Ovarian activity during the annual reproductive cycle and nesting cycle of a wild avian species, the pied myna (Sturnus contra contra)

1987 ◽  
Vol 65 (4) ◽  
pp. 958-966
Author(s):  
S. K. Gupta ◽  
B. R. Maiti
Keyword(s):  
Reproductive Cycle ◽  
Gland Cell ◽  
Cell Mass ◽  
Egg Laying ◽  
Nest Building ◽  
Ovarian Activity ◽  
Annual Reproductive Cycle ◽  
Ovarian Weight ◽  
Gland Cells ◽  
Thecal Gland

Ovarian activity was studied during the annual reproductive cycle and nesting cycle in the Indian pied myna (Sturnus contra contra). The investigation was carried out on the basis of gravimetric, histological (gross and quantitative), and histochemical (3β-hydroxysteroid dehydrogenase and lipids) studies. In the ovary of the pied myna, four types of healthy follicles (primordial, small developing, large developing, and yolky) were recognized; the stroma showed gland cells. Steroidogenic activity was marked in the theca and granulosa of the follicles, and it altered with the growth of the follicles. The probable source of stromal gland cells is discussed. The ovarian activity changed over the course of the year with four distinct phases, viz., progressive (February to April), breeding (May), regression (June to July), and nonbreeding (August to January) phases. Ovarian weight, largest follicular diameter, populations of larger follicles, and thecal gland cell mass increased gradually from February through April, became maximal in May, decreased in June and July, and became minimal during August through January. Yolky follicles developed only in May. Stromal gland cell mass was abundant in March, decreased from April to June, was almost absent from July to September, reappeared in October, and gradually increased afterwards. Steroidogenic activity of the thecal and stromal gland cells also changed with the annual ovarian cycle; it was absent during July through September and reappeared in October. The granulosa cells showed steroid activity only in May. During the nesting cycle, ovarian activity increased rapidly from early nest-building to egg-laying periods and declined during incubation and nestling periods; this was evident from changes in ovarian weight, largest follicular diameter, thecal gland mass, and populations of larger follicles. Yolky follicles were seen during late nest-building, egg-laying, and incubation periods. Stromal gland cell mass decreased gradually during the nesting cycle. 3β-Hydroxysteroid dehydogenase activity was maximal in the nest-building period.

Hormonal and Experiential Factors Influencing the Nestbox Oriented Behaviour of Budgerigars (Melopsittacus Undulatus)

Behaviour ◽  
1969 ◽  
Vol 35 (1-2) ◽  
pp. 1-25 ◽  
Author(s):  
Barbara F. Brockway
Keyword(s):  
Prior Experience ◽  
Ovarian Follicle ◽  
Physiological State ◽  
Gonadal Hormones ◽  
Egg Laying ◽  
Nest Building ◽  
Ovarian Activity ◽  
Male Courtship ◽  
Opposite Sex ◽  
Males And Females

AbstractOther workers have shown that gonadal hormones can stimulate avian nest building and that there are species differences concerning the identity of the efficacious hormones. Nest building may be stimulated by estrogenic but not by androgenic material in one species. In another species, the converse is true. Budgerigars do not build nests. Their eggs are laid in tree-cavities. The female performs an easily quantified behaviour that is oriented to her prospective egg-laying site (a nestbox in the laboratory). This nestbox-oriented behaviour (NBOB) consists of remaining within the nestbox for various intervals throughout the day. This occurs daily, and she spends progressively more time within the nestbox as the day of initial oviposition approaches. Thus, NBOB is temporally and situationally related to nest building. A male rarely enters a nestbox unless he is engaging in courtship activities oriented to his mate. This report concerns laboratory studies that were conducted to determine: (1) the effects of different quantities of exogenous testosterone, estradiol and progesterone upon the NBOB of male and female budgerigars when they were individually-caged and unable to see or to hear members of the opposite sex, and (2) the effects of prior breeding experience(s) upon hormonally-induced NBOB. Four experiental types were studied: (V) virgins of either sex which, since fledging, had been visually isolated from the opposite sex and nestboxes; (Ex) males and females which had participated in at least one successful breeding cycle prior to this study; (V1) virgin females which were induced to perform NBOB but to maintain undeveloped ovaries; and (V2) virgin females which were induced to undergo full ovarian development and oviposition in the absence of nestboxes. Both intact and castrated males were studied. Ovarian hormones were given only to castrated males. No ovariectomized females were studied. Birds were injected thrice weekly and observed for 3 weeks. 1) Sexual identity and hormonal factors. Estradiol with or without progesterone stimulated NBOB by V and Ex males and females. The presence or absense of testicular androgens did not induce any male to perform NBOB. Larger (1.0 mg) quantities of testosterone induced females to perform NBOB, but such NBOB was atypically erratic. Testosterone-induced NBOB by females may have been a more direct manifestation of a testosterone-increased ovarian activity; however, the oviducts and ovaries of females receiving either 0.5 mg of 1.0 mg quantities of testosterone were not significantly heavier or larger than those of controls receiving only oil. Progesterone, alone, was just as ineffective as was the oil placebo: neither promoted any significant NBOB by males or females. These findings suggest that NBOB and nest building are not only related in temporal and situational ways, but share a common endocrinological denominator as well. Since NBOB appears to be primarily influenced by increased plasma levels of estrogenic material rather than by decreased levels of androgenic material, the NBOB of burgerigars is similar to the nest building of canaries and ring doves and diametrical to the androgen-stimulated nest building of black-crowned night herons. Estradiol with or without progesterone prompted females but not males to perform advanced phases of NBOB. Also females performed many phases of NBOB sooner than did males. Thus, males seem to be (genetically) less responsive to hormonal stimuli prompting NBOB than are females. 2) Experiential factors. In general, V birds of both sexes began to perform each phase of NBOB later and spent less time in nestbox occupation than did Ex birds receiving identical treatments. A previous study showed that Ex females, stimulated by either visual or vocal male courtship displays performed NBOB sooner than did V females. This prompted me to compare the ovarian follicle sizes and oviductal weights between Ex and V females receiving identical treatments and to examine the hormonally induced NBOB of V1 and V2 females. Since there were no significant differences in the ovarian and oviductal measurements between V and Ex females receiving identical injections, the differential response in the NBOB of V and Ex females does not seem to be solely due to a difference in the development of their reproductive tracts. Accordingly, we cannot say that male courtship more readily promotes NBOB with Ex than with V females because V females require more male stimulation in order to attain a given endogenous hormonal level or physiological state than do Ex females. Indeed prior experience may affect neural thresholds for response to given endogenous hormonal states without altering the response of reproductive organs. Perhaps Ex females are more readily induced to perform NBOB due to some factor involved in previous NBOB or a general familiarity with nestboxes. Data on V1 and V2 females supports this latter hypothesis. The onsets of each phase of NBOB and the amount of nestbox occupation were both potentiated by prior cxperience(s) concerning nestboxes. Prior experience(s) concerning heterosexual interactions or full ovarian activity and oviposition did not significantly affect hormonally induced NBOB.

scholarly journals The annual reproductive cycle of the snail Megalobulimus abbreviatus (Bequaert, 1948) (Gastropoda, Pulmonata)

2005 ◽  
Vol 65 (3) ◽  
pp. 459-467 ◽  
Author(s):  
A. C. M. Horn ◽  
A. Achaval ◽  
D. M. Zancan
Keyword(s):  
Breeding Season ◽  
Reproductive Cycle ◽  
Reproductive System ◽  
Morphological Changes ◽  
Reproductive Organ ◽  
Early Summer ◽  
Egg Laying ◽  
Annual Reproductive Cycle ◽  
Organ Weights ◽  
Maturation Index

Morphological changes in the sexual organs of the pulmonates were observed throughout a year and correlated with reproductive-cycle periods. Reproductive-organ weights of the snail Megalobulimus abbreviatus were recorded seasonally and gonad sections were analyzed morphologically. The weights were used to obtain the organosomatic index. Mean oocytic diameter and oocytic maturation index were based on gonad sections. It was concluded that M. abbreviatus is an iteroparous snail whose annual reproductive cycle is characterized by mating and egg laying throughout spring and early summer, and also by reproductive system preparation, occurring over the remainder of the summer until the end of winter, for a new breeding season.

Elevated nest predation risk promotes offspring size variation in birds with prolonged parental care.

2019 ◽  
Author(s):  
Gretchen F. Wagner ◽  
Emeline Mourocq ◽  
Michael Griesser
Keyword(s):  
Predation Risk ◽  
Reproductive Cycle ◽  
Perceived Risk ◽  
Nest Predation ◽  
Bird Species ◽  
Size Variation ◽  
Egg Laying ◽  
Offspring Size ◽  
Natural Predation ◽  
Risk Spreading

Predation of offspring is the main cause of reproductive failure in many species, and the mere fear of offspring predation shapes reproductive strategies. Yet, natural predation risk is ubiquitously variable and can be unpredictable. Consequently, the perceived prospect of predation early in a reproductive cycle may not reflect the actual risk to ensuing offspring. An increased variance in investment across offspring has been linked to breeding in unpredictable environments in several taxa, but has so far been overlooked as a maternal response to temporal variation in predation risk. Here, we experimentally increased the perceived risk of nest predation prior to egg-laying in seven bird species. Species with prolonged parent-offspring associations increased their intra-brood variation in egg, and subsequently offspring, size. High risk to offspring early in a reproductive cycle can favour a risk-spreading strategy particularly in species with the greatest opportunity to even out offspring quality after fledging.

Mechanisms underlying pituitary microvascular remodelling in thoroughbred horses during the annual reproductive cycle

2014 ◽  
Author(s):  
Angus Yeomans ◽  
Nichol Thompson ◽  
Jennifer Castle-Miller ◽  
David O Bates ◽  
Domingo Tortonese
Keyword(s):  
Reproductive Cycle ◽  
Annual Reproductive Cycle ◽  
Thoroughbred Horses

scholarly journals Proliferative and Apoptotic Pathways in the Testis of Quail Coturnix coturnix during the Seasonal Reproductive Cycle

Animals ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 1729
Author(s):  
Sara Falvo ◽  
Luigi Rosati ◽  
Maria Maddalena Di Fiore ◽  
Federica Di Giacomo Russo ◽  
Gabriella Chieffi Baccari ◽  
...  
Keyword(s):  
Reproductive Cycle ◽  
Second Messengers ◽  
Reproductive Period ◽  
Annual Reproductive Cycle ◽  
Coturnix Coturnix ◽  
Immunohistochemistry Analysis ◽  
17Β Estradiol ◽  
Apoptotic Pathways ◽  
Camp And Cgmp ◽  
Activation Phase

The quail Coturnix coturnix is a seasonal breeding species, with the annual reproductive cycle of its testes comprising an activation phase and a regression phase. Our previous results have proven that the testicular levels of both 17β-estradiol (E2) and androgens are higher during the reproductive period compared to the non-reproductive period, which led us to hypothesize that estrogens and androgens may act synergistically to initiate spermatogenesis. The present study was, therefore, aimed to investigate the estrogen responsive system in quail testis in relation to the reproduction seasonality, with a focus on the molecular pathways elicited in both active and regressive quail testes. Western blotting and immunohistochemistry analysis revealed that the expression of ERα, which is the predominant form of estrogen receptors in quail testis, was correlated with E2 concentration, suggesting that increased levels of E2-induced ERα could play a key role in the resumption of spermatogenesis during the reproductive period, when both PCNA and SYCP3, the mitotic and meiotic markers, respectively, were also increased. In the reproductive period we also found the activation of the ERK1/2 and Akt-1 kinase pathways and an increase in second messengers cAMP and cGMP levels. In the non-reproductive phase, when the E2/ERα levels were low, the inactivation of ERK1/2 and Akt-1 pathways favored apoptotic events due to an increase in the levels of Bax and cytochrome C, with a consequent regression of the gonad.

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