Produc. .fungi jl 



ORGANISMS OF THE SOIL VJHICH ATTACK NH'iATODE£ 

 C. L. Duddington 



The suggested title of my paper, "Organisms which attach eelvjorrns in 

 the soil," is for a very ■^^d.de topic. I could not possibly cover so 

 broad a subject here. Actually, I am proposing to deal totally with 

 one group of nematode attacking organisms, the predacious fungi, 

 which are the ones I have been particularly interested in over the 

 last twenty years. 



Predacious f\mgi are to be found, I think I am right in saying, in 

 every group of fungi. The particular ones that I am imierested in 

 are found in two rather widely separated groups. 'One is the Sapro- 

 legniales, which is a group of Phycomycetes fairly closely allied 

 with Mucorales. The other predacious fimgi that I especially want 

 to discuss are found in the Fungi Imperfecti, those fungi which have 

 no sexual reproductive process and which, therefore, cannot be properly 

 classifed. 



These predacious fungi divide into two groups: First, those which 

 capture eelworns alive and consume them, the truly predacious types, 

 such as Arthrobotrys and Dactylella ; and second, those which are 

 internally parasitic, attacking the eelworms usually by means of 

 spores which stick to the cuticle of the eelworm, penetrate it with a 

 germ tube, and so form a mycelium inside the worm. (That type, I 

 suppose, should be described as parasitic, rather than predacious.) 

 Common, too, are the eelworni trapping fungi, which are more important. 

 So, I am going to start by describing some of the ways in which they 

 capture their prey. 



There are two kinds of eelworm traps, the sticky trap and the con- 

 tractile trap. The simplest form of sticky trap is found in the 

 zoopagales, where such genera as Stylopage have mycelium that are 

 sticky all over. If the eelworm come into contact with such a 

 mycelium, at any point, it becomes stuck like a fly on fly paper. 

 That is the least specialized type of eelworm trapj but in the 

 predacious Fungi Imperfecti, much more specialized trapping organs 

 are found. 



The most common and best known type of sticky trap is a sticky network. 

 A hypha on the fungus produces a branch which curls around and joins 

 again. Other hyphal branches form in that way, producing a system of 

 networks with the loops usually standing at right angles to one another, 

 much like the semi-circular canals in the inner ear. Only the networks 

 are sticky, and they appear to be sticky just for eelworms, at least 

 while they are in their normally moist condition. The networks will 

 rot stick to such things as insect cuticle, cuticle of earthworms, and 



