Mitogenome reconstruction of an endangered African seahorse from a Traditional Chinese Medicine market was based on a misidentification

Abstract

The recently published complete mitochondrial genome of the endangered Knysna seahorse, Hippocampus capensis Boulenger, 1900, was based on a specimen obtained from a Traditional Chinese Medicine market. As H. capensis is endemic to temperate South Africa and exceptionally rare, illegal trade to supply Asian markets would constitute a considerable extinction risk. I investigated the phylogenetic placement of the Chinese specimen using mitochondrial DNA control region and cytochrome b sequences from the H. capensis mitogenome among corresponding published sequences of H. capensis and a number of closely related seahorse species. The Chinese specimen was distinct from H. capensis and instead clustered with H. casscsio, a seahorse that was recently described from the South China Sea. The sequences of H. casscsio clustered randomly among those of specimens identified as H. fuscus, a species whose taxonomic validity is disputed, and which is considered to be a synonym of the widespread Indo-Pacific seahorse H. kuda. Given that the morphological identification of seahorses is difficult, it is recommended that the publication of new species descriptions and genomic resources be preceded by a comprehensive comparison with the available molecular data. The taxonomy of seahorses is far from resolved, and cutting-edge molecular studies will not improve this situation if they do not take existing information into consideration.

Limitations of DNA barcoding in determining the origin of smuggled seahorses and pipefishes

“…First, in order to identify species using DNA barcoding, it is important that a standardised reference database exists, as the majority of the seahorses sequenced in this study (i.e., those associated with the Hippocampus kuda complex) could not be identified to species level. Although a comparatively short fragment of the COI gene was sequenced here due to the low quality of the tissue samples, a longer fragment of this marker does not provide more taxonomic resolution [52]. However, a different mitochondrial marker (control region) was suitable to distinguish between H. kuda from the Indian Ocean, and a clade comprising H. fuscus and Chinese seahorses referred to as H. casscsio [52], suggesting that it may be possible to resolve the taxonomy of the H. kuda complex by increasing the number of genetic markers.…”

“…The mitochondrial genome that was used to identify these samples [51] was most likely from a specimen native to China that in other recent literature has been referred to as H. casscsio Zhang, Qin, Wang & Lin, 2016, and which may be a synonym of H. fuscus [52].…”