Toxocara vitulorum (Ascaridida: Nematoda): mitochondrial gene content, arrangement and composition compared with other Toxocara species.

Partial mitochondrial (mt) genome sequence (10,486bp) from the parasitic nematode Toxocara vitulorum was determined and its organization and structure compared with those of T. cati, T. canis and T. malaysiensis. The obtained mt genome sequence of T. vitulorum contains 10 protein-coding genes (cytochrome c oxidase subunits 1-3, Nicotinamide adenine dinucleotide dehydrogenase subunits 1-5, ATP synthase subunit 6 and cytochrome b), 14 transfer RNA genes and the large ribosomal RNA gene (rrnL), non-coding regions. ORF encoding for ATPase subunit 8 is not found in this partial mtDNA sequence. Five translation initiation codons were inferred, ATT, ATG, GTG, GTT and TTG. Most of the genes used TAG or TAA as a stop codon and two genes ended with a T. The gene arrangement and composition of the T. vitulorum mt genome is very similar to that of other Toxocara species mitochondrial genomes sequenced thus far. All genes are transcribed in the same direction, as other Toxocara species. This genome has a high A+T content (67.5%) and low G+C content (32.5%). Phylogenetic reconstruction based on aligned nucleotide sequences of seven taxa provided strong support that Toxocara vitulorum is more closely related to T. malaysiensis than to T. canis and T. cati.