DETECTION OF CROSS-MATING BETWEEN TWO GENERATIONS OF THE CUTTLEFIH SEPIA OFFICINALIS BY SPERM RESERVOIR ANALYSIS

• Published in: Journal of molluscan studies 1998-02, Vol.64 (1), p.1-9
• Main Authors: GAUVRIT, E., DU SEL, G. PINCZON, BLANC, A., DAGUZAN, J.
• Format: Article
• Language: English
• ISSN: 0260-1230; 1464-3766
• DOI: 10.1093/mollus/64.1.1

This study concerns the reproductive cycle of Sepia officinalis living in southern Brittany and about mating between the two-year classes of breeders living there. The reproductive cycle is partly similar to that proposed by Mesnil (1977). The less important Sepia ofpicinalis group, which realised its cycle in one year, come, in all likelihood, from the early broods of the large group II breeder (GIIB) females. The group I breeder (GIB) females, which arrive later in the breeding area, would generate the long life cycle individuals. But, considering that GIB females are in minority and less fecund than larger GIIB females, it is not possible that they generate, on their own, all the long life cycle recruits. Obviously, part of GIIB offspring reproduce also during the second year. The year class of some males can be determined using some of the sperm reservoir (SR) found in the buccal pouch of the wild females. We estimate that under a size of 2.6 mm, the SR found in the buccal pouch of a female, would be deposited by GIB male and above 4.7 mm it would be deposited by GIIB. In this way, cross-mating between GIB males and GIIB females has been detected during the breeding season. The opposite situation (i.e. GIIB males with GIB females) is rather rare. In conclusion, the two year classes of breeding cuttlefish living in southern Brittany are not repro-ductively separated. There is gene flow between GIB and GIIB, due to mating between GIB males and GIIB females and also between GIB offspring and part of GIIB offspring going through a long life cycle.