Hatchling Phenotype Research Articles

Effects of incubation technique on proxies for olive ridley sea turtle (Lepidochelys olivacea) neonate fitness

Sea turtles and their nests face multiple threats on nesting beaches. Techniques have been developed to mitigate threats, these include relocating nests to fenced-off hatcheries or polystyrene boxes. The alteration of the nest’s natural environment may have direct effects on hatchling phenotype and locomotor performance. To test the effects of these two incubation conditions on proxies for hatchling fitness, we analysed locomotor performance (time to crawl 3 m and righting response) and phenotypic measures (weight and carapace length and width) of olive ridley sea turtle (Lepidochelys olivacea) hatchlings. We found that mean temperature was higher in hatcheries (30.5°C) than in polystyrene boxes (29.9°C) and that hatchlings incubated in polystyrene boxes had smaller straight carapace length (39.2 mm ± 2.0) and were significantly slower in crawl speed (CS) (0.0107 m s−1 ± 0.005) than those from hatcheries (SCL = 40.7 mm ± 1.3; CS = 0.018 m s−1 ± 0.005).

Myth busting? Effects of embryo positioning and egg turning on hatching success in the water snake Natrix maura.

It is a common belief that reptile eggs should not be turned after oviposition once the embryo has attached itself to the inner membrane of the shell as it might kill developing embryos. Here, we used 338 eggs from 32 clutches of the water snake Natrix maura to (1) thoroughly describe natural clutch arrangement, (2) experimentally assess the effects of natural embryo positioning and (3) egg turning on embryo metabolism, hatching success, and hatchling phenotype. Clutches contained, on average, 59% of embryos located at the top, 28% at the bottom, and 14% on a side of the egg. Larger females laid larger clutches with higher proportion of top located embryos. Top embryos displayed higher metabolic rates (heart rates), shorter incubation time, and produced lighter and shorter snakes than bottom embryos. Egg turning did not significantly influence egg development, hatching success or hatchling phenotypes. However, post-birth mortality was significantly higher in turned (37.5%) compared to unturned (4.5%) embryos, providing support to the common belief that eggs should not be moved from their natural position.

EXPRESSION PROFILE OF SEX DETERMINATION GENE, BIOREPRODUCTION, PHENOTYPE, AND LOCOMOTORY PERFORMANCES OF OLIVE RIDLEY, Lepidochelys olivacea INDUCED BY DIFFERENT INCUBATION TEMPERATURE

Sex determination in turtle species is not only based on genotype, but also rely on the incubation temperature. In addition, sexual differentiation takes place during the thermo-sensitive period (TSP). This study was conducted to determine the effects of incubation temperature on sex expression profile of determination gene, bioreproduction, phenotype, and locomotory performances of olive ridley turtle hatchlings. Fertile eggs incubated at two temperatures, namely feminine temperature (30-33°C), and masculine temperature (26-27°C). Value of cycle threshold (CT) measured during TSP, i.e 23-25 embryonic development stage, and after TSP, i.e 26-27 embryonic development stage using real time PCR techniques. Comparison of gene expression at both incubation temperatures were analyzed by ANOVA, and Student’s t test. Hatchling bioreproduction and phenotype measurement consist of the incubation period, embryo growth, morphometrics, and locomotori performances hatchlings were analyzed with regression analysis and Student’s t test. The results showed expression of both aromatase and Rspond 1 genes (which plays a role in ovarian differentiation) after the TSP that incubated at feminine temperature higher and different with masculine temperature. In conjunction with the bioreproduction and phenotype, the incubation period of feminine temperature shorter than that of masculine. Likewise, growth of the embryo of feminine temperature was faster than that of masculine. Incubation at feminine temperature significantly affect to carapace width, length and width of the plastron, long flippers and rear arms, long neck, and the frequency of the swing flippers. Keywords: thermo-sensitive period (TSP), gene expression, phenotype, Lepidochelys olivacea

Incubation temperature influences trade-off between structural size and energy reserves in mallard hatchlings.

The reproductive success of precocial birds depends on investments in clutch formation and incubation. Egg quality strongly affects the phenotypic traits correlated with survival of the hatchling, but parental ability to maintain incubation temperature can also influence hatchling outcomes. The effect of incubation temperature on hatchling phenotype has been widely studied in reptiles but not in birds. The aim of this study was to explore the effects of egg mass and incubation temperature on the incubation period, hatchability, and hatchling phenotype of the mallard (Anas platyrhynchos). Mallard eggs were incubated under six constant incubation temperatures (ranging from 35.0° to 39.0°C). Hatchlings were weighed, and their structural size was measured. Some hatchlings were used for an examination of residual yolk sac mass and basic chemical composition of the yolk-free body. All investigated phenotypic traits except for chemical composition were positively correlated with egg mass. Incubation temperature did not affect hatchling body mass, but increased temperatures led to a decreased yolk-free body mass and structural size of hatchlings and to increased yolk sac mass. Our results suggest that there is a trade-off between the yolk-free body size and energetic reserves in the form of the yolk sac and that this trade-off is modulated by incubation temperature.

Incubation temperature fluctuation does not affect incubation length and hatchling phenotype in the Chinese skink Plestiodon chinensis

Studies examining the effects of incubation temperature fluctuation on the phenotype of hatchling reptiles have shown species variation. To examine whether incubation temperature fluctuation has a key role in influencing the phenotype of hatchling Chinese skinks (Plestiodon chinensis), we incubated eggs produced by 20 females under five thermal regimes (treatments). Eggs in three treatments were incubated in three incubators, one set constant at 27°C and two ramp-programmed at 27±3°C and 27±5°C on a cycle of 12h (+) and 12h (−). The remaining eggs were incubated in two chambers: one inside a room where temperatures varied from 23.0 to 31.1°C, with a mean of 27.0°C; the other outside the room where temperatures varied from 20.2 to 35.3°C, with a mean of 26.1°C. We found that: (1) for eggs at a given embryonic stage at ovipositon, the mean rather than the variance of incubation temperatures determined the length of incubation; (2) most (egg mass, embryonic stage at oviposition, incubation length and all examined hatchling traits except tail length and locomotor performance) of the examined variables were affected by clutch; and (3) body mass was the only hatchling trait that differed among the five treatments, but the differences were tiny. These findings suggest that incubation temperature fluctuation has no direct role in influencing incubation length and hatchling phenotype in P. chinensis.

Consequences of induced hatching plasticity depend on predator community.

Many prey species face trade-offs in the timing of life history switch points like hatching and metamorphosis. Costs associated with transitioning early depend on the biotic and abiotic conditions found in the subsequent life stage. The red-eyed treefrog, Agalychnis callidryas, faces risks from predators in multiple, successive life stages, and can hatch early in response to mortality threats at the egg stage. Here we tested how the consequences of life history plasticity, specifically early hatching in response to terrestrial egg predators, depend on the assemblage of aquatic larval predators. We predicted that diverse predator assemblages would impose lower total predation pressure than the most effective single predator species and might thereby reduce the costs of hatching early. We then conducted a mesocosm experiment where we crossed hatchling phenotype (early vs. normal hatching) with five larval-predator environments (no predators, either waterbugs, dragonflies, or mosquitofish singly, or all three predator species together). The consequences of hatching early varied across predator treatments, and tended to disappear through time in some predation treatments, notably the waterbug and diverse predator assemblages. We demonstrate that the fitness costs of life history plasticity in an early life stage depend critically on the predator community composition in the next stage.

The behavioural and physiological strategies of bird and reptile embryos in response to unpredictable variation in nest temperature

Temperature profoundly affects the rate and trajectory of embryonic development, and thermal extremes can be fatal. In viviparous species, maternal behaviour and physiology can buffer the embryo from thermal fluctuations; but in oviparous animals (like most reptiles and all birds), an embryo is likely to encounter unpredictable periods when incubation temperatures are unfavourable. Thus, we might expect natural selection to have favoured traits that enable embryos to maintain development despite those fluctuations. Our review of recent research identifies three main routes that embryos use in this way. Extreme temperatures (i) can be avoided (e.g. by accelerating hatching, by moving within the egg, by cooling the egg by enhanced rates of evaporation, or by hysteresis in rates of heating versus cooling); (ii) can be tolerated (e.g. by entering diapause, by producing heat-shock proteins, or by changing oxygen use); or (iii) the embryo can adjust its physiology and/or developmental trajectory in ways that reduce the fitness penalties of unfavourable thermal conditions (e.g. by acclimating, by exploiting brief windows of favourable conditions, or by producing the hatchling phenotype best suited to those incubation conditions). Embryos are not simply passive victims of ambient conditions. Like free-living stages of the life cycle, embryos exhibit behavioural and physiological plasticity that enables them to deal with unpredictable abiotic challenges.

Effect of intermittent incubation and clutch covering on the probability of bacterial trans‐shell infection

Microbial infection is considered a critical cause of hatching failure in birds. Although several behavioural mechanisms are believed to improve reproductive success in birds, their direct effect on the risk of bacterial trans‐shell infection (BTSI) remains to be tested. Here, we focus on the protective roles of intermittent incubation and covering of the clutch with nest lining during the laying period, when eggs are highly susceptible to BTSI. To our knowledge, this study is the first to use culture‐independent PCR‐based methods to measure quantitative and qualitative indices of BTSI. In our experiment, we exposed Mallard Anas platyrhynchos eggs that were either intermittently incubated (I‐INCUB) or un‐incubated (I‐UNINCUB), and covered (COV) or uncovered (UNCOV) with nest lining. Hatchability of I‐INCUB eggs was twice that for I‐UNINCUB eggs. The presence and degree of BTSI had no effect on hatching success of experimental eggs. The residual weights of ducklings hatched from infected and I‐INCUB eggs were lower than those from uninfected and I‐UNINCUB eggs. In addition, ducklings originating from COV eggs were heavier than those hatched from UNCOV eggs. Intermittent incubation and clutch covering had no effect on the probability or degree of BTSI. Although the effect of BTSI is considered less detrimental in temperate birds, we show that the presence of BTSI inside the egg may significantly affect hatchling phenotype. This represents a novel insight into the role of BTSI in the reproductive success of birds and implies that the use of molecular PCR‐based methods is required in future studies for a better understanding of such causality.

Sun exposure, nest temperature and loggerhead turtle hatchlings: Implications for beach shading management strategies at sea turtle rookeries

Sea turtle incubation biology is tightly linked to nest thermal conditions due to the effect temperature has on hatching success, sex determination, morphology and locomotion performance. Because of this relationship between nest temperature and hatchling outcomes, global warming presents an immediate threat to many sea turtle nesting beaches throughout the world. Even small rises in nest temperatures may skew sex ratios and, raise egg mortality and influence hatchling phenotypes adversely, impacting on hatchling recruitment and ultimately species survival at some rookeries. The development of adaptive management practices capable of minimizing the effects of increasing global temperature on nest temperatures is thus a priority for animals exhibiting temperature-dependent sex-determination, such as sea turtles. Here, the relationship between solar radiation exposure and nest temperatures at the Mon Repos turtle rookery, south east Queensland, Australia was explored and the relationship between nest temperature and hatchling attributes examined. Shading decreased nest temperature, and higher nest temperatures were associated with smaller sized hatchlings that had decreased locomotion performance. The use of shading to minimize nest temperature is a management strategy that may be used to mitigate detrimental effects of increased global temperatures at some rookeries. Here, we explored the viability of natural shading options, such as the planting of trees behind nesting beaches, for combating the adverse effect of increased nest temperature caused by increased air temperatures.

Nest and maternal origin can influence morphology and locomotor performance of hatchling green turtles (Chelonia mydas) incubated in field nests

In numerous laboratory experiments involving the incubation of reptile eggs, both the maternal origin of eggs and the incubating environment (nest effect) have been demonstrated to influence hatchling phenotype. Although different hatchling phenotypes have been reported from natural nests, the separate effects of maternal origin and nest on hatchling phenotype in natural nests have not been demonstrated because in natural nests the two effects are confounded with each other. Here, we use a split clutch design to experimentally separate nest effects from maternal origin effects in field nests of green turtles (Chelonia mydas). We found both maternal origin and nest to influence hatchling morphology and locomotor performance in some but not all field nests. By using egg mass (maternal origin effect) and nest temperature (nest effect) in multiple regression analysis, we found maternal origin had a greater influence than nest temperature on the morphological attributes of hatchling mass and carapace size, but nest temperature had a greater influence than maternal origin on the performance attributes of self-righting time, self-righting propensity, swim thrust during the first 30 min of swimming, and power stroke rate during the first 30 min of swimming.

Effect of nest temperature on hatchling phenotype of loggerhead turtles (Caretta caretta) from two South Pacific rookeries, Mon Repos and La Roche Percée

La Roche Percée, in New Caledonia, is the most important loggerhead turtle rookery outside of Australia for the eastern Pacific genetic stock. The females nesting on this beach are genetically similar to the females found at the Mon Repos rookery in Queensland, Australia. This study shows how nest temperature affects the phenotype of genetically similar populations. During the 2010–11 breeding season, mean nest temperatures were significantly higher at La Roche Percée (31.8°C) than at Mon Repos (29.5°C) and the mean for the three-days-in-a-row maximum nest temperatures was also significantly higher at La Roche Percée (34.6°C), than at Mon Repos (31.7°C). Differences were found in mean hatching success (La Roche Percée 83 ± 3%, Mon Repos 96 ± 2%) and emergence success (La Roche Percée 76 ± 3%, Mon Repos 93 ± 3%). Hatchlings from La Roche Percée also had significantly lower fitness characteristics, having smaller carapace size (La Roche Percée 1565 ± 7 mm2, Mon Repos 1634 ± 5 mm2), slower self-righting times (La Roche Percée 4.7 ± 0.1 s, Mon Repos 2.7 ± 0.1 s) and slower crawling speed in terms of both absolute speed and body lengths per second (La Roche Percée 2.5 ± 0.2 cm s–1 or 0.57 ± 0.05 body lengths s–1, Mon Repos 4.6 ± 0.1 cm s–1 or 1.04 ± 0.02 body lengths s–1). Nest temperatures at La Roche Percée approached the upper limit of embryo thermal tolerance towards the end of incubation (34°C) and this condition may contribute to the lower hatching and emergence success and lower fitness characteristics of hatchlings at the La Roche Percée rookery.

Fluctuations in incubation temperature affect incubation duration but not morphology, locomotion and growth of hatchlings in the sand lizard Lacerta agilis (Lacertidae)

AbstractLi, H., Zhou, Z.‐S., Ding, G.‐H. and Ji, X. 2011. Fluctuations in incubation temperature affect incubation duration but not morphology, locomotion and growth of hatchlings in the sand lizard Lacerta agilis (Lacertidae). —Acta Zoologica (Stockholm) 00: 1–8.Studies looking for potential effects of temperature and temperature fluctuations on phenotypic traits of reptile hatchlings have shown species variation, but have not always allowed a distinction between effects of fluctuation per se and temperature extremes themselves. To examine whether incubation temperature fluctuation has a key role in influencing the phenotype of offspring, we incubated eggs of the sand lizard Lacerta agilis at one of the four temperature regimes (27, 27 ± 2, 27 ± 4 and 27 ± 6 °C). We found that: (1) hatchlings incubated under the four temperature regimes did not differ from each other in any of the morphological and physiological traits examined; (2) interactions that included temperature treatment did not affect any trait examined; (3) the mean incubation length was longer in the 27 ± 6 °C treatment than in the other three treatments; and (4) female hatchlings were shorter in head length and width but longer in snout‐vent length as well as abdomen length than males derived from the same‐sized egg. Our data show that both the type and the magnitude of temperature variation can affect incubation length. We found no evidence for phenotypic divergence in responses to temperature fluctuations during incubation and therefore suggest that temperature variation does not affect the phenotype of hatchlings in L. agilis.

Staying cool, keeping strong: incubation temperature affects performance in a freshwater turtle

AbstractIt is unclear how predicted rises in ambient temperature associated with climate change will impact upon the survivorship of oviparous reptiles. Given that the incubation temperature can influence hatchling phenotype, understanding how elevated temperatures during development can affect the ability of hatchlings to undertake routine behaviours is important, especially for threatened species. Here we tested if raising mean incubation temperature above natural levels altered the physiology of hatchlings to an extent that behavioural function was impaired. Firstly, incubation temperatures were recorded from nests of the freshwater turtle (Elusor macrurus) in the wild, and the observed thermal range (26–31 °C) used to define the experimental protocol. Then, freshly laid E. macrurus eggs were collected and incubated at three constant temperatures (26, 29 and 32 °C). Embryos incubated at 32 °C had the lowest hatching success. Those that did hatch were smaller than the other groups and had a reduced post‐hatch growth rate. On land, the ability of hatchling turtles to right themselves is critical, and the turtles incubated at 32 °C took 30‐times longer to do this than those incubated at 26 °C. Once in the water, hatchling turtles must be able to swim effectively to evade predation and obtain food items. During swimming trials the 32 °C group exhibited a lower mean stroke force (10.5±0.3 mN) and spent less time swimming (133.7±17.7 s) compared with hatchlings incubated at 29 °C (13.4±0.4 mN, 281.3±25.7 s) and 26 °C (15.7±0.5 mN, 270.8±28.5 s). The results of the present study illustrate that even slight rises in the mean incubation temperature, over that observed in the wild, can impact upon a hatchling's performance.

Shift in Thermal Preferences of Female Oviparous Common Lizards During Egg Retention: Insights into the Evolution of Reptilian Viviparity

Pregnant female Zootoca vivipara select lower body temperatures than males or nonpregnant females, and this shift in the thermal preferendum is believed to be related to optimising the conditions for embryogenesis. Thus, subjecting embryos to the higher temperature selected by males and non-gravid females might have detrimental effects on embryonic development and on hatchling fitness, according to predictions of the “maternal manipulation” hypothesis on the evolution of viviparity. To test the role of gestation environment on embryonic development in oviparous Z. vivipara, we kept a number of gravid females at the temperature selected by non-gravid females in a laboratory thermal gradient, whereas control females were allowed to regulate their body temperature without restrictions. Developmental stage at oviposition was more advanced for embryos of the experimental clutches, which were heavier than those of the control group. Forced gestation temperature also affected hatching success (58.62% in the experimental treatment vs. 97.37% in the control group). In addition, hatchlings from females subjected to high temperatures during pregnancy were smaller, had shorter head length and performed worse in running trials. Our results fulfil the prediction of the “maternal manipulation” hypothesis, and suggest that the shift in female body temperature during pregnancy optimizes embryogenesis and hatchling phenotype by avoiding the negative effects of the high incubation temperatures preferred by non-gravid females.

Determining optimal incubation temperature for a head-start program: the effect of incubation temperature on hatchling Burnett River snapping turtles (Elseya albagula)

This study monitored natural nest temperatures and examined the effect of incubation temperature on hatchling phenotype of the freshwater turtle Elseya albagula to determine the optimal temperature for a potential head-start program. Eggs were incubated at constant temperatures (26°C, 28°C and 30°C) to determine the influence of temperature on incubation period, hatchling morphology, swimming performance and post-hatching growth rate. Hatchlings incubated at 26°C had longer plastrons than hatchlings from 30°C and swam faster, three days after hatching, than did hatchlings incubated at either 28°C or 30°C. Incubation temperature also provided a source of variation in hatchling scute patterns. Clutch of origin influenced hatchling mass and size, growth at 184 days after hatching, and the swimming performance of 3-day and 75-day post-hatch hatchlings. Constant temperatures of 26°C and 28°C produced the highest hatching success and highest-quality hatchlings and are therefore recommended for incubation of eggs in a head-start program. In the field, unshaded nests experienced greater daily fluctuations in temperature and higher temperatures overall compared with shaded nests, such that unshaded nest temperatures approached the upper thermal limit to development.

Maternal investment and nutrient use affect phenotype of American alligator and domestic chicken hatchlings

Maternal investment by oviparous amniotes, in the form of yolk and albumen, and the mechanisms by which embryos use available energy and nutrients have a profound effect on embryo and, consequently, hatchling phenotype. Nutrient provisioning and uptake vary within and among oviparous taxa, avian and non-avian reptiles, due to differences and similarities in environment, behavior, and phylogeny. Eggs of crocodilians, the closest extant relatives to modern birds, are ideal models for examining modes of embryonic development, especially with regard to nutrient uptake, in non-avian reptiles and comparing them with those of birds. In this study, we investigated egg composition, embryo growth, and nutrient use in the domestic chicken ( Gallus gallus) and American alligator ( Alligator mississippiensis). We explored egg composition by separating and weighing components of fresh eggs. We measured embryo growth and nutrient usage by dissecting embryos and by obtaining samples of liquid from the amnion, digestive tract, and yolk sac throughout the last half of incubation. Variation in albumen mass contributed most to egg mass variation in chicken eggs, whereas alligator eggs were composed almost equally of yolk and albumen, although larger eggs contained proportionally more albumen and less yolk than smaller eggs. Both chicken and alligator albumen were mostly water (87% and 96%, respectively) although chicken albumen contained over three times more solid mass per gram than alligator albumen. In both species, yolk contained a high proportion of solids. Larger eggs produced larger hatchlings in both chickens and alligators, but albumen solids contributed to embryo mass only in chicken embryos. However, intact albumen proteins appeared in the stomach in embryos of both species. While the final disposition of albumen in alligators is unclear, variation in maternal investment of yolk at oviposition was responsible for nearly all of the variation in alligator hatchling phenotype, while both yolk and albumen contributed to chicken hatchling mass.

Slight differences in incubation temperature affect early growth and stress endocrinology of wood duck (Aix sponsa) ducklings

Early developmental experiences, such as incubation conditions, can have important consequences for post-hatching fitness in birds. Although the effects of incubation temperature on phenotype of avian hatchlings are poorly understood, recent research suggests that subtle changes in incubation conditions can influence hatchling characteristics, including body size and condition. We designed an experiment to explore the effects of incubation temperature on hatching success, survival to 9 days post hatch, growth and the hypothalamo-pituitary-adrenal (HPA) axis in wood ducks (Aix sponsa). Wood duck eggs were collected from nest boxes and experimentally incubated at three temperatures (35.0, 35.9 and 37.0 degrees C), each falling within the range of temperatures of naturally incubated wood duck nests. Survival and growth were monitored in ducklings fed ad libitum for 9 days post hatch. In addition, baseline and stress-induced plasma corticosterone concentrations were measured in 2 and 9 day old ducklings. Hatching success and survival to 9 days was greatest in ducks incubated at the intermediate temperature. Ducklings incubated at 35.9 degrees C and 37.0 degrees C had 43% higher growth rates than ducklings incubated at 35.0 degrees C. In addition, ducklings incubated at 35.0 degrees C had higher baseline (17-50%) and stress-induced (32-84%) corticosterone concentrations than ducklings incubated at 35.9 degrees C and 37.0 degrees C at 2 and 9 days post hatch. We also found a significant negative correlation between body size and plasma corticosterone concentrations (baseline and stress-induced) in 9 day old ducklings. To our knowledge, this is the first study to demonstrate that thermal conditions experienced during embryonic development can influence the HPA axis of young birds. Our results illustrate that subtle changes (<1.0 degrees C) in the incubation environment can have important consequences for physiological traits important to fitness.

The variance of incubation temperatures does not affect the phenotype of hatchlings in a colubrid snake, Xenochrophis piscator

It has been documented in some reptiles that fluctuating incubation temperatures influence hatchling traits differently than constant temperatures even when the means are the same between treatments; yet whether the observed effects result from the thermal variance, temperature extremes or both is largely unknown. We incubated eggs of the checkered keelback snake Xenochrophis piscator under one fluctuating (Ft) and three constant (24, 27 and 30 °C) temperatures to examine whether the variance of incubation temperatures plays an important role in influencing the phenotype of hatchlings. The thermal conditions under which eggs were incubated affected a number of hatchling traits (wet mass, SVL, tail length, carcass dry mass, fatbody dry mass and residual yolk dry mass) but not hatching success and the sex ratio of hatchlings. Body sizes were larger in hatchlings from incubation temperatures of 24 and 27 °C compared with the other two treatments. Hatchlings from the four treatments could be divided into two groups: one included hatchlings from the 24 and 27 °C treatments, and the other included hatchlings from the 30 °C and Ft treatments. In the Ft treatment, the thermal variance was not a significant predictor of all examined hatchling traits, and incubation length was not correlated with the thermal variance when holding the thermal mean constant. The results of this study show that the mean rather than the variance of incubation temperatures affects the phenotype of hatchlings.

Effects of egg size on Double-crested Cormorant ( Phalacrocorax auritus) egg composition and hatchling phenotype

Maternal investment of yolk and albumen in avian eggs varies with egg mass and contributes to variation in hatchling mass. Here we use the natural variation in mass and composition of Double-crested Cormorant ( Phalacrocorax auritus) eggs to examine consequences of variation in yolk and albumen mass on hatchling phenotype. The Double-crested Cormorant, a large bird with altricial young, lays eggs ranging in mass from 40 to 60 g and containing an average of 82% albumen and 18% yolk. Variation in Cormorant egg mass arises primarily from variation in the amount of albumen and water in the eggs; yolk mass remains relatively constant, contributing only 10% to egg mass variation. Likewise, variation in hatchling mass correlates positively with albumen mass and albumen solids contribute to hatchling dry mass. Thus, variation in Cormorant egg mass is primarily the result of variation in the amount of egg albumen, which contributes most to variation in hatchling mass. Similarities in egg composition of altricial birds, along with data presented here, suggest that variation in hatchling mass of all altricial birds may depend most on the amount of egg albumen, unlike species with precocial young that hatch from eggs with substantially more yolk.

Latent effects of egg incubation temperature on growth in the lizard Anolis carolinensis

Varied egg incubation temperatures can result in immediate effects on the phenotype of reptiles, and also latent effects that can augment or contradict effects evident at egg hatching. I examined the effects of incubation temperature on embryonic development, hatching morphology, and subsequent growth in multiple populations of the lizard Anolis carolinensis. Eggs from wild-caught females in four populations were incubated at up to three temperatures, 23.5, 27, and 30 degrees C. Measures of body size were collected immediately after hatching and weekly thereafter, while juveniles were maintained in a common laboratory environment for 8 weeks. Cooler incubation temperatures resulted in longer incubation periods but did not affect conversion of egg mass to hatchling mass. Incubation temperature did not affect hatchling mass or snout vent length (SVL), but did affect subsequent growth in both mass and SVL, which varied by population. Cooler incubation temperatures generally resulted in greater overall growth over 8 weeks of housing all juveniles in a common environment. In A. carolinensis, egg incubation temperature had latent effects on juvenile growth despite the absence of any detected immediate effects on hatchling phenotype. Therefore, the total impact and evolutionary importance of developmental environment should not be assessed or assumed based solely on the phenotype of reptiles at birth or hatching.