the influence of pressure on the activity of alkaline phosphatase of some marine invertebrates from the Baltic Sea were carried out at temperatures between 5° and 55°C. The results obtained indicate that the influence of pressure on alkaline phosphatase activity is modified by temperature. At low temperatures, pressure has a decreasing effect on enzyme activity, while it has an increasing effect at higher temperatures. The gill homogenates of the relatively pressure-resistent bivalves Cyprina islandica and Mytilus edulis show a lower decrease of activity under pressure at low temperatures than the gill-homogenate of Carcinus maenas and a purified enzyme preparation of a homoiothermal animal.     

Age and growth in Nephrops norvegicus (Decapoda: Nephropidae)

The growth of the lobster Nephrops norvegicus (L.) in laboratory tanks was studied. The moult increments of males and females were not significantly different. The growth per moult was of the progressive geometric type throughout the life of the lobster, including the larval instars. Moulting in both the laboratory and the natural population occurred throughout the year in males, but there was a peak of moulting activity in females from June to August. There was no indication of a terminal anecdysis. Size-frequency histograms from monthly samples taken 10 to 20 miles south-west of the Isle of Man over a period of 21/2 years provided data on the growth of the year classes. It is possible to recognise the year classes in females at least, until the lobsters are 3 to 4 years old. Instar determination based on the numbers of aesthetasc-bearing segments of the antennule and on the numbers of lamellae in the endocuticle was unsuccessful. Estimates of the numbers of moults occurring in each year, and the expected mean sizes of the year classes are given.     

The chemical basis of food detection in the lobster Homarus gammarus

A synthetic mixture of chemicals, based on the composition of an extract of squid muscle, has been developed, which is highly attractive for the lobster Homarus gammarus (L.). None of the components of this mixture was as attractive as the complete mixture, and substitution of D-amino acids for the natural L-forms also greatly reduced the attractiveness. This would indicate that several different types of chemosensory cell must be simultaneously stimulated to initiate exploratory feeding behaviour, and that a high degree of stereospecificity is involved. The results are discussed in the context of the wide range of food materials known to attract lobsters.     

Cytological sexing of cetacea

A biopsy dart, that can be shot from a gun or crossbow, was developed to obtain skin of whales at sea. Determination of sex was found possible by staining and locating sex chromatin bodies in the nuclei of female skin cells. This procedure will be useful in many types of field studies on whales.     

Surface area in ecological analysis: Quantification of benthic coral-reef algae

The surface area of organisms and substrata is shown to be a significant ecological parameter because of its functional importance in the system. Quantification of surface area can be of particular value in morphologically complex environments such as coral reefs. The amount of surface in a reef habitat can be estimated by direct measurements and theoretical approximations, using a surface index (SI) for the amount of surface increase over that of a similarly bounded plane. SI values for a section of the British Honduran barrier reef ranged up to 15 in the reef-crest area at scales significant to macro-organisms. By combining substrate-area measurements with estimates of percent coverage of the major benthic algal components, a reef transect with a horizontal area of 300 m² was shown to have over 300 m² covered by benthic macroalgae. The potential for the further development of surface estimation techniques is discussed.