Spawn and early larval development of Spanish dancer nudibranch Hexabranchus sanguineus (Rüppell and Leuckart, 1828) (Gastropoda: Nudibranchia)

Abstract

Hexabranchus sanguineus is best known as the Spanish dancer was found predominantly on the shallow fringing reef platforms all around Hurghada. Egg ribbons, fecundity and growth of larval stages of four specimens of H. sanguineus were studied in the laboratory. It lays a rose shape egg ribbons, attached to suitable hard substrate, varied in lengths and breadths. The egg ribbons lengths ranged from 19.68-20.28 mm. Eggs are clustered together in clear and transparent spawn jelly capsules. Eggs are spherical in shape with 100-113 microns in diameter. The number of eggs in the capsules was not the same in all ribbons, ranged between 8-34 eggs/capsule. The estimated total fecundity of H. sanguineus ranged from 1.5×106-3.6×106 eggs. The small, translucent, slow rotary movement trochophore larva was developed within capsules on the 6th day and reached 120-150 μm. The active mobile veliger larvae were released successively into the surrounding medium like red fumes with 150-190 μm from 8-9 days. The shell possesses only a single spire. It measures 170-200 μm in length and 130-150 μm in height.