Effect of size on sperm production in the freshwater crayfish “redclaw” Cherax quadricarinatus (Parastacidae).

BUGNOT, A.B1., LÓPEZ GRECO, L.S.1,2

Coquimbo, Chile

Congreso; Mid-Year Meeting of the Crustacean Society; 2007

The Crustacean Society

EFFECT OF SIZE ON SPERM PRODUCTION IN THE FRESHWATER CRAYFISH “REDCLAW” CHERAX QUADRICARINATUS (PARASTACIDAE).   Bugnot, A.B1., López Greco, L.S.1,2   1Dept. of Biodiversity and Experimental Biology, FCEN, University of Buenos Aires, Cdad. Univ. C1428EHA, Buenos Aires, Argentina. 2CONICET. laura@bg.fcen.uba.ar   Sperm production is one of the aspects scarcely known in the majority of Decapoda although it has been shown in the few studied species that this parameter could affect the reproductive out of females by “sperm limitation”. Due to the absence of any knowledge about this aspect in C. quadricarinatus this study was aimed at studying the effect of male size on sperm production. Males of  8.55-270.64g (n=84) were purchased from a local farm, and once in the laboratory they were measured (maximum carapace length, maximum post-orbital length) and their reproductive systems were dissected. For each distal vas deferens one piece of 1cm in length (equivalent to the length of the spermatophore transferred to the female during mating) was disaggregated in saline solution and spermatozoa were counted in a Neubauer camera. The remaining tissue was processed for histological analysis. For determining spermatozoa viability vital dye exclusion was used. The sperm production of C. quadricarinatus is related to size, being within the range 107-109 spermatozoa/ml. The sperm viability does not depend on size being greater than 98.5% in all cases. According to these results the sperm production would not be a limiting factor during mating since egg production is 300-1000 eggs/spawn. Although the presence of spermatozoa indicates sexual maturity, the macroscopic and microscopic analysis of the vas deferens demonstrate that males smaller than 40 g produce a more liquid and less sticky spermatophore than greater males. Being the adhesiveness of the spermatophore to the female sternum the main feature to assure fertilization and avoid spermatophore displacement, these results demonstrate that the functional maturity of males is acquired at nearly 40 g, although sperm production starts earlier. Financial support: ANPCYT (PICT 2004-953), UBACYT 2004-2007 (project X143), Antorchas Foundation (project 4248-138), and CONICET (1106/2004). POSTER PRESENTATION