CONICET | Buscador de Institutos y Recursos Humanos

Pejerrey (Odontesthes sp., Atheiniformes) is the common name of several South American fish species considered to be promising for intensive aquaculture. However, one major drawback to achieve this goal is their slow growth rate. Growth hormone of O. bonariensis has recently been sequenced and characterized, but the endocrine control of somatic growth in this species is still uncovered. Insulin growth factor-I (IGF-I) of O. bonariensis and O. hatcheri has been cloned and sequenced. Since their sequence showed high identity (99%) we have been able to develop a quantitative Real Time PCR to measure IGF-I mRNA of both species. IGF-I mRNA levels were evaluated after injecting 1 μg/g-bw recombinant homologous growth hormone (pjGH). In O. bonariensis, a significant increase of IGF-I expression was found at 9 hours post-injection returning to basal levels 4 hours later. Also, GH stimulation showed a dose-dependent response and reached a 6 fold IGF-I maximum increase when 2.5 µg pjGH/g were injected. In this context, IGF-I mRNA quantification may provide a valid tool to study and monitor growth. It is also know that pejerrey show high levels of stress in culture due to its high sensitivity to habitat changes and this stress is may be related to their slow growth rate. Then we decided to evaluate growth status and stress of O.hatcheri in captivity. The fish were captured in Carrilaufquen Lake (Rio Negro-Argentina), transported and adapted to tank culture. Hepatic IGF-I mRNA and plasmatic cortisol levels (RIA) were measured at 0, 1, 3, 6 and 9 days after capture. Cortisol was significantly increased at day 3 and remained elevated until the end of the experience. Pre-adapted fish (wild fish held in captivity for seven months) also showed an increased cortisol concentration compared with captured fish at day 0. IGF-I mRNA levels did not show any variation during the experiment but pre-adapted fish had a lower relative IGF-I mRNA concentration. These findings suggest that growth could be affected by long term captivity.