Scientists from the Kyoto University Museum and elsewhere have described a new species of the fish genus Coradion from Australian waters.
Coradion calendula. Image credit: Matsunuma et al., doi: 10.5281/zenodo.7504828.
Coradion is a genus of marine ray-finned fish in the family Chaetodontidae (butterflyfishes).
Until now, the genus was known only from three scientifically recognized species native to the Indian and Pacific Oceans.
“Coradion was established by Kaup in 1860 for Chaetodon bennetti and Chaetodon chrysozonus,” said Kyoto University Museum researcher Mizuki Matsunuma and colleagues from Japan and Malaysia.
“Subsequently, Bleeker designated Chaetodon chrysozonus as the type species of Coradion.”
“The genus is diagnosed by a relatively short snout; brush-like teeth with thickened lips; dorsal-fin spines; fewer than 60 scales in the complete lateral line, ending at the caudal-fin base; and no supraorbital horns.”
“Three valid species of Coradion have been recognized in the Indo-West Pacific region: Coradion chrysozonus, Coradion altivelis, and Coradion melanopus.”
Named Coradion calendula, the newly-described species is most similar to Coradion chrysozonus.
“Coradion chrysozonus is distributed in the eastern Indian and western Pacific Oceans, from the Andaman Sea east to the Solomon Islands, and from Australia north to Taiwan and the Ogasawara Islands, Japan,” the researchers said.
“The species is common in Southeast Asia, and has often been photographed by divers, in addition to occurring in fish markets.”
Coradion calendula is distributed off northwestern and northern Australia, from the North West shelf east to northern Cape York Peninsula, in the vicinity of the Torres Strait.
The species has also been collected from Kendrew Island, Dampier Archipelago.
“All examined specimens were collected by demersal trawl from 11 to 128 m deep off northwestern Australia, most of the specimens being obtained from depths greater than 34 m,” the authors noted.
Individuals of Coradion chrysozonus feed on sponge tissue and benthic invertebrates; Coradion calendula likely has a similar dietary habit.
“However, because the pelvic fins are associated with maneuverability while swimming, rather than propulsion, the difference in pelvic-fin shape between large adults of Coradion calendula and Coradion chrysozonus may reflect a difference in their habitat, such as structural complexity of the coral reef,” they said.
“Although Coradion calendula inhabits relatively deep water (to 130 m depth) on the North West shelf, the population at the northeastern extreme of the distributional range inhabits shallower water (20 m depth), due to the decreasing maximum depth of shallow coastal waters off northern Australia, including Torres Strait and adjacent areas,” they added.
“Such a shift in habitat depth allows an overlap in the depth ranges of Coradion calendula and Coradion chrysozonus, thereby driving hybridization between the two closely related species in that area.”
The discovery of Coradion calendula is reported in a paper published online in the Journal of the Ocean Science Foundation.
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M. Matsunuma et al. 2023. Coradion calendula, a new butterflyfish from Australia (Teleostei: Chaetodontidae). Journal of the Ocean Science Foundation 40: 1-28; doi: 10.5281/zenodo.7504828
