Honors College Theses

Publication Date



Biology (B.S.B.)

Document Type and Release Option

Thesis (restricted to Georgia Southern)

Faculty Mentor

Christopher Cutler


The American eel, Anguilla rostrata, is a special teleost fish species that can acclimate to both fresh and seawater during its lifetime. Such plasticity is due to specialized osmoregulatory processes that exist for each environment, maintained partly due to the presence of water channels called aquaporins (AQP). AQP 1aa, 1ab, 4b2, 8ab and 10b2 all play roles in the modulation of water levels in urine, that occurs within nephrons of the eel kidney, a major site for fluid filtration, secretion, and reabsorption. Previously, the location of the aquaporins had not been determined because the various nephron sections were indistinguishable. However, as cilia are only found in the proximal portions of seawater eel renal nephrons, AQP proteins could be localized to nephron segments in conjunction with the presence or absence of cilia stained with a fluorescent anti-tubulin antibody. A similar immunohistochemical technique was also used to localize the AQP proteins. Results show that AQP1aa is found in the early proximal tubule, AQP1ab at the junction of the proximal and distal tubules, AQP4b2 was widely distributed in the proximal and distal tubules, and collecting ducts. Furthermore, AQP8ab was mainly located in the distal tubule, with low levels in the collecting duct and AQP10b2 was found at the end of the distal tubule and in the collecting duct. The results suggest that AQP1aa, 1ab and 4b2 are involved in fluid secretion in the proximal tubule and AQP1ab, 4b2, 8ab and 10b2 are involved in fluid reabsorption in the distal tubule/collecting duct.