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

Nontechnical abstract

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. The proposed research addresses how jellies with diverse body shapes, tentacle structures and ways of hunting impact the balance of marine food webs in distinct ways. We use techniques including 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. Used together, these approaches allow us, for the first time, to accurately reconstruct the predation strategies across these gelatinous ambush predators from individual cells to whole ecosystems.

Technical abstract

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 are fragmentary. 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 can be applied to current and future measurements of tentaculate prey abundance. The findings will improve predation impact estimates and parameterization of food web models ranging from regional to global scales.