SEPIABREED - Improving the reproduction of the European cuttlefish, Sepia officinallis (Linnaeus, 1758) in captivity: a multidisciplinary approach

Much cuttlefish research during the last few years has focused on its introduction as a new species for aquaculture. This is because the species displays biological and economical aspects with potential for industrial culture. Sykes et al. (2006a) reviewed this potential and identified reproduction as a technological bottleneck for the European cuttlefish, Sepia officinalis. This was mostly due to several biological aspects of the species, such as: semelparity; low fecundity and fertility in captive conditions; and suspicions of inbreeding (after egg non-viability after 6 consecutive generations - Sykes et al. 2006b). Control of reproductive function in captivity is essential for the sustainability of commercial aquaculture production. It relies on species specific biological and physiological knowledge and culture conditions, which will ultimately influence animal welfare (Conte 2004). Nonetheless, no previous studies on cuttlefish reproduction in captivity have used a multidisciplinary approach to solve these problems. With the present proposal we aim at an approach that will take zoo-technology, behavior, physiology, and population genetics, into account.

Regarding the effect of culture conditions, early experiments (Forsythe et al. 1991 and 1994; Correia et al. 2005) and recent data (Sykes et al. 2006a & 2006b, 2009 and unpublished results; Domingues & Márquez 2010) indicate that the type of tank, environmental and biological conditions may influence fecundity and fertility. On the other hand, the effects of optimal bottom area/tank volume, density, and natural male/female ratio; are still to be unveiled and these culture conditions will have an effect on cuttlefish physiology.

Knowledge regarding cuttlefish behaviour and chemical communication has been reported both in nature and captivity. In nature, cuttlefish only become social for reproduction, while in captivity they show complex intraspecific visual displays (Hanlon et al. 1999) and form short-term female-male pair associations (Boal, 1997). Males use visual displays to establish size-based dominance hierarchies, where large males mate more frequently (Adamo & Hanlon, 1996; Boal, 1997). During copulation, males display sperm removal behaviour (Hanlon et al. 1999). Despite the wealth of information regarding the role of vision in cuttlefish behaviour, little is known about the role(s) of olfaction. Apparently, olfaction is involved both in female mate-choice and social recognition (Boal & Golden, 1999; Boal, 2006). Recently, a peptide (ILME) was identified in cuttlefish, which is a chemical messenger released by the oocytes and eggs and which acts at both paracrine and pheromonal levels (Zatilny et al. 2000a) So, to what extent does all of this influence reproduction in captivity and how can we use it to manipulate cuttlefish reproduction? On the other hand, to what extent will culture conditions influence cuttlefish behavior and chemical communication?

If we are able to succeed in raising reproduction numbers in captivity to what is recorded in nature, then the future cuttlefish aquaculture industry will have to rely on a breeding selection protocol that still needs development. S. officinalis is a semelparous species and this implies a different brood stock management that used for most finfish. Until now, it has been a common practice to use cultured broodstocks to obtain animals for the subsequent generations (Sykes et al. 2006b). Such closed-cycle practice with captive breeders may have led to reproductive isolation from wild populations and a resultant loss of genetic variability due to the low effective breeding population size and inbreeding. We need to address this issue, by determining the effective number of breeders contributing for reproduction in an integrative way, by using behavioral analysis and paternity studies, and quantifying the loss of genetic variation in consecutive cultured generations at given culture conditions. To achieve this objective, we will have two lines of breeders: one according to Sykes et al. (2006a) and another were we will establish the minimum level of outbreeding by adding “new blood” at different generations.

After, we will use the data to redesign the existing cuttlefish husbandry protocol based on a statistical approach that will determine the importance of each variable under study in this project and the magnitude of influence in cuttlefish reproduction in captivity.

The accomplishment of the objectives of the current proposal will allow not only a better understanding of cuttlefish biology, behaviour and genetics, but will also be of extreme importance for other cephalopod species and industry application in the future.