Gonadal Activity Research Articles

Inhibin B, AMH, but not INSL3, IGF1 or DHEAS support differentiation between constitutional delay of growth and puberty and hypogonadotropic hypogonadism.

In pre-pubertal boys ≥ 14years, the differentiation between constitutional delay of growth and puberty (CDGP) and hypogonadotropic hypogonadism (HH) is challenging, as current diagnostic tools have limitations in sensitivity and specificity. The aim of this study was to assess the usefulness of markers of gonadal activity, growth axis activation and adrenarche in differentiation between pre-pubertal CDGP and HH. This retrospective study was carried out between 2006 and 2015 in an academic out-patient referral centre. The clinical data of 94 boys, aged 13.9-23.2years and referred for "pubertal delay" were reviewed. Definite diagnoses were established on initial work-up and clinical follow-up: 24 boys were diagnosed with HH, 22 boys with CDGP, pre-pubertal (PP CDGP) at referral and 28 boys with CDGP, early pubertal at referral (EP CDGP), the latter serving as control group. Twenty patients were excluded from evaluation because of previous sex steroid treatment or associated chronic disease. Inhibin B and AMH were measured in all (n=74); INSL3, IGF1, IGFBP3 and DHEAS in a subset of patients (n=45) in serum of first presentation. Inhibin B and AMH were higher in boys with PP CDGP than in boys with HH: inhibin B: 87.6±42.5 vs. 19.8±13.9pg/mL; p<0.001; AMH: 44.9±27.1 vs. 15.4±8.3ng/mL; p<0.001. Receiver operating characteristics (ROC) for the diagnosis of PPCDGP vs. HH (inhibin B≥28.5pg/mL): sensitivity: 95%, specificity: 75%; AUC: 0.955. In combination with an AMH cut-off ≥20ng/mL the specificity increased to 83%. INSL3, IGF1, IGFBP3 and DHEAS levels were not different. In boys with EP CDGP, inhibin B and IGF1 levels were highest (138.7±59.9 pg/mL/289.7±117ng/mL), whereas AMH levels were lowest (11.7±9.1ng/mL). Sertoli cell markers are helpful for establishing a prognosis, whether a boy with pubertal delay will enter puberty spontaneously, whereas Leydig cell, growth and adrenal markers are not.

Comparison of Gametogenic Cycles of the Endemic European Carpet Shell Clam (Ruditapes decussatus) and the Introduced Manila Clam (Ruditapes philippinarum) from a Temperate Coastal Mediterranean Lagoon in the Dardanelles, Turkey

In this study, the gametogenic cycle of the newly introducedManila clam Ruditapes philippinarum was described for the first time for Turkish waters and compared with that of the native European grooved carpet shell clam Ruditapes decussatus coexisting in Çardak Lagoon (Çanakkale, Turkey) in the Dardanelles. A total of 480 individuals were sampled for each species between January andDecember 2011. Both species exhibited similar distinct seasonal changes in gonad activity and completed their gametogenic cycles. In both species, gonads advanced very fast after winter reaching ripe stage in April and May in theManila clams and carpet shell clams, respectively. In Manila clams, spawning commenced in April and continued until October. In carpet shell clams, spawning started in May, but the main spawning event occurred in June and continued until July with a discontinuation in August and a marginal spawning taking place in September and possibly in October. Gonad index (GI) values were indicated similarities in gonad development between males and females of both species with apparent synchronism between sexes during early development, first maturation and early spawning until July. We report for the first time the reproduction of the Manila clam in Turkish waters and show that optimal conditions for gametogenesis and spawning exist for this exotic species from March until October in the Dardanelles. This information will be useful for clam fishery management especially in areas where carpet shell clam and the Manila clam are known to coexist.

Measuring Faecal Epi-Androsterone as an Indicator of Gonadal Activity in Spotted Hyenas (Crocuta crocuta).

Enzyme immunoassays (EIA) that measure faecal testosterone metabolites (fTM) are useful tools to monitor gonadal activity. The aim of this study was to validate an “in-house” epiandrosterone EIA to monitor fTM in spotted hyenas. FTM were characterised in a male and a female hyena that each received an injection of 3H-testosterone. High-performance liquid chromatography (HPLC) analyses revealed a cluster of highly polar enzyme-hydrolysable hormone metabolite conjugates. We performed hydrolysis using β-glucuronidase to deconjugate metabolites and improve sensitivity of the assay. Because β-glucuronidase from Helix pomatia has been reported to bias testosterone measurements in some species, we compared the enzymatic activity of the commonly used β-glucuronidase extracted from H. pomatia with the same enzyme from Escherichia coli. Our results showed that β-glucuronidases from both sources produced similar results from spotted hyena faeces. We therefore hydrolysed samples with H. pomatia enzymes. HPLC analyses also demonstrated that following hydrolysis the epiandrosterone EIA measured significant amounts of immunoreactive metabolites corresponding to radiolabelled metabolites in both sexes. Additionally, HPLC and GC-MS analyses confirmed the presence of epiandrosterone in faeces of spotted hyenas. The biological relevance of the epiandrosterone EIA was validated by demonstrating (1) a significant increase in fTM levels in response to a testosterone injection within 16 h, (2) no biological responsiveness to an adrenocorticotropic hormone (ACTH) injection and (3) significant differences in fTM levels between juvenile males and adult immigrant males in a free-ranging wild population. Our results clearly demonstrate that the epiandrosterone EIA is a reliable non-invasive method to monitor gonadal activity in spotted hyenas.

Pharmacological and Morphological Evidence of AMPK-Mediated Energy Sensing in the Lower Brain Stem Ependymocytes to Control Reproduction in Female Rodents.

Ependymocytes are one of the energy-sensing cells that regulate animal reproduction through their responsiveness to changes in extracellular glucose levels and the expression of pancreatic-type glucokinase and glucose transporter 2, which play a critical role in sensing blood glucose levels in pancreatic β-cells. Molecular mechanisms underlying glucose sensing in the ependymocytes remain poorly understood. The AMP-activated protein kinase (AMPK), a serine/threonine kinase highly conserved in all eukaryotic cells, has been suggested to be an intracellular fuel gauge that detects cellular energy status. The present study aims to clarify the role AMPK of the lower brainstem ependymocytes has in sensing glucose levels to regulate reproductive functions. First, we will show that administration of 5-aminoimidazole-4-carboxamide-1-β-D-ribofuranoside, an AMPK activator, into the 4th ventricle suppressed pulsatile LH release in female rats. Second, we will demonstrate the presence of AMPK catalytic subunit immunoreactivities in the rat lower brainstem ependymocytes. Third, transgenic mice were generated to visualize the ependymocytes with Venus, a green fluorescent protein, expressed under the control of the mouse vimentin promoter for further in vitro study. The Venus-labeled ependymocytes taken from the lower brainstem of transgenic mice revealed that AMPK activation by 5-aminoimidazole-4-carboxamide-1-β-D-ribofuranoside, an AMPK activator, increased in vitro intracellular calcium concentrations. Taken together, malnutrition-induced AMPK activation of ependymocytes of the lower brainstem might be involved in suppression of GnRH/LH release and then gonadal activities.

Vasa expression in spermatogenic cells during the reproductive-cycle phases of Podarcis sicula (Reptilia, Lacertidae).

The vasa gene encodes a DEAD-box ATP-dependent RNA helicase that regulates the translation of multiple mRNAs involved in germ line differentiation. This protein has been deeply studied in many animals, but few data are available to date on reptiles. In this work, we sequenced a portion of Podarcis sicula vasa gene (Ps-vasa), developed a specific antibody and verified its specificity. Using anti-Ps-Vasa and confocal microscopy, we studied Vasa expression in male germ cells during the reproductive cycle of P. sicula: during full gonadal activity (spring), during regression of gonadal activity (summer) and during slow autumnal recrudescence. We also analyzed Vasa expression in young testes when the walls of the seminiferous tubules were forming. The aim was to verify if Vasa is involved in the process of male germ cell differentiation in all phases of the reproductive cycle. In adult testes, during full gonadal activity and during recrudescence, Vasa staining was detected from spermatogonia to spermatids. Vasa spots were also observed in the nucleus of germ cells supporting its function in different cellular compartments. No Vasa staining was observed in mature spermatozoa during the spring and mid-late November. The seminiferous epithelium analyzed in the summer appeared reduced with only spermatogonia, all Vasa-immunostained, some in division to replace germ cells. In immature testes, the seminiferous epithelium contained only spermatogonia and spermatocytes. The clear immunostaining in their cytoplasm revealed that Vasa is already expressed in juvenile male gonads, suggesting a role in the differentiation process since P. sicula early developmental stages.

Menarche, puberty and vitamin D

Puberty is the development process - result of a complex series of molecular and physiological events, culminating in reproductive capability. Gonadotropin-releasing hormone actively released from specialized neurons of the hypothalamus stimulates gonadal activation and triggers physical changes of puberty through initiation of the hormonal cascade. Epidemiologic studies and numerous clinical trials claim that sufficient levels of vitamin D3 are essential for normal physiological growth, development and puberty, by activation of the neurohormonal multisystem in the hypothalamus-pituitary-gonadal axis. Various scientific studies investigate the role of vitamin D3 and its metabolites in specific reproductive disorders of women and men. All these data contribute to intensive research on vitamin D3 and its receptor as a potential factor, affecting the pathogenesis of a numerous diseases, connected with its non-classical function, such as diabetes, obesity, cancer, puberty disorders and infertility. In the last decade, the prevalence of vitamin D3 deficiency has been increasing in many parts of the world, that has caused an increasing number of medical research on the subject. Nevertheless, data on the vitamin D status and its association with puberty in girls are constrained. This paper was written to present different studies on vitamin D3 and its influence on puberty through the regulation of the neurohormonal system during sexual maturity

Interaction of specific temporal phase relations of circadian neural oscillations and long term photoperiodic responses in Japanese quail, Coturnix coturnix japonica

Specific temporal phase relations of neural oscillations are reported to regulate gonadal activity in many avian species but their interaction with photo-sexual response are still unclear. Hence in the present study, 3week old Japanese quail maintained in short days (experiment 1) received normal saline (SD control) or serotonin precursor 5-HTP and dopamine precursor l-DOPA injections at the interval of 12h (SD 12-h) for 13days. At 37week of age, one subgroup of SD 12-h received these drugs at the interval of 8-h (SD 12-h+8-h). In the second experiment, 3week old quail were injected with 5-HTP and l-DOPA 8h apart (LD 8-h) and then maintained under long days. At the age of 37weeks, one subgroup of these LD quail was retreated with 5-HTP and l-DOPA at the interval of 8h (LD 8-h+8-h). Cloacal gland volume was monitored weekly up to 45weeks of age in both experiments and other reproductive parameters were monitored at 23 and 45week of age.These results indicate that 12-h phase relation of neurotransmitter precursors not only initiates early onset of scotorefractoriness i.e., full development of gonad even under short-day length but maintains it continuously (a long lasting effect) unlike control and the 8-h relation dissipates it, making the quail scotosensitive. On the other hand, the 8-h phase relation suppresses the gonado-stimulatory effect of long days but this effect is transitory. Thus the 12-h phase relation is gonado-stimulatory under short day conditions and the 8-h relation is gonado-inhibitory even under long days, inducing scotorefractoriness and photorefractoriness, respectively, it is suggested that effects of specific temporal phase relation of circadian neural oscillations similar to photoperiodic effects, are not only mediated by HPG axis but may also modulate the classical photoperiodic responses of Japanese quail.

Seasonal gonad cycle of the climbing perch Anabas testudineus (Teleostei: Anabantidae) in a tropical wetland

Seasonal reproduction of the climbing perch Anabas testudineus in the Candaba wetland, Philippines, is described. Monthly specimens were collected, gonads and viscera excised, and the gonads histologically examined. Low mean female gonadosomatic index [GSI (%)] from September to February (0.3–2.1 %) increased in March (8.7 %), peaked in May (10.9 %), and declined in June (3.3 %), but increased again in July and August (8.3–5.5 %). Male GSIs (at least 1 %) were low from September until May, increased in June (2.5 %), and then declined thereafter. All the six oocyte and four spermatogenic cell development stages were observed in the gonads throughout the annual cycle. The ovary was dominated by primary growth oocytes (chromatin nucleolus, perinucleolus) from August to February (77–90 %), but yolky oocytes (previtellogenic, vitellogenic) comprised 15 % to 28 % of the ovary from March to July. Mature oocytes were present for most of the year, comprising 40 % of the total oocytes in March-April, peaking in May (50 %), but declining to 30 % in June–July. Spermatozoa consistently dominated the testis throughout the annual cycle, particularly in November and March (58 %). Food intake in both sexes was generally low during the dry season (December–April) when gonad activity was also low, but started to increase at the onset of the wet season (May–November) when gonad activity began to peak. These results demonstrate that the climbing perch gonads exhibit asynchronous development, allowing a protracted breeding season with intense gonad activity timed at the onset of the wet season, concurrent with increasing food intake through the rest of the season.

Different effects of an extended photoperiod treatment on growth, gonadal function, and condition of hair coats in Thoroughbred yearlings reared under different climate conditions.

ABSTRACTOne- to two-year-old Thoroughbred colts and fillies being reared in Miyazaki (warm climate) and Hidaka (cold climate), Japan, were administered extended photoperiod (EP) treatment between December 20 and the following April 10, and its effect on growth, endocrine changes, gonadal activation, and hair coat condition was investigated. In colts reared in Miyazaki, no effect of EP treatment was noted on the growth indices, including body weight (BW), height at withers (HW), girth, and cannon circumference (CC), whereas the BWs and CCs of fillies were significantly higher in the EP treatment group than the control. In Hidaka, the BWs and HWs of colts and HWs of fillies were significantly higher in the EP treatment group. Gonadal activation characterized by an increase in circulating hormone concentrations was earlier in the EP treatment group for fillies reared in Miyazaki [luteinizing hormone (LH), follicle-stimulating hormone (FSH), progesterone (P4), and estradiol-17β (E2)] and in colts (LH, testosterone, and E2) and fillies (LH, FSH, P4, and E2) reared in Hidaka. Regardless of sex and climate, prolactin was significantly higher in the EP treatment group, whereas insulin-like growth factor (IGF-I) was not. Initial ovulation occurred before April in more of the EP treatment group than the control regardless of the climate. Molting of the hair coat, examined in March, was advanced in the EP treatment group regardless of sex and climate. These results suggest that EP treatment may promote growth and gonadal activation in fillies reared in Miyazaki and in colts and fillies reared in Hidaka and that the effect may be mediated by prolactin.

Effects of estradiol on neural responses to social signals in female túngara frogs.

Estradiol plays an important role in mediating changes in female sexual behavior across reproductive cycles. In the túngara frog [Physalaemus (=Engystomops) pustulosus], the relationship between gonadal activity and female sexual behavior, as expressed by phonotaxis, is mediated primarily by estradiol. Estradiol receptors are expressed in auditory and motivational brain areas and the hormone could serve as an important modulator of neural responses to conspecific calls. To better understand how estradiol modifies neural responses to conspecific social signals, we manipulated estradiol levels and measured expression of the immediate early gene egr-1 in the auditory midbrain, thalamus and limbic forebrain in response to conspecific or heterospecific calls. We found that estradiol and conspecific calls increased egr-1 expression in the auditory midbrain and limbic forebrain, but in the thalamus, only conspecific calls were effective. In the preoptic area, estradiol enhanced the effect of the conspecific call on egr-1 expression, suggesting that the preoptic area could act as a hormonal gatekeeper to phonotaxis. Overall, the results suggest that estradiol has broad influences on the neural circuit involved in female reproduction, particularly those implicated in phonotaxis.

Expression of nestin in superior cervical ganglia of rats is influenced by gender and gonadectomy

Neurons and glia arise from neural progenitor cells that express nestin. Although substantial changes in neuronal development were observed during the postnatal period, data concerning dynamics of nestin expression in the superior cervical ganglia (SCG) of rat during that period are lacking. It is known that gonadectomy and steroid hormones influence the development of neurons in the SCG during the postnatal period, but there are no data on how they influence the persistence of nestin expression in the SCG cells.The dynamics of nestin expression in the SCG in rats of three age groups, as well as the influence of gender and gonadectomy, was investigated.Three groups of male rats were sacrificed at 2, 3 and 6 months of age. Additional groups of male and female Sprague-Dawley rats were gonadectomized at the age of 2 months. After 30 days, they were sacrificed and SCGs were harvested and processed immunohistochemically. Immunoreactivity for nestin in the SCG was observed in satellite glia, based on their expression of s100. The proportion of neurons that were encircled with nestin-immunoreactive satellite cells (nestin encircled neurons, NEN) decreased between second and third month of age (p<0.05). The proportion of NEN was greater in the NPY+ than in the NPY− subpopulation. The proportion of NEN in the SCG of female rats was significantly higher (p<0.05) than that of both, the male rats and ovariectomised groups. The percentage of these neurons was significantly higher (p<0.05) in orchidectomised, in comparison to male rats.Results show the existence of nestin-immunoreactive satellite cells in the SCG of adult rats. A substantial decrease of nestin expression in SCG cells of rats, after the onset of sexual maturation, was observed. This decrease showed significant sex-dependence and was dramatically influenced by gonadal activity.

Life history of a cyprinid species in non‐regulated and regulated rivers from permanent and temporary Mediterranean basins

AbstractStreamflow variability, natural and human induced, has been suggested as a driver of life history differences among freshwater fish populations. During 1 year, we collected bimonthly and fortnightly samples from four populations of Iberian barbel, inhabiting permanent and temporary Mediterranean rivers with non‐regulated and regulated flow regimes. We analysed data for fish age, growth and reproduction to (i) compare barbels' life cycles between permanent and temporary non‐regulated rivers; (ii) assess the effect of two types of flow alteration in these traits; and (iii) identify flow variables significantly related with growth and reproductive cycles. Regional differences were related with the age of first maturation, growth rate and timing and duration of the reproductive season. Flow regulation promoted a decrease of fish growth rates, condition and gonad activity and an increase of maximum length and longevity. Seasonal variation of growth and gonad maturation were related with temperature and streamflow components. This study offers a multi‐regional perspective of the relationship between fish biological cycles and streamflow variability, providing water resource managers with needed perspective about the effect of anthropogenic alteration of streamflow magnitudes. Copyright © 2014 John Wiley &amp; Sons, Ltd.

Melatonin in sperm biology: breaking paradigms.

Melatonin is a ubiquitous molecule, present in a wide range of organisms, and involved in multiple functions. Melatonin relays the information about the photoperiod to the tissues that express melatonin-binding sites in both central and peripheral nervous systems. This hormone has a complex mechanism of action. It can cross the cell plasma membrane and exert its actions in all cells of the body. Certain melatonin actions are mediated by receptors that belong to the superfamily of G-protein-coupled receptors (GPCRs), the MT1 and MT2 membrane. Melatonin can also bind to calmodulin as well as to nuclear receptors of the retinoic acid receptor family, RORα1, RORα2 and RZRβ. The purpose of this review is to report on recent developments in the physiological role of melatonin and its receptors. Specific issues concerning the biological function of melatonin in mammalian seasonal reproduction and spermatozoa are considered. The significance of the continuous presence of melatonin in seminal plasma with a fairly constant concentration is also discussed.

The Role of Different Photoperiods in the Activation of the Thyroid Gland and Ovaries of Adult and Aged Rats ( Rattus Norvegicus )

Back ground: Many animals use the length of the day (photoperiod) to predict and adjust to seasonal changes in the environment through predictive changes in physiology and behaviour. The present work is designed to study the effect of different photoperiod regimes, i.e., short photoperiod 10L:14D, long photoperiod 14L:10D and 12L:12D light-dark cycle (LD) on the structure and hormonal secretion of the thyroid gland and ovaries in adult and aged female rats. Material and methods: The rats were divided into 6 groups, each group contained 6 adults (6 months old) or aged rats (18 months old) and maintained for one month under different photoperiod regimes. Results: Short and long photoperiods increased the activity of the thyroid gland of the adult rats. This gland was full of small follicles lined with simple columnar epithelium. Serum thyroxin levels were extremely higher in long photoperiod group than that observed in 12:12LD and short photoperiod groups. In contrast short photoperiod induced an increase in serum thyroxin level in the aged rats. Short photoperiod and 12:12 LD cycle enhanced gonadal activity of the adult rats. The ovary contained clusters of primordial follicles, different stages of ovarian follicles, and, few numbers of atretic follicles. In the groups of the aged rats all the stages of the ovarian follicles exhibited signs of atresia in such groups. LH, FSH, progesterone and estrogen were increased mainly in the control group in adult and aged rats compared to the photoperiod groups. From the present result we could conclude that: 12:12 light dark cycle enhanced the structural and functional activities of ovaries in adult rats, while aging decreased their activities. In contrast, long photoperiod induced thyroid gland activities in adult rats while short photoperiods activated the gland of aged rats.

Regulation of gonadotropin secretion by monitoring energy availability.

Nutrition is a principal environmental factor influencing fertility in animals. Energy deficit causes amenorrhea, delayed puberty, and suppression of copulatory behaviors by inhibiting gonadal activity. When gonadal activity is impaired by malnutrition, the signals originating from an undernourished state are ultimately conveyed to the gonadotropin-releasing hormone (GnRH) pulse generator, leading to suppressed secretion of GnRH and luteinizing hormone (LH). The mechanism responsible for energetic control of gonadotropin release is believed to involve metabolic signals, sensing mechanisms, and neuroendocrine pathways. The availabilities of blood-borne energy substrates such as glucose, fatty acids, and ketone bodies, which fluctuate in parallel with changes in nutritional status, act as metabolic signals that regulate the GnRH pulse generator activity and GnRH/LH release. As components of the specific sensing system, the ependymocytes lining the cerebroventricular wall in the lower brainstem integrate the information derived from metabolic signals to control gonadotropin release. One of the pathways responsible for the energetic control of gonadal activity consists of noradrenergic neurons from the solitary tract nucleus in the lower brainstem, projecting to the paraventricular nucleus of the hypothalamus. Further studies are needed to elucidate the mechanisms underlying energetic control of reproductive function.

Neuroendocrine gene expression reveals a decrease in dopamine D2B receptor with no changes in GnRH system during prepubertal metamorphosis of silvering in wild Japanese eel

Silvering is a prepubertal metamorphosis preparing the eel to the oceanic reproductive migration. A moderate gonad development occurs during this metamorphosis from the sedentary yellow stage to the migratory silver stage. The aim of this study was to elucidate the molecular aspects of various endocrine parameters of BPG axis at different ovarian developmental stages in wild yellow and silver female Japanese eels. The GSI of the sampled female eels ranged between 0.18 and 2.3%, corresponding to yellow, pre-silver and silver stages. Gonad histology showed changes from previtellogenic oocytes in yellow eels to early vitellogenic oocytes in silver eels. Both serum E2 and T concentrations significantly increased with ovarian development indicating a significant activation of steroidogenesis during silvering. In agreement with previous studies, significant increases in pituitary gonadotropin beta subunits FSH-β and LH-β transcripts were also measured by qPCR, supporting that the activation of pituitary gonadotropin expression is likely responsible for the significant ovarian development observed during silvering. We investigated for the first time the possible brain neuroendocrine mechanisms involved in the activation of the pituitary gonadotropic function during silvering. By analyzing the expression of genes representative of the stimulatory GnRH control and the inhibitory dopaminergic control. The transcript levels of mGnRH and the three GnRH receptors did not change in the brain and pituitary between yellow and silver stages, suggesting that gene expression of the GnRH system is not significantly activated during silvering. The brain transcript levels of tyrosine hydroxylase, limiting enzyme of DA synthesis did not change during silvering, indicating that the DA synthesis activity was maintained. In contrast, a significant decrease in DA-D2B receptor expression in the forebrain and pituitary was observed, with no changes in DA-D2A receptor. The decrease in the pituitary expression of DA-D2BR during silvering would allow a reduced inhibitory effect of DA. We may raise the hypothesis that this regulation of D2BR gene expression is one of the neuroendocrine mechanisms involved in the slight activation of the pituitary gonadotropin and gonadal activity that occur at silvering.

Reproduction of a whiptail lizard (Ameivula ocellifera, Teiidae) from a coastal area in northeastern Brazil.

The reproductive ecology of Ameivula ocellifera was studied from September 2009 to August 2010 in a coastal area of the state of Ceará, Brazil. Females reproduced continuously throughout the year, with a peak at the end of the rainy season. Even though there was a predominance of pre-reproductive individuals in the sample, gonadal activity of males peaked synchronously to female reproduction. Mean clutch size was 1.98 ± 0.56 and positively associated with female body size, while mean egg volume was 510.54 ± 84.29 mm3 and unrelated to female body size. We did not find any association between clutch size and average egg volume.

Reproduction and diet of Hyla euphorbiacea (Anura: Hylidae) in a pine-oak forest of southeastern Puebla, Mexico

We studied some reproductive characteristics and diet of the hylid frog Hyla euphorbiacea in a pine-oak forest from Sierra Negra, southeastern Puebla, Mexico. The breeding season lasted from June to September; during this period males exhibited monthly variation in gonadal activity, whereas females did not. Sexual size dimorphism was observed, with females being larger than males, and female size was positively correlated with number and diameter of ovarian follicles. Diet during the rainy season was composed of invertebrates, classified into 16 prey categories. The most important was Lepidoptera (larvae), followed by Coleoptera (adults), and Araneae. Diet diversity and trophic niche overlap between sexes were relatively high. We discuss some recent findings and biological characteristics of H. euphorbiacea, which potentially make this species more susceptible to population declines than other members of the genus.

Testosterone production and spermatogenesis in free-ranging Eurasian lynx (Lynx lynx) throughout the year

Seasonal variation in reproduction is common in mammals as an adaptation to annual changes in the habitat. In lynx, male reproduction activity is of special interest because female lynxes are monoestric with an unusual narrow (about 1 month) breeding season. In Eurasian lynx, mating occurs between January and April depending on the latitude. To characterize the seasonal pattern of sperm and testosterone production in free-ranging Eurasian lynxes, long-term frozen-stored testis material obtained postmortem from 74 hunted or road-killed lynxes in Sweden was used to analyze annual changes in testis mass, testicular testosterone content, and spermatogenetic activity. Values of most gonadal parameters obtained in subadult lynxes were significantly different from the values observed in adult males. In adult lynxes, a moderate annual fluctuation of gonadal parameters was found which was most profound for testis weight and testicular testosterone concentration reaching highest values in March (median of 2.18 g and 2.67 μg/g tissue respectively). Grouping the data of pre-/breeding (January–April) and postbreeding season (May–September) revealed significant changes in testis weight and testosterone concentration. The relative spermatogenetic activity remained high in postbreeding testes. However, net sperm production decreased according to reduction of testis mass and a tendency to lower cauda epididymal sperm numbers in the postbreeding period was observed. Our results demonstrate that it is possible to analyze the gonadal activity of frozen testis/epididymis tissue postmortem and that male Eurasian lynxes show—opposite to the females—only moderate seasonal changes in their reproductive capacity.

The MID-PIWI module of Piwi proteins specifies nucleotide- and strand-biases of piRNAs.

Piwi-interacting RNAs (piRNAs) guide Piwi Argonautes to suppress transposon activity in animal gonads. Known piRNA populations are extremely complex, with millions of individual sequences present in a single organism. Despite this complexity, specific Piwi proteins incorporate piRNAs with distinct nucleotide- and transposon strand-biases (antisense or sense) of unknown origin. Here, we examined the contribution of structural domains in Piwi proteins toward defining these biases. We report the first crystal structure of the MID domain from a Piwi Argonaute and use docking experiments to show its ability to specify recognition of 5' uridine (1U-bias) of piRNAs. Mutational analyses reveal the importance of 5' end-recognition within the MID domain for piRNA biogenesis in vivo. Finally, domain-swapping experiments uncover an unexpected role for the MID-PIWI module of a Piwi protein in dictating the transposon strand-orientation of its bound piRNAs. Our work identifies structural features that allow distinguishing individual Piwi members during piRNA biogenesis.