Nematode-trapping fungi constitute a guild of species that develop specialized trapping structures with which they capture and digest nematodes. These traps are not constitutively present, but instead develop in the presence of nematodes3; they attract them2, adhere to their cuticle and eventually pierce it, extending hyphae inside their bodies.
Due to the fact that many nematode species behave as pests and diseases, groups of fungi with nematode-antagonistic effects are interesting due to their potential uses in biocontrol1,4. Here we describe the progression of the nematode-trapping process by Arthrobotrys oligospora Fres. (Helotiales: Orbiliaceae) (isolate INTA10, obtained from soil of an organic tomato farm in La Plata area, Argentina [S 35°06′ W 58°12′]) on the free-living nematode Panagrellus redivivus Linn. (Rhabditidae: Panagrolaimidae).
INTA10 was grown on 90×15mm oatmeal agar culture plates in the dark at 24±1°C until the plate was covered (72h). Twelve plates were prepared. Approximately 5000 nematodes were inoculated on each plate, and dispersed freely across the culture. Every 6h after nematode inoculation (t=6, 12, 18, and 24) three cultures were stained using methylene blue (0.1% w/v) and immediately rinsed with sterile physiological solution, while the remainder of the cultures was allowed to continue its development. Stained cultures were examined using a compound microscope (Leica, DM E) to observe trapping progression (Fig. 1). Developed traps (indicated with arrows, Fig. 1A) with alive, recently caught nematodes were found at t=6. Fungal colonization inside the nematodes was detected at t=24, with the presence of blue-dyed hyphae growing inside them (indicated with arrows in Fig. 1B, shown magnified in Fig. 1C). Figure 1D shows the multicellular, tridimensional adhesive traps stemming from the mycelium in further detail.
The work was funded by PE INTA PNPV 1135033.
DS holds a research career award from Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET).
