GSA Annual Meeting in Phoenix, Arizona, USA - 2019

Paper No. 38-32
Presentation Time: 9:00 AM-5:30 PM


TENNAKOON, Shamindri1, JAMAL, Fatemah2, GRUN, Tobias B.3, PORTELL, Roger W.2, KOWALEWSKI, Michal2, PETSIOS, Elizabeth4 and TYLER, Carrie L.5, (1)Florida Museum of Natural History, University of Florida, 1659 Museum Road, Gainesville, FL 32611; Department of Biology, University of Florida, Gainesville, FL 32611; University of Peradeniya, Peradeniya, 20400, Sri Lanka, (2)Florida Museum of Natural History, University of Florida, 1659 Museum Road, Gainesville, FL 32611, (3)University of Florida, Invertebrate Paleontology, 1659 Museum Road, Gainesville, FL 32611, (4)Department of Geosciences, Baylor University, 101 Bagby Ave., Baylor Sciences Building, Waco, TX 76706, (5)Department of Geology and Environmental Earth Science, Miami University, Oxford, OH 45056

Many species of fish that prey on echinoids produce test damage that varies by predator and prey. For example, in the northeastern Gulf of Mexico, the grey triggerfish (Ballistes capriscus) has been observed feeding on sea urchins and sand dollars. While successful feeding attempts create a distinct hole in the test, unsuccessful or non-lethal attacks may produce marginal traces on the ambitus. However, these predator-prey relationships and resulting traces are underexplored relative to that of echinoids and predatory drilling gastropods. Therefore, here, we report preliminary results based on SCUBA sampling of live sand dollars preyed upon by triggerfish in the Gulf of Mexico and surveys of congeneric fossil species available in the Invertebrate Paleontology Collections at the Florida Museum of Natural History.

This pilot study included 148 sand dollar specimens collected at four sites on the shallow shelf of the northeastern Gulf of Mexico and included three species: Encope michelini (n=33), Mellita tenuis (n=52), and Clypeaster subdepressus (n=63). Cuspate shaped marks along the ambitus of the tests, and on some specimens extending into the lunules, were observed on many specimens. We interpret these as traces produced by non-lethal triggerfish predation. The traces never extend into the petals, which suggests that bite marks involving petals are more likely to be lethal. There appears to be species selectivity, and traces were more frequent on the flatter sand dollars, Encope michelini (88%) and Mellita tenuis (65%), and rare on Clypeaster subdepressus (21%).

In addition, fossil sand dollars from the Pliocene portion of the Tamiami Formation were examined for marginal traces. Healed traces comparable in morphology to those observed on live-collected specimens were observed on fossils tests of Encope tamiamiensis, Mellita aclinensis, and Clypeaster sunnilandensis, which suggests the presence of non-lethal predation.

An expanded analysis including both recent and fossil echinoids will aid in the recognition of and development of protocols to identify non-lethal predatory traces, and better understand the relationship between the predators causing the traces and their echinoid prey in the fossil record.