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The effect of water quality on the size and fecundity of Asellus aquaticus (Crustacea:Isopoda)

1981; Elsevier BV; Volume: 1; Issue: 2 Linguagem: Inglês

10.1016/0166-445x(81)90033-3

1879-1514

Mohsen Tolba, D.M. Holdich,

Fish Biology and Ecology Studies

Samples of Asellus aquaticus (L.) were collected from a number of freshwater sites in central England exhibiting either clean, semi-polluted or polluted conditions. The clean sites contained naturally decaying organic matter but the polluted sites also contained sewage and toxicants. The asellids were found to vary in the maximum length attained, and in pereonal width and fresh body weight, in response to water quality. In asellids from polluted sites the body size (length × average pereonal width) and wet weight were significantly lower than those from a clean site. Asellids free semipolluted sites showed an intermediate condition. The number of eggs contained in the marsupia of ovigerous females increases witn body size. However, the actual number of eggs is dependent upon the water quality, there being more eggs in the marsupia of all sizes of ovigerous females from clean sites than those from polluted sites. Asellids from semi-polluted sites showed an intermediate condition. Ovigerous females from polluted sites, kept in clean water, produced F1 generations which, when grown in clean water, showed a significant increase in body size and weight. f1 generation males, derived from clean water females and grown up in clean or polluted water at 20°C, showed a significantly larger increase in width for any given body length in clean water than they did in polluted water. Care must therefore be taken when comparing growth rates of animals from different geographical locations which exhibit different degrees of water quality.