福寿螺的过冷却研究

福寿螺是IUCN认定的世界100种恶性外来入侵物种之一,在华南地区已对水稻生产造成严重危害。福寿螺属于热带软体动物,采用万用电表联接热敏电阻法研究了福寿螺在低温胁迫下的过冷却点,并探讨了不同个体福寿螺在过冷却发生后的死亡率和体内组织损伤。结果表明: 1)各种螺高的福寿螺冷却点均值为-6.96 ℃,范围在-6.21--7.32 ℃之间,恢复最高体温均值为-4.07 ℃,范围在-3.07--4.93 ℃之间,过冷却后维持时间均值为45.97 min,范围在18.60-75.34 min;2)福寿螺的过冷却点大小受螺高影响,螺高35 mm≤H<45 mm的福寿螺过冷却点显著高于5 mm≤H<15 mm、15 mm≤H<25 mm、25 mm≤H<35 mm体型的福寿螺,5-35 mm螺高的福寿螺过冷却点变化稳定;3)福寿螺在发生过冷却阶段的死亡率在23.33%-36.67%之间,不同体型的福寿螺之间没有显著性差异;4)过冷却后福寿螺死亡率随暴露时间的延长而提高,0到15 min内由20.9%提高到100%,过冷却后暴露时间对福寿螺死亡率影响较大;5)发生过冷却15 min后取出的福寿螺,染色后其外套膜有少量红色出现,而肾部和消化腺部未呈现明显红色,低温胁迫已经对福寿螺组织造成了显著损伤。本研究结果对于进一步探索福寿螺的生态适应性、扩散北界及福寿螺的越冬机制有一定参考价值。

Study on the supercooling of golden apple snail (Pomacea canaliculata)

The golden apple snail(Pomacea canaliculata) is considered one of the 100 worst invasive alien species by the Invasive Species Specialist Group of the International Union for Conservation of Nature.The golden apple snail was introduced into China around 1980 from South America for commercial purposes.However,it proved to be a failure on the market over the next few years.Consequently,golden apple snails were disposed of into rivers,canals and paddy fields.Since then,P.canaliculata has resulted in massive rice production losses in South China.Although P.canaliculata is a tropical mollusk species,its cold-hardiness has been reported recently in some studies.Supercooling point is an important index for reflecting the resistance of many creatures including mammals,insects and molluscs in low temperature environments.According to many studies,molluscs also exhibit diverse physiological responses to low temperature environments.However,no studies on supercooling points and physiological responses were performed on P.canaliculata from South China to low temperature stress.In this study,supercooling points of P.canaliculata from South China were determined using a device composed of multimeter determination connected with thermistors.Moreover,mortalities and organ injuries to P.canaliculata of different shell heights during supercooling periods were studied.Results showed that the mean value of supercooling points of snails of different heights was-6.96℃,ranging from-6.21℃ to-7.32℃.The mean value of maximum body temperature in recovery stage was-4.07℃,ranging from-3.07℃ to-4.93℃;the mean supercooling time of P.canaliculata of different heights was 45.97 min,ranging from 18.60 min to 75.34 min.Change in the supercooling point value correlated with the height of P.canaliculata,and the supercooling point of snails with a height of 35 mm≤H<45 mm was significantly higher than those of snails with heights of 5 mm≤H<15 mm,15 mm≤H<25 mm and 25 mm≤H<35 mm,respectively.It was concluded that the supercooling point of P.canaliculata whose height ranged from 5 to 35 mm was consistent to some extent.The mortality of P.canaliculata in the supercooling stage ranged from 23.33% to 36.67%,and there were no significant differences among mortalities of P.canaliculata of different heights.Mortality of P.canaliculata correlated with increased exposure time,and ranged from 20.9% to 100% in 15 min.This experiment showed that exposure time could greatly influence the mortality of P.canaliculata.Photographs of organs color-stained by 2,3,5-triphenyltetrazolium chloride(TTC) showed a slight red staining on the mantle,which was not obvious on the digestive gland or the kidney of a dead snail,obtained after supercooling for 15 min.Low temperatures resulted in significant organ injury in P.canaliculata.Results obtained from this study will assist further investigation of the ecological adaptation,the northern limit to potential areas of invasion and the survival mechanism of P.canaliculata over winter.