Hatchling Performance Research Articles

Reproduction and hatchling performance in freshwater turtles associated with a remediated coal fly-ash spill

In 2008 an impoundment retaining wall failed at the Tennessee Valley Authority's coal burning plant in Kingston, Tennessee, releasing large quantities of coal-fly ash into the Emory River. Following extensive remediation of the spill, we captured (in 2011 and 2012) gravid turtles of multiple species in three rivers (two impacted and one reference) within the vicinity of the spill to determine whether there was evidence of the spill influencing reproduction. There was little evidence that river of origin affected reproductive output, hatching success, hatchling size, or hatchling locomotor performance. Although hatching success and hatchling righting ability of pond sliders, Trachemys scripta, was higher in our reference river than in the Emory or Clinch River, respectively, these differences could not be attributed to differences in individual element concentrations in turtle tissues and effect sizes were relatively small. For example, hatching success was reduced by 11% in the spill zone compared to the reference river, an effect that is unlikely substantial enough to influence local population dynamics in light of turtle life history. Our results suggest that residual contamination that remains in the Emory–Clinch system after its remediation poses low risk of excessive element exposure and limited adverse reproductive effects to freshwater turtles. Future monitoring could reveal whether the observed reduction in hatching success gradually attenuates with time, or whether any long-term effects of chronic exposure to low-level contamination emerge over time.

Experimental evaluation of reproductive response to climate warming in an oviparous skink

The impact of climate warming on organisms is increasingly being recognized. The experimental evaluation of phenotypically plastic responses to warming is a critical step in understanding the biological effects and adaptive capacity of organisms to future climate warming. Oviparous Scincella modesta live in deeply-shaded habitats and they require low optimal temperatures during embryonic development, which makes them suitable subjects for testing the effects of warming on reproduction. We raised adult females and incubated their eggs under different thermal conditions that mimicked potential climate warming. Female reproduction, embryonic development and hatchling traits were monitored to evaluate the reproductive response to warming. Experimental warming induced females to lay eggs earlier, but it did not affect the developmental stage of embryos at oviposition or the reproductive output. The high temperatures experienced by gravid females during warming treatments reduced the incubation period and increased embryonic mortality. The locomotor performance of hatchlings was not affected by the maternal thermal environment, but it was affected by the warming treatment during embryonic development. Our results suggest that climate warming might have a profound effect on fitness-relevant traits both at embryonic and post-embryonic stages in oviparous lizards.

The effect of incubation temperature on hatchling quality in the olive ridley turtle, Lepidochelys olivacea, from Alas Purwo National Park, East Java, Indonesia: implications for hatchery management

Nest protection through egg relocation from natural nests into protected hatcheries is a common practice used at rookeries around the world to increase hatchling recruitment into sea turtle populations. However, rarely have the impacts of this practice on hatchling recruitment and quality been assessed. This study investigated the influences of the thermal nest environment of olive ridley turtles Lepidochelys olivacea on emergence success and quality of hatchlings of hatchery nests in Alas Purwo National Park, East Java, Indonesia (2009 and 2010 nesting seasons). Nest temperatures above 34 °C for at least 3 consecutive days during incubation in the hatchery resulted in decreases in emergence success and locomotor performance of hatchlings. The use of the hatchery is recommended due to extremely high predation rate of nests left on the beach; however, altering hatchery management practice by spacing nests one meter apart and providing shade should improve hatchery outcomes now and into the future.

Factors influencing the embryonic development and hatchling size of the oceanic squid Illex coindetii following in vitro fertilization

Egg masses of oceanic squid accidently collected in the wild have been observed only from a few spawning events in aquaria, and as a consequence, the study of their embryos and hatchlings is very limited. Here, we used in vitro fertilization techniques to understand the abiotic factors that influenced egg development and hatchling performance of the ommastrephid squid Illex coindetii from the Mediterranean Sea. Egg and hatchling sizes of these ommastrephids are close to the minimum for cephalopod species, and therefore, short embryonic developmental periods were expected under a Mediterranean temperature regime. Low incubation densities and the use of antibiotics in the incubation medium resulted in relatively high survival rates to hatchling. Hatching time was inversely proportional to incubation temperature and ranged from 5 to 11days at 21°C and 13°C, respectively. The addition of oviducal jelly to the eggs immediately after fertilization, followed by another addition at the beginning of organogenesis, resulted in better chorionic expansion, with an increase in egg diameter, delayed hatching and higher hatchling weight, which suggests a better use of yolk reserves. Larger hatchlings in length and weight also tended to be produced at low temperature, probably also due to better yolk absorption. As this species spawns all year round, size differences between summer and winter hatchlings may be suspected. In vitro fertilization techniques used in the laboratory proved to be useful in shedding some light on the early life of this oceanic squid. Further research is needed to elaborate on tests to predict gamete quality and to develop methods to avoid premature hatching.

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

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

Locomotion performance of green turtle hatchlings from the Heron Island Rookery, Great Barrier Reef

Locomotion performance plays a vital role in determining hatchling green turtle Chelonia mydas survival in the first few hours after emerging from their nests as hatchlings crawl and swim the gauntlet of predators before reaching the relative safety of the open ocean. Previous laboratory based constant incubation experiments found incubation temperature to influence the size and swimming performance of hatchling green turtles. Here we examine the morphology and crawling and swimming performance of hatchling green turtles as they emerge from nests on Heron Island rookery in the southern Great Barrier Reef to test the hypothesis that nest temperature in the field can influence these attributes. We found inter-nest differences in hatchling mass and dimensions, and that hatchling mass was not correlated with nest temperature. However, hatchlings from warmer nests had smaller carapace dimensions than hatchlings from cool nests suggesting that more yolk was converted to hatchling tissue during embryonic development in cool nests. There was considerable intra- and inter-nest variation in both crawling and swimming performance of hatchlings. Hatchlings from cool nests tended to be faster crawlers than hatchlings from warm nests, but the thrust produced during swimming was not correlated with nest temperature. During the 4 h swimming trial, hatchlings swimming effort decreased significantly during the first 3 h but swimming effort remained relatively constant for the last 1 h. Individual hatchling crawling and swimming performances were not correlated with each other.

Experimental analysis of body size and shape during critical life‐history events of hatchling slider turtles, Trachemys scripta elegans

Summary A fundamental goal of examining life‐histories is to identify those traits that enable organisms to move from one stage of life to another; however, traits that are important in one stage or event may not be important in subsequent cases. For long‐lived taxa like turtles, studies of early life stages might be especially revealing because mortality is high during those times. In this study, we examined several morphological characters in hatchling turtles to assess their relationships with hatchling performance and survival. We assessed hatchling plastron shape and body size during a release–recapture field experiment and in subsequent swimming performance trials in the laboratory. Hatchling mass and plastron shape were correlated. Heavier turtles were relatively shorter and wider than lighter turtles. Hatchling mass had a significant positive correlation with both recapture rate, a proxy measure of survivorship, and with swimming speed. Plastron shape and recapture probability were not significantly correlated, but shape was a significant predictor of swimming performance. Shorter, wider turtles swam faster than longer, skinnier individuals. We hypothesize that this may be advantageous for quick‐start swimming to escape predation, a function of longer legs, or improved range of motion. These data support previous studies that demonstrated the importance of hatchling size for survival in the critical overland migration from nests to the water and also document the impact of body shape on basic life‐history traits for neonatal turtles.

Phenotypic Responses of Hatchlings to Constant Versus Fluctuating Incubation Temperatures in the Multi-banded Krait, Bungarus multicintus (Elapidae)

Most studies on egg incubation in reptiles have relied on constant temperature incubation in the laboratory rather than on simulations of thermal regimes in natural nests. The thermal effects on embryos in constant-temperature studies often do not realistically reflect what occurs in nature. Recent studies have increasingly recognized the importance of simulating natural nest temperatures rather than applying constant-temperature regimes. We incubated Bungarus multicintus eggs under three constant and one fluctuating-temperature regimes to evaluate the effects of constant versus fluctuating incubation temperatures on hatching success and hatchling phenotypes. Hatching success did not differ among the four treatments, and incubation temperature did not affect the sexual phenotype of hatchlings. Incubation length decreased as incubation temperature increased, but eggs incubated at fluctuating temperatures did not differ from eggs incubated at constant temperatures with approximately the same mean in incubation length. Of the hatchling phenotypes examined, residual yolk, fat bodies and locomotor performance were more likely affected by incubation temperature. The maximal locomotor speed was fastest in the fluctuating-temperature and 30 degrees C treatments and slowest in the 24 degrees C treatment, with the 27 degrees C treatment in between. The maximal locomotor length was longest in the fluctuating-temperature treatment and shortest in the 24 degrees C and 27 degrees C treatments, with the 30 degrees C treatment in between. Our results show that fluctuating incubation temperatures do not influence hatching success and hatchling size and morphology any differently than constant temperatures with approximately the same mean, but have a positive effect on locomotor performance of hatchlings.

Effects of sand erosion and current harvest practices on incubation of the flatback sea turtle (Natator depressus)

A suitable gaseous, hydrous and thermal nest environment is essential for the development of sea turtle embryos. The harvest of partial clutches by indigenous people and changes in nest depth from wind erosion or predation have prompted questions about the impact of clutch size and nest depth on nest success and hatchling output. We investigated the impact of reduced clutch sizes and nest depths on flatback sea turtle (Natator depressus) eggs, using a hatchery on a natural beach and clutch sizes of 10, 30 and 50 eggs, deposited at depths of 25, 35 and 50 cm. Hatchlings were collected on emergence and their size, mass, scalation and locomotor performance were measured. Neither clutch size nor nest depth had a significant effect on hatching success, emergence success or escape success in this study. Smaller clutches had longer incubation durations due to the lower temperatures within the nest, presumably from the lower metabolic heat produced. Hatchlings from deeper nests emerged later in the night than did those from shallower nests. Within the context of this study, changes to clutch size and nest depth appear to have no detrimental effect on the fate of the remaining eggs and the condition and performance of hatchlings.