Age and growth variability of the yellow clam Mesodesma mactroides Reeve, 1854 in two populations of Argentina: Implications under climate change

Abstract

Morphometric relationships, age and growth rates of the yellow clam Mesodesma mactroides Reeve, 1854 were compared in two populations of Argentina: Santa Teresita (36°32´00"S) and Mar del Plata (37°57´52"S). Santa Teresita´s clams were heavier (shell, soft parts) than Mar del Plata ones. Mutveis-stained cross-sections and acetate peels revealed an internal shell growth pattern of well-defined slow-growing translucent bands and alternating fast-growing opaque bands. Translucent bands (clusters) representing external rings were formed mostly during October in both sites, coinciding with gonadal maturation processes and spawning. Data confirm the annual formation of translucent bands in this species. Comparison of growth parameters showed a higher growth rate k and lower maximum age in Mar del Plata (8 yr.) than Santa Teresita (9 yr.), which could be triggered by differences in salinity between localities due to the influence of the Rio de la Plata estuary, strongly linked to climate variability. Shell mass condition index and Oceanic Niño Index were negatively correlated, showing the influence of El Niño in shell properties of the species. Considering the events are becoming more intense and frequent, changes in growth rates and shell properties of Santa Teresita's population could be expected to be more vulnerable under climate change.