Some fungi are carnivores: they trap and digest tiny soil worms called nematodes. There are several hundred species of these nematode-trapping fungi, and they show remarkable anatomical, physiological and behavioural-like adaptations.Why trap worms?
Most fungi are saprotrophs, feeding on dead organic matter. Nematode-trapping fungi often live in soil or rotting wood that is poor in nitrogen. Trapping and digesting nematodes provides an extra source of nitrogen and other nutrients.Types of trap (all made from modified hyphae):
• Adhesive networks: Arthrobotrys oligospora forms three-dimensional sticky nets of hyphal loops. A worm that crawls into the net becomes stuck to the adhesive coating.
• Constricting rings: some species, such as Drechslerella (formerly Arthrobotrys) dactyloides, form rings of three cells. When a worm pushes into the ring and touches the inner surface, the three cells swell inwards within a fraction of a second, gripping the worm tightly.
• Adhesive knobs: small sticky knobs on short stalks that attach to a passing worm.Digestion
Once the worm is caught, hyphae penetrate its cuticle and grow through its body, secreting enzymes that digest it. The fungus then absorbs the products.
Efficient trap production
Many of these fungi form large numbers of traps mainly when nematodes are present, detecting chemicals released by the worms. This avoids wasting energy and materials on traps when there is no prey.
Most fungi are saprotrophs, feeding on dead organic matter. Nematode-trapping fungi often live in soil or rotting wood that is poor in nitrogen. Trapping and digesting nematodes provides an extra source of nitrogen and other nutrients.Types of trap (all made from modified hyphae):
• Adhesive networks: Arthrobotrys oligospora forms three-dimensional sticky nets of hyphal loops. A worm that crawls into the net becomes stuck to the adhesive coating.
• Constricting rings: some species, such as Drechslerella (formerly Arthrobotrys) dactyloides, form rings of three cells. When a worm pushes into the ring and touches the inner surface, the three cells swell inwards within a fraction of a second, gripping the worm tightly.
• Adhesive knobs: small sticky knobs on short stalks that attach to a passing worm.Digestion
Once the worm is caught, hyphae penetrate its cuticle and grow through its body, secreting enzymes that digest it. The fungus then absorbs the products.
Efficient trap productionMany of these fungi form large numbers of traps mainly when nematodes are present, detecting chemicals released by the worms. This avoids wasting energy and materials on traps when there is no prey.