India: Nematodes capture



*Nematodes capture by Arthrobotrys oligospora* KTS 1001 – A nematode hungry fungus.** Sandeepa Inamdar Kanitkar and Ravi. U. Kanitkar Krishi Tantra Sanstha 12, Ganeshwadi Pune 411 004 sankan@vsnl.com March 2003 Arthrobotrys oligospora belongs to a group of nematophagus fungi, which possess specialized structures - in the form of rings, which are extensions of the mycelium to capture, kill and digest nematodes. Arthrobotrys spp have been reported to be present in many suppressive soils. They are usually found in soils with high organic matter content. They are also commonly found in waste mushroom beds. In India, they can be easily isolated from soils near cattle-sheds where the excreta of the animals are collected in a common dump before use. Samples from these sources were collected and plated on Martin’s Rose Bengal agar. Profuse growth of Arthrobotrys was seen in a week in 6 out of 10 samples. After purification, the fungus was grown water agar with Rose Bengal. Profuse ring formation was observed in a week, after which juveniles of Root Knot nematode were introduced in a plate. Daily microscopic observation of the backside of the petri-plate was carried out under low power [10x]. Experiment was carried out in triplicates with control plate containing nematodes only. Daily observation was carried out. The number of nematodes captured and killed was increased from 4^th day and seen up to 8^th day.. Abundant sporulation was observed from the rings, which had trapped and digested nematodes.



It was seen that for the nematode binding to occur, maximum contact with the ring apparatus for a specific period of time was required. The more the nematode was entangled the better it was for the rings to immobilize it. The time of effective contact was noted to be between 1 to 2 minutes. Nematodes, which were entangled at both ends, had a very less chance of escaping the nets. Very fast moving nematodes easily surpassed the nets and tunneled through the ring-nets at ease. Once thoroughly entangled the movement of the nematode became sluggish in 2 to 10 minutes. After 24 hours the nematode was fully utilized and the remains of less than 20% of the body could be seen. The rings, which had previously trapped nematodes and utilized them, were seen in the form of rings, which are extensions of the mycelium as dark colored. The rings, which had earlier trapped nematodes, were ready again to trap new ones once the nematode contents were fully utilized. There was no change in the efficiency as compared to unused rings. 5 days observation showed that 300 nematodes / plate were entangled and killed. After 7 days the number rose to 330. The number of killed nematodes outside the rings was on par with the control plate showing no difference in mortality. Some scientists have reported secretion of nematicidal metabolites in culture. The finding was not replicated over here. This might be due to nutrient deficient medium used to culture A oligospora 1001. Further studies are underway. Below are some photographs of rings of A oilgospora 1001 rings in action

	*1.Profuse sporulation of Arthrobotrys oligospora* 1001 on a trapped and killed root knot nematode**
	*2. Profuse ring production of A oligospora* 1001 in culture**
	3 . Lock tight trap. The nematode is entangled in 3 rings, only two can be seen in this focus
	4. Multipoint contact is necessary for the nematode to stick to establish the fool-proof adhesive contact
	5. Utilization of body contents of nematode by A oligospora 1001 [ 12 hours after the nematode was entangled]
	6. Three dimensional ring. Lactophenol blue staining of A oilgospora 1001 at 45x.

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