Endocrine regulation of pejerrey (Odontesthes bonariensis) spermatogenesis in the wild

ELISIO, M., CHALDE T., MIRANDA, LA.

Rennes

Conferencia; 27th Conference of European Comparative Endocrinologists; 2014

The endocrine mechanisms that regulate spermatogenesis in fish and theirinteraction with environmental cues have been poorly studied comparedwith oogenesis. The aim of this work was to study the spermatogenesis inpejerrey fish under the influence of photoperiod and water temperaturefluctuation in a Pampas shallow lake (Chascomús, Buenos Aires, Argentina),evaluating the transcript levels of brain Gnrh variants and cyp19a1b,pituitary Gths subunits, gonadal Gth receptors, and 11-KT plasmatic levels.Males at spermiogenic phase were mainly observed during spring, and alsoduring autumn, under a photoperiod above 11 hs of light and a watertemperatures below to 21 ºC. Arrested males were observed in summer(water temperatures above 21 ºC), and some of them were caught duringwinter (9-10 hs of light). Males at spermatogonial phase were mainlyobserved in autumn, while most males at meiotic phase were caught inwinter (lowest photoperiod and water temperature conditions). Gnrh-Iincreased in proportion to the testicular development. On the other hand,while gnrh-III showed a significant increase at the spermatogonial phase,cyp19a1b increased significantly during the meiotic phase and remainedelevated up to the spermiogenic phase. No significant variation wasobserved for gnrh-II. At pituitary level, fshb increased progressively up to themeiotic phase, and decreased then during the spermiogenic phase. Whilegph! fluctuated similarly to fshb, lhb showed no significant variationbetween the gonadal stages. Gonadal Gth receptors showed a significantincrease only during the spermiogenic phase, being this event more evidentfor lhcgr. Plasma levels of 11-KT increased proportionally to the advance ofspermatogenesis up to the meiotic phase and decreased then duringspermiogenic phase. Present results suggest that in pejerrey, thespermatocyte production occurs mainly during winter (low temperature andshort daylength conditions) through the stimulation of FSH and 11-KT, whilespermiation occurs after photoperiod increase, with water temperaturesbelow to 21 ºC, and is related to a rise of gnrh-I, cyp19a1b and lhcgr.