Efectos de la generación de energía hidroeléctrica en la reproducción de Prochilodus magdalenae (Prochilodontidae): evidencia de la respuesta endócrina / Hydropower effects on Prochilodus magdalenae (Prochilodontidae) reproduction: evidence from endocrine response

RESUMEN Objetivo. Describir la respuesta endocrina asociada con la reproducción de un pez potamódromo tropical ante cambios en el régimen de descarga de caudal producido por la generación de hidro-energía en un río Andino. Materiales y métodos. Se analizó la reproducción de Prochilodus magdalenae en individuos de dos sectores de una cuenca neotropical: uno con flujo hidrológico natural y otro con un régimen regulado. Resultados. En la sección de la cuenca con flujo natural, se encontró que la producción de hormonas relacionadas con la reproducción de peces (FSH y LH) estaba correlacionada con el índice gonadosomático, mientras que en peces bajo la influencia del pulso de agua producto de la operación hidroeléctrica esta correlación no fue detectada. Conclusiones. La producción de hormonas asociadas con la reproducción en peces potamódromos fue sensible a cambios en el nivel/caudal. En consecuencia, peces expuestos a las alteraciones en el pulso de caudal estarían recibiendo estímulos ambiguos que afectan la producción de hormonas, la sincronización de la reproducción con las señales ambientales y la maduración, lo cual es esencial para el éxito reproductivo.

ABSTRACT Objective. Describe the endocrine response associated with the reproduction of a tropical potamodromous fish under changes in the flow discharge produced by hydropower in an Andean. Materials and methods. We analyzed Prochilodus magdalenae reproduction in individuals from two sectors of a Neotropical river basin: one with a natural flow and another one with a regulated hydrological regime. Results. In the sector of the basin with the natural flow we found that the production of hormones related with fish reproduction (FSH and LH) was correlated with the gonadosomatic index, while in fish experiencing hydropeaking due to hydroelectric operation no such correlation was detected. Conclusions. Hormone production associated to reproduction of the Potamodromous fish was sensitive to changes in water level and discharge. Then, fish exposed to hydropeaking would be receiving ambiguous stimuli that affect hormone production, reproduction synchronization with environmental cues, and ripening, which are essential for reproductive success.

Gonadotropin subunits of the characiform Astyanax altiparanae: Molecular characterization, spatiotemporal expression and their possible role on female reproductive dysfunction in captivity.

To better understand the endocrine control of reproduction in Characiformes and the reproductive dysfunctions that commonly occur in migratory fish of this order when kept in captivity, we chose Astyanax altiparanae, which has asynchronous ovarian development and multiple spawning events, as model species. From A. altiparanae pituitary total RNA, we cloned the full-length cDNAs coding for the follicle-stimulating hormone ß subunit (fshb), the luteinizing hormone ß subunit (lhb), and the common gonadotropin α subunit (gpha). All three sequences showed the highest degree of amino acid identity with other homologous sequences from Siluriformes and Cypriniformes. Real-time, quantitative PCR analysis showed that gpha, fshb and lhb mRNAs were restricted to the pituitary gland. In situ hybridization and immunofluorescence, using specific-developed and characterized polyclonal antibodies, revealed that both gonadotropin ß subunits mRNAs/proteins are expressed by distinct populations of gonadotropic cells in the proximal pars distalis. No marked variations for lhb transcripts levels were detected during the reproductive cycle, and 17α,20ß-dihydroxy-4-pregnen-3-one plasma levels were also constant, suggesting that the reproductive dysfunction seen in A. altiparanae females in captivity are probably due to a lack of increase of Lh synthesis during spawning season. In contrast, fshb transcripts changed significantly during the reproductive cycle, although estradiol-17ß (E2) levels remained constant during the experiment, possibly due to a differential regulation of E2 synthesis. Taken together, these data demonstrate the putative involvement of gonadotropin signaling on the impairment of the reproductive function in a migratory species when kept in captivity. Future experimental studies must be carried to clarify this hypothesis. All these data open the possibility for further basic and applied studies related to reproduction in this fish model.