Low predation intensity on the stalked crinoid Democrinus sp. (Echinodermata), in Roatán, Honduras, reveals deep water as likely predation refuge

Abstract

Predation has been hypothesized to play a key role in the evolutionary and ecological history of crinoids. Whereas evidence of predation on crinoids in the form of injuries can be common, quantifying predation intensity, which is critical for properly evaluating such hypotheses, has proven challenging. Here, we used a longitudinal approach to quantify predation intensity on the extant, deepwater, stalked crinoid, Democrinus sp. These quantitative estimates are based on data collected from a manned submersible during expeditions conducted over a 2-yr span. These results indicate that this deepwater crinoid is subject to much lower predation intensity than are crinoids living in shallow-water, consistent with (1) an inverse relationship between predation intensity and depth, and (2) the hypothesis that for stalked crinoids, which are unable to handle high predation intensity, deep water is a refugium.