Osmotic regulation of the amphipod Gammarus chevreuxi (Sexton, 1912)

Sam Houston

Abstract


This study investigated osmotic regulation in the amphipod, Gammarus chevreuxi, and is the first publication of this organism’s osmotic regulatory curves.  Unlike most estuarine amphipods studied to date which are hyperosmotic regulators, G. chevreuxi is a hyper-hyposmotic regulator. The hyperosmotic gradient maintained by G. chevreuxi in dilute media is very low (~120mmol.L-1), which has been interpreted as evidence of freshwater ancestry among the Crustacea. Salinity acclimation did not appear to affect heart rate or pleopod beat frequency. The gill cells responsible for ion uptake appeared to be smaller in high salinities or distorted. The apical membrane in concentrated media shows signs of damage beneath the cuticle. These findings demonstrate strong osmoregulatory ability in G. chevreuxi and suggest descent from a freshwater lineage of amphipods.

 

Keywords: osmoregulation, ion regulation, Gammarus chevreuxi, gill ultrastructure, haemolymph, sodium, calcium, magnesium, salinity acclimation, heart rate


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