Dr. Fűköh Levente szerk.: Malakológiai Tájékoztató 16. (Eger, 1997.)

DÁVID, Á.: Predation by Muricid Gastropods on Late-Oligocene (Egerian) Molluscs Collected from Wind Brickyard, Eger, Hungary

MALAKOLÓGIAI TÁJÉKOZTATÓ MALACOLOGICAL NEWSLETTER 1997 16: 05-12 Prédation by Muricid Gastropods on Late-Oligocene (Egerian) Molluscs Collected from Wind Brickyard, Eger, Hungary Á., Dávid Abstract: Occurrence of Muricid drillholes on the shells of molluscs collected from four different layers of Wind Brickyard (Late-Oligocene /Egerian/) is examined. Mode of life.feeding habit of molluscs, distribution of successful, unsuccessful and unfinished borings have been taken into consideration. Traces of Muricid prédation have been found on the shells of bivalves and gastropods. Number of borings is low on the molluscan shells collected from the Molluscan clay. Encreasing number of borings can be observed in the case of molluscs of the „x" layer and „k" layer. The only layer where the number of unfinished borings is higher than the two other boring types is the „c" layer. Dominantly scavangers and suspensionfeeders have been attacked by the representatives of Muricidae. Keywords: Muricid prédation, molluscs, Late-Oligocene, Wind Brickyard, Hungary 1. Introduction 1.1. Geological background The clay-pit of Wind Brickyard at Eger (Fig. 1) is well-known as the stratotype of the Egerian stage. The lithological sequence of the profde is as follows: - glauconitic, tuffaceous sandstone, - molluscan clay, - layers of marine silty sandstone („x" layer), - layers of marine limonitic sandstone („k" layer), - alternation of coarse sand, carbonaceous clay and a thin gravelly intercalation („c" layer). The above mentioned formations contain molluscan fossills abundantly (Báldi, T. 1973). 1.2. Predatory behaviour of Muricid gastropods Boring activity of predatory gastropods can be traced back until the Lower-Jurassic. There are several families which prey upon shelly animals by hole-drilling. The first appearence of Muricidae were reported from the end of the Lower-Cretaceous. Their holes are easily recognisable in fossil material (Bromley, R. G. 1970, 1981; Carter,R. M. 1968; Hoffman, A. et al. 1974; Sohl, F. 1969; Taylor, J. D. 1970, 1983). Characteristic features of Muricids can be summarized in the following way: - epifaunal animals, - prey on both living and dead organisms, - holes are bored by both mechanical and chemical activity, - drilled holes steep-sided, straight, cylindrical, - do not show preferred sites for boring on prey (Arua, J. 1989).