FY2025

Research paper

Ribbon worms living on deep-sea trees: Alvinonemertes daitoensis sp. nov. (Nemertea, Monostilifera) associated with the glass sponge Walteria leuckarti (Porifera, Hexactinellida)

We discovered a new species of nemertean, Alvinonemertes daitoensis sp. nov., at a depth of 843 meters northwest of Minamidaito Island, Japan. This species is closely associated with the hexactinellid glass sponge Walteria leuckarti. It shows a distinctive ecological behavior, wrapping around the branches of its host sponge, similar to Alvinonemertes dariae and Sagornya dagmarae, suggesting convergent arboreal adaptations to tree- shaped host animals. The Japanese name of the species is “Daito Kinobori Himomushi,” based on this unique lifestyle.

Natsumi Hookabe, Geminne G. Manzano, Naoto Jimi, Hiroki Kise, James Davis Reimer, Shinji Tsuchida & Yoshihiro Fujiwara (2025) Ribbon worms living on deep-sea trees: Alvinonemertes daitoensis sp. nov. (Nemertea, Monostilifera) associated with the glass sponge Walteria leuckarti (Porifera, Hexactinellida), Systematics and Biodiversity, 23:1, 2504484, DOI:10.1080/14772000.2025.2504484

FY2024

Research paper

First northwestern Pacific records of the deep-sea cardinalfish Epigonus glossodontus (Teleostei, Epigonidae) from the Daito Islands, Japan

The deep-sea cardinalfish Epigonus glossodontus Gon, 1985, previously known only from the Hawaiian Islands, was observed on steep seafloors surrounding Kitadaito and Minamidaito islands, both being oceanic islands belonging to the Daito Islands, Japan in the northwestern Pacific. Sparse populations were mainly observed at depths of 340–588 m, around or within small caves, fissures, and recesses. A glossy bluish-green body color with black-margined scales was revealed by the field observations, the glossy color fading immediately after death. Its Japanese name is "ホラアナヒスイヤセムツ"(Horaanahisui-yasemutsu, meaning "cave jade deep-sea cardinalfish").

Mao Sato, Shohei Ito, Yoshihiro Fujiwara, Keita Koeda(2025). “First northwestern Pacific records of the deep-sea cardinalfish Epigonus glossodontus (Teleostei, Epigonidae) from the Daito Islands, Japan” Zookeys 1231:1-10 DOI: 10.3897/zookeys.1231.136445
University of the Ryukyus Official Website: https://www.u-ryukyu.ac.jp/news/64937/

A New Species of Flabelligena (Annelida: Acrocirridae) from the Western Pacific

We discovered a new species of polychaete worm, Flabelligena daitoensis, belonging to the family Acrocirridae. This species is the first to be described from the Pacific Ocean. This species inhabits sandy environments at depths of 644 to 774 meters. The polychaete genus Flabelligena has previously been described from the Atlantic, Mediterranean, Indian, and Antarctic oceans.
The specific name daitoensis is derived from the fact that this species was first discovered near Minamidaito Island. Its Japanese name is "ダイトウヒメクマノアシツキ" (Daito-hime-kumanoashitsuki).

Naoto Jimi, Natsumi Hookabe, Shoki Shiraki, Hiroyuki Yokooka, Sau Pinn Woo, Shinji Tsuchida, and Yoshihiro Fujiwara (2024). “A New Species of Flabelligena (Annelida: Acrocirridae) from the Western Pacific." Species Diversity, 29(2), 415–421. DOI: 10.12782/specdiv.29.415

Presentations

Bergman LA, Koeda K, Reimer JD, Sentoku A, Chris M, Yokooka H, Sato M, Bacharo KBB, Tsuchida S, Fujiwara Y (2025) Diversity across the Philippine Sea: benthic megafauna community composition across four ridges in southern Japan. 17th Deep-Sea Biology Symposium
Received the Early-Career Research Award

Bergman LA, Koeda K, Reimer JD, Sentoku A, Yokooka H, Sato M, Bacharo KBB, Tsuchida S, Fujiwara Y (2025) Examining benthic megafauna community composition across four ridges in the Philippine Sea. JAMSTEC International Day 2025

Hookabe N, Fujiwara Y (2025) Ribbon worms from hydrothermal vent fields and seamounts. 17th Deep-Sea Biology Symposium
Received the Early-Career Research Award

Bacharo KBB, Lalas JA, Hakim AA, Fourreau CHL, Kise H, Sentoku A, Yokooka H, Hookabe N, Horowitz J, Tsuchida S, Fujiwara Y, Reimer JD. Nippon’s marine jewels: Preliminary findings on black corals (Antipatharia) of southern Japan. The 27th Annual Meeting of the Japanese Coral Reef Society

Bacharo KBB, Villareal K, Kise H, Sentoku A, Yokooka H, Horowitz J, Hookabe N, Tsuchida S, Fujiwara Y, Reimer JD (2025) Illuminating the diversity of deep-sea anthozoans found in selected sites of the Northwestern Pacific. 17th Deep-Sea Biology Symposium

Bacharo KBB, Villareal K, Monroy MPM, Kise H, Sentoku A, Yokooka H, Hookabe N, Horowitz J, Tsuchida S, Fujiwara Y, Reimer JD (2025) Diversity and distribution of anthozoan specimens collected during the 2020-2024 JAMSTEC expeditions in the northwestern Pacific. Ocean and Earth Symposium 2024

Fujiwara Y, Kawato M, Yoshida T, Tsuchida S, Hookabe N, Bergman L, Koeda K, Sentoku A, Reimer JD, Bacharo, KBB, Jimi N, Bessho-Uehara M, Yamanaka T, Shiraki S, Sato M, Kise H, Yamaki A, Ohno A, Yokooka H, Ito S, Mitsufuji K, Koyama Y, Yasuda T, Okamura G, Vendetti Jann, Sugimoto Y, Shinomiya Y, Tun HA, Fujioka R (2025) Overview of KM24-03 Leg 2 Cruise. Ocean and Earth Symposium 2024 (in Japanese)

Fujiwara Y (2024) Introduction to Deep-Sea Biology. Special Lecture on Life Sciences. Aoyama Gakuin University. (in Japanese)

Koeda K, Sato M, Ito S, Ohno A, Bergman L, Tsuchida S, Fujiwara Y (2024) The fish fauna of deep-sea karst in the Daito Islands. The 2024 (59th) Annual Meeting of the Ichthyological Society of Japan (in Japanese)

Misato Sako, Yoshihiro Fujiwara, Naoto Jimi (2024) An undescribed species of Dendronephthya (Cnidaria, Octocorallia) from Kita-Koho Seamount. Annual Meeting of Plankton and Benthos Society of Japan 2024

Newsletter

Bacharo KBB, Bergman LA, Kise H, Sentoku A, Yokooka H, Ohno A, Tsuchida S, Fujiwara Y, Reimer JD. (2024). JAMSTEC KM24-03 (Leg 2) Deep-Sea Cruise: Report on the cnidarians of the Daito Islands, Philippine Sea. Deep Sea Life, 23: 11-12.

Vendetti J (2024) Dispatches from the D-ARK: Follow Curator of Malacology Jann Vendetti with updates from an expedition into the deep sea caves around Japan's Minami-Daito Island. National History Museum Los Angeles County. https://nhm.org/stories/deep-sea-caves-expedition-japan

Exhibitions / Events

JAMSTEC, Enoshima Aquarium (2025) [Live Stream] New Species Discovered! Exploring the Mysterious Deep-Sea Caves "D-ARK". Enoshima Aquarium
JAMSTEC official YouTube chennel／Niconico Live Streaming

Yamaki A, Ito S, Koeda K, Kawato M, Bergman L, Narushima H, Fujiwara Y (2025) Live coverage of underwater drone survey ~ Off the coast of Enoshima ~ Vol.9 D-ARK Special. Enoshima Aquarium (in Japanese)

Fujiwara Y (2025) Special lecture “D-ARK”. Enoshima Aquarium (in Japanese)

Ito S (2025) Underwater drone piloting experience. Enoshima Aquarium (in Japanese)

Enoshima Aquarium (2024–2025) Special exhibition “Enosui Deep-sea exhibition - 200% Deepness-”. Enoshima Aquarium

Enoshima Aquarium (2024) Aquarium exhibit: "Display of deep-sea creatures collected at D-ARK". Enoshima Aquarium

SNS / Mass media

Enosui cruise diary (in Japanese)

D-ARK cruise (1) April 27th: D-ARK departs for unknown waters
D-ARK cruise (2) April 29th: Finally Arrived! Minamidaito Island
D-ARK cruise (3) April 30th and May 1st: Two Underwater Robots Launch!
D-ARK cruise (4) May 2nd, May 3rd Mini ROV, Baited camera, fishing collection, CTD water sampling
D-ARK cruise (5) May 4th, May 5th Endoscopic camera, CTD, Baited camera again
D-ARK cruise (6) May 6th and May 7th Two caves
D-ARK cruise (7) May 8th and May 9th: Enthusiastic fishing expeditions and cave exploration
D-ARK Voyage (8) May 10th and May 11th: Transition: D-ARK's survey for this year ends safely, and we head to the Kyushu-Palau Ridge.

JAMSTEC Official SNS (in Japanese)

• Ocean shot Project “D-ARK（Deep-sea Archaic Refugia in Karst）” Kicks Off!
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• D-ARK Press (1) Large deep-sea cave discovered during first cruise!
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• D-ARK Press (1) Large deep-sea cave discovered during first cruise! video
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• D-ARK Press (2) New Deep-Sea Exhibit Now Open at Enoshima Aquarium!
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• D-ARK Press (3) D-ARK’s First New Species! Paper on “Daito-hime-
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• D-ARK Press (4) “Deep-Sea Exhibition” Now Showing at Enoshima Aquarium!
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• JAMSTEC × Enoshima Aquarium Live Stream Promo #1
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• JAMSTEC × Enoshima Aquarium Live Stream Promo #2
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• D-ARK Press (5) Japan’s First Record! Paper on “Horaanahisui-yasemutsu” Published!
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Darwin’s Amazing Animals Official X “exclusive coverage of the research cruise conducted in the waters around Minamidaito Island” (in Japanese)

Special drama " Darwin’s Amazing Animals is coming!?", August 20, 2024. NHK TV

Award

AORI Director’s Award　“Challenging the Deep-Sea Caves!” (2025) Photo Contest, Ocean and Earth Symposium 2024