Embryonic development and cardiac morphology of the grass shrimp, Palaemonetes pugio Holthuis, 1949 (Decapoda, Caridea, Palaemonidae): Embryonic staging

Decapod crustaceans are known for their variation in developmental patterns and their successful adaptation to diverse environmental conditions. The grass shrimp, Palaemonetes pugio Holthuis, 1949, inhabits the brackish waters off the Atlantic and Gulf coasts of North America and is a critically important component of the food chain in these ecosystems. A clear description and understanding of early embryonic developmental processes is necessary in order for this species to be used for future physiological, ecological, developmental and toxicological investigations. Here, we establish a uniform staging scheme for the embryonic period of development in grass shrimp using an 8-stage sequence. Under constant conditions (20 C, 32 ppt sea water), mean clutch size was 190 (±5) embryos per female and mean time for embryonic development (fertilization to eclosion) was 13 days. Morphological changes and staging were documented using photomicroscopy (still and video). Also described are cardiac morphological changes associated with embryonic development. The morphometrics of both embryonic development and cardiac ontogeny are provided. The morphological features described for P. pugio throughout embryonic development and the standardized embryonic staging scheme can be used to compare developmental patterns and timing when investigating questions related to an array of biological disciplines making this species a stronger model system.