Freshwater Crayfish Astacus Leptodactylus Research Articles

Superimposed Morphofunctional Study of Ion Regulation and Respiration in Single Gill Filaments of the Crayfish Astacus Leptodactylus

Using an in vitro perfusion method, a morphofunctional study was made of single filaments isolated from the podobranch of the fresh-water crayfish Astacus leptodactylus. Each filament was fixed for transmission electron microscopy directly after an electrophysiological study. This procedure allowed us to distinguish 2 filament populations on the basis of the electrical potential differences and the superimposed ultrastructural analysis. When both sides of the preparation were perfused with Van Harreveld saline, the potential difference was either zero for a first population of filaments or different from zero for a second one. The filaments of the first population were selectively sensitive to [Ca2+] changes but insensitive to [Na+] and [Cl -] changes in the external perfusion medium. Their epithelia were of the respiratory type, i.e., they were thin and poor in mitochondria. The filaments of the second population were sensitive to [Ca2+] and [Na+] changes. Their epithelia were of the ion-transporting type, i.e., they were thick, rich in mitochondria, and showed a developed basolateral membrane system.

Saprolegnia parasitica and its virulence on three different species of freshwater crayfish

Saprolegnia parasitica isolated from freshwater crayfish Astacus leptodactylus was investigated for its ability to infect and kill three different species of crayfish, Astacus astacus, Pacifastacus leniusculus and Procambarus clarkii. Healthy (non-injured) crayfish challenged with zoospores of S. parasitica became infected and ca. 20% died as a result of such infection. If the epicuticle of the crayfish was abrased gently before challenge with zoospores, mortality increased significantly, ca. 3 times. There were no significant differences in susceptibility between the three species of crayfish tested against S. parasitica.

The quaternary structure of four crustacean two-hexameric hemocyanins: immunocorrelation, stoichiometry, reassembly and topology of individual subunits

Two-hexameric (2×6) hemocyanins from the brachyuran crabsCancer pagurus andCallinectes sapidus, the freshwater crayfishAstacus leptodactylus and the lobsterHomarus americanus were isolated and dissociated into native subunits.

Effects of simultaneous changes of water temperature and oxygenation on the acid-base balance of the shore crab, Carcinus maenas

1. 1. Shore crabs Carcinus maenas were exposed to constant normoxic P O 2 (isobaric normoxia) or constant normoxic C O 2 (isoconcentration normoxia), at ambient seawater temperature of 7, 16 and 25°C, and constant P CO 2 , 0.82 torr. The acid-base balance (ABB) of prebranchial hemolymph was assessed by measuring pH and P CO 2 2. 2. The pH v- temperature relationship was the same in isobaric and isoconcentration normoxia, but the temperature-dependent variations of P v CO 2 were more marked in the second condition. This implies that the hemolymph carbonate concentration variations paralleled the P v CO 2 changes. 3. 3. By contrast, in the freshwater decapod crayfish Astacus leptodactylus, temperature-dependent changes of P v CO 2 , and carbonate concentration are different in isobaric and isoconcentration normoxia. 4. 4. In studies of respiration and ABB of water breathers, an essential prerequisite is an excellent regulation of ambient P O 2 , p co 2 ionic composition and temperature, because, as these experiments illustrate, the changes of ABB with ambient temperature variation are influenced by the effect of temperature on the ambient O 2 concentration, which itself also contributes to the observed respiratory and ABB responses.