Genetic comparison between torafugu Takifugu rubripes and its closely related species karasu Takifugu chinensis

摘要

Sequence analyses of mitochondrial (mt) and nuclear genes were performed for genetic comparison between two Takifugu pufferfish species: torafugu T. rubripes and karasu T. chinensis. With a sequence coverage of 20% in mtDNA, 640, 308, 344, 522 and 697 bp encoding mt 16S ribosomal RNA (rRNA), adenosine triphosphatase 6 (ATPase 6), nicotinamide adenine dinucleotide dehydrogenase subunit 4 (ND4), ND5 and cytochrome b (cyt b), respectively, among 24 wild torafugu, 24 wild karasu and six hybrid-like samples, 15% of the torafugu identified by external color patterns showed nucleotide sequences consistent with karasu. Meanwhile, sequences of 60% karasu were consistent with those registered for torafugu (AJ421455). As for the hybrid-like samples, two possessed karasu-specific sequences in some base positions while torafugu-specific sequences in others. The remaining hybrid-like samples possessed torafugu-specific sequences. On the other hand, the mt control region did not show such type of consistency. Analysis of nuclear melanocortin receptor genes (MC1R, MC4R) among 54 samples showed 99–100% inter- and intraspecific sequence identity. Partial nuclear 18S rRNA, complete internal transcribed spacer 1 (ITS1), partial 5.8S rRNA and ITS2 genes showed similar levels of identity, indicating a very low level of variation in their respective gene fragments between the two Takifugu species.