Embryonic and larval development of the grass goby Zosterisessor ophiocephalus (Teleostei, Gobiidae)

Abstract

Zosterisessor ophiocephalus is a large, nest guarding goby which breeds 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 downhang‐ing Zostera sp. roots. The present study reports the first successful attempt of rearing this species under laboratory conditions from fer tilized eggs to bottom dwelling juveniles. We describe embryonic and larval development in order to identify age stages and diagnostic features to be compared with other Mediterranean goby species. Lar val behaviour is also observed. Embryonic development is com pleted within 8 d at 18° C. At hatching, the yolk‐sac larva is positive phototactic, has an open mouth and visible swimbladder. The first exogenous feeding on rotifers occurs at day 2 post‐hatching, while yolk sac absorption and the negative phototaxis are at day 4. Defined patterns of melanophore distribution characterize and differentiate the yolk sac stage from equivalent ones reported for other Medi terranean species. Larvae metamorphose into juveniles at day 13 when all the fins appear. They feed on Artemia and show an in creased growth rate. At day 26, the juvenile bodies become com pressed dorso‐ventrally. The juveniles shift to benthic habits and can be fed on artificial feed pellets. At day 82, the final body shape and colour patterns are acquired and territorial behaviour is displayed.