Paper No. 20
Presentation Time: 8:00 AM-6:00 PM
WHO'S ON THE MENU? EXPERIMENTAL ANALYSIS OF PREY SELECTION BY NATICA UNIFASCIATA
DIETL, Gregory P.1, HENDY, Austin, J.W.
2 and ROJAS BRICENO, Alexis
2, (1)Paleontological Research Institution, 1259 Trumansburg Road, Ithaca, NY 14850, (2)Center for Tropical Palaeontology and Archaeology, Smithsonian Tropical Research Institute, Balboa, Ancon, 0843-03092, Panama, gpd3@cornell.edu
Analyses of molluscan death assemblages from the eastern Pacific coastline of Panama indicate that naticid predation is concentrated among particular prey species, regardless of their underlying abundance. One explanation for this observation is that naticid gastropods have a selective feeding behavior. Laboratory experiments were therefore carried out to investigate aspects of prey choice by the locally abundant
Natica unifasciata. One series of experiments (with replacement) tested not only the preference of predators for one of three prey genera (
Iliochione, Protothaca, and
Juliacorbula), but also the consequences of varying prey abundance on their consumption. Prey species were represented by either the same number of individuals (5 specimens) or with varied abundance (species having either 8, 5, or 2 specimens) in each treatment. A second experiment was conducted to determine the sequence by which
Natica selected prey as they depleted each prey resource (without replacement), and included the prey genera
Carditamera, Mactrotoma, Florimetis, Iliochione, Protothaca, and
Juliacorbula.
In simple prey-choice experiments Natica unifasciata overwhelmingly preferred consumption of Protothaca, regardless of abundance. Where all taxa were evenly abundant (5 specimens each per tank) Protothaca would be consumed in ~95% of observations, and even when rare (2 specimens per tank) Protothaca would be the prey consumed in ~85% of cases. The prey sequence experiment (without replacement) showed that Natica consumed Flormimetis earliest, followed by Mactrotoma and Protothaca, with successively less frequent attacks on Iliochione and Carditamera. These results confirm our observations from beach collections, that naticid feeding behavior is highly selective towards particular prey species. Natica unifasciata shows a preference for bivalves of moderate size (<25 mm), with thin shells, and minor surface sculpture. An absence of incomplete drill holes among surviving prey specimens hints that the selection of prey occurs before they are encountered physically, possibly through water-borne chemical cues.
