The mitochondrial genomes of sarcoptiform mites: are any transfer RNA genes really lost?

BACKGROUND

Mitochondrial (mt) genomes of animals typically contain 37 genes for 13 proteins, two ribosomal RNA (rRNA) genes and 22 transfer RNA (tRNA) genes. In sarcoptiform mites, the entire set of mt tRNA genes is present in Aleuroglyphus ovatus, Caloglyphus berlesei, Dermatophagoides farinae, D. pteronyssinus, Histiostoma blomquisti and Psoroptes cuniculi. Loss of 16 mt tRNA genes, however, was reported in Steganacarus magnus; loss of 2-3 tRNA genes was reported in Tyrophagus longior, T. putrescentiae and Sarcoptes scabiei. Nevertheless, convincing evidence for mt gene loss is lacking in these mites.

RESULTS

We sequenced the mitochondrial genomes of two sarcoptiform mites, Histiostoma feroniarum (13,896 bp) and Rhizoglyphus robini (14,244 bp). Using tRNAScan and ARWEN programs, we identified 16 and 17 tRNA genes in the mt genomes of H. feroniarum and R. robini, respectively. The other six mt tRNA genes in H. feroniarum and five mt tRNA genes in R. robini can only be identified manually by sequence comparison when alternative anticodons are considered. We applied this manual approach to other mites that were reported previously to have lost mt tRNA genes. We were able to identify all of the 16 mt tRNA genes that were reported as lost in St. magnus, two of the three mt tRNA genes that were reported as lost in T. longior and T. putrescentiae, and the two mt tRNA genes that were reported as lost in Sa. scabiei. All of the tRNA genes inferred from these manually identified genes have truncation in the arms and mismatches in the stems.

CONCLUSIONS

Our results reveal very unconventional tRNA structures in sarcoptiform mites and do not support the loss of mt tRNA genes in these mites. The functional implication of the drastic structural changes in these tRNA genes remains to be investigated.

[Investigation and morphological observation of Histiostoma feroniarum breeding in Chinese herbal medicine Rhizoma Zingiberis]

OBJECTIVE

To understand the breeding situation of Histiostoma feroniarum in Chinese herbal medicine Rhizoma Zingiberis.

METHODS

The Rhizoma Zingiberis sold on the market was selected and brushed. The dust from Rhizoma Zingiberis was screened under a microscope to search the mites. The mites were made into specimens to identify the species.

RESULTS

The mites were H. feroniarum. Totally 14 mites were found in 100 g dust sample, with the density of breeding of 0.14/g.

CONCLUSIONS

H. feroniarum could breed in Chinese herbal medicine Rhizoma Zingiberis, and the prevention and control measures should be adopted.

[Morphologic observation on Histiostoma feroniarum in Allium cepa]

OBJECTIVE

To observe the external morphology of Histiostoma feroniarum hypopus under a light microscope.

METHODS

The samples were collected in a mushroom cultivation base, and the H. feroniarum hypopus was isolated and purified. The slide samples were prepared and observed under an optical microscope.

RESULTS

The back body of the H. feroniarum hypopus was flat with tiny bristles, the epidermis was of significant ossification, the ventral had four pairs of slender feet stretched, the sucker plate was prosperous in the end of the body, and the sucker plate had eight suckers. The gnathosoma was thin, long and highly specialized.

CONCLUSIONS

The light microscopy shows the morphological characteristics of H. feroniarum hypopus, providing the basis for identifying and life cycle study.