Ingestion of dye by the sexes of Trichostrongylus colubriformis.

Trichostrongylus colubriformis ingested the fluorescent dye, Rhodamine B, while feeding in vivo and in vitro. Ingestion by females of T. colubriformis in vivo significantly exceeded that of males from 15 to 30 days of infection. However, the rate of ingestion declined linearly in both sexes as the helminths' age increased. Uptake of dye in vitro was dependent on time and concentration. Ingestion by the sexes of T. colubriformis in vitro increased significantly with elevated temperature, length of time that the worms were outside the host, decreasing concentrations of salt in the incubation medium and acidic pH's. In vitro ingestion was similar in light or dark conditions. Saturation of the medium with oxygen or nitrogen/carbon dioxide significantly increased or decreased, respectively, ingestion by helminths. Uptake of dye by T. colubriformis decreased significantly in groups when nematodes were increased from 250 to 1,000 worms of a single sex in 2 ml of medium. In females there was a similar decrease in single- or mixed-sex groups containing more than 500 worms while ingestion by males in mixed-sex groups was significantly less than in groups containing only males.