Sotka Erik E, McCarty Amanda, Monroe Emily A, Oakman Nicole, Van Dolah Frances M
Grice Marine Laboratory and Department of Biology, College of Charleston, 205 Fort Johnson Road, Charleston, SC 29412, USA.
J Chem Ecol. 2009 Jul;35(7):851-9. doi: 10.1007/s10886-009-9658-9. Epub 2009 Jul 11.
Gulf of Mexico blooms of the dinoflagellate Karenia brevis produce neurotoxic cyclic polyethers called brevetoxins. During and after a red tide bloom in southwestern Florida, K. brevis cells lyse and release brevetoxins, which then sink to the benthos and coat the surfaces of seagrasses and their epiphytes. We tested the possibility that these brevetoxin-laden foods alter the feeding behavior and fitness of a common benthic herbivore within Floridean seagrass beds, the amphipod Ampithoe longimana. We demonstrated that coating foods with K. brevis extracts that contain brevetoxins at post-bloom concentrations (1 microg g(-1) drymass) does not alter the feeding rates of Florida nor North Carolina populations of A. longimana, although a slight deterrent effect was found at eight and ten-fold greater concentrations. During a series of feeding choice assays, A. longimana tended not to be deterred by foods coated with K. brevis extracts nor with the purified brevetoxins PbTx-2 and PbTx-3. Florida juveniles isolated with either extract-coated or control foods for 10 days did not differ in survivorship nor growth. A similar lack of feeding response to brevetoxin-laden foods also was exhibited by two other generalist herbivores of the southeastern United States, the amphipod A. valida and the urchin Arbacia punctulata. Given that benthic mesograzers constitute a significant portion of the diet for the juvenile stage of many nearshore fishes, we hypothesize that the ability of some mesograzers to feed on and retain brevetoxins in their bodies indicates that mesograzers may represent an important route of vertical transmission of brevetoxins through higher trophic levels within Gulf of Mexico estuaries.
墨西哥湾的短裸甲藻大量繁殖会产生名为短裸甲藻毒素的神经毒性环状聚醚。在佛罗里达州西南部赤潮爆发期间及之后，短裸甲藻细胞裂解并释放短裸甲藻毒素，这些毒素随后沉入底栖生物区，附着在海草及其附生植物的表面。我们测试了这些富含短裸甲藻毒素的食物是否会改变佛罗里达海草床中一种常见的底栖食草动物——长手沙钩虾的摄食行为和健康状况。我们发现，用含有短裸甲藻毒素的短裸甲藻提取物（赤潮后浓度为1微克/克干重）涂抹食物，并不会改变佛罗里达州或北卡罗来纳州长手沙钩虾种群的摄食率，不过在浓度高出八倍和十倍时发现了轻微的抑制作用。在一系列摄食选择试验中，长手沙钩虾往往不会受到涂有短裸甲藻提取物或纯化短裸甲藻毒素PbTx - 2和PbTx - 3的食物的抑制。用涂有提取物的食物或对照食物隔离饲养10天的佛罗里达幼虾，在存活率和生长方面没有差异。美国东南部的另外两种广食性食草动物——强壮沙钩虾和斑点海胆，对富含短裸甲藻毒素的食物也表现出类似的缺乏摄食反应的情况。鉴于底栖中型食草动物是许多近岸鱼类幼体阶段饮食的重要组成部分，我们推测，一些中型食草动物在体内摄食并留存短裸甲藻毒素的能力表明，中型食草动物可能是短裸甲藻毒素在墨西哥湾河口较高营养级中垂直传播的重要途径。
