Haemolymph metabolic variables and immune response in Litopenaeus setiferus adult males: the effect of an extreme temperature

Abstract

The stress of captivity could be the main reason for the loss of sperm quality of Litopenaeus setiferus (L) males in captivity. The aim of this study was focused on the physiological and immunological response of adult male shrimp exposed to a temperature extreme (33 degreesC in order to understand how the stress modulates the physiological, immunological and reproductive behavior of L. setiferus males. We used some blood metabolic variables, sperm quality and immune response as indicators of stress measured daily during the 10-day experiment. The high temperature provoked loss of osmotic capacity (OC), a reduction in blood metabolites at day 5, a reduction in hemocyte pro Phenoloxidase (proPO) activity and a dramatic reduction in sperm quality in comparison to that observed in freshly captured wild shrimp populations. The ratio between proPO and granular cells (small granular and large granular cells) (proPO/GC showed a cyclic behavior with lower peaks at days 3, 7 and 10 and high peaks at days 0, 5 - 6 and 8 - 9, evidencing migration and recovery of cells and proPO every 48 - 96 h, depending on the intensity of the stress. Such hemocyte migration was directed to the ampule and spermatophore where bacterial growth could be enhanced by abnormal and dead sperm cells. In such circumstances, a rapid mobilization of reserves could help to promote tissue regeneration in male testes and vas deferens. Such use of reserves could explain the reduction in blood metabolites observed at day 5 in present study. Although blood metabolites recovered after day 5, the loss of OC suggests that shrimp lose their osmotic homeostasis, possibly associated with the entrance of water due to inflammation of tissues provoked by melanization. (C) 2003 Elsevier Science B.V. All rights reserved.