Maternal and environmental influences on growth and survival of embryonic and hatchling snapping turtles (Chelydra serpentina)

Abstract

Clutches of six female snapping turtles (Chelydra serpentina) each were distributed among six incubators set at one of three constant temperatures (22.0, 25.6, and 28.6 °C) in either a wet (−100 kPa) or a dry (−500 kPa) vermiculite substrate. We tested for influences of egg mass, clutch, and incubation temperature and moisture on survival of embryos and hatchlings, on size at hatching, and on rate of post-hatching growth over 7 months. Intraclutch variation in egg mass had no effect on embryonic mortality. Mass at hatching was correlated with egg mass, but neither variable was related significantly to post-hatching survival or rate of growth. Eggs incubated at the highest temperature produced smaller hatchlings which subsequently grew more slowly than those from eggs incubated at the low and intermediate temperatures. Eggs incubated at the intermediate temperature produced larger turtles at 7 months post-hatching than did eggs incubated at the low or high temperatures. Eggs incubated in wet substrates produced larger hatchlings than those in dry substrates, but post-hatching growth rates were independent of these effects of moisture. Eggs incubated at the two extreme temperatures produced mostly females; those at 25.6 °C produced only males. Interclutch variation was significant for egg mass, mass at hatching, and survival of embryos, and was the most important influence on variation in post-hatching rates of growth. These results indicate that egg size and size at hatching may not be useful indicators of intraspecific variation in egg quality or post-hatching success in turtles, unless differences among clutches and embryonic thermal experience are also considered, particularly in relation to parental investment in the amount, quality, and apportionment of the egg's yolk.

Experimental Analysis of an Early Life-History Stage: Selection on Size of Hatchling Turtles

“…A four-year study of a cohort of painted turtles documented a positive relationship between body size at hatching and longevity in the laboratory (Brodie and Janzen 1996), suggesting persistent fitness benefits of increased offspring size, although a sevenmonth laboratory study of hatchling common snapping turtles apparently found no such relationship (Brooks et al 1991). However, juvenile turtles experience much higher mortality rates in nature than in these two enclosure experiments (e.g., Galbraith and Brooks 1987, Frazer et al 1990, Congdon et al 1993, possibly because individuals are exposed to numerous predators in natural habitats (Janzen et al 1992, Lindeman 1993.…”

Slight differences in incubation temperature affect early growth and stress endocrinology of wood duck (Aix sponsa) ducklings

“…In reptiles, incubation temperature has been shown to influence traits important to population dynamics and individual fitness, including offspring sex ratios, body size, body morphology, growth rate, locomotor performance, behavior and survival (Bull, 1980;Joanen et al, 1987;Burger, 1990;Brooks et al, 1991;Van Damme et al, 1992;Shine et al, 1997;Angilletta, 2000;Booth et al, 2000;Nelson et al, 2004). By contrast, the effect of incubation conditions on hatchling fitness in birds is poorly understood.…”

Temperature-Dependent Sex Determination in Vertebrates

“…Consequently, TSD evolution may be constrained in different taxa (but see Rhen and Lang 1998) by lack of genotype-by-temperature interaction (e.g., Janzen 1992), by nest temperature variance (Bull et al 1982a), or by maternal effects (Bowden et al 2000). Nonetheless, clutch identity affects reptilian phenotypes (Bull et al 1982a;Brooks et al 1991;Van Damme et al 1992;Janzen 1993; Allsteadt and Lang 1995a; Shine and Harlow 1996;Shine et al 1997a,b), and components other than additive genetic variance can substantially affect sex determination.…”