Brossi-Garcia, A.L., S. G. Melo
Macrobrachium petronioi, a native species of freshwater shrimp, was captured along the coast of Rio Branco, Cananeia (S.P), Brazil. The eggs are green-black in early development and the average size was 1.21 mm by 0.98 mm. After hatching, the larvae were maintained individually in plastic containers with sand as a substrate, 100 ml of freshwater, and at an average temperature of 25 C. M. petronioi has no free-swimming larval phase, but newly hatched larvae do possess several zoea I characters; therefore, they are clearly more developed than the zoea I of other Macrobrachium species with prolonged larval development. The average duration of larval development in M. petronioi was 5.5 days. During early development, the larvae subsist on the stored yolk mass. After the third moult, the post-larvae accept food. The three zoeal stages prior to the post-larval stage, were described and characterized, with detailed morphological analyses. This species has a partially abbreviated type of development. Total independence of the brackish water environment, found in the larvae of some Macrobrachium species, may be related to their large yolk supply; which has probably resulted in the production of larger and consequently better developed larvae. This situation was observed for M. petronioi and suggests that the adaptation occurred by production of more advanced larval stages. This may explain the long period of incubation, which extends to about 50 days and also the lower production of eggs.
(Departamento de Zoologia, Instituto de Biociencias, Universidade Estadual Paulista -Campus de Rio Claro, S.Paulo, C.P. 199, Brazil)
*******