Arthrobotrys



Characterized by tall, colourless conidiophores bearing clusters of spores (conidia) at the tip and often at several swollen points below. The conidia are pale, 2- to 3-celled, and leave conspicuous scars on the conidiophore when released.

Species of Arhrobotrys are probably all predators on eelworms (nematodes). They employ several devices to capture these microscopic worms, including (a) constricting rings and (b) sticky networks of loops. Constricting rings work something like the well-known Venus' fly trap. When a nematode, intent upon searching for bacteria and other small edible particles, enters one of the rings, the cells of the ring suddenly inflate and the nematode becomes entrapped. Click here for a link to an excellent web page from the Division of Microbial Ecology, Lund University, partially dealing with nematode parasites. On that page Dr. Dag Ahren has provided a fascinating animated photograph of one of these rings. The constricting action of these rings is so powerful that the nematode is almost cut in half. Sticky networks are less theatrical than constricting rings, yet they have their own brand of terror. When a nematode enters the network of loops it is held by a very strong "glue" and is unable to escape. In both cases, the captured worm first struggles wildly and then seems to become comatose. The fungus then sends its filaments into the worm and digests it. When it has obtained sufficient nutrients from its prey the fungus reproduces by producing clusters of conidia at the tops of long conidiophores.

Arthrobotrys species are common in soil and decaying plant debris. They are undoubtedly important in controlling numbers of nematodes, including those causing damage to agricultural crops. To study them it is necessary to first have a culture of nematodes. We maintain them on a weak medium spread with yeast or bacteria. Pea soup mix also seems to be good food for nematodes. To see Arthrobotrys, a pinch of soil is introduced into the nematode culture. After a few days the traps will become abundant.

Holomorphs: Orbilia. Ref: Haard 1968, van Oorschot, 1985, and Rubner, 1996.