Spatial microhabitat selection by Biomphalaria pfeifferi in a small perennial river in Tanzania
Utzinger, Jürg ; Mayombana, Charles ; Smith, Tom ; Tanner, Marcel
In: Hydrobiologia, 1997, vol. 356, no. 1-3, p. 53-60
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- A study was carried out in the Mlali river in south-central Tanzania with two aims. First, to determine microhabitat availability in two sites (A and B) with respect to water depth, water velocity and dominant substratum type. Second, to assess microhabitat use by Biomphalaria pfeifferi, the intermediate host snail of intestinal schistosomiasis and to investigate whether these snails show preferences for certain microhabitats. The two sites differed significantly with respect to width, water depth, water velocity and substratum composition. It is suggested that the absence of B. pfeifferi from site B is mainly associated with the high water velocities at that site, where 62% of the measurements exceeded30 cm s-1. In site A, the microhabitat use by 327 B. pfeifferi snails was assessed by means of direct observation. No significant relationships were found between snail size and the habitat variables investigated, indicating that snail size appeared to be of no importance in spatial microhabitat selection. B. pfeifferi snails showed statistically significant preferences for shallow water (depth: 2-7 cm) and the preferred water velocities ranged between 12 and 21 cm s-1 with an estimated optimum at13.3 cm s-1. No statistically significant preferences for substratum type were found