Sex Accessories Morphology and Functions during the Seasonal Testicular Cycle of a Subtropical Wild Avian Species, the Yellow-Throated Sparrow Petronia xanthocollis Burton

Annual changes in the male sex accessories (tubuli recti, rete testis, vasa efferentia, epididymis, vas deferens and seminal glomus) were studied during the annual testicular cycle of the yellow-throated sparrow ( Petronia xanthocollis Burton). All the segments of genital tract and the seminal glomus became enlarged during the progressive phase (January to March), were maximally enlarged during breeding (April), began to decrease during regression (May and June) and became maximally regressed during the nonbreeding phase (July to December). But the sialic acid level of the seminal glomus increased to maximum already during the progressive phase, remained high during breeding and declined subsequently. The findings suggest that the male sex accessories functions vary distinctly with the annual testicular cycle presumably due to alterations in the testicular androgen production in the yellow-throated sparrow.     

Cytologic variation in the pineal organ of roseringed parakeets (Psittacula krameri) with respect to artificial photoperiods and annual cyclicity in testicular functions

Abstract

Adult male roseringed parakeets were transferred to 16L: 8D (LP), or 8L: 16D (SP) for 45 or 90 days on four particular dates corresponding to the different phases of an annual testicular cycle and the cytological responses of the pineal were studied comparing them with the features in respective natural photoperiodic (NP) birds. Different cytological characteristics including the values of nuclear diameter in pinealocytes indicated that LP for 45 days during the pre‐breeding phase and for 90 days during each phase resulted in an increased pineal activity, while SP for 45 and 90 days induced inhibitory responses of the pineal during each, but not the progressive phase of the annual testicular cycle. During the latter phase, none of the artificial photoperiodic schedules, other than LP for 90 days, influenced the cytological features of the pineal. The results suggest that the photosensitivity of the pineal in these parakeets varies in relation to the testicular functions in an annual testicular cycle, but the seasonal pattern of photoperiodic response of the pineal and that of the previously studied testes in the same birds does not seem to be identical.     

The Pineal Gland,but Not Melatonin,Is Associated with the Termination of Seasonal Testicular Activity in an Annual Reproductive Cycle in Roseringed Parakeet Psittacula krameri

The role of the pineal gland and its hormone melatonin in the regulation of annual testicular events was investigated for the first time in a psittacine bird, the roseringed parakeet (Psittacula krameri). Accordingly, the testicular responsiveness of the birds was evaluated following surgical pinealectomy with or without the exogenous administration of melatonin and the experimental manipulations of the endogenous levels of melatonin through exposing the birds to continuous illumination. An identical schedule was followed during the four reproductive phases, each characterizing a distinct testicular status in the annual cycle, namely, the phases of gametogenic quiescence (preparatory phase), seasonal recovery of gametogenesis (progressive phase), seasonal initiation of sperm formation (pre‐breeding phase), and peak gametogenic activity (breeding phase). In each reproductive phase, the birds were subjected to various experimental conditions, and the effects were studied comparing the testicular conditions in the respective control birds. The study included germ cell profiles of the seminiferous tubules, the activities of steroidogenic enzymes 17β‐hydroxysteroid dehydrogenase (17β‐HSD), and Δ⁵3β‐hydroxysteroid dehydrogenase (Δ⁵3β‐ HSD) in the testis, and the serum levels of testosterone and melatonin. An analysis of the data reveals that the pineal gland and its hormone melatonin may play an inhibitory role in the development of the testis until the attainment of the seasonal peak in the annual reproductive cycle. However, in all probability, the termination of the seasonal activity of the testis or the initiation of testicular regression in the annual reproductive cycle appears to be the function of the pineal gland, but not of melatonin.     

Melatonin Does Not Modulate Testicular Responsiveness to Altered Photoperiods. A Study During Different Phases of the Annual Gonadal Cycle in Roseringed Parakeets (Psittacula krameri)

The roseringed parakeet has been shown to exhibit a variable testicular responsiveness to both altered photoperiodic regimens and to treatment with melatonin during different phases of the annual gonadal cycle. Adult male roseringed parakeets were held under either natural photoperiods (NP), or long photoperiods (LP; 16L 8D), or short photoperiods (SP; 8L 16D) for a total period of 90 days. From day 46 onward, half of the total birds in each group were administered with the vehicle of melatonin, and the other birds were injected daily in the afternoon with melatonin (25 µg/ 100 g body wt.) till the end of the experiment. An identical experimental schedule was followed during the four different (preparatory, progressive, pre-breeding, and breeding) phases of the annual testicular cycle. The testicular activities in various bird groups were evaluated by volumetric, gravimetric, histometric and karyometric measurements, and by quantitative histological studies. The findings revealed that exogenous melatonin may exert either a suppressive influence or none at all on the testicular functions in relation to the photoperiodic schedule as well as to the reproductive phase of the concerned bird, but in no case modulates gonadal responsiveness to artificially altered photoperiods.     

Melatonin Does Not Modulate Testicular Responsiveness to Altered Photoperiods. A Study During Different Phases of the Annual Gonadal Cycle in Roseringed Parakeets (Psittacula krameri)

The roseringed parakeet has been shown to exhibit a variable testicular responsiveness to both altered photoperiodic regimens and to treatment with melatonin during different phases of the annual gonadal cycle. Adult male roseringed parakeets were held under either natural photoperiods (NP), or long photoperiods (LP; 16L 8D), or short photoperiods (SP; 8L 16D) for a total period of 90 days. From day 46 onward, half of the total birds in each group were administered with the vehicle of melatonin, and the other birds were injected daily in the afternoon with melatonin (25 µg/ 100 g body wt.) till the end of the experiment. An identical experimental schedule was followed during the four different (preparatory, progressive, pre-breeding, and breeding) phases of the annual testicular cycle. The testicular activities in various bird groups were evaluated by volumetric, gravimetric, histometric and karyometric measurements, and by quantitative histological studies. The findings revealed that exogenous melatonin may exert either a suppressive influence or none at all on the testicular functions in relation to the photoperiodic schedule as well as to the reproductive phase of the concerned bird, but in no case modulates gonadal responsiveness to artificially altered photoperiods.     

The pineal gland, but not melatonin, is associated with the termination of seasonal testicular activity in an annual reproductive cycle in roseringed parakeet Psittacula krameri

The role of the pineal gland and its hormone melatonin in the regulation of annual testicular events was investigated for the first time in a psittacine bird, the roseringed parakeet (Psittacula krameri). Accordingly, the testicular responsiveness of the birds was evaluated following surgical pinealectomy with or without the exogenous administration of melatonin and the experimental manipulations of the endogenous levels of melatonin through exposing the birds to continuous illumination. An identical schedule was followed during the four reproductive phases, each characterizing a distinct testicular status in the annual cycle, namely, the phases of gametogenic quiescence (preparatory phase), seasonal recovery of gametogenesis (progressive phase), seasonal initiation of sperm formation (pre-breeding phase), and peak gametogenic activity (breeding phase). In each reproductive phase, the birds were subjected to various experimental conditions, and the effects were studied comparing the testicular conditions in the respective control birds. The study included germ cell profiles of the seminiferous tubules, the activities of steroidogenic enzymes 17β-hydroxysteroid dehydrogenase (17β-HSD), and Δ⁵3β-hydroxysteroid dehydrogenase (Δ⁵3β- HSD) in the testis, and the serum levels of testosterone and melatonin. An analysis of the data reveals that the pineal gland and its hormone melatonin may play an inhibitory role in the development of the testis until the attainment of the seasonal peak in the annual reproductive cycle. However, in all probability, the termination of the seasonal activity of the testis or the initiation of testicular regression in the annual reproductive cycle appears to be the function of the pineal gland, but not of melatonin.     

Oviductal Function during the Annual Ovarian Cycle of a Wild Avian Species, the Tree Pie Dendrocitta vagabunda

The present investigation was carried out on oviductal activity during the annual ovarian cycle of the Indian tree pie ( Dendrocitta vagabunda ). The oviductal activity was evaluated by weight, length, histology (gross and quantitative) and peroxidase, acid phosphatase, alkaline phosphatase, sialic acid, glycogen, RNA and protein concentrations of different regions of the oviduct. All these values w ere low during the nonbreeding phase (August to January), increased during the progressive phase (February to March), became maximum during breeding (April to May) and decreased in the regression phase (June to July). The functional change of the oviduct is suggested to be due to fluctuation of ovarian steroid activity in this avian species.     

Oviductal Function during the Annual Ovarian Cycle of a Wild Avian Species,the Tree Pie Dendrocitta vagabunda

The present investigation was carried out on oviductal activity during the annual ovarian cycle of the Indian tree pie (Dendrocitta vagabunda). The oviductal activity was evaluated by weight, length, histology (gross and quantitative) and peroxidase, acid phosphatase, alkaline phosphatase, sialic acid, glycogen, RNA and protein concentrations of different regions of the oviduct. All these values w ere low during the nonbreeding phase (August to January), increased during the progressive phase (February to March), became maximum during breeding (April to May) and decreased in the regression phase (June to July). The functional change of the oviduct is suggested to be due to fluctuation of ovarian steroid activity in this avian species.     

Annual changes in testicular development and plasma sex steroids in the captive male dojo loach <Emphasis Type="Italic">Misgurnus anguillicaudatus</Emphasis>

Testicular development in the captive male dojo loach Misgurnus anguillicaudatus was examined monthly in relation to the levels of plasma sex steroids [testosterone (T), 11-ketotestostrone (11-KT), and 17,20β-dihydroxy-4-pregnen-3-one (DHP)]. On the basis of testicular histology, the annual gonadal cycle was found to be divisible into 3 periods: the recovery and proliferation period, which mainly consists of early spermatogenic testis from August to November (reproductive phase I); the preparation period for the next spawning period, which mainly consists of late spermatogenic testis from December to April (reproductive phase II); and the mature period, characterized by a high proportion of mature testis from May to July (reproductive phase III). Individual variability in testicular development was high, and continuous spermatogenesis was observed throughout the year. High levels of plasma T, 11-KT, and DHP were observed during reproductive phase III. 11-KT began to increase in February, while T was present at low levels in reproductive phase II. These results suggest that the physiologically active season of testis development for breeding in the dojo loach is from May to July, although spermatogenesis occurs throughout the year.     

Structure of the ellipsoid sheath in the spleen of the armadillo (Dasypus novemcinctus). A light and electron microscopic study

A seasonal study of the seminal vesicles in relation to that of the testes had been conducted in the catfish, H. fossilis. The annual reproductive cycle of the catfish has been divided into (i) Preparatory period (February–April), (ii) Prespawning period (May–June), (iii) Spawning period (July–August) and (iv) Postspawning period (September–January). Testes exhibit initiation of spermatogenesis in the mid-preparatory period, but significant increase in weight of the testes accompanied by active spermatogenesis occurs during the prespawning period. In the spawning period, the testes are maximally enlarged and their seminiferous tubules are packed with spermatozoa. Following spawning, the testes gradually regress in the postspawning period. The seminal vesicles show initiation of secretory activity during the preparatory period but their recrudescence lags behind that of the testes by about a month. The seminal vesicles attain maximum weight and secretory activity during the spawning period. Thereafter, the seminal vesicles regress precipitously and sooner than the testes. The histochemical and biochemical studies on the seminal vesicles indicate that the secretion contains mucoproteins, acid mucopolysaccharides, primary proteoses, besides traces of phospholipids and native proteins.     

Immunohistochemical evidence for 11beta-hydroxylase (P45011beta) and androgen production in the gonad during sex differentiation and in adults in the protandrous anemonefish Amphiprion clarkii

To obtain basic information on the endocrine mechanisms underlying sex change in the protandrous anemonefish Amphiprion clarkii, we examined the immunolocalization of the steroidogenic enzyme cytochrome 11beta-hydroxylase (P45011beta), which is involved in 11-ketotestosterone (11-KT) production, and analyzed the ability of gonads to produce steroid hormones throughout the sex differentiation process and at the breeding stage. Immunopositive reactions against P45011beta appeared in sexually undifferentiated gonads at 30 days post hatching (dph). The number of immunopositive cells continued to increase during ovarian differentiation (from 60 to 180 dph) and throughout the formation of ambisexual gonads with both ovarian and testicular tissue until 270 dph. In the male phase, strongly immunopositive cells were observed in the cellular interstices of both testicular and ovarian tissues. P45011beta was localized only in the theca cells enclosing developed oocytes in the female phase. In-vitro 11-KT production in the gonads gradually increased with testicular differentiation (before, during, and after differentiation). Production of 11-KT in the gonads was higher in the male phase than during testicular differentiation or in the female phase. Our results suggest that androgen is involved in testicular differentiation during sex differentiation and spermatogenesis.     

A possible role of prostaglandin E2 in reproduction of the male water frog, Rana esculenta. In vivo and in vitro studies.

Plasma prostaglandin E2 (PGE2), prostaglandin F2 alpha (PGF2 alpha), androgens and estradiol-17 beta were measured in the male water frog, Rana esculenta, during the annual sexual cycle. In vivo experiments were carried out to study the effects of PGE2 and PGF2 alpha on plasma sex steroids during the following periods: prereproduction (April), reproduction (May), postreproduction (June) and recovery (October). In the same months, in vitro experiments were performed to evaluate the effects of these two prostaglandins (PGs) on testicular release of sex steroids. The PGE2 plasma levels peaked in April. PGE2 treatment in vivo increased androgens in April and October, while PGF2 alpha increased estradiol-17 beta in June and October. In in vitro experiments, PGE2 increased androgens in April, while PGF2 alpha increased estradiol-17 beta in October. These results suggest that PGE2 could induce the breeding activity, probably through androgens synthesis. PGF2 alpha could interrupt the breeding, through estradiol-17 beta secretion.     

Effects of glucocorticoids on plasma levels of thyroid hormones (T4 and T3) and testicular activity in catfish, Clarias gariepinus during different phases of annual breeding cycle

Effects of short-term administration of corticosterone and cortisol on plasma levels of thyroid hormones, gonado-somatic index and testicular histology have been reported in catfish, Clarias gariepinus during different phases of its breeding cycle. Corticosterone administration had no significant effect on plasma levels of T4, T3 and T3/T4 ratio, irrespective of doses and phases of breeding cycle. However, 5 microg dose of cortisol significantly increased plasma levels of T3 and the T3/T4 ratio during quiescent and regressive phases, while it significantly decreased plasma levels of T4 during progressive phase. During breeding phase, 2 microg and 5 microg doses of cortisol significantly decreased plasma levels of T4 and T3, respectively, while 5 microg dose of cortisol alone reduced T3/T4 ratio. Irrespective of phases of annual breeding cycle and doses, short-term administration of corticosterone and cortisol had no significant effect either on GSI or testicular histology. These findings suggest that corticosterone is ineffective in stimulating plasma levels of thyroid hormones, while cortisol, depending on dose and phase/season, may differentially increase, decrease or have no effect on plasma levels of thyroid hormones in C. gariepinus.     

Importance of photoperiods in determining temporal pattern of annual testicular events in rose-ringed parakeet (Psittacula krameri).

Male rose-ringed parakeets (Psittacula krameri) were transferred to a long photoperiod (LP; LD 16:8) or a short photoperiod (SP; LD 8:16) for 45 or 90 days on four dates corresponding to the beginnings of different reproductive phases in an annual testicular cycle, and testicular responsiveness was evaluated by comparison with the testicular volume, weight, seminiferous tubular diameter, and germ cell profiles of birds in a natural photoperiod (NP). Exposure of birds to LP during the progressive phase (November) led to precocious maturation of testes after 45 days, but induced regression at 90 days. After showing retarded gametogenic functions at 45 days, parallel (November) SP birds exhibited an accelerated rate of germ cell formation at day 90. During the prebreeding phase (January), there were no remarkable differences in any features of testes among NP. LP, and SP birds at 45 days, but gonadal involution in LP parakeets and active spermatogenesis in SP birds occurred after 90 days. The testes did not show any response to LP or SP for 45 and 90 days when the birds were transferred to altered photoperiods during the breeding (March) and preparatory (June) phases, indicating that the parakeets were photorefractory for at least 6 months (March through September). The results also suggest that initiation and termination of seasonal gametogenic activity in parakeets are possibly functions of endogenous rhythmicity or extraphotoperiodic environmental factors. Duration of light may have certain influences on the attainment of annual peak in spermatogenesis, but in all probability the species has a low photoperiod threshold for induction of testicular growth.     

Relation between the Adrenals and Thyroid and their Hormones and the Testicular cycle of a Subtropical Avian Species

In order to understand the hormonal interactions throughout the reproductive phases (non-breeding, progressive, breeding and regressive) of a sub-tropical avian species, the male common myna (Acriodotheres tristis), hormones like epinephrine (E), norepinephrine (NE), corticosterone, tri-iodothyronine (T 3), thyroxine (T 4) and testosterone (along with testicular sialic acid) were quantitated. Histometry and histology of the testis and adrenal glands were also performed. It became evident that a parallel relationship exists between the reproductive phases of the common myna and levels of the hormones E, NE, corticosterone, T 3, T 4 and testosterone. Considering the ambient climatological conditions, it is suggested that primarily daylength and secondarily humidity control the gonadal cycle of this species.     

Relation between the Adrenals and Thyroid and their Hormones and the Testicular cycle of a Subtropical Avian Species

In order to understand the hormonal interactions throughout the reproductive phases (non-breeding, progressive, breeding and regressive) of a sub-tropical avian species, the male common myna ( Acriodotheres tristis ), hormones like epinephrine (E), norepinephrine (NE), corticosterone, tri-iodothyronine (T 3 ), thyroxine (T 4 ) and testosterone (along with testicular sialic acid) were quantitated. Histometry and histology of the testis and adrenal glands were also performed. It became evident that a parallel relationship exists between the reproductive phases of the common myna and levels of the hormones E, NE, corticosterone, T 3 , T 4 and testosterone. Considering the ambient climatological conditions, it is suggested that primarily daylength and secondarily humidity control the gonadal cycle of this species.     

Mating and role of seminal receptacles in the reproductive biology of the spider crab Maja squinado (Decapoda, Majidae)

The reproductive biology of the spider crab Maja squinado was analyzed based on monthly samples from an 18-month study carried out in Galicia (NW Spain) and laboratory experiments holding primiparous and multiparous females in captivity with and without males. The seminal receptacles of adult females were analyzed and their relationship with the presence and developmental stage of the eggs and the gonad maturity stage was determined. Gonad maturation in primiparous females began one or two months after the pubertal moult. Females having gonads in an advanced stage of development made their appearance in December and the first spawning took place in mid-winter or early spring. The percentage of ovigerous females from March to September was ∼75%. As the incubation period progressed, the ovaries became mature again in order to carry out the next spawning. Under experimental conditions the breeding cycle started earlier in multiparous females, during their second yearly cycle, than in primiparous ones. After mating, female spider crabs store sperm in seminal receptacles and this sperm is used in the fertilization of eggs immediately prior to spawning. The analyses of seminal receptacles consisted of the estimation of fullness and the number of differentiated sperm masses. The number of masses ranged between 0 and 6 in field samples (median for females with stored sperm=1) and was positively correlated with fullness. Differences in colour and volume of individual masses showed that, at least in some cases, females carried out successive matings with long intervals in between. This storage mechanism allowed females to fertilize successive broods without remating (as was also shown under experimental conditions). Juvenile females from shallow waters did not have developed seminal receptacles which indicated that mating was not possible until the onset of maturity. Postpubertal females in shallow waters (August to October), including animals participating in aggregations, always showed empty receptacles. The seasonality of receptacle fullness showed that mating involved hard-shelled females and occurred in deep water during the autumn migration from juvenile habitats or in the wintering habitats, during the last stages of gonad maturation (November to February). After fertilization ovigerous females continued to store sperm, but the volume was lower than in non-ovigerous females. Mating may occur in ovigerous females, particularly in the final period of incubation, because in females with broods almost ready to hatch, both new and older sperm masses were seen in the receptacles (distinguished by colour and size). The fullness of the receptacles decreased both in ovigerous and non-ovigerous females in the final phase of the annual breeding cycle (August–October), however, some sperm was still available. In the laboratory, mating was observed, and no courtship nor postcopulatory guarding was recorded. The analysis of receptacles from laboratory experiments indicated that primiparous and multiparous females showed differences in the seasonality of mating in the first phase of the breeding cycle (September–January), related to differences in the timing of gonad maturation and hatching. Mating occurred in the final stages of gonad maturation, a short time before hatching, and matings were detected in ovigerous females. Multiple matings were also evident, to a greater extent than in the field, probably due to the higher availability of males. Females underwent over four successive spawnings in the laboratory without having to recopulate, and the incubation lasted on the average from 40 to 58 days (∼18 and 16°C respectively) and the mean duration between hatching and the next spawning was 3.4 days. It is estimated that most females carry out three successive spawnings during the annual cycle.     

Testicular development and serum levels of gonadal steroids during the annual reproductive cycle of captive Japanese sardine

Gonad and blood samples were taken throughout the year from captive males of the Japanese sardine,Sardinops melanostictus, and changes in serum levels of gonadal steroids were examined in relation to the annual gonadal cycle. On the basis of testicular histology, the annual gonadal cycle was divisible into four periods: immature (July–September), spermatogenesis (October–December), spermiation (January–April), and post-spawning (May–June). The pattern of seasonal changes in the gonadosomatic index (GSI) was inversely correlated with that of water temperature, and reflected the degree of testicular maturity. The serum testosterone level was relatively low during spermatogenesis (2.2–2.5 ng/ml), rose markedly around the time of spermiation (7.7–24.6 ng/ml), and became low after spawning and during immature periods (0.6–0.7 ng/ml). The serum 17α,20β-dihydroxy-4-pregnen-3-one level was high in males with spermatogenic or spermiating testes (0.6–1.0 ng/ml), but became low (0.2 ng/ ml during the post-spawning period and was undetectable in immature fish. Although 11-ketotestosterone was detectable in some fish, the values obtained were thought to reflect cross-reactivity of the antiserum employed with testosterone. These findings are discussed in relation to male reproduction of the Japanese sardine and steroidal regulation of spermatogenesis and spermiation in other teleosts.     

Photoperiodic ovarian response in yellow-throated sparrow, Gymnorhis xanthocollis: involvement of circadian rhythm

The experiments aim to investigate the mechanism of photoperiodic time measurement during photoperiodic ovarian response of subtropical yellow-throated sparrow. Groups of the photosensitive female birds were exposed to various night-interruption cycles for a period of 35 days. These light-dark cycles consisted of a basic photophase of 6h and 1h photointerruption of the 18h dark phase in 24h cycle at different points. A control group was also placed under 7L/17D. Ovarian response was observed in the night-interruption cycles in which the photointerruption of dark phase was made 12h after the onset of basic photophase. The results are consistent with the Bünning hypothesis and indicate that an endogenous circadian rhythm is involved in photoperiodic time measurement during initiation of ovarian growth in this species.     

Seasonal effects of pinealectomy on testicular recrudescence and secretory activity of seminal vesicles in the catfish Heteropneustes fossilis (Bloch)

The effects of pinealectomy on testicular activity and secretory activity of seminal vesicles were examined in the catfish Heteropneustes fossilis under various combinations of photoperiod and temperature during different periods of the annual reproductive cycle. Pinealectomy had no effect on gonadal activity during the preparatory, prespawning and spawning periods of the reproductive cycle. However, during the postspawning period, under long (LD 14:10) or short (LD 9:15) photoperiod at 25° C or at gradually increasing ambient temperature, pinealectomy accelerated testicular recrudescence and secretory activity of the seminal vesicles. Nevertheless. during this period the presence of the pineal facilitated the recrudescence of testes and seminal vesicles in catfish exposed to continuous light (LL), continuous darkness (DD) and 12 hL:l2 hD (LD) at 25° C. These findings suggest that the role of the pineal in catfish reproduction is variable and depends upon the photoperiod and temperature regimes to which the fish are exposed, as well as on the time of the year and the state of the reproductive cycle. The results also suggest that the effects of pinealectomy in catfish are mediated through an influence on the hypothalamo-hypophyseal gonadal axis.