Data from: Strike mechanics of an ambush predator: the spearing mantis shrimp

Ambush predation is characterized by an animal scanning the environment from a concealed position and then rapidly executing a surprise attack. Mantis shrimp (Stomatopoda) consist of both ambush predators (ʻspearersʼ) and foragers (ʻsmashersʼ). Spearers hide in sandy burrows and capture evasive prey, whereas smashers search for prey away from their burrows and typically hammer hard-shelled, sedentary prey. Here, we examined the kinematics, morphology and field behavior of spearing mantis shrimp and compared them with previously studied smashers. Using two species with dramatically different adult sizes, we found that strikes produced by the diminutive species, Alachosquilla vicina, were faster (mean peak speed 5.72±0.91 m s^−1; mean duration 3.26±0.41 ms) than the strikes produced by the large species, Lysiosquillina maculata (mean peak speed 2.30±0.85 m s^−1; mean duration 24.98±9.68 ms). Micro-computed tomography and dissections showed that both species have the spring and latch structures that are used in other species for producing a spring-loaded strike; however, kinematic analyses indicated that only A. vicina consistently engages the elastic mechanism. In the field, L. maculata ambushed evasive prey primarily at night while hidden in burrows, striking with both long and short durations compared with laboratory videos. We expected ambush predators to strike with very high speeds, yet instead we found that these spearing mantis shrimp struck more slowly and with longer durations than smashers. Nonetheless, the strikes of spearers occurred at similar speeds and durations to those of other aquatic predators of evasive prey. Although counterintuitive, these findings suggest that ambush predators do not actually need to produce extremely high speeds, and that the very fastest predators are using speed to achieve other mechanical feats, such as producing large impact forces.

伏击式捕食的典型特征为动物隐蔽于隐秘位置扫描周遭环境，随后迅速发起突袭。螳螂虾（Stomatopoda）包含两类生态类群：伏击捕食者（spearers）与巡游觅食者（smashers）。矛型螳螂虾隐匿于沙质洞穴中，捕食灵活逃逸的猎物；锤型螳螂虾则会离开洞穴搜寻猎物，通常以坚硬外壳的固着性猎物为食，通过锤击完成捕猎。

本研究针对矛型螳螂虾的运动学、形态学与野外行为展开系统探究，并与此前已被深入研究的锤型螳螂虾进行对比分析。我们选取成体体型差异悬殊的两个物种开展实验：体型娇小的近缘小螳螂虾（Alachosquilla vicina）与体型较大的斑条琴螳螂虾（Lysiosquillina maculata）。结果显示，近缘小螳螂虾的攻击峰值速度更快，其平均峰值速度为5.72±0.91 m·s⁻¹，平均持续时长为3.26±0.41 ms；而斑条琴螳螂虾的平均峰值速度仅为2.30±0.85 m·s⁻¹，平均持续时长为24.98±9.68 ms。

显微计算机断层扫描（micro-computed tomography）与解剖实验结果表明，两个物种均拥有与其他物种用于实现蓄力突袭的弹簧-扣锁结构；但运动学分析显示，仅近缘小螳螂虾（A. vicina）会持续启用该弹性储能机制。野外观测结果显示，斑条琴螳螂虾主要于夜间隐蔽于洞穴中伏击灵活逃逸的猎物，其攻击时长相较于实验室拍摄的视频存在长短两种差异。

我们原本预判伏击捕食者的攻击速度会极高，但研究结果却与预期相悖：这些矛型螳螂虾的攻击速度慢于锤型螳螂虾，且持续时长更长。尽管如此，矛型螳螂虾的攻击速度与持续时长，与其他捕食灵活逃逸猎物的水生捕食者相近。尽管这一结果违背直觉，但本研究结果表明，伏击捕食者实际上并不需要极致的攻击速度；而那些速度极快的捕食者，实则是利用速度来实现其他力学功效，例如产生巨大的冲击力。