Intra and extracellular osmotic regulation in the

Authors: Samuel Coelho de Faria Alessandra Silva Augusto John Campbell McNamara

Publish Date: 2010/10/28

Volume: 181, Issue: 2, Pages: 175-186

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Abstract

We investigate extra and intracellular osmoregulatory capability in two species of hololimnetic Caridea and Anomura Macrobrachium brasiliense a palaemonid shrimp and Aegla franca an aeglid anomuran both restricted to continental waters We also appraise the sharing of physiological characteristics by the hololimnetic Decapoda and their origins and role in the conquest of fresh water Both species survive salinity exposure well While overall hyperosmoregulatory capability is weak in A franca and moderate in M brasiliense both species strongly hyporegulate hemolymph Cl− but not osmolality Muscle total free amino acids FAA increase slowly but markedly in response to the rapid rise in hemolymph osmolality consequent to hyperosmotic challenge 35fold in A franca and 19fold in M brasiliense Glycine taurine arginine alanine and proline constitute ≈85 of muscle FAA pools in fresh water taurine arginine alanine each contribute ≈22 in A franca while glycine predominates 70 in M brasiliense These FAA also show the greatest increases on salinity challenge Muscle FAA titers correlate strongly R = 082 with hemolymph osmolalities across the main decapod sub/infraorders revealing that marine species with high hemolymph osmolalities achieve isosmoticity of the intra and extracellular fluids partly through elevated intracellular FAA concentrations freshwater species show low hemolymph osmolalities and exhibit reduced intracellular FAA titers consistent with isosmoticity at a far lower external osmolality Given the decapod phylogeny adopted here and their multiple independent invasions of fresh water particularly by the Caridea and Anomura our findings suggest that homoplastic strategies underlie osmotic and ionic homeostasis in the extant freshwater DecapodaWe thank Dr Lewis Joel Greene Centro Interdepartamental de Química de Proteínas Hemocentro FMRP USP for kindly providing access to HPLC facilities and Dr Helen J Laure Susie Teixeira Keiko and Danilo César Ament for technical support Research was financed by grants from the Fundação de Amparo à Pesquisa do Estado de São Paulo FAPESP 2007/048709 and Conselho Nacional de Desenvolvimento Científico e Tecnológico CNPq 30417420068 to JCM Animals were collected under IBAMA permit 070/2004 issued by the Instituto Brasileiro do Meio Ambiente e dos Recursos Naturais Renováveis This investigation constitutes part of an undergraduate monograph submitted by SCF to the Department of Biology FFCLRP Universidade de São Paulo USP financed by a PIBIC/CNPq scholarship 117377/20074

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