Production of methyl mercury in the gut of the Australian termite Mastotermes darwiniensis

Animals are often exposed to or can ingest heavy metals along with their food. Therefore, we tested whether the hindgut microbiota of Mastotermes darwiniensis possesses the capability to form methyl mercury. The termite M. darwiniensis (Isoptera) was fed with saw dust containing different concentrations of inorganic mercury. Methyl mercury was determined by purge‐and‐trap capillary gas chromatography‐atom fluorescence spectrometry (CGC‐AFS) using ethyl mercury chloride as the internal standard. Total mercury concentrations were determined in the termite tissue by inductive coupled plasma‐isotope dilution mass spectrometry (ICP‐IDMS) after microwave‐assisted digestion. The obtained results showed in vivo methyl mercury production in terrestrial insects for the first time. Desulfovibrio intestinalis isolated from M. darwiniensis was identified as a biomethylating species of the intestinal microbiota.     

Direct potentiometric determination of redox potentials of the gut contents in the termites Zootermopsis nevadensis and Cubitermes severus and in three other arthropods

A Pt and calomel electrode combination were used to determine the redox potentials of the gut contents in two termites, Zootermopsis nevadensis and Cubitermes severus. Strongly reducing conditions occurred in the paunch of Z. nevadensis (mean E_h = ?160 mV), consistent with many evidences that anaerobic fermentation of wood polymers occurs at this site. In C. severus, a soil-feeder, equivalent regions of the hindgut were more midly reducing (P1: mean E_h = ?104 mV; P3: mean E_h = ?47 mV) while the colon appeared microaerobic or aerobic. It is argued that these conditions are more appropriate to the digestion of humic materials. Potentials consistent with aerobic conditions were found throughout the guts of Periplaneta americana, Locusta migratoria and Glomeris marginata, although the cockroach hindgut was more reducing than the equivalent structures in the other non-termite species.     

Analysis of cellulolytic and hemicellulolytic enzyme activity within the Tipula abdominalis (Diptera: Tipulidae) larval gut and characterization of Crocebacterium ilecola gen. nov., sp. nov., isolated from the Tipula abdominalis larval hindgut

Abstract In forested stream ecosystems of the north and eastern United States, larvae of the aquatic crane fly Tipula abdominalis are important shredders of leaf litter detritus. T. abdominalis larvae harbor a dense and diverse microbial community in their hindgut that may aide in the degradation of lignocellulose. In this study, the activities of cellulolytic and hemicellulolytic enzymes were demonstrated from hindgut extracts and from bacterial isolates using model sugar substrates. One of the bacterial isolates was further characterized as a member of the family Microbacteriaceae. Taxonomic position of the isolate within this family was determined by a polyphasic approach, as is commonly employed for the separation of genera within the family Microbacteriaceae. The bacterial isolate is Gram-type positive, motile, non-sporulating, and rod-shaped. The G + C content of the DNA is 64.9 mol%. The cell wall contains B2γ type peptidoglycan, D- and L-diaminobutyric acid as the diamino acid, and rhamnose as the predominant sugar. The predominant fatty acids are 12-methyltetradecanoic acid (ai-C_15:0) and 14-methylhexadecanoic acid (ai-C_17:0). The isolate forms a distinct lineage within the family Microbacteriaceae, as determined by 16S rRNA sequence analysis. We propose the name Crocebacterium ilecola gen. nov., sp. nov., to accommodate this bacterial isolate. The type species is T202^T (ATCC BAA-1359; GenBank Accession DQ826511).     

The uptake of macromolecular materials in the hindgut of viviparous rockfish embryos

Regions of the gut of near-term embryos and new-born larvae of the viviparous rockfish Sebastes taczanowskii were examined histologically and immunohistochemically in order to ascertain whether they possessed the potential to absorb intact macromolecules. Compared with the hindgut of larvae 24 h after parturition, that of near-term embryos (stage 31) was found to be markedly hypertrophied and to react positively when tested for the presence of eosinophilic materials and with antibodies raised against extracts of the rockfish yolk (ab.a-E). In addition, near-term embryos incubated in Ringer solution containing 1% bovine serum albumin appeared to accumulate the protein within the epithelium of the hindgut. Furthermore, as confirmed by immunodiffusion analysis, the ovarian fluid contained materials which reacted positively to ab.a-E. These results suggest that ingestion of intact macromolecules occurs during the late embryonic stages and that the yolk-like substances detected within the hindgut epithelium of such embryos may be derived from the bathing ovarian fluid.     

Ciliated epithelium in the gut of larval Atlantic halibut, Hippoglossus hippoglossus

The presence of cilia was documented in the hindgut of larval Atlantic halibut ( Hippoglossus hippoglossus ) with the use of electron microscopy. Cilia were shown to be present as late as 8 and 9 day post hatch. These observations were compared to similar observations in more primitive teleosts.     

驯鹿对苔藓植物的选择食用及其生境的物种多样性

苔藓植物由于含有较高浓度的不饱和脂肪酸尤其是花生四烯酸可以提高动物的御寒能力,因此驯鹿和其他许多生活在寒冷地区的食草动物以及鸟类将苔藓作为主要的食物来源。为了进一步了解苔藓被采食的情况,本实验对生活在内蒙古大兴安岭满归敖鲁古雅民族乡的驯鹿3个月份的粪便(1999年采)进行了显微观察,发现其中苔藓植物在4月份占5.63%、6月份2.2%、9月份12.92%,3个月份的粪便中均以赤茎藓（Pleurozium schreberi）为主,占苔藓总量的70%以上,曲尾藓（Dicranum spp.）、毛叶苔（Ptilidium ciliare）和沼泽皱蒴藓（Aulacomnium palustre）也有少量食用。对驯鹿生活区域内4种林型下苔藓植物的盖度和生物量的测定结果表明,驯鹿对苔藓植物的选择食用与苔藓植物的物种和丰富度相关。     

Influence of lipopolysaccharides on the attachment of Thiobacillus ferrooxidans to minerals

The loss of part of the lipopolysaccharides (LPS) of the outer membrane of T. ferrooxidans negatively influenced the attachment of the bacteria to minerals and the bioleaching process. LPS previously extracted from T. ferrooxidans and which had come into contact with pyrite inhibited the attachment of cells to minerals and also negatively affected the bioleaching. These results suggest that LPS play an important role in the attachment of the microorganisms and therefore, its presence or absence could affect the bioleaching process.     

Adaptations to foliar absorption of faeces: a pathway in plant carnivory

BACKGROUND AND AIMS: Roridula plants capture insects but have no digestive enzymes. It has been hypothesized that Roridula leaves absorb nitrogen from the faeces of obligately associated, carnivorous hemipterans. But rapid movement across the leaf surfaces of most plant leaves is prevented by the presence of an impermeable cuticle. However, in carnivorous plants, cuticular gaps or pores in digestive/absorptive cells allow rapid movement across the leaf surface. Recently, it was suggested that the hemipteran-plant interaction constituted a new pathway for plant carnivory. Here, a further adaptation to this pathway is described by demonstrating how Roridula plants probably absorb hemipteran faeces rapidly through their leaf cuticles. METHODS: The dye neutral red was used to document the rapidity of foliar absorption and TEM to determine the nature of cuticular discontinuities in the leaf of Roridula. KEY RESULTS: Aqueous compounds diffuse rapidly across the cuticle of Roridula's leaves but not across the cuticles of co-occurring, non-carnivorous plant leaves. Furthermore, immature Roridula leaves were unable to absorb neutral red whereas mature leaves could. Using TEM, cuticular gaps and pores similar to those in other carnivorous plants were found in the epidermal cells of mature Roridula leaves. CONCLUSIONS: The leaf cuticle of Roridula is very thin (0-120 nm) and cell wall elements project close to the leaf surface, possibly enhancing foliar absorption. In addition to these, cuticular gaps were frequently seen and probably perform a function similar to those found in other carnivorous plants: namely the absorption of aqueous compounds. The cuticular gaps of Roridula are probably an adaptation to plant carnivory, supporting the newly described pathway.     

The role of volumetric feedback from the hindgut in the regulation of meal size in fifth-instar Locusta migratoria nymphs

ABSTRACT. Behavioural studies show that fullness of the hindgut influences the size of meals taken by fifth-instar Locusta migratoria L. nymphs, with the relevant information coming from the ileum and passing via the terminal abdominal ganglion. Morphological and electrophysiological studies suggest that stretch receptors on the posterior ileum, associated with branches of the rectal nerves, register extension of the ileal fold and probably also an increase in ileal volume. A system in which the volumetric feedbacks from both the crop and hindgut interact in the regulation of meal size is postulated.