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Journal of Experimental Biology 56,249-261 (1972)
Published by Company of Biologists 1972

The Evolution of Kidney Function in the Neritacea (Gastropoda, Prosobranchia)

COLIN LITTLE ¹

¹ Department of Zoology, University of Bristol

1. The marine form Nerita fulgurans is unable to osmoregulate, and regulates ions only to a very minor degree. The kidney plays no part in controlling the ionic or osmotic composition of the haemolymph.

2. The freshwater neritid Neritina latissima produces a dilute urine. Salts are removed from the urine by the glandular part of the kidney. The composition of haemolymph in the freshwater Theodoxus fluviatilis has been analysed. It contains surprisingly little calcium.

3. Observations on terrestrial species of Eutrochatella and Alcadia showed that these snails all produce a dilute urine. The site of salt reabsorption is not clear, but the results indicate that it may be reabsorbed by the glandular part of the kidney, the bladder, and also by the mantle epithelium. The haemolymph of the terrestrial species is similar in composition to that of Theodoxus.

4. The renal systems of marine, freshwater and terrestrial neritaceans are compared. Without much gross structural reorganization from the marine species, the Kidney of the freshwater forms have been developed into organs for reabsorbing salts from the urine. The terrestrial species have probably evolved from these freshwater ones, and have retained the production of a dilute urine; this is certainly appropriate because they live in very damp environments.