Cockroache; Ecology, behavior & history - W.J. Bell

ing cockroach Cryptocercus. An average of 234 microbial
colony-forming units/cm 2 cuticle have been detected on
C. punctulatus (Rosengaus et al., 2003), and the insects are
known to allogroom, using their mouthparts to directly
graze the cuticular surface of conspecifics.Young nymphs
spend 8% of their time in mutual grooming (Fig. 5.5B)
and 15–20% of their time grooming adults. Grooming
decreases with increasing age, and allogrooming was
never observed in adults (Seelinger and Seelinger, 1983).
Grooming has a number of important functions, and
high levels of autogrooming may be related primarily
to the prevention of cuticular pathogenesis in their
microbe-saturated habitats. Digestion of some of the
gleaned bacteria may be an auxiliary benefit, particularly
if resident gut bacteria play a role in neutralizing ingested
pathogens. Intense allogrooming in developmental stages
with high nutrient requirements is suggestive that there
may be a nutritional reward for the groomer, in the form
of microbes, cuticular waxes, or other secretions. Starvation
is known to increase grooming interactions in termites
(Dhanarajan, 1978), and the observation that
young Cryptocercus nymphs spend up to a fifth of their
time grooming the heavily sclerotized adults, presumably
the most pathogen-resistant stage, further supports this
hypothesis. However, young nymphs also may be acquiring
antimicrobials or other non-nutritive beneficial substances
from adults during grooming, and keeping nest
mates free of infection is in the best interest of the
groomer as well as the groomee. Radiotracer studies are
necessary to confirm the assimilation of ingested microbes.
Flagellates as Food
Trophic stages of protozoans are vulnerable when they
are passed from adult to offspring during proctodeal
trophallaxis in the wood-feeding cockroach Cryptocercus.
Some flagellate species are extremely large—Barbulanympha
may be up to 340 long (Cleveland et al.,
1934), and first instars of Cryptocercus are unusually small
(Nalepa, 1996). Consequently, large flagellates may not be
able to pass through the proventriculus of early instars
without being destroyed; the phenomenon has been reported
in termites. Remnants of the flagellate Joenia were
observed in the gizzards of all young Kalotermes examined
by Grassé and Noirot (1945). It may take several
molting cycles before the gizzard of the young host is of a
diameter to allow passage of the largest flagellates. Typically,
the large protozoans are the last ones established in
Cryptocercus; they are not habitually found in the hindgut
until the third instar (Nalepa, 1990). Until then, the numerous
flagellates passed from adult to offspring in the
proctodeal fluids are a high-quality, proteinaceous food
(Grassé, 1952) available at low metabolic cost to the consumer
(Swift et al., 1979). The normal death of protozoans
within the gut may also contribute to microbial
protein in the hindgut fluids. Cleveland (1925) indicated
that “countless millions of them must die daily” in a single
host.
Fungi as Food
Fig 5.5 Grooming behavior. (A) Periplaneta americana passing
an antenna through its mouth during autogrooming. Modified
from Jander (1966), courtesy of Ursula Jander. (B) Fourth-instar
Cryptocercus punctulatus allogrooming a sibling. Photo by
C.A. Nalepa.
Many animals feed on fungal tissue by selectively grazing
on fruiting bodies and mycelia. Others consume small
quantities of fungal tissue along with larger amounts of
the substrate on which the fungus is growing (Kukor
and Martin, 1986). Cockroaches as a group span both
categories, using fungi as food either incidentally or
specifically.
Among the more selective feeders are species like Parcoblatta,
which include mushrooms in their diet (Table
4.1), and Lamproblatta albipalpus, observed grazing on
mycelia covering the surface of rotten wood and dead
leaves (Gautier and Deleporte, 1986). The live and dead
plant roots used as food by the desert cockroach Arenivaga
investigata are sheathed in mycorrhizae, and numerous
fungal hyphae can be found in the crop (Hawke and
Farley, 1973). Shelfordina orchidae eats pollen, fungal hy-
82 COCKROACHES