The complete mitochondrial genome of the short snouted seahorse Hippocampus hippocampus Linnaeus 1758 (Syngnathiformes: Syngnathidae) and its phylogenetic implications

Mitochondrial genome announcements need to consider existing short sequences from closely related species to prevent taxonomic errors

The reconstruction of complete mitochondrial genomes (mitogenomes) has considerable potential to clarify species relationships in cases where morphological analysis and DNA sequencing of individual genes are inconclusive. However, the trend to use only mitogenomes for the phylogenies presented in mitogenome announcements carries the inherent risk that the study species’ taxonomy is incorrect because no mitogenomes have yet been reconstructed for its sister species. Here, I illustrate this problem using the mitogenomes of two seahorses, Hippocampus capensis and H. queenslandicus. Both specimens used for mitogenome reconstruction originated from traditional Chinese medicine markets rather than native habitats. Although mitogenome phylogenies placed these specimens correctly among the seahorses from which mitogenomes were available at the time, incorporating single-marker sequence from closely related species into the phylogenies revealed that both mitogenomes are problematic. The mitogenome of the endemic South African H. capensis did not cluster among single-marker DNA sequences of seahorses from the species’ native habitat, but among sequences submitted under the names H. casscsio, H. fuscus and H. kuda that originated from all over the Indo-Pacific, including China. Phylogenetic placement of the mitogenome of H. queenslandicus within a cluster of seahorses that also included H. spinosissimus confirms an earlier finding that H. queenslandicus is a synonym of H. spinosissimus, a widespread Indo-Pacific species that also occurs in China. It is recommended that mitogenome announcements incorporate available single-marker sequences of closely related species, not only mitogenomes. The reconstruction of mitogenomes can exacerbate taxonomic confusion if existing information is ignored.

Diversity of Seahorse Species (Hippocampus spp.) in the International Aquarium Trade

Seahorses (Hippocampus spp.) are threatened as a result of habitat degradation and overfishing. They have commercial value as traditional medicine, curio objects, and pets in the aquarium industry. There are 48 valid species, 27 of which are represented in the international aquarium trade. Most species in the aquarium industry are relatively large and were described early in the history of seahorse taxonomy. In 2002, seahorses became the first marine fishes for which the international trade became regulated by CITES (Convention for the International Trade in Endangered Species of Wild Fauna and Flora), with implementation in 2004. Since then, aquaculture has been developed to improve the sustainability of the seahorse trade. This review provides analyses of the roles of wild-caught and cultured individuals in the international aquarium trade of various Hippocampus species for the period 1997–2018. For all species, trade numbers declined after 2011. The proportion of cultured seahorses in the aquarium trade increased rapidly after their listing in CITES, although the industry is still struggling to produce large numbers of young in a cost-effective way, and its economic viability is technically challenging in terms of diet and disease. Whether seahorse aquaculture can benefit wild populations will largely depend on its capacity to provide an alternative livelihood for subsistence fishers in the source countries. For most species, CITES trade records of live animals in the aquarium industry started a few years earlier than those of dead bodies in the traditional medicine trade, despite the latter being 15 times higher in number. The use of DNA analysis in the species identification of seahorses has predominantly been applied to animals in the traditional medicine market, but not to the aquarium trade. Genetic tools have already been used in the description of new species and will also help to discover new species and in various other kinds of applications.

Complete mitochondrial genome and phylogenetic analysis of the Gray's pipefish Halicampus grayi Kaup 1856

In the present study, the complete mitochondrial genome of H. grayi was determined and annotated. The circular mitogenome is 16,959 bp in length and contains 13 protein-coding genes (PCGs), two rRNA genes, 22 tRNA genes, and a control region. Most of the PCGs start with ATG, but CO1 begins with a GTG start codon. Phylogenetic analysis revealed that H. grayi was strictly related to network pipefish Corythoichthys flavofasciatus with 100% bootstrap support value. This work provides basic molecular information that would be useful for further investigation on conservation genetics and evolutionary relationships of H. grayi.