Chronic and acute thermal stressors have non-additive effects on fertility.

Climate change is driving both higher mean temperatures and a greater likelihood of heatwaves, which are becoming longer and more intense. Previous work has looked at these two types of thermal stressors in isolation, focusing on the effects of either a small, long-term increase in temperature or a large, short-term increase in temperature. Yet, a fundamental gap in our understanding is the combined effect of chronic and acute thermal stressors and, in particular, its impact on vital processes such as reproduction. Here, we investigated the independent and interactive effects of higher constant temperatures and short-term heatwave events on reproductive success and offspring fitness in an insect study system, the burying beetle Nicrophorus vespilloides. We found a substantial reduction in key fitness traits (fecundity, hatching success and offspring size) after exposure to both a heatwave and higher constant temperatures, but not after exposure to only one of these thermal stressors. This indicates that the effects of chronic and acute thermal stressors are amplified when they act in combination, as is very likely to occur in natural populations. Our findings, therefore, suggest that, by not considering the potential multiplicative effects of different types of thermal stressors, we may be underestimating the effects of climate change on animal fertility.

High thermal tolerance of egg clutches and potential adaptive capacity in green turtles.

Climate warming threatens sea turtles, among other effects, because high temperatures increase embryo mortality. However, not all species and populations are expected to respond the same way because they could have different thermal tolerances and capacities to adapt. We tested the effect of incubation temperature on egg mortality in a population of green turtles (Chelonia mydas) previously suggested to be less affected by extreme climatic events than others. We (1) assessed the relationship between temperature and hatching success, (2) defined an optimal range of temperatures that maximized hatching success and (3) assessed the variability in the response to temperature among clutches laid by different mothers, which could allow adaptation. Hatching success was consistently high in green turtle clutches with a skew toward high values, with 50 % of clutches having a success above 94 %. Yet, it was mildly affected by temperature, declining at both low and high temperatures. The optimal range of mean incubation temperatures was between ~30.5 °C and 32.5 °C. Current mean temperatures (31.3 °C) fall within the middle of the optimal range, indicating a potential resilience to further rises in mean nest temperature. Hatching success was best described by nest temperature and the interaction between female identity and temperature. This last predictor indicated a variability in thermal tolerance among clutches laid by different mothers and therefore, a capacity to adapt. The studied population of green turtles seems to be less vulnerable than others to climate warming. Understanding how different populations could respond to increasing temperatures could help complete the picture on the potential effects of climate change on sea turtles.

Effective toxicity of pH to embryonic development of the banded lampeye killifish Aplocheilichthys spilauchen (Duméril, 1861).

The banded lampeye killifish, Aplocheilichthys spilauchen, feeds on larvae of the anopheles mosquito, which makes the fish a good candidate for biological control of malaria. Aquatic organisms require optimal hydrogen ion concentration (pH) for healthy aquatic life, but the impact of pH alteration on A. spilauchen reproductive potential is not known. This study investigated the toxic effect of pH on the embryonic development of A. spilauchen using a static renewal exposure method. Newly fertilised embryos were exposed to a range of pH treatments (5-6 acidic; 7 neutral; 8-9 alkaline) until hatching. All pH media involved triplicates and pH 7 was used as a control. The pH media were checked every 24 h for change and adjusted if necessary. Dissolved oxygen (DO), electrical conductivity (EC), and temperature were monitored throughout the experiment. The endpoints investigated were hatching success, hatchling length, and hatching period. Results indicated a mean hatching success of 95.83 % for pH 7 (neutral) group, while embryos exposed to acidic and basic media recorded lower hatching successes of 60.42 % and 83.34 %, respectively. Hatchling length and hatching period were longer in the control group than in groups of acidic and basic media. Effective toxic pH values of 4.5, 6 and 6.5 were estimated for the hatching period, hatching success, and hatchling length, respectively. These results suggest that sharp changes in the pH of aquatic environments from neutral may adversely impact the reproductive potential of A. spilauchen via embryonic development. This is the first time effective toxic pH values have been estimated for A. spilauchen embryonic development.

Nest site selection and fidelity of European pond turtle (Emys orbicularis) population of Babat Valley (Gödöllo, Hungary).

BACKGROUND: The conservation of aquatic and semiaquatic turtles requires knowledge of the area and vegetation structure of habitat used for nesting, and nesting migration route. We aimed to survey the effects of habitat features to the nest site selection, nesting success, and test the possibility of nest site fidelity. Our study was carried out at 10 different nesting areas, with special emphasis on data from returning females in a pond system in Hungary between 2014 and 2017. RESULTS: Most nesting attempts were found in closed sand steppes, uncharacteristic dry and semi-dry grasslands habitat patches. The principal component analysis (PCA) showed that increased sandy soil cover, sunlight and slope were important variables in nest site choice. The increasing PCA first axis score significantly increased the chance of an emergence. The degradation of open steppe vegetation, occurrence of weeds, invasive and disturbance tolerant species have a negative effect on the selection of nest sites. We observed that 96.55% of nests were located within 20 m south of a pine forest at preferred nest site at pond 5, which provided the right incubation temperature through partial shading. The returning females nested significantly closer to the northern pine forest than the single clutch females. Most probably the returning females already has the necessary experience to select the right nesting site. The individually marked females did not choose new nesting areas during the monitored years which suggests nesting area fidelity, but we did not find nest site fidelity. CONCLUSION: The maintenance of mosaic habitat structure, slowing down the succession process at the nesting area should be basic priorities in European pond turtle conservation programs. We suggested a spatial and temporal scheduling of land management and agricultural work to the local farmers. If the actual nest site is in an agricultural area, all work should be avoided throughout the year. Agricultural machinery should avoid the migration routes of adult turtles and emerged hatchlings during the concerned period. Under strong predation pressure, predator control should be carried out, and use nest protection.

Shark critical life stage vulnerability to monthly temperature variations under climate change.

In a 10-month experimental study, we assessed the combined impact of warming and acidification on critical life stages of small-spotted catshark (Scyliorhinus canicula). Using recently developed frameworks, we disentangled individual and group responses to two climate scenarios projected for 2100 (SSP2-4.5: Middle of the road and SSP5-8.5: Fossil-fueled Development). Seasonal temperature fluctuations revealed the acute vulnerability of embryos to summer temperatures, with hatching success ranging from 82% for the control and SSP2-4.5 treatments to only 11% for the SSP5-8.5 treatment. The death of embryos was preceded by distinct individual growth trajectories between the treatments, and also revealed inter-individual variations within treatments. Embryos with the lowest hatching success had lower yolk consumption rates, and growth rates associated with a lower energy assimilation, and almost all of them failed to transition to internal gills. Within 6 months after hatching, no additional mortality was observed due to cooler temperatures.

Exposure of an endangered seabird species to persistent organic pollutants: Assessing levels in blood and link with reproductive parameters.

Ocean contamination, particularly from persistent organic pollutants (POPs), remains a significant threat to marine predators that occupy high trophic positions. Long-lived procellariform seabirds are apex predators in marine ecosystems and tend to accumulate contaminants. Prolonged exposure to pollutants negatively affects their fitness including reproductive success. Low breeding success may represent a hurdle for the restoration of small and endangered seabird populations, including several highly threatened gadfly petrels. Here we investigated the annual variation (2019 and 2022) in organochlorine pesticide (OCP), polychlorinated biphenyl ether (PCB), polybrominated diphenyl ether (PBDE), and polycyclic aromatic hydrocarbon (PAH) exposure in the endangered Bermuda petrel (Pterodroma cahow), and the relationship between female contaminant burden and breeding parameters. We found that petrels were exposed to a wide range of pollutants (33 out of 55 showed measurable levels) with PCBs dominating the blood contaminant profiles in both years. Only 9 compounds were detected in >50 % of the birds. Specifically, among OCPs, p, p'-DDE and hexaclorobenzene were the most frequently detected while fluorene and acenaphthene were the most common PAH. The concentrations of ∑5PCBs and ∑7POPs were higher in older birds. Furthermore, females with greater contaminant burdens laid eggs with a lower probability of hatching. However, female investment in egg production (size and volume) was unrelated to their blood contaminant load. Overall, this study highlights the presence of a wide range of contaminants in the petrel's food web, and it sheds light on the potential impact of chronic exposure to sub-lethal levels of PCBs on the breeding success of seabirds. We claim that toxicological testing should be a practice integrated in the management of seabirds, particularly of endangered species to monitor how past and present anthropogenic activities impact their conservation status.

The limits of stress-tolerance for zooplankton resting stages in freshwater ponds.

In seasonal environments, many organisms evolve strategies such as diapause to survive stressful periods. Understanding the link between habitat stability and diapause strategy can help predict a population's survival in a changing world. Indeed, resting stages may be an important way freshwater organisms can survive periods of drought or freezing, and as the frequency and extent of drought or freezing vary strongly among habitats and are predicted to change with climate change, it raises questions about how organisms cope with, and survive, environmental stress. Using Daphnia magna as a model system, we tested the ability of resting stages from different populations to cope with stress during diapause. The combination of elevated temperatures and wet conditions during diapause shows to prevent hatching altogether. In contrast, hatching is relatively higher after a dry and warm diapause, but declines with rising temperatures, while time to hatch increases. Resting stages produced by populations from summer-dry habitats perform slightly, but consistently, better at higher temperatures and dryness, supporting the local adaptation hypothesis. A higher trehalose content in resting eggs from summer-dry habitat might explain such pattern. Considering that temperatures and summer droughts are projected to increase in upcoming years, it is fundamental to know how resting stages resist stressful conditions so as to predict and protect the ecological functioning of freshwater ecosystems.

Evaluation of Fecundity, Fertilization, Hatching, and Gonadosomatic Index of Exotic Clarias gariepinus (Burchell, 1822) and Native Clarias macromystax (Gunther, 1864) under Semi-Arid Conditions of Nigeria.

The study evaluates the hybridizations between two African catfish, C. gariepinus and C. macromystax, using artificial reproduction. Fecundity and gonadosomatic index were assessed, and growth performance at different developmental stages was evaluated. The results indicated that both species possess a similar gonadosomatic index. The parent C. gariepinus possesses significantly (p < 0.05) higher male reproductive quality than C. macromystax. Fecundity was significantly higher (p < 0.05) in the female parent of C. macromystax and lower in C. gariepinus. The highest fertilization rates and hatching rates were achieved in the hybrid cross of ♀C. macromystax × â™‚C. gariepinus (♀Cm × â™‚Cg) which also recorded the lowest deformed larva rate. Survival rates at the larval stage were more than 80%, with the highest record of survival in the hybrid ♀Cm × â™‚Cg. However, survival rates in the fry stage were lower than 70%. The hybrid cross (C. macromystax × C. gariepinus) outperformed the parental cross of C. macromystax but was not significantly similar to the parental cross of C. gariepinus. The study revealed the potential of the hybrid ♀C. macromystax × â™‚C. gariepinus, and hybridizations of ♀C. macromystax × â™‚C. gariepinus (♀Cm × â™‚Cg) are indeed possible and proved to have a better growth and survival rate under semi-arid conditions, which would contribute significantly to the improvement of C. macromystax production in captivity.

The effects of moderate concentrations of Karenia brevis on stone crab reproduction.

The stone crab, Menippe mercenaria, supports a commercial fishery along Florida's Gulf coast where harmful algae blooms, known as red tides (Karenia brevis) develop. Red tides occur nearly annually and can overlap with the stone crab reproductive season. We determined the impact of moderate red tide (K. brevis) concentrations (∼105 cells L-1) on stone crab embryo development, hatching success, female stress, hatch duration, and larval survival. Crabs and larvae were exposed to a control (no K. brevis) or moderate concentrations of K. brevis. No difference in embryo development or hatching success was observed. Stress was elevated in the K. brevis treatment, resulting in prolonged hatching relative to the control. Larval survival was reduced in K. brevis relative to the control. Moderate concentrations of K. brevis results in sublethal effects on stone crabs and reduces larval survival, suggesting that mitigation that reduces bloom concentrations could provide relief to stone crab populations.

Reproductive performance of Peregrine falcons relative to the use of organochlorine pesticides, 1946-2021.

Populations of some fish- and meat-eating birds suffered dramatic declines globally following the introduction of organochlorine pesticides during the late 1940s and 1950s. It has been hypothesised that these population declines during the 1950s-1970s were largely driven by a combination of reproductive failure due to eggshell-thinning, egg breakage and embryonic death attributable to DDT and its metabolites, and to enhanced mortality attributable to the more toxic cyclodiene compounds such as aldrin and dieldrin. Using 75 years (1946-2021) of Peregrine falcon (Falco peregrinus) monitoring data (315 unique nest-sites monitored for 6110 nest-years), we studied the breeding performance of a resident Peregrine population in southern Scotland relative to the spatiotemporal pattern of organochlorine pesticide use. We show that (i) Peregrine breeding success and measures of breeding performance increased substantially following the reduction in, and subsequently a complete ban on, the use of organochlorine pesticides; (ii) improvements in Peregrine breeding performance were more dramatic in southeastern Scotland where agriculture was the predominant land use than in southwestern Scotland where there was less arable and more forested land; (iii) Peregrines nesting closer to the coast generally had higher fledging success (that is, a higher proportion of clutches that produced at least one fledgeling) than those nesting inland farther away from the coast; (iv) low temperatures and excessive rain in May negatively affected Peregrine fledging success; and (v) Peregrine abundance increased in parallel with improvements in reproductive performance following the reduction and then complete ban on the use of organochlorine pesticides in the UK. However, recovery was gradual and occurred over four decades, and rate of recovery varied among measures of reproductive performance (egg, nestling and fledgeling production). Our results suggest that the temporal pattern of organochlorine pesticide use strongly influenced Peregrine reproductive parameters but that the pattern of influence differed regionally. Overall results are consistent with the hypothesis that reproductive failure caused by organochlorine pesticides was an important driver of the decline in the south Scottish Peregrine population, and that improvements in all measures of breeding performance following a reduction and eventual ban on organochlorine use facilitated the observed increase in this population.

Comparison of toxicity of silver nanomaterials and silver nitrate on developing zebrafish embryos: Bioavailability, osmoregulatory and oxidative stress.

The mechanisms of toxicity of engineered nanomaterials (ENMs) to the early life stages of freshwater fish, and the relative hazard compared to dissolved metals, is only partially understood. In the present study, zebrafish (Danio rerio) embryos were exposed to lethal concentrations of silver nitrate (AgNO3) or silver (Ag) ENMs (primary size 42.5 ± 10.2 nm). The 96 h-LC50 for AgNO3 was 32.8 ± 0.72 µg Ag L-1 (mean ± 95% CI) compared to 6.5 ± 0.4 mg L-1 of the whole material for Ag ENMs; with the ENMs being orders of magnitude less toxic than the metal salt. The EC50 for hatching success was 30.5 ± 1.4 µg Ag L-1 and 6.04 ± 0.4 mg L-1 for AgNO3 and Ag ENMs, respectively. Further sub-lethal exposures were performed with the estimated LC10 concentrations for both AgNO3 or Ag ENMs over 96 h, where about 3.7% of the total Ag as AgNO3 was internalised, as measured by Ag accumulation in the dechorionated embryos. However, for the ENM exposures, nearly all (99.8%) of the total Ag was associated with chorion; indicating the chorion as an effective barrier to protect the embryo in the short term. Calcium (Ca2+) and sodium (Na+) depletion was induced in embryos by both forms of Ag, but hyponatremia was more pronounced in the nano form. Total glutathione (tGSH) levels declined in embryos exposed to both Ag forms, but a superior depletion occurred with the nano form. Nevertheless, oxidative stress was mild as superoxide dismutase (SOD) activity stayed uniform and the sodium pump (Na+/K+-ATPase) activity had no appreciable inhibition compared to the control. In conclusion, AgNO3 was more toxic to the early life stage zebrafish than the Ag ENMs, still differences were found in the exposure and toxic mechanisms of both Ag forms.

Potential impacts of environmental bacteria on the microbiota of loggerhead (Caretta caretta) and green (Chelonia mydas) sea turtle eggs and their hatching success.

Sea turtle hatching success can be affected by many variables, including pathogenic microbes, but it is unclear which microbes are most impactful and how they are transmitted into the eggs. This study characterized and compared the bacterial communities from the (i) cloaca of nesting sea turtles (ii) sand within and surrounding the nests; and (iii) hatched and unhatched eggshells from loggerhead (Caretta caretta) and green (Chelonia mydas) turtles. High throughput sequencing of bacterial 16S ribosomal RNA gene V4 region amplicons was performed on samples collected from 27 total nests in Fort Lauderdale and Hillsboro beaches in southeast Florida, United States. Significant differences were identified between hatched and unhatched egg microbiota with the differences caused predominately by Pseudomonas spp., found in higher abundances in unhatched eggs (19.29% relative abundance) than hatched eggs (1.10% relative abundance). Microbiota similarities indicate that the nest sand environment, particularly nest distance from dunes, played a larger role than the nesting mother's cloaca in influencing hatched and unhatched egg microbiota. Pathogenic bacteria potentially derive from mixed-mode transmission or additional sources not included in this study as suggested by the high proportion (24%-48%) of unhatched egg microbiota derived from unknown sources. Nonetheless, the results suggest Pseudomonas as a candidate pathogen or opportunistic colonizer associated with sea turtle egg-hatching failure.

No evidence of inbreeding depression despite a historical severe bottleneck in the endangered Bermuda petrel (Pterodroma cahow).

The Bermuda petrel Pterodroma cahow is an island endemic seabird that belongs to the Procellariiformes, one of the most endangered orders of birds. Historical records suggest a significant population size decline following human settlement in Bermuda, bringing the species to near extinction. Since the 1950s, the population has been recovering aided by the implementation of an ongoing conservation plan. However, it still faces several threats, and negative genetic effects resulting from that drastic decline are to be expected, including inbreeding and genetic drift. We studied genetic diversity and levels of inbreeding, and their effects on individual fitness and mating choice. We also tested for a genetic signature of the recent demographic bottleneck. For this, we analyzed variation in thousands of nuclear single-nucleotide polymorphisms derived from double digest restriction site-associated DNA sequencing and 1 mitochondrial gene (cytochrome oxidase I). The results revealed that the Bermuda petrel suffered a recent genetic bottleneck and shows low mitochondrial diversity compared with other petrel species. Conversely, nuclear diversity was similar to that of other endangered petrels. Inbreeding levels were not high overall, although some individuals were highly inbred. However, we found no evidence that individual inbreeding or relatedness between mates affected hatching success, or that mate choice is influenced by kinship in this very small population.

Divergent effects of climate change on the egg-laying opportunity of species in cold and warm regions.

Climate warming can substantially impact embryonic development and juvenile growth in oviparous species. Estimating the overall impacts of climate warming on oviparous reproduction is difficult because egg-laying events happen throughout the reproductive season. Successful egg laying requires the completion of embryonic development as well as hatching timing conducive to offspring survival and energy accumulation. We propose a new metric-egg-laying opportunity (EO)-to estimate the annual hours during which a clutch of freshly laid eggs yields surviving offspring that store sufficient energy for overwintering. We estimated the EO within the distribution of a model species, Sceloporus undulatus, under recent climate condition and a climate-warming scenario by combining microclimate data, developmental functions, and biophysical models. We predicted that EO will decline as the climate warms at 74.8% of 11,407 sites. Decreasing hatching success and offspring energy accounted for more lost EO hours (72.6% and 72.9%) than the occurrence of offspring heat stress (59.9%). Nesting deeper (at a depth of 12 cm) may be a more effective behavioral adjustment for retaining EO than using shadier (50% shade) nests because the former fully mitigated the decline of EO under the considered warming scenario at more sites (66.1%) than the latter (28.3%). We advocate for the use of EO in predicting the impacts of climate warming on oviparous animals because it encapsulates the integrative impacts of climate warming on all stages of reproductive life history.

Efectos divergentes del cambio climático sobre la oportunidad de desove de las especies en regiones cálidas y frías Resumen El calentamiento global puede tener un impacto considerable sobre el desarrollo embrionario y el crecimiento juvenil de las especies ovíparas. Es complicado estimar el impacto general que tiene el calentamiento global sobre la reproducción ovípara ya que los eventos de desove suceden durante la época reproductiva. El desove exitoso requiere que se complete el desarrollo embrionario y que el momento de eclosión sea favorable para la supervivencia de las crías y la acumulación de energía. Proponemos una nueva medida-oportunidad de desove (OD)-para estimar las horas anuales durante las cuales una puesta de huevos recién desovados produce crías que sobreviven y almacenan suficiente energía para invernar. Estimamos la OD dentro de un modelo de distribución de la especie Sceloporus undulatus bajo las recientes condiciones climáticas y bajo un escenario de calentamiento global mediante la combinación de datos microclimáticos, funciones del desarrollo y modelos biofísicos. Pronosticamos que la OD declinará conforme la temperatura aumente en 74.8% de los 11407 sitios. La disminución del éxito de eclosión y de la energía de las crías explicó más horas perdidas de OD (72.6% y 72.9%) que la presencia de estrés por calor en las crías (59.9%). Una anidación más profunda (a una profundidad de 12 cm) puede ser un ajuste conductual más efectivo para la retención de la OD que los nidos con mayor sombreado (50% de sombra) porque el primero mitigó por completo la declinación de la OD bajo el escenario de calentamiento en más sitios (66.1%) que el segundo ajuste (28.3%). Defendemos el uso de la OD en el pronóstico del impacto del calentamiento global sobre los animales ovíparos porque encapsula los impactos integrales que tiene el calentamiento global sobre todas las etapas de la vida reproductiva. 气候变化在寒冷和温暖地区对物种产卵机会造成不同影响.

Systematic review of avian hatching failure and implications for conservation.

Avian hatching failure is a widespread phenomenon, affecting around 10% of all eggs that are laid and not lost to predation, damage, or desertion. Our understanding of hatching failure is limited in terms of both its underpinning mechanisms and its occurrence across different populations. It is widely acknowledged that rates of hatching failure are higher in threatened species and in populations maintained in captivity compared to wild, non-threatened species, but these differences have rarely been quantified and any broader patterns remain unexplored. To examine the associations between threat status, management interventions, and hatching failure across populations we conducted a phylogenetically controlled multilevel meta-analysis across 231 studies and 241 species of birds. Our data set included both threatened (Critically Endangered, Endangered, and Vulnerable) and non-threatened (Near Threatened and Least Concern) species across wild and captive populations, as well as 'wild managed' ('free-living') populations. We found the mean overall rate of hatching failure across all populations to be 16.79%, with the hatching failure rate of wild, non-threatened species being 12.40%. We found that populations of threatened species experienced significantly higher mean hatching failure than populations of non-threatened species. Different levels of management were also associated with different rates of hatching failure, with wild populations experiencing the lowest rate of hatching failure, followed by wild managed populations, and populations in captivity experiencing the highest rate. Similarly, populations that were subject to the specific management interventions of artificial incubation, supplementary feeding, and artificial nest provision displayed significantly higher rates of hatching failure than populations without these interventions. The driver of this correlation between hatching failure and management remains unclear, but could be an indirect result of threatened species being more likely to have lower hatching success and also being more likely to be subject to management, indicating that conservation efforts are fittingly being focused towards the species potentially most at risk from extinction. This is the most comprehensive comparative analysis of avian hatching failure that has been conducted to date, and the first to quantify explicitly how threat status and management are associated with the rate of hatching failure in a population. We discuss the implications of our results, focusing on their potential applications to conservation. Although we identified several factors clearly associated with variation in hatching failure, a significant amount of heterogeneity was not explained by our meta-analytical model, indicating that other factors influencing hatching failure were not included here. We discuss what these factors might be and suggest avenues for further research. Finally, we discuss the inconsistency in how hatching failure is defined and reported within the literature, and propose a standardised definition to be used in future studies which will enable better comparison across populations and ensure that the most accurate information is used to support management decisions.

Evaluate effects of the dilution medium and holding time on various motility parameters of delta smelt semen.

Sperm preservation is an efficient technique used for the recovery, conservation, and management of some endangered fish species. The present study was conducted to explore how preservation time would affect sperm and spawning performance in the endangered delta smelt (Hypomesus transpacificus). Sperm were preserved with the modified Hanks balanced salt solution at 14.7-16.9 °C. The Kruskal-Wallis test of sperm parameters using OpenCASA plugin in ImageJ software showed that sperm (n = 33♂) had significantly higher velocity and motility within the first 5 s after activation than that of other time points, while sperm had the lowest velocity and motility after 3 min post activation (P < 0.001). The findings (n = 30♂) also showed fresh sperm had higher velocity and motility than preserved sperm, while the sperm preserved for over 24 h showed a significantly low performance (P < 0.001). The nonlinear mixed effects models of fertilization results (n = 14♂ × 70♀) indicated the fresh sperm and sperm preserved for 1 h had higher fertilization rates than other preservation times (P < 0.001). The hatching rate (n = 14♂ × 70♀) also showed the fresh sperm and sperm preserved for 3 min and 1 h had higher hatching rates than other preservation times (P < 0.001). Overall, the study showed the best sperm performance in delta smelt was found within the first 5 s post activation, and the best fertilization and hatching rates were found when the sperm were fresh and preserved for 1 h. The findings of this study provide information for the first time about how long the delta smelt's sperm are motile for quality analysis, and how the preservation time can affect sperm quality, fertility, and hatching of this species for future applications.

Thiamethoxam affects the developmental stages of banded gourami (Trichogaster fasciata).

Thiamethoxam (THM), a type III systemic neonicotinoid insecticide, is widely used in agriculture in many countries, including Bangladesh. THM can enter the aquatic systems through the runoff, spray-drift and groundwater leaching and can affect the aquatic organisms, including fish. Current environmental levels of THM in Bangladesh waters are variable. However, the presence of this chemical in the aquatic environment and its possible effects on the fish inhabiting those water bodies is concerning. To understand the effects of environmental THM on the development of embryo and larvae, the present study used banded gourami (Trichogaster fasciata), a freshwater fish species distributed in different Asian countries, including Bangladesh. In laboratory setting, fertilized eggs (n = 100) and one-day-old banded gourami larvae (n = 100) were exposed to six concentrations of THM (0, 0.02, 0.2, 2, 20, 200 mg/L) in three replicates, in which three concentrations were within the environmentally relevant levels. Hatching rate, incubation period, mortality, and malformations of embryo and larvae were observed. The hatching success and survival of embryo and larvae significantly decreased with increasing THM concentrations. The 24-h LC50 of THM for the embryo was 4.24 mg/L. The 24-h, 48-h, 72-h, and 96-h LC50 values of THM for one-day-old larvae were 12.20, 3.80, 0.78, and 0.27 mg/L, respectively. Overall developmental malformations included lordosis, notochord abnormality, yolk-sac edema, dark brown yolk sac, hemorrhage, and irregular caudal fin. These abnormalities in embryos were common across all the concentrations of THM applied. The results of the present study suggest that environmentally relevant concentrations of THM can induce developmental defects in the embryo and larvae of banded gourami.

The Survival Rate from Splitting Clutch Design Method for Green Turtle's Relocated Nest in Penang Island, Malaysia.

Ten nests were collected from Kerachut and Teluk Kampi, Penang Island between 2 August 2009 and 9 December 2009, and each one nest was split into three small clutch sizes for incubation at three nesting depths (45 cm, 55 cm and 65 cm), with a total of 30 modified nests for this experiment. Three important objectives were formulated; to observe on the survival hatchings among the three nesting depths, to study on the effects of sand temperature on incubation period among the three nesting depths, and to investigate the influence of sand temperature on hatchling's morphology. Main result shows that the mean survival of the hatchlings was 25.40% at 45 cm nesting depth, followed by mean 17.60% at 55 cm nesting depth, and lastly, the mean was 21.50% at 65 cm nesting depth. Overall, there are 56.63% survival hatchlings, 10.97% dead hatchlings and 32.40% unhatched eggs were produced. The incubation period was also found to be significantly correlated with sand temperature, p > 0.001, and nesting depth, p < 0.001. The hatchling's length and weight varies is sizes across the nesting depths, p < 0.001. However, the small difference in hatchling sizes per nesting depths are not strong enough to prove the significant correlation with sand temperature, p > 0.05. This article provides a basic knowledge from the splitting clutch design method. A sum of 50%-60% survivals hatchlings produced were incubating under small range of clutch sizes, 29 to 49 eggs. This article provides basic result on the survival hatchlings, eggs survivorship, incubation period, temperature, hatchling's morphology and discussion on implication of this method on conservation in Malaysia.

Terdapat 10 sarang penyu yang dikutip di pantai Kerachut dan Teluk Kampi, di antara 2 Ogos 2009 hingga 9 Disember 2009, dan setiap satu sarang dibahagikan kepada tiga bahagian kecil yang sama rata untuk proses pengeraman pada tiga kedalaman sarang yang berbeza (45 cm, 55 cm dan 65 cm). Jumlah keseluruhan sarang yang diubahsuai untuk menjalankan eksperimen ini ialah sebanyak 30 sarang. Tiga objektif utama telah diketengahkan; dimana penelitian ke atas anak penyu menetas di tiga kedalaman sarang yang berbeza, untuk mengkaji kesan suhu sarang ke atas masa pengeraman di antara tiga kedalaman sarang yang berbeza, dan kajian pengaruh suhu sarang ke atas morfologi anak penyu yang menetas. Keputusan utama menunjukkan min anak penyu menetas adalah sebanyak 25.40% di kedalaman sarang 45 cm, diikuti min 17.60% di kedalaman sarang 55 cm, dan yang terakhir, min 21.50% di kedalaman sarang 65 cm. Secara keseluruhannya, terdapat 56.63% anak penyu menetas, 10.97% anak penyu mati dan 32.40% telur yang tidak menetas telah dihasilkan. Didapati bahawa tempoh penetasan mempunyai signifikasi korelasi ke atas suhu sarang, p > 0.001 dan kedalaman sarang, p > 0.001. Sementara itu, panjang anak penyu dan berat anak penyu didapati berbeza saiz mengikut kedalaman sarang, p < 0.001. Namun begitu, perbezaan saiz anak penyu yang tidak begitu ketara yang dihasilkan mengikut kedalaman sarang tidak memberi kesan ke atas signifikasi korelasi dengan suhu sarang, p > 0.05. Kajian ini memberikan maklumat asas keputusan daripada kaedah pengasingan telur. Jumlah keseluruhan menunjukkan 50%­60% anak penyu menetas berjaya dihasilkan, walaupun dieramkan dalam jumlah kumpulan telur yang kecil, iaitu sebanyak 29­49 telur. Artikel ini adalah penting untuk memberikan maklumat asas mengenai anak penyu menetas, survival telur, tempoh penetasan, suhu, morfologi anak penyu dan perbincangan implikasi kaedah ini kepada konservasi di Malaysia.

Developmental asynchrony might not reduce fitness in early life in painted turtles.

Synchronous hatching and emergence of turtles from nests may be adaptive in predator avoidance during dispersal. However, little is known about the phenotypic consequences of such synchrony or the generality of predator avoidance in driving the evolution of this trait. Colbert et al. (2010) found that less advanced embryos hatched early in the presence of more advanced sibs, sustaining a persistent reduction in neuromuscular function. In this study, we experimentally assessed the influence of such accelerated embryonic development on hatching success, winter survival, and survival during terrestrial dispersal from the nest. Although we predicted that shortened incubation periods would reduce survival, early-hatching individuals suffered no detectable fitness costs at any stage considered in this study. Incubation temperature did not affect hatching success, and offspring sex did not affect survival across treatment groups. Incubation regime influenced offspring body size and was negatively correlated with dispersal time, however, there was no effect on survival during winter or terrestrial dispersal. Lack of a detectable fitness cost in these key early-life stages associated with hatching synchrony is consistent with a single, predator avoidance origin for this trait and retention in C. picta and other derived turtles via phylogenetic inertia.

Spatiotemporal Variation in Hatching Success and Nestling Sex Ratios Track Rapid Movement of a Songbird Hybrid Zone.

AbstractHybridization often occurs at the parapatric range interface between closely related species, but fitness outcomes vary: hybrid offspring exhibit diverse rates of viability and reproduction compared with their parental species. The mobile hybrid zone between two chickadee congeners (Poecile atricapillus × Poecile carolinensis) has been well studied behaviorally and genetically, but the viability of hybrids and the underlying mechanisms contributing to hybrid fitness have remained unclear. To better characterize the fitness costs of hybridization in this system, we analyzed 21 years of data from four sites, including more than 1,400 breeding attempts by the two species, to show that rates of hatching success changed substantially as the zone of hybridization moved across the landscape. Admixture-associated declines in hatching success correlated with reduced proportions of heterogametic (female) offspring, as predicted by Haldane's rule. Our data support an underlying mechanism implicating genetic admixture of the homogametic (male) parent as the primary determinant of offspring sex ratio, via incompatibilities on the hemizygous Z chromosome. Our long-term study is the first to directly measure changes in fitness costs as a vertebrate hybrid zone moves, and it shows that changes in these costs are a way to track the distribution of a hybrid zone across the landscape.