Locomotor Activity Rhythms in the Hagfish under Expanded or Contracted Light-Dark Cycles

The relationship between sex steroid hormone profiles in plasma and gonadal function in hagfish is poorly understood. In the present study, plasma concentrations of estradiol, testosterone, and progesterone were examined with respect to gonadal development, sexual differences, and possible function of atretic follicles in the brown hagfish, Paramyxine atami, using a time-resolved fluoroimmunoassay. Plasma concentrations of these three hormones were low in juveniles of both sexes. In females, plasma estradiol showed a significant correlation with ovarian development, with the highest concentrations in late vitellogenic adults. Plasma testosterone and progesterone also increased significantly in non-vitellogenic adult females; however, plasma testosterone showed no significant differences among adult females at different ovarian developments, while plasma progesterone was significantly lower in late vitellogenic adults than it was in non-vitellogenic adults. Vitellogenic females that possessed atretic follicles showed significantly lower concentrations of all three hormones than females that only possessed normal follicles. In males, no significant differences were found in plasma estradiol or testosterone levels among groups of different developmental stages of the testis, while plasma progesterone showed a clear inverse relationship with testicular development. Thus, differences were found in plasma sex steroid hormone profiles between male and female P. atami. Moreover, plasma estradiol showed a significant correlation with ovarian development, which suggests that estradiol is involved in the regulation of ovarian development. The present study also revealed that steroid hormone production was strongly suppressed in females that possessed atretic follicles in their ovaries.

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Locomotor Activity Rhythms in the Hagfish under Expanded or Contracted Light-Dark Cycles

Abstract: This study reports on the locomotor activity rhythms of Paramyxine atami exposed to expanded and contracted photoperiodic regimes (Tin hours) divided into light and dark periods of equal duration. Nocturnal activity was entrained by the range of 23.5 l i•…T•…25.2 h on average.

Cited by 3 publications

References 5 publications

Effects of estradiol or testosterone treatment on expression of gonadotropin subunit mRNAs and proteins in the pituitary of juvenile brown hagfish, Paramyxine atami

Effects of estradiol or testosterone treatment on expression of gonadotropin subunit mRNAs and proteins in the pituitary of juvenile brown hagfish, Paramyxine atami

Molecular cloning of cytochrome P450 side-chain cleavage and changes in its mRNA expression during gonadal development of brown hagfish, Paramyxine atami

Relationships between Plasma Concentrations of Sex Steroid Hormones and Gonadal Development in the Brown Hagfish,Paramyxine atami

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