Osmotic relationships in a freshwater mussel, Hyridella menziesi Gray (Lamellibranchia: Unionidae)

Key metabolites in tissue extracts of Elliptio complanata identified using (1)H nuclear magnetic resonance spectroscopy

We used (1)H nuclear magnetic resonance spectroscopy to describe key metabolites of the polar metabolome of the freshwater mussel, Elliptio complanata. Principal components analysis documented variability across tissue types and river of origin in mussels collected from two rivers in North Carolina (USA). Muscle, digestive gland, mantle and gill tissues yielded identifiable but overlapping metabolic profiles. Variation in digestive gland metabolic profiles between the two mussel collection sites was characterized by differences in mono- and disaccharides. Variation in mantle tissue metabolomes appeared to be associated with sex. Nuclear magnetic resonance spectroscopy is a sensitive means to detect metabolites in the tissues of E. complanata and holds promise as a tool for the investigation of freshwater mussel health and physiology.

Amino acids in haemolymph, single fibres and whole muscle from the claw of freshwater crayfish acclimated to different osmotic environments

The concentrations of free amino acids were measured in whole claw muscle, single fibres and haemolymph of Australian freshwater crayfish, Cherax destructor, during the intermoult stage. The average total pool of amino acids in short-sarcomere fibres (179 mmol kg(-1)) was 60% greater than in long-sarcomere fibres, due to higher concentrations of alanine, cysteine, glutamate, leucine and proline. The two fibre types exhibited differences in the banding pattern of the isoforms of troponin using gel electrophoresis. The average pool of amino acids in haemolymph was 2.7 mmol kg(-1). Cherax has symmetrical claws and the total pool of amino acids from whole muscles (approx. 79 mmol kg(-1)) was similar in left and right claw muscles. In animals acclimated to osmotic environments between 0 and 220 mOsm, the osmotic pressure of the haemolymph increased from 356 to 496 mOsm, but no systematic changes were observed in the amino acid profiles of muscles or haemolymph. The major findings were that (a) concentrations of amino acids differed between the two major fibre types in claw muscle and (b) amino acids in the muscle fibres did not play a major part in intracellular osmoregulation in Cherax, suggesting this species is an anisosmotic regulator.