Role of fat bodies in oocyte growth and recruitment in the frog Rana cyanophlyctis (Schn.)

Abstract

Effects of 30-day bilateral fat body excision in February and November and replacement with 10 or 20 mg fresh aqueous fat body homogenate 6 days a week for 30 days, unilaterally or bilaterally fat body excision plus 20 IU human chorionic gonadotrophin (HCG) in February, and long-term (60 days) fat body excision in March-April were studied in Rana cyanophlyctis. In addition, the effect of ovariectomy on fat body weights in February and November was also studied. The frogs were fed 6 days a week with live guppies ad libitum. The ovarian follicular kinetics was studied by estimating the numbers of first growth phase (FGP), medium and large second growth phase (MSGP and LSGP) oocytes and atretic follicles. Regardless of season, 1-month fat body ablation caused a significant reduction in LSGP oocytes, gonadosomatic index, and increase in atretic follicles. Administration of 20 mg fat body homogenate to fat-body-excised frogs prevented the fall in the number of LSGP oocytes and the gonadosomatic index. In fact, there was a significant increase in the LSGP oocytes and percentage weight of ovaries in these frogs. Follicular atresia was greatly reduced due to fat body homogenate (10 or 20 mg) administration. In 30-day unilaterally fat-body-extirpated frogs, the mean weight of the ipsilateral ovary was reduced to 50% compared to that of the shamoperated frogs due to increased follicular atresia and associated decrease in LSGP oocytes. The administration of HCG increased recruitment of SGP oocytes in unilaterally as well as bilaterally fat-body-ablated frogs. This was accompanied by a reduction in atresia of oocytes and elevation of the gonadosomatic index. Interestingly, in long-term fat-body-ablated frogs, ovarian weight recovered and follicular kinetics in them was identical to that found in shamoperated control frogs. Furthermore, in 30-day ovariectomized frogs, in both seasons there was a significant rise in fat body weights. The above findings in R. cyanophlyctis suggest that fat bodies have a role in vitellogenesis, and they serve as immediate sources of lipid energy needed for follicular growth. If adequate food is provided to fat-body-excised frogs, after an initial setback, ovarian growth commences by drawing lipids from other sources. It is concluded that fat bodies in the frog have a supporting and possibly not an obligatory role in vitellogenic growth of oocytes.

Sexual patterns of prebreeding energy reserves in the common frog Rana temporaria along a latitudinal gradient

“…follicular maturation, spermatogenesis, behavioural activities) during the time when energy intake is absent or minimal. Further, experimental studies in ranid anurans have also supported a functional link between lipid stores and vitellogenesis (Rana cyanophlyctis: Prasadmurthy and Saidapur 1987, Rana tigrina: Saidapur and Hoque 1996, Girish and Saidapur 2000 and testicular activity (R. hexadactyla: Kasianthan et al 1978). Considering the difference between sexes in the timing of the main energetic investments into reproduction in most temperate zone anurans, i.e.…”

“…However, the risk of encountering ''bad conditions'', making foraging and energy gathering problematic (e.g. Further, experimental studies in ranid anurans have also supported a functional link between lipid stores and vitellogenesis (Rana cyanophlyctis: Prasadmurthy and Saidapur 1987, Rana tigrina: Saidapur and Hoque 1996, Girish and Saidapur 2000 and testicular activity (R. hexadactyla: Kasianthan et al 1978). Further, northern R. temporaria have more pronounced iteroparous life histories, with longer life spans and lower yearly reproductive effort (Miaud et al 1999, Hettyey et al 2005.…”

Degeneration of germ line cells in amphibian ovary

“…Degeneration of diplotene oocytes was reported mainly as the physiological response of a female organism to various stresses, such as excision of fat bodies or long‐term captivity in Rana cyanophlyctis (Prasadmurthy and Saidapur 1987; Pancharatna and Saidapur 1992), heat treatment in Rana sylvatica (Witschi 1929) and Rana catesbeiana (Wang et al. 1980), starvation in Xenopus laevis (Dumont 1972), and adverse light regime and overcrowding in captivity in Bufo bufo (Jørgensen 1992).…”

A review of the reproductive system in anuran amphibians

“…The fat bodies are involved in the metabolism of gonadal processes [1,49], mainly in the synthesis and storage of lipids (diglycerides and sterols) [50], fat-soluble vitamins, and esters [51]. Fat bodies also participate in energy supply [52], folliculogenesis, gonadosomatic index (gonad weight/body weight × 100), oxygen uptake [7], yolk production [53], and steroidogenesis. Fat bodies synthesize pregnenolone, progesterone, dehydroepiandrosterone, testosterone, and estrone.…”

“…Meanwhile, the female frog's reproductive system comprises oviducts and ovaries attached to fat bodies. The ovaries' fat bodies contribute to the formation of follicles, oocytes, hormones, and yolk [7][8][9]. The reproductive process begins in the ovaries with the formation of oogonia and oocytes [10].…”