VERTICAL MIGRATION OF TRICHOSTRONGYLID LARVAE ON GRASSES.

摘要: Experiments were conducted in the laboratory to investigate ability of trichostrongylid larvae migrate vertically on various grasses under controlled environments. Only a small proportion, 2 3%, given opportunity ascend grass blades, conditions considered favorable for migration, climbed. Of these, 59.2, 26.7, 9.9, 3.4, and 0.8% found 1st-, 2nd-, 3rd-, 4th-, above 5th-inch height level from soil, respectively. It was concluded that though infective can climb grasses, greatest portion remain at base vegetation. The comparatively more successful tall fescue than smooth brome. external morphology apparently influences migration larvae. A film moisture is obviously advantageous migration. On an average 0.65% test climbed wetted blades while only 0.04% unwetted blades. Upward favored by higher relative humidity. 1.36% 95% humidity 0.06% 56% Lower temperature adversely affected upward 0.13% 40 F 2.54% did so 79 80 F. direct influence light intensity not clearly established since darkness essentially similar. Taylor (1938), Rogers (1940), Kauzal (1941), Dinaburg (1944), Crofton (1948), Rees (1950) studied vertical herbage. Their techniques involved placement known numbers larvae, contained volume water, soil herbage experimental plots field or laboratory. Subsequent recovery interpreted indicate surface onto However, except (1948) (1950), most these investigators establish actual ascended. Furthermore, few cases (Crofton, 1948; Rees, 1950; Rogers, 1940) correlated with environmental factors. present study undertaken order obtain extensive series observations Received publication 20 August 1963. * From Department Veterinary Science, Paper N.S. 400, approval Director, Wis. Agr. Exp. Sta., supported part University Research Committee. as well population which does migrate, observe factors including moisture, temperature, humidity, light, type grass, number available upon movement MATERIALS AND METHODS studies obtained "seed" calves primarily infected Haemonchus placei minor populations Cooperia onchophora Trichostrongylus colubriformis. cultured sterilized sphagnum according method Cauthen (1940) recovered using Baermann funnels. Differential counts made individual tests, therefore, have been referred trichostrongylid. 7 days old when used but trial all same age. Grass grown seeds planted silt muck paper pots. soils render them free nematode life prior tests. seedlings emerged tuft 3 inches tall. Numbers estimated dilution counts. By restriction suspension, quantity could be placed position