Hoover R C, Hawkins Olivia H, Rosen Jack, Wilson Conrad D, Crawford Callie H, Holst Meghan M, Huie Jonathan M, Summers Adam P, Donatelli Cassandra M, Cohen Karly E
Department of Biology, University of Louisiana at Lafayette, Lafayette, LA, 70503, USA.
Department of Biology, Tufts University, Medford, MA 02155, USA.
Integr Comp Biol. 2023 Sep 15;63(3):796-807. doi: 10.1093/icb/icad076.
Armor is a multipurpose set of structures that has evolved independently at least 30 times in fishes. In addition to providing protection, armor can manipulate flow, increase camouflage, and be sexually dimorphic. There are potential tradeoffs in armor function: increased impact resistance may come at the cost of maneuvering ability; and ornate armor may offer visual or protective advantages, but could incur excess drag. Pacific spiny lumpsuckers (Eumicrotremus orbis) are covered in rows of odontic, cone-shaped armor whorls, protecting the fish from wave driven impacts and the threat of predation. We are interested in measuring the effects of lumpsucker armor on the hydrodynamic forces on the fish. Bigger lumpsuckers have larger and more complex armor, which may incur a greater hydrodynamic cost. In addition to their protective armor, lumpsuckers have evolved a ventral adhesive disc, allowing them to remain stationary in their environment. We hypothesize a tradeoff between the armor and adhesion: little fish prioritize suction, while big fish prioritize protection. Using micro-CT, we compared armor volume to disc area over lumpsucker development and built 3D models to measure changes in drag over ontogeny. We found that drag and drag coefficients decrease with greater armor coverage and vary consistently with orientation. Adhesive disc area is isometric but safety factor increases with size, allowing larger fish to remain attached in higher flows than smaller fish.
甲胄是一组多功能的结构，在鱼类中至少独立进化了30次。除了提供保护外，甲胄还可以控制水流、增强伪装能力，并且具有两性异形。甲胄功能存在潜在的权衡：抗冲击能力的增强可能以机动性为代价；华丽的甲胄可能具有视觉或保护优势，但可能会产生额外的阻力。太平洋刺躄鱼（Eumicrotremus orbis）全身覆盖着一排排齿状的锥形甲胄螺环，保护鱼免受海浪冲击和捕食威胁。我们感兴趣的是测量刺躄鱼甲胄对鱼体水动力的影响。体型较大的刺躄鱼拥有更大、更复杂的甲胄，这可能会带来更高的水动力成本。除了保护性的甲胄外，刺躄鱼还进化出了一个腹侧吸盘，使它们能够在所处环境中保持静止。我们推测甲胄和吸附能力之间存在权衡：小鱼优先考虑吸附，而大鱼优先考虑保护。我们使用微型计算机断层扫描（micro-CT），比较了刺躄鱼发育过程中甲胄体积与吸盘面积，并构建了三维模型来测量个体发育过程中阻力的变化。我们发现，随着甲胄覆盖面积的增加，阻力和阻力系数会降低，并且随方向一致变化。吸盘面积呈等比缩放，但安全系数随体型增大而增加，这使得大鱼比小鱼能够在流速更高的水流中保持附着状态。
