Ribosomal DNA sequences reveal gregarine pathogens (Apicomplexa: Gregarinia) in mites and other arachnids (Arachnida)

Abstract

Ribosomal RNA genes are widely applied in phylogenetic studies due to the ubiquitous presence and relative conservation of many regions of their nucleotide sequences. Many specific PCR primers have been developed for amplification of the rDNA cluster fragments from particular taxa. However, the use of universal primers hybridising to the conserved rDNA regions enables discovering sequences of eukaryote endosymbiont or pathogen origin in the analysed DNA sample. This approach makes it possible to detect gregarines (Protozoa: Apicomplexa) that are obligate parasites of digestive tracts and body cavities in invertebrate animals. Here we report new uncultured gregarine clones detected by rDNA sequencing in one harvestmen, Rilaena triangularis (Opiliones: Phalangioidea), and two astigmatid feather mite species, Proctophyllodes stylifer and P. ateri (Acari: Analgoidea). To our knowledge, this is the first record of parasitic Astigmata (cohort Psoroptidia) infected with gregarines. Comparison of the amplified rDNA fragments with sequences deposited in GenBank revealed that analysed sequences corresponded to 18S rDNA from the genera Gregarina (85 and 90 % identity with G. chortiocetes for sequences found in P. ateriand harvestman, and Syncystis (87 % identity with S. mirabilis for sequences found in P. stylifer). The differences observed between nucleotide sequences of the gregarine 18S rDNA fragments indicated that the gregarine isolates from which the sequences were derived belonged to presumably three different species.