Brown Bryan L, Creed Robert P, Dobson William E
Department of Biology, Appalachian State University, Boone, N.C., 28608, USA.
Oecologia. 2002 Jul;132(2):250-255. doi: 10.1007/s00442-002-0961-1. Epub 2002 Jul 1.
Branchiobdellid annelids and their freshwater crayfish hosts are generally thought to have a commensal relationship. Branchiobdellids of the genus Cambarincola exploit their hosts through a variety of mechanisms; however, an effect of branchiobdellids on crayfish has not been conclusively demonstrated. We investigated whether branchiobdellids positively affect the host crayfish Cambarus chasmodactylus in the New River, North Carolina. In a laboratory experiment, we placed 0, 3, or 6 branchiobdellids on C. chasmodactylus and observed a significant effect of branchiobdellid presence on both growth and mortality of host crayfish; crayfish with branchiobdellids exhibited faster growth and lower mortality with increasing branchiobdellid density. A tracer experiment demonstrated that branchiobdellids feed on items found in the branchial chamber of C. chasmodactylus. We hypothesize that such feeding activity by branchiobdellids reduces fouling of crayfish gills by epibionts and particulate matter and could lead to the reduced mortality and increased growth rates observed in the laboratory experiment. Specifically, Cambarincola may improve the ventilatory and excretory fitness of C. chasmodactylus by cleaning gill filaments. Field data support this hypothesis by demonstrating that branchiobdellids are found disproportionately at sites proximal to the branchial chamber in the New River. This study provides evidence that the relationship between C. chasmodactylus and Cambarincola may be a cleaning symbiosis, at least in environments where gill fouling is a problem for C. chasmodactylus.
鳃蛭类环节动物与其淡水小龙虾宿主通常被认为是共生关系。坎氏鳃蛭属的鳃蛭类通过多种机制利用其宿主；然而，鳃蛭类对小龙虾的影响尚未得到确凿证明。我们调查了鳃蛭类是否对北卡罗来纳州新河的小龙虾宿主查氏坎氏螯虾有积极影响。在一项实验室实验中，我们在查氏坎氏螯虾上放置0只、3只或6只鳃蛭，并观察到鳃蛭的存在对宿主小龙虾的生长和死亡率都有显著影响；随着鳃蛭密度的增加，有鳃蛭的小龙虾生长更快，死亡率更低。一项示踪实验表明，鳃蛭以查氏坎氏螯虾鳃腔内发现的物质为食。我们推测，鳃蛭类的这种摄食活动减少了附着生物和颗粒物对小龙虾鳃的污染，这可能导致在实验室实验中观察到的死亡率降低和生长率提高。具体来说，坎氏鳃蛭可能通过清洁鳃丝来提高查氏坎氏螯虾的通气和排泄适应性。野外数据支持了这一假设，表明在新河鳃腔近端的地点发现的鳃蛭数量不成比例。这项研究提供了证据，证明查氏坎氏螯虾与坎氏鳃蛭之间的关系可能是一种清洁共生关系，至少在鳃污染对查氏坎氏螯虾来说是个问题的环境中是如此。
