Larval Development in Two Populations of the Ghost Shrimp Callichirus major (Decapoda: Thalassinidea) under Laboratory Conditions

ABSTRACT Zoeal and first postlarval stages of the Gulf of Mexico and Florida Atlantic populations of the ghost shrimp Callichirus major were obtained from laboratory cultures. Forty to sixty larvae from each parental female (8 from the Gulf population, and 4 from the Florida Atlantic population) were reared individually to obtain stage-duration data, while morphological studies were based on animals from mass cultures. Durations of larval stages were similar in larvae from different females and different populations. The Florida Atlantic population of C. major passed through 4 or 5 zoeal stages before molting to the decapodid stage. In contrast, the Gulf population almost always passed through 4 zoeal stages, and rarely had 3 or 5 zoeal stages. In both populations, duration for each of the first 3 zoeal stages was about 2 days. Duration of the fourth zoeal stage was, as in the decapodid stage, typically 3-4 days. When present, the fifth zoeal stage was usually 3-4 days in duration. Larvae from these populations were morphologically similar, with the persistent exception of the outermost spines on the posterior margin of the telson and the dorsal spine on abdominal segment 2, both of which were longer in the Gulf of Mexico population. Comparisons with other species in the genus Callichirus showed that the 2 populations of C. major were morphologically closer to the Brazilian Callichirus sp. (formerly referred to as C. major) than to C. islagrande and C. garthi.