Hatchling Morphology Research Articles

Do different yolk androgens exert similar effects on the morphology or behaviour of Japanese quail hatchlingsCoturnix japonica?

Avian eggs contain variable levels of several maternal androgens that may all be important in adjusting offspring phenotype at the individual or brood level. Most studies have focused on experimental manipulations of testosterone (T), and the other yolk androgens such as androstenedione (A4) and 5‐alpha‐dihydrotestosterone (DHT) were so far neglected. However, in species where the amount of A4in the yolk much exceeds that of the other androgens, A4could represent the dominant agent of androgen‐mediated maternal effects, in which case manipulations of T would be misdirected. We conducted our study in a species with high yolk A4and relatively low T and DHT levels, the Japanese quailCoturnix japonica. We injected unincubated eggs with a physiological dose of either A4, T, or DHT, and measured hatchling growth, as well as behaviour in an open field test. T treatment non‐significantly increased social reinstatement behaviour in the open field test, but it seemed to significantly suppress early skeletal growth and mass gain. The A4and DHT treatments, in contrast, significantly increased reinstatement behaviour, but did not affect mass and size growth. These results suggest that future investigations should view yolk androgens as integrated components of the complex yolk steroid environment.

Temperature fluctuations affect offspring sex but not morphological, behavioral, or immunological traits in the Northern Painted Turtle (Chrysemys picta)

Evolutionary theory predicts that when phenotypic variation arises during development that differently influences the fitness of each sex, selection should favor the maternal ability to match offspring phenotype to the sex that incurs a fitness benefit from that phenotype. In reptiles with temperature-dependent sex determination, the temperatures experienced during incubation can influence numerous phenotypic parameters, including sex. To mimic more naturalistic conditions, this experiment examined how variation in temperature fluctuations affects offspring sex as well as a suite of phenotypic parameters having putative fitness consequences in the Northern Painted Turtle ( Chrysemys picta (Schneider, 1783)). We also characterized variation in natural nest temperatures, including the daily temperature range, related to the vegetation cover surrounding the nest. We found that temperature fluctuations did not affect hatchling morphology, immune response, or behavior, but did significantly affect offspring sex ratios. Thermal profiles of natural nests were related to the amount of surrounding vegetation. Results suggest that nest-site choice by females could influence the sex of their offspring, but we found no evidence that variation in temperature fluctuations adaptively matches offspring sex and phenotype.

Salinity-induced heterokairy in an upper-estuarine population of the snail Radix balthica (Mollusca: Pulmonata)

AB Aquatic Biology Contact the journal Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections AB 9:95-105 (2010) - DOI: https://doi.org/10.3354/ab00231 Salinity-induced heterokairy in an upper-estuarine population of the snail Radix balthica (Mollusca: Pulmonata) Oliver Tills*, John I. Spicer, Simon D. Rundle Marine Biology and Ecology Research Centre, University of Plymouth, Drake Circus, Plymouth PL4 8AA, UK *Email: oliver.tills@plymouth.ac.uk ABSTRACT: Climate change is predicted to increase sea level and cause saline intrusion of coastal freshwaters. This will have consequences for freshwater organisms inhabiting such areas; developmental phenotypic plasticity may facilitate the persistence of freshwater species under such scenarios of increased salinity. Here we investigated developmental plasticity under different salinity treatments (S = 2, 5, 7 and 9, with artificial pond water [APW] and deionised water [S = 0] as controls) in embryos from an upper-estuarine population of the gastropod Radix balthica. We focused on plasticity in the timing of developmental events (heterokairy) at different salinities, including the time of onset (relative and absolute) of 10 developmental events and duration of 4 developmental stages; we also assessed whether salinity affected hatchling morphology and embryonic cardiac activity. There were significant differences in the absolute time of onset of several events with increased salinity, including a delayed first heartbeat in S5 and S7 compared with APW and in the relative time of onset of eye spot formation, first heartbeat and foot attachment between treatments. Stage duration also varied between salinity treatments: the hippo developmental stage lasted significantly longer in S7 compared with APW and development overall was prolonged in S7, with embryos in S9 not developing past the trochophore stage. Salinity also affected both shell size and shell shape of hatchlings. Hence salinity influences the time of onset (absolute and relative) of developmental events and duration of several developmental stages and the morphology of hatchling snails, although the mechanistic basis and fitness implications are, as yet, unknown. KEY WORDS: Developmental phenotypic plasticity · Seawater intrusion · Embryonic development · Sequence changes Full text in pdf format PreviousCite this article as: Tills O, Spicer JI, Rundle SD (2010) Salinity-induced heterokairy in an upper-estuarine population of the snail Radix balthica (Mollusca: Pulmonata). Aquat Biol 9:95-105. https://doi.org/10.3354/ab00231 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in AB Vol. 9, No. 1. Online publication date: April 06, 2010 Print ISSN: 1864-7782; Online ISSN: 1864-7790 Copyright © 2010 Inter-Research.

Influence of incubation temperature on morphology and locomotion performance of Leatherback (Dermochelys coriacea) hatchlings

The journey of Leatherback ( Dermochelys coriacea (Vandelli, 1761)) hatchlings from nest to the sea is a vulnerable life-history stage. Studies have shown that nest incubation temperatures influence hatchling morphology and locomotor performance, which may affect hatchling fitness. We obtained incubation temperature profiles from 16 Leatherback nests in Tobago, West Indies, during the 2008 nesting season (March–June). There was significant variation among mean nest incubation temperatures, which had a significant influence on hatchling morphology. Using principal components analysis, we determined the morphological traits that explained the most variation among hatchlings, which allowed investigation of the relationship between hatchling morphology and terrestrial locomotion speed. Hatchlings with a narrower carapace width and longer flipper reach (produced at lower incubation temperatures) had significantly faster terrestrial speed and total run time than those with opposite characteristics (produced at higher incubation temperatures). Our results demonstrate that lower incubation temperatures produce hatchlings with traits that are significantly advantageous to terrestrial locomotion. These findings suggest that nest incubation temperature is important in determining hatchling fitness, as nest incubation temperature significantly influences hatchling morphology and locomotor capabilities. This study supplements related findings in Green Turtles ( Chelonia mydas (L., 1758)), but also illustrates some unique features in Leatherbacks.

The effects of incubation temperature on the morphology and composition of Australian Brush-turkey (Alectura lathami) chicks

Environmental heterogeneity during embryonic development generates an important source of variation in offspring phenotypes and can influence the evolution of life histories. The effects of incubation temperature on offspring phenotypes in reptiles has been well documented but remains relatively unexplored in birds as their embryos typically develop over a narrow range of temperatures. Megapode birds (Order Galliformes; Family Megapodiidae) are unique in that their embryos tolerate and develop over a wide range of incubation temperatures, yet little is known of the effect that temperature has on hatchling morphology and composition. Australian Brush-turkey eggs collected on the day of laying were incubated in the laboratory under constant temperatures of 32, 34 and 36 degrees C until hatching in order to determine the influence of temperature on hatchling mass, size and composition. The dry mass of the yolk-free body and residual yolk of hatchlings were temperature dependent, such that higher temperatures produced chicks of lesser yolk-free body mass and greater residual yolk mass than chicks incubated at lower temperatures. However the overall size (linear dimensions) and lipid, protein and ash content of chicks were independent of temperature.

Developmental windows and origins of the chemical cues mediating hatching responses to injured conspecific eggs in the common frog (Rana temporaria)

In amphibians, embryonic exposure to chemical cues resulting from a predation event on conspecific eggs can influence hatching traits. However, there is no information on the precise origin of the active substances, or on the critical period of embryonic development mediating such a process. In this context, common frog ( Rana temporaria L., 1758) eggs were exposed at Gosner stage 2, 16, or 20 to chemical cues simulating predation on whole eggs, jelly envelopes, or embryos. Embryonic movement rate, hatching time, and developmental stage at hatching appeared unaffected by the nature of the treatment. In contrast, the embryonic treatments strongly affected the morphology of hatchlings, with the groups exposed to crushed whole eggs and jelly envelopes showing longer (exposures at stages 16 and 20) and deeper (exposure at stage 20) tails than their unexposed counterparts. In addition, exposure at stage 20 to crushed embryos also produced hatchlings with longer tails than the controls. Thus, morphological plasticity at hatching can result from a relatively short period of embryonic exposure to conspecific chemical cues. This critical period occurs at the completion of neurulation (stage 16), with the most marked effects resulting from an exposure at the last stage of embryonic development (stage 20).

Phenotypic effects of thermal mean and fluctuations on embryonic development and hatchling traits in a lacertid lizard, Takydromus septentrionalis

How fluctuating temperatures influence reptilian embryos and hatchlings has attracted increasing scientific attention, but is poorly known. We conducted an incubation experiment with a factorial design of two mean temperatures (24 vs. 28 degrees C) and three diel thermal fluctuations (0, +/-3, +/-6 degrees C) to determine the effects of diel thermal fluctuations and mean temperature on incubation duration and hatchling phenotypes. Both diel thermal fluctuations and mean temperature significantly affected incubation duration, but not hatching success. Incubation duration increased with increasing temperature fluctuations at a mean temperature of 24 degrees C, but not at a mean temperature of 28 degrees C. The significant interaction between diel thermal fluctuations and mean temperature on hatchling morphology indicated that the effect of thermal fluctuations depended on the mean temperature. Hatchling mass differed significantly between 24+/-6 and 28+/-6 degrees C, but not between the two constant temperatures or the temperatures with +/-3 degrees C fluctuations. At a mean temperature of 24 degrees C, the effect of thermal fluctuations on hatchling size was marginally significant, with relatively large hatchlings at the constant temperature; at a mean temperature of 28 degrees C, thermal fluctuations had no impact on hatchling size. The locomotor performances were significantly affected by mean temperature rather than diel thermal fluctuations. Therefore, diel thermal fluctuations around a given mean temperature do not affect hatchling phenotypes in a relatively large magnitude, but the influence of diel thermal fluctuations may differ with changing mean temperatures.

Consequences of maternal yolk testosterone for offspring development and survival: experimental test in a lizard

SummaryHormone‐mediated maternal effects and developmental plasticity are important sources of phenotypic variation, with potential consequences for trait evolution. Yet our understanding of the importance of maternal hormones for offspring fitness in natural populations is very limited, particularly in non‐avian species.We experimentally elevated yolk testosterone by injection of a physiological dose into eggs of the lizardCtenophorus fordiStorr, to investigate its roles in offspring development, growth and survival.Yolk testosterone did not influence incubation period, basic hatchling morphology or survival under natural conditions. However, there was evidence for increased growth in hatchlings from testosterone‐treated eggs, suggesting that maternal hormones have potential fitness consequences in natural populations.The positive effect of prenatal testosterone exposure on postnatal growth could represent a taxonomically widespread developmental mechanism that has evolved into an adaptive maternal effect in some taxa, but remains deleterious or selectively neutral in others.A broader taxonomic perspective should increase our understanding of the role of physiological constraints in the evolution of endocrine maternal effects.

Embryonic experience to predation risk affects tadpoles of the common frog (Rana temporaria)

Amphibians are known to exhibit phenotypic plasticity in response to variations in predation pressure. Data also indicate that developmental changes can be induced by embryonic exposures to predator non-contact cues. However, the possible consequences of such exposures on larval behavioural activity and sensitivity to chemical cues from predators have remained unexplored. These laboratory experiments examine the effects of predation cues experienced during embryonic development on some morphological and behavioural traits in hatchlings and tadpoles of the common frog (Rana temporaria). Eggs were raised until hatching in the nonlethal presence of either a sympatric predator (larval spotted salamander, Salamandra salamandra), or an allopatric predator (juvenile Turkish crayfish, Astacus leptodactylus), or crushed conspecific tadpoles. Predators were kept either starved, or fed with R. temporaria tadpoles. Embryonic treatments had significant consequences on weight and total length of hatchlings, as well as on the general activity of tadpoles. Olfactometric tests showed that the behavioural responses of tadpoles to chemical cues from the two predators tested were not significantly affected by embryonic treatments. In contrast, embryonic experience showed a significant influence on the behavioural response of tadpoles to chemical cues from crushed conspecifics. These results indicate that the morphology of hatchlings depends on the species and diet of the predators present during embryonic development and demonstrate for the first time that the subsequent activity and chemically mediated antipredator behaviour of tadpoles can be influenced by embryonic experience of the predation risk.

THE ADAPTIVE SIGNIFICANCE OF TEMPERATURE-DEPENDENT SEX DETERMINATION: EXPERIMENTAL TESTS WITH A SHORT-LIVED LIZARD

Why is the sex of many reptiles determined by the temperatures that these animals experience during embryogenesis, rather than by their genes? The Charnov-Bull model suggests that temperature-dependent sex determination (TSD) can enhance maternal fitness relative to genotypic sex determination (GSD) if offspring traits affect fitness differently for sons versus daughters and nest temperatures either determine or predict those offspring traits. Although potential pathways for such effects have attracted much speculation, empirical tests largely have been precluded by logistical constraints (i.e., long life spans and late maturation of most TSD reptiles). We experimentally tested four differential fitness models within the Charnov-Bull framework, using a short-lived, early-maturing Australian lizard (Amphibolurus muricatus) with TSD. Eggs from wild-caught females were incubated at a range of thermal regimes, and the resultant hatchlings raised in large outdoor enclosures. We applied an aromatase inhibitor to half the eggs to override thermal effects on sex determination, thus decoupling sex and incubation temperature. Based on relationships between incubation temperatures, hatching dates, morphology, growth, and survival of hatchlings in their first season, we were able to reject three of the four differential fitness models. First, matching offspring sex to egg size was not plausible because the relationship between egg (offspring) size and fitness was similar in the two sexes. Second, sex differences in optimal incubation temperatures were not evident, because (1) although incubation temperature influenced offspring phenotypes and growth, it did so in similar ways in sons versus daughters, and (2) the relationship between phenotypic traits and fitness was similar in the two sexes, at least during preadult life. We were unable to reject a fourth model, in which TSD enhances offspring fitness by generating seasonal shifts in offspring sex ratio: that is, TSD allows overproduction of daughters (the sex likely to benefit most from early hatching) early in the nesting season. In keeping with this model, hatching early in the season massively enhanced body size at the beginning of the first winter, albeit with a significant decline in probability of survival. Thus, the timing of hatching is likely to influence reproductive success in this short-lived, early maturing species; and this effect may well differ between the sexes.

THE ADAPTIVE SIGNIFICANCE OF TEMPERATURE-DEPENDENT SEX DETERMINATION: EXPERIMENTAL TESTS WITH A SHORT-LIVED LIZARD

Why is the sex of many reptiles determined by the temperatures that these animals experience during embryogenesis, rather than by their genes? The Charnov-Bull model suggests that temperature-dependent sex determination (TSD) can enhance maternal fitness relative to genotypic sex determination (GSD) if offspring traits affect fitness differently for sons versus daughters and nest temperatures either determine or predict those offspring traits. Although potential pathways for such effects have attracted much speculation, empirical tests largely have been precluded by logistical constraints (i.e., long life spans and late maturation of most TSD reptiles). We experimentally tested four differential fitness models within the Charnov-Bull framework, using a short-lived, early-maturing Australian lizard (Amphibolurus muricatus) with TSD. Eggs from wild-caught females were incubated at a range of thermal regimes, and the resultant hatchlings raised in large outdoor enclosures. We applied an aromatase inhibitor to half the eggs to override thermal effects on sex determination, thus decoupling sex and incubation temperature. Based on relationships between incubation temperatures, hatching dates, morphology, growth, and survival of hatchlings in their first season, we were able to reject three of the four differential fitness models. First, matching offspring sex to egg size was not plausible because the relationship between egg (offspring) size and fitness was similar in the two sexes. Second, sex differences in optimal incubation temperatures were not evident, because (1) although incubation temperature influenced offspring phenotypes and growth, it did so in similar ways in sons versus daughters, and (2) the relationship between phenotypic traits and fitness was similar in the two sexes, at least during preadult life. We were unable to reject a fourth model, in which TSD enhances offspring fitness by generating seasonal shifts in offspring sex ratio: that is, TSD allows overproduction of daughters (the sex likely to benefit most from early hatching) early in the nesting season. In keeping with this model, hatching early in the season massively enhanced body size at the beginning of the first winter, albeit with a significant decline in probability of survival. Thus, the timing of hatching is likely to influence reproductive success in this short-lived, early maturing species; and this effect may well differ between the sexes.

Maternal effects of egg size on emuDromaius novaehollandiaeegg composition and hatchling phenotype

Parental investment in eggs and, consequently, in offspring can profoundly influence the phenotype, survival and ultimately evolutionary fitness of an organism. Avian eggs are excellent model systems to examine maternal allocation of energy translated through egg size variation. We used the natural range in emu Dromaius novaehollandiae egg size, from 400 g to >700 g, to examine the influence of maternal investment in eggs on the morphology and physiology of hatchlings. Female emus provisioned larger eggs with a greater absolute amount of energy, nutrients and water in the yolk and albumen. Variation in maternal investment was reflected in differences in hatchling size, which increased isometrically with egg size. Egg size also influenced the physiology of developing emu embryos, such that late-term embryonic metabolic rate was positively correlated with egg size and embryos developing in larger eggs consumed more yolk during development. Large eggs produced hatchlings that were both heavier (yolk-free wet and dry mass) and structurally larger (tibiotarsus and culmen lengths) than hatchlings emerging from smaller eggs. As with many other precocial birds, larger hatchlings also contained more water, which was reflected in a greater blood volume. However, blood osmolality, hemoglobin content and hematocrit did not vary with hatchling mass. Emu maternal investment in offspring, measured by egg size and composition, is significantly correlated with the morphology and physiology of hatchlings and, in turn, may influence the success of these organisms during the first days of the juvenile stage.

Predator-induced plasticity in early life history and morphology in two anuran amphibians.

Predation pressure during early life stages is often high, but few studies have examined antipredator responses at these stages. We studied the effects of an egg predator (leech, Haemopis sanguisuga) and two tadpole predators (dragonfly larvae, Aeshna spp.; and threespine stickleback, Gasterosteus aculeatus) on the timing of hatching and morphology of hatchlings and young tadpoles in two anuran amphibians [Rana arvalis (RA) and R. temporaria (RT)] in a factorial laboratory experiment. We also compared the responses of two geographically separated RA populations on the Baltic island of Gotland and in Uppland on the Swedish mainland. We found inconsistent evidence for the predictions that the presence of an egg predator induces earlier hatching, and the presence of a larval predator delays hatching. RT hatched later in the presence of stickleback than in the control treatment, but RA hatched earlier, less developed and at smaller size in the leech, dragonfly, and stickleback treatments. There was no indication of predator-induced morphology in hatchlings of either of the species. However, young RA tadpoles had shorter tails and deeper bodies in the stickleback treatment and RT had shorter tails in the leech, dragonfly and stickleback treatments. Irrespective of treatment, RA from Gotland hatched with relatively longer bodies than Uppland individuals and had relatively deeper and short tails as young tadpoles. Our results highlight the diversity of induced responses to predators in anuran amphibians: predator presence affects the timing of hatching and morphology of young tadpoles, but these responses vary depending on the species and predator considered.

Influence of incubation temperature on hatching success, energy expenditure for embryonic development, and size and morphology of hatchlings in the oriental garden lizard, Calotes versicolor (Agamidae).

We incubated eggs of Calotes versicolor at four constant temperatures ranging from 24 degrees C to 33 degrees C to assess the effects of incubation temperature on hatching success, embryonic use of energy, and hatchling phenotypes that are likely to affect fitness. All viable eggs increased in mass throughout incubation due to absorption of water, and mass gain during incubation was dependent on initial egg mass and incubation temperature. The average duration of incubation at 24 degrees C, 27 degrees C, 30 degrees C, and 33 degrees C was 82.1 days, 60.5 days, 51.4 days, and 50.3 days, respectively. Incubation temperature affected hatching success, energy expenditure for embryonic development, and several hatchling traits examined, but it did not affect the sex ratio of hatchlings. Hatching success was lowest (3.4%) at 33 degrees C, but a higher incidence of deformed embryos was recorded from eggs incubated at this temperature compared to eggs incubated at lower temperatures. Most of the deformed embryos died at the last stage of incubation. Energy expenditure for embryonic development was, however, higher in eggs incubated at 33 degrees C than those similarly incubated at lower temperatures. A prolonged exposure of eggs of C. versicolor at 33 degrees C appears to have an adverse and presumably lethal effect on embryonic development. Hatching success at 24 degrees C was also low (43.3%), but hatchlings incubated at 24 degrees C did not differ in any of the examined traits from those incubated at two intermediate temperatures (27 degrees C and 30 degrees C). Hatchlings incubated at 33 degrees C were smaller (snout-vent length, SVL) than those incubated at lower incubation temperatures and had larger mass residuals (from the regression on SVL) as well as shorter head length, hindlimb length, tympanum diameter, and eye diameter relative to SVL. Hatchlings from 33 degrees C had significantly lower scores on the first axis of a principal component analysis representing mainly SVL-free head size (length and width) and fore- and hindlimb lengths, but they had significantly higher scores on the second axis mainly representing SVL-free wet body mass. Variation in the level of fluctuating asymmetry in eye diameter associated with incubation temperatures was quite high, and it was clearly consistent with the prediction that environmental stress associated with the highest incubation temperatures might produce the highest level of asymmetry. Newly emerged hatchlings exhibited sexual dimorphism in head width, with male hatchlings having larger head width than females.

Incubation regime affects juvenile morphology and hatching success, but not sex, of the oviparous lizard Oligosoma suteri (Lacertilia: Scincidae)

We studied the effects of different artificial incubation regimes on the hatching success, morphology, and sex of hatchlings of New Zealand's only endemic egg‐laying skink, Oligosoma suteri (Boulenger, 1906). Eggs were randomly distributed among three constant incubation temperatures (18, 22, and 26°C) and two water potentials (‐120 and ‐270 kPa). Hatching success and hatchling survival were greatest at 22 and 26°C. Hatchlings from 18°C incubation had low survival, morphological abnormalities of the limbs, and atypical colouration. Water potential did not influence hatchling survival, morphology, or sex. Equal sex ratios were found at all incubation regimes indicating that sex determination in O. suteri is genetic, not temperature‐dependent.

Morphological Variation in Hatchling American Alligators (Alligator mississippiensis) from Three Florida Lakes

Morphological variation of 508 hatchling alligators from three lakes in north central Florida (Lakes Woodruff, Apopka, and Orange) was analyzed using multivariate statistics. Morphological variation was found among clutches as well as among lakes. Principal components analysis was used to determine the proportion of the variation attributable to shape as opposed to size. Shape accounted for 42% and 36% of the variation among individuals and clutches, respectively. Linear discriminant analysis with cross-vali- dation was performed to determine whether the clutch from which an individual came or the lake from which a clutch came from could be predicted. Success of predicting clutch membership varied from 67% for Lake Apopka to 74% for Orange Lake. The lake from which a clutch was obtained could be predicted with a success rate of 49%. The optimal subset of measurement variables, obtained from stepwise discrim- inant analysis, was used to illustrate the morphological variation among clutches and lakes in a scatterplot of the first two canonical variables. Assuming factors such as genetics, nutrition, age, size, and stress affect hatchling morphology, one would suspect hatchlings from the same clutch to be more similar than hatch- lings from different clutches. Likewise, we suggest that a lake effect could be the result of intrapopulational similarity of environmental factors, such as food and resource availability, nutrient levels, contaminant levels, and parental lineage (genetics). We hypothesize that demographic and environmental influence on the ma- ternal contribution to the embryonic environment, rather than genetic influence, is responsible for the ob- served pattern of morphological variation.

Predation-induced effects on hatchling morphology in the common frog (Rana temporaria)

As mortality due to predation is often high at early independent life stages in many animals, it can be expected that predation-induced modifications of early life history and morphology will be common when predation risk varies spatially or temporally. However, studies of such effects are still rare. Predation-induced changes in life history and morphology have often been described in amphibian larvae, but the focus has been on older larvae and little is known about responses of hatchlings or very young larvae. We examined whether predator presence influenced timing of hatching and hatchling morphology in the common frog, Rana temporaria. In a paired design, eggs from 10 clutches were allowed to develop from fertilization to hatching, with or without the nonlethal presence of a larva of the large diving beetle Dytiscus marginalis. We found no evidence that predator presence affected timing of hatching. However, hatchlings raised in the presence of the predator had relatively shorter bodies and deeper tail fins than their full-sibs raised in the absence of the predator, indicating that predation induces morphological responses in R. temporaria hatchlings. This is one of the very few studies showing that predators, or chemical cues released during a predation event, can induce a plastic morphological changes in vertebrates at very early life stages.

Predation-induced effects on hatchling morphology in the common frog (<i>Rana temporaria</i>)

As mortality due to predation is often high at early independent life stages in many animals, it can be expected that predation-induced modifications of early life history and morphology will be common when predation risk varies spatially or temporally. However, studies of such effects are still rare. Predation-induced changes in life history and morphology have often been described in amphibian larvae, but the focus has been on older larvae and little is known about responses of hatchlings or very young larvae. We examined whether predator presence influenced timing of hatching and hatchling morphology in the common frog, Rana temporaria. In a paired design, eggs from 10 clutches were allowed to develop from fertilization to hatching, with or without the nonlethal presence of a larva of the large diving beetle Dytiscus marginalis. We found no evidence that predator presence affected timing of hatching. However, hatchlings raised in the presence of the predator had relatively shorter bodies and deeper tai...

How incubation temperature influences the physiology and growth of embryonic lizards.

Eggs of two small Australian lizards, Lampropholis guichenoti and Bassiana duperreyi, were incubated to hatching at 25 degrees C and 30 degrees C. Incubation periods were significantly longer at 25 degrees C in both species, and temperature had a greater effect on the incubation period of B. duperreyi (41.0 days at 25 degrees C; 23.1 days at 30 degrees C) than L. guichenoti (40.1 days at 25 degrees C; 27.7 days at 30 degrees C). Patterns of oxygen consumption were similar in both species at both temperatures, being sigmoidal in shape with a fall in the rate of oxygen consumption just prior to hatching. The higher incubation temperature resulted in higher peak and higher prehatch rates of oxygen consumption in both species. Total amount of oxygen consumed during incubation was independent of temperature in B. duperreyi, in which approximately 50 ml oxygen was consumed at both temperatures, but eggs of L. guichenoti incubated at 30 degrees C consumed significantly more (32.6 ml) than eggs incubated at 25 degrees C (28.5 ml). Hatchling mass was unaffected by either incubation temperature or the amount of water absorbed by eggs during incubation in both species. The energetic production cost of hatchling B. duperreyi (3.52 kJ x g(-1)) was independent of incubation temperature, whereas in L. guichenoti the production cost was greater at 30 degrees C (4.00 kJ x g(-1)) than at 25 degrees C (3.47 kJ g(-1)). Snout-vent lengths and mass of hatchlings were unaffected by incubation temperature in both species, but hatchling B. duperreyi incubated at 30 degrees C had longer tails (29.3 mm) than those from eggs incubated at 25 degrees C (26.2 mm). These results indicate that incubation temperature can affect the quality of hatchling lizards in terms of embryonic energy consumption and hatchling morphology.

Incubation of eggs of the Australian broad-shelled turtle, Chelodina expansa (Testudinata : Chelidae), at different temperatures: effects on pattern of oxygen consumption and hatchling morphology

Incubation temperature influences embryonic development and the morphology of resultant hatchlings in many species of turtle but few studies have addressed its effect on oxygen consumption and total embryonic energy expenditure. Eggs of the Australian broad-shelled river turtle, Chelodina expansa, were incubated at constant temperatures of 24˚C and 28˚C to determine the effect of temperature on oxygen consumption, embryonic energy expenditure and hatchling morphology. All embryos at both incubation temperatures experienced a period of developmental diapause immediately after oviposition. Once this initial diapause was broken, embryos underwent a further period of developmental arrest when the embryo was still very small and had minimal oxygen consumption (<20 µL h–1). However, once rapid embryonic growth started, development appeared to be continuous. Rate of increase and peak rate of oxygen consumption were temperature dependent, both being highest at 28˚C. Net production efficiency (total oxygen consumed during incubation divided by yolk-free hatchling mass) was 120 mL O2 g–1 at 24˚C and 111 mL O2g–1 at 28˚C. Hatchling mass and yolk-free hatchling mass were independent of incubation temperature, but hatchlings from 28˚C had larger residual yolks and smaller head widths than hatchlings from 24˚C.