Combrinck c (5 résultats)

Hardcover. Etat : Good. Good - Bumped and creased book with tears to the extremities, but not affecting the text block, may have remainder mark or previous owner's name - GOOD Standard-sized.

Hardcover. Etat : Brand New. 1st edition. 364 pages. 9.25x6.25x1.00 inches. In Stock.

In the course of an extensive survey of the freshwater snails in the Republic of South Africa, it was noticed that the most commonly occurring species were usually associated with habitats containing a muddy substratum. Two snail species, Bulinus (Bulinus) tropicus Krs. and Lymnaea natalensis Krs. and 5 substratum types were selected. The observations were made in an outdoor river model and in an outdoor aquarium. The criteria chosen for testing the suitability of the substratum were the population statistics, from which ability to increase (rc) was calculated, growth rate and the selecting ability of the snails when given a random choice between the different substratum types. For L. natalensis the succession of rc values on the different substrata were mud, stones, sand, gravel and fine sand but for B. tropicus the only large difference recorded was between the gravel and the other groups. The growth rates on the different substrata for both species parallelled the rc sequence recorded for L. natalensis. B. tropicus appeared to be more dependent on the substratum and to have a better selecting ability. 30 pp., 15 figs, br. 8. …

Etat : New. pp. x + 364.

Etat : New. pp. x + 364 4 Illus.