METHANE PRODUCTION IN TERRESTRIAL ARTHROPODS

We have screened more than 110 representatives of the different taxa o f terrestrial arthropods for methane production in order to obtain add itional information about the origins of biogenic methane. Methanogeni c bacteria occur in the hindguts of nearly all tropical representative s of millipedes (Diplopoda), cockroaches (Blattaria), termites (Isopte ra), and scarab beetles (Scarabaeidae), while such methanogens are abs ent from 66 other arthropod species investigated. Three types of symbi osis were found: in the first type, the arthropod's hindgut is coloniz ed by free methanogenic bacteria; in the second type, methanogens are closely associated with chitinous structures formed by the host's hind gut; the third type is mediated by intestinal anaerobic protists with intracellular methanogens. Such symbiotic associations are Likely to b e a characteristic property of the particular taxon. Since these taxa represent many families with thousands of species, the world populatio ns of methane-producing arthropods constitute an enormous biomass. We show that arthropod symbionts can contribute substantially to atmosphe ric methane.