Can fluctuating asymmetry in the swimming crab Ovalipes trimaculatus (Crustacea: Polybiidae) be used as a measure of TBT pollution?

LEZCANO, ANIBAL; ROJAS QUIROGA, MARÍA LAURA; LIBEROFF, ANA LAURA; VAN DER MOLEN, SILVINA

Congreso; XV Congreso Latinoamericano de Ciencias del Mar; 2013

Marine pollution leads to a reduction in developmental homeostasis and individuals inhabiting such conditions may be characterized by morphological alterations and/or poor physiological conditions. The Nuevo Gulf (Patagonia, Argentina) presents an industrial and high marine traffic zone (Puerto Madryn city) with significant and concentrated levels of tributyltin (TBT) pollution. Contrastingly, surrounding areas (~30 Km of coast line) which present scarce human impact are well preserved. Based on the hypothesis that TBT pollution increases the morphological alterations (e.g. asymmetries), the degree of fluctuating asymmetry (FA) in the carapace shape of Ovalipes trimaculatus, were compared by using 2D geometric morphometrics. Additionally, in order to assess the physiological condition of the crabs as well as the carapace composition, the energy density of muscle tissue and the carapace dry weight were analyzed. Sampling included areas with similar environmental characteristics but differing levels of TBT pollution: high (Puerto Madryn harbor), moderate (El Doradillo beach, in the north) and none (Cerro Avanzado beach, in the south). Individuals inhabiting the most polluted site were those showing the highest asymmetry values in carapace shape and the lowest energy density. Nevertheless, carapace dry weight was similar in the three locations. Our results are in accordance with the hypothesis that TBT pollution increase the FA levels and reduce the energy density of crabs. Thus O. trimaculatus may provide a sensitive biological monitor of TBT pollution. The use of FA on carapace shape as a simple, sensitive and cost-effective biomonitoring system for the detection of TBT pollution is discussed.