Hatchling Phenotype Research Articles

Effects of Emergence on Hatchling Phenotypes in Loggerhead Sea Turtles (Caretta caretta) of the North Pacific

Effects of Emergence on Hatchling Phenotypes in Loggerhead Sea Turtles (Caretta caretta) of the North Pacific

Effect of moisture, temperature, and maternal influence on the hatching, phenotype, and performance of hawksbill turtles Eretmochelys imbricata

Hawksbill turtles are considered Critically Endangered. An understanding of how nest microenvironment (moisture and temperature) and maternal characteristics can influence embryonic development, hatching success, phenotype, and hatchling performance is needed to ensure effective conservation management. We undertook controlled egg incubations at different temperatures and relative humidities. Additionally, we sampled temperatures at natural nests with data loggers, and relative humidity of the sand at nest depth, to determine the conditions that eggs experienced naturally. We varied relative sand humidity (RSH) percentages (30, 50, 75, and 100%) at a constant incubation temperature of 29.5°C. We also assessed constant temperature incubations at 25, 29.5, and 34°C with 75% RSH. Incubation at 29.5°C resulted in successful hatching (73.3%), whereas temperatures of 25 and 34°C prevented hatching. However, hatching in natural nests occurred even between 34 and 36°C, provided that eggs were exposed to these temperatures <20% of the entire period of incubation, and only towards the end of incubation. Controlled incubation at 30% RSH prevented hatching. RSH linearly affected hatching success, phenotype, and performance of hatchlings: eggs incubated at 100% RSH had the greatest hatching success and produced the heaviest, largest, and fastest hatchlings. RSH correlated positively with sand depth on the beach, so that ≥75% RSH is ensured at the average depth of natural nests (~39.2 cm), resulting in successful hatching (74.3 ± 34.7%). The controlled incubation showed that temperature and hydric conditions had the most significant impact on hatching success, hatchling phenotype (size and weight), and hatchling performance. Maternal characteristics, however, were slightly less important. These results suggest that the impact of moisture should be taken into consideration in hawksbill turtle conservation projects. The thermal and hydric environments experienced by developing embryos should also be considered when evaluating how climate change affects marine turtles.

Pengaruh Suhu Inkubasi Terhadap Profil Ekspresi Gen Determinasi Seks Tukik Lepidochelys olivacea

Sex determination in turtles is not only based on genotype, but also depends on the incubation temperature. In addition, sex differentiation takes place during the thermosensitive period (TSP). This review article aims to examine the effect of incubation temperature on the expression profile of the sex determination gene for tortoises. Fertile eggs are incubated at two temperatures, namely the feminine temperature (30-33 ° C), and the masculine temperature (26-27 ° C). The results of bioreproduction and phenotype measurements of hatchlings, namely, embryo growth, incubation time, morphometrics, and locomotor performance of hatchlings were analyzed by regression analysis and Student's t test. The results of analysis from several literatures showed that the expression of aromatase and Rspond 1 genes (which play a role in ovarian differentiation) after TSP from incubated embryos at a higher feminine temperature and different from the masculine temperature. Regarding bioreproduction, the incubation period at the feminine temperature is shorter than the masculine temperature. Likewise embryos grow more rapidly at feminine temperatures. Incubation at feminine temperature had a significant effect on the phenotype of hatchlings, namely carapace width, plastron length and width, long flipper and hind arms, long neck, and flipper swing frequency.

Potential impacts of sea level rise and beach flooding on reproduction of sea turtles

Climate change scenarios predict an increase in global temperature and sea level rise. For sea turtles, the association between sea level rise, nest water content and temperature along the beach may influence embryo development and offspring survival. Over three consecutive years (2016 – 2018), a field experiment was conducted on Boa Vista island, Cabo Verde, to assess the potential impacts of tidal inundation on hatching success and hatchling phenotype in loggerhead sea turtles (Caretta caretta). Ninety-three groups of three nests each (N = 279) were relocated to a 5 km stretch of the same beach. Nests in each group were placed at regular intervals of 30 to 60 m across three zones of the beach: the lower “wet” zone, where tidal inundation was a risk, a middle zone, and the upper vegetated zone. Mean emergence and hatching success in the wet treatment was 12.0% and 18.9% respectively. In the middle zone it was 25.6% and 39.5%. In the vegetated zone it was 47.2% and 57.1%. Male hatchling production was severely reduced in the wet zone, probably by nest inundation, with the few hatchlings produced being predominantly male. Female body size and clutch size both had a significant impact on hatchling production and hatchling phenotype. In response to increased global temperatures, male hatchling production may continue in nests laid in areas of high flooding risk. The relocation of clutches to the upper beach areas as a conservation plan could be implemented to reduce the mortality of nests by high tide.

Incubating green turtle (Chelonia mydas) eggs at constant temperatures: Hatching success, hatchling morphology and post-hatch growth

Past studies applying constant-temperature incubation of eggs have involved all species of sea turtles, but rarely can we find a single one incubating eggs at three or more temperatures. Here, we incubated green turtle (Chelonia mydas) eggs from Ganquan Island, South China Sea, at five constant temperatures (26, 28, 30, 32 and 34°C) to determine hatching success, incubation length and hatchling phenotype at each test temperature and temperatures optimal for embryonic development. Temperature affected hatching success, incubation length and all seven examined hatchlings traits, and clutch origin affected three (head length, fore-flipper length and hind-flipper length) of the seven. Hatching success was lowest at 34°C and none of hatchlings hatched at this temperature was normal and survived over one week. The rate of embryonic development and the rate of post-hatch growth both were lowest at 26°C. Given that low survival and growth rates can translate into reduced individual fitness, we conclude that both 26°C and 34°C are unsuitable for incubation of C. mydas eggs. Post-hatch growth was fastest in hatchlings incubated at 30°C, and eggs of C. mydas incubated at temperatures around 30°C are more likely to produce mixed sexes. Accordingly, we conclude that temperatures within the range from 28°C to 32°C are generally optimal for embryonic development of C. mydas.

Temperature-induced changes in egg white antimicrobial concentrations during pre-incubation do not influence bacterial trans-shell penetration but do affect hatchling phenotype in Mallards

Microbiome formation and assemblage are essential processes influencing proper embryonal and early-life development in neonates. In birds, transmission of microbes from the outer environment into the egg’s interior has been found to shape embryo viability and hatchling phenotype. However, microbial transmission may be affected by egg-white antimicrobial proteins (AMPs), whose concentration and antimicrobial action are temperature-modulated. As both partial incubation and clutch covering with nest-lining feathers during the pre-incubation period can significantly alter temperature conditions acting on eggs, we experimentally investigated the effects of these behavioural mechanisms on concentrations of both the primary and most abundant egg-white AMPs (lysozyme and avidin) using mallard (Anas platyrhychos) eggs. In addition, we assessed whether concentrations of egg-white AMPs altered the probability and intensity of bacterial trans-shell penetration, thereby affecting hatchling morphological traits in vivo. We observed higher concentrations of lysozyme in partially incubated eggs. Clutch covering with nest-lining feathers had no effect on egg-white AMP concentration and we observed no association between concentration of egg-white lysozyme and avidin with either the probability or intensity of bacterial trans-shell penetration. The higher egg-white lysozyme concentration was associated with decreased scaled body mass index of hatchlings. These outcomes demonstrate that incubation prior to clutch completion in precocial birds can alter concentrations of particular egg-white AMPs, though with no effect on bacterial transmission into the egg in vivo. Furthermore, a higher egg white lysozyme concentration compromised hatchling body condition, suggesting a potential growth-regulating role of lysozyme during embryogenesis in precocial birds.

Hatchery efficiency as a conservation tool in threatened sea turtle rookeries with high embryonic mortality

Sea turtles are globally endangered and facing anthropogenic threats. To mitigate the negative impacts on sea turtle populations, different conservation strategies have been developed and implemented. For instance, when an endangered population suffers a high embryonic mortality from predation, human poaching, beach flooding or erosion, the relocation of clutches to safer and controlled areas can lower these threats. However, the use of hatcheries is controversially discussed, with some previous studies reporting negative results such as low hatching success, skewed sex ratio or phenotypic alterations of hatchlings. In this study, we evaluated the efficiency of beach hatcheries compared to in-situ incubation in Cabo Verde using data from six nesting seasons (2013–2018). During this study, several thousand high-risk clutches from loggerhead turtle (Caretta caretta Linnaeus, 1758) were relocated to a hatchery constructed within the Sea Turtle Natural Reserve (STNR, Boa Vista Island). Our findings confirmed that the in-situ nests within the STNR have extremely high egg mortality that is usually over 70%. Mean hatching success of clutches relocated to hatcheries was significantly higher than in-situ clutches with mean values between 70 and 85%. No significant differences were observed in the incubation period, the size and the behavioural response of hatchlings between relocated and in-situ clutches. As long as a sea turtle population is endangered and hatching success is low, clutch relocation programs which are designed to have an impact at the population level, are considered an efficient tool that contributes to its recuperation. Nevertheless, strict recommendations that increase hatching success while maintaining natural hatchling phenotype must be implemented.

Effect of Hatchery Nest Environment on Olive Ridley (Lepidochelys olivacea) Hatchling Performance

The nest environment plays an important role in influencing sea turtle hatchling phenotype. Increasing global temperatures can potentially cause detrimental changes to hatchling size and performance and ultimately influence their recruitment into the adult population. The mass nesting rookeries of olive ridleys in Odisha on the east coast of India are among the largest globally and the only major ones outside Central America. Many nests laid on the east coast of India are translocated to hatcheries as part of hatchery management practices. Therefore, it is imperative to understand the effects of temperature on hatchlings produced in hatcheries as well as site-specific factors in order to undertake appropriate climate-resilient hatchery management measures. This study examined the effect of temperature on the morphology and locomotor performance of hatchlings produced in 2 different hatcheries on the east coast: in Rushikulya, Odisha, and in Chennai, Tamil Nadu, India. We examined various size (body, flipper, and neck length) and performance (crawl speed, righting ability, and righting propensity) parameters for hatchlings at both hatcheries across a range of temperatures. We found that hatchling size and performance were significantly influenced by nest incubation temperature. Higher incubation temperatures resulted in smaller hatchling size, which in turn was correlated with lower performance variables. Incubation temperature also had a direct effect on hatchling performance independent of hatchling size. The effect of nest temperature on morphology and performance of hatchlings could influence their survival and recruitment rates, thus influencing population dynamics and resilience to climate change.

Clutch quality is related to embryonic development duration, hatchling body size and telomere length in the spined toad (Bufo spinosus)

AbstractReproductive success is often related to parental quality, a parameter expressed through various traits, such as site selection, mate selection and energetic investment in the eggs or progeny. Owing to the complex interactions between environmental and parental characteristics occurring at various stages of the reproductive event, it is often complicated to tease apart the relative contributions of these different factors to reproductive success. Study systems where these complex interactions are simplified (e.g. absence of parental care) can help us to understand how metrics of parental quality (e.g. gamete and egg quality) influence reproductive success. Using such a study system in a common garden experiment, we investigated the relationships between clutch hatching success (a proxy of clutch quality) and offspring quality in an amphibian species lacking post-oviposition parental care. We found a relationship between clutch quality and embryonic development duration and hatchling phenotype. We found that hatchling telomere length was linked to hatching success. These results suggest that clutch quality is linked to early life traits in larval amphibians and that deciphering the influence of parental traits on the patterns we detected is a promising avenue of research.

Effect of increased embryonic temperature during developmental windows on survival, morphology and oxygen consumption of rainbow trout (Oncorhynchus mykiss)

Temperature is a crucial environmental factor that influences physiological functions in fishes, and increased temperature during development can shape an organism's phenotype. An active line of inquiry in comparative developmental physiology is whether short-term exposure to thermal changes have lasting phenotypic effects. This is the first study to apply a developmental 3-dimensional critical window experimental design for a vertebrate, using time, temperature, and phenotypic response (i.e., variables measured). Rainbow trout (Oncorhynchus mykiss) are an anadromous species for which resident populations occupy freshwater environments that are likely impacted by variable and rising temperatures, particularly during embryonic development. To assess thermal effects on fish development, we examined trout hatchling phenotypes following rearing in constant temperatures (5, 10, 15 and 17.5 °C) and following exposure to increased temperature above 5 °C during specific developmental windows. Time to 50% hatch, hatchling mass and body length showed general trends of decreasing with increasing constant temperature, and survival was highest in constant 10 °C incubation. Thermally shifting embryos into 17.5 °C during gastrulation and organogenesis reduced survival at hatch compared to 10 °C, and exposure to 15 and 17.5 °C only late in development produced lighter and shorter hatchlings. Oxygen consumption rate (V̇o2) at organogenesis differed between embryos incubated constantly in increased temperature or exposed only during organogenesis, but generally we found limited temperature effects on V̇o2 that may be due to high data variability. Collectively, these results suggest that survival of rainbow trout hatchlings is most sensitive to 17.5 °C exposure during gastrulation and organogenesis, while warm water exposure later in development has greater impacts on morphology. Thus, trait-specific critical windows of thermal sensitivity exist for rainbow trout embryos that alter the hatching phenotype.

Investigating the effects of nest shading on the green turtle (Chelonia mydas) hatchling phenotype in the Ogasawara islands using a field-based split clutch experiment.

The Ogasawara Islands are an important rookery for the green turtle (Chelonia mydas) in the North Pacific. Green turtles possess temperature-dependent sex determination, and warmer incubation temperatures produce more females than males. Therefore, conservation practices such as nest shading may be required for this population to mitigate the effect of global warming on their sex ratio. To consider the application of such conservation practices in the Ogasawara population, it is fundamental to understand how artificially modified nest environments will affect green turtle hatchling phenotypes that influence their fitness. Here, we investigated the effects of nest shading on green turtle hatchling phenotypes in the Ogasawara population by using a split clutch experimentequally separating the clutch, relocating each half-clutch into an outdoor hatchery area either with or without shading, and observing the subsequent hatchling phenotype. Our results showed that the shading treatment produced hatchlings with a better self-righting response and a larger carapace size. Additionally, the shading treatment mostly reduced the production of hatchlings with a nonmodal scute pattern and produced hatchlings with a smaller unabsorbed yolk sac, which may be associated with their residual yolk mass. These results suggest that conservation practices such as shading could alter not only the sex ratio but also the hatchling phenotype that influences their fitness. Hence, our results suggest that applications of such conservation strategies must be carefully considered.

Incubation environment and parental identity affect sea turtle development and hatchling phenotype.

For reptiles, the incubation environment experienced by embryos during development plays a major role in many biological processes. The unprecedented rate of climate change makes it critical to understand the effects that the incubation environment has on developing embryos, particularly in imperiled species such as chelonians. Consequently, a number of studies have focused on the effects of different environmental conditions on several developmental processes and hatchling phenotypic traits. In addition to the incubation environment, it is also essential to understand how parental contributions can influence hatchling quality. This is the first study that investigates the effects of parental origin and incubation conditions on sea turtle embryonic development and hatchling phenotype in nests incubating in the field (rather than under controlled laboratory conditions). Here, we used the loggerhead sea turtle (Caretta caretta) to investigate the effects of parental origin (clutch), incubation temperature, and the nest hydric environment on embryonic growth, incubation durations, hatching success, and hatchling phenotype. Our results show that nest moisture and temperature affect embryo mass towards the last third of development, with hatchling size positively correlated with nest moisture content, and maternal origin had a strong impact on hatching success and hatchling size regardless of the incubation conditions. The results from this experiment identify multiple factors that affect turtle embryonic development under field incubation conditions, a fundamental consideration when interpreting the potential impacts of climate change on reptilian development.

Effect of incubation temperature on sex-dependent embryo mortality and morphological traits in Mallard.

Although birds have genetically determined sex, the sex ratio has been reported to deviate from parity in several studies. Temperature-dependent sex determination, which is common in reptiles, is absent in birds. However, females are able to adjust their investment into eggs according to the sex of the embryo, which may cause sex-specific embryonic mortality. Incubation temperature may also cause sex-biased embryonic mortality, and it may differentially affect the phenotype of male and female hatchlings. We aimed to investigate differences between male and female Mallard embryos regarding their egg size, mortality during incubation and hatchling phenotype in relation to incubation temperature. Mallard eggs were incubated under six constant incubation temperatures (ranging from 35.0 to 38.0 °C). Hatchlings were weighed, and their morphological traits were measured. We determined the sex of hatchlings and unhatched embryos by genetic analysis and found higher male embryonic mortality at 35.5 °C (44 males vs. 28 females) and a higher proportion of female hatchlings at 38 °C (24 males vs. 38 females); however, these results were not statistically significant. Our results suggest that Mallard females do not differentiate quantitatively between sexes during egg production. Male hatchlings were significantly larger but not heavier than females. The size difference between sexes was most pronounced at temperatures around 36 °C, which is the mean temperature of naturally incubated Mallard eggs.

Exposure of Avian Embryos to Cycling Incubation Temperatures Reduces Adult Bactericidal Ability.

In birds, the temperature at which eggs are incubated shapes many aspects of hatchling phenotype, but long-term effects are less studied. We studied the effect of incubation temperature and pattern on the subsequent development of innate immune function in Japanese quail (Coturnix japonica). We incubated quail eggs in one of three replicated treatments: control (37.5°C), low (36.0°C), and cyclical incubation. The cyclical treatment had the same average temperature as the low-temperature treatment (36.0°C) and an upper temperature that was the same as the control. When individuals were 5, 20, and 55 d of age (i.e., adults), we measured the ability of blood plasma to kill Escherichia coli. Throughout development there was a nonsignificant trend for immune function to be lower in the cycling treatment. In adulthood, however, individuals incubated at cycling temperatures had significantly lower immune function than control birds but did not differ from individuals incubated at constant low temperatures. Males and females responded similarly to the incubation treatment, but females developed a greater plasma bactericidal ability than males. We conclude that variation in innate immune function of adult birds is shaped by temperature fluctuations experienced during incubation.

Effects of incubation temperature on hatchling performance and phenotype in loggerhead sea turtle Caretta caretta

ESR Endangered Species Research Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials ESR 38:45-53 (2019) - DOI: https://doi.org/10.3354/esr00935 Effects of incubation temperature on hatchling performance and phenotype in loggerhead sea turtle Caretta caretta Alejandro Usategui-Martín1,*, Ana Liria-Loza1, Jeffrey D. Miller2, María Medina-Suárez3, Saray Jiménez-Bordón4, Valentín Pérez-Mellado5, Daniel Montero1 1University of Las Palmas de Gran Canaria, EcoAqua University Institute, Telde, Las Palmas 35214, Spain 2Biological Research and Education Consultants, Missoula, Montana 55801, USA 3NGO Cabo Verde Natura 2000, Sal Rei 5110, Cape Verde 4NGO Asociación para el Desarrollo Sostenible y Conservación de la Biodiversidad, Agüimes, Las Palmas 35118, Spain 5University of Salamanca, Department of Animal Biology, Salamanca 37007, Spain *Corresponding author: ausategui@gmail.com ABSTRACT: Under natural conditions sea turtle eggs are subjected to a changing thermal environment, but little is known about the effect of these temperature fluctuations during incubation on the performance and phenotype of hatchlings. The aim of this study was to determine how incubation temperature pattern (increasing or stable) and incubation temperature regime (low or high) affect incubation and hatching duration, hatching and emergence success, hatchling phenotype (carapace length and weight) and self-righting interval at hatching. Loggerhead sea turtle Caretta caretta (Linnaeus, 1758) clutches were collected at different beaches on the Cape Verde archipelago and divided among incubators with different temperature regimes and patterns. Minimum straight carapace length and weight of all individuals were measured at hatching. In addition, the hatching duration and the time interval required for each hatchling to self-right were recorded. Results showed that incubation temperature regimes influenced all studied parameters more than the increasing temperature pattern. Low incubation temperature regimes, both in the increasing and stable pattern, increased the incubation time, produced bigger hatchlings and caused a slower righting response compared to the high temperature regimes. An optimal range of incubation temperatures was determined by assessing the most favorable values for hatchlings, although some differences were found in the higher temperatures of this optimal range between different rookeries. This means that turtle incubation in the laboratory should, as far as possible, follow the natural incubation temperature fluctuation of the studied rookery. KEY WORDS: Loggerhead sea turtle · Caretta caretta · Incubation temperature regime · Incubation temperature pattern · Hatchling performance · Hatchling phenotype · North Atlantic Full text in pdf format PreviousNextCite this article as: Usategui-Martín A, Liria-Loza A, Miller JD, Medina-Suárez M, Jiménez-Bordón S, Pérez-Mellado V, Montero D (2019) Effects of incubation temperature on hatchling performance and phenotype in loggerhead sea turtle Caretta caretta. Endang Species Res 38:45-53. https://doi.org/10.3354/esr00935 Export citation Mail this link - Contents Mailing Lists - RSS Facebook - Tweet - linkedIn Cited by Published in ESR Vol. 38. Online publication date: February 07, 2019 Print ISSN: 1863-5407; Online ISSN: 1613-4796 Copyright © 2019 Inter-Research.

Different incubation patterns affect selective antimicrobial properties of the egg interior: experimental evidence from eggs of precocial and altricial birds.

Avian eggs contend with omnipresent microorganisms entering the egg interior, where they affect embryo viability and hatchling phenotype. The incubation behaviour and deposition of egg white antimicrobial proteins (AMPs) vary highly across the avian altricial-precocial spectrum. Experimental evidence of how these alterations in avian reproductive strategies affect the antimicrobial properties of the precocial and altricial egg interior is lacking, however. Here, we tested the egg white antimicrobial activity in eggs of two representative model species, from each end of the avian altricial-precocial spectrum, against potentially pathogenic and beneficial probiotic microorganisms. Eggs were experimentally treated to mimic un-incubated eggs in the nest, partial incubation during the egg-laying period, the onset of full incubation and the increased deposition of two main egg white AMPs, lysozyme and ovotransferrin. We moreover assessed to what extent egg antimicrobial components, egg white pH and AMP concentrations varied as a result of different incubation patterns. Fully incubated precocial and altricial eggs decreased their antimicrobial activity against a potentially pathogenic microorganism, whereas partial incubation significantly enhanced the persistence of a beneficial probiotic microorganism in precocial eggs. These effects were most probably conditioned by temperature-dependent alterations in egg white pH and AMP concentrations. While lysozyme concentration and pH decreased in fully incubated precocial but not altricial eggs, egg white ovotransferrin increased along with the intensity of incubation in both precocial and altricial eggs. This study is the first to experimentally demonstrate that different incubation patterns may have selective antimicrobial potential mediated by species-specific effects on antimicrobial components in the egg white.

Transplanting gravid lizards to high elevation alters maternal and embryonic oxygen physiology, but not reproductive success or hatchling phenotype.

Increased global temperatures have opened previously inhospitable habitats, such as at higher elevations. However, the reduction of oxygen partial pressure with increase in elevation represents an important physiological constraint that may limit colonization of such habitats, even if the thermal niche is appropriate. To test the mechanisms underlying the response to ecologically relevant levels of hypoxia, we performed a translocation experiment with the common wall lizard (Podarcis muralis), a widespread European lizard amenable to establishing populations outside its natural range. We investigated the impacts of hypoxia on the oxygen physiology and reproductive output of gravid common wall lizards and the subsequent development and morphology of their offspring. Lowland females transplanted to high elevations increased their haematocrit and haemoglobin concentration within days and maintained routine metabolism compared with lizards kept at native elevations. However, transplanted lizards suffered from increased reactive oxygen metabolite production near the oviposition date, suggesting a cost of reproduction at high elevation. Transplanted females and females native to different elevations did not differ in reproductive output (clutch size, egg mass, relative clutch mass or embryonic stage at oviposition) or in post-oviposition body condition. Developing embryos reduced heart rates and prolonged incubation times at high elevations within the native range and at extreme high elevations beyond the current range, but this reduced oxygen availability did not affect metabolic rate, hatching success or hatchling size. These results suggest that this opportunistic colonizer is capable of successfully responding to novel environmental constraints in these important life-history stages.

The hidden function of egg white antimicrobials: egg weight-dependent effects of avidin on avian embryo survival and hatchling phenotype.

ABSTRACTAvidin is a key egg white antimicrobial protein with strong binding capacity for biotin, an essential growth and immune cell precursor. As such, it is assumed to have a pronounced, though still poorly explored, effect on hatchling phenotype. We tested the effect of experimentally increased egg white avidin concentration (AVIDIN+) on hatching success, chick morphology, post-hatching growth performance and innate immune function in a model bird, Japanese quail (Coturnix japonica). Probability of embryo survival in the late embryonic phase increased with increasing egg weight in control eggs, but not in AVIDIN+ eggs. Chicks hatching from lighter AVIDIN+ eggs had a shorter tarsus than chicks hatching from heavier AVIDIN+ eggs. This suggests that an increase in egg white avidin favours embryo survival in lighter eggs during late embryogenesis, but at the expense of reduced structural body size. Plasma complement activity in 6-day-old AVIDIN+ chicks decreased with increasing body mass and tarsus length; the opposite was observed in control chicks, implying that the later post-hatching innate immune function of larger chicks was compromised by an increase in egg white avidin concentration. Here, we document an important role of egg white antimicrobials in maintenance of embryo viability, avian hatchling morphology and immune phenotype.

Non-invasive monitoring of the fertilization rate in sea turtle nests: comparison between two techniques

Egg fertilization rate is a defining event in the life history of reproducing oviparous species. However, for many terrestrial oviparous species, this parameter is only estimated after hatching, studying evidences of embryonic development in unhatched eggs. We compared the accuracy of this method with a second non-invasive technique based in the careful nest excavation within the first 96 hours after egg-laying and counting the proportion of eggs with a white spot in the shell. The study was conducted in a nesting population of loggerhead turtles (Caretta caretta) from Boavista Island (Republic of Cabo Verde). We found significant differences on the estimation of fertilization rate between both techniques. After hatching experimented researchers significantly overestimated the number of unfertilised eggs and this parameter was not correlated with the estimation after laying. The earlier estimation had no effect on hatching success and hatchling phenotype. There was no correlation between the number of alive embryos at laying and the hatching success. Unfertile eggs have no effect on survival of developing embryos withing a nest. Fertilization rate in loggerheads did not show spatial or temporal variation during nesting season. We proposed the implementation in sea turtle nesting monitoring programs of an annual, accurate and non-invasive estimation of egg fertilization rate based in the excavation of a sample of representative nests immediately after the formation of the white spot in the shell of developing embryos.

Thermal consequences of subterranean nesting behavior in a prairie-dwelling turtle, the Ornate Box Turtle (Terrapene ornata)

Many oviparous reptiles deposit eggs in excavated nest chambers, and the location and depth at which eggs are laid can affect predation risk, incubation duration, mortality rates, and hatchling phenotype. Among turtles, nest depth also influences incubation conditions of some large-bodied species, but nest depth is generally expected to vary less among small-bodied species. We monitored nesting behavior of Ornate Box Turtles (Terrapene ornata (Agassiz, 1857)) for two seasons in Illinois. We used direct observations to confirm that, among 31 nesting events, six females oviposited while beneath the substrate surface. Furthermore, comparisons of body length to nest depth indicated that five additional females likely also constructed nests while buried. Nests laid while females were underground were deeper, on average, than other nests (16.7 versus 11.2 cm), and while mean nest temperatures were similar between groups, temperature fluctuations and maximum temperatures were lower among nests that were laid while females were underground. Subterranean oviposition appears to have moderated incubation temperatures by allowing females to deposit eggs at greater depths than would be possible from the surface. This little-documented behavior may be a mechanism for this species to influence the incubation environment, which in turn may influence hatchling phenotypes.