The effect of environmental cues and neurotransmitters on male sexuality of the eastern Pacific Penaeus (Litopenaeus) species
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This research evaluates the effect of ecosystem anomalies during El Niño 2009-2010 and the role of serotonin and the dopamine antagonist: spiperone over the male reproductive mechanism of three species of the sub-genus Litopenaeus from the Gulf of Nicoya, Costa Rica. Wild males of Penaeus (Litopenaeus) stylirostris and Penaeus (Litopenaeus) occidentalis were captured during 2009-2010 for spermatophore quality analysis, complemented with sexual performance under captivity. Additionally, these species and Penaeus (Litopenaeus) vannamei were used to study the role of serotonin alone and in combination with spiperone on male sexual maturation, using spermatophore quality parameters as indicators. Our findings indicate that during El Niño 2009-2010 the adult male population of P. stylirostris and P. occidentalis suffered a distinctive reproductive declined of reversible nature since after moving males to a stable environment (maturation laboratory conditions), in the same geographical location, both species improved significantly their sexuality in a short period of time, particularly P. stylirostris. These findings suggest that environmental cues are a primary controlled mechanism for spermatophore production and that captivity do not affect negatively the sexual status of wild Litopenaeus. Therefore, it seems that both species are capable of reaching their optimum sexual potential under controlled reproduction conditions by managing the environment adequately. Comparative studies in following years will help to clarify the relative contributions of El Niño event and fishery overexploitation over male shrimp sexuality. Concerning the role of neurotransmitters, serotonin at 25μg gμ1 body weight (b.w.; 10μ6mol animalμ1) did not induce any improvement on spermatophore quality of P. stylirostris and P. vannamei. Moreover, serotonin plus spiperone (2μg gμ1 b.w.; 10μ7mol animalμ1) injection in P. stylirostris, P. vannamei and P. occidentalis, induced some degree of negative sexual response. These findings suggest that serotonin and dopamine play a different reproductive role in males and females of Litopenaeus; the relative importance of the major known endocrine pathways is discussed.
