Sledovi predacije na lupinah miocenskih polžev in školjk pri Dolenjem Mokrem Polju

Geološko podlago njiv in travnikov v okolici Dolenjega Mokrega Polja tvorijo srednjemiocenski (badenijski) laporasti apnenci. Po vsakem oranju teh njiv se na površju zbirajo hišice ter kamena jedra polžev in školjk. Na nekaterih vrstah fosilov smo opazili sledove predacije (izvrtine), zato smo se odločili, da le te podrobneje raziščemo in na podlagi njihove oblike skušamo določiti povzročitelja. Zanimala nas je tudi pogostnost navrtanih lupin. Poudarek raziskave je predvsem na polžjih hišicah turitel. V okviru diplomske naloge sem pregledala dve njivi: prva (lokacija A) meri 20 m2, druga (lokacija B) pa 52,5 m2 . S površine sem sistematično pobrala vse fosilne polžje in školjčne lupine ter njihova kamena jedra. Na lokaciji B sem večjo pozornost namenila pobiranju čim bolj celih hišic turitel, na katerih sem kasneje določevala mesto izvrtin na hišicah. Vrstno sestavo združbe sem določila s primerjavo favne v zbirki Prirodoslovnega muzeja Slovenije. Določila sem 12 različnih vrst, najpogostejša med njimi pa je Turritella turris. Za določanje vrst plenilcev sem izbrane primerke pregledala na vrstičnem elektronskem mikroskopu. Na koncu sem dobljene rezultate primerjala s položajem in obliko izvrtin pri recentnih turitelah. Ugotovila sem, da so bili najpogostejši plenilci turitel naticidni polži, del izvrtin pa pripada tudi muricidam, čeprav fosilnih ostankov le-teh na terenu nisem našla. Najpogosteje je navrtan osrednji del hišice, in sicer med četrtim in sedmim zavojem. Prav tako so tudi recentne turitele večinoma navrtane na osrednjem delu lupine. V primerjavi z recentnimi turitelami so razlike vidne v debelini lupine, v velikosti hišic ter reliefu lupine. Fields and meadows around Dolenje Mokro Polje are underlain by the Middle Miocene (Badenian) marly limestones. After annular plowing of the fields, shells and casts of fossil gastropods and bivalves, originating from these marly limestones, come to the surface. In some specimens are observed traces of predation (boreholes), that were decided to be explored more detail and based on their shape tried to determine the predator. We also documented the abundance of the drilled shells. The focus of the research is on the gastropod Turritella. As part of the diploma thesis, two fields were examined the first (locality A) is 20 m2 large, the second (locality B), measures 52.5 m2. From the area A, all fossil shells and their casts were systematically collected. At the locality B, the emphasis has been on collecting unfragmented (or less fragmented) shells of the gastropod genus Turritella. The species composition of the assemblage was determined by comparison with material stored at the Slovenian Museum of Natural History. Twelve different species were determined, the most common among them is Turritella turris. Some selected specimens were examined to determine the possible predators by observing the boreholes under the Scanning Electron Microscope. Finally, the obtained results were compared with the position and shape of the boreholes in recent Turritella. The most common predators of turritellids are the naticid gastropods, but some borings also belong to muricids, although no fossil muricids have been found at neither of the localities. The most common drilling position is in the central part of the shell, between the fourth and the seventh whorl. Similar, also recent turritellids are mostly drilled in the central part of the shell. Compared with the recent turritellids, there are clear differences in the thickness, size and the relief of the shell.