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 of Rana temporalis were studied in a 2 4 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.

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 17b-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.

The ontogeny of kin recognition in tadpoles of the toad Bufo 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 in B. melanostictus unlike in some other anurans.

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 subadult Rana 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.

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 frog Rana 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 guppies ad 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 (> 1400 μm) 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 of Rana 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/100 g 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.

Effect of synthetic nonapeptide (Thr-Cys-Ser-Val-Ser-Glu-Trp-Gly-Ile) on ovarian follicular development in the bull frog Rana tigrina (Daud).

Effect of synthetic nonapeptide (Thr-Cys-Ser-Val-Ser-Glu-Trp-Gly-Ile) representing the amino acid sequence 86-94 of human seminal plasma was studied on the ovarian follicular growth in the bullfrog R. tigrina during preparatory phase of reproductive cycle. Daily (except on Sundays) injections of 10 micrograms nonapeptide for one month caused a significant increase in ovarian weight and number of second growth phase (SGP) or vitellogenic oocytes. The results suggest that the nonapeptide is biologically active in amphibians also.

Effect of (d-Ala6) LHRH on hypophyseal gonadotrophs and ovary of adult frog, Rana tigrina (Daud.) during post-breeding regression phase.

Effects of synthetic luteinizing hormone-releasing hormone (LHRH, 1.5 micrograms) agonist on pituitary and ovary were studied in R. tigrina during November, the post-breeding regression phase. Injections (ip) were given 6 days a week for 30 days and frogs were sacrificed on day 31. Pituitary sections were stained with AB-PAS-OG. The staining intensity, cytoplasmic granulation and cell, nuclear and cytoplasmic areas of hypophyseal gonadotrophs (B2 cells) increased (P < 0.05) following LHRH administration. In controls, the B2 cells were small and faintly stained. LHRH treatment significantly increased ovarian weight over controls due to recruitment of medium sized second growth phase oocytes (MSGP) from the first growth phase (FGP) oocytes. Nearly 50% of oocytes from the FGP oocyte pool were recruited to SGP. Control frog ovaries lacked SGP oocytes. The results demonstrate that both ovary and pituitary of R. tigrina remain responsive to gonadotrophic and GnRH stimulation respectively during the post breeding regression phase.

Effect of thyroxine, prolactin and adrenalin on the gravid ovaries of the frog Rana cyanophlyctis (Schn.).

The effects of thyroxine, prolactin and adrenalin on the gravid ovaries of R. cyanophlyctis were studied during late prebreeding period when vitellogenic growth of oocytes is complete or near completion. Specified doses of hormones were injected (ip) six days a week for one month. They were fed guppies ad libitum daily 6 days a week. Administration of 2 or 5 micrograms eltroxine (synthetic thyroxine) had no effect on ovaries or oviducts. Whereas, higher doses 8, 12 and 16 micrograms thyroxine caused significant (P < 0.05) decrease in the per cent weight of ovaries and oviducts. The mean diameter of the largest oocyte was also reduced significantly compared to the controls. There was an increase in the atresia of vitellogenic oocytes. Treatment with 100 micrograms prolactin also caused reduction in the per cent weight of ovaries and oviducts. However, mean diameter of the largest oocyte did not change significantly. Follicular atresia increased only moderately. Injection of 180 micrograms adrenalin bitartrate caused drastic decrease (P < 0.05) in the per cent weight of ovaries and oviducts and mean diameter of the largest oocyte. Many yolky follicles became atretic. The findings suggest that increase in the levels of thyroxine (beyond a certain limit), prolactin and adrenalin around the breeding period decrease the fecundity of the frog by inducing atresia of yolky oocytes. We conclude that the above hormones in excess quantities act as negative modifiers of ovarian activity in R. cyanophlyctis.

Kinetics of spermatogenesis in megachiropteran bat, Rousettus leschenaulti (Desmarset): seminiferous epithelial cycle, frequency of stages, spermatogonial renewal and germ cell degeneration.

The paper describes in detail the cytomorphology of different types of germ cells, the 10 typical cellular associations or stages of the cycle of seminiferous epithelium (CSE), frequency of appearance of these stages, pattern of spermatogonial stem cell renewal and per cent degeneration of various germ cells in R. leschenaulti. Of the 14 steps of spermiogenesis (stained with PAS-haematoxylin) the first 10 were associated with the stages I-X, whereas, the remaining were found in association with one of the first six stages. The frequency of appearance of the various stages ranged from 3.84% (stage V) to 19.84% (stage I). These observations indicate that stage V is of shortest duration and stage I is of the longest duration in the bat. Five types of spermatogonia (A1, A2, A3, In and B) were identified based on their shape, size and nuclear morphology. Type A spermatogonia are oval with a large nucleus containing 1 or 2 nucleoli. The chromatin showed progressive condensation from A1 to A3 so that the latter appeared darkest among all the A type spermatogonia. The In type derived from A3 are smaller but appear darker than A3 due to heterochromatin crusts along the inner border of the nucleus. The B type spermatogonia derived from In are round and possess single nucleolus. The B type spermatogonia divided mitotically before entering meiosis or the actual production of the primary spermatocytes. The various spermatogonia divided mitotically at fixed stages of the cycle giving rise to their next generations.(ABSTRACT TRUNCATED AT 250 WORDS)

Role of temperature in regulation of ovarian cycle in bull frog Rana tigerina.

Effect of temperature on the ovarian cycle was studied in R. tigerina by exposing them to (1) constant low (22 degrees C) temperature during preparatory (active vitellogenic growth) phase (March-May) when the mean ambient temperature ranged from 26 degrees-28 degrees C and (2) to constant high (30 degrees +/- 1 degrees C) temperature during postbreeding regression phase (August-November) when the mean ambient temperature ranged from 22 degrees-26 degrees C. The ovaries of initial controls (biopsy samples taken prior to the commencement of the experiment) in March contained only first growth phase (FGP) oocytes with a maximum size range of 361-480 microns in diameter. In the frogs exposed to constant low temperature for 2 months, only 7% of FGP oocytes were recruited to second growth phase (SGP) with a mean largest diameter of 631 microns compared to 31% large SGP oocytes with a mean diameter of 1114 microns in the frogs collected from natural fields. The number of atretic follicles (AF) was lower and fat body weights were significantly higher in low temperature exposed frogs. The exposure of the frogs to constant high temperature during postbreeding months caused an increase in the mean diameter and number of large FGP oocytes, numerical increase in AF and decrease in fat body weights over corresponding controls maintained at room temperature. The pituitary gonadotrophs of these frogs showed stimulatory changes such as increase in cell size and appearance of secretory granules in the cytoplasm. The results suggest that in R. tigerina high temperature stimulates oocyte growth while low temperature retards it.(ABSTRACT TRUNCATED AT 250 WORDS)