Methane production in terrestrial arthropods.

Abstract

We have screened more than 110 representatives of the different taxa of terrsrial arthropods for methane production in order to obtain additional information about the origins of biogenic methane. Methanogenic bacteria occur in the hindguts of nearly all tropical representatives of millipedes (Diplopoda), cockroaches (Blattaria), termites (Isoptera), and scarab beetles (Scarabaeidae), while such methanogens are absent from 66 other arthropod species investigated. Three types of symbiosis were found: in the first type, the arthropod's hindgut is colonized by free methanogenic bacteria; in the second type, methanogens are closely associated with chitinous structures formed by the host's hindgut; the third type is mediated by intestinal anaerobic protists with intracellular methanogens. Such symbiotic associations are likely to be a characteristic property of the particular taxon. Since these taxa represent many families with thousands of species, the world populations of methane-producing arthropods constitute an enormous biomass. We show that arthropod symbionts can contribute substantially to atmospheric methane.Biopolymer degradation by anaerobic biota is responsible for most atmospheric methane, but there is still a considerable lack of knowledge about its sources and sinks (1, 2). A long-standing dispute concerns the potential contributions to atmospheric methane by methanogenic bacteria in the hindguts of insects (3-9). We (Table 1). They were subjected to measurements of gas emissions within 24-48 hr. For this period, the animals were fed their particular diet.Screening Procedure. The living arthropods were placed into serum vials (50 or 250 ml) and sealed with butyl rubber stoppers. For 2-12 hr the arthropods (0.5-50 g fresh weight, depending on size and availability of specimens) were incubated at room temperature (210C). The detection limit for methane was in the nmol range, guaranteeing that any significant methane emission could be detected by gas chromatography of gas samples taken at the end ofthe incubation period. Under these conditions, all methane-emitting species produced >100 nmol of methane during the incubation period. All nonproducers failed to produce methane concentrations higher than the background level (maximum, 10-20 nmol), even if the incubation time was prolonged and higher numbers of arthropods were incubated. Specimens of representative species of nonproducers were subjected to microscopic inspection (cf. Table 1); in all cases, the absence of methanogenic bacteria was confirmed. Small insects mining in wood were incubated in situ in heavily populated blocks of wood in 1-literjars for prolonged periods (up to 1 week, with daily gas measurements).Quantitative Gas Chromatographic Determinations. Determinations of methane were performed by using ethane as an internal standard (5). Continuous monitoring of the methane emission of the different cockroach species and millipedes with the aid of an experimental photoacoustic CO laser setup confirmed that the intestinal methane w...

Shared and unique environmental factors determine the ecology of methanogens in humans and rats

“…Although all rumens have significant numbers of methanogens, in the world of the animal hindgut and the human colon, some have it and others do not (9,10). The reasons for their absence or very low number in some colons are unknown.…”

“…It has been suggested that congenital or taxonomic factors determine methane-producing status in the human large bowel (15) or the lower animal hindgut (9,16), but opinion varies about whether these factors relate to shared early familial environment (15) or to familial genetic influences (16,17).…”

Entomophagy: A Viable Opportunity for Food Security

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Methanogens in the Environment: An Insight of Methane Yield and Impact on Global Climate Change

“…The unceasing improvement of molecular methods for this study of environmental microorganisms has facilitated the characterization of methanogens community. Methanogens range has already been studied and species were isolated from a extensive scale of environments: gut of terrestrial arthropods (Hackstein and Stumm, 1994), termite guts (Ohkuma et al, 1999), hydrothermal vents (Takai and Horikoshi, 1999), hydrocarboncontaminated soils (Watanabe et al, 2002), ocean (Reeburgh, 2007) sediment soils (Bridgham et al, 2013), freshwater (Borrel et al, 2011) and humans (Saengkerdsub and Ricke, 2014). Among submerged soils, rice field soils have been widely examined (Ramakrishnan et al, 2001).…”