[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 (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.

<Reference Paper>

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/)."