Comparison of oxygen consumption of three freshwater amphipods, Gammarus loeffleri, G. crinicaudatus, and G. zagrosensis in different salinities

Respiration and oxygen consumption in aquatic invertebrates including Gammarus (Crustacea: Amphipoda) are affected by osmotic pressure and salinity. This effect was investigated in three species from ecologically different springs in Fars Province. Oxygen consumption was measured for 1 hour period in various salinities (2 - 10 ppt) using a dissolved oxygen probe. Results showed significant differences in oxygen consumption in salinities 4 - 10 ppt. Oxygen consumption in all three species increased from salinity 2 - 6 ppt, and decreased with increasing salinity to 8 - 10 ppt. It was also significantly higher in salinities of 6 - 8 ppt in G. crinicaudatus, compared to other species. Regarding salinity differences in the environments of these species, it can be said that G. crinicaudatus has more tolerance and adaptability to salinity increase compared to the other two species. The higher oxygen consumption suggests that 6 ppt salinity was critical for all the three species. These three species have probably derived from a common ancestor diverging in time after geographical isolation of its descendant populations. The difference in their physiological responses could be a reflection of adaptation pressures, particularly osmotic conditions of their environments.