Seasonal Reproductive Cycle Research Articles

Quantifying the seasonal reproductive cycle in three species of Malagasy fruit bats with implications for pathogen and population dynamics.

Bats (order Chiroptera) are hosts for highly virulent zoonotic pathogens. Many bats demonstrate seasonally varying antiviral responses, including antibody responses which have been observed to peak during the nutritionally depleted dry-season and female gestation periods, suggesting some impact of resource deficits on bat virus immunity. Given the frequent overlap in these energetically demanding periods, it is likely that endocrinological changes associated with pregnancy might partially explain the aforementioned pattern in antibody dynamics. Regardless, we know little about the seasonality of reproduction in many fruit bat species, despite the importance of reproductive biology to informing conservation management (e.g. population viability) and disease dynamics. Here, we aimed to elucidate the reproductive biology of three species of endemic fruit bat native to the island of Madagascar: Pteropus rufus, Eidolon dupreanum, and Rousettus madagascarensis. To do so, we leveraged plasma samples collected in part with a longitudinal field study, from 2018 to 2020. We adapted three standard reproductive assays previously validated in humans to quantify seasonal changes in reproductive hormones for bats and applied a mixture model approach to determine hormone cutoffs for pregnancy. As expected, we found that pregnant females showed the highest levels of estradiol and progesterone and adult males the highest levels of testosterone. Additionally, female P. rufus and R. madagascariensis showed clear seasonality in reproduction with peaks in estradiol and progesterone in August and October, respectively. Seasonality was less clearly discernible in the female E. dupreanum and male data. In general, we found that the commercially available assays were successful in quantifying endocrinological hormones for bats; when paired with histological embryo sections or field data, these offer a powerful tool to elucidate bat reproductive calendars.

The annual ovarian cycle in Northern pit vipers (Bothrops atrox) using serum steroids and ultrasound of the female reproductive tract

Knowledge on hormonal regulation of reproductive cycles in viperid snakes is still incipient, especially when it comes to females and tropical species. There is an urgent need to understand the reproduction of venomous snakes to improve assisted reproduction techniques and optimize the maintenance of these animals in captivity. With this in mind, we monitored Northern pit viper females year-round throughout different seasons via serum levels of progesterone (P4) and estradiol (E2) in conjunction with ultrasound examinations. Ovarian follicles were classified according to their size and stage of vitellogenesis in F-I and F-II (non-vitellogenic phase) or in F-III and F-IV (vitellogenic phase). During autumn and winter, five adult males were rotated among these females for reproductive pairing, which resulted in 17 copulations and 2 pregnancies in the first year and 12 copulations and 5 pregnancies in the second year. Then, we assessed changes in P4 and E2 levels according to seasons, predominant ovarian structures and the presence of embryos or eggs in the oviduct. Our findings showed high levels of E2 when a greater number of vitellogenic follicles were detected, indicating a possible influence of E2 on vitellogenesis and higher levels of P4 whenever eggs and embryos were visualized in the oviduct, implying its role in maintaining pregnancy. Descriptive analysis of the vipers’ ovarian cycles revealed a greater number of vitellogenic follicles during winter, probably as a result of increases in E2; whereas pregnancies occurred predominantly in spring, under the influence of P4. The use of ultrasound images, as a minimally invasive methodology, associated with serum steroid levels has proven to be an efficient approach in the reproductive monitoring of Northern pit vipers in vivo. In addition, these data suggest that female pit vipers under human care display a seasonal reproductive cycle, despite earlier studies involving captive males of the species indicating a lack of seasonality in sperm production and quality.

Exploring the role of endogenous retroviruses in seasonal reproductive cycles: a case study of the ERV-V envelope gene in mink.

Endogenous retroviruses (ERVs), which originated from exogenous retroviral infections of germline cells millions of years ago and were inherited by subsequent generations as per Mendelian inheritance patterns, predominantly comprise non-protein-coding sequences due to the accumulation of mutations, insertions, deletions, and truncations. Nevertheless, recent studies have revealed that ERVs play a crucial role in diverse biological processes by encoding various proteins. In this study, we successfully identified an ERV envelope (env) gene in a mink species. A phylogenetic tree of mink ERV-V env and reference sequences was constructed using Bayesian methods and maximum-likelihood inference. Phylogenetic analyses indicated a significant degree of sequence conservation and positive selection within the env-surface open reading frame. Additionally, qRT-PCR revealed diverse patterns of mink ERV-V env expression in various tissues. The expression of mink ERV-V env gene in testicular tissue strongly correlated with the seasonal reproductive cycles of minks. Our study suggests that the ERV-V env gene in mink may have been repurposed for host functions.

The real subsumption of nature and cryopolitics: Temporal fixes in dairy farming in Southern Italy

Water buffaloes have a seasonal cycle of reproduction. Normally they tend to reproduce more when the daylight hours decrease. This seasonal reproduction also means that most of the buffalo calves would be born in autumn and winter in Italy where buffaloes are dairy animals, and milk production would be the highest in these seasons. However, consumer demand for the PDO (Protected designation of origin) mozzarella cheese is the highest in spring and summer. In order to deal with the imbalances between the seasonality of milk production and mozzarella consumption, and the strict regulations of the PDO cheese production, farmers and veterinarians resort to a temporal fix, and they regularly deseasonalise buffalo reproduction. However, there is an obvious discrepancy between the use of this and other fixes (cryotechnologies) generally associated with industrial agriculture, and the idea of traditional and sustainable food production. By engaging with relevant economic geography and political ecology literature, this paper investigates the temporal fixes in dairy farming and agri-food production through an in-depth empirical analysis of deseasonalisation, as a particular form of the real subsumption of nature, and cryopolitics in buffalo mozzarella cheese production in Southern Italy. The work presented in this article is based on multi-sited qualitative field research of buffalo farming and mozzarella cheese production in Campania region. This paper also has wider implications on how socio-ecological fixes shape ‘just-in-time’ animal agriculture and agri-food production.

Testosterone is closely related to Leydig cell activity, environmental factors, and androgen receptor distribution in adult male lizards of Liolaemus cuyanus (Reptilia: Liolaemidae) during the reproductive cycle.

Testosterone, the primary sex hormone in male lizards, is closely linked to Leydig cell activity (the cells where steroidogenesis occurs) throughout the reproductive cycle, but testosterone action is related to androgen receptors (ARs) distribution in the seminiferous epithelium. In temperate zones, environmental factors detected through the hypothalamic-pituitary-gonadal axis, downregulate plasma testosterone, resulting in a seasonal reproductive cycle. The aim of this work is to study plasma testosterone in adult male lizards of Liolaemus cuyanus, an oviparous species, throughout its reproductive cycle and its relationship with Leydig cell histology, TotalLeydigCell/ActiveLeydigCell (TLC/ALC) ratio, environmental factors (temperature, relative humidity and solar irradiation) and ARs distribution in seminiferous epithelium. Specimens (N = 27) were captured (October to March) in a semi-arid zone (Valle de Matagusanos, San Juan, Argentina) and grouped into three relevant reproductive periods: pre-reproductive (PrR), reproductive (R), and post-reproductive (PsR). Significant differences in plasma testosterone were found among these periods, highest during R than in PsR. A significant positive correlation between plasma testosterone and TLC/ALC ratio was also observed. Plasma testosterone has a significant positive correlation only with solar irradiation, but not with the other variables. In PrR and R, ARs distribution was cytoplasmic and nuclear, shifting to only cytoplasmic in PsR. These results highlight the close correspondence between plasma testosterone, Leydig cell histology and activity, environmental factors, and ARs distribution, resulting in a synchronization that allows males of L. cuyanus to coordinate their reproductive cycle with the most favorable environmental conditions, probably for mating and birth of offspring.

Seasonality of Reproduction in a Subtropical Free-Living Finch Amandava amandava: Plasticity of Adenohypophyseal Gonadotropes, Lactotropes, and Thyrotropes

Introduction: This study sought to decipher the mechanism of transitions between life-history stages in a seasonally reproducing subtropical finch, Amandava amandava delineating the plasticity of the gonadotropes (LH cells), lactotropes (PRL cells), and thyrotropes (TSH cells) in the pituitary gland including the pars tuberalis, with regard to the in situ expression, morphological characteristics, and alteration in the plasma levels of hormones. Methods: Immunohistochemistry of LH, PRL, TSH cells, morphometry and densitometry of expressed hormones (Image J software analysis), and ELISA for plasma hormonal levels were performed. Results: LH, PRL, and TSH cells showed remarkable plasticity during the annual seasonal reproductive cycle. In the PT, all the 3 cell types were detected during the breeding phase, with additional detection of the TSH immunoreactivity during the pre-breeding and the PRL immunoreactivity during post-breeding phases. Pars distalis (PD) expressions and the plasma levels of the LH and TSH were at the peak during the breeding phase, but the PRL peak was during the post-breeding phase. In addition to PRL in the neurohypophysis and in the median eminence, hypothalamic PRL, and TSH were also elucidated. Conclusions: This study suggests activation of the gonadal axis by the PT TSH which might transduce seasonal cues, but not specifically photoperiod, in the birds of the tropics/subtropics. Post-breeding phase sustained high plasma TSH and peak plasma PRL might coordinate the transition to the non-breeding phase including the trigger of parental care as the later hormone assigned with. Hypothalamic TSH and PRL might influence events of seasonality through central modulation.

Neuropeptide expression and action in the reproductive system of the starfish Asterias rubens.

Reproductive processes are regulated by a variety of neuropeptides in vertebrates and invertebrates. In starfish (phylum Echinodermata), relaxin-like gonad-stimulating peptide triggers oocyte maturation and spawning. However, little is known about other neuropeptides as potential regulators of reproduction in starfish. To address this issue, here, we used histology and immunohistochemistry to analyze the reproductive system of the starfish Asterias rubens at four stages of the seasonal reproductive cycle in male and female animals, investigating the expression of eight neuropeptides: the corticotropin-releasing hormone-type neuropeptide ArCRH, the calcitonin-type neuropeptide ArCT, the pedal peptide-type neuropeptides ArPPLN1b and ArPPLN2h, the vasopressin/ocytocin-type neuropeptide asterotocin, the gonadotropin-releasing hormone-type neuropeptide ArGnRH, and the somatostatin/allatostatin-C-type neuropeptides ArSS1 and ArSS2. The expression of five neuropeptides, ArCRH, ArCT, ArPPLN1b, ArPPLN2h, and asterotocin, was detected in the gonoducts and/or gonads. For example, extensive ArPPLN2h expression was revealed in the coelomic epithelial layer of the gonads throughout the seasonal reproductive cycle in both males and females. However, seasonal and/or sexual differences in the patterns of neuropeptide expression were also observed. Informed by these findings, the in vitro pharmacological effects of neuropeptides on gonad preparations from male and female starfish were investigated. This revealed that ArSS1 causes gonadal contraction and that ArPPLN2h causes gonadal relaxation, with both neuropeptides being more effective on ovaries than testes. Collectively, these findings indicate that multiple neuropeptide signaling systems are involved in the regulation of reproductive function in starfish, with some neuropeptides exerting excitatory or inhibitory effects on gonad contractility that may be physiologically relevant when gametes are expelled during spawning.

Seasonal variations of testis anatomy and of G-coupled oestrogen receptor 1 expression in Gerbillus gerbillus.

The gerbil, Gerbillus gerbillus, a nocturnal desert rodent of northern Africa, exhibits a seasonal reproductive cycle with marked anatomical and behavioural shifts between breeding season and resting season. The aim of this study is to investigate key elements involved in these seasonal changes, specifically in males: the histology of the testis as well as the expression of the G-protein-coupled oestrogen receptor 1 (GPER1) in the testis. During the breeding season, the seminiferous tubules were full of spermatozoa, and their epithelium contained germinal cells embedded in Sertoli cells. Amidst tubules, well-developed Leydig cells were observed around blood vessels, with peritubular myoid cells providing structural and dynamic support to the tubules. GPER1 was largely expressed throughout the testis. Notably, Leydig cells, spermatogonia and spermatocytes showed strong immunohistochemical signals. Sertoli cells, spermatozoa and peritubular myoid cells were moderately stained. During the resting season, spermatogenesis was blocked at the spermatocyte stage, spermatids and spermatozoa were absent and the interstitial space was reduced. The weight of the testis decreased significantly. At this stage, GPER1 was found in Leydig cells, spermatocytes and peritubular myoid cells. Sertoli cells and spermatogonia were not marked. Overall, the testis of the gerbil, Gerbillus gerbillus, has undergone noticeable histological, cellular and weight changes between seasons. In addition, the seasonal expression pattern of GPER1, with pronounced differences between resting season and breeding season, indicates that this receptor is involved in the regulation of the reproductive cycle.

Diversity, seasonal abundance, and environmental drivers of chaetognath populations in North Inlet Estuary, South Carolina, USA.

Chaetognaths (Phylum: Chaetognatha) are one of the most abundant phyla of zooplankton worldwide and play an important role in marine trophic interactions. Although the role of chaetognaths in global ecosystems is well understood, the spatial variation and environmental drivers of estuarine chaetognath populations is poorly understood. To provide the first known record of chaetognath species composition in a coastal estuary in the south-eastern USA, chaetognaths were identified and quantified from zooplankton samples collected on a monthly basis in 2019 and 2020 from North Inlet Estuary in South Carolina. Parasagitta tenuis was the most abundant species of the five found, making up 33% of total abundance. The egg presence of these chaetognaths was further analyzed to gauge reproductive cycles. Abundance and egg presence were compared with surface and bottom measurements of temperature, salinity, and dissolved oxygen levels to determine the driving abiotic factors behind chaetognath's seasonal variability and reproductive cycles. Temperature, salinity, and dissolved oxygen all had low (r < ±.29), non-significant correlations with abundance. Chaetognath egg production was most significantly associated with dissolved oxygen (p < .001) and seasonal changes in temperature (p < .001). Our initial findings indicate the continued abundance of chaetognath in a local estuary are dependent on abiotic factors that are strongly influenced by a changing climate.

The reproductive age of males of the taimyr of wild reindeer (&lt;i&gt;Rangifer tarandus&lt;/i&gt;)

Purpose: to study the age of manufacturers, the share of their participation in the rut and assess the contribution of males of wild deer to the implementation of reproductive cycles of the Taimyr population in the period 1993–2008.Materials and methods. The fees of the material were carried out in the period 1993-2008. On Western Taimyr and Putoran plateau. To identify the environmental-morphophysiological characteristics of males (a pre-productive group 1–3+, reproductive low-ranking and high-ranking males from 4 years and older) performed selective weighing of 38 males in the summer-autumn period (August-October). The body weight of the animal is an indirect reproductive sign of its strength. For low -ranking, animals were taken with a live weight of 80 to 130 kg. High -ranking bulls with body weight for 130 kg were attributed. During the period of spring migration 2001, 2004, 2006. 37 males are balanced. The reproductive success of males was evaluated from the values of the potential fertility of adult females in herds of spring migration flows 1998–2006. During scientific shootings in April -May, 218 pregnant and Yalov female wild deer deer were examined. The reproductive contribution of adult males in the seasonal reproductive cycles of this part of the Taimyr population (the number of fruits per 100 adult females) was calculated from the equality of two relations (proportions) - sexually mature females of this commercial sample (A) to pregnant females of this sample (B) and 100 sexually mature females ( c) to pregnant females (D), i.e. By the main property of the proportion. The individual age of the males was evaluated according to the layered structures of the incisors [12] of the formed layers of the cement of the cutter I1, previously decalcinated by a 5 % solution of nitric acid. Sections of males from samples 1993–2008. Received on a microtome with a freezing model X MZ-1. To count the annual rings of wild reindeer, samples were painted with hematoxylane Erlich.Results. According to selective data (n = 128), the reproductive age of males of Taimyr wild deer was investigated: bulls of 14 age groups from 3 years and older are involved in Gona. The main contribution is made by age groups from 4 to 9 years. These males make up 78.9 % of the reproductive nucleus that supports the reproduction of the population. Until the age of 7, the number of males participating in the rut is growing. From 8 years, the fraction of manufacturers is reduced. In terms of age distribution, the decline of highly productive males begins with 6 years. The largest number of potential manufacturers is provided by 5–7-lite groups (48.42 %), but the maximum number of reproductive males in age distribution is concentrated in a 5-year group, quite numerous in the population-9.4 %. The maximum reproductive age is 16 years (1 male or 0.78 % of the reproductive nucleus). The average age of reproductive males in the population of 7.14 years. The race of animals in West Taimyr flows from October 19–20 to November 9–15 (3-4 weeks). Mating occurs both in short -term large aggregations that combine several hundred to one thousand animals, and in harem groups from 8 to 30 individuals. The average size of harems was detected in the range of 16.2 goals (n = 24). The average indicator of the reproductive contribution of males: 76.6 ± 3.28 fruits per 100 sexually mature females.

Seasonal gonadal changes in adult male lizards of Liolaemus cuyanus (Iguania: Liolaemidae) from the Monte desert, Argentina

Male reproductive cycles in lizards can be continuous or seasonal depending on the environmental conditions and female availability. The aim of this study is to investigate whether adult males of the psammophilus lizard Liolaemus cuyanus present seasonal changes of reproductive traits throughout the reproductive cycle. In order to carry out this task, sampling of specimens (N = 27) was carried out monthly from October to March in Valle de Matagusanos, Ullúm, San Juan, Argentina (31°06′46.08′’ S, 68°38′03.84′’ W; altitude: 945 m), a semi-arid zone. The animals captured in different months were grouped based on reproductive criteria according to three relevant periods: pre-reproductive (PrR), reproductive (R) and post-reproductive (PsR). In order to identify and characterize these periods, several male reproductive traits were obtained, like morphometric parameters (body mass, snout-vent length, testes and abdominal fat body mass), tubular surface and estimation of the interstitial tissue coverage, combined with histological and cell seminiferous tubule observations (germ cells types, histological and ultrastructural details) and presence of sperm in the cauda epididymis. During the PrR period, which occurred during spring, well-developed testes with free tubular sperm cells were present, but these were less frequent than during the R period. On the other hand, luminal sperm cells were evident at the seminiferous tubules from the beginning of the R period, in conjunction with the maximum testes mass and seminiferous tubular surfaces. This was also coincident with a higher abundance of sperm cells in the cauda epididymal lumen. At the end of this period, the initial regression of the seminiferous epithelium was corroborated by organelle regression which was observed in the ultrastructure of spermatogenic cells. At the beginning of the PsR period, before autumn, a marked decrease in male reproductive traits above described was detected. Instead, an increase in abdominal fat body mass could be observed indicating the onset of the lethargy period. The results obtained suggest that this population of L. cuyanus has a seasonal reproductive cycle, with its reproductive activity occurring during the spring-summer months (PrR-R periods) and finishing in late summer (PsR).

The logistic equation in the context of Stieltjes differential and integral equations

In this paper, we introduce logistic equations with Stieltjes derivatives and provide explicit solution formulas. As an application, we present a population model which involves intraspecific competition, periods of hibernation, as well as seasonal reproductive cycles. We also deal with various forms of Stieltjes integral equations, and find the corresponding logistic equations. We show that our work extends earlier results for dynamic equations on time scales, which served as an inspiration for this paper.

Reproduction patterns of the bloody cockle Senilia senilis (Linnaeus 1758) in the Sine-Saloum inverse estuary

Understanding the reproductive biology of a species is an important means of determining the renewal capacity of natural stocks, especially in the case of heavily exploited species. It is a fundamental element in supporting the implementation of management measures. Here, we studied the bloody cockle (S. senilis) in the Sine-Saloum, with the aim of describing its seasonal and spatial reproductive cycle. S. senilis reproduction was studied over an annual cycle at two sites chosen for their contrasting situations along the upstream-downstream gradient. The reproductive cycle was studied by histological analysis of a pool of individuals maintained in-situ and sampled throughout the year. Our results showed that gamete maturation is asynchronous within and between individuals. Gametogenesis mostly occurred in October. The maturation stage showed a seasonal pattern with continuous reproduction throughout the year, with two preferred periods between May and July and December and February. The reproductive cycle is highly dependent on temperature and salinity variations, resulting in a seasonal cycle and spatial heterogeneity. The temperature induces gametogenesis and salinity synchronizes the spawning periods.

Embryonic development timeline in skates (Chondrichthyes: Rajiformes): Sympterygia acuta as the first case study in the family Arhynchobatidae

Oviparous elasmobranch embryos (Chondrichthyes) have been the focus of several embryological studies; they are useful models for studying early ontogeny in vertebrates, as can help explore the existence of common developmental patterns among species. Skates (Rajiformes) are the most speciose order of oviparous elasmobranchs, however, few studies are focused on embryo development and only based on one skate family: Rajidae. Here, we extended the study of embryo development to other skate family, Arhynchobatidae, which represent about 1/3 of all skate species. Three adult female bignose fanskates (Sympterygia acuta) were held in captivity in order to provide the first complete embryonic development timeline for any species within the Arhynchobatidae family. Our results allowed further comparisons at the embryonic scale of different oviparous elasmobranch families, providing an updated cross-species overview of the early ontogeny. Incubation in S. acuta lasted 97 ± 1.4 days at 11–21.7 °C, and hatching size was 93.2 ± 0.2 mm in total length and 49.2 ± 0.3 mm in disc width. Early embryos of S. acuta were anatomically similar to other oviparous elasmobranch embryos, with several structures appearing at the same time, but late embryonic development was comparatively delayed. The late resorption of both the external yolk sac and the external gill filaments, and also the delay in the slit opening could indicate a low metabolic demand in S. acuta, which would probably be coupled with its seasonal reproductive cycle. Some structures such as external gill filaments and claspers appeared at a similar time in some species of Rajidae and also in Arhynchobatidae, but at different times in species of the same family, showing an inconsistency also found within shark families. Although the sequential scheme remained relatively constant, small heterochronies would be present within skates, within sharks, and also between skates and sharks.

Hypothalamic expression of GnRH-I and GnIH in the Eurasian tree sparrow over a single long day.

Seasonal reproductive cycles of most birds are regulated by photoperiod via neuroendocrine control. The present study aims to investigate the role of a single long day in triggering hypothalamic expressions of GnRH-I and GnIH in the Eurasian tree sparrow (Passer montanus). Sparrows were divided into two groups (n = 24 each) and pre-treated under short days (9L: 15D) for 4days. On the fifth day, one group was exposed to long day (14L: 10D), while other was continued under short day for another 1day. Birds of both the groups were sacrificed and perfused on fifth day at different time points, i.e., ZT 14, ZT 16 and ZT 18 and the expressions of GnRH-I and GnIH mRNAs and peptides were studied using real-time PCR and immunohistochemistry, respectively. In addition, testicular size was measured to know testicular development. Observations revealed that birds exposed to a single long day (14L: 10D) showed an increase in hypothalamic expressions of GnRH-I mRNA and peptide and decrease in levels of GnIH mRNA only at ZT 16 and ZT 18 with no significant change in GnIH peptide. However, no significant change in GnRH-I or GnIH expression was observed at any time point under short day and birds maintained high and low expression levels of GnIH and GnRH-I, respectively. Our results clearly indicate that the photoperiodic response system of sparrow is highly sensitive to light and responds even to single long day. Furthermore, they suggest that the GnRH-I and GnIH are expressed in the hypothalamus of tree sparrow in an anti-phasic manner and switching over of their expression occurs at late hours of exposure of birds to single long day.

Reproductive Biology, Sperm storage, and Sexual Maturity of Thamnodynastes strigatus (Serpentes: Dipsadidae).

Life history strategies determine and influence many aspects of species fitness. In this study, we describe the reproductive biology - reproductive cycle, sperm storage, and sexual maturity - of Thamnodynastes strigatus in South Brazil. We analyzed 49 individuals (25 males and 24 females) from herpetological collections. The reproductive cycle of males and females was described considering the morpho-anatomical and histological changes in the testes, ductus deferens, and kidney, as well in the ovary and oviduct. The age at the onset of sexual maturity was determined by skeletochronology of the caudal vertebra. The reproductive cycle is seasonal semi-synchronous and most individuals have a reproductive peak in spring and summer. The seasonal biennial reproductive cycle and viviparity are two phylogenetically conserved characters in Tachymenini snakes. Thamnodynastes Strigatus females store sperm in the utero-vaginal junction furrows during autumn. There were no differences between the ages of sexual maturity of males (4-11y) and females (4-12y). Females reach sexual maturity at larger body sizes, and this may confer an adaptive advantage due to a higher fecundity potential. Herein, we confirmed the previously described seasonal biennial reproductive cycle of T. strigatus through histological analysis.

Cycle of reproduction, oocyte atresia, and maturation size of the Manila clam Ruditapes philippinarum on a pebble beach in Mutsu Bay, Northern Japan

ABSTRACT This study investigated the seasonal cycle of reproduction and oocyte atresia (i.e. cell death and degeneration), and size at maturity of the Manila clam Ruditapes philippinarum (Mollusca: Bivalvia) in Mutsu Bay, Northern Japan. Monthly changes in condition factor and reproductive stage of gonads indicated that females and males spawned during July–September and June–October in 2014, respectively. The volume fraction of atretic oocytes reached a small peak at 9.3% in August (i.e. cell death of oocytes during their development in the spawning period) and the largest peak in October at 25.0% (i.e. residual oocytes in the recovery period). The atretic oocytes under resorption by macrophage-like cells comprised 2.5–14.3% and 100% of total atretic oocytes in the spawning and recovery/early gametogenesis periods, respectively. The shell length at 50% maturity was estimated to be 21.1 mm in females and 18.5 mm in males.

Advances in Reproductive Endocrinology and Neuroendocrine Research Using Catfish Models.

Catfishes, belonging to the order siluriformes, represent one of the largest groups of freshwater fishes with more than 4000 species and almost 12% of teleostean population. Due to their worldwide distribution and diversity, catfishes are interesting models for ecologists and evolutionary biologists. Incidentally, catfish emerged as an excellent animal model for aquaculture research because of economic importance, availability, disease resistance, adaptability to artificial spawning, handling, culture, high fecundity, hatchability, hypoxia tolerance and their ability to acclimate to laboratory conditions. Reproductive system in catfish is orchestrated by complex network of nervous, endocrine system and environmental factors during gonadal growth as well as recrudescence. Lot of new information on the molecular mechanism of gonadal development have been obtained over several decades which are evident from significant number of scientific publications pertaining to reproductive biology and neuroendocrine research in catfish. This review aims to synthesize key findings and compile highly relevant aspects on how catfish can offer insight into fundamental mechanisms of all the areas of reproduction and its neuroendocrine regulation, from gametogenesis to spawning including seasonal reproductive cycle. In addition, the state-of-knowledge surrounding gonadal development and neuroendocrine control of gonadal sex differentiation in catfish are comprehensively summarized in comparison with other fish models.

MATURASI LELE MUTIARA Clarias gariepinus BETINA MELALUI PENAMBAHAN HORMON OODEV DAN ESTRADIOL-17ß PADA PAKAN

The problem in Mutiara strain of North African catfish Clarias gariepinus culture is that the production of both larvae and seeds is still inhibited by the seasonal reproductive cycle where the catfish only spawn once during the spawning season. The purposes of this study were to evaluate the effect of administration of oodev and estradiol-17ß on the maturity process and to determine the best doses in accelerating the maturion of female Mutiara strain. This study used a Completely Randomized Design with 5 treatments and 3 individual replications. The treatments were combination between dose Oodev (PMSG and Anti-Dopamine) and dose Estradiol-17ß in feed (both doses in ml/kg feed):A(0+0), B(0.5+0), C(0+0.6), D(0.5+0,6), E(1+1). The results of this study showed that the administration of Oodev and Estradiol-17ß significant affect on gonadal maturity index about 82.21% compared to control and acclerating maturation of female mutiara strain with doses the best is the treatment E (oodev 1 ml/kg feed+estradiol-17ß 1 ml/kg feed).Key words: Clarias gariepinus, dose, estradiol-17ß, maturation, oodev

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

Simple SummaryThe quail Coturnix coturnix exhibits an annual cycle of testis size, sexual steroid production, and spermatogenesis. The testicular levels of both 17β-estradiol (E2) and androgens are higher during the reproductive period compared to the non-reproductive period, suggesting that estrogens act in synergy with the androgens for the initiation of spermatogenesis. Therefore, the present study aimed to investigate the estrogen responsive system in quail testis in relation to the reproduction seasons, with a focus on the molecular pathways activated in both active and regressive quail testes. The results indicated that estrogens participated in the activation of mitotic and meiotic events during the reproductive period by activating the ERK1/2 and Akt-1 pathways. In the non-reproductive period, when the E2/ERα levels are low, ERK1/2 and Akt-1 pathways remain inactive and apoptotic events occur. Our results suggest that the activation or inhibition of these molecular pathways plays a crucial role in the physiological switch “on/off” of the testicular activity in male quail during the seasonal reproductive cycle.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.