Diet impact on the reproductive characters of male red claw Cherax quadricarintus during the juvenile-adult transition

Abstract

Male decapod reproduction involves gametogenesis, spermatozoa packaging in spermatophores, changes in cheliped´s growth, and specific behaviors such as courtship, male-male agoniztic interactions, and territory defense. These reproductive-related morpho-functional processes are supported by feed, one of the higher operative costs in aquaculture. This study aimed to evaluate the reproductive variables during the juvenile-mature transition of the male red claw Cherax quadricarinatus fed with two low-cost diets (T1 and T2). Pre-adult males (∼7 g) were individually distributed in plastic containers and fed a diet with fish silage (T1) (n = 9), a diet without fish silage (T2) (n = 8), and a commercial diet for ornamental fish used as a reference diet (T3) (n = 7). The proximal composition of T1, T2, and T3 was 34 %, 28 %, and 47 % for crude protein; 13 %, 9 %, and 6.5 for lipids; and 34 %, 47 %, and 28 % for carbohydrates, respectively. All males acquired sexual maturity with a body weight between 16 and 21 g. All groups showed similar chelae growth (based on the evaluation of the chelae height, and chelae thickness indexes) and red patch development. The gonadosomatic index was significantly lower in the T2 group with respect to T1. The lowest proportion of mature testicular lobes (filled with spermatids/spermatozoa) was detected in the T2 group (49 %), followed by T1 (59 %) group. There was also a lower protein content (∼ 27 %) in the vasa deferentia of the T2 group. However, all males showed a well-developed reproductive system and the histology of the testes and vasa deferentia showed no evidence of structural differences among groups. Under transmission electron microscopy analysis, both the primary and secondary layers of the spermatophore did not show qualitative differences among groups, including the spermatozoon morphology and acrosome size. This study highlights that males fed low-cost diets (0.56 and 0.65 U$S kg− 1, for T1 and T2 respectively), in particular T1, showed reproductive performances as good as the group fed on the reference diet. This is the first analysis of a pool of morpho-functional and biochemical reproductive variables in red claw males, to evaluate the effects of formulated diets on male sexual maturation.