Marine brachyuran crabs’ osmoregulatory and metabolic responses upon warming and seawater dilution challenges: the non-native Charybdis helleri is more sensitive than the native Menippe nodifrons.

The presence of non-native organisms challenges ecosystems under the influence of climate change. Comparisons of physiological performance between ecologically-similar native and non-native species contribute to invasion studies. We examined two decapod crustaceans in Estuarine Complex of Paranaguá (ECP), Brazil: the non-native Charybdis hellerii and the native Menippe nodifrons. Crabs were acclimated to control (26 °C) and elevated (30 °C) temperatures for one week in full-strength seawater (35‰), and were then submitted to dilute seawater (30, 25, and 20‰) for 6 hours. Hemolymph was assayed for osmolality, chloride, magnesium, and lactate; muscle samples were evaluated for hydration levels. Dissolved oxygen and ammonia production were assessed in the experimental water. Both species were impacted by low salinity, with an synergistic effect from elevated temperatures. However, C. hellerii was more affected than M. nodifrons, displaying less capacity to keep stable muscle hydration levels upon seawater dilution, a steeper decrease in dissolved oxygen, higher ammonia excretion, and higher lactate, as compared to the native crab. The non-native C. hellerii was physiologically challenged to a much higher degree than the native species. Although C. hellerii has established populations in the ECP, its sensitivity (synergistic deleterious effect) to salinity reductions and rising temperatures may limit its further spread in areas with intense fluctuating abiotic conditions. These data can support modelling efforts of the trends in these species distribution where C. helleri is invasive. This result may also be indicative of the undergoing process of invasion; similar approaches could contribute to invasion science involving other marine/estuarine crabs.