Egg massi intracapsular and extracapsular larval development of Rapana thomasiana gross, 1861, from the Eastern Black Sea Region

Egg Mass, Intracapsular and Extracapsular Larval Development of Rapana thomasiana GROSS, 1861, from the Eastern Black Sea Region Spawning season, size at first sexual maturity, capsule production, egg yield and larval development of sea snail, Rapana thomasiana Gross 1861, have been studied using 27 mature pairs during 1996 spawning season- Spawning occured between late June (20°C) and early August (27°C) when average seawater temprature was around 25°C. Minimum shell length at first sexual maturity was about 40 mm. Total number of capsules produced by an average female ranged between 197 and 999 (575±40.1; n= 27). Each capsule contained between 105 and 1090 eggs with a mean of 5549 ±818. The mean number of eggs produced by each female during whole spawning season has been estimated as 318729 and egg size ranged between 182 um and 275 um as a parallel to the embrionic development. The mean length of the capsules were 15.44 mm. At least five different stages of intracapsular development were observed. In different developmental stages, colour of embryos vary from yellow to brown-black. Key words : Sea snail Rapana thomasiana, reproduction, larval development, capsule production. VI