The effects of 11-ketotestosterone implants on transcript levels of gonadotropin receptors, and foxl2 and dmrt1 genes in the Previtellogenic ovary of cultured beluga (Huso huso).

The in vivo effect of 11-ketotestosterone (11KT) on transcript levels of the gonadotropin receptors (fshr and lhr) and sex differentiation-related genes (dmrt1 and foxl2) was examined in the ovaries of immature female beluga. For this purpose, six fish were treated with implants containing 2.5 mg 11KT and a placebo group of six females of the same age and gametogenic stage were given a blank implant. The implants were intraperitoneally inserted into 4-year-old females at the previtellogenic stage (mean body weight 5580 ± 165 g) and maintained under culture conditions for 8 weeks. Ovary samples for gene expression analysis of lhr, fshr, dmrt1 and foxl2 were collected by biopsy at 3 and 8 weeks post implantation. Diameters of oocytes increased in response to 11KT treatment, both at 3 and at 8 weeks post implantation, but no obvious changes were evident in cytology. Three weeks of 11KT treatment did not affect target gene expression, but a tendency for a time-dependent decrease of lhr and dmrt1 mRNA levels was observed in both treatment and placebo groups. By 8 weeks of treatment, however, 11KT implants provoked the upregulation of fshr and foxl2 transcript levels. Furthermore, lhr and dmrt1 transcript abundances recovered by 8 weeks of exposure in both blank- and 11KT-implanted beluga. These results suggest that 11KT, either directly or indirectly, may affect gametogenesis and regulate some key components of the reproductive axis in female beluga.

The effects of 11-ketotestosterone on occupation of downstream location and seawater in the New Zealand shortfinned eel, Anguilla australis.

The androgen 11-ketotestosterone (11KT) is associated with the physiological and morphological changes that occur during the transformation of sedentary ('yellow') freshwater eels (Anguilla spp.) into their migratory form ('silver') prior to their spawning migration in the ocean. In this study, we investigate the possible role of 11KT in modulating behaviors consistent with downstream migration; i.e., downstream and salinity preference in the New Zealand shortfinned eel (A. australis). Unlike silvering, 11KT did not induce preference for downstream locations, scored as presence at the downstream ends of 35 m raceways. Likewise, there was no evidence for increased salinity preference in 11KT-treated yellow eels, scored as preference for sea water over fresh water in a choice experiment. However, the 11KT treatment induced higher frequency of movements between fresh water and sea water, which may indicate restlessness.