Gardiner Jayne M, Atema Jelle
Boston University Marine Program, Marine Biological Laboratory, Woods Hole, MA 02543, USA.
J Exp Biol. 2007 Jun;210(Pt 11):1925-34. doi: 10.1242/jeb.000075.
Odor plumes are complex, dynamic, three-dimensional structures used by many animals to locate food, mates, home sites, etc. Yet odor itself has no directional properties. Animals use a variety of different senses to obtain directional information. Since most odor plumes are composed of dispersing odor patches and dissipating vorticity eddies, aquatic animals may localize odor sources by simultaneous analysis of chemical and hydrodynamic dispersal fields, a process referred to as eddy chemotaxis. This study examines the contributions of olfaction, mechanoreception and vision to odor source localization in a shark, the smooth dogfish Mustelus canis. Two parallel, turbulent plumes were created in an 8 m flume: squid rinse odor and seawater control. Minimally turbulent ;oozing' sources of odor and seawater control were physically separated from sources of major turbulence by placing a brick downstream from each oozing source, creating two turbulent wakes, one or the other flavored with food odor. This created four separate targets for the sharks to locate. Animals were tested under two light conditions (fluorescent and infrared) and in two sensory conditions (lateral line intact and lateral line lesioned by streptomycin). Intact animals demonstrated a preference for the odor plume over the seawater plume and for the source of odor/turbulence (the brick on the odor side) over the source of the odor alone (the odor-oozing nozzle). Plume and target preference and search time were not significantly affected by light condition. In the light, lesioning the lateral line increased search time but did not affect success rate or plume preference. However, lesioned animals no longer discriminated between sources of turbulent and oozing odor. In the dark, search time of lesioned animals further increased, and the few animals that located any of the targets did not discriminate between odor and seawater plumes, let alone targets. These results demonstrate for the first time that sharks require both olfactory and lateral line input for efficient and precise tracking of odor-flavored wakes and that visual input can improve food-finding performance when lateral line information is not available. We distinguish between rheotaxis: orientation to the large-scale flow field (olfaction, vision and superficial lateral line), eddy chemotaxis: tracking the trail of small-scale, odor-flavored turbulence (olfaction and lateral line canals), and pinpointing the source of the plume (lateral line canals and olfaction).
气味羽流是复杂、动态的三维结构，许多动物利用它来定位食物、配偶、栖息地等。然而气味本身没有方向性。动物利用多种不同的感官来获取方向信息。由于大多数气味羽流由分散的气味斑块和消散的涡旋涡流组成，水生动物可能通过同时分析化学和流体动力扩散场来定位气味源，这一过程称为涡旋趋化作用。本研究考察了嗅觉、机械感受和视觉在鲨鱼（平滑狗鲨，犬鲛）气味源定位中的作用。在一个8米长的水槽中产生了两股平行的湍流羽流：鱿鱼冲洗液气味羽流和海水对照羽流。通过在每个渗出源下游放置一块砖块，将最小湍流的“渗出”气味源和海水对照源与主要湍流源物理隔开，形成两个湍流尾流，其中一个或另一个带有食物气味。这为鲨鱼创造了四个单独的目标来定位。在两种光照条件（荧光和红外）和两种感官条件（侧线完整和用链霉素损伤侧线）下对动物进行测试。完整的动物表现出对气味羽流比对海水羽流更偏好，对气味/湍流源（气味一侧的砖块）比对单独的气味源（气味渗出喷嘴）更偏好。羽流和目标偏好以及搜索时间不受光照条件的显著影响。在光照下，损伤侧线会增加搜索时间，但不影响成功率或羽流偏好。然而，受损动物不再区分湍流气味源和渗出气味源。在黑暗中，受损动物的搜索时间进一步增加，并且少数找到任何目标的动物不再区分气味羽流和海水羽流，更不用说目标了。这些结果首次表明，鲨鱼需要嗅觉和侧线输入才能高效、精确地追踪有气味的尾流，并且当侧线信息不可用时，视觉输入可以提高觅食性能。我们区分了趋流性：对大规模流场的定向（嗅觉、视觉和浅侧线）、涡旋趋化作用：追踪小规模、有气味的湍流轨迹（嗅觉和侧线管）以及确定羽流的源头（侧线管和嗅觉）。
