EMBRYONIC AND LARVAL DEVELOPMENT OF THE GRASS GOBY ZOSTERISESSOR OPHIOCEPHALUS (TELEOSTEI, GOBIIDAE)

Zosterisessor ophiocephalus is a large, nest guarding goby which breed s within horizontal burrows excavated by males in the muddy bottom of the coastal shallow, brackish waters of the Italian northern Adriatic. Females spawn their eggs attaching them to the downhanging Zostera sp . roots. The present study reports the first successful attempt of rea ring this species under laboratory conditions from fertilized eggs to bottom dwelling juveniles. We describe embryonic and larval developmen t in order to identify age stages and diagnostic features to be compar ed with other Mediterranean goby species. Larval behaviour is also obs erved. Embryonic development is completed within 8 d at 18 degrees C. Ar hatching, the yolk-sac larva is positive phototactic, has an open m outh and visible swimbladder. The first exogenous feeding on rotifers occurs at day 2 post-hatching, while yolk sac absorption and the negat ive phototaxis are ar day 4. Defined patterns of melanophore distribut ion characterize and differentiate the yolk sac stage from equivalent ones reported for other Mediterranean species. Larvae metamorphose int o juveniles at day 13 when all the fins appear. They feed on Artemia a nd show an increased growth rate. At day 26, the juvenile bodies becom e compressed dorso-ventrally. The juveniles shift to benthic habits an d can be fed on artificial feed pellets. At day 82, the final body sha pe and colour patterns are acquired and territorial behaviour is displ ayed.