Gabr et al Reproductive versus somatic growth during the life cycle of Sepia pharaonis 



809 



60 



50 



40 



30 



20 



N94 



r 12 



N94 



offshore after spawning either 

 to die or to return to spawn 

 again; such a migration is un- 

 hkely to be preceded by any deg- 

 radation of mantle muscle, 

 which is the major organ for lo- 

 comotion in cuttlefish. In nei- 

 ther mantle nor head was there 

 a significant variation in per- 

 centage of protein or water con- 

 tent with maturity stage. These 

 data indicate that female S. 

 pharaonis possibly do not use 

 mantle or head tissue to fuel 

 gonadal development, at least 

 during the beginning of the 

 spawning season. 



In sharp contrast, studies of 

 another cuttlefish. Sepia doll- 

 fusi (Gabr et al., in press), have 

 demonstrated that this species 

 seems to use mantle muscle as 

 an energy source during go- 

 nadal development. There thus 

 appears to be a continuum in 

 cuttlefish reproductive strategy. 

 At one end, spawning is associ- 

 ated with gonad maturation at 

 the expense of somatic tissue. 

 At the other end, growth of re- 

 productive organs takes place 

 through the use of energy and 

 nutrients derived from the diet, 

 not through mobilization of nu- 

 trients and energy from somatic 

 tissue. 



The results of this paper 

 agree with some studies on the 

 squid lUex argentinus (Hatfield 

 et al., 1992; Rodhouse and 

 Hatfield, 1992; Clarke et al., 



1994). Although mantle mass of female lUex 

 argentinus decreases in relation to ML with matu- 

 rity, this is not associated with degradation or 

 changes in the biochemical composition of mantle 

 muscle. Studies on Lo//^o /brfoesj (Collins etal., 1995), 

 L. gahi (Guerra and Castro, 1994) and Photololigo 

 sp. (Moltschaniwskyj, 1995) have also demonstrated 

 that maturation and growth occur simultaneously 

 during most of the life cycle and that the condition of 

 the squid remains high at maturation. 



The digestive gland showed no loss of mass during 

 maturation. Boucaud-Camou (1971) indicated that 

 the digestive gland of Sepia officinalis could act as a 

 lipid storage organ, and Blanchier and Boucaud- 



MI 

 HI 



i 5- 



i i 5 I 



M 



M 



N95 



VI 

 DGI 



M 



M 



N95 



M 



24 



1.6 



0.8 



0.0 



SCI 

 GSI 



N94 



M 



N95 



M 



Month 



Figure 4 



Male Sepia pharaonis mean (SD) dry weight indices of mantle (MI), head (HI), vis- 

 cera (VI), digestive gland (DGI), spermatophoric complex (SCI) and gonad masses 

 (GSI) for standard size (50-70 mm ML). 



Camou (1984) found that the variation in lipid lev- 

 els of the digestive gland seemed more related to diet 

 than to sex or maturity state of the gonads. There 

 was no significant variation in the digestive gland 

 weight with maturity state and season. Thus, the 

 digestive gland mass cannot be used as an indicator 

 of feeding activity in S. pharaonis as it can in some 

 squid (Abolmasova et al., 1990) because no increase 

 in DGI was found in the season of high feeding ac- 

 tivity. This agi-ees with Castro et al. ( 1991 ), who found 

 no significant variation in the digestive gland weight 

 with season in S. officinalis and S. elegans. 



In conclusion, this study shows that the pattern of 

 intermittent spawning suggested by our previous 



