Predaceous Fungi

From: Christensen (
Date: Sun Jan 03 1999 - 22:49:04 PST

Date: Sun, 3 Jan 1999 23:49:04 -0700
From: "Christensen" <>
Message-Id: <aabcdefg61$foo@default>
Subject: Predaceous Fungi

Among the most highly specialized of the
fungi are the predaceous fungi, which have
developed a number of mechanisms for
capturing small animals they use as food.
Although microscopic fungi with such
habits have been know for many years,
recently it has been learned that a number
of species of gilled fungi also attack and
consume the small roundworms known
as nematodes. The oyster mushroom,
Pleurotus ostreatus, for example, grows
on decaying wood (a, b). Its hyphae secrete
a substance that anesthetizes nematodes,
after which the hyphae envelop and pene-
trate these tiny worms. The fungus appar-
ently uses them primarily as a source of
nitrogen, thus supplementing the low lev-
els of nitrogen that are present in wood.

Some of the microscopic deutero-
mycetes secrete on the surface of their hy-
phae a sticky substance in which passing
protozoa, rotifers, small insects, or other
animals become stuck (c). More than 50
species of this group trap or snare nema-
todes. In the presence of these round-
worms, the fungal hyphae produce loops
that swell rapidly, closing the opening like
a noose when a nematode rubs against its
inner surface. Presumably the stimulation
of the cell wall increases the amount of os-
motically active material in the cell, caus-
ing water to enter the cells and increase
their turgor pressure. The outer wall then
splits, and a previously folded inner wall
expands as the trap closes.

(a)The oyster mushroom, Pleurotus ostreatus.

(b)Hyphae of the oyster mushroom, which
produce a substance that anesthetizes, converg-
ing on the mouth of an immobilized nematode.

(c)The predaceous deuteromycete Arthrobotrys
anchonia has trapped a nematode. The trap
consists of rings, each comprising three cells,
which when triggered swell rapidly to about three
times their original size in 0.1 second and strangle
the nematode. Once the worm has been trapped,
fungal hyphae grow into its body and digest it.


Biology of Plants sixth edition
by Peter H. Raven, Ray F. Evert, Susan E. Eichhorn
W.H. Freeman & Company Worth Publishers
page 333

The letters (a), (b), and (c) refer to three captions.

(a, b) G. L. Barron, University of Guelph
(c) N. Allin and G. L. Barron, University of Guelph

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