Introduction Reproduction of many temperate fishes is seasonal and the maturation and spawning of their gametes is under photothermal control. Reproductive success of first generation (G1) common sole Solea solea has been low. This restricts domestication and consequently economic viability of commercial culture. In this study, we have investigated the photothermal effects on the sexual maturation during the prespawning months in G1 sole that were a) outdoor housed under the natural photothermal regime, or b) indoor housed under artificial photothermal induction. Methods Maturation status was assessed in male and female G1 broodstock in November as controls, after which the remaining population was divided over two outdoor tanks placed in a pond and two indoor recirculating aquaculture system (RAS) tanks. Repeatedly maturation status was assessed for male and female fish in one tank for each condition in January, February and during spawning in early April, while the other tank was untouched not to disturb the fish in achieving reproductive success. Maturation status was assessed by determining the gonadosomatic index (GSI) and blood plasma steroid levels. The sole genome was sequenced in order to retrieve gonadotropin sequences and perform quantitative real-time PCR in females. Results and Discussion Successful mass spawning and egg fertilisation occurred in all experimental outdoor and indoor tanks and gonadal development was similar for males and females under both conditions. Higher E2 and T levels were found in indoor housed females which may have caused differences in vitellogenesis as also indicated by lower hepatosomatic indices. The expression of common glycoprotein unit a (gpa), fshß and lhß revealed similar temporal expression profiles between outdoor and indoor housed females but the latter showed less individual variation. Conclusion G1 sole was reproduced successfully at large scale in captivity, both in outdoor pond tanks as in indoor RAS tanks. The results indicate the importance of the natural photothermal regime in inducing sexual maturation in sole, as in temperate fish species in general. Specifically, a significant cold period (2-3 months at 5-7 °C) may be permissive for the action of FSH which levels will subsequently decrease and LH levels increase during rising temperatures towards spawning. The sole genome will be instrumental in unraveling its maturation and reproduction impairment under captive conditions in future studies.
|Publication status||Published - 2014|
|Event||10th International Symposium on Reproductive Physiology of Fish, Olhão, Portugal - |
Duration: 25 May 2014 → 30 May 2014
|Conference||10th International Symposium on Reproductive Physiology of Fish, Olhão, Portugal|
|Period||25/05/14 → 30/05/14|
Palstra, A. P., Blok, M. C., Kals, J., Blom, E., Tuinhof-Koelma, N., Dirks, R. P., ... Blonk, R. J. W. (2014). In- and outdoor reproduction of first generation common sole under a natural photothermal regime: Temporal progression of sexual maturation determined by plasma steroids, genome sequencing and pituitary gonadotropin expression. Abstract from 10th International Symposium on Reproductive Physiology of Fish, Olhão, Portugal, .