Effects of temperature on larval swimming patterns regulate vertical distribution relative to thermoclines in Asterias rubens

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• 作者：Cylia V. Civelek ; ^{cylia.civelek@dal.ca} ; Ré ; mi M. Daigle ; Anna Metaxas
• 关键词：Larval behavior ; Survival ; Swimming path ; Thermal tolerance ; Thermocline ; Vertical distribution
• 刊名：Journal of Experimental Marine Biology and Ecology
• 出版年：2013
• 出版时间：July, 2013
• 年：2013
• 卷：445
• 期：Complete
• 页码：1-12
• 全文大小：1070 K

文摘

Asteroid larvae rely mainly on currents for dispersal, predator avoidance, and the location of resources. At small scales, larvae can regulate their vertical positions in the water column by swimming, and consequently, can affect their horizontal displacement. In this study, we examined the effect of water temperature on the survival of larval Asterias rubens, as well as on larval swimming patterns around thermal gradients of various strengths. A response to thermal gradients can be a result of physiological and/or physical processes to improve long-term survival and consequently, facilitate dispersal. We induced spawning of A. rubens in the laboratory, and reared larvae for 5 and 10 days. Percent larval survival in temperatures ranging from 6 to 32 ¡ãC was determined over 48 h. Temperatures between 6 and 24 ¡ãC did not affect survival of 5- or 10-d larvae. For 10-day larvae, low mortality (21.5 % ) was observed in 28 ¡ãC, and 100 % mortality at 32 ¡ãC within 6 h, suggesting a threshold in survival between the two temperatures. Ten-day old larvae were placed in rectangular plexiglass chambers with homogeneous (6, 12, 18, and 24 ¡ãC) or thermally-structured water columns that were generated in the laboratory, in which the temperature in the surface and bottom layers was 24 and 12, 18 and 12, 18 and 6, and 12 and 6 ¡ãC, respectively. Larval swimming patterns were videotaped for 30 min and footage was analyzed at 5-min intervals to measure speeds and vertical velocities of all visible larvae using pairs of consecutive frames. Swimming paths were examined by following 21 randomly selected (every 81 s) larvae in each treatment for as long as possible. In the absence of a thermal gradient, larval vertical velocity showed a parabolic relationship with temperature, unlike larval speed, which increased linearly, regardless of thermal structure. Net to gross displacement rate was measured for each larval path, and showed a decrease over time, but did not vary with temperature. We concluded that vertical patterns in larval distribution with respect to thermoclines reflect changes in vertical velocity rather than an enhancement of short-term survival. Larval swimming behavior influences vertical distribution, and ultimately, dispersal, settlement and adult populations.