Physiological and immunological assessment of two types of crayfish in aquaculture

Abstract

Due to the need to develop domestic aquaculture of decapod crustaceans, one of the urgent issues is monitoring the health of these aquatic organisms through the most informative bioindicators — hemolymph indicators. The aim of the study was a comparative physiological and immunological assessment of long-toed (Pontastacus leptodactylus) and Australian red-clawed (Cherax quadricarinatus) river crayfish contained in a closed water use facility. The main hydrochemical parameters generally met the existing requirements. The physiological and immunological condition of crayfish was assessed by hematological and cytochemical analyses. Hemolymph samples were taken in vivo by puncture of the ventral sinus. The total number of hemocytes was determined in the native hemolymph in the Goryaev chamber. The number of cells in five large squares was counted. Lysosomal cationic protein was detected in hemocytes by the cytochemical reaction with bromophenol blue, which we previously modified. Red-clawed crayfish have a significantly 45% higher total number of hemocytes, which indicates its greater immune resistance to pathogens compared with long-toed crayfish. The most significant species differences in the hemogram were noted for agranulocytes (HC I) — in long-fingered crayfish, the indicator is higher with a high confidence coefficient (t). With a high degree of confidence, it is possible to judge a higher proportion of semigranulocytes (HC II) in red-lobed crayfish. The proportion of HC IV of long-fingered crayfish is greater than that of red-clawed crayfish. In red-clawed crayfish, the average cytochemical coefficient of ACC is lower than in long-fingered crayfish. This also confirms its high immune resistance due to the consumption of highly cytotoxic cationic protein in the process of immune protection.