[Okinawa Churaumi Aquarium] The "Mysterious 2 Types" Discovered in the Deep Sea Were Actually Male and Female "Kihana-dai" – Male Individuals with Beautifully Lustrous Scales Now on Display!

Key facts

  • [Okinawa Churaumi Aquarium] The "Mysterious 2 Types" Discovered in the Deep Sea Were Actually Male and Female "Kihana-dai" – Male Individuals with Beautifully Lustrous Scales Now on Display!
  • The Okinawa Churaumi Aquarium is now exhibiting a male individual of the rare Anthiinae family fish, Kihana-dai, which inhabits the deep sea. Previously, two types of fish with slight differences in color and form were collected and displayed, but it was unclear whether they were different species or variations within the same species. A research team led by Kindai University has reported the existence of sexual dimorphism in Kihana-dai, clarifying that these "mysterious 2 types" correspond to the male and female of the same species. Furthermore, it is suggested that the species may undergo protogynous sex change, transforming from female to male as they mature, with future research expected to confirm this process.
  • Source: PR Times
  • Date: June 11, 2026

Direct answer

The Okinawa Churaumi Aquarium is now exhibiting a male individual of the rare Anthiinae family fish, Kihana-dai, which inhabits the deep sea. Previously, two types of fish with slight differences in color and form were collected and displayed, but it was unclear whether they were different species or variations within the same species. A research team led by Kindai University has reported the existence of sexual dimorphism in Kihana-dai, clarifying that these "mysterious 2 types" correspond to the male and female of the same species. Furthermore, it is suggested that the species may undergo protogynous sex change, transforming from female to male as they mature, with future research expected to confirm this process.

Citation
[Okinawa Churaumi Aquarium] The "Mysterious 2 Types" Discovered in the Deep Sea Were Actually Male and Female "Kihana-dai" – Male Individuals with Beautifully Lustrous Scales Now on Display! (June 11, 2026), PR Times
Source
PR Times
Date
June 11, 2026
The Okinawa Churaumi Aquarium is now exhibiting a male individual of the rare Anthiinae family fish, Kihana-dai, which inhabits the deep sea. Previously, two types of fish with slight differences in color and form were collected and displayed, but it was unclear whether they were different species or variations within the same species. A research team led by Kindai University has reported the existence of sexual dimorphism in Kihana-dai, clarifying that these "mysterious 2 types" correspond to the male and female of the same species. Furthermore, it is suggested that the species may undergo protogynous sex change, transforming from female to male as they mature, with future research expected to confirm this process.
調査出典：PR Times

📋 Article Processing Timeline

  • 📰 Published: June 11, 2026 at 22:00
  • 🔍 Collected: June 11, 2026 at 13:21
  • 🤖 AI Analyzed: June 12, 2026 at 16:52 (27h 30m after Collected)
The Okinawa Churaumi Aquarium (Location: Motobu Town, Kunigami District, Okinawa Prefecture; Director: Keiichi Sato) is exhibiting a male individual of the rare Anthiinae family fish, Kihana-dai, which inhabits the deep sea. 【Kihana-dai】 Scientific Name: Selenanthias sp. A species belonging to the genus Selenanthias in the Anthiinae family, approximately 12 cm in total length. It is a rare species that inhabits deep waters from Kanagawa Prefecture to the Ryukyu Islands, living around 200 meters deep near the coast of Okinawa Island. ■ Exhibition Location: "Journey to the Deep Sea" individual tank corner ■ Exhibited Individual: 1 Kihana-dai (Male) *Exhibition may end depending on the condition of the organism. The aquarium has previously collected and exhibited two types of fish belonging to the genus Selenanthias, which showed slight differences in coloration and morphology. However, it was unclear whether they were separate species or variations within the same species. Recently, a research team centered at Kindai University reported that sexual dimorphism (differences in morphology and coloration between males and females) exists in Kihana-dai. This clarified that the "mysterious 2 types" that had puzzled the aquarists correspond to the male and female of Kihana-dai. Furthermore, the paper suggests that this species may undergo "protogynous sex change," where it changes sex from female to male with growth. It is expected that this process can be confirmed through continued observation and breeding at the aquarium. The aquarium will continue to work on elucidating the ecology of various marine organisms, including this species, through ongoing exhibition, breeding, and research. Nomura, R., Uechi, T., Kobayashi, Y., Miyamoto, K., Wada, H., & Miyazaki, Y. (2026). Sexual dimorphism and protogeny in two species of Selenanthias (Serranidae: Anthiadinae) collected from Japanese waters: R. Nomura et al. Ichthyological Research, 1-15. About Okinawa Churaumi Aquarium "Chura" in "Okinawa Churaumi Aquarium" means "beautiful, pure, and clear" in the Okinawan language. Under the exhibition concept of recreating the naturally rich Okinawan sea, the aquarium creates encounters with a wide variety of aquatic life inhabiting the waters of the Southwest Islands and the Kuroshio Current, with the theme of "Encountering the Okinawan Sea." Furthermore, as a world-leading aquarium, it conducts research on the conservation and breeding of rare species, as well as biological research. It also aims to be a hub facility that provides high-quality educational opportunities to all people and leads sustainable tourism. It is certified as a registered museum, which has legal standing among museums nationwide. *Okinawa Churaumi Aquarium is managed and operated by the "Okinawa Churashima Foundation (URL https://churashima.okinawa/)."

FAQ

How can the male and female Kihana-dai be distinguished?

Kihana-dai exhibit sexual dimorphism, meaning males and females differ in color and form. The male individual on display is particularly characterized by its beautifully lustrous scales.

Where does the Kihana-dai inhabit?

It is a rare species inhabiting deep waters from Kanagawa Prefecture to the Ryukyu Islands, particularly around 200 meters deep near the coast of Okinawa Island.

How long will the Kihana-dai be on display?

The exhibition period may vary depending on the condition of the organism. Please check with the aquarium for the latest information.

Are there other fish that undergo sex change?

Yes, clownfish are well-known examples. Kihana-dai is also suggested to undergo protogynous sex change, and research is ongoing.

What is the theme of the Okinawa Churaumi Aquarium's exhibits?

With the theme 'Encountering the Okinawan Sea,' the aquarium recreates the naturally rich Okinawan sea, creating opportunities to encounter diverse aquatic life.

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