入侵性红耳滑龟与土著乌龟幼体游泳、翻身及心率表现的差异

Abstract

为检验入侵性龟类是否在某些功能表现上较土著龟类具显著优势，将相同孵化环境中孵出的红耳滑龟和乌龟幼体在不同测试温度下测定其运动（游泳和翻身）和心率表现。结果显示：所检测的两种龟幼体功能指标均随测试温度的变化而变化；红耳滑龟幼体比乌龟幼体具有较快的游泳速度和心率，但较慢的翻身速度。此外，通过比较来自不同养殖群体的两种龟幼体发现：低纬度的海口养殖群个体比高纬度的海宁养殖群个体具有较快的心率、较好的运动表现。结合已发表的临界高低温数据对不同指标构建热功能曲线发现：红耳滑龟幼体游泳速度的热表现宽度大于乌龟幼体，翻身反应的热表现宽度反而较小；海宁养殖群的游泳速度和翻身反应的热表现宽度大于海口养殖群个体。表明：较强游泳能力及能在较宽的热范围内实现较好的游泳表现、较高代谢水平可能有助于入侵性红耳滑龟在新环境中快速扩散、与其它物种竞争取胜并实现其成功入侵。红耳滑龟未表现出较快的翻身速度可能与因其相对较扁平的体型而导致的翻身较难有关。;The invasive species are believed to perform better than native species in many aspects of physiology and behavior. Thermal physiological performance, one of the most crucial traits potentially determining the invasion success of alien species, has only been investigated experimentally in a few comparative studies of invasive and native species.In order to assess the superiority of some functional performances in invasive turtles over native ones, we incubated 160 eggs of Trachemys scripta elegans and Mauremys reevesii from two different cultured cohorts (Haikou-a low-latitude site and Haining-a high-latitude site, 40 eggs from each cultured cohort of both species) under an identical laboratory condition[(29±1)℃, -220 kPa substrate water potential], and randomly selected 80 hatchlings (20 individuals from each cultured cohort of both species) to measure their locomotor performances (swimming speed and righting time) and heart rate at seven different test temperatures (16, 20, 24, 28, 32, 36 and 40℃). A laterally positioned digital video camera was used to record the swimming performance of each turtle in a racetrack with 10 cm water depth in the swimming tests, while a perpendicularly positioned camera was used to record the righting performance of each turtle in an open box in the righting tests. Videoclips were examined later for the average swimming speed over 30 cm, and righting time. An infrared heart rate monitor was used to measure the heart rate (beat per minute) of each turtle. Test temperature significantly affected swimming speed, righting time, and heart rate in hatchlings of both turtle species. T. scripta elegans hatchlings appeared to have a greater swimming speed and heart rate, but needed more time to right themselves than M. reevesii hatchlings. Individuals from the Haikou cohort had a greater swimming speed, heart rate, and shorter righting time than those from the Haining cohort. We used the curve-fitting procedure of TableCurve 2D to construct thermal performance curves (TPCs) based on the exponentially modified Gaussian model for each locomotor and physiological variable, and then extracted two parameters[the maximal performance (P_m) and thermal performance breadth at 80% level of maximal performance (B₈₀)] from each constructed TPC. Similarly, T. scripta elegans hatchlings had a higher P_m for swimming speed and heart rate, but lower P_m for the reciprocal of righting time than M. reevesii hatchlings; individuals from the Haikou cohort had a higher P_m for swimming speed, heart rate and reciprocal of righting time than those from the Haining cohort. T. scripta elegans hatchlings had a wider B₈₀ for swimming speed than M. reevesii hatchlings, but not for heart rate and reciprocal of righting time;individuals from the Haikou cohort had narrower B80 for swimming speed and reciprocal of righting time than those from the Haining cohort. These results probably indicated that T. scripta elegans had better locomotor and physiological performances (e.g., faster swimming speed and greater thermal plasticity) than M. reevesii, which might contribute to its invasive success in a novel environment. Compared with M. reevesii hatchlings, T. scripta elegans hatchlings righted themselves more slowly, probably due to their more flattened body shape.