Many predators fracture strong mollusk shells, requiring specialized weaponry and behaviors. The current shell fracture paradigm is based on jaw- and claw-based predators that slowly apply forces (high impulse, low peak force). However, predators also strike shells with transient intense impacts (low impulse, high peak force). Toward the goal of incorporating impact fracture strategies into the prevailing paradigm, we measured how mantis shrimp () impact snail shells, tested whether they strike shells in different locations depending on prey shape ( spp., , spp.) and deployed a physical model (Ninjabot) to test the effectiveness of strike locations. We found that, contrary to their formidable reputation, mantis shrimp struck shells tens to hundreds of times while targeting distinct shell locations. They consistently struck the aperture of globular shells and changed from the aperture to the apex of high-spired shells. Ninjabot tests revealed that mantis shrimp avoid strike locations that cause little damage and that reaching the threshold for eating soft tissue is increasingly difficult as fracture progresses. Their ballistic strategy requires feed-forward control, relying on extensive pre-strike set-up, unlike jaw- and claw-based strategies that can use real-time neural feedback when crushing. However, alongside this pre-processing cost to impact fracture comes the ability to circumvent gape limits and thus process larger prey. In sum, mantis shrimp target specific shell regions, alter their strategy depending on shell shape, and present a model system for studying the physics and materials of impact fracture in the context of the rich evolutionary history of predator-prey interactions.

Myrmecochory, a type of ant-mediated seed dispersal, is a diffuse, widespread mutualism in which both partners are purported to benefit from the services or rewards of the other. However, ant benefits in this interaction are conflicted and understudied, especially in the context of microbial third parties. Here, we investigate the effect of a myrmecochore plant-produced antimicrobial chemical (sanguinarine) on the growth of a common entomopathogenic fungus (Beauveria bassiana). We then explore whether sanguinarine, through its effect on entomopathogen growth, might influence ant survival and foraging behavior. At high concentrations, sanguinarine increased the growth of B. bassiana, but fungal growth was not affected at concentrations of sanguinarine near natural levels produced in seeds. When ant colonies were exposed to B. bassiana, survival was not affected by a sanguinarine-supplemented diet. Furthermore, ant foraging patterns (preference for or avoidance of food items with sanguinarine) did not change when ants were exposed to the entomopathogen. Though sanguinarine promotes the growth of an entomopathogen at higher concentrations, which might pose an additional risk for ants in myrmecochory, we assert that social immune behavioral defenses (such as grooming or redispersal of seeds after elaiosome Terms of use and reuse: academic research for non-commercial purposes, see here for full terms. https://www.springer.com/aamterms-v1