A mechanosensory system that controls feeding in adult Mnemiopsis

Abstract

We describe here the food groove complex and mechanism of prey capture used by adult Mnemiopsis spp. ctenophores to obtain prey swept into the auricular grooves by feeding currents. Tentilla that emerge from the tentacular groove of the food groove complex extend into the auricular grooves and capture prey upon their sticky surfaces. The prey-laden tentilla contract and drag the prey to the edge of the transport groove, which is also part of the food groove complex. The transport groove undergoes a focal eversion to capture and transport prey orally. Focal eversion exposes the inner ciliated surface of the transport groove as it extends toward the prey. Focal eversion can be evoked by mechanical stimuli from a probe, but only if it is positioned directly over the tentacular groove. We propose that g-cilia located within the tentacular groove are mechanoreceptors whose output triggers a sensory-motor pathway that in turn everts the transport groove. The mechanosensory-motor pathway is ectodermal and sensitive to Mg²⁺ anesthesia, which defocuses and amplifies eversion. Tentilla are not strictly necessary for eversion to occur, because preparations lacking tentilla can still display eversion; however, they may amplify the sensory signal by interacting with g-cilia as they contract.