The spinose shells of the sessile, epifaunal bivalve Arcinella cornuta, from the fossiliferous Pliocene Pinecrest and Caloosahatchee beds of Florida, provide evidence of ecological interactions with both boring predatory gastropods and commensal bivalves. The number, sizes, and positions of borings in A. cornuta were compared to parameters such as size of the valve and density of spines at the boring site to determine to what extent spines influenced the borers. Records of attacks by naticid and muricid gastropods are preserved as borings in the shells of their putative prey. Gastropods can exhibit stereotyped attack patterns and can be highly selective with regard to prey size and boring site in order to optimize net energy return. Although some site and size selectivity was evident, attack strategies toward A. cornuta shifted over time. Spine density at boring sites was negatively correlated with boring frequency, demonstrating that spines hindered predatory attacks. Smaller predators were selective and most often bored at the thinner posterior region of the shell. Larger predators were less selective and most often bored at the lunule; the thickest portion of the shell, but the only area unobstructed by spines. Larger predators apparently accepted longer boring times in order to increase chances at success. Over time, establishing two preferred boring sites enabled predators to optimize their attacks. This direct link between prey morphology and predator adaptation signals that an arms race between these two species may have been underway.
A. cornuta shells were also the preferred habitat of boring gastrochaenid bivalves, signaling a shift in the borer's habitat. Some species of the bivalve family Gastrochaenidae dwell in semiendolithic boreholes partially covered by secreted calcareous envelopes or crypts. Gastrochaenids selectively colonized shells of A. cornuta to exploit the feeding currents, armor, and raw materials provided by the host. The distribution of borings and crypts indicates that gastrochaenids colonized and grew within the spines of A. cornuta, orienting their siphons to exploit feeding currents created by the host. As the gastrochaenids matured and outgrew the space available within the spines, they incorporated them into their crypts.
| Identifer | oai:union.ndltd.org:PITT/oai:PITTETD:etd-05062003-191127 |
| Date | 23 May 2003 |
| Creators | Beatty, William Lee |
| Contributors | Harold Rollins, Edward Lidiak, Thomas Anderson, Rosemary Capo, Lance Lugar, Jeffrey Schwartz |
| Publisher | University of Pittsburgh |
| Source Sets | University of Pittsburgh |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.library.pitt.edu:80/ETD/available/etd-05062003-191127/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to University of Pittsburgh or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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