Embryonic stages of the freshwater prawn Macrobrachium olfersi (Decapoda, Palaemonidae)

Macrobrachium olfersi is a palaemonid prawn with a broad geographical distribution, from the East Coast of the United States to southern Brazil. This paper attempts to establish the embryonic stages for M. olfersi based on morphological features in living and fixed embryos. We adopted nonfixed percentages related to the morphological events to define ten embryonic stages: pre-cleavage, cleavage, gastrula, germinal disk, naupliar, caudal papilla, C-shape, eye-pigmentation, segmented-abdomen, and pre-hatching. We hope the description of these stages can be used as a tool for studies of the embryonic process in species of Macrobrachium, and also as a guide to judge the developmental stages of palaemonids in environmental and experimental studies.