Annual Reproductive Cycle Research Articles

Seasonal changes of biological condition and reproductive cycle of hampback shrimp <i>Pandalus hypsinotus</i> (Caridea, Pandalidae) in the Tatar Strait

Research and commercial trawl catches of humpback shrimp Pandalus hypsinotus from the Tatar Strait (Japan Sea) in 2004–2020 were investigated, with bioanalysis of about 45 thousand specimens. Average timing of group molting, spawning, and eggs laying are determined, terms of gonads and eggs development are estimated. Prespawning and molting of the females occur between January-April, with the peaks in early February and middle February, respectively. All oviparous females have 30–40 days to lay eggs, and molt during 50–55 days; the peak of the eggs laying occurs in late June. The males molt in July-August, afterwards the largest individuals change gender and new intersexes are formed. The males have the second molting in October-December, with the peak in late November. In January, after finish of the males molting, a new annual reproduction cycle starts from the prespawning molting of females. Both vitellogenesis and embryogenesis are observed through the year, though females with developing gonads prevail from August to January (because of a long time span between winter and summer moltings while the egg carrying continued 15 months) but oviparous females — from February to July. The individual reproductive cycle of Pandalus hypsinotus in the Tatar Strait lasts 24 months, with 9 months of vitellogenesis (quick growth of gonads) and 15 months of embryogenesis. During the 2-year reproductive cycle, most of females pass through the following stages: i) gonads development (just after eggs laying) when almost all oviparous females (up to 95 % in May) have green gonads under carapace that corresponds to the stage of development «eggs laid — gonads weakly developed»; ii) summer molting from August when females lose hairs on pleopods and the gonads growth accelerates; iii) respawning in January-March (together with the firstly spawning intersexes, with slight delay of the latter); iv) initial developing of eggs during summer; v) stage of «eyed eggs» from December to March; and vi) eggs laying and molting from late March to late May; then the 2-year reproductive cycle repeats.

Seasonally Related Disruption of Metabolism by Environmental Contaminants in Male Goldfish (Carassius auratus).

Endocrine disrupting chemicals mimic or disrupt action of the natural hormones, adversely impacting hormonal function as well as cardiovascular, reproductive, and metabolic health. Goldfish are seasonal breeders with an annual reproductive cycle regulated by neuroendocrine signaling which involves allocation of metabolic energy to sustain growth and reproduction. We hypothesize that seasonal changes in physiology alter overall vulnerability of goldfish to metabolic perturbation induced by environmental contaminants. In this study, we assess effects of endogenous hormones, individual contaminants and their mixture on metabolism of goldfish at different reproductive stages. Exposure effects were assessed using 1H-NMR metabolomics profiling of male goldfish midbrain, gonad and liver harvested during early recrudescence (October), mid-recrudescence (February) and late recrudescence (June). Compounds assessed include bisphenol A, nonylphenol, bis(2-ethylhexyl) phthalate, fucosterol and a tertiary mixture (DEHP + NP + FS). Metabolome-level responses induced by contaminant exposure across tissues and seasons were benchmarked against responses induced by 17β-estradiol, testosterone and thyroid hormone (T3). We observe a clear seasonal dependence to metabolome-level alteration induced by hormone or contaminant exposures, with February (mid-recrudescence) the stage at which male goldfish are most vulnerable to metabolic perturbation. Responses induced by contaminant exposures differed from those induced by the natural hormones in a season-specific manner. Exposure to the tertiary mixture induced a functional gain at the level of biochemical pathways modeling over responses induced by individual components in select tissues and seasons. We demonstrate the importance of seasonally driven changes in physiology altering overall vulnerability of goldfish to metabolic perturbation induced by environmental contaminants, the relevance of which likely extends to other seasonally-breeding species.

The dynamics of the liver weight and liver indices in the course of gonad maturation of gadid species on Eastern Kamchatka

Longterm data on the liver weight, hepatosomatic (HSI) and gonadosomatic (GSI) indices of walleye pollock, Pacific cod and saffron cod are analyzed on Eastern Kamchatka in seasonal aspect and in the course of gonad maturation. Individual values of the indices extensively vary and depend on the fish body length, season and stage of gonad maturity. The dynamics of the HSI is agree to the dynamics of the GSI during the year and depending on gonad maturity. The maximum values of the HSI are typical for walleye pollock and Pacific cod individuals with the gonads of the III stage of maturity. The maximum values of the index in saffron cod are found in mature individuals with immature gonads. The minimum values are demonstrated by the fish with the gonads at the stage of final spawning or of post-spawning recovery. During the annual reproduction cycle males and females of walleye pollock and cod realize different scenarios of spending and accumulating liver fat. Whereas the maximum HSI is observed in the fish with the gonads at the III maturity stage, the minimum values in males are typical for individuals with smelting gonads, and in females – on finishing the spawn. That can be connected to possible feeding for the individual. Liver weight and liver index can increase in males just shortly after finishing spawning, in females that is found only at the stage of post-spawning recovery.

Fatty Acid Profile and Proximate Composition of Gonads from Wild Echinometra vanbrunti during an Annual Cycle: Suitability for Human Consumption

ABSTRACT Human consumption of sea urchin gonads has led to overexploitation of commercial species, and the search for new marketable species to promote the recovery of exploited populations. Echinometra vanbrunti is a promising candidate for commercial exploitation. Its annual reproductive cycle has an effect on the proximate composition of the gonads; if they were to be consumed, the best quality in biochemical composition was determined to be from December to May, when nutritive phagocytes uphold the highest contents of protein and lipid. They possess considerable levels of omega-3 essential fatty acids, predominantly eicosapentaenoic and docosahexaenoic (DHA) acids, quite important for human nutrition. A subtle trend of higher DHA levels during the growing, premature, and mature gonadal stages of females and males was observed, though it is strongly influenced by diet and environment. A program to protect and regulate the sustainable extraction needs to be put in place before commercial exploitation.

Reproduction and Maturation of Sea Bass, Lateolabrax japonicus, after Transportation from Net-Cages to Indoor Tanks.

To determine whether the reproductive processes of sea bass, Lateolabrax japonicus, proceed normally after transportation from an outdoor net-cage into indoor tanks, we examined changes in the gonadosomatic index (GSI), histological gonadal tissue, and plasma levels of sex hormones (testosterone and estradiol-17ß) during their annual reproductive cycle. We also measured maturation and spawning across two sea water salinity levels (full and low salinity). Fecundity was estimated by the relationship between egg number and body size in female sea bass. Monthly changes in the GSI, histological gonadal tissues, and oocyte size showed both male and female sea bass reach final maturation in January and February, respectively, indicating that the spermiation of males occurs earlier than the spawning of females. The histological results indicated that the sea bass is a multiple spawner, similar to many marine teleosts, exhibiting group-synchronous oocyte development. Female maturation and spawning were enhanced in lower salinity seawater (29.6-31.0 psu) compared to that of normal salinity (34.5-35.1 psu). These results confirm that sea bass reproduction can occur successfully in captivity and imply that fertilized eggs can be collected from February to March. Additionally, our results show that lower salinity enhances oocyte maturation and spawning of female sea bass.

Reproductive biology and annual reproductive cycles of two sympatric lineages of Bostrychus sinensis with a natural habitat on southeastern coast of China

The two phylogeographic lineages [South China Sea (SCS) lineage and East China Sea (ESC) lineage] of the four-eyed sleeper (Bostrychus sinensis) occur sympatrically along the southeastern coast of China, where there is a small percentage of hybrids in a natural habitat. To assess the mechanism responsible for the incomplete reproductive isolation between the SCS and ECS lineages of four-eyed sleeper, there was sampling of individuals from the Yueqing Bay from November 2018 to November 2019 to determine whether there are differences in characteristics of the reproductive cycles and reproductive biology. The two lineages varied in reproductive seasonality, body size and shape, and egg number. The SCS lineage spawned annually between May and August, with the absolute fecundity (AF) of the SCS lineage being 9960 to 39,517 eggs per female, and there was positive allometric growth of this species. The ECS lineage spawned annually between June and July, with females producing 4064 to 10,370 eggs per fish and individuals having an isometric growth pattern. Preliminary results indicated that there was partial overlap in the spawning season between the two lineages in the sympatric region, which may not be a primary factor in the incomplete reproductive isolation. Furthermore, the lineage differences in fecundity and body shape and size may lead to variation in mate choice and reproductive strategy. The results from this study provide insight into the biology, reproductive strategies, and speciation of the four-eyed sleepers.

Transcriptome Profiling of the Pacific Oyster Crassostrea gigas Visceral Ganglia over a Reproduction Cycle Identifies Novel Regulatory Peptides.

The neuropeptides involved in the regulation of reproduction in the Pacific oyster (Crassostrea gigas) are quite diverse. To investigate this diversity, a transcriptomic survey of the visceral ganglia (VG) was carried out over an annual reproductive cycle. RNA-seq data from 26 samples corresponding to VG at different stages of reproduction were de novo assembled to generate a specific reference transcriptome of the oyster nervous system and used to identify differentially expressed transcripts. Transcriptome mining led to the identification of novel neuropeptide precursors (NPPs) related to the bilaterian Eclosion Hormone (EH), crustacean female sex hormone/Interleukin 17, Nesfatin, neuroparsin/IGFBP, prokineticins, and urotensin I; to the protostome GNQQN, pleurin, prohormones 3 and 4, prothoracotropic hormones (PTTH), and QSamide/PXXXamide; to the lophotrochozoan CCWamide, CLCCY, HFAamide, and LXRX; and to the mollusk-specific NPPs CCCGS, clionin, FYFY, GNamide, GRWRN, GSWN, GWE, IWMPxxGYxx, LXRYamide, RTLFamide, SLRFamide, and WGAGamide. Among the complete repertoire of NPPs, no sex-biased expression was observed. However, 25 NPPs displayed reproduction stage-specific expression, supporting their involvement in the control of gametogenesis or associated metabolisms.

Seasonal changes and endocrine regulation of gonadal development in hatchery-produced Pacific bluefin tuna Thunnus orientalis broodstock in sea cages

We examined the annual reproductive cycle of both female and male hatchery-produced Pacific bluefin tuna (PBT, Thunnus orientalis) broodstock at 3 years of age, including the associated changes in plasma levels of sex steroid hormones and the gene expression of key endocrine factors. The females progressed to vitellogenesis in April, and approximately 50% of the females were observed in late vitellogenesis between June and July at water temperatures between 24.1 °C and 29.0 °C. Approximately 90% of the males were in spermiation for at least 7 months between April and October, which included the period when vitellogenic females were present. Furthermore, the gonadosomatic index of both females and males peaked between June and July. These results indicate that the reproductive season of hatchery-produced PBT peaks between June and July, which is in agreement with the reproductive season reported for PBT broodstock originating from wild-caught juveniles. Furthermore, the percentage of hatchery-reared females that reached late vitellogenesis in the present study was higher than that in wild-caught captive-reared females reported in previous literature. Analysis of plasma sex steroid levels and gene expression profiles suggested that oocyte and ovarian development were associated with 17β-estradiol (E2) control, whereas spermatogonial differentiation towards meiosis seemed to be mediated by 11-ketotestosterone (11-KT). Furthermore, the production of E2 and 11-KT is likely regulated by luteinizing hormone and follicle-stimulating hormone, respectively, via their related receptors. The findings of this study are expected to contribute to improvements of technologies for obtaining fertilized eggs from hatchery-produced PBT broodstock.

Field study reveals morphological and neuroendocrine correlates of seasonal breeding in female water voles, Arvicola terrestris

Seasonally breeding mammals display timely physiological switches between reproductive activity and sexual rest, which ensure synchronisation of births at the most favourable time of the year. These switches correlate with seasonal changes along the hypothalamo-pituitary–gonadal axis, but they are primarily orchestrated at the hypothalamic level through environmental control of KISS1-dependent GnRH release. Our field study shows that births of fossorial water voles, Arvicola terrestris, are concentrated between March and October, which indicates the existence of an annual reproductive cycle in this species. Monthly field monitoring for over a year further reveals dramatic seasonal changes in the morphology of the ovary, uterus and lateral scent glands, which correlate with the reproductive status. Finally, we demonstrate seasonal variation in kisspeptin expression within the hypothalamic arcuate nucleus. Altogether, this study demonstrates a marked rhythm of seasonal breeding in the water vole and we speculate that this is governed by seasonal changes in photoperiod.

Ecological variation among island foxes relative to reproductive events

Ecological attributes of a species can vary as resource requirements and social interactions change in response to the annual reproductive cycle. We examined variation in home range size, home range overlap, activity (2005–2006), and food item selection (2006–2007) of island foxes (Urocyon littoralis) on San Nicolas Island relative to reproduction-related events. Home ranges, particularly for males, were larger during the mating period compared with the post-mating, pup-rearing, and non-reproduction periods. Home range overlap with non-mate neighbors also increased during the mating period. The greater home range size and overlap during the mating season is consistent with foxes, particularly males, traveling into the ranges of neighboring pairs in an attempt to secure extra-pair copulations. Daily activity patterns did not vary among the reproductive periods. Use of vertebrate prey items increased during the period when adults would have been provisioning weaning young. These items (e.g., mice, birds, lizards) are protein-rich and easier to transport compared with smaller items (e.g., fruits, snails, insects) that also are commonly consumed by island foxes. Variation in ecological attributes among island foxes across the different seasons defined by reproductive events likely represents efforts to maximize mating opportunities, particularly among adult males, and to secure optimal resources for provisioning growing young. These patterns are consistent with those observed among other small canid species.

Testicular maturation of thin-lipped grey mullet during the annual reproductive cycle in captivity

ABSTRACTIntroduction: Continuous maintenance of mullet broodstock in captivity and the control of testicular development are important, particularly when linked to mass propagation of juveniles in the hatcheries, however, the complete description of testes maturation still lacking.Aim of the work: The main goal of our study to present a complete description for the testes and the obtaining of mature thin-lipped mullet, Liza ramada, males suitable for breeding in captivity.Material and methods: We performed morphological and histological techniques to describe the testicular cycle of developmental stages of male mullet reared in freshwater and captivity. Results: In general, the testes of L. ramada exhibit remarkable seasonal variations in shape, size, color and texture. Indeed, five developmental stages were characterized during testicular cycle in L. ramada in freshwater based on the histomorphology and gonadosomatic index. These stages include immature testis, stimulating spermatogenesis, rapid spermatogenesis, mature (ripe) testis and spawning (running) testis. Importantly, the testis development started when the day length and water temperature begun to decrease in September while the gradual decrease in both photoperiod and water temperatures ensure complete gonad maturation (September-December). However, induction of successful spawning in L. ramada occurs when photoperiod and water temperatures decline to their minimum values during December.Conclusion: The present study provides the morphological and histological description for testes of L. ramada during gonad maturaion in captivity and able to obtain a ripe mullet male suitable for hormonal induced reproduction in these species especially in captivity. In spite of attaining the ripe stage of L. ramada males in freshwater, the spawning can only possible with hormonal and environmental stimulation.

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.

Seasonal Dynamics of the Honey Bee Gut Microbiota in Colonies Under Subtropical Climate : Seasonal Dynamics of Honey Bee Gut Microbiota.

Honey bees (Apis mellifera) provide invaluable benefits for food production and maintenance of biodiversity of natural environments through pollination. They are widely spread across the world, being adapted to different climatic conditions. To survive the winter in cold temperate regions, honey bees developed different strategies including storage of honey and pollen, confinement of individuals during the winter, and an annual cycle of colony growth and reproduction. Under these conditions, winter honey bees experience physiological changes, including changes in immunity and the composition of honey bee gut microbiota. However, under tropical or subtropical climates, the life cycle can experience alterations, i.e., queens lay eggs during almost all the year and new honey bees emerge constantly. In the present study, we characterized nurses' honey bee gut microbiota in colonies under subtropical region through a year, combining qPCR, PCR-DGGE, and 16S rDNA high-throughput sequencing. We also identified environmental variables involved in those changes. Our results showed that under the mentioned conditions, the number of bacteria is stable throughout the year. Diversity of gut microbiota is higher in spring and lower in summer and winter. Gradual changes in compositions occur between seasons: Lactobacillus spp. predominate in spring while Gilliamella apicola and Snodgrasella alvi predominate in summer and winter. Environmental variables (mainly precipitations) affected the composition of the honey bee gutmicrobiota. Our findings provide new insights into the dynamics of honey bee gut microbiota and may be useful to understand the adaptation of bees to different environmental conditions.

Intracytoplasmic sperm injection versus conventional IVF

Intracytoplasmic sperm injection is a widely used fertilisation method that involves injecting a single spermatozoon into oocyte cytoplasm using a glass micropipette.1 Although it was introduced as a modification of conventional in-vitro fertilisation (IVF) to overcome severe male factor infertility,2 intracytoplasmic sperm injection has become the most common laboratory technique in assisted reproductive technology, accounting for almost 70% of the around 2·8 million annual assisted reproductive technology cycles, according to global estimates.

Accumulation of a bitter amino acid, pulcherrimine, in sea urchin ovaries and its relevance to the annual reproductive cycle

Hemicentrotus pulcherrimus in the Tohoku area is not utilized as a fishery product because the ovaries have a bitter taste almost all year. To discover the cause, we compared the annual reproductive cycles and ovarian accumulation of a bitter amino acid, pulcherrimine, in H. pulcherrimus collected at Mikuni (Fukui Prefecture), where it is fished in summer, and Iwaki (Fukushima Prefecture), where it is not utilized. At both sites, pulcherrimine increased in maturing ovaries as oogenesis proceeded from autumn to winter, decreased after spawning in spring, but remained in spent and immature ovaries for a few months. In Mikuni, pulcherrimine was scarcely detected in the ovaries for several months in summer. However, in Iwaki, late spawning delayed the disappearance of pulcherrimine in summer, and early initiation of oogenesis advanced the restart of pulcherrimine accumulation in autumn compared to Mikuni. Consequently, the period when the ovaries were palatable because of the absence of pulcherrimine during summer was short in Iwaki. The major cause of such short-term palatability could be the lower seawater temperature in the Tohoku area. Furthermore, pulcherrimine was never detected in other sea urchins, although a bitter taste was found in the mature ovaries of some species.

The process of testicular regression also impacts the physiology of the epididymis of the bat Molossus molossus, although with a delay in epididymal response due to sperm storage

Responsible for post-testicular maturation, concentration, protection and sperm storage, the epididymis is an organ that can be easily subdivided into three segments: caput, corpus and cauda. Each epididymal region displays different morphology and functions within the sperm maturation process. Despite the great importance of this organ, studies on its morphology and hormonal control in bats remain scarce. Thus, the aim of this study was to morphologically analyze the epididymis of the bat Molossus molossus (Chiroptera: Molossidae), in order to evaluate its morphological and morphometric variations, as well as some aspects of its hormonal control during the annual reproductive cycle. For this purpose, 60 sexually adult males were used in this study, comprising five specimens collected monthly for one year to form 12 sample groups. The epididymis was subjected to morphological, morphometric and immunohistochemical analyses. The results demonstrated that the processes of total testicular regression and posterior recrudescence suffered by M. molossus also impacts the physiology of the epididymis, however, a delay in the epididymal response is seen due to the storage of sperm. Similar to other mammals, the epididymis of M. molossus has a large predominance of principal and basal cells. The epididymal seasonal variations appear to be directly correlated to rainfall and photoperiod, but not to temperature. Meanwhile, epididymal physiology appears to be regulated, at least partially, by the expression of the androgen receptor in epithelial cells, which has agonist effects on cell proliferation.

Ecological and reproductive characteristics of holothuroids Isostichopus badionotus and Isostichopus sp. in Colombia.

Isostichopus badionotus and Isostichopus sp. are two holothuroids exploited in the Caribbean region of Colombia. Until recently, they were considered a single species. During one year, 222 individuals of Isostichopus sp. and 114 of I. badionotus were collected in two bays of the Santa Marta region to study their reproductive biology and collect information on their size, weight and habitat. Both sea cucumber morphotypes showed an annual reproductive cycle, with a reproductive season from September to November, closely related to the increase in water temperature and rainfall. In both sea cucumbers the population structure exhibited a unimodal distribution composed of mature individuals and a sex ratio of 1:1. Isostichopus sp. had an average size and weight (193 ± 52 mm and 178 ± 69 g) and size and weight at first maturity (175 mm and 155 g) that was much lower than I. badionotus (respectively, 324 ± 70 mm and 628 ± 179 g; 220 mm and 348 g). While 98% of Isostichopus sp. individuals were collected in the upper 2.5 m, on rocky bottoms between cracks, 73% of I. badionotus individuals were found between 3 and 7.8 m depth, exposed on sandy bottoms. These differences imply that management measures (e.g. minimum catch size) should not be the same for both sea cucumbers morphotypes.

Reproductive biology of female sawcheek scorpionfish, Brachypterois serrulata (Richardson, 1846) (Teleostei; Scorpaenidae) from Visakhapatnam Coast, India.

We examined the reproductive biology of sawcheek scorpionfish, Brachypterois serrulata, collected from Visakhapatnam fish landing center (fishing area covered 16.98°-20.20°N, 82.19°-86.53°E). We studied the annual reproductive cycle, fecundity, size at first maturity, mode of spawning with periodical changes and histological preparations. Size distribution and size at sexual maturity were calculated as 108mm TL for females. The mean gonado somatic index values of female increased rapidly from January to December, and reached its peak during January and February. The fecundity of the fish species is determined by the size and weight of the individuals. The fecundity varied from 1896 to 20,488, with an average of 5721.90 ova.

Latitudinal variation in arrival and breeding phenology of the pied flycatcher Ficedula hypoleuca using large‐scale citizen science data

Many species have advanced the timing of annual reproductive cycles in response to climatic warming, sometimes leading to asynchrony between trophic levels, with negative population consequences. Long‐distance migratory birds, reliant on short seasonal food pulses for breeding, are considered particularly susceptible to such disjunction because late arrival may preclude optimal timing of egg‐laying. It is unknown whether the relative timing of arrival and egg‐laying is sufficiently plastic, in time and space, to enable an adaptive response when arrival times change relative to local food resources. We used citizen science data, describing pied flycatcher Ficedula hypoleuca arrival and egg‐laying dates, to explore temporal (2013–2016) and spatial (across Great Britain) variation in the phenology of arrival, laying and their difference. To assess the long‐term trend in arrival and laying at a single location, we used data from a long‐term field study. The arrival‐laying interval was consistently shorter in the north, driven by the contrast between spatial variation in arrival date and spatial invariance in laying date. To understand whether a short arrival‐laying interval may have consequences for productivity, we assessed the association between this interval and clutch size. We found no statistically significant correlation between these two variables. To examine long‐term changes in arrival and laying dates, we focussed on a single location in southwestern England. Both dates of first male arrival and first egg laid in a season advanced since 1986, with no evidence of interval shortening. Together, our results demonstrate spatial and annual variation in the arrival‐laying interval, with no detected effect on fecundity. Thus, the interval from arrival to laying is likely dictated by spatially and temporally varying local conditions, suggesting these migrant birds may have the ability to adapt this interval to align with local conditions and mitigate potential mismatch impacts.

Evaluation of factors inducing variability of faecal nutrients in captive red deer under variable demands

Based on the assumption that dietary and faecal nitrogen correlate, the number of studies using faecal samples collected in the wild to understand diet selection by wild herbivores and other ecological patterns has been growing during the last years, especially due to the recent development of cheap tools for analysis of nutrients like Near-Infrared Reflectance Spectroscopy (NIRS). Within the annual reproductive cycle, cervids (members of the family Cervidae) face strong seasonal variations in nutritional demands, different for hinds (gestation and lactation) and stags (antler growth) and reflected in differential patterns of seasonal diet selection. In this study we aimed to quantify how pasture availability, season and individual factors like sex, age, reproductive status, body mass and body condition affect faecal nutrients in captive red deer with the goal of understanding how these factors may influence the interpretation of results from samples obtained in the wild with little or no information about the animals who dropped those faeces. We used NIRS for analysing nitrogen, neutral and acid detergent fibres in faeces. The relative influence of some individual factors like pregnancy was low (around 4%), while age and weight may induce a variability up to 18%. The presence or absence of pasture contributed to a variability around 13%, while the season contributed to an average variability around 17% (and up to 21% in certain situations). This high variability in faecal nutrients was observed in a controlled setting with captive animals and controlled diets. Thus, in natural situations we suspect that there would be even greater variation. According to the results, we recommend that preliminary research with captive animals of the species of interest should be conducted before collecting samples in the wild, which should help in the interpretation of results.