Two new species of South American freshwater crayfish genus Parastacus Huxley, 1879 (Crustacea: Decapoda: Parastacidae).

Two new species of Parastacus Huxley, 1879 are described from material collected in the state of Rio Grande do Sul, southern Brazil: Parastacus fluviatilis sp. nov. from highland streams and Parastacus caeruleodactylus sp. nov. from wetlands. Parastacus fluviatilis sp. nov. is distinguished mainly by large chelipeds with dense setae cover on the cutting edge of fingers, telson subtriangular with two lateral blunt spines and strongly concave ventral surface of lateral process of thoracic sternites 6 and 7. Parastacus caeruleodactylus sp. nov. is distinguished mainly by blue cheliped fingers and a large gap between them, reduced abdomen, dorsal and ventral margins of dactylus, propodus and carpus of second pair of pereiopods with tufts of long setae and mid-dorsal carina of exopod of uropods unarmed. According to IUCN Red List criteria both species are considered endangered. Habitat characterization and a method for defining the shape of second abdominal pleura are also provided.

Metabolic responses in two species of crayfish (Parastacus defossus and Parastacus brasiliensis) to post-hypoxia recovery.

The period of post-hypoxia recovery is essential for the rapid replenishment of energy reserves and for the removal of metabolic end products formed during hypoxia. Periods of post-hypoxia recovery were analyzed in two crayfish species, where Parastacus defossus is a fossorial species, and Parastacus brasiliensis lives in lotic environments with higher oxygen levels. After 4 h of hypoxia (2 mg O(2)/L), groups of animals were placed in tanks with oxygenated water and were then removed at intervals of 1, 3, 6, and 9 h. Hemolymph and tissues (hepatopancreas, muscle, and anterior and posterior gills) were extracted for the determination of glucose, lactate, free glucose, glycogen, total proteins, total lipids, arginine phosphate, and arginine. As expected, lactate levels were restored more rapidly in P. defossus than in P. brasiliensis. P. defossus restored its glycogen reserves of the hepatopancreas and muscle tissue. Free glucose was quickly restored in all tissues of both species. In relation to arginine phosphate reserves, P. defossus showed a greater ability to restore this metabolite in the hepatopancreas. Both species recovered their arginine phosphate reserves, but they also used this metabolite in longer periods of recovery. Mainly in P. brasiliensis the reserves of total lipids seem to be an important source of energy during the recovery period. The animals developed various metabolic strategies to post-hypoxia recovery, mainly P. defossus which restored its reserves more completely and more rapidly than did P. brasiliensis.

Metabolic responses of Parastacus defossus and Parastacus brasiliensis (Crustacea, Decapoda, Parastacidae) to hypoxia.

The metabolic responses of two crayfish species living in different habitats, Parastacusdefossus and Parastacus brasiliensis, were analyzed after different periods of hypoxia (2.0mg O(2)/L of oxygen). In the laboratory, groups of animals were subjected to hypoxia for 1, 2, 4, and 8h. The hemolymph, hepatopancreas, muscle, and anterior and posterior gills were removed for determination of glucose, free glucose, glycogen, lactate, total proteins, total lipids, total cholesterol, arginine, and arginine phosphate. In both species, glucose and lactate increased significantly after 4h of hypoxia, but decreased after 8h (p>0.05) from the beginning of the experiment. Reductions of glycogen, lipids, and cholesterol were recorded in hepatopancreas and muscle tissue, especially of P. defossus, after 4h of hypoxia. Free glucose levels decreased in all tissues of P. brasiliensis, mainly in the hepatopancreas and muscle (p<0.05), while P. defossus showed smaller reductions of these reserves. All reserves in the anterior and posterior gills, with exception of the glycogen reserves, behaved similarly in both species. Both crayfishes stored and used arginine phosphate, mainly P. defossus, which also showed higher concentrations of all metabolites than did P. brasiliensis. Both species showed metabolic adaptations to hypoxia, but, as expected, P. defossus appeared to be better adapted.