Hemolymph metabolic variables and immune response in Litopenaeus setiferusadult males: the effect of acclimation

Massive nauplii production in Litopenaeus setiferus by means of natural mat ings has not been reported. The main reason is the low spermatophore attach ment rate that has been associated with male sterilization because of male reproductive tract degenerative and the male reproductive melanization synd romes (MRTDS and MRMS). This information indicated both syndromes could be related to the captivity and management stress that affects the immune syst em and the physiological state of shrimp. We used some blood metabolic vari ables, sperm quality, and immune response as indicators of captivity stress in adult males of L. setiferus. A comparison between freshly captured shri mp with shrimp maintained in the laboratory for 7 days at two temperatures were examined. Glucose and calcium were not different between fresh and acc limated shrimp at either temperature (P > 0.05). A reduction in triacylglyc erol, proteins, and cholesterol was observed in acclimated shrimp in compar ison with base line shrimp (P < 0.05). Lactate was reduced only in shrimp a cclimated at the lower temperature. Sperm quality was not significantly dif ferent between base line samples and acclimated shrimp. The immune system w as altered in acclimated shrimp at both temperatures. A reduction in total haemocytes, granular cells, and semigranullar cells was measured in acclima ted shrimp in comparison with base-line shrimp. In contrast, a higher pheno loxidase activity (proPO) was observed in acclimated shrimp, indicating tha t regulatory mechanisms of immune system of those shrimp were altered by ca ptivity conditions. The blood metabolic variables indicated that captive sh rimp were affected nutritionally more than physiologically. The immune resp onse showed the nutritional effect or another management factor reduced the cellular defenses and altered the molecular mechanisms associated with mel anin production. This could be related to the melanization syndrome observe d in previous studies. A new sequence to explain the appearance of the male reproductive shrimp syndromes of L. setiferus was proposed. (C) 2001 Elsev ier Science B.V. All rights reserved.