Sperm economy and limitation in spiny lobsters

Sperm limitation, when female fertilisation success is constrained by the s upply of sperm, is generally perceived to be an uncommon feature of reprodu ction in species which directly transfer gametes during copulation, Male si ze, previous copulations, and the balance of expected reproductive return a nd future mating opportunity may, how ever, limit the amount of sperm males transfer to females. We used laboratory experiments where mate size could be manipulated and its consequences on spermatophore sine and clutch size d etermined to show that in two genera of spiny lobsters (Crustacea: Palinuri dae) male reproductive output limits the size of clutches brooded by female s. In Panulirus argus from the Florida Keys. we show that while male size a ffects spermatophore area, males also vary the amount of ejaculate positive ly with female size. Furthermore, the area of the spermatophore has a great er influence than female size on subsequent clutch weight. In Jasus edwards ii from Neu Zealand, female size, male size and mate order all affect clutc h weight. In both species, clutches fertilised by small males in the labora tory are significantly smaller than clutches fertilised by large males. The se results suggest that to ensure they receive sufficient sperm, females sh ould either mate several times prior to oviposition mate as early as possib le in the reproductive season, or choose large, preferably unmated males as partners and thus compete with other females for preferred males. Sperm-li mited female fecundity has the potential to limit the egg production of fis hed populations where large males are typically rare.