Non-breeding Phase Research Articles

Seasonal piRNA Expression Profile Changes in the Testes of Plateau Zokor (Eospalax baileyi).

Seasonal reproduction is a mammalian behavior that has developed over an extended evolutionary period and requires animals to respond to external environmental changes to facilitate reproduction. In this study, we investigated the role of PIWI-interacting RNA (piRNA) in the seasonal reproduction of plateau zokors (Eospalax baileyi). piRNA expression profiles in plateau zokor testes during both breeding and non-breeding seasons were examined. The piRNAs had a distinctive ping-pong signature and ranged from 27 to 32 nt with a peak at 30 nt. Testicular piRNAs predominantly aligned to specific genomic regions, including repeat and gene regions. Analysis of the piRNA-mRNA interaction network and functional enrichment of differentially expressed piRNAs targeting mRNAs revealed their association with testicular development and spermatogenesis. Significantly, PIWIL4 is an mRNA gene that interacts with piRNA and exhibits high expression levels within the testes during the non-breeding phase. This study provides a foundation to improve our understanding of piRNA regulatory mechanisms during testicular development and spermatogenesis in seasonally reproducing animals and, specifically, in the plateau zokor.

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.

The opioid peptide leucine-enkephalin disrupts seasonal and gonadotropin-induced ovarian recrudescence in the gecko Hemidactylus frenatus

The enkephalins are known to regulate many physiological functions, including reproduction in vertebrates. However, the role of leucine-enkephalin (L-ENK) in the ovarian recrudescence activity of reptiles is not known. In the present study, we studied the influence of L-ENK on seasonal and FSH–induced ovarian recrudescence during the breeding and non-breeding phases of the cycle in the tropical and subtropical gecko Hemidactylus frenatus. In the first experiment, treatment with 5 and 25 μg L-ENK resulted in a dose-dependent inhibitory effect on the hypothalamic gonadotropin-releasing hormone (GnRH) neurons and ovary, as indicated by a significantly decreased percent area of GnRH-immunoreactive (GnRH-ir) fibres in the median eminence and pars distalis of the pituitary gland, concomitant with complete absence of stage V (late vitellogenic) follicles in the ovary compared to those of experimental controls. In the second experiment, administration of FSH to lizards in the regression phase stimulated the recruitment of stage IV and V (vitellogenic) follicles in contrast to their absence in initial controls or treatment controls. However, similar treatment of FSH in combination with 25 μg L-ENK did not result in the development of stage IV or V follicles. Together, these results suggest for the first time that treatment with 5 and 25 μg L-ENK exerts a dose-dependent inhibitory effect on the hypothalamic GnRH release into the median eminence and pituitary gland, leading to the blockade of ovarian recrudescence. These results also suggest a possible direct inhibitory effect of L-ENK at the level of the ovary in the gecko.

Annual movements of a migratory seabird—the NW European red-throated diver (Gavia stellata)—reveals high individual repeatability but low migratory connectivity

In this study, the annual movements of a seabird species, the red-throated diver (Gavia stellata), were investigated in space and time. Between 2015 and 2017, 33 individuals were fitted with satellite transmitters at the German Bight (eastern North Sea). In addition, stable isotope analyses of feathers (δ13C) were used to identify staging areas during the previous moult. The German Bight is an important area for this species, but is also strongly affected by anthropogenic impacts. To understand how this might affect populations, we aimed to determine the degree of connectivity and site fidelity, and the extent to which seasonal migrations vary among different breeding locations in the high Arctic. Tagged individuals migrated to Greenland (n = 2), Svalbard (n = 2), Norway (n = 4) and northern Russia (n = 25). Although individuals from a shared breeding region (northern Russia) largely moved along the same route, individuals dispersed to different, separate areas during the non-breeding phase. Kernel density estimates also overlapped only partially, indicating low connectivity. The timing of breeding was correlated with the breeding longitude, with 40 days later arrival at the easternmost than westernmost breeding sites. Repeatability analyses between years revealed a generally high individual site fidelity with respect to spring staging, breeding and moulting sites. In summary, low connectivity and the distribution to different sites suggests some resilience to population decline among subpopulations. However, it should be noted that the majority of individuals breeding in northern Russia migrated along a similar route and that disturbance in areas visited along this route could have a greater impact on this population. In turn, individual site fidelity could indicate low adaptability to environmental changes and could lead to potential carry-over effects. Annual migration data indicate that conservation planning must consider all sites used by such mobile species.

Seasonal plasticity in the morphology and cytoarchitecture of the hippocampal complex of the Indian Roller, Coracias benghalensis

Coracias benghalensis, commonly known as Indian Roller, a subtropical seasonally breeding bird native to Prayagraj (25° 28′ N, 81° 54′ E), U.P., India, exhibits a specific rolling behavior (an ornate sexual display) to attract the female for courtship. We hypothesized that the emergence of the seasonal rolling behavior of C. benghalensis would coincide with seasonal neuronal morphology changes in the dorsomedial hippocampus (DMH) area of the hippocampal complex (HCC). To test this hypothesis, the present study aimed to reveal qualitative and quantitative changes in neuronal plasticity in various neuronal classes of DMH across the breeding (pre-breeding and breeding) and the non-breeding (quiescent and regression) phases of the reproductive cycle of C. benghalensis. Plasticity in the morphology of four neuronal types (unipolar, bipolar, pyramidal, and multipolar) in the DMH area of HCC during the breeding and the non-breeding phases was characterized by using Golgi-Colonnier staining for identification and characterization of neuronal morphology. As compared to the quiescent phase, a significant increase of soma diameter, dendritic field, dendritic thickness, length of spine neck, spine head diameter, number of visible spines, and spine density in all four types of neurons was observed during the breeding phase. In contrast, significant decreases were observed during the bird's non-breeding phase compared to the breeding phase. This study concludes that during the breeding phase of C. benghalensis, neuronal arborization was substantially increased in DMH, suggesting an enhanced capability for circuit plasticity possibly underlying rolling behavior. Our study establishes seasonal plasticity in DMH and will serve as a novel model for future studies investigating the molecular, physiological, and cellular mechanisms underlying complex, yet stereotyped, sensorimotor behavior.

Migration gives sleepless nights to the birds: a study on a Palaearctic–Indian migrant, Emberiza bruniceps

Migration is a seasonal phenomenon, wherein the birds swap between their breeding and overwintering grounds to avoid harsh climatic conditions and maximally utilize the geographical resources available. The annual cycle of a migratory bird broadly comprises non-breeding and breeding phases. The non-breeding phase corresponds to non-migratory life history state (LHS), whereas the breeding phase can be bifurcated into migratory (spring/autumn migration) and reproductive stages. Since most of the migratory birds are nocturnal migrants, this results either in shift or compromised sleep in these organisms for the sake of their reproduction and survival. Thus, an obvious question arises regarding the prevalence and distribution of sleep in these night migrants. Therefore, the present study focuses on the life history state-dependent as well as daily (with reference to night) differences in sleep behavior with special mention of different sleep postures in a migratory bunting, Emberiza bruniceps. For this purpose, male redheaded buntings were procured from the wild, and after acclimation in laboratory condition, were subjected to short (8L:16D) and long (13L:11D) photoperiodic schedules. Short photoperiod corresponds to non-migratory, whereas long photoperiod leads to pre-migratory and migratory LHSs. The results reveal that sleep behavior varied with different life history states of the bird. Non-migratory and pre-migratory states were dominated by front and back sleep postures, whereas migratory phase was dominated by active wakefulness. Not only life history state, even the night itself showed gradation in occurrence of different sleep behaviors. As the study was conducted in different phases of night, phasic distribution of different sleep behaviors was also observed. Thus, the bird under study, redheaded bunting, clearly demonstrated life history state, as well as daily differences in distribution of different sleep behaviors.

Colour change in a structural ornament is related to individual quality, parasites and mating patterns in the blue tit.

Carry-over effects refer to processes that occur in one season and influence fitness in the following. In birds, two costly activities, namely reproduction and moult, are restricted to a small time window, and sometimes overlap. Thus, colour in newly moulted feathers is likely to be affected by the costs of reproduction. Using models of bird vision we investigated male colour change in a free-living population of blue tits (Cyanistes caeruleus) in three sampling occasions: spring 1, winter and spring 2. We related crown, tail, breast and cheek feather colouration after the moult (winter) to the intensity of infections by blood parasites during reproduction (spring 1). In the following spring (spring 2), we explored mating patterns with respect to changes in feather colour (springs 1 vs. 2). Males that were less intensely infected by the malaria parasite Plasmodium while breeding showed purer white cheek feathers in winter, which may indicate higher feather quality. Increased brightness in the white cheek was associated with better body condition during reproduction. In the following season, males with brighter cheeks paired with females that had noticeably brighter cheek patches compared to the male's previous mate. These results suggest that the conditions experienced during reproduction are likely to affect moult and thus feather colouration, at least in the white patch. High quality individuals may allocate resources efficiently during reproduction increasing future reproductive success through variation in mating patterns. Carry-over effects from reproduction might extend not only to the non-breeding phase, but also to the following breeding season.

Short distance directional migration in the threatened Socotra cormorant: link to primary productivity and implications for conservation

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 575:181-194 (2017) - DOI: https://doi.org/10.3354/meps12209 Short distance directional migration in the threatened Socotra cormorant: link to primary productivity and implications for conservation Sabir B. Muzaffar1,*, Chris Clarke1, Roxanne Whelan1, Rob Gubiani1, Timothée R. Cook2,3 1Department of Biology, United Arab Emirates University, PO Box 15551, Al Ain, United Arab Emirates 2Institute of Ecology and Environmental Sciences, Department of Evolutionary Ecology, Evolutionary Ecophysiology Team, University Pierre et Marie Curie, Bâtiment 34-44 - 5e étage, 4 place Jussieu, 75252 Paris, France 3FitzPatrick Institute of African Ornithology, DST-NRF Centre of Excellence, University of Cape Town, Rondebosch 7701, South Africa *Corresponding author: s_muzaffar@uaeu.ac.ae ABSTRACT: Conservation of threatened seabirds commonly focuses on protection of breeding areas. However, conditions at non-breeding areas also affect population dynamics, calling for a better understanding of seabird migratory ecology. In particular, it is crucial to identify the type of migration and the oceanic conditions determining non-breeding habitat selection. We studied movements of the threatened Socotra cormorant Phalacrocorax nigrogularis breeding at Siniya Island, United Arab Emirates (UAE) (35% of the world population), using platform transmitter terminals (PTTs) deployed on adults during the 2013 and 2014 breeding seasons. Concomitantly, we used remotely-sensed chlorophyll a concentration data (CHL) of areas visited by birds in the Arabian Gulf and Gulf of Oman regions (2002 to 2016 monthly averages), as an index of primary productivity. The migratory pattern of the Socotra cormorant was non-dispersive, fitting with the gregarious habits and group foraging mode of this forage fish specialist. Birds performed a short westward directional migration to islands off western UAE, then moved eastwards to the Strait of Hormuz before returning to Siniya Island. Birds concentrated at a few localities, which therefore represent areas of high conservation priority. During breeding, CHL around the colony was high. During non-breeding, however, CHL around non-breeding areas was low, even though more productive waters were present within foraging range. The mismatch between the non-breeding phase and CHL could be linked to spatial and temporal lags in responses of secondary and tertiary consumers to primary productivity. Effective conservation will necessitate a better understanding of the ecology and distribution of forage fish within the Gulf. KEY WORDS: Seabird · PTT · Chlorophyll a · Arabian Gulf · Anchovy · Herring · Flying fish · United Arab Emirates Full text in pdf format Supplementary material PreviousNextCite this article as: Muzaffar SB, Clarke C, Whelan R, Gubiani R, Cook TR (2017) Short distance directional migration in the threatened Socotra cormorant: link to primary productivity and implications for conservation. Mar Ecol Prog Ser 575:181-194. https://doi.org/10.3354/meps12209 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 575. Online publication date: July 20, 2017 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2017 Inter-Research.

Seabird breeding population size on the Antarctic Peninsula related to fisheries activities in non-breeding ranges off South America

AbstractPopulation growth of the southern giant petrelMacronectes giganteusfrom South America has been linked with an increase in fishing activities. It was demonstrated recently that a population from Elephant Island, Antarctic Peninsula, largely overlaps its non-breeding distribution with zones of high fishing intensity off South America. This study investigated the assumption that the increase in this population since the 1980s is related to an increase in fisheries off South America. Our results show that the population size is proportional to the increase in demersal and squid fisheries. These fisheries produce a considerable amount of discards, which can be used by non-breeding southern giant petrels as a food source during unfavourable conditions in winter. This may enhance the adult survival rates with potential carry-over effects on population size. Our study shows that we need to further understand the effects of fishery discards/offal on scavenging seabirds of the Southern Ocean, and highlights the importance of understanding the carry-over effects of seabird–fisheries interactions during the non-breeding phase in population dynamics.

Year-round distribution suggests spatial segregation of Cory’s shearwaters, based on individual experience

Recent studies have shown that pelagic seabirds with little breeding experience are wide ranging individuals exploring different foraging grounds and occupying generally more pelagic habitats than more experienced birds. This study compared the spatial dynamic of the year-round distribution and behaviour between two different population components: experienced (Exp; >2 years of successful breeding) and inexperienced (Inexp; ≤2 successful years) Cory’s shearwaters (Calonectris borealis) individuals from Berlenga Island, offshore the Portuguese coast. Our aim was to verify the occurrence of variations in the at-sea activity, foraging habitats and isotopic niches of Exp (N = 11) and Inexp (N = 11) individuals, during their breeding and non-breeding phases. Our results confirmed differences in the migratory routes and foraging grounds during the annual cycle between these two population components: Inexp birds exhibited a more pelagic behaviour than Exp birds, with extensive migratory routes, marked by several stopovers, and a higher number of non-breeding areas. Exp individuals migrated through shorter routes, and wintered in fewer locations. Exp individuals foraged on coastal, shallow and cold water areas and showed higher carbon and nitrogen isotopic values, while Inexp birds foraged more on pelagic, windy and frontal zones and exhibited lower carbon and nitrogen isotopic values. Our results suggest that experience plays a relevant role in explaining the spatial distribution and behaviour of pelagic seabirds such as Cory’s shearwaters. Future research with larger sample sizes should focus on comparing the behaviour of juvenile, immature, first-time breeders and breeders with increasing experience and age.

Conservation implications of consistent foraging and trophic ecology in a rare petrel species

Individuals within populations can use different resources, leading to ecological segregation and niche variation. This segregation could have direct impacts on the migratory strategy or breeding success, thus affecting the overall population and community dynamics and, ultimately, survival. In this study, we assessed the inter-annual and within individual foraging ecology of an endemic and highly threatened seabird species, the Desertas petrel Pterodroma deserta, during the breeding and non-breeding phases. We combined 54 annual tracks (26 individuals; 2009–2013) obtained with light-level loggers (Global Location Sensing or GLS loggers) with stable isotope analyses (δ15N and δ13C) of blood (plasma and cells) and feathers. Wide-ranging tracking data show that this species is a generalist predator, able to adapt to very different habitats. All birds remained faithful to their selected non-breeding areas over the years leading to very high spatial, temporal and trophic consistency among years (i.e. usually with intra-correlation coefficient values, which is an index of repeatability of > 40%). During both the breeding and non-breeding seasons, individual birds showed narrow and segregated isotopic niches, indicating a high level of specialization and limited choice of prey and habitats. The conservation of a seabird with such a dispersive (species-level) yet consistent (individual-level) non-breeding distribution pattern represents a challenge in marine policy terms. On the one hand, such a consistent temporal and spatial pattern will help with defining core areas for conservation, which could be protected through specific management measures or by the establishment of marine protected areas. Yet, their relatively large size (on average 4000 km2) and extent over both national and international waters, where different legislative frameworks apply, will require the coordinated action by many nations, international organizations and multilateral environmental agreements.

The efficacy of controlled internal drug release (CIDR) in synchronizing the follicular wave in dromedary camels (Camelus dromedarius) during the breeding season

The present study aimed to evaluate the efficacy of controlled internal drug release (CIDR) to synchronize the follicular wave in dromedary camels (Camelus dromedarius) during the breeding season through ovarian monitoring, evaluating sexual receptivity, and measuring progesterone (P4) and estradiol (E2) levels during and after CIDR treatment. Sixteen camels received a new CIDR containing 1.9 g of P4 for 14 days. Ultrasound ovarian monitoring was performed on the day of insertion and every 3 days until the CIDR was withdrawn. Ultrasound examinations were continued day in day out after the CIDR was withdrawn for 10 days. According to the ultrasound examinations, the percentages of camels in the breeding (follicles: 12–18 mm) and nonbreeding phases were calculated. Blood samples were collected day after day during the experimental period (24 days) from the day that the CIDR was inserted. The serum P4 and E2 concentrations were analyzed using ELISA kits. The sexual receptivity of the camels was tested daily during the course of the experiment. The results revealed that 2 and 4 days after the CIDR was withdrawn, the percentage of camels in the breeding phase (68.75% and 75.00%, respectively) was significantly (P < 0.05) higher than that in the nonbreeding phase (31.25% and 25.00%, respectively). The percentage of camels that were abstinent during CIDR treatment was significantly (P < 0.05) higher than that observed for those who were incompletely receptive or completely receptive. The P4 levels increased significantly (P < 0.05) 2 days after CIDR insertion (1.73 ng/mL) and reached maximum values (2.94 ng/mL) at Day 12. Significant (P < 0.05) decreases in the P4 levels were observed 2 to 4 days after CIDR withdrawal (1.01 and 0.80 ng/mL, respectively). The P4 levels reached minimum values (0.18–0.22 ng/mL) at Day 20 through the end of the experiment. The E2 levels differed insignificantly during and after CIDR treatment in dromedary camels. In conclusion, the treatment of dromedary camels with CIDR produced a uniform increase in serum concentrations of P4 that could completely prevent sexual receptivity but could not suppress the follicular wave. After CIDR withdrawal, the P4 levels fell and induced the emergence of a new follicular wave, and most of the camels were in the breeding (ovulatory) phase 2 to 4 days after withdrawal. Therefore, CIDR can be used to synchronize the follicular wave in dromedary camels.

Male convict cichlid 11-ketotestosterone levels throughout the reproductive cycle: an exploratory profile study in laboratory and field populations.

The convict cichlid (Amatitlania nigrofasciata) has been extensively examined in relation to many behavioral topics, such as courtship, pair-bonding, bi-parental care, and territoriality. Recently, this model species has been utilized in studies on genetics, endocrinology, and neuroanatomy, with an ultimate goal of connecting behavior with its underlying mechanisms. The goal of this study was two-fold: (1) profile the circulating levels of plasma 11KT in the male convict cichlid at multiple points during the reproductive cycle and (2) generally compare the hormonal profiles of the widely used laboratory populations and those of a free-living population in the streams of Costa Rica. The results of the field experiment showed that male convict cichlids had higher levels of circulating 11KT during courtship and lower during the parental care and non-breeding phases. The profile of the laboratory population was similar to the profile of the free-living individuals, with significantly higher levels of 11KT occurring during courtship than during parental care, though the level of 11KT during non-breeding phase was elevated in the laboratory. The high levels of 11KT during courtship and low levels of 11KT during parental care found in both the field and the laboratory is similar to what has been reported in other species of teleosts, and may suggest an important function of 11KT in the expression of courtship behavior and the subsequent onset of parental behaviors in this model species.

Seasonal plasticity in the peptide neuronal systems: potential roles of gonadotrophin-releasing hormone, gonadotrophin-inhibiting hormone, neuropeptide Y and vasoactive intestinal peptide in the regulation of the reproductive axis in subtropical Indian weaver birds.

Two experiments examined the expression of gonadotrophin-releasing and inhibiting hormones (GnRH-I, GnRH-II and GnIH), neuropeptide Y (NPY) and vasoactive intestinal peptide (VIP) in subtropical Indian weaver birds, which demonstrate relative photorefractoriness. Experiment 1 measured peptide expression levels in the form of immunoreactive (-IR) cells, percentage cell area and cell optical density in the preoptic area (GnRH-I), midbrain (GnRH-II), paraventricular nucleus (GnIH), mediobasal hypothalamus [dorsomedial hypothalamus (DMH), infundibular complex (INc), NPY and VIP] and lateral septal organ (VIP) during the progressive, breeding, regressive and nonbreeding phases of the annual reproductive cycle. GnRH-I was decreased in the nonbreeding and VIP was increased in INc in the breeding and regressive states. GnRH-II and NPY levels did not differ between the testicular phases. Double-labelled immunohistochemistry (IHC) revealed a close association between the GnRH/GnIH, GnRH/NPY, GnRH/VIP and GnIH/NPY peptide systems, implicating them interacting and playing roles in the reproductive regulation in weaver birds. Experiment 2 further measured these peptide levels in the middle of day and night in weaver birds that were maintained under short days (8 : 16 h light /dark cycle; photosensitive), exposed to ten long days (16 : 8 h light /dark cycle; photostimulated) or maintained for approximately 2 years on a 16 : 8 h light /dark cycle (photorefractory). Reproductively immature testes in these groups precluded the possible effect of an enhanced gonadal feedback on the hypothalamic peptide expression. There were group differences in the GnRH-I (not GnRH-II), GnIH, NPY and VIP immunoreactivity, albeit with variations in immunoreactivity measures in the present study. These results, which are consistent with those reported in birds with relative photorefractoriness, show the distribution and possibly a complex interaction of key neuropeptides in the regulation of the annual reproductive cycle in Indian weaver birds.

Social interactions during the aquatic breeding phase of the family Hynobiidae (Amphibia: Caudata)

Social animals with a monophasic life cycle exhibit a more complex social system for reproduction than that of other social animals in which the life cycle is biphasic. The family Hynobiidae (Amphibia: Caudata) is phylogenetically basal to most other salamander families, practices external fertilization, and has a biphasic life cycle alternating between aquatic breeding and terrestrial nonbreeding phases. There are many controversial and specific social interactions during the aquatic breeding phase in several of the inspected species of this family when comparing their sexual or social behaviors with those of other animal species. Some papers describing these social interactions have misled us by erroneously referring to phenomena of territoriality, chase, amplexus/midwifing, mating ball formation, scramble competition, and parental care. Especially, I am skeptical of the male’s premating displays (e.g., chase, clasp, snout contact, chin rubbing, tail undulation, smelling, digging) regarded as “courtship” in some papers, except for Ranodon sibiricus that may produce a single large spermatophore, because most of these displays result in the female’s escape from the male. Also, I am skeptical of the behavior of a male, staying near deposited egg sacs, regarded as “parental care” because such a male can be predicted to change easily with other males and not to guard eggs or embryos against predators. Thus, I provide a focal review and correct observations on hynobiid sexual and social behavior by incorporating some unignorable descriptions that do not fit with previous descriptions on aquatic social interactions of this family.

Testosterone Affects Song Modulation during Simulated Territorial Intrusions in Male Black Redstarts (Phoenicurus ochruros)

Although it has been suggested that testosterone plays an important role in resource allocation for competitive behavior, details of the interplay between testosterone, territorial aggression and signal plasticity are largely unknown. Therefore, we investigated if testosterone acts specifically on signals that communicate the motivation or ability of individuals to engage in competitive situations in a natural context. We studied the black redstart, a territorial songbird species, during two different life-cycle stages, the early breeding phase in spring and the non-breeding phase in fall. Male territory holders were implanted with the androgen receptor blocker flutamide (Flut) and the aromatase inhibitor letrozole (Let) to inhibit the action of testosterone and its estrogenic metabolites. Controls received a placebo treatment. Three days after implantation birds were challenged with a simulated territorial intrusion (STI). Song was recorded before, during and after the challenge. In spring, both treatment groups increased the number of elements sung in parts of their song in response to the STI. However, Flut/Let-implanted males reacted to the STI with a decreased maximum acoustic frequency of one song part, while placebo-implanted males did not. Instead, placebo-implanted males sang the atonal part of their song with a broader frequency range. Furthermore, placebo-, but not Flut/Let-implanted males, sang shorter songs with shorter pauses between parts in the STIs. During simulated intrusions in fall, when testosterone levels are naturally low in this species, males of both treatment groups sang similar to Flut/Let-implanted males during breeding. The results suggest that song sung during a territorial encounter is of higher competitive value than song sung in an undisturbed situation and may, therefore, convey information about the motivation or quality of the territory holder. We conclude that testosterone facilitates context-dependent changes in song structures that may be honest signals of male quality in black redstarts.

Year-round territorial aggression is independent of plasma DHEA in the European nuthatch Sitta europaea

Plasma testosterone can play an important role in promoting aggressive behaviors relating to territory defense in breeding male birds. Some birds defend territories also during the non-breeding phase, when testosterone circulates at basal levels. In such species, plasma levels of the pro-hormone dehydroepiandrosterone (DHEA) may support non-breeding territoriality by acting as a local substrate for sex steroids. To test this possible role of plasma DHEA, we examined the seasonal DHEA profile of male (and female) European nuthatches Sitta europaea: a male and female nuthatch pair will defend an all-purpose territory throughout the year. We hypothesized that plasma DHEA would be detectable in wintering nuthatches with a territory. However, only ca. half of the territorial wintering males (and females) displayed detectable DHEA levels, suggesting that plasma DHEA is not a major sex steroid precursor during non-breeding. Further, among hatching-year birds, plasma DHEA was significantly lower in territorial birds than in “floaters”, i.e., subordinate birds without a territory. To experimentally examine the role of DHEA in non-breeding territoriality, we treated adult wintering males with DHEA and measured effects on aggressive responses to conspecific challenge. DHEA treatment elevated plasma levels of DHEA (and testosterone), but did not enhance territorial behaviors or their persistence. Taken together, our data suggest that DHEA (and, indeed, sex steroids per se) do not regulate non-breeding territoriality in the nuthatch. Given that territorial aggression in nuthatches is expressed year-round, a hormone for its activation may be redundant.

Seasonal histophysiological study of the pineal gland in relation to gonadal and adrenal gland activities in adult domestic pigeon, Columba livia Gmelin

Some aspects of physiology related to the pineal gland in the adult male domestic pigeon, Columba livia Gmelin have been investigated. It was also correlated with the activity of the gonadal and adrenal glands by changing environmental conditions (e.g., seasonal photoperiods, temperature, humidity and rainfall). The maximum daily temperature was noticed in April and minimum in January, 2003. Pineal gland weights showed significant (F = 52.04, P < 0.01) annual variations with a maximum relative weight of the pineal gland being recorded in the month of July, when testicular relative weight was minimum. Testis and adrenal gland weights showed significant (F = 144.31, P < 0.01; F = 106.36, P < 0.01 respectively) annual variations with a maximum relative adrenal weight being recorded in the month of April, when testicular relative weight reaches a maximum value. Besides, assessment of pineal in relation to seasonal activity showed a completely inverse relationship with gonadal and adrenal gland. During the months of June–August and November–January, the testis remained in a state of atrophy. The rise in temperature contributed to rise in adrenal-gonadal function and reduced pineal function. Testicular weight peaked in March, April and May when the longest days and the highest temperatures prevailed and humidity was moderately low. A second testicular weight peak was also noticed in September and October when the temperature was also moderately high. These observations have been interpreted to suggest that two breeding and two nonbreeding phases are existed in the animal. Ultra structural study of the pineal gland and adrenocortical tissue indicate some features related to the breeding phase of pigeons. Within the pineal gland, mitochondria, dense cored vesicle with material and lipid droplets were found to be maximal within the pinealocyte cell cytoplasm of the regressive phase-I than the primary breeding phase. Golgi body and lysosomes were well defined. Furthermore, rough endoplasmic reticulum sacs were enlarged in size in the regressive phase-I. On the other hand, the number of mitochondria and cytoplasmic secretory granules within both the SCZ and CZ of the adrenocortical regions were found to be maximum during the primary breeding phase than the regressive phase-I. Extensive rough endoplasmic reticulum was found in the cytoplasm also. Furthermore, Golgi complex was enlarged within the breeding season.

Extinction Risk: A Comparative Analysis of Central Asian Vertebrates

In 2004, IUCN listed 20% of all mammals, 12% of birds and 4% of reptiles as threatened with extinction. Why are these species, but not the others in their clades, at risk? Most comparative studies of Red List status to date have investigated the relationship between status and life history or ecology, either at a local level where species face a given situation which may be known in detail, or at a global level where threats are much more heterogeneous. The use of data at a sub-global level raises several issues, including the need to assess populations across geopolitical borders and how best to treat non-breeding phases of populations. However, regional-level data provide the opportunity to look in more detail at how threatening processes operate. We employ comparative analysis using phylogenetically independent contrasts and multiple regression to control for inter-related and confounding independent variables, to evaluate correlates of regional threat for three groups of central Asian vertebrates. We find that aspects of dispersal, area of occupancy, body mass and generation time are important in predicting the perceived risk of regional extinction.

Seasonal changes in the seminiferous epithelium of rhesus and bonnet monkeys.

With a view to elucidate seasonal variations in testicular spermatogenesis, quantitative analysis of spermatogenic cells was carried out in non-human primate species viz. rhesus (Macaca mulatta) and bonnet (M. radiata) monkeys during breeding (October-December) and non-breeding (May-June) seasons. The results revealed significant inhibition of testicular germ cell population during non-breeding compared with the breeding period in both the species. Quantitative determination of Sertoli cell-germ cell ratio showed a marked decrease in the number of type A-spermatogonia, spermatocytes (non-pachytene and pachytene) and spermatids (in steps 1-12 of spermiogenesis) in rhesus monkey during the non-breeding period. Bonnet monkeys exhibited the significant decline in the number of primary spermatocytes and spermatids during the non-breeding phase. In addition, average diameter of round seminiferous tubules and nuclear diameter of Leydig cells also decreased significantly in rhesus monkeys. However, bonnet monkeys did not show any significant change in nuclear diameter/morphology of Leydig cells, testicular tubular diameter and number of type A-spermatogoniae. Sertoli cell number did not show any significant change during both breeding and non-breeding periods in both the species. The results of this study indicate a prominent seasonal variation in testicular spermatogenic/Leydig cells in rhesus monkeys than those observed in bonnet monkeys.