HYPOBIOSIS IN PARASITIC WORMS 105 



to the normal state. The frog nematodes of the genus Cosmocerca, 

 as well as the land tortoise nematodes of the genus Tachygonethria 

 slow down their physiological processes but remain active. 



Simitch and Petrovitch-^ observed in Yugoslavia, a reaction 

 of parasitic worms in hibernating spermophils CiteUus citellus. 

 These mammals burrow in ground holes in the autumn to spend 

 the whole winter season in sleep; however, they often wake for 

 short intervals. During hibernation, their temperature falls 

 approximately to that of the surroundings, but it returns to 

 normal rapidly on awakening. It appears that parasitic worms 

 vary in their sensitivity to these intermittent falls in temperature 

 and each species is able to tolerate it for a different period. 

 Some worms always die during the hibernation of the host. The 

 acanthocephalan Macracanthorhynchus hinidinaceus proved to 

 be the most sensitive, dying after the shortest period of reduced 

 temperature in the host. This worm is normally a parasite of the 

 pig and is not well adapted to the physiological conditions of the 

 spermophil. The cestode, Hymenolepis nana and the nematodes 

 Streptopharagus kutassi and Trichostrongylus sp. are also not 

 specific parasites of the spermophil, and remain alive for no 

 more than 10 days of continuous hibernation. On the other 

 hand, the cestode Hymenolepis diminiita var. citelli and the 

 acanthocephalan Moniliformis moniliformis can withstand 20 

 days and the nematode Gongylonema longispicula even 30 days 

 of continuous hibernation of the host. Encysted, i.e. resting 

 larvae of two cestode species proved to be the least sensitive as 

 they survived under all conditions. 



Trematode larvae developing in snails may, under certain 

 circumstances, interrupt their physiological activity while their 

 hosts undergo aestivation, i.e. at a relatively high temperature. 

 Barbosa and Coelho-^ demonstrated that the Brasilian water 

 snail, Aiistralorbis glabratus, infected with immature sporocysts 

 of the human parasite. Schistosoma mansoni, is able to survive the 

 dry season in a state of inactivity on the dried bottom mud for 

 prolonged periods. The development of the sporocyst is then 

 interrupted, but is resumed at the start of the rainy season when 



References p. 106 



