Investigation into the Mechanism of Ion Transport in Rio Negro Characiformes

Author

Vineza D. Reduta, University of San DiegoFollow

Date of Award

Spring 5-28-2017

Document Type

Undergraduate Honors Thesis

Degree Name

Bachelor of Arts in Biology

Department

Biology

Advisor

Richard Gonzalez

Abstract

Four fish species within the Characiform Order [(Rosy tetras (Hyphessobrycon rosaceus), Serpae tetras (Hyphessobrycon eques), Emperor tetras (Nematobrycon palmeri) and Penguin tetras (Thayeria obliqua)] are native to the ion-poor, acidic waters of the Rio Negro. In this paper, we focus on Wood’s revised Na⁺/NH₄⁺ exchange model to gain better insight into the mechanisms of ion transport within the Characids. We exposed each species to two experimental treatments: (i) 1mM ammonia (high external ammonia [HEA]), to test coupling of Na⁺ uptake and ammonia excretion, and (ii) 100μM Acetazolamide (carbonic anhydrase inhibitor), to test coupling of Na⁺ uptake and H⁺ excretion. With the HEA treatment, three out of the four species resulted in neither a stimulation nor inhibition of Na⁺ uptake, indicating no loose coupling involved between NH₄⁺ excretion and Na⁺ uptake. As for the Acetazolamide exposure, three out of the four species showed no significant difference in Na⁺ uptake, showing that Na⁺ uptake is not dependent on the protons provided from carbonic anhydrase. Thus, Wood’s Na⁺/ NH₄⁺ exchange model is unsupported in these Characiformes.

Digital USD Citation

Reduta, Vineza D., "Investigation into the Mechanism of Ion Transport in Rio Negro Characiformes" (2017). Undergraduate Honors Theses. 46.
https://digital.sandiego.edu/honors_theses/46