Gametogenic cycle of the smooth clam Callista chione on the south-western coast of Portugal

Abstract

The gametogenic cycle of the smooth clam Callista chione off the Arrábida region was studied throughout a 17-month period (from January 2004 to May 2005) using standard histological techniques, mean oocyte diameters and a condition index. This species showed a synchronism between sexes both in terms of gametogenic development and spawning. The results indicated that sex-ratio was not significantly different from parity. In January 2004, the gametogenic cycle had already begun and ended in late October 2004. Three spawning peaks were detected: January–March, April–May and August–October. No resting period was observed and a new gametogenic cycle began in early November, immediately after the spawning period. The analysis of the oocyte diameter enabled predicting the main spawning periods, which appear to be largely governed by seawater temperature. The condition index evolved according to the reproductive cycle of the species, with the highest values being observed prior to the main spawning periods. The size at first maturity estimated for C. chione was 50.81 mm.

Age determination and growth rate of a Callista chione population from the southwestern coast of Portugal

“…Using these VBG equations and the size at first maturation previously estimated for this Callista chione population (50.81 mm SL; Moura et al 2008), we estimated the respective age at first maturity. According to these calculations, the smooth clam off Arrábida reaches sexual maturation at between 4.25 (surface growth rings) and 4.44 yr of age (internal growth bands).…”

Age, growth, and population structure of the smooth clam Callista chione in the eastern Adriatic Sea

“…in July, January and March, indicating several reproductive events within a year. In the coastal waters of southwest Portugal, C. chione showed three spawning peaks between January and October (Moura et al 2008). The occurrence of several reproductive peaks throughout the breeding season is likely to be an adaptation that favors, by risk spreading, successful recruitment rather than relying on the survival of one large cohort per year.…”

“…Moura et al (2008) noted that changes in body condition index in C. chione followed the gametogenic cycle; flesh weight increased prior to spawning and decreased during spawning. Previous studies of gonad development in C. chione have indicated that this bivalve is capable of year-round reproduction, having a prolonged reproductive cycle with simultaneous presence of gametes in various stages of maturation (Metaxatos 2004;Moura et al 2008). In our study, three peaks in condition index were noted, i.e.…”

“…Callista chione does not begin gametogenesis until it attains a length of at least 30 mm, and the size at first maturity for this species is *51 mm (Moura et al 2008). Fecundity in bivalves is size-related and in the largest animals, most production ([90%) is channeled into gamete synthesis (Gosling 2003).…”

“…Previous studies that have been conducted on C. chione include an analysis of its reproductive cycle in the coastal waters of Màlaga, southern Spain (Tirado et al 2002) and in southwestern Portugal (Moura et al 2008), and its population dynamics in the eastern Mediterranean waters off Greece (Metaxatos 2004). Furthermore, its age and shell growth rate has been determined along latitudinal gradients (Hall et al 1974) in the English Channel (Forster 1981), in the Bay of Trieste, Italy (Keller et al 2002) and from shallow depths (\5 m), in the Thracian Sea, northeastern Mediterranean (Leontarakis and Richardson 2005) and from the southwestern coast of Portugal (Moura et al 2009).…”