Description of the embryonic development of Pachycheles chubutensis (Anomura, Porcellanidae).

GONZÁLEZ PISANI XIMENA; PASTOR-DE-WARD CATALINA T.; DUPRÉ ENRIQUE

Newcastle upon Tyne

Congreso; 10th International Congress of Reproduction in Marine Invertebrates; 2004

P. chubutensis inhabits the lower eulittoral and the sub littoral rocky bottom from Cabo Polonio (Uruguay; 34ºS) to Rawson (Chubut, Argentina; 44ºS). To establish the structural patterns and the sequence of the embryonic development, optical and scanning electron microscopy (SEM) were used. The development sequence could be divided in five stages, based on the yolk volume, the presence of the germinal appendages, chromatophores and eyes pigmentation. Periodic samples were taken during the reproductive season of the species (September to March).  Ovigerous females with their respective males were moved from rock caves to the laboratory. They were kept in similar condition to nature, one couple per containers with small stones and bivalve shells that they used as caves, and sea water (34‰) at 20 ± 1ºC, changing it once a week. The embryos were collected from the females daily. The external embryonic membrane cover was extracted for a better observation with a differential interference contrast (DIC) microscope. and SEM. The embryonic development last 21 days, from the first stage to hatching of the zoea 1. Five stages were differentiated.  Stage 1: no structures are sighted; the embryos develop to morula and blastula; blastomeres can be observed on the surface. Stage 2: the first buds of appendages were observed. Stage 3: the ocular pigmentation appear in the ocular globe; Stage 4: the chromatophores appear in the abdominal zone; Stage 5: the ocular pigmentation cover entirely the ocular globe. At the end of this stage, the hatching of the pre-zoea takes place and 5 to 10 minutes after, the rostral and caudal spines stretches and the zoea I appear.