Ch. Jeuniaux

Osmoregulation in molluscs of the intertidal zone.

Abstract o 1. Gastropods ( Littorina littorea, Purpura lapillus, Patella vulgata ) and bivales ( Mytilus edulis, Scrobicularia plana, Glycymeris glycymeris ) of the littoral area behave as poikilosmotic animals when acclimated gradually to diluted media. However, when transferred directly to the more diluted medium, these molluscs react by a “shell-closing” mechanism, leading to a transitory hyperosmotic state in the blood and the perivisceral fluids. 2. In the euryhaline molluscs studied, osmoregulation is achieved by isosmotic regulation of the intracellular medium. Free amino acids and taurine play a significant part as osmotic effectors in this regulation, except in the case of the Polyphacophora Acanthochitona discrepans . 3. The part played by the amino-acid pool as well as the nature of the prominent amino acids at work in the regulation of the intra-cellular osmolarity varies from species to species; no single, general pattern emerges from our study.

Biosynthesis of chitinases by mammals of the order Carnivora

Abstract The secretion of chitinases has been examined in six species of Mammals belonging to the order Carnivora. Chitinases were found only in the extracts of the gastric mucosa of two species not adapted to a strictly meat diet [Canidae: dog and fox] while those with exclusive carnivorous habits, [Mustelidae: stoat, ferret, marten; and Felidae: cat, seem not to secrete the enzyme. These observations confirm the existence of a correlation between the ability of a given species to synthetize chitinases in digestive svstem and the feeding habits of the species.

A comparative study of chitinase activity in digestive tract of Serranus cabrilla and Serranus scriba

Chitinolytic activity was searched for in oesophagus, stomach, intestine, pyloric caeca and liver of two sympatric closely related species of Serranidae (Teleostei, Perciformes): Serranus cabrilla (L.) and Serranus scriba (L.) living near the rocky shore of Calvi (Corsica, Mediterranean Sea). The chitinase activity was much higher in stomach than in other parts of the digestive tract and liver in both species. In extracts of gastric mucosa, the chitinase activity was more important in S. cabrilla than in S. scriba; an appointed situation was found in the extracts of intestine and pyloric caeca. These findings are discussed as aspects of the ability of these species to share very near ecological niches.

Les Acides Aminés Libres De L'Hémolymphe Des Isopodes Marins Sphaeroma hookeri, Sphaeroma serratum (Flabellifera) ET Idotea balthica (Valvifera)

AbstractThe total concentration of the free amino acids in the hemolymph is higher (about twice the amount in three species of marine Isopods (Sphaeroma hookeri, S. serratum and Idotea balthica) than in Decapods.In the three species so far studied, the proportions of glycine and taurine are always rather high. In the Sphaeromatidae, serine is the most concentrated amino acid while the proline concentration is comparatively low. The situation is reversed in Idotea balthica.In Crustaceans, the free amino acid composition of the hemolymph thus appears, both quantitatively and qualitatively, to be a biochemical character of marine Isopods when compared to Oniscoids Isopods and to Decapods.

Les Acides Aminés Libres Du Sérum Des Cimothoidae (Crustacés, Isopodes, Parasites De Poissons) Et De Quelques Téléostéens

The free amino-acid composition of the sera of 4 species of Isopods Cymothoidae (Meinertia oestroides, Meinertia parallela, Emetha audouini, Anilocra physodes) are very similar, and present the same characteristics, both quantitatively and qualitatively, as those of free marine Isopods of the family Sphaeromatidae and Idoteidae. Five amino acids are preponderant (serin, prolin, glycin, alanin and taurin). The total concentration is relatively high (154.6-356.4 mg/100 ml) with respect to Decapods. In the parasites studied so far, the free amino-acid pattern (except prolin) is rather like that of the Teleost Fishes, whether they are potential hosts of Cymothoidae or not. The free amino-acid concentration of the blood of the Fishes does not seem to be impaired by the Cymothoidae parasitism.

Les Acides Aminés Libres De L'Hémolymphe Au Cours De La Mue De Puberté Et De La Sénescence Chez Sphaeroma Serratum (Isopoda, Flabellifera) : Par

: In Sphaeroma serratum, the amino-acidemia is high (about 120 mg/100 ml) during the intermolt stages. The relative proportions of the different free amino acids show only slight differences in young males and senescent ones. At the time of the puberty molt, the total amino-acids concentration (including taurine) of the hemolymph increases sharply during premolt (up to 267 mg/100 ml), falls after ecdysis (down to 97 mg/100 ml and then rises up to the level of the intermolt stage. These variations are due not only to concentration or dilution of the whole hemolymph constituents, but also to specific modifications of the concentration of some of the free amino-acids with respect to the others. These variations of the amino-acidemia, mainly those of serine, proline, glycine, alanine and of the amine taurine, could play a definite role in increasing the osmotic pressure of the hemolymph during premolt, as a preparation to ecdysis.