Fungi as Food

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 Par-coblatta, 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 Areni-vaga 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-

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-in-star Cryptocercus punctulatus allogrooming a sibling. Photo by C.A. Nalepa.

phae, and plant tissue (Lepschi, 1989), and gut content analyses have clearly established that many species in tropical rainforest consume fungal hyphae and spores (WJB, unpubl. obs.). Australian Ellipsidion spp. are often associated with sooty mold, although it is not known if they eat it (Rentz, 1996). No known cockroach specializes on fungi, although species that live in the nests of fungus-growing ants and termites may be candidates.

All types of decaying plant tissues, whether foliage, wood, roots, seeds, or fruits, are thoroughly permeated by filamentous fungi (Kukor and Martin, 1986). The fungal contribution to the nutrient budget of cockroaches, however, is unknown. Chitin is the major cell wall component of most fungi and constitutes an average of 10% of fungal dry weight (range = 2.6-26.2) (Blumenthal and Rose-man, 1957). Although chitinases are apparently rare in the digestive processes of most detritus-feeding insects (Martin and Kukor, 1984), it is distributed throughout the digestive tract of P. americana. The enzyme is related to cannibalism and the consumption of exuvia (Water-house and McKellar, 1961), but may also play a role in breaking down fungal polysaccharides.

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