Ecological Networks of Allometric Growth,Feeding Behavior and Gut Microbiota in Chinese Alligator Hatchlings

Chinese alligator hatchlings in captivity are fragile and have a high mortality rate within first year.The body mass gain of reptile animals is closely related to their feeding behavior and gut microbiota.This study analyzed the intrinsic factors influencing the allometric growth of Chinese alligator hatchlings based on their body mass gain,feeding behavior,and gut microbiota.This information would enhance the health management of Chinese alligator hatchlings.There was a significant correlation between the total distance moved,the average number of conspecifics nearby,and body mass gain.Chinese alligator hatchlings with a greater growth rate showed greater activity and more independent behavior during feeding than those with a lower growth rate.Moreover,after feeding started,some functions of the gut microbiota showed significant relationships with growth rate and feeding activity.Chinese alligator hatchlings with a greater growth rate showed greater levels of heme biosynthesis than those with a lower growth rate,and feeding activity was inhibited by long-chain fatty acid biosynthesis.These results elucidate the relationships between health,feeding behavior,and the gut microbiota of Chinese alligator hatchlings.Understanding the intrinsic factors of their health and feeding behavior can improve the health management of Chinese alligator hatchlings in captivity for conservation.

Effects of Constant versus Fluctuating Incubation Temperatures on Hatching Success, Incubation Length, and Hatchling Morphology in the Chinese Skink (Plestiodon chinensis)

We incubated eggs ofPlestiodon chinensis under five constant （24, 26, 28, 30, and 32 ℃） and one fluctuating thermal regimes to examine the effects of constant versus fluctuating incubation temperatures on hatching success, incubation length, and hatchling morphology. The duration of incubation varied considerably among the six temperature treatments, whereas hatching success did not. The mean incubation length decreased as temperature increased in a nonlinear way, and increased as the thermal variance increased. Incubation temperature affected the body size （linear length and mass） and shape of hatchlings, with eggs incubated at 26, 28, and 30 ℃ producing larger and heavier hatchlings than did those incubated at 24 ℃, 32 ℃, or fluctuating temperatures. Our results showed that exposure of P. chinensis eggs to extreme temperatures for brief periods of time did not increase embryonic mortality and, in the fluctuating-temperature treatment, the thermal variance affected hatchling morphology more evidently than the thermal mean. Our results highlight the importance of the thermal variance in affecting embryonic development and hatchling morphology, and add further evidence that temperatures within the range of 26-30 ℃ are optimal for P. chinensis embryos.

Differences in Incubation Length and Hatchling Morphology among Five Species of Oviparous Phrynocephalus Lizards (Agamidae) from China

We incubated eggs of five Phrynocephalus species （P. albolineatus, P. axillaries, P. grumgrzimailoi, P. helioscopus and P. przewalskii） at three constant temperatures （24℃, 28℃ and 32℃） to examine differences in incubation length and hatchling morphology among species and among temperature treatments. We combined data from this study with those reported previously for P. frontalis and P. versicolor to examine whether embryonic stage at laying is a causal factor for interspecific variation in incubation length, and whether the phylogenetic relationship inferred from hatchling morphology is consistent with the relationship based on mitochondrial DNA data. Mean values for incubation length differed among the five species studied herein and, in all these five species, incubation length decreased at a decreasing rate as temperature increased. In none of the five species did hatchling size （snout-vent length and body mass） and other morphological variables differ among the three temperature treatments. The seven oviparous Phrynocephalus lizards found in China differ from each other in hatchling morphology, and embryonic stage at laying is a causal factor of inter- and intra-specific variation in incubation length. The phylogenetic relationship inferred from hatchling morphology is not always consistent with the currently known relationship based on mitochondrial DNA data. Data from this study and those reported previously allow the conclusion that any Phrynocephalus species may have its unique position along the axis defined by hatchling morphology.

Effects of Thermal and Hydric Conditions on Egg Incubation and Hatchling Phenotypes in Two Phrynocephalus Lizards

Flexible-shelled eggs of the lizards Phrynocephalus przewalskii and P. versicolor were incubated under different thermal and hydric conditions to elicit the effects of incubation environment on hatching success, embryonic development and duration as well as hatchling phenotypes. Embryogenesis of the two species was not sensitive to changes in the hydric environment except P. przewalskii incubated in 30°C group. Temperature significantly altered the duration of embryogenesis, with cooler temperatures leading to a longer incubation period. Hatching success was greater at 26 and 30°C than at 34°C. The hatchlings incubated at 26 and 30°C had longer snout-vent length, larger body mass, and better locomotor performance than those incubated at 34°C. Compared to P. przewalskii, P. versicolor had a shorter incubation period and yielded smaller hatchlings, which then had a higher survival rate in cooler and drier habitats. We conclude that an incubation temperature of 30°C would produce the best balance among developmental rate, hatching success, and post-hatching performance. We speculate that the upper temperature limit for incubation of P. versicolor eggs may be slightly higher than 34°C.

Maternal Thermal Effects on Female Reproduction and Hatchling Phenotype in the Chinese Skink(Plestiodon chinensis)

We maintained gravid Chinese skinks(Plestiodon chinensis) at three constant temperatures(25, 28 and 31 °C) during gestation, and randomly assigned eggs from each female to one of the same three temperatures for incubation to determine maternal thermal effects on female reproduction and hatchling phenotype. Maternal temperature affected egg-laying date, hatching success and hatchling linear size(snout-vent length, SVL) but not clutch size, egg size, egg component, and embryonic stage at laying. More specifically, females at higher temperatures laid eggs earlier than did those at low temperatures, eggs laid at 31 °C were less likely to hatch than those laid at 25 °C or 28 °C, and hatchlings from eggs laid at 31 °C were smaller in SVL. Our finding that maternal temperature(pre-ovipositional thermal condition) rather than incubation temperature(post-ovipositional thermal condition) affected hatching success indicated that embryos at early stages were more vulnerable to temperature than those at late stages. Our data provide an inference that moderate maternal temperatures enhance reproductive fitness in P. chinensis.

Assigning hatchlings to eggs:Is relative mass assignment an accurate method?

Background: Accurately assigning hatchlings to the eggs from which they hatched is a prerequisite to understanding how the composition and environment of eggs affect the growth and survival of nestlings. Correctly assigning hatchlings to their eggs can be a challenging endeavor, however, because multiple eggs within the same clutch can hatch at essentially the same time. Egg and hatchling mass are highly correlated in most bird species, and thus assigning eggs to hatchlings using their relative mass(e.g., matching the heaviest hatchling to the heaviest candidate egg) could prove extremely useful.Methods: To assess its potential utility, I applied relative mass assignment(RMA) retrospectively to a dataset of 133 Common Grackle(Quiscalus quiscula) nests in which all egg-hatchling dyads were determined unequivocally.Results: I found that RMA correctly assigned approximately 90% of hatchlings to their eggs when 2-4 hatchlings were present between checks. The number of nests in which hatchlings could not be assigned to their egg, however, increased monotonically from 13 to 46 to 78% for nests containing 2, 3, and 4 hatchlings, respectively, due to the greater likelihood that the mass of hatchlings or their candidate eggs was identical.Conclusions: Although RMA correctly identified the vast majority of egg-hatchling dyads, researchers should use this method with caution, because it will always inflate positive egg-size effects and thus could potentially result in erroneously reporting significant effects.

How incubation temperature affects hatchling performance in reptiles: an integrative insight based on plasticity in metabolic enzyme

Evaluating the effects of temperature variations on animals plays an important role in understanding the threat of climate warming.The effects of developmental temperature on offspring performance are critical in evaluating the effects of warming temperatures on the fitness of ovipa-rous species,but the physiological and biochemical basis of this developmental plasticity is largely unknown.In this study,we incubated eggs of the turtle Pelodiscus sinensis at low(24℃),medium(28℃),and high(32℃)temperatures,and evaluated the effects of developmental temperature on offspring fitness,and metabolic enzymes in the neck and limb muscles of hatchlings.The hatchlings from eggs incubated at the medium temperature showed better fitness-related performance(righting response and swimming capacity)and higher activities of metabolic enzymes(hexokinase,HK;lactate dehydrogenase,LDH)than hatchlings from the eggs incubated at high or low temperatures.In addition,the swimming speed and righting response were significantly correlated with the HK activities in limb(swimming speed)and neck(righting response)muscles,suggesting that the developmental plasticity of energy metabolic pathway might play a role in determining the way incubation temperature affects offspring phenotypes.Integrating the fitness-related performance and the activities of metabolic enzymes,we predict that the P sinensis from high latitude would not face the detrimental effects of climate warming until the average nest temperatures reach 32℃.

Influence of incubation temperature on sea turtle hatchling quality

Since the 1980s it has been known that incubation temperature influences the sex ratio of sea turtle hatchlings emerging from their nests,and there has been much speculation on how global climate change might threaten sea turtle populations by raising nest temperatures and causing highly female-biased hatchling sex ratios.More recently,studies have indicated that incubation temperature can also influence the size and locomotor performance of sea turtle hatchlings.Here I review recent studies that have explored the influence of incubation temperature on sea turtle hatchling quality in terms of hatchling morphology and locomotor performance.I also discuss the likely underlying mechanisms responsible for incubation temperature-induced differences in hatchling locomotor performance,and how an increase in nest temperature associated with global warming might affect recruitment of sea turtle hatchlings.

Reduced egg shell permeability affects embryonic development and hatchling traits in Lycodon rufozonatum and Pelodiscus sinensis

The response of embryos to unpredictable hypoxia is critical for successful embryonic development,yet there remain significant gaps in our understanding of such responses in reptiles with different types of egg shell.We experimentally generated external regional hypoxia by sealing either the upper half or bottom half of the surface area of eggs in 2 species of reptiles(snake[Lycodon rufozonatum]with parchment egg shell and Chinese softshelled turtle[Pelodiscus sinensis]with rigid egg shell),then monitored the growth pattern of the opaque white patch in turtle eggs(a membrane that attaches the embryo to the egg shell and plays an important role in gas exchange),the embryonic heart rate,the developmental rate and the hatchling traits in turtle and snake eggs in response to external regional hypoxia.The snake embryos from the hypoxia treatments facultatively increased their heart rate during incubation,and turtle embryos from the upper-half hypoxia treatment enhanced their growth of the opaque white patch.Furthermore,the incubation period and hatching success of embryos were not affected by the hypoxia treatment in these 2 species.External regional hypoxia significantly affected embryonic yolk utilization and offspring size in the snake and turtle.Compared to sham controls,embryos from the upper-half hypoxia treatment used less energy from yolk and,therefore,developed into smaller hatchlings,but embryos from the bottom-half hypoxia treatment did not.

Contributions of source population and incubation temperature to phenotypic variation of hatchling Chinese skinks

Phenotypic plasticity and local adaptation are viewed as the main factors that result in between-population variation in phenotypic traits,but contributions of these factors to phenotypic variation vary between traits and between species and have only been explored in a few species of reptiles.Here,we incubated eggs of the Chinese skink(Plestiodon chinensis)from 7 geographically separated populations in Southeast China at 3 constant temperatures(24,28,and 32℃)to evaluate the combined effects of dutch origin,source population,and incubation temperature on hatchling traits.The relative importance of these factors varied between traits.Nearly all examined hatchling traits,including body mass,snout-vent length(SVL),tail length,head size,limb length,tympanum diameter,and locomotor speed,varied among populations and were affected by incubation temperature.Measures for hatchling size(body mass and SVL)varied considerably among clutches.Source population explained much of the variation in hatchling body mass,whereas incubation temperature explained much of the variation in other examined traits.Our results indicate that between-population variation in hatchling traits of P.chinensis likely reflects the difference in natural incubation conditions and genetic divergence.

Increased CO2 Levels during the First Half of Incubation at High Altitude Modifies Embryonic Development of Fertile Leghorn Breeder Eggs

The exchange of oxygen (O2) and carbon dioxide (CO2) within an incubator has a significant impact on embryonic development (ED) and hatching processes. This study examines the influence of non-ventilation (NV) conditions during the first ten days of incubation at high altitudes on Leghorn hens hatching eggs. Five hundred four hatching eggs were equally divided into three treatment groups and placed in twelve incubators (R = 4). The first group was subjected to standard ventilated conditions (V) during the setting phase. The ventilation inlet holes of the remaining incubators in the NV treatments were closed with either micropore (M) or polypropylene (P) tape, referred to as NVM and NVP groups, respectively. These two different airtight settings were intended to allow for a gradual rise in CO2 naturally generated by the embryos. Results indicate that carbon dioxide concentration gradually increased during the first half of incubation, reaching 1.42% in the NVM group and 1.20% in the NVP group, while the V condition group remained at 0.15%. From 10 days of incubation onwards, normal V conditions were restored in all incubators. The highest hatchability of fertile eggs (HFE) was shown by the NVP group (55.7%), followed by the V (52.6%) and NVM (38.6%) groups. The NVP group showed a greater yolk-free body mass (YFBM) from 10 days of incubation until the hatch basket transfer. NV conditions during the first 10 days of incubation at high altitude produced higher YFBM with gradually decreasing yolk sac mass. In comparison to the NVM and V conditions, the particular NVP condition showed a beneficial impact on the quality of hatched chicks. Sustaining NVP condition (1.2% of CO2) throughout the first half of incubation at high altitude generated the optimal environment in the incubator ensuring the best hatchability results. This study highlights how important it is for hatchery managers to recognize the influence of low O2 and high levels of CO2 on the development trajectories of Leghorn embryos during early incubation at high altitudes.

Sexual Dimorphism, Female Reproductive Characteristics and Egg Incubation in an Oviparous Forest Skink(Sphenomorphus incognitus) from South China

We studied sexual dimorphism and female reproduction in an oviparous forest skink （Sphenomorphus incognitus） from South China. We incubated eggs under five thermal regimes （22, 25, 28, 25 ± 3 and 27± 5℃） to examine the effects of constant versus fluctuating temperatures on incubation length and hatchling morphology. In our sample the largest male and female were 110 mm and 108 mm snout-vent length （SVL）, respectively. Adult males and females did not differ in mean SVL; adult males were larger in head size （both length and width）, longer in fore- and hind-limb lengths and shorter in abdomen length than females of the same SVL. Accordingly, we conclude that S. incognitus is a sexually monomorphic species in terms of SVL but shows sexual dimorphism in head size, abdomen length and appendage length. Females laid a single clutch of 3-10 eggs per breeding season from early May to mid- August, with larger females generally laying more （but not always larger） eggs per clutch than did smaller ones. Embryonic stages at laying ranged from Dufaure and Hubert＇s （1961） stage 31 to 32, with a mean stage of 31.3. The positive relationship between clutch mass and female SVL was not significant. The offspring size-number trade-off does not exist in S, incognitus, as revealed by the fact that egg mass was independent of relative fecundity. Incubation length decreased as temperature increased, and stable temperatures resulted in delayed hatching. Hatchlings incubated under the five thermal regimes did not differ from each other in any examined trait, suggesting that S. incognitus is among oviparous reptilian species where incubation temperature has no role in modifying hatchling morphology as long as eggs are not exposed to extreme temperatures for prolonged periods of time.

Food restriction affects maternal investment but not neonate phenotypes in a viviparous lizard

Food availability significantly affects an animal＇s energy metabolism, and thus its phenotype, survival, and reproduction. Maternal and offspring responses to food conditions are critical for understanding population dynamics and life-history evolution of a species. In this study, we conducted food manipulation experiments in field enclosures to identify the effect of food restriction on female reproductive traits and postpartum body condition, as well as on hatchling phenotypes, in a lacertid viviparous lizard from the Inner Mongolian desert steppe of China. Females under low-food availability treatment （LFT） had poorer immune function and body condition compared with those under high-food availability treatment （HFT）. The food availability treatments significantly affected the litter size and litter mass of the females, but not their gestation period in captivity or brood success, or the body size sprint speed, and sex ratio of the neonates. Females from the LFT group had smaller litter sizes and, therefore, lower litter mass than those from the HFT group. These results suggest that female racerunners facing food restriction lay fewer offspring with unchanged body size and locomotor performance, and incur a cost in the form of poor postpartum body condition and immune function. The flexibility of maternal responses to variable food availability represents an important life strategy that could enhance the resistance of lizards to unpredictable environmental change.

Sexual Dimorphism,Female Reproductive Characteristics and Embryonic Thermosensitivity in the Tonkin Forest Skink(Sphenomorphus tonkinensis)from Hainan,South China

We collected 75 adult Tonkin forest skinks(Sphenomorphus tonkinensis) from Hainan, South China and incubated eggs at four constant temperatures ranging from 22 ℃ to 28 ℃ to study sexual dimorphism, female reproductive characteristics and embryonic thermosensitivity. The largest male was 53.4 mm snout-vent length(SVL), and the largest female was 54.3 mm SVL. The mean SVL was slightly greater in adult females(49.9 mm) than in adult males(48.8 mm), but the difference was not significant.Head length, head width, fore-limb length and hindlimb length were longer in adult males and abdomen length was longer in adult females after accounting for SVL. Accordingly, we conclude that S. tonkinensis is basically a sexually size-monomorphic species with sexual dimorphism in head size, abdomen(trunk)length and limb size. Females laid up to two clutches of 1–4 eggs each per egg-laying season from February to May. Egg mass, clutch size and clutch mass were independent of female SVL. Embryonic stages at laying varied from Dufaure and Hubert’s stage 30 to 31. With female SVL held constant, the negative correlation between egg mass and clutch size was not significant, suggesting that the offspring(egg) sizenumber trade-off between is not evident or eggs are well optimized for size in S. tonkinensis. None of the eggs at 28 ℃ hatched;hatching success was lower at 22 ℃ than at 24 ℃ or 26 ℃. The mean incubation length was 52.9 d at 22 ℃, 40.4 d at 24 ℃ and 33.6 d at 26 ℃. Hatchlings from eggs incubated at 22 ℃,24 ℃ and 26 ℃ did not differ morphologically at hatching, suggesting that temperatures within this range do not differentially affect hatchling morphology in S. tonkinensis.

Perch Associated Expression of Phenotypic Plasticity in Limb Development and Sprint Speed in Agamid Lizard Calotes versicolor: A Laboratory Study

New born hatchlings of Calotes versicolor were reared in terrarium having narrow or wide perches for a period of 4-month and their snout vent length（SVL）, tail, fore and hindlimb lengths were measured at monthly intervals. Limb postures（closer to the body or spread away from the body） were also recorded. The sprint speed was recorded in two and four-month old lizards on a 1 m long race track providing 45° or 60° slope. In both the groups, SVL and tail lengths were comparable but the limb lengths and their growth rates were significantly greater in lizards of wider perch group. The lizards reared with narrow perches positioned their limbs closer to the body; while those reared on wider perches spread their limbs away from their body. Further, the latter exhibited significantly higher sprint speed regardless of the slope of the race track over those of narrow perch group. Sprint speeds of lizards in both groups were correlated with the limb sizes. The study showed that the lizards reared on narrow or wide perches exhibited divergent adaptive responses（phenotypic plasticity） by developing longer or shorter limbs and corresponding changes in their sprint speeds. These findings support the idea that availability of perch structure during early development evokes adaptive plasticity in the limb development and associated locomotory performance in arboreal lizards like C. versicolor.

Biological Value of Maggot Meal as a Replacement for Fishmeal in the Diets of African Giant Snail （Achatina spp.） Hatchings

Poverty, inadequate dietary intake, and diseases are the major causes of malnutrition in Nigeria. Averagely, Nigerians consume about 5.5 g of animal protein per day which is low compared to the minimum of 30 g per person per day as recommended by Food and Agricultural Organization. The concept of household food security ensures that adequate food can be obtained, either through home production or purchases. Snail production is one of the means through which these ills could be eliminated. Protein deficiency that is endemic in developing nations can be reduced through the domestication of micro-livestock like snail which is rich in protein and iron. Sixty Achatina achatina hatchlings were used in a 90 days feeding trial. The hatchlings were assigned to four treatments in a Completely Randomized Design with three replicates each. Maggot meal was incorporated at the levels of 0.6, 1.4, and 2 kg per 100 kg of feed in treatments 2, 3 and 4, respectively. Treatment 1 had no maggot meal and served as the control. Results showed that snail weight, shell length and shell width increased with increase in the levels of maggot meal. Hatchlings on T3 and T4 had statistically similar values （P 〉 0.01） which were significantly （P 〈 0.01） higher than values obtained for hatchlings on T1 and T2 .Weight gain and feed conversion values of hatchlings on T3 and T4 were also significantly higher than values observed for hatchlings on T1 and T2. Therefore, maggot meal could effectively replace fishmeal in the diet of African giant snail hatchlings.

The Probable Cause for Nesting Pattern of Olive Ridley (Lepidochelys olivacea) at Ramnagar Beach, North East Coast of Andaman Island, India

The nesting behaviour of sea turtles remains a subject to study, due to their enigmatic pattern of seasonal breeding activities. Over a period of time, several reports have been made in this context associated with the nesting behaviour of the Olive Ridley turtles. In the present study, characteristics of the breeding beach and nesting pattern of Olive Ridley (Lepidochelys olivacea) at Ramnagar along N-E coast of Andaman Islands were investigated, during the nesting periods 2016-2017. The study area hosts Olive Ridley, the dominant sea turtles with more than 300 individuals nesting each year. For this study, the number of sea turtles visited, nested, the sediment characters, salinity, and temperature were taken. The exposed sandy nesting beach characteristics are prone to varying degrees of morphological changes every day. The results depict that even though similar grain size (Coarse Sand to Fine Sand and Very well sorted to Poorly Sorted), with an ambient incubating temperature, pH and salinity with wide nesting area, the selective nesting in the particular location of the beach identified because of comfortable energy conditions in the waters (1.5 m/s) favours the female turtles to reach the beach at the preferable site of Ramnagar and nest.

Phenotypic consequences of maternally selected nests:a cross-fostering experiment in a desert lizard

Despite the importance of maternally selected nests in shaping offspring phenotypes,our understanding of how the nest environment affects embryonic development and offspring traits of most non-avian reptiles is rather limited largely due to the logistical difficulty in locating their nests.To identify the relative contributions of environmental(temporal[seasonal]and spatial[nest-site])and intrinsic(clutch)factors on embryonic development and offspring traits,we conducted a cross-fostering experiment by swapping eggs between maternally-selected nests of the toad-headed agama(Phrynocephalus przewalskii)in the field.We found that nest environment explained a large proportion of variation in incubation duration,hatching success,and offspring size and growth.In contrast,clutch only explained a small proportion of variation in these embryonic and offspring traits.More significantly,compared with spatial effects,seasonal effects explained more phenotypic variation in both embryonic development and offspring traits.Eggs laid early in the nesting season had longer incubation durations and produced smaller hatchlings with higher post-hatching growth rates than did later-laid eggs.Consequently,hatchlings from early-laid eggs reached larger body sizes prior to winter.In addition,we found that female toad-headed agama did not select nests specific to reaction norms of their own offspring because hatchlings from original or translocated nests had similar phenotypic traits.Overall,our study demonstrates the importance of seasonal variation in nest environments in determining embryonic development and offspring phenotypes,which has not been widely appreciated at least in non-avian reptiles.

Innate phase behavior in the desert locust, Schistocerca gregaria

Detailed aspects of the transition from the solitarious to the gregarious phase in the framework of locust ecology are undoubtedly most important for understanding locust phase polyphenism. Nevertheless, due to obvious difficulties in studying the solitarious phase in nature, such information is limited and mostly available from research carried out under laboratory conditions. In the current study, we examined the dispersal patterns of newly hatched locust nymphs in a laboratory setup that simulated seminatural conditions. This was carried out with no previous manipulation of the nymphs other than controlling their parental density. We comparatively tested the spatial distribution of newly hatched nymphs on perches located at different ranges within an emergence arena, and the expected Poisson （random） distribution. Hatchlings were found to disperse among the perches in a pattern significantly different from that expected by random. Irrespective of their parents＇ phase, the observed distributions of all nymphs were clearly clumped, similar or close to those expected for gregarious locusts. It seems that rather than emerging with a parentally derived and predetermined phase, hatchlings have an independent default or innate behavioral state, which reflects at least tolerance if not attraction to conspecifics. The typical phase behavior may later become dominant under the appropriate environmental conditions. These results imply novel perspectives on locust phase transformation, which contribute to our understanding of the formation of locust crowds under field conditions. These should be considered in any rationale for developing a preventative management strategy of locust populations.

Can snakes use yolk reserves to maximize body size at hatching?

We experimentally miniaturized freshly laid eggs of the Chinese cobra Naja atra(Elapidae)by removing^10%and^20%of original yolk.We tested if yolk-reduced eggs would produce 1)normal-sized hatchlings with invariant yolk-free body mass(and thus invariant linear size)but dramatically reduced or even completely depleted residual yolk,2)smaller hatchlings with normal­sized residual yolk but reduced yolk-free body mass,or 3)smaller hatchlings of which both yolk-free body mass and residual yolk are proportionally reduced.Yolk quantity affected hatchling linear size(both snout-vent length and tail length)and body mass.However,changes in yolk quan­tity did not affect incubation length or any hatchling trait examined after accounting for egg mass at laying(for control and sham-manipulated eggs)or after yolk removal(for manipulated eggs).Specifically,yolk-reduced eggs produced hatchlings of which all major components(carcass,re­sidual yolk,and fat bodies)were scaled down proportionally.We show that snakes cannot use yolk reserves to maximize their body size at hatching.Furthermore,our data also suggest that the parti­tioning of yolk in embryonic snakes is species-specific.