Author

Irwin Beitch

Date of Award

Summer 1962

Document Type

Thesis

Degree Name

Master of Science

Department

Biology

Abstract

The urinary systems of Roccus saxatilis (Walbaum) and Roccus Americanus (Gmelin) were studied to check the validity of the monogeneric classification and to examine the osmoregulatory mechanism that allows the species to survive in environments of various salinities. The gross anatomy of the urinary systems of 13 R saxatilis and 12 R. americanus showed a number of similarities to exist, e.g. the general mesonephric form and size, uretal position and length, and the renal venous system. The head kidney, a hemopoietic organ, was larger in R. ­saxatilis than in R. americanus. Histological comparisons were made of H and E serial sections of the posterior part of the kidneys, and of the ureter, from three R. saxatilis and four R. americanus; included were the entire kidneys of two 2-year-old males of each species. The kidney of a young specimen of each species was also studied. The lomeruli in R. americanus were found to be larger than those R. saxatilis; however, in a previous study, freshwater R. saxatilis were shown to have glomeruli of intermediate size. The number of goblet cells in the anterior part of the ureter was greater in g. saxatilis and may be correlated with glomerular size. A dis­tal tubular segment, usually present in freshwater fishes, was absent in both species; probably a reflection of their marine origin.

As the differences in the urinary system were explained on the basis of selective adaptation, they, and the number of similarities, were considered to support a monogeneric classification.

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