Prospection of genes related to the growth of the pink shrimp Farfantepenaeus paulensis
In the first stage of this study, experiments were carried out to evaluate the growth and survival of shrimp native to southern Brazil, of the species Farfantepenaeus paulensis, grown in different salinities. For this, groups of 200 PL47 (post-larvae aged 47 days), with an average initial weight (± SD) of 0.022 g (± 0.008), produced at the Marine Aquaculture Station (FURG) were grown for 60 days in cages (1m3) suspended in two tanks with 20,000 L of water, at salinities 5 and 30. Salinity levels were considered different treatments, which had three repetitions each. The prawns were fed ad libitum, with a commercial feed provided twice a day in trays. The means (± SD) of temperature, pH, dissolved oxygen and total ammonia (N-AT) were 25.5C (± 1.9); 8.07 (± 0.13); 5.16 mg / L (± 1,07) and 0.042 mg / L (± 0.013), respectively, these values being considered acceptable for this species. At the end of the experiment, the shrimp were counted and weighed, with an average survival of 97% for both treatments. The results obtained demonstrated a significantly higher final weight (P <0.05, ANOVA followed by the Tukey test) of the shrimps acclimated to the lowest salinity, with means (± SD) of final weight equal to 1.08 g (± 0, 3) and 0.62 g (± 0.15) at salinity 30. These results probably reflect the action of genes induced by low salinity that also have an effect on growth. Continuing the work, the five lightest and five heaviest shrimp from each repetition were immediately frozen in liquid nitrogen for the next stage. In the second phase of this work,a gene prospection study was carried out using the organisms that showed a differentiated growth, with the objective of identifying genes related to the growth process and salinity tolerance. The tested method was an adaptation of the usual technique of analysis of the differential expression of genes, through the reverse transcription of the total RNA followed by the polymerase chain reaction (DDRT-PCR). Using the cryopreserved tissues of the shrimp, the total RNA was extracted and the respective complementary DNAs (cDNAs) were produced. From the comparison between the genes transcribed in the two size classes, genes with differential expression were identified in the comparison between large and small individuals. Two of these genes, hitherto unknown to pink shrimp (cyclophilin and hemocyanin), were isolated, cloned,sequenced and compared with genes from other species stored in the World Bank for genes (Genbank). The results obtained in this study demonstrate the viability of the methodology used to identify genes related to important characteristics for aquaculture.