Tentaculate ambush predators in 3D: Trophic effects of tentacle arrangement and morphology in an understudied group

Food web links influence how energy flows through the ocean and are therefore of broad interest to marine scientists. One group of marine predators that are widespread but not well understood are jellyfish and other gelatinous animals that use tentacles to hunt and ambush their prey. Emerging evidence shows that through predation with specialized tentacles, different gelatinous predators hunt different prey types, and these hunting preferences vary widely even within closely related species. This project addresses how jellies with diverse body shapes, tentacle structures and ways of hunting impact the balance of marine food webs in distinct ways. The team is using cutting-edge techniques, such as underwater cameras, microscopy, laser-based scanning and machine learning, in novel and multi-scale ways to achieve unprecedented resolution of predator prey relationships in three dimensions. These approaches allow the team, for the first time, to accurately reconstruct the predation strategies across these gelatinous ambush predators from individual cells to whole ecosystems. This project includes research training for postdoctoral scientists and undergraduate students, and educational outreach to middle and high school students. Project results are being communicated to broad audiences by working with artists and leveraging the unique video and imagery created during the research process. Tentaculate ambush predators (TAPs) are a functional group of gelatinous marine organisms that wait motionless to capture their motile prey through contact with sticky and/or stinging tentacles. TAPs comprise three distantly related taxa–siphonophores, cydippid ctenophores, and hydromedusae–and are ubiquitous and abundant throughout coastal, open ocean and midwater ecosystems. TAPs may be critical for structuring marine communities, but knowledge of their feeding impacts and mechanisms is limited. Quantifying trophic effects has been hampered by the challenge of working with fragile gelatinous organisms, which are often absent or underrepresented in net samples and do not behave naturally in the lab. This project uses new in situ imaging techniques that minimally disturb fragile plankton to quantify: 1) tentacle array structures, 2) prey-capture cell distributions, 3) tentacle deployment behaviors, 4) prey capture location, 5) prey encounter rates and ingestion, and 6) ecosystem level predation impacts of TAPs. The resulting mechanistic basis for prey capture are applicable to current and future measurements of tentaculate prey abundance, improving predation impact estimates and parameterization of food web models ranging from regional to global scales. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.