Hatchling Size Research Articles

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.

The role of energetic reserves during embryonic development of an annual killifish.

Females can significantly improve their fitness by utilizing a range of maternal effects. Embryos of annual killifish survive the dry season in ephemeral pools encased in dry substrate for several months. Here, we experimentally test the association between energetic provisioning and maternally controlled duration of embryonic development in the African annual killifish Nothobranchius furzeri (Cyprinodontiformes). We found that embryonic energetic reserves do not limit duration of development. However, differences in energetic reserves affect the size at which embryos hatched, with larger yolk size resulting in larger hatchling size. These findings suggest uncoupling of the two traits examined (i.e., embryonic energetic reserves and development duration) and emphasize the strong buffering role of diapause in the energetic balance of embryonic development in the annual killifish. Developmental Dynamics 246:838-847, 2017. © 2017 Wiley Periodicals, Inc.

Effects of environmental warming during early life history on libellulid odonates

Climate warming affects ectotherms globally, yet we know little regarding the variability in species’ responses to warming, particularly in early life stages. Additionally, intraspecific variation in response to warming is understudied but may determine species’ resilience to warming. To assess how temperature affects egg development rate in co-occurring dragonfly species, we manipulated temperature (range: 22–31 °C) and measured time to hatching. Warming decreased egg development time across all species, indicating that while climate warming will advance hatching phenology, maintained synchrony in hatching order will likely not affect species interactions. Our second experiment examined early life-history responses to warming in the dot-tailed whiteface (Leucorrhinia intacta (Hagen, 1861)) dragonfly. We measured time to hatching, hatchling size, growth rate, and survival at four temperatures (23–30 °C), including a treatment with increased thermal variation. Warming resulted in smaller hatchlings with increased growth and mortality rates, whereas higher thermal variation did not have effects different from those of warming alone. We observed significant intraspecific variation in the responses to warming in both egg development time and hatchling size and this variation was correlated with date of oviposition. High levels of intraspecific variation may be important in buffering populations from the effects of climate warming.

Social environment during egg laying: Changes in plasma hormones with no consequences for yolk hormones or fecundity in female Japanese quail, Coturnix japonica.

The social environment can have profound effects on an individual’s physiology and behaviour and on the transfer of resources to the next generation, with potential consequences for fecundity and reproduction. However, few studies investigate all of these aspects at once. The present study housed female Japanese quail (Coturnix japonica) in pairs or groups to examine the effects on hormone concentrations in plasma and yolk and on reproductive performance. Circulating levels of androgens (testosterone and 5-α-dihydrotestosterone) and corticosterone were measured in baseline samples and after standardised challenges to assess the responsiveness of the females’ endocrine axes. Effects of the social environment on female fecundity were analysed by measuring egg production, egg mass, fertilization rates, and number of hatched offspring. Counter to expectation, females housed in pairs had higher plasma androgen concentrations and slightly higher corticosterone concentrations than females housed in groups, although the latter was not statistically significant. Pair vs. group housing did not affect the females’ hormonal response to standardised challenges or yolk testosterone levels. In contrast to previous studies, the females’ androgen response to a gonadotropin-releasing hormone challenge was not related to yolk testosterone levels. Non-significant trends emerged for pair-housed females to have higher egg-laying rates and higher fertility, but no differences arose in egg weight or in the number, weight or size of hatchlings. We propose that our unexpected findings are due to differences in the adult sex ratio in our social treatments. In pairs, the male may stimulate female circulating hormone levels more strongly than in groups where effects are diluted due to the presence of several females. Future studies should vary both group size and sex composition to disentangle the significance of sexual, competitive and affiliative social interactions for circulating and yolk hormone levels, and their consequences for subsequent generations.

Eggshell structure in Caiman latirostris eggs improves embryo survival during nest inundation.

Egg inundation often results in poor hatching success in crocodylians. However, how tolerant eggs are to submergence, and/or how eggshell ultrastructure may affect embryo survival when inundated, are not well understood. In this study, our objective was to determine if embryo survival in Caiman latirostris is affected by eggshell surface roughness, when eggs are submerged under water. Tolerance to inundation was tested early (day 30) versus late (day 60) in development, using eight clutches (four per time treatments), subdivided into four groups: (N = 9 per clutch per treatment; 9 × 4 = 36 eggs per group). 'Rough' eggshell represented the natural, unmodified eggshell surface structure. 'Smooth' eggshell surface structure was created by mechanically sanding the natural rough surface to remove surface columnar elements and secondary layer features, e.g. irregularities that result in 'roughness'. When inundated by submerging eggs under water for 10 h at day 30, 'smooth' eggshell structure resulted in more than twice as many dead embryos (16 versus 6, smooth versus rough; N = 36), and fewer than half as many healthy embryos (6 versus 13, smooth versus rough, respectively; N = 36). By contrast, at day 60, inundation resulted in very low hatching success, regardless of eggshell surface structure. Only two hatchlings survived the inundation, notably in the untreated group with intact, rough eggshells. Inundation produced a high rate of malformations (58% at day 30), but did not affect hatchling size. Our results indicate that eggshell roughness enhances embryo survival when eggs are inundated early in development, but not late in development. Apparently, the natural surface 'roughness' entraps air bubbles at the eggshell surface during inundation, thereby facilitating gas exchange through the eggshell even when the egg is submerged under water.

Life history traits determine the differential vulnerability of native and invasive apple snails (Pomacea spp.) to a shared juvenile-stage predator

The vulnerability of gastropods to their predators varies with life history traits such as morphology, body size, behavior, and growth rates as well as predator size. A recent study suggested that the invasive apple snail, Pomacea maculata, was considerably more vulnerable to crayfish predators than the native Florida apple snail, P. paludosa. The difference was hypothesized to be caused by the relatively small hatchling size of P. maculata. To test this hypothesis, we conducted a series of feeding assays designed to quantify maximum feeding rates and selective foraging of crayfish on apple snails. The rate at which crayfish killed individual P. maculata (i.e., kill rates) decreased with snail size, and kill rates on both species increased with crayfish size. Kill rates on juvenile P. maculata were higher than kill rates on size-matched hatchling P. paludosa, and crayfish fed selectively on P. maculata when offered mixed groups of size-matched snails. Further analyses revealed that hatchling P. paludosa possess shells 1.8× heavier than size-matched P. maculata suggesting differences in vulnerability to crayfish were consistent with interspecific differences in shell defenses. Differences in hatchling size and defensive traits in combination make crayfish kill rates on hatchling P. maculata approximately 15.4× faster than on hatchling P. paludosa, but the relative contribution of hatchling size to differences in apple snail vulnerability was >3× greater than the contribution of defensive traits.

The effects of incubation temperature on locomotor performance, growth and survival in hatchling velvet geckos

AbstractThe thermal environment that lizard eggs experience during incubation can affect the size, shape and performance of hatchlings. Summer heatwaves are predicted to increase in frequency and duration in the future, and could produce higher temperatures inside lizard nests. Increase in nest temperatures may influence offspring sex, body size, growth and locomotor performance, which in turn can affect fitness. We investigated whether incubation temperatures influenced the locomotor performance of hatchlings of the velvet gecko (Amalosia lesueurii), a nocturnal gecko that lays eggs in communal nests inside rock crevices. We incubated eggs at two fluctuating temperature regimes that mimicked current nest temperatures (mean = 23.2°C, range 10–33°C, ‘current’) and predicted future nest temperatures (mean = 27.0°C, 14–37°C, ‘future’). We measured the locomotor performance of hatchlings at four temperatures (20, 25, 30 and 35°C), and released them at two field sites (Nowra and Dharawal National Park, ‘DNP’) to estimate their growth and survival over 10 months. Hot‐incubated hatchlings were smaller, and ran more slowly than current‐incubated hatchlings at all four test temperatures. Incubation temperature did not affect the growth rates of lizards from Nowra, but at DNP, hot‐incubated lizards grew more slowly than current‐incubated lizards. Survival analyses revealed that future‐incubated hatchlings had lower survival than current‐incubation hatchlings over 10 months of life, but selection on hatchling traits differed between study sites. For hatchlings from DNP, there was evidence for directional selection on body mass, but little support for selection on SVL or speed. At Nowra, there was equivalent evidence for selection on mass, SVL and speed. These results demonstrate that incubation induced differences in morphology and locomotor performance can influence the survival of hatchlings. In the absence of maternal plasticity in nesting behavior, future increase in nest temperatures, by altering offspring morphology, performance and survival, have the potential to influence the viability of gecko populations.

The ecology of the tropical salamander, Bolitoglossa subpalmata, in Costa Rica.

The ecology of the tropical salamander, Bolitoglossa subpalmata, in Costa Rica.

Diet history effects on Zebra Finch incubation performance: Nest attendance, temperature regulation, and clutch success

ABSTRACT Incubation is a costly phase of avian reproduction, as parents must invest in heat transfer to eggs and nest construction in order to maintain egg temperature within suitable thermal limits; however, costs may differ based on an individual's ability to invest in reproduction. To investigate how environmental conditions, specifically food quality experienced during development and reproduction, influence tactics of resource allocation and costs during incubation, captive Zebra Finches (Taeniopygia guttata castanotis) were raised on either a high- or low-quality diet, paired with a bird of the same diet history, and randomly assigned to breed under the same diet they had been reared on or on the opposite diet. Data were collected on nest attendance, nest quality, nest temperature, and clutch performance (clutch size, egg weight, and number of hatchlings). Greater nest attendance and higher nest-quality scores predicted low temperature fluctuation. Three structural nest components also contributed t...

Multiple Paternity Benefits Female Marbled Salamanders by Increasing Survival of Progeny to Metamorphosis

AbstractMultiple paternity occurs in most species and animal groups that have been studied. Because mating involves fitness costs to individual females, theory predicts that polyandrous females gain greater fitness benefits than costs, allowing the behavior to be maintained. Genetic, rather than material, benefits often occur in species where males provide females with little more than sperm and seminal fluid. We compared fitness correlates of single‐ and double‐sire clutches from female marbled salamanders (Ambystoma opacum) at the egg, hatchling, and metamorph stages of offspring development. Because clutches were collected from experimental breeding groups, strict paternity exclusion of offspring using microsatellite data allowed us to categorize each clutch as having either one or two fathers. Early offspring viability and size of hatchlings were not different between single‐ and multiple‐paternity clutches. Larvae from the two clutch types were allowed to develop together in field enclosures until metamorphosis. Although there was no difference in size at metamorphosis, survival to metamorphosis was significantly higher in multiple‐paternity clutches (44% vs. 40%) suggesting a benefit for females. The results were consistent with genetic benefits, although maternal effects could not be ruled out. The data did not support predictions of the genetic bet‐hedging and good sperm hypotheses for genetic benefits of polyandry.

The effects of light exposure during incubation on embryonic development and hatchling traits in lizards.

Light is an environmental factor that is known to profoundly affect embryonic development in some oviparous vertebrates, but such effects are unstudied in reptiles. We investigated the light sensitivity of lizard embryos by examining the thickness and light transmittance of eggshells as well as the effect of light on embryonic development and hatchling traits in four lizard species, the Chinese skink (Plestiodon chinensis), the northern grass lizard (Takydromus septentrionalis), the oriental leaf-toed gecko (Hemidactylus bowringii) and the Japanese gecko (Gekko japonicus). The eggshells were thinner and thus had higher light transmittance in Chinese skink than the other three species. Light exposure during incubation significantly accelerated the embryonic development in all species, with higher light intensity resulting in faster embryonic development. Interestingly, light stimulation negatively influenced hatchling size and survival in skinks, but had no effect in lacertids and geckos. This interspecific discrepancy not only relates to the differences in thickness and light transmittance of eggshells, but might also reflect the differences in the reproductive habits of these species. Given the diversity of light conditions that reptile embryos face during development, studies on the response of reptile embryos to light may offer a unique opportunity to understand the mechanisms of embryonic light sensitivity in animals.

Reproductive output and morphometrics of green turtle, Chelonia mydas nesting at the Kosgoda rookery in Sri Lanka

Reproductive output provides data fundamental to the conservation and management of sea turtles. Five years of data on the reproductive output of female green turtles was collected from Kosgoda beach, the second largest sea turtle rookery in Sri Lanka. Egg size, clutch size, clutch frequency, female size, hatchling size, hatching success, nest depth, and incubation duration were recorded. A total of 1,492 nests comprising 166,358 eggs were laid by 575 nesting females during the study period. Larger females had a higher reproductive output, laying larger eggs, bigger clutches, and producing a greater number of eggs in total for a season. There was no relationship between clutch size and egg size, and the hatchling size did not depend on the egg size or the female size. The mean hatching success was 77.3% and the mean incubation duration was 50.6 days. Clutch size, egg size, female body size, and nest depth had no effect on hatching success of the green turtles nests laid at Kosgoda rookery. Even though the size of the nesting turtles and clutch size were similar to other green turtle populations, the reproductive output and clutch frequency of green turtle females nesting at Kosgoda rookery were low compared to the population at Rekawa beach in southern Sri Lanka and other green turtle populations worldwide. The shorter stretch of beach (1 km) used to collect data may be a reason for this difference, precluding observation of re-nesting efforts by the female turtles.

Early Mode of Life and Hatchling Size in Cephalopod Molluscs: Influence on the Species Distributional Ranges.

Cephalopods (nautiluses, cuttlefishes, squids and octopuses) exhibit direct development and display two major developmental modes: planktonic and benthic. Planktonic hatchlings are small and go through some degree of morphological changes during the planktonic phase, which can last from days to months, with ocean currents enhancing their dispersal capacity. Benthic hatchlings are usually large, miniature-like adults and have comparatively reduced dispersal potential. We examined the relationship between early developmental mode, hatchling size and species latitudinal distribution range of 110 species hatched in the laboratory, which represent 13% of the total number of live cephalopod species described to date. Results showed that species with planktonic hatchlings reach broader distributional ranges in comparison with species with benthic hatchlings. In addition, squids and octopods follow an inverse relationship between hatchling size and species latitudinal distribution. In both groups, species with smaller hatchlings have broader latitudinal distribution ranges. Thus, squid and octopod species with larger hatchlings have latitudinal distributions of comparatively minor extension. This pattern also emerges when all species are grouped by genus (n = 41), but was not detected for cuttlefishes, a group composed mainly of species with large and benthic hatchlings. However, when hatchling size was compared to adult size, it was observed that the smaller the hatchlings, the broader the latitudinal distributional range of the species for cuttlefishes, squids and octopuses. This was also valid for all cephalopod species with benthic hatchlings pooled together. Hatchling size and associated developmental mode and dispersal potential seem to be main influential factors in determining the distributional range of cephalopods.

The effects of nest incubation temperature on embryos and hatchlings of the loggerhead sea turtle: Implications of sex difference for survival rates during early life stages

In sea turtles, higher hatch and emergence successes, larger body size of hatchlings, and superior terrestrial and swimming locomotor performances are important to maximize survival rates. Here, the hatch and emergence successes, embryonic mortality rates, hatchling morphology, and terrestrial and swimming locomotor performances of the loggerhead sea turtle (Caretta caretta) from male and female producing nests were investigated. Mortality rates during the early embryonic stage in the male producing nests were significantly lower than those in the female producing nests. The hatchlings from male producing nests showed higher terrestrial locomotor performances than those from female producing nests. Furthermore, while the other factors did not show differences between the two nesting groups, the high incubation temperatures significantly affected the mortality rate of embryos and the swimming performance of hatchlings. The present study indicates that male hatchlings are likely to have higher survival rates than female hatchlings during the critical terrestrial period. In addition, the present study suggests that as global warming proceeds, female-fate embryos and/or female hatchlings are likely to face lower survival rates than males, owing to high mortality rate of embryos and low swimming performance of hatchlings.

High stock density impairs growth, female condition and fecundity, but not quality of early reproductive stages in vendace (Coregonus albula)

In fisheries science, stock density is one of the fundamental factors that affect growth and condition. However, reproductive traits like fecundity and also the size and quality of offspring (via maternal effects) can be modified by stock density. In the short-living freshwater fish species vendace (Coregonus albula), the impact of stock density via maternal condition on quantity and quality of eggs and larvae was often proposed as a driver of population fluctuations, but such mechanisms have only rarely been evaluated. We systematically analysed growth, female condition and reproductive traits (fecundity, egg size, hatching rate and size of hatchlings) of vendace in relation to stock density across three lakes over two years. Across populations of contrasting density, length at first maturity, female condition and relative fecundity strongly reflected the difference in stock density, while size of eggs and larvae and hatching success at artificial breeding were not correlated with stock density. Our results indicate that density-dependent female spawner traits do not alter reproductive success, but vendace maintain egg size and hatching rate at the expense of egg quantity even at low per-capita resource availability. Accordingly, the reproductive potential of vendace stocks is primarily driven by spawning stock biomass and relative fecundity. We conclude that besides spawning stock biomass and relative fecundity, the additional inclusion of spawner condition into stock assessment has little potential to improve vendace fisheries management.

Effects of egg temperature and moisture on phase characteristics of the hatchlings in Locusta migratoria

The effects of temperature and moisture during the egg stage on hatchling phase characteristics of Locusta migratoria were investigated. The incubation temperature of eggs laid by crowd-reared females affected embryonic development and some phase characteristics of the hatchlings. Incubation at 20 °C caused eggs to develop more slowly and to produce more black hatchlings than those incubated at 30 °C. A correlation was found between body size and cuticular melanism of hatchlings at these temperatures; however, the correlation was lower at the lower temperature. When large eggs expected to produce large and black hatchlings were exposed to dry conditions, they produced small, whitish hatchlings, typical of the solitary phase. However, unlike typical solitary individuals, these nymphs did not show extra moulting and had only 5 stadia before reaching the adult stage. These results suggested that deprivation of water from eggs may produce progeny looking like solitarious forms, but developmental traits such as numbers of nymphal stadia were unaffected.

Incubation temperature affects development order of morphological features and staging criteria in turtle embryos

AbstractEmbryonic development is strongly affected by incubation temperature in most animals, and the effects of incubation temperature continue after partition. However, relatively little is known about the effects of incubation temperature on the development of morphological features in reptiles. As a result, whether developmental rates of different traits change uniquely in response to incubation temperature remains unknown. In this study, we compared embryonic development of an Australian turtle incubated at different temperatures. We examined 43 internal and external morphological features of embryos at each week of development and compared presence and absence of each feature within and across weeks and temperature treatments, using a multivariate statistical approach. We identified morphological features that develop at different rates in turtle embryos incubated at different temperatures. Embryos incubated at 30°C hatched 3 weeks earlier, grew to hatchling size faster, and developed advanced morphological features earlier than those incubated at 26°C. Furthermore, embryonic features that appear late in development appeared progressively earlier in embryos incubated at 30°C. Embryos incubated at 26°C also retained some early embryonic features for longer periods of time during development, especially from weeks 2–4. Despite temperature effects, some traits appeared at the same week of development in embryos from both treatments, including a clearly distinguishable carapace and distinct gut villi at week 3. Variation in appearance and retention of features means that not all external features consistently appear in the same order, depending on incubation temperature. From a practical perspective, cool‐ and warm‐incubated embryos may exhibit different sets of embryological features, which may not be captured by previously published embryological staging guides.

Living at the edge: lower success of eggs and hatchlings at lower elevation may shape range limits in an alpine lizard

Studies on range limits clarify the factors involved in the extent of species occurrence and shed light on the limits to adaptation. We studied the effects of elevational variation on the thermal dependence of fitness-related traits (incubation time, hatching rate, and survivorship, size, and condition of hatchlings) to assess the role of incubation requirements in distribution range limits of the alpine endemic Iberolacerta cyreni. We captured gravid females from two core (summit) and two marginal (low-elevation edge) populations, we incubated their eggs at three temperatures (22, 26, and 30 °C), and we monitored phenotypic effects. Viability of eggs and hatchlings decreased, independently of elevation, as incubation temperature increased. Hatching success and embryo survivorship were lower for clutches from low-elevation areas than for those from mountain summits, showing that lizards face difficulties thriving at the low-elevation edge of their range. Such difficulties were partly counterbalanced by faster postnatal growth at lower elevations, leading to increased adult size and higher fecundity. High incubation temperature had detrimental effects also at low-elevation areas, and no elevational variation in the thermal dependence of hatchling traits was detected. We suggest that temperature effects on egg development and the lack of selective pressures strong enough to foster local adaptation at marginal areas, combined with extended egg retention, may contribute to shape the range limits of these alpine oviparous reptiles.

Access to multiple mates increases fecundity but does not affect per-offspring maternal investment in a marine gastropod

Females of many organisms mate more than once and with more than one male, suggesting that polyandry confers some advantage to the female or her offspring. However, variation in maternal investment in response to mate choice and mate number can confound efforts to determine if there are benefits of polyandry. Access to multiple mates could increase maternal investment in offspring via a number of different mechanisms. Few studies have determined if investment is influenced by mate choice and number, and data are particularly lacking for marine invertebrates. This study was designed to determine if maternal investment and offspring size increase with access to increasing numbers of mates in the protandrous intertidal slipper snail Crepidula cf. marginalis. Virgin female slipper limpets were exposed to one, three, or five potential mates and their fecundity, egg size, and hatchling size were measured for multiple clutches. Treatment had a significant effect on fecundity, with fecundity increasing with the number of potential mates. Treatment did not have an effect on the size of eggs or hatchlings, on the variation in egg size or hatchling size within broods, or on the frequency of oviposition. Treatment did alter the variation in average offspring size among females, but not in the way predicted by theory. The main result, that access to multiple mates does not have an effect on per offspring maternal investment, makes C. cf. marginalis an ideal candidate to study the effects of polyandry on offspring fitness without having to take into account confounding effects of variation in maternal investment.

Genotypic differences in embryonic life history traits ofFolsomia quadrioculata(Collembola: Isotomidae) across a wide geographical range

1. Life history traits play a central role in adaptation to specific environmental conditions. Egg development time, hatchling, and egg batch size in 10 populations of the soil‐dwelling collembolan speciesFolsomia quadrioculata(Tullberg, 1871) from diverse habitats across arctic and temperate regions, ranging in latitude from 43 to 81°N were studied.2. For all traits, 15 °C was used as the reference temperature. Phenotypic plasticity was studied by changing temperature to 10 and 20 °C in hatchling size, and to 20 °C in egg development time. The effect of latitude, climatic zone, and summer temperature at their sites of sampling was tested to address the hypotheses that populations from cooler areas would have (i) a faster temperature‐dependent egg development, (ii) a larger hatchling size, (iii) smaller egg batches and (iv) higher phenotypic plasticity3. The first and fourth hypothesis were not supported, whereas the second and third were partly supported when including the whole latitudinal gradient, but not within regions. Plasticity showed a complex pattern, including large differences between populations from similar macroclimates and considerable similarity between some populations from contrasting climates. Small effects of latitude and macroclimatic variables emphasised that local climate and microhabitat should be taken into account when evaluating thermal conditions as possible drivers of population‐specific differences in soil‐dwelling ectotherms.4. There was a trade‐off between egg batch and hatchling sizes. A weak correlation between the population mean egg development time and the mean hatchling size suggested that the populations are, or have been, exposed to differential selection.