Cirrhitichthys polyactis
A hawkfish with a lunate tail and high dorsal ray count.
The swallowtail hawkfish (Cyprinocirrhites polyactis), also called the lyretail hawkfish, is a marine ray-finned fish in the family Cirrhitidae. It is the sole species in its genus. This fish lives on tropical reefs in the Indian Ocean and western Pacific Ocean, from South Africa and Kenya east to Palau, Melanesia, and Fiji, north to Japan, and south to Australia, including Western Australia and the Great Barrier Reef. It is found at depths of 10 to 132 meters (33 to 433 feet), on steep slopes and small coral heads exposed to currents.
The species was first described in 1874 as *Cirrhitichthys polyactis* by Dutch ichthyologist Pieter Bleeker, with the type locality being Ambon Island. In 1917, Japanese ichthyologist Shigeho Tanaka described a new species, *Cyprinocirrhites ui*, placing it in a new monotypic genus; this was later considered a synonym of *Cirrhitichthys polyactis*, but the monotypic genus was retained. The genus name combines *cyprinus* (meaning "carp" or "minnow") with *cirrhites* (an alternate spelling of the type genus *Cirrhitus*); Tanaka did not explain the reference to carp. The specific name *polyactis* means "many rayed," referring to the high number of soft rays in the dorsal fin, more than any other hawkfish.
The swallowtail hawkfish differs from all other hawkfishes in two ways: its lunate (crescent-shaped) caudal fin, with both upper and lower lobes elongated, and its high dorsal fin soft ray count. The dorsal fin has 10 spines, each tipped with numerous cirri, and 16–17 soft rays, with the first ray elongated. The anal fin has 3 spines and 6–7 soft rays. The caudal fin is lunate, with the uppermost ray of the upper lobe and the lowest ray of the lower lobe extending into filaments. The lower pectoral fin rays are longer than the others. This species reaches a maximum total length of 15 cm (5.9 in). Its overall color is orange to brownish-orange, often with orange-red to brownish blotches.
Unlike most hawkfishes, which are benthic (bottom-dwelling), the swallowtail hawkfish stays in the water column several meters above the substrate. It preys mainly on pelagic crustaceans, copepods, and other zooplankton. It may be a protogynous hermaphrodite, but further study is needed to confirm this. The species is occasionally found in the aquarium trade.
Quick Facts
- Taxon
- Cyprinocirrhites polyactis
Facts from the source article.
Lore & Background
The swallowtail hawkfish was first formally described in 1874 by Dutch ichthyologist Pieter Bleeker as Cirrhitichthys polyactis, with the type locality given as Ambon Island. In 1917, Japanese ichthyologist Shigeho Tanaka described a new species, Cyprinocirrhites ui, placing it in a new monotypic genus; this was later considered a synonym of Cirrhitichthys polyactis, but the monotypic genus was retained. The genus name combines cyprinus, meaning 'carp' or 'minnow' (Tanaka did not explain why), and cirrhites, an alternative spelling of the type genus Cirrhitus. The specific name polyactis means 'many rayed', referring to the high count of soft rays in the dorsal fin, higher than any other hawkfish.
This species differs from all other members of the family Cirrhitidae in two features: the lunate caudal fin with both upper and lower lobes elongated, and the high dorsal fin soft ray count. The dorsal fin contains 10 spines, each with numerous cirri at its tip, and 16–17 soft rays, the first ray being elongated. The anal fin has 3 spines and 6–7 soft rays. The lower pectoral fin rays are longer than the others. The overall colour is orange to brownish-orange, frequently with orange-red to brownish blotches.
Unlike other hawkfishes, which are mostly benthic, the swallowtail hawkfish stays in the water column several metres above the substrate. It preys largely on pelagic crustaceans, copepods, and other zooplankton. It may be a protogynous hermaphrodite, but further study is needed to confirm this.
Reader's Guide
The swallowtail hawkfish is significant as the only known member of its genus, Cyprinocirrhites, and for its distinctive morphology that sets it apart from all other hawkfishes. Its lunate caudal fin with elongated lobes and high dorsal soft ray count are unique within the family Cirrhitidae. The species was first described in 1874 by Pieter Bleeker, and later a separate monotypic genus was proposed by Shigeho Tanaka in 1917, though the species was eventually synonymized while the genus was retained. Its behavior is also notable: unlike most benthic hawkfishes, it inhabits the water column several meters above the substrate, feeding on pelagic crustaceans and zooplankton. The species is found on tropical reefs in the Indian Ocean and western Pacific Ocean, at depths between 10 and 132 meters, and is occasionally seen in the aquarium trade. Its potential protogynous hermaphroditism remains unconfirmed and requires further study.
Did You Know?
- The swallowtail hawkfish is the only known member of its genus, Cyprinocirrhites.
- Its specific name polyactis means 'many rayed', referring to its high dorsal fin soft ray count.
Frequently Asked Questions
What is Cirrhitichthys polyactis?
Cirrhitichthys polyactis is a small hawkfish now recognized under the genus Cyprinocirrhites, commonly known as the swallowtail or lyretail hawkfish. It is the sole member of that genus, making it a one-of-a-kind lineage within the hawkfish family Cirrhitidae.
Where does Cirrhitichthys polyactis live in the wild?
This species ranges across tropical reefs of the Indian Ocean and western Pacific, stretching from South Africa and Kenya east to Fiji and Japan and south to the Great Barrier Reef. It typically occupies steep reef slopes and small current-exposed coral heads at depths of 10 to 132 meters.
How big does Cirrhitichthys polyactis get?
The swallowtail hawkfish tops out at roughly 15 centimeters (about 6 inches) in total length, which is on the smaller side even among hawkfish.
What makes Cirrhitichthys polyactis look different from other hawkfish?
Its most eye-catching traits are a deeply forked, crescent-shaped tail and a dorsal fin with an unusually high ray count, both of which separate it visually from its cirrhitid relatives.
Who originally described Cirrhitichthys polyactis?
The species was first named in 1874 by Dutch ichthyologist Pieter Bleeker, who assigned it to the genus Cirrhitichthys. It has since been moved into its own genus, Cyprinocirrhites, to reflect its distinct body plan.
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