Multiple paternity in the thalassinidean ghost shrimp, Callichirus islagrande (Crustacea: Decapoda: Callianassidae)

Adult ghost shrimp, Callichirus islagrande (Schmitt, 1935), are obligate inhabitants of burrow systems that they excavate deeply into beachfront sediments in the northern Gulf of Mexico. Mating presumably occurs in these burrows but has never been directly observed in C. islagrande or any other thalassinidean. A variety of possible mating systems is suggested by those of other decapods, among which are examples of both internal and external sperm deposition, sperm competition among males, and male adaptations for paternity assurance. We used genetic markers to determine if clutches brooded by individual female ghost shrimp had been fertilized by multiple males. The two microsatellite loci we employed were sufficiently polymorphic to detect 95% of the occurrences of fertilization by two males. Among 40 ovigerous females collected from the Louisiana Isles Dernieres barrier island, eight (20%) carried egg masses for which more than two paternal alleles were detected, indicating fertilization by multiple males. In two cases of multiple paternity, alleles from one of the males were detected in only a portion of an egg mass. These observations suggest several, possibly novel characteristics of the mating system that can be further investigated. © Springer-Verlag 2004.