100 G. WITENBERG 



dehydrated state. When moistened they absorb water and 

 regain their normal shape and movement {Nematodirus sp., 

 etc.). 



Not all species of nematodes and also not all stages of the same 

 nematode have the same capacity to withstand dehydration. 

 ZavadovskyS has shown that very young Trichostrongylid larvae 

 cannot withstand dehydration, while five-day old ensheathed 

 infective stages remain viable when dehydrated for two months 

 (at 22°). On the other hand, infective larvae of the notorious 

 stomach nematode of the sheep, Haemonchus contortus, perish 

 rapidly when desiccated^. 



Some larvae of nematodes parasitic in plants have remarkable 

 capacity to withstand desiccation. Steiner and Albin^^ recorded 

 reviviscence of desiccated specimens of Anguina tritici after 28 

 years and of Tylenchus polyhypnus (m.ature young females and 

 larvae) after 39 years quiescence in herbarium specimens^^. It 

 should be noted that the observation of the revival of dehydrated 

 Anguina tritici (formerly called Anguinulina) was made as early 

 as in 1743 by Needham, and is one of the earliest records of a 

 cryptobiotic phenomenon. 



Free living nematodes usually show no dormancy during their 

 life cycle. There are, however, coprophagous species which 

 develop a so-called stage of persisting larvae ('Dauerlarve' of 

 Fuchs^'"): when the larvae have consumed all available food they 

 become transformed into a persisting stage which differs slightly 

 morphologically from normal larvae. They are m^ore slender and 

 sluggish and withstand starvation. When food again becomes 

 available they start feeding and develop along normal lines. In 

 some species of the genus Diplogaster which belong to the above 

 mentioned group, the persisting larvae crawl onto passing dung 

 beetles, hide under their elyirae and are transported to a new 

 place of abundant food. They may rest in a dormant state for 

 long periods on this living transport. 



Larvae of another nematode of this group, Rhabditis coarctata, 

 build special elongated capsules glued to the exoskeleton of the 

 dung beetles, and are carried in them until the beetle comes to a 



