Population divergence in cold tolerance of the intertidal gastropod Littorina brevicula explained by habitat-specific lowest air temperature

作者：Chiba Susumu^*; Iida Takeshi; Tomioka Aya; Azuma Noriko; Kurihara Takeo; Tanaka Kazuhiro

来源：Journal of Experimental Marine Biology and Ecology, 2016, 481: 49-56.

DOI：10.1016/j.jembe.2016.04.009

• Cold hardiness
• Freeze tolerance
• Intertidal gastropod
• Latitude
• Littorinidae

Temperature is a fundamental element determining the distribution patterns of ectotherms, and it is generally recognized that physiological tolerances of ectotherms change according to thermal gradients in their habitats. However, little is known about the variation in cold tolerance of marine invertebrates among local populations of the same species. In this study, three experiments were conducted to demonstrate inter-population variation in the cold tolerance of the intertidal gastropod Littorina brevicula, and to explore factors driving the variation. First, seasonal changes in the freezing temperature (the supercooling point, SCP) and the median lower lethal temperature (LLT50) of snails collected from a single population were examined to identify the cold tolerance strategies of this species. Seasonal fluctuation was clear in only the LLT50 which was lower than the SCP in winter, indicating that cold tolerance strategy of this species was freeze tolerant. Second, the cold tolerance of snails from four populations was compared. These populations were distributed at latitudinally different locations, and the comparisons were performed before winter when their cold tolerance was not required and in winter when their cold tolerance increased. In this experiment, while the cold tolerance of snails collected in winter was higher than that of snails collected before winter in all four populations, there were differences in tolerance among the populations. Furthermore, to estimate their ability of acclimation to cold environments, snails that were collected from the northernmost and southernmost populations in the four populations before winter were acclimated to a constant low temperature in the laboratory for a long period (120-130 days). This long period of acclimation led to an increase in the cold tolerance of both populations, but the latitudinal difference was maintained. Additionally, after imposing the long period of acclimation to snails that were collected at 12 locations before winter, factors that might cause local variation in their cold tolerance were explored. This experiment clearly showed that local variation in cold tolerance was explained by the lowest local air temperature. Our study demonstrated inter population variation in the cold tolerance of an intertidal mollusc, and that the variation is explained by thermal gradients in winter.

• 出版日期2016-8