Predation traces on clams (Bivalvia: Veneridae) from the eocene of Antarctica

• Autores: Romero, María; Palópolo, Evangelina; Brezina, Soledad; Casadio, Silvio Alberto; Santillana, Sergio
• Año de publicación: 2023
• Idioma: inglés
• Tipo de recurso: documento de conferencia
• Materia: Ciencias Exactas y Naturales; predation traces; eocene; antarctica; Ciencias Exactas y Naturales
• Institución: Universidad Nacional de Río Negro

Fil: Romero, María. Estación costera J. J. Nágera, Instituto de Investigaciones Marinas y Costeras (IIMyC, CONICETUNMdP). Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET). Argentina.
Fil: Palópolo, Evangelina. Instituto de Investigación en Paleobiología y Geología (IIPG, CONICET-UNRN). Argentina.
Fil: Brezina, Soledad. Instituto de Investigación en Paleobiología y Geología (IIPG, CONICET-UNRN). Argentina.
Fil: Casadio, Silvio. Instituto de Investigación en Paleobiología y Geología (IIPG, CONICET-UNRN). Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET). Argentina.
Fil: Santillana, Sergio. Instituto Antártico Argentino. Argentina.
This study presents a metric analysis of predator-prey relationships based on venerid species of Subfamily Tapetinae from the La Meseta Formation (Eocene) of the Antarctic Peninsula. The two main components of assemblages were Adelfia omega and Katelysia florentinoi. The topmost marine layers of the James Ross Basin are represented by two sites (A: 64° 14’ 28.78” S; 56° 38’ 43.19” W; B: 64° 14’ 30.39” S; 56° 38’ 44.53” W), from which 871 specimens (IAA-Pi-338/342, n= 811; IAA-Pi-360, n= 60) were randomly selected. In 95 % of the cases, venerids had articulated valves, a moderate-high dissolution degree and an intermediate level of compaction deformation. Drill holes were assigned to Oichnus paraboloides. The height of each venerid specimen and the outer diameter of boreholes were measured. The following proportions were calculated to perform a drilling frequency analysis: attack and drilling frequency, success rate, and prey effectiveness. Non-parametric analysis was used to test differences between samples. A linear correlation between valve height and hole outer diameter was calculated to determine if both variables have a linear relation. The specimens with intermediate valve height values (mean= 28.29; median= 28.28; range= [12; 45]) had the highest drilling and attack rates, which were around 24 % in both cases. Drilling frequencies (9 % and 3 %, respectively) in specimens with the lowest valve height values (mean=25.74; median=26.19; range= [10; 41]) and the highest valve height values (mean= 35.69; median= 35.76; range= [26; 59]) were similar to those previously reported for the Eocene of La Meseta Formation and other localities. Attack frequencies were lower in specimens with the highest and lowest valve height values (6 % and 9 %, respectively) than those found in other investigations from the top of the La Meseta Formation. In specimens with intermediate and low valve height values, the success rate was almost 90 %. Prey effectiveness (i.e., relative frequency of failed attacks) is very low in all cases. No significant differences in the predator size were observed (p-value= 0.5360). Individuals of intermediate size from site A had the greatest attack and drilling frequency rates, which may indicate that predation pressure was greater there. The size of the prey and the outside diameter of the borehole do not strongly correlate. Prey and specimen size appear to have a nonlinear relationship. Predators mostly prey on intermediate sizes (12-45 mm). According to previous studies, it is plausible that predators choose an optimal prey.