125 Paleontology V - Predation and Biological Interactions

Monday, 1 November 2010
1:30 PM - 5:30 PM
Room 503

BRACHIOPODS AS ACCEPTABLE PREY: PREDATION ON MODERN AND FOSSIL BRACHIOPODS

Paper number: 125-9
Program: Technical Sessions
Time: 3:30 PM – 3:45 PM

Authors

Abstract

While the post-Paleozoic decline of rhynchonelliform brachiopods may have been due to increased predation during the Mesozoic Marine Revolution, it is also possible that brachiopods may have been undesirable prey. To evaluate rhynchonelliform brachiopods as acceptable prey, we combine modern experimental data with Phanerozoic data on predation traces. Modern experiments conducted on San Juan Island consisted of 26 feeding trials offering terebratulides and bivalves to multiple species of predators (crabs, seastars, and gastropods). In addition, local terebratulide populations were inspected for the presence of repair scars to estimate the frequency of durophagous predation. The Phanerozoic record of predation was also examined using predation traces (drill holes and repair scars), a common proxy for predation intensity. Based on a comprehensive examination of the literature, a database recording drilling and repair scar frequencies was assembled based on the following criteria: 1) trace frequencies listed at the species level, 2) raw numerical data reported, 3) interpretation of traces as predatory in origin, and 4) minimum sample size of n=10.

Of the 132 brachiopods offered to predators in the laboratory, 37% were consumed, including successful ingestion by all three groups of predators employed. In addition, the repair frequency of samples acquired from local Terebratalia populations was 29% (n=178). Concurrently, examination of the literature on fossil predation traces demonstrated an extensive record of attacks on Cambrian to Recent rhynchonelliform brachiopods. Trace frequency is high throughout the Paleozoic (reaching 55%), sparse during the Mesozoic, and high again in the Cenozoic.

The consumption of modern brachiopods by multiple species of invertebrate predators in the laboratory and the observed high repair scar frequency suggest that predation pressure on modern brachiopods is substantial. The pervasive presence of predation traces in fossil brachiopods (scarcity of Mesozoic traces may reflect a decrease in predation or dearth of Mesozoic studies) reaffirms the experimental results on modern brachiopods. Predation may have played a role in the post-Paleozoic decline of brachiopods, including their shift to cryptic habitats and other refugia.