BACKGROUND: The relationship between the activity of the epiphysis and gonads in rats of different sex and age in different seasons of the year was determined by studying the levels of melatonin and testosterone in the blood plasma. Determination of the levels of melatonin and testosterone in the serum of rats was carried out by enzyme-linked immunosorbent assay. To assess the relationship between the levels of melatonin and testosterone the correlation coefficient was calculated. Based on the study of the levels of melatonin and testosterone in serum the circannual relationship between the activity of the pineal gland and gonads in males of reproductive age has been determined. In females, the relationship between the levels of melatonin and testosterone without the circannual dependence has been determined. The strongest correlation between melatonin and testosterone is present in males at the age of 9 months in autumn, and it corresponds to the human age of 29-30 years.
Rasbora tawarensis is an endemic freshwater fish in Lake Laut Tawar, Aceh Province, Indonesia. Unfortunately, its status is regarded as critical endangered with populations decreasing in recent years. To date no information on the spawning activities of the fish are available. Therefore, this study provides a contribution to the knowledge on reproductive biology of R. tawarensis especially on spawning seasons as well as basic information for conservation of the species.
Plasma sex steroid hormonal profile and gonad histology were correlated to study the annual reproductive cycle of Hemibagrus nemurus. Hormones were measured by Enzyme Linked Immunosorbent Assay. Gonad tissues were observed by using light microscopy. The highest testosterone (T) value for male was observed in November and that of female was in October. 11-ketotestosterone (11-KT) and 17β-estradiol (E2) levels were highest in June and November, respectively. Hormonal profiles of T, 11-KT and E2 showed several peaks which indicated a non-seasonal pattern. There were significant differences (p