Abstract
Vertical glass tubes, with various portions blackened, were illuminated by a horizontal beam of white light to determine the photoresponse and georesponse of miracidia and cercariae.Four-arm test chambers were used to determine the lowest light intensity at which miracidia and cercariae showed a phototactic response. This intensity (.0.35 lx) was the same for miracidia and cercariae even though miracidia, whose next host is a bottom-dwelling clam (Pisidium casertanum), are photonegative, and cercariae, with a bottom-dwelling caddisfly larva (Limnephilus sp.) as next host, are photopositive.Two-arm test chambers, illuminated with monochromatic light, were used to determine the wavelengths to which the larval stages were responding. Cercariae showed a single response peak at 550 nm while miracidia showed two peaks, one at 550 nm and the other at 650 nm. The second peak may be a result of a screening effect by the pigment which surrounds the photoreceptor.Miracidia showed a positive georesponse when tested in vertical test tubes. However, the negative photoresponse determined their distribution in a conflicting situation. No conclusive results were obtained when the georesponse of cercariae was tested. These larvae remained on the bottom of test chambers under all conditions.
Publisher
Canadian Science Publishing
Subject
Animal Science and Zoology,Ecology, Evolution, Behavior and Systematics
Cited by
12 articles.
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