engleski

Anaerobic potential of Synurella ambulans (Müller, 1846) (Crustacea, Amphipoda) from hyporheic zone of Sava River and Stalnjak Spring, Croatia

The hyporheic zone (HZ), a subterranean/surface water transitional interface, is a complex shallow interstitial groundwater flow system situated lateral and beneath a stream. HZs belong to the most threatened aquatic environments. The extreme characteristics of the HZs, including dynamic and highly heterogeneous hydrologic and biochemical processes, small physical size and exchange flow, and full darkness, cause higher concentration of major ions and metals and unpredictable changes in the rate of dissolved oxygen. To cope with oxygen deprivation, subterranean organisms have evolved different strategies such as reduced metabolism [1], high amounts of stored glycogen and phosphagen arginine phosphate [2] and utilization of anaerobic routes. [3] In this study, the activities of three enzymes involved in energy metabolism were measured in small stygophilous amphipod Synurella ambulans to assess its anaerobic potential. Specimens were sampled from two localities: the HZ of the Sava River (Zagreb, Jarun) and acid springbrook Stalnjak (Zaprešić). The data on metabolic enzyme activity of this species are lacking since this amphipod species hasn’t been intensively investigated. The ratio of pyruvate kinase (PK) over phosphoenolpyruvate carboxykinase (PEPCK) activities was used as an index of aerobic relative to anaerobic capacity of an animal, and lactate dehydrogenase (LDH) activity as an indicator of anaerobic glycolytic potential. Stalnjak population had lower PK/PEPCK ratio and lower LDH activity than population at the Sava River indicative of higher dependence on anaerobic pathways compared with the population from the Sava River HZ. PK/PEPCK ratio in S. ambulans was ~2- 3-fold higher compared with the published values for two other stygobiont species (Niphargus virei and Niphargus rhenorhodanensis), but ~6-fold lower than in an epigean species Gammarus fossarum (Hervant, 1997). LDH activity in S. ambulans was similar to that of N. rhenorhodanensis and N. virei. Overall, relatively low PK/PEPCK ratio and high LDH activity indicate increased anaerobic potential of S. ambulans and its ability to tolerate low oxygen concentrations underground.

hyporheic zone ; energy metabolism ; pyruvate kinase, phosphoenolpyruvate carboxykinase ; lactate dehydrogenase

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