Give me hard substrates! Biotic interactions between Danian serpulids and oysters from Patagonia

BREZINA S.S.; ROMERO, M.V.; CASADÍO, S.

GENERAL ROCA

Congreso; 11° CONGRESO DE LA ASOCIACIÓN PALEONTOLÓGICA ARGENTINA; 2016

Many works on recent and fossil oysters as hard substrates have shown characteristicdistribution patterns of sclerobiotic assemblages and also biotic relationships ascommensalism, parasitism, overgrowth, among others. This information can be useful to reconstruct life habits of extinct fossil organisms and biotic interactions if they were infested during their lifetime. The aim of this work is to assess possible paleoecological relationships among serpulid worms and Pycnodonte (Phygrea) burckhrdti (Böhm, 1903), an early danian oyster included in mudstones beds of Jagüel Formation, in General Roca locality. A total of 189 oysters were analyzed (60 left, 24 right, and 115 articulated specimens) and the presence/ absence of serpulids on the valves were registered. Statistical analysis (i.e., goodness of fit test and exact confidence intervals for the binomial distribution) were performed in order toassess possible preference of serpulids for different areas of the valves. Results showed a differential settlement of tube worms in the external margins of both valves. These uncovered areas could have placed a few milimeters above the sediment-water interface. In coincidence with life position of recent gryphaeid oysters, the margins of both valves of P. (Ph.) burckhardti would have a better exposure to colonization during the life of the oyster. Inhalant currents generated by oysters or suspended debris generated by the motion of the surrounding water could have fed serpulids. In conclusion, a biotic interaction among serpulids and oysters is suggested by the distribution pattern of the serpulids on the margins of the of P. (Ph.) burckhardti.