Density-dependent growth and metamorphosis in the larval bronze frog Rana temporalis is influenced by genetic relatedness of the cohort

Effects of density and kinship on growth and metamorphosis in tadpoles ofRana temporalis were studied in a 2x4 factorial experiment. Fifteen egg masses were collected from streams in the Western Ghat region of south India. The tadpoles were raised as siblings or in groups of non-siblings at increasing density levels, viz. 15, 30, 60 and 120/5 l water. With an increase in density level from 15 to 120 tadpoles/5 l water, duration of the larval stage increased and fewer individuals metamorphosed irrespective of whether they belonged to sibling or non-sibling groups by day 100 when the experiments were terminated. The size of individuals at metamorphosis declined significantly with increase in the density of rearing. However, at higher densities (60 and 120 tadpoles/5 l water) sibling group tadpoles performed better compared to mixed groups and took significantly less time to metamorphose. Also, more individuals of sibling groups metamorphosed compared to non-sibling groups at a given density. Mixed rearing retarded growth rates, prolonged larval duration resulting in a wider spectrum of size classes, and lowered the number of individuals recruited to terrestrial life. The study shows that interference competition occurred more strongly in cohorts of mixed relatedness than in sibling groups

The ontogeny of kin recognition in tadpoles of the toadBufo melanostictus (Anura; Bufonidae)

The ontogeny of kin recognition and influence of social environment on the development of kin recognition behaviour was experimentally investigated in tadpoles of Bufo melanostictus that lived in aggregations and showed low larval dispersion. Embryos and tadpoles of the toad were reared as (i) kin only, (ii) with kin and non-kin (separated by a mesh screen), and (iii) in isolation. They were tested for the ability to discriminate between (i) familiar siblings and unfamiliar non-siblings, (ii) familiar siblings and familiar non-siblings and, (iii) unfamiliar siblings and unfamiliar non-siblings. All tadpoles were fed on boiled spinach before conducting trials. Preference of test tadpoles to associate near the end compartments whether empty or containing members of specific stimulus groups was assessed using a rectangular choice tank. When tested in tanks with empty end compartments, the test tadpoles showed random distribution and thus no bias for the apparatus or the procedure. In the presence of kin/non-kin in the end compartments a significantly greater number of test tadpoles spent the majority of the time near familiar or unfamiliar kin rather than near familiar or unfamiliar non-kin. Kin discrimination ability persisted throughout larval development. Familiarity with siblings is not required for discriminating kin from non-kin, and kin discrimination ability is not modified following exposure to non-kin. Also, involvement of dietary cues is unlikely to be the prime mechanism of kin recognition inB. melanostictus unlike in some other anurans

Effect of photoperiod and temperature on ovarian cycle of the frog Rana tigrina (Daud.)

The effect of varying photoperiod regimes (LD: 20,4; 4,20; 6,18; 18,6 and 12,12) on ovarian follicular development was analysed in the frogRana tigrina maintained at ambient and constant 30° ± l° C for 3 months. The experiments were conducted in early recrudescent and quiescent phases. The frogs were fed guppiesad libitum on alternate day. None of the photoperiod regimes had any effect on the ovaries or the fat bodies, whereas exposure to constant high temperature (regardless of photoperiod) during recrudescent phase induced production of greater number of eggs (~ 18000 vs 13000 in controls) of ovulatory sizes (> 1400µm) compared to the corresponding controls maintained at ambient temperature. Hence, ovarian mass also increased in these frogs. In the quiescent phase, high temperature merely enhanced growth of previtellogenic oocytes. In both the phases high temperature caused a reduction in the fat bodies over the respective controls, possibly due to increased metabolic activity. The above findings indicate that temperature plays a key role in the regulation of ovarian cycle ofRana tigrina and that the photoperiodic mechanisms may not govern the annual recrudescence of ovaries in the frog. The study also shows that the frog exhibits the phenomenon of "phenotypic plasticity" in its reproductive behaviour by producing significantly greater number of eggs in response to elevated temperature

Dynamics of oogenesis in the tropical anuran Rana tigrina (Amphibia: Ranidae) with special reference to vitellogenic cycles in wild-caught and captive flogs

The ovarian cycle of Rana tigrina was analysed by quantifying the developing oocytes (classified into stages on the basis of diameter) and atretic ones at monthly intervals. Stages I to IV represent oocytes in the first growth phase and the remaining ones the vitellogenic or second growth phase. Stages I-III occurred year round but exhibited significant variation in their number. The number of stage II oocytes always dominated the other stages. Recruitment of oocytes to stages IV and V in April marked the initiation of vitellogenic growth in all specimens. Of the 30 to 35% second growth phase oocytes, 25 to 28% reached ovulatory sizes by June. After spawning the ovarian mass declined drastically from 15 to 0.2% of body mass in July. Atresia was maximal (5%) in August. In other months, it was less than 1.5% of the total oocytes. Oogenic episodes occurred in March and July yielding new oocytes. The number of first growth phase oocytes fluctuated from 65 to 95%. The fluctuation was inversely correlated with the second growth phase oocytes indicating a 30 to 35% annual turnover rate of oocytes in the frog. The final egg number/ovarian mass is positively correlated with the snout-vent length as well as body mass of the frogs. R. tigrina produces about 4000 eggs/100g body mass. Further, the mean number of yolky eggs/100 g body mass and the total volume (V) of eggs/frog were highly correlated. Frogs living in captivity produced fewer eggs compared to the wild ones (3594 ± 227 in captive vs 4704 ± 317 in wild frogs). Also, these frogs failed to breed though they showed amplexus with breeding males. Injection of desoxycorticosterone acetate however induced spawning in 4 out of 5 frogs. They released about 3000 eggs each. Captivity seems to mainly impair breeding and to a little extent the vitellogenic growth of oocytes in R. tigrina

Peripheral blood and ovarian levels of sex steroids in the cyclic hamster

Changes in progesterone (P), testosterone (T), estrone (E1) and estradiol-17β (E2) in peripheral blood, ovary, corpora lutea (CL) and in the nonluteal portion of the ovary (NLO) were studied in the cyclic hamster by RIA. In addition, androstenedione (A) was measured, but only in serum. Serum P levels were the same on Days 1 (day of ovulation) and 2 at 0900 h (5 ng/ml), but declined markedly on Day 3 and on the morning of Day 4 (proestrus). After the LH surge on the afternoon of Day 4, serum and ovarian levels of P increased abruptly until 1900 h to 11-18 ng/ml and declined slowly thereafter. Peak T levels in both serum (209 pg/ml) and the ovary occurred between 1400-1500 h of Day 4, paralleling the rising P levels. However, T levels declined rapidly after 1600 h to undetectable levels by 1900 h, but there was a second peak of T by 2300 h in serum which was matched by the ovary. Serum levels of E1 and E2 began to rise on Day 2, reaching peak values by Day 4 between 1200 and 1400 h (41 pg/ml and 152 pg/ml, respectively). Peak ovarian concentrations of E1 and E2 were reached on Day 4 at 0900 h. These high levels were maintained up to 1600 h of Day 4 and declined rapidly thereafter. The serum levels of E1 were about one-third as high as E2 and were not as drastically affected on the evening of Day 4. Serum androstenedione ranged from 1-2 ng/ml, but changes throughout the cycle were not as striking as for the other steroids. However, increased levels of A were associated with decreased levels of estrogens and vice-versa. Therefore, the circulating levels of A probably reflect altered secretion rates of other steroids. Administration of 5 μ g LH on the evening of Day 4 (when all steroid levels are declining) caused significant increases in P and T but not E2. Hence, the refractory period of estrogen synthesis on the evening of Day 4 cannot be attributed to insufficient levels of LH during the preovulatory period

Ovarian steroidogenesis in the proestrous hamster

In the proestrous hamster, in response to the LH surge, there is a dramatic and sustained increase in serum progesterone (P) and transitory increases in testosterone (T), estrone (E1) and estradiol-17β (E2). Ovarian steroidogenesis in the proestrous hamster was analyzed in detail by studying: 1) concentrations of these steroids in the whole ovary, antral follicles (AF) and the nonantral follicular portion of the ovary (NAO) at 1200 h (prior to the LH surge), 1500 h (during the LH surge) and 1800 h (after the LH surge); 2) in vitro steroidogenic production by the AF and NAO, as well as the whole ovary (removed before 1200 h, 1500 h and 1800 h and 3) in vitro effects of LH, FSH and P on steroidogenesis of ovaries removed before the LH surge and incubated for 2 h. P concentration was the same in AF and NAO at 1200 h but increased slightly in the AF with the onset of the LH surge. Both the concentration and production rate of P increased from a minimum at 1200 h (1 ng/mg/h) to a maximum by 1800 h (30 ng/mg/h) in the ovary, AF and NAO. On the other hand, the concentration of T, E1 and E2 was selectively greater in the AF at all times. Maximum T production occurred in the ovaries removed during the LH surge (150 pg/mg/h) followed by a significant decline by 1800 h. However, AF produced negligible amounts of T at all times. In the NAO, the production of T was essentially the same (about 20 pg/mg/h) in all 3 incubations. The production of E1 and E2 was much greater in the AF than in the NAO, especially between 1200-1500 h. By 1800 h, the levels and synthetic capacity for estrogens in the ovary, AF and NAO declined to baseline levels, while the production of P was still very high. These studies indicate that in the proestrous hamster, steroidogenesis in the NAO which largely represents the interstitial compartment is limited to the production of P and androgens and only a negligible fraction passes down the pathway to form estrogens. On the other hand, steroidogenesis is more complete in the AF where it can proceed efficiently as far as estrogens. LH (5-250 ng/ml) added in vitro increased the production rate of all steroids whereas 1 ng LH increased only the synthesis of E2. FSH (100-200 ng/ml) also stimulated E2 production but not E1. Higher concentration of FSH (250 ng/ml) resulted in overall increases in P, T, E1 and E2 possibly due to contamination with LH. Exogenous P (10, 100 ng/ml) had no effect on T or E1 synthesis, but E2 production was enhanced

Interstitium: site of steroid synthesis in the ovary of the long term hypophysectomized hamster

The ovaries of hamsters hypophysectomized (H̅) on the afternoon of proestrus synthesize in vitro substantial amounts of progesterone for as long as 20 days post-H̅ (Taya and Greenwald, 1979b). The purpose of the present study was to identify by histochemistry and ultrastructure the ovarian cell type which still possessed the enzymes capable of steroidogenesis despite the long term absence of gonadotropins. After Day 6 post-H̅, the ovaries contained interstitium and viable and atretic small preantral follicles. The viable preantral follicles were histochemically devoid of Δ 5-3β -hydroxysteroid dehydrogenase (3β -HSDH). Histochemically, there were no appreciable changes in lipids in the interstitial gland cells (IGC) until Day 20 post-H̅, followed by a slight decrease by Day 30. The 3β -HSDH activity in the IGC showed no appreciable changes until Day 6 and thereafter decreased gradually until Day 30. Trace amounts of glucose-6-phosphate dehydrogenase were found in the IGC until Day 6 and thereafter the enzyme was undetectable. The IGC contained only trace amounts of acid phosphatase until Day 10, followed by a gradual increase by Day 30. A single i.p. injection of 5 μg ovine LH on Day 10, 20 or 30 resulted 3 h later in dramatic increases in the concentration of serum progesterone and ovarian progesterone and testosterone but not estradiol-17β . Concomitantly, the depletion of lipid droplets in viable interstitial cells was observed by histochemical and ultrastructural criteria. However, lipid accumulations in degenerating interstitial cells and atretic granulosa cells were unaffected by LH treatment. These data indicate that the interstitium is an active steroidogenic tissue for at least 30 days post-H̅ and that LH can rapidly stimulate synthesis and secretion of progesterone and testosterone by the interstitium in long term hypophysectomized hamsters

In-Vitro steroidogenesis of newly formed corpora lutea and the non-luteal ovary in the rat, rabbit, hamster and guinea-pig

The steroidogenic abilities of the newly formed corpus luteum (8-10 h after ovulation) and the non-luteal ovary were compared in the guinea-pig, hamster, rabbit and rat using an invitro incubation technique. Histologically, newly formed rat corpora lutea (CL) were highly luteinized whereas the CL of the rabbit and guinea-pig were only partially luteinized. The CL of the hamster showed the least amount of luteinization. Serum progesterone was highest in the rat (18 ± 3 (s.e.m.) ng/ml). In the hamster, it was about 8 ng/ml, whereas in the rabbit and guinea-pig it was about 1 ng/ml. Serum androstenedione ranged between 0.5 and 1 ng/ml. Serum testosterone was lowest in the hamster (60 pg/ml) and highest in the rabbit (470 pg/ml), whereas in the rat and guinea-pig, testosterone levels were similar (about 240 pg/ml). Serum oestrogens were at baseline levels in all species. The CL of the rat exhibited considerably greater steroidogenic ability than the CL of the other species, producing 70 ± 6 ng progesterone/mg per h, 215 ± 14 pg androstenedione/mg per h, 49 ± 3 pg testosterone/mg per h, 3 pg oestrone/mg per h and 1 pg oestradiol/mg per h. Rabbit CL produced only progesterone (7 ± 2 ng/mg per h). Newly formed hamster CL produced none of the above steroids. In general, the ability of the CL to produce progesterone in vitro correlated with the degree of luteinization found by histological observation. Guinea-pig CL were embedded deeply in the ovary and could not be obtained without damage. Consequently, a portion of the ovary containing a corpus luteum was incubated. There was no difference in the steroid production by this portion of the ovary compared with the non-luteal ovary. The non-luteal ovary of the rat produced the highest amount of progesterone (10 ± 2 ng/mg per h). The guinea-pig non-luteal ovary produced about 5 ± 2 ng progesterone/mg per h, whereas the non-luteal ovary of the rabbit did not produce any. On the other hand, the hamster non-luteal ovary lost progesterone. Non-luteal ovaries from all species produced androgens. The non-luteal ovary of the guinea-pig contained especially large numbers of atretic antral follicles. The guinea-pig non-luteal ovary produced extremely large amounts of androstenedione (1110 ± 210 pg/mg per h) and testosterone (606 ± 154 pg/mg per h) compared with the amounts produced by the non-luteal ovary of the rat, hamster and rabbit. In the non-luteal ovary, interstitium and atretic antral follicles are the probable source of androgens. Oestrogen production by the non-luteal ovary was at baseline levels in the four species studied correlating with the absence of healthy antral follicles. The results indicate the extreme species differences that exist in ovarian function in the early postovulatory period

Induction of ovarian follicular development in the subadult frog Rana tigrina using luteinizing hormone releasing hormone-acetate

In the subadult Rana tigrina administration of 2 μg luteinizing hormone releasing hormone-acetate/frog six days a week for 4 weeks in April resulted in the formation of medium (in all 8 frogs) and large sized (in 4 out of 8 frogs) yolky oocytes and, concomitant increases in the oviductal mass. The ovarian and oviductal masses showed a 10-fold increase over the control frogs. In untreated frogs the ovaries were transparent and contained first growth phase oocytes only. The oviducts were also infantile. The pituitary sections were stained using antisera raised in rabbit against the β-subunit of human luteinizing hormone and human follicle stimulating hormone. Immunoreactivity, staining intensity, cytoplasmic granulation and, cell, nuclear and cytoplasmic areas of gonadotrophs (B2 cells) increased significantly in luteinizing hormone releasing hormone treated frogs. The above findings suggest that pituitary-ovarian axis in the subadultRana tigrina is responsive to luteinizing hormone releasing hormone and that long-term treatment with the hormone induces cytomorphological changes in the gonadotrophs which result in the conversion of inactive cells into secretory cells. This is accompanied by precocious vitellogenic growth of oocytes in the subadult frogs

Members of opposite sex mutually regulate gonadal recrudescence in the lizard Calotes versicolor (Agamidae)

Adult males and females of the seasonally breeding lizard Calotes versicolor were subjected to various social situations under semi-natural conditions to explain the role of socio-sexual factors in gonadal recrudescence. They were grouped as: (i) males and females, (ii) males and females separated by a wire mesh, (iii) same sex groups of males or females, (iv) castrated males with intact females and (v) ovariectomized (OvX) females with intact males from postbreeding to breeding phase. Specimens collected from the wild during breeding season served as the control group. Plasma sex steroid levels (testosterone in male and 17β-estradiol in female), spermatogenetic activity and vitellogenesis were the criteria to judge gonadal recrudescence. In intact males and females that were kept together, gonadal recrudescence and plasma sex steroids levels were comparable to those in wild-caught individuals. Gonadal recrudescence was at its least in all male and all female groups, and plasma sex steroids were at basal levels. Association with OvX females initiated testicular recrudescence but spermatogenetic activity progressed only up to the spermatid stage while males separated from females by wire mesh showed spermatogenetic activity for a shorter period. Females grouped with castrated males and those separated from males by wire mesh produced vitellogenic follicles. However, the total number and diameter of vitellogenic follicles, and plasma estradiol levels were lower than in the females grouped with intact males. The findings indicate that association with members of the opposite sex with progressively rising titers of sex steroids is crucial in both initiating and sustaining gonadal recrudescence in the lizard. Thus, members of the opposite sex mutually regulate gonadal recrudescence in the C. versicolor