Annual Reproductive Cycle Research Articles

Quantitative assessment of egg maturation in the horse clam Tresus keenae (Kuroda & Habae 1950) from the south coast of Korea using indirect enzyme-linked immunosorbent assay (ELISA)

The quantity of eggs produced in an annual reproductive cycle of some commercially important shellfish is vital in a hatchery operation or managing the wild populations. The horse clam Tresus keenae (Kuroda & Habe, 1950) is one of the aquaculture candidate bivalve species occurring on the subtidal soft bottom of the coastal Northwest Pacific ocean, while their reproductive effort is yet to be determined. Unlike fishes, assessing the reproductive effort of a marine bivalve is challenging since most species do not have a separable gonad except scallops, as ovaries or testis are inseparable from the visceral mass. Therefore, we developed an indirect enzyme-linked immunosorbent assay (ELISA) to measure the quantity of the egg produced in an annual reproductive cycle. The rabbit anti-egg protein IgG developed in this study was sensitive enough to detect as little as 0.3 μg/ml of the egg protein in indirect ELISA. The horse clam produced as much as 41.1% of the total body weight as eggs during spawning in October, equivalent to 378.2 million mature eggs. Histology revealed that T. keenae has a short resting period in January and February and a long period of gonial mitosis from March to August. The annual reproductive cycle and reproductive capacity of T. keenae estimated in this study provide crucial information in the successful hatchery operation to develop the horse clam aquaculture and manage the wild population for sustainable exploitation.

Seasonal changes in the reproductive cycle and condition index of the surf clam Mactra stultorum (Mollusca: Bivalvia) in the Gulf of Gabes, Tunisia

The reproductive biology of Mactra stultorum from the Gulf of Gabes was investigated monthly during a oneyear period (2017). This study is the first study examining its reproductive biology during one-year in the south of Tunisia. The overall samples presented a balanced sex ratio, with males dominating among smaller individuals (< 22 mm) and females predominating in larger size classes (> 34 mm). The obtained total sex ratio (F:M) was equal to 1.03:1. The size at first maturity (SL50%) was 20.43 and 22.10 mm for males and females, respectively. The seasonal variations assessed through macro- and microscopic characteristics in the gonads of both sexes indicated a clearly defined annual reproductive cycle with a principal spawning peak during summer and a resting period during December and January. The reproduction of M. stultorum was strongly influenced by fluctuations in the seawater temperature, as reflected through the temporal variation in the gonadal cycle, condition index (CI) and tissue weight rate (TiWR). If managed properly, M. stultorum is expected to meet the domestic market demand through artisanal fishery. The adoption and implementation of rules, such as limiting the size of clams, is required to protect this new exploitable fishery resource.

Reproductive toxicity of bisphenol A, at environmentally relevant concentrations, on ovarian redox balance, maturational response, and intra-oocyte signalling events in Labeo bata

Bisphenol A (BPA) is a widely used plastic monomer that potentially interferes with ovarian neuroendocrine, endocrine, and autocrine/paracrine factors, causing reproductive dysfunction. However, the influence of BPA on redox balance, estrogen receptor (ER) expression vis-à-vis meiotic cell cycle progression, and intra-oocyte signalling events has not been extensively investigated. The present study examines the impact of BPA on reproductive toxicity in female Labeo bata (Order Cypriniformes, Family Cyprinidae), a freshwater teleost preferred as a food fish in the Indian subcontinent. Our results show that while ovarian weight (gonadosomatic index, GSI) and dynamics of follicular growth undergo pronounced changes during the annual reproductive cycle, chronic BPA exposure at environmentally relevant concentrations promotes follicular atresia concomitant with reduced GSI during the spawning phase, the highest response being observed due to low-dose (0.1 μg/L, 0.438 nM) BPA exposure in vivo. Furthermore, BPA perturbation of ovarian StAR expression and ERα/ERβ homeostasis corroborates with elevated oxidative stress in BPA-treated ovary, FG follicles, and follicular cells. A sharp increase in ROS accumulation and nitric oxide (NO) levels in BPA-treated full-grown (FG) follicles coupled with loss of redox balance, elevated follicular cell death, and activation of apoptotic markers (caspase -8, -9, -3, Bax) indicate poor oocyte health and reproductive toxicity. Importantly, maturational steroid (MIS, 17,20β-P)-induced cyclin B-p34cdc2 activation and elevated GVBD (germinal vesicle breakdown) response require protein kinase A (PKA) inhibition and participation of Mos/MAPK- and cdc25-mediated signalling events. While the adenylate cyclase activator forskolin (FK) abrogates, priming with a PKA inhibitor (H89) promotes the meiotic G2-M1 transition, confirming the role of PKA in meiotic cell cycle progression in this species. Furthermore, the negative influence of BPA priming on 17,20β-P-induced oocyte maturation involves elevated PKAc phosphorylation (activation) and significant alteration in Mos/MAPK signalling, indicating derailed meiotic maturational competence and disrupted oocyte quality.

Spatial and temporal patterns of gonadal maturation and spawning in European flounder Platichthys flesus at its southern continental edge

The European flounder (Platichthys flesus) is a marine flatfish with high plasticity in several life-history traits, including spawning sites and habitat use patterns. With the overarching goal of understanding the use of estuaries in connection with maturation and reproduction in adult flounder, this study investigates its reproductive cycle in the Douro Estuary (NW Portugal), at the southern edge of its geographical distribution. Adults were caught by monthly trawling from November 2016 to November 2017. Sex ratio and length-weight relationships were determined. The annual reproductive cycle was described using a combination of gonadosomatic (GSI), hepatosomatic (HSI), and general fish condition (Kn) indices, seasonal gonad development staging (macroscopic and histological), and quantification of plasma sexual steroids. Total sex ratio was 1 M:3 F, and females presented negative allometric growth, while males’ growth was isometric. The various indices consistently indicated that the greatest reproductive activity occurred between January and March, peaking in February. However, some females at advanced reproductive stages (late vitellogenesis), high GSI values and steroid hormone (E2) levels were observed as late as May. Females in spawning condition, i.e., undergoing full oocyte maturation and ovulation, were never found, unlike males who exhibited spermiation within the estuary. Sexual differences in migration patterns were also suggested: males seem to leave earlier and stay longer in offshore spawning grounds, while females return to the estuary shortly after spawning. Overall, there was a good correlation between GSI, seasonal hormone cycling, and sexual maturity of female and male flounder, supporting the use of circulating sex steroids as a less invasive tool to assess maturity status.

Genetic associations of ewe body condition score and lamb rearing performance in extensively managed meat sheep

Many small ruminant production systems are relatively low input and rely heavily on animals grazing pastures often in extensive and harsh environmental conditions, unsuitable for any other type of agriculture. New breeding goal traits for lifetime resilience for maternal sheep breeding programmes have been investigated, focusing on body tissue mobilisation phenotypes and their genetic relationships with maternal production traits. Performance records of 8,355 Scottish Blackface ewes, from 2 extensively reared hill sheep flocks, collected over a 20-year period, were used to quantify relationships between body condition score (BCS) and the ewe's ability to successfully rear lambs. Between 14,000 and 25,000 data records per trait were available, measured across the annual sheep reproductive cycle. The pedigree file used for the analyses included sire and dam information for 50,207 animals. Most heritability estimates for the BCS traits - measured at key time points within the annual production cycle, or considering BCS changes between time points - were low, but significantly different from zero, ranging between 0.07 and 0.17. The heritability estimate for the number of lambs at pregnancy scanning was 0.09. Heritabilities for foetal loss from pregnancy scanning to lambing, lamb loss from lambing to weaning and number of lambs weaned were 0.02, 0.02 and 0.06, respectively. These estimates indicate that genetic control over the reproductive and lamb survival traits (expressed as a trait of the dam), is lower than that for BCS (and BCS changes) over the reproductive cycle. The genetic relationships amongst the BCS of ewes at pre-mating, pregnancy scan and at pre-lambing, with litter size at pregnancy scan and number of lambs weaned, were consistent. They indicate that ewes of higher body condition score (potentially over-fat, within the range recorded in these flocks) conceive, and rear, fewer lambs, with genetic correlations ranging between -0.18 and -0.58. However, post-weaning, animals with genetic propensity for greater gain in BCS from weaning to pre-mating produce larger litters and rear more lambs. In addition, the selection of ewes that lose less condition during pregnancy will reduce foetal losses. The results from this study paint a complex picture that should be interpreted in the context of specific management practices for extensively managed hill sheep, at critical times in their reproductive cycle. The traits relating to body tissue mobilisation, as assessed using BCS, are mostly heritable and their inclusion in future breeding programmes, to aid future selection for resilience, should be considered.

The Annual Reproductive Cycle, Proximate Composition, Fatty Acid and Amino Acid Content of Pacific Oyster, Crassostrea gigas (Magallana gigas), in Gadeok-do, Korea

The Annual Reproductive Cycle, Proximate Composition, Fatty Acid and Amino Acid Content of Pacific Oyster, Crassostrea gigas (Magallana gigas), in Gadeok-do, Korea

Effect of Life History on Alopias pelagicus Overexploitation Vulnerability: A Literature Review

Alopias pelagicus Nakamura 1935 or pelagic thresher shark is an epipelagic species of shark prone to overexploitation due to its epipelagic habitat and slow life history. In 2019, based on existing data on abundance and exploitation, A. Pelagicus was included in the International Union for Conservation of Nature (IUCN) Red List of Threatened Species with the category of endangered (EN). This literature review analyzed the relationship between A. pelagicus life history and overexploitation susceptibility. The method used is a comprehensive search of international journals in online databases from ScienceDirect and Google Scholar with certain inclusion and exclusion criteria. Based on the criteria, seven out of 270 search results of international journal articles were included for the analysis. The results from the seven journal articles shows that A. pelagicus has a slow life history or k-selected life history. This life history is characterized by slow sexual maturity, low fecundity, long gestation period, annual reproductive cycle, slow growth, long lifespan, and low natural mortality rate. This life history makes A. pelagicus prone to overexploitation because if the mortality rate of catching exceeds the natural mortality rate, it will take a long time for A. pelagicus to return to their original population size.

Molecular cloning and bioinformatic characterization of Gonadotropin Inhibitory Hormone (GnIH) and its receptors in the freshwater murrel, Channa punctatus (Bloch, 1793).

Gonadotropin inhibitory hormone belonging to the RFamide peptide family, a hypothalamic neuropeptide, regulates Hypothalamus-pituitary-gonadal (HPG) axis and inhibits gonadal development. GnIH polypeptide precursor has an Arg-Phe-NH2 (RFamide) motif at the C-terminal, which has LPXRF (X = Q or L) domain. The actions of GnIH are mediated through G-protein coupled receptors and upto threereceptors have been characterized in many teleosts. GnIH exerts its inhibitory effect on the HPG axis through direct interaction with GnRH and Kisspeptin neurons in the brain and acts directly on the pituitary gonadotrophs. To decipher the role of GnIH in Indian freshwater murrel, Channa punctatus, we sequenced the cDNA encoding GnIH and its two receptors. The identified GnIH mRNA encodes three RFamide peptides having -MPMRF, -MPQRF, and -LPQRFamide motifs. In silico analysis of the amino acid sequence of GnIH exhibits its molecular and functional properties and the protein-protein interaction with significant factors regulating the HPG axis. The 3-D structure of GnIH and its receptors, provides more relevant information about the active residues of these proteins which might be involved in their functioning and interaction with other proteins. Molecular dynamic simulation of GnIH protein has provided more insight into its dynamic behavior. The expression of GnIH and its receptors, shows an inverse correlation with gonadal development during the annual reproductive cycle.

Intersex manifestation in the rainbow darter (Etheostoma caeruleum): Are adult male fish susceptible to developing and recovering from intersex after exposure to endocrine active compounds?

For over a decade, intersex has been observed in rainbow darter (RD) (Etheostoma caeruleum) populations living downstream wastewater treatment plants (WWTPs) in the Grand River, Ontario, Canada. To further our understanding of intersex development in adult male fish, the current study addressed three objectives: i) can intersex be induced in adult male fish, ii) is there a specific window of exposure when adult male fish are more susceptible to developing intersex, and iii) can pre-exposed adult male fish recover from intersex? To assess intersex induction in adult male fish, wild male RD were exposed in the laboratory for 22 weeks (during periods of spawning, gonadal regression, and gonadal recrudescence) to environmentally relevant concentrations of 17α-ethinylestradiol (EE2) including nominal 0, 1, and 10 ng/L. Intersex rates and severity at 10 ng/L EE2 were similar to those observed historically in adult male populations living downstream WWTPs in the Grand River and confirmed previous predictions that 1–10 ng/L EE2 would cause these adverse effects. To assess a window of sensitivity in developing intersex, male RD were exposed to nominal 0, 1 or 10 ng/L EE2 for 4 weeks during three different periods of gonadal development, including (i) spawning, (ii) early recrudescence and (iii) late recrudescence. These short-term exposures revealed that intersex incidence and severity were greater when RD were exposed while gonads were fully developed (during spawning) compared to periods of recrudescence. To assess if RD recover from intersex, wild fish were collected downstream WWTPs in the Grand River and assessed for intersex both before and after a 22-week recovery period in clean water that included gonadal regression and recrudescence. Results showed that fish did not recover from intersex, with intersex rates and severity similar to those both before and after the transition to clean water. This study further advances our knowledge on intersex manifestation in adult male fish including their sensitivity to endocrine active compounds during different periods of their annual reproductive cycle and their limited ability to recover from intersex after onset of the condition.

Annual reproductive cycle of males of the great fruit-eating bat, Artibeus lituratus: Testicular variations, abiotic regulation and sperm analysis

Artibeus lituratus is one of the most well-known bat species in the Neotropics, probably due to its high abundance and the ability to inhabit urban areas. It plays an important ecological role in the ecosystem due to its ability to disperse seeds, which contributes to the regeneration of degraded areas. Actually, the species has been used as an important experimental model for ecotoxicological studies of the impact of pesticides on male reproduction. Despite that, the reproductive pattern of A. lituratus is still controversial due to inconsistent descriptions of the reproductive cycle. Thus, the aim of the present work was to evaluate the annual variations of the testicular parameters and sperm quality of A. lituratus and analyze their responses to annual variations in abiotic factors in the Cerrado area in Brazil. Testes of five specimens were collected each month for one year (12 sample groups) and submitted to histological, morphometric, and immunohistochemical analyses. Analyses of the sperm quality were also performed. Results demonstrate that A. lituratus presents a continuously active process of spermatogenesis throughout the year, with two significant peaks in spermatogenic production (September-October and March), which indicates a bimodal polyestric pattern of reproduction. These reproductive peaks seem to be related to an increase in proliferation and, consequently, in the number of spermatogonia. Conversely, seasonal variations in testicular parameters are correlated with annual fluctuations in rainfall and photoperiod but not with temperature. In general, the species presents smaller spermatogenic indexes with a similar sperm quantity and quality to other bat species.

Rhythmicity in testicular melatonin and its correlation with the dynamics of spermatogenic cells in an annual reproductive cycle of Clarias batrachus under natural photo-thermal conditions

Melatonin, the pineal hormone, is synthesized and secreted rhythmically in accordance with various environmental cues especially photo-thermal conditions. The reproductive physiology of seasonal breeders is synchronized with the surroundings by melatonin as a neuroendocrine mediator to acts as an important factor in fish reproduction. However, the data on the participation of melatonin in male reproduction and the putative interaction with the process of spermatogenesis in fish is scarce till date. So, major objectives of the current study are to determine for the first time, the relationship, if any, between seasonal levels of melatonin and testicular development and maturation of the germ cells, and also the involvements of specific meteorological parameters in spermatogenesis under natural photo-thermal conditions. We measured the concentration of circulatory and testicular melatonin; value of gonadosomatic index (GSI), relative percentages of different developing spermatogenic cells, area and perimeter (size and shape) of seminiferous lobules along with the level/duration of rainfall, water temperature and day length in six reproductive phases throughout an annual cycle in adult male catfish (Clarias batrachus). Intra-testicular and serum melatonin concentration showed a similar seasonal pattern with a peak during “functional maturity” phase and trough during “slow spermatogenesis” phase. Correlation as well as regression analyses also supported this positive relationship. Interestingly, intra-testicular melatonin also showed a significant positive correlation with GSI and relative percentage as well as lobular size of mature stages (spermatid and spermatozoa) of germ cells in an annual cycle. Furthermore, meteorological factors exhibited as critical cues to regulate the dynamics (in %) of spermatogenic cells and the level of testicular melatonin throughout the annual gonadal cycle. Our results corroborated by principal component (PC) analysis and showed very clearly that active “functional maturity” state is characterized by GSI, testicular melatonin, relative abundance and lobular size of mature spermatogenic stages as key internal oscillators; and studied environmental variables as the external clues for the regulation of spawning process. Collectively, the present data revealed that there is a relationship between melatonin levels and testicular growth and development of germ cells in Clarias batrachus under natural photo-thermal conditions.

Reproductive cycles of alligator snapping turtles (Macrochelys temminckii)

The alligator snapping turtle (Macrochelys temminckii) is a species for which captive propagation and reintroduction programs are well established; however, little is known about its reproductive behavior and physiology. In this study, we measured monthly plasma sex steroid hormone concentrations of androgen (T + DHT) estradiol-17B (E2), and progesterone (P4), and used ultrasonography to monitor annual reproductive cycles of a captive population of alligator snapping turtles that is maintained under semi-natural conditions in southeastern Oklahoma. Concurrently, we used automated radio telemetry to measure the relative activity levels of male and female alligator snapping turtles and examine these activity patterns in the context of their reproductive cycles. We also measured monthly concentrations of the glucocorticoid (GC) corticosterone (CORT). Seasonal variation was only detected for T in males, but was observed for T, E2, and P4 in females. Vitellogenesis began in August and ended in April and coincided with elevated E2. Ovulation took place 10–29 April and the nesting period lasted from 11 May – 3 June. Males exhibited greater relative activity levels than females in the fall, winter, and early spring, which coincided with the period when mature sperm would be available for mating. Females were more active than males during the peri-nesting period in the spring. Seasonal changes in CORT were detected and did not differ between males and females. CORT concentrations were elevated in the late spring and summer, coincident with the foraging season, and depressed in the fall, and winter, and at their nadir in the early spring.

New approaches concerning the testis of Astyanax lacustris (Characidae): immunohistochemical studies

Astyanax lacustris, locally known as lambari-do-rabo-amarelo, is a study model for Neotropical fish. Testis of A. lacustris shows deep morphophysiological changes throughout the annual reproductive cycle. This work analyzed the distribution of claudin-1, actin, and cytokeratin as elements of the cytoskeleton in germinal epithelium and interstitium; the distribution of type I collagen, fibronectin, and laminin as extracellular matrix compounds; and the localization of androgen receptor in the testis of this species. Claudin-1, cytokeratin, and actin were present in the Sertoli cells and modified Sertoli cells, and actin was also detected in peritubular myoid cells. Type I collagen were in the interstitial tissue, laminin in the basement membrane of germinal epithelium and endothelium, but fibronectin was additionally detected in the germinal epithelium compartment. The labeling of androgen receptor was higher in peritubular myoid cells and undifferentiated spermatogonia, and weaker labeling was detected in type B spermatogonia. Therefore, the present work highlights new aspects of the biology of the testis of A. lacustris, and contribute to amplify the understanding of this organ.

Reproductive phenology of critical native plant species for mineland restoration in the eastern Amazon

AbstractAmazon ironstone outcrops vegetation, or canga, is a remarkable environment in which the plants are adapted to peculiar circumstances. Knowledge regarding different aspects of this ecosystem remains modest, including necessary insights for its conservation and recovery, such as the reproductive phenology of priority species that form the plant community. This study aimed to monitor the reproductive phenology of critical native species that are categorized as rare, endemic, and/or threatened in the canga of the Amazon Rainforest, in Pará, Brazil. During February 2016 and May 2017, eleven species were evaluated regarding the presence or absence of flowering and fruiting phenophases, and these were associated with environmental variables. Phenological data were evaluated through circular statistical analysis. All studied species flowered and produced fruit during the monitoring period. The evaluated species have an annual reproductive cycle marked by seasonality and flowering peaks between March and April, during the wet season, and fruiting peaks during May, at the beginning of the dry season. The best period for collecting ripe seeds, a primary tool for the restoration of degraded areas, is June. Water availability may be essential for the establishment of annual plants and to induce flowering in both annual and perennial species. The reproductive phenophases of the studied species are concentrated within a short period and are synchronized, which may increase the possibility of cross‐pollination and minimize flower and seed predation. We discuss the challenges in including annual plants and the importance of having them and perennial species in conservation and restoration of degraded areas projects.

Temporal expression of thyroid hormone regulating genes (tsh-b, tsh-r, dio2 and dio3) and their correlation with annual reproductive cycle of the Indian freshwater catfish, Heteropneustes fossilis (Bloch).

Photoperiod and temperature are well-established environmental cues for gonadal growth in seasonally reproducing organisms. The photoperiod is known to regulate seasonal reproduction via induction of thyroid hormone regulating genes in the saccus vasculosus (SV) of fishes. However, SV is absent in many seasonally breeding fishes, including Heteropneustes fossilis. H. fossilis is a long-day breeding catfish in which gonadal recrudescence begins six months earlier than spawning. The present study attempted to analyse the expression of thyroid hormone-regulating genes (tsh-b, tsh-r, dio2 and dio3) in the brain, liver and ovary. In the brain, upregulated expression of thyrotropin-beta subunit (tsh-b), deiodinase2 (dio2) and deiodinase3 (dio3) genes is concomitant with the increasing photoperiod and temperature in nature, which may appear to regulate seasonal reproduction. Both deiodinases, dio2 and dio3, were also upregulated in the liver and ovarian tissue during the gonadal growth phase. The upregulation of deiodinases may enhance the metabolism and activity of tissues, thereby facilitating their respective roles. The expression of these genes was also assessed in the brain, liver, ovary, kidney, skin, spleen and gill tissues during the spawning period. The ubiquitous expression of deiodinases may point to enhanced activity in their organ-specific role. The present study speculates that expression of tsh-b, tsh-r, dio2 and dio3 genes during the reproductive phase of H. fossilis might be involved in the regulation of seasonal reproduction.

Sexual Maturity and Macronutrient Contents in Diopatra sp. (Onuphidae, Polychaeta) Maintained at Different Salinity Levels

Diopatra sp. (Onuphidae, Polychaeta) is an economically important polychaete species commonly used as a fishing bait by local anglers in Cilacap, Central Java Province. Some biological aspects of this local species, however, have not been studied yet. The aim of this research was to see the effect of salinity levels on the sexual maturity and the macronutrient contents of the animals. Diopatra specimens in the present study were collected from the intertidal mangrove habitats of Jeruklegi Village, Cilacap, in sexually immature condition. The worms were then transported to the laboratory and were maintained in containers with four different salinity levels, i.e. 10, 15, 20 and 25 ppt over the next two months. The sexual maturity of the animals were observed based on the presence or absence of coelomic gametes. Proximate analysis was performed to determine macronutrient contents of the animals. The effect of salinity levels on the animals' sexual maturity and macronutrient contents was analyzed using one-way ANOVA. The results showed that salinity levels did not significantly affect the sexual maturity level of Diopatra worms (p > 0.05). Similarly, they did not affect the protein and fat contents, but impacted the carbohydrate content of the animals (p < 0.05). The protein and the fat contents in Diopatra sp., i.e. 41–43% and 6–9%, respectively, met the amount required to be used as shrimp broodstock and fish feeds. While the species has the potential for use in local aquaculture, the annual reproductive cycle as well as the identity of the species, however, require further research.

Characteristics of δ-Aminolevulinic Acid Dehydratase of the Cold-Water Sponge Halisarca dujardinii

δ-Aminolevulinic acid dehydratase (ALAD) is a key enzyme of the cytoplasmic heme biosynthesis pathway. The primary structure of the ALAD gene, the multimeric structure of the ALAD/hemB protein, and ALAD expression during the annual reproductive cycle were studied in the cold-water marine sponge Halisarca dujardinii. The results implicated the GATA-1 transcription factor and DNA methylation in regulating ALAD expression. Re-aggregation of sponge cells was accompanied by a decrease in ALAD expression and a change in the cell content of an active ALAD/hemB form. Further study of heme biosynthesis and the role of ALAD/hemB in morphogenesis of basal animals may provide new opportunities for treating pathologies in higher animals.

Annual reproductive cycle of a successful Lessepsian immigrant in the Eastern Mediterranean Sea, Pomadasys stridens (Forsskål, 1775) (Family: Haemulidae)

ABSTRACT The striped piggy, Pomadasys stridens (Forsskål, 1775), is one of the successfully colonized Lessepsian immigrants entering the Mediterranean through the Suez Canal. This study was carried out to understand to what extent the reproduction strategy adopted by this species had played a role in its successful establishment. The study is based on samples collected during the monthly trawl surveys conducted between January 2017 to November 2020 in the Northeast Mediterranean. The annual gonadal development cycle was estimated by observing the Gonadosomatic Index changes. Seasonal patterns in energy intake and allocation were acquired from Hepatosomatic, Digestosomatic, and Relative Body Condition indices. The results indicated that the species has prolonged gonadal development periods, during which spawning occurs twice, in early summer and at the onset of the winter. A comparison of all indices involved indicated that the species feeds and develops gonads at the same time before summer spawning, feeds heavily and stores energy during the warmest period, and uses the stored energy in the winter spawning. As these features do not differ much from their congenerics inhabiting the geography they originated from, it is suggested that it was not the ecological plasticity of the species that is the basis of their success but the reproductive traits they have fitted well to the Mediterranean Ecosystem.

Gonad recrudescence and annual sex steroid patterns in female goldspot mullet, Liza parsia reared in brackishwater pond

Goldspot mullet, Liza parsia is a commercially important fish of South East Asia, where its farming depends on wild seed resources due to unavailability of hatchery technology. It, therefore, is important to understand the annual reproductive cycle of female L. parsia in captivity. In this study, adult male and female L. parsia (body weight ranges: 45–90 g; total length ranges: 100–125 mm, age >1 year) were collected from the wild and reared in a brackishwater pond. Thereafter, fish were randomly sampled at monthly intervals to measure the hepatosomatic index (HSI), gonadosomatic index (GSI), levels of serum steroids (testosterone, T; 17β-estradiol, E2 and 17α-hydroxyprogesterone, 17-OHP), and oocyte growth. Results exhibited that female L. parsia undergoes six different maturation stages, namely I (oocyte diameter, OD: <100 µm), II (OD: 100–350 µm), III (OD: 350–400 µm), IV (vitellogenic oocyte, OD: 400–450 µm), V (ripe oocyte, OD: 450–550 µm) and VI (atretic oocyte, OD: 60–150 µm), with synchronous oocyte development. The highest (P < 0.05) HSI (1.96 ± 0.24) and GSI (12.01 ± 0.73) were recorded in December and January, respectively. Concentration of E2 gradually increased from August and reached its peak (807.67 ± 25.98 pg mL−1, P < 0.05) in December. The level of 17-OHP (85.87 ± 0.91 pg mL−1) was at its peak during the normal spawning month (January) (P < 0.05). Overall, the results indicated that L. parsia attains maturity in brackishwater pond, which is consistent with previous observations, and altogether provide the basis to develop a breeding technology in captivity through hormonal and environmental manipulations.

Microclimatic variation affects developmental phenology, synchrony and voltinism in an insect population

Abstract Temperature influences the rate of most biological processes. Nonlinearities in the thermal reaction norms of such processes complicate intuitive predictions of how ectothermic organisms respond to naturally fluctuating temperatures, and by extension, to climate warming. Additionally, organisms developing close to the ground experience a highly variable microclimate landscape that often is poorly captured by coarse standard climate data. Using a butterfly population in central Sweden as a model, we quantified the consequences of small‐scale temperature variation on phenology, emergence synchrony and number of annual reproductive cycles (voltinism). By combining empirical microclimate and thermal performance data, we project development of individual green‐veined white butterflies (Pieris napi) across 110 sites in an exceptionally high‐resolved natural microclimate landscape. We demonstrate that differences among microclimates just meters apart can have large impacts on the rate of development and emergence synchrony of neighbouring butterflies. However, when considering the full development from egg to adult, these temporal differences were reduced in some scenarios, due to negative correlations in development times among life stages. The negative correlations were caused by temperatures at some sites beginning to exceed the optimum for development as the season progressed. Indeed, which sites were optimal for fast development could change across the lifetimes of individual butterflies, that is, ‘fast’ sites could become ‘slow’ sites. Thus, from a thermal point of view, there seem to be no consistently optimal microsites. Importantly, the fast sites were not always the warmest sites. We showed that such unintuitive effects could play an important role in the regulation of phenological synchrony and voltinism in insects, as most sites consistently favoured two generations. The results were generally robust across years and three different egg‐laying dates. Using high‐resolved empirical climate data on organism‐relevant temporal and spatial scales and considering nonlinear responses to temperature, we demonstrated the large and unintuitive population‐level consequences of locally and temporarily high temperatures. We suggest to—whenever possible—incorporate species‐ and life stage‐specific nonlinear responses to temperature when studying the effects of natural microclimate variation and climate change on organisms. Read the free Plain Language Summary for this article on the Journal blog.