SHORT NATURAL PHOTOPERIOD STIMULATES

BUSSO JM; PONZIO MF; DOMINCHIN MF; FIOL DE CUNEO MH; RUIZ RD

Jornada; 2da Reunión Conjunta de Sociedades de Biología de la República Argentina.; 2011

Hystricomorphic rodents are particularly well represented in South America; among them, Chinchilla spp is threatened and the presence of remaining colonies in the Argentinean Andes is uncertain, although a domestic form is widespread in breeding farms. Chinchilla lanigera exhibits reproductive rhythms with two breeding peaks in spring and summer; however, there are not studies about photoperiod effects on its reproductive physiology. Domesticated males (n=7) were studied to determine the effects of natural photoperiod upon testicular activity in Córdoba (31°S–64°W) during May, August, November, and February; urine (24h) was obtained before to semen collection by electroejaculation. Differences in androgen excretion (ng/mg of creatinine) were detected by repeated measures ANOVA, the highest values were found associated with “short” light/dark cycles (autumn-winter); acrosome intact sperm percentages were higher during winter-spring than summer-autumn, and the lowest sperm concentration was detected in summer (p<0.05). However, seminal volume and sperm functional activity showed non significant seasonal changes. These results suggest that the chinchilla male gonadal activity is affected by natural photoperiod; therefore, it is possible to postulate that this species would be a “short-day” breeder.