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 Selleck DAPT 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. “
“Recent years have witnessed a resurgence in tests of the evolution selleck products and origin of the great height and long neck of the Staurosporine datasheet giraffe Giraffa camelopardalis. The two main hypotheses are (1) long necks evolved through competition with other browsers allowing giraffe to feed above them (‘competing browsers’ hypothesis); or (2) the necks evolved for direct use in intra-sexual combat to gain access to oestrous females (‘necks-for-sex’ hypothesis). Here, we review recent developments and their relative contribution in explaining giraffe evolution. Trends from Zimbabwean giraffes show
positive allometry for male necks and isometry for female necks relative to body mass, while comparative analyses of the cervical versus the total vertebral column of the giraffe, okapi and fossil giraffe suggest selection specifically on neck length rather than on overall height. Both support the necks-for-sex idea. Neither study, however, allows us to refute one of the two ideas. We suggest new approaches for quantifying the relative importance of the two hypotheses. A direct analysis of selection pressure on neck length via survival and reproduction should clarify the mechanism maintaining the trait, while we predict that short robust ossicones should have arisen concurrently with incipient neck elongation if sexual selection was the main selective driver.