Circannual rhythms in the activity of the parathyroid gland and ultimobranchial body cells of the frog Rana temporaria (Anura, Amphibia).

The annual activity of the parathyroid gland cells and those of the ultimobranchial body cells of the frog Rana temporaria is quantitatively investigated by a morphometric study. A cosinor analysis shows a periodic succession of different parameters. The secretory activity of the parathyroid cells starts after a maximal value of external temperature in July. This activity is followed by an increase of plasma calcium which seems to induce the activity of the ultimobranchial cells.

Failure to relate thyroid hormones and in vitro 5'-monodeiodination activity to oocyte development and sex steroids in the giant swamp frog Dicroglossus occipitalis at the equator.

Females of the giant swamp frog Dicroglossus occipitalis were captured in Zaïre close to the equator in the course of 1 month. During this period, females with fully developed eggs were found, together with females of which the eggs were still in the first developmental stages. A close relationship was established between the maturation of the eggs and the studied gonadal factors: the gonadosomatic index, the oviduct weight, plasma estradiol-17 beta (E2) concentrations, plasma testosterone concentrations, and the total ovarian E2 concentrations. At the level of the thyroidal axis, the studied factors (plasma thyroxine (T4), plasma triiodothyronine (T3), plasma T3/T4 ratio, T4 and T3 concentrations, and the T3/T4 ratio in the thyroids and the 5'-monodeiodination activity (5'-D-activity) in the skin and kidney homogenates) did not show parallel changes with the maturation process of the eggs. These results indicate that no causal relation has to exist between the annual variation in thyroid hormones and the annual reproductive patterns as found in frogs from the tropical or temperate climatic region.

Thyroid hormones, testosterone, and estradiol-17 beta in plasma of Epomops franqueti (Tomes, 1860) (Chiroptera) in the rain forest of the Equator.

Using Japanese catching nets a total of 77 males and 37 females of the fruit eating bat Epomops franqueti (Megachyroptera) were captured during a period of 1 year around Kisangani (Zaïre). Adult males with white epaulets weighing 143 +/- 3.6 g (18) had their testes present in the scrotum and higher plasma concentrations of thyroxine (T4) and testosterone than adult males without epaulets and with abdominal testes (weight 107.5 +/- 2.0 g (39)) or juveniles (72.7 +/- 2.8 g (20)). Mean embryo weight of pregnant bats was 4.26 +/- 1.09 g (12) ranging from 1.8 to 14.8 g whereas body weight of mothers (+ embryos) was 117.0 +/- 3.6 g (12). Body weight of nonpregnant bats was 107.3 +/- 2.1 (10) and of female juveniles 74.6 +/- 4.3 (15). Plasma concentrations of triiodothyronine (T3) were lowest in nonpregnant adults and comparable in juveniles and pregnant bats. No difference in plasma T4 concentrations was found between all groups. Estradiol-17 beta concentrations were three times higher in pregnant bats compared to nonpregnant ones or juveniles. A possible relationship between these high figures and elevated T3 values has been discussed.

Reproductive cycle, thyroxine and corticosterone in females of the giant swamp frog Dicroglossus occipitalis at the equator.

Females of the giant swamp frog Dicroglossus occipitalis were captured in the tributaries of the Zaïre River near Kisangani, a town situated close to the equator (00 degree 31' N) with virtually constant conditions as to photoperiod, temperature, precipitation, and relative humidity. An annual variation in the reproductive capacity of this species could be demonstrated. A reproductive quiescence with a low gonadal somatic index (GSI), undeveloped eggs, and minimal plasma concentrations of estradiol-17 beta (E2) and progesterone (P4) was found from October to January. E2 and P4 and thyroxine (T4) contents of the thyroids were positively correlated with GSI and egg size. Plasma T4 concentrations, however, were negatively correlated with GSI, whereas variations in corticosterone correlated only with E2. No correlation between plasma concentrations of glucose and GSI or all other hormonal parameters could be found. It is concluded that during egg maturation, increased amounts of E2 and P4 are produced. The observed variations in thyroidal and plasma T4 may be the result of an activation of thyroid function by the peripheral conversion of T4 into triiodothyronine.