Dorcus

Abstract: Stag beetles are xylophagous insects that feed mainly on dead wood. They play an important role in the decomposition of dead wood in forest ecosystems. Most dead wood contains 1% nitrogen at most. It is suspected that stag beetles can utilize atmospheric nitrogen. We show that the larvae of Dorcus (Macrodorcus) rectus exposed to nitrogen reduce acetylene to ethylene in a time-dependent fashion. No reaction was detected with the dead wood or autoclaved larvae, suggesting that living larvae use the reaction for fixing nitrogen. Acetylene reduction to ethylene by larvae increased with incubation time. This effect was not seen using decayed wood only, autoclaved wood only or autoclaved larvae. Acetylene reduction by the larva proceeded at 1.25 ± 0.37 nmol acetylene/h/g (fresh wt), corresponding to the fixation of 0.25 μg nitrogen per day per larva.

Abstract: An updated checklist of the Lucanidae (Coleoptera) from Iran is given. New locality records are listed and some dubious distributional records are discussed. Dorcus vavrai Nonfried, 1905 is placed in synonymy with Dorcus peyronis Reiche and Saulcy, 1856 (new synonymy) The female of Lucanus xerxes Kral, 2004 is described. A key for the identification of the Iranian stag beetle species is also provided and all the species are figured.

Abstract: Dorcus koreanus Jang and Kawai, 2008 was recently described as a valid species in Haenam, South Korea, based on morphology. However, the taxonomic position and relationships of this new species with the related species Dorcus japonicus and Dorcus carinulatus were not examined in detail. To address this issue, we evaluated the phylogenetic relationships of D. koreanus to its related species based on molecular analyses of mitochondrial 16S rRNA gene sequences. The molecular evidence suggested that D. koreanus and D. carinulatus are more closely related to each other than either is to D. Japonicus. The genetic divergence between D. koreanus and D. carinulatus ranged from 1.2 to 1.6%, whereas that between D. koreanus and D. japonicus ranged from 9.0 to 9.2%. By comparing the range of nucleotide substitutions within Lucanidae, we determined that the sequence distance between D. koreanus and D. carinulatus is smaller than that for required for species-level distinction. Therefore, we reduce D. koreanus to subspecies rank, as Dorcus carinulatus koreanus stat. nov.

Abstract: The search for new antibiotics or antifungal agents is crucial for the chemotherapies of infectious diseases. The limited resource of soil bacteria makes it difficult to discover such new drug candidate. We, therefore, focused on another bacterial resource than soil bacteria, the microbial flora of insect species. In the present study, we isolated 40 strains of bacteria and fungi from the mycangia of three species of stag beetle, Dorcus hopei binodulosus, Dorcus rectus, and Dorcus titanus pilifer. We identified those species with their ribosomal DNA sequences, and revealed that Klebsiella spp. are the most frequent symbiont in the stag beetle mycangia. We examined whether these microorganisms produce antibiotics against a Gram-negative bacterium, Escherichia coli, a Gram-positive bacterium, Staphylococcus aureus, or a fungus, Cryptococcus neoformans. Culture supernatants from 33, 29, or 18 strains showed antimicrobial activity against E. coli, S. aureus, or C. neoformans, respectively. These findings suggest that bacteria present in the mycangia of stag beetles are useful resources for screening novel antibiotics.