Interclutch and interpopulation variation in the effects of incubation conditions on sex, survival and growth of hatchling turtles (Chelydra serpentina)

Abstract

With 5 figures in the text)We tested the hypothesis that larger egg and hatchling sizes in the snapping turtle confer posthatching advantages, by comparing the growth rates and survival of hatchlings from different thermal and hydric environments during embryonic development. We also tested for sex-specific differences in survival and growth, two indices of hatchling fitness, as predicted by the Charnov & Bull (1977) model of environmental sex determination (ESD). In addition, we examined interclutch and interpopulation variability in the responses of embryos and hatchlings to incubation conditions. Eggs of 21 clutches from four Ontario populations were incubated at 22,0,25,5 or 29·3°C in a dry (-350 kPa) or wet (-150 kPa) vermiculite substrate, and hatchling survival and growth in the laboratory were monitored for 11 months. Initial egg mass and substrate moisture were positively correlated with mass at hatching, but did not affect hatching success, posthatching growth or posthatching survival. Initially heavier hatchlings were more likely to survive, but did not grow more quickly. The effects of incubation environment and hatchling mass were not consistent among clutches or populations. Intermediate incubation temperatures produced mostly males, with higher embryo and hatchling survival, as well as posthatching growth, than the mostly females from the extreme temperatures. These results support the Charnov-Bull model. Embryo and hatchling mortality and deformities were higher in clutches from two populations which are contaminated with organochlorine toxins. Interclutch differences were significant for all variables, even when initial egg or hatchling sizes were considered. Hatchlings from the population near the northern limit of the species' range grew the slowest. These results indicate that hatchling size cannot be used as an index of hatchling quality or posthatching success, unless interclutch and interpopulation variation are taken into account.

Effect of tidal overwash on the embryonic development of leatherback turtles in French Guiana

“…Hatching success for organisms that lay eggs in a nest, such as sea turtles, is believed to be influenced by numerous biotic and abiotic factors such as predation, type of substrate, porosity, temperature, moisture content, salinity, slope of the beach, nest elevation, rainfall and tidal inundation (Mortimer, 1990;Horrocks and Scott, 1991;Ackerman, 1997;Wood and Bjorndal, 2000;Allen et al, 2001;Bilinski et al, 2001;Donlan et al, 2004;Foley et al, 2006). In many oviparous reptiles, however, environmental factors not only influence embryo survivorship (Horrocks and Scott, 1991;Resetarits, 1996), but also hatchling size (Packard and Packard, 1988), performance (Janzen, 1993), growth (Bobyn and Brooks, 1994), behaviour (Burger, 1991), and sex determination (Spotila et al, 1994). After the emergence of hatchling turtles, their survival may be strongly related to the distance at which the nest is laid from the sea and from supra-littoral vegetation behind the beach (Mrosovsky, 1983).…”

Temperature-Dependent Sex Determination in Vertebrates

“…That different incubation temperatures can affect the hatchling phenotype via differences in size, color, growth rates, locomotor ability, and many other characteristics that may ultimately influence survival or reproductive fitness is well recorded in the reptile literature (e.g., Joanen et al 1987; Bobyn and Brooks 1994;O'Steen 1998). These effects are seen in both TSD and GSD species (Rhen and Lang,Chapter 10).…”

“…Whereas temperature effects on certain traits may be mediated by temperature-induced variation is sex steroid levels in some species, studies in snapping turtles indicate 96 T. Rhen and J. W. Lang McKnight and Gutzke 1993Bobyn and Brooks 1994Spotila et al 1994Roosenburg 1996Roosenburg and Kelley 1996Foley 1998Demuth 2001Janzen and Morjan 2002 that temperature can have effects mediated via alternative mechanisms. In experiments described earlier, snapping turtle embryos were treated with exogenous estrogen or a potent aromatase inhibitor at the beginning of the thermosensitive period (TSP).…”

“…Under those circumstances, parental ability to bias sex ratios accordingly is also favored. Survival Differential mortality Burger and Zappalorti 1988Janzen 1995Rhen and Lang 1995Bobyn and Brooks 1994Elphick and Shine 1999Gutzke and Packard 1987aJoanen et al 1987 Fecundity Sexual size dimorphism Head et al 1987Allsteadt and Lang 1995aAllsteadt and Lang 1995aBobyn and Brooks 1994Webb et al 1987 Phenotypic effects Allsteadt and Lang 1995aArnold et al 1995Braña and Ji 2000 Crews et al 1998 Bull and Charnov 1989Demuth 2001Gutzke and Crews 1988Packard and Packard 2001Elphick and Shine 1999Rhen and Lang 1999bGutzke et al 1987…”

Reproductive ecology of the Beal’s-eyed turtle (Sacalia bealei)

“…Studies of turtle 33 reproductive ecology have revealed important direct and indirect effects on fitness and 34 demography (Bobyn & Brooks, 1994;Weisrock & Janzen, 1999;Valenzuela, 2001; Spencer and 35 Thompson, 2003;Janzen et al, 2007). For example, research on the snapping turtle (Chelydra 36 serpentina) found that initial egg mass and substrate moisture were positively correlated with 37 hatchling mass, which could then affect hatchling survival (Bobyn & Brooks, 1994 (Zhang et al, 1998). Since 2014, we conducted field studies focusing on 46 habitat selection, home rage, and reproductive ecology through methods of radio telemetry, 47 spool-and-line tracking, and direct observation (Hu, 2016).…”