Caractères et évolution des enzymes chitinolytiques chez les vertébrés infèrieurs

The activity of chitinases extracted from various organs of different fish, amphibians and reptiles was estimated as a function of pH by using “native” chitin as substrate. Three types of chitinase activity were recorded, suggesting the existence of three different chitinase types: Type 1: (optimum pH; 4.5, no activity at pH 1.0) was found in various organs, such as intestine, pyloric caeca, pancreas, liver, spleen, etc.); Type IIa: (optimum pH; 3.0, weak activity at pH 1.0) was obtained from the gastric mucosa of fish and one species of urodele; Type IIb: (optimum pH; 3.0, strong activity at pH 1.0) was found in the gastric mucosa of reptiles and batrachian anura. Chitinase activity appears to be adapted to the pH of the digestive fluids. A tentative scheme is presented of chitinase evolution among lower vertebrates.     

Les Invertébrés Planctoniques du Lac Volvi (Macédoine,Grèce). The Planktonic Invertebrates of Lake Volvi (Macedonia,Greece)

The planktonic invertebrates found in Lake Volvi are presented. There are 26 species of Rotifera, 1 Bivalve (larva), 13 Cladocera, 5 Copepoda, 1 Branchiura and 1 Diptera (larva). Many of these are new for the Greek fauna, though they are common in Europe. The discovery of some other species extends the knwown bounds of their geographical distribution in Greece. The lack of large-sized forms is considered to be due to strong predation by Alosa macedonica. (Pisces, Clupeidae). A comparison is given to the planktonic invertebrates of other Balkan lakes. There is a remarkable similarity with the fauna of Lake Doïrani.