Research publication and activity

The Galapagos Marine Reserve is the only known place in the world that mature female whale sharks migrate to. Most of these females are believed to be pregnant. Okinawa Churashima Foundation has collaborated with the Galapagos Whale Shark Project (Ecuador), Universidad San Francisco de Quito USFQ (Ecuador), Galápagos National Park (Ecuador), Georgia Aquarium (USA), Galapagos Conservation Trust (UK) and Marine Megafauna Foundation (USA), in conducting field research to shed light on the reproduction ecology of whale sharks. The methods developed by Okinawa Churaumi Aquarium to monitor the health of our captive large elasmobranchs, such as conducting underwater ultrasonography and blood sampling were used to study wild whale sharks in the ocean. As a result, for the first time in the world, researchers detected ovarian follicles (egg precursors) with diameters from 28.5mm to 83.6mm in two whale sharks.

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Shark intestines have a very unusual structure. From the outside they are tube-shaped but inside they have a spiral-shaped structure. The reason for this spiral structure is not completely clear.
Recently, we discovered a possible answer to this mystery. By using ultrasound, we could view the movement of the intestine while Jinta, the aquarium’s whale shark, was digesting. It showed Jinta twisting the intestine during digestion. It always twists to the right which winds the spiral structure tighter.
Like wringing water out from a cloth, it suggests that sharks twist their intestine to help excrete feces from its anus.

This new knowledge was possible through the rearing of the whale shark at the aquarium. We will continue to study reared animals to further contribute to our knowledge of organisms.

【Title】Narrowing, twisting, and undulating: Complicated movement in shark spiral intestine inferred using ultrasound
【Authors】Taketeru Tomita, Kiyomi Murakumo, Rui Matsumoto (Bold letters: the Churashima Foundation Staff)
【Journal】Zoology

Whale sharks filter feed for zooplankton at the ocean's surface. Researchers have tracked and logged whale shark movements with data logging devices, and found that whale sharks also dive down to the dark deep sea. As whale sharks live in both well-lit surface waters and dark depths, how do their eyes manage this challenge?
Researchers from Okinawa Churaumi Aquarium collaborated with research teams led by Professor Shigehiro Kuraku of Research Organization of Information and Systems National Institute of Genetics (Team leader of RIKEN) and Professor Mitsumasa Koyanagi of Osaka Metropolitan University, to research how genetics influences the vision of whale sharks.

【Title】Whale shark rhodopsin adapted to deep sea lifestyle by a substitution associated with human disease
【Authors】Kazuaki Yamaguchi, Mitsumasa Koyanagi, Keiichi Sato, Akihisa Terakita, Shigehiro Kuraku

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The symbiotic relationship between species of anemonefish and sea anemones is well known. This study used genetic analysis to reveal phylogenetic differentiation in the host sea anemones. The results allow a deeper understanding of the interactions between sea anemones and anemonefish, including differences in toxicity of the host anemones.

【Authors】Rio Kashimoto, Miyako Tanimoto, Saori Miura, Noriyuki Satoh, Vincent Laudet, Konstantin Khalturin (Bold letters: the Churashima Foundation Staff)
This study was conducted with staff from the Churashima Foundation in collaboration with the Okinawa Institute of Science and Technology.
【Title】Transcriptomes of Giant Sea Anemones from Okinawa as a Tool for Understanding Their Phylogeny and Symbiotic Relationships with Anemonefish
【Journal】Zoological Science

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In recent years, humpback whale watching has become increasingly popular in Japan. In some areas, businesses have started to offer whale swim tours. Overseas studies suggest that an expanding tourism industry may lead to disturbance or stress to the animals, which can have long-term impacts. Long term impacts can include having fewer calves, decreased life span, and/or abandoning an area. It is important to establish rules to help minimize the impact on cetaceans while maintaining a sustainable tourism industry.
The Okinawa Churashima Foundation Research Center, with the aims of humpback whale conservation and sustainable tourism, has collaborated with Dr. Stephanie Stack of the Pacific Whale Foundation. Dr. Stack and her team have extensive experience in many places in the world, studying the impact of human activities, including tourism, on cetaceans. By working with people in related industries, we are better able to study and evaluate the effects of whale watching and swim tours. We will continue to study this issue while collaborating with related industries and research institutions in Japan and overseas!

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The first thing you notice about the thread pipefish is that it is tiny. The research group at the Okinawa Churashima Foundation collected an extremely small fish at a depth of 8 meters off the coast of Motobu. The specimen was confirmed to be Kyonemichthys rumengani, a species of pipefish that had not been found in Japanese waters. Some scuba divers thought that this species was found in Japan, however, this was the first confirmed specimen. Observations of its structure and genetics, reveal it is closely related to the Urocampuspipefishes found in inland bays and brackish waters. Its Japanese common name is proposed to be hariyouji, because it resembles a needle.

【Authors】Nozomi Hanahara, Miyako Tanimoto,Naoki Shirakawa （Bold letters: the Churashima Foundation Staff）
【Title】Kyonemichthys rumengani (Teleostei: Syngnathidae) is sister taxon to the pipefish genus Urocampus: genetic and morphological evidence
【Journal】Species Diversity　DOI: 10.12782/specdiv.27.293

Frogfish use their limbs-like pectoral and pelvic fins to “walk” around the sea floor. There are over 50 species of frogfish around the world. Most frogfish are marine species, however the brackishwater frogfish is unusual in that is found in brackishwater and freshwater. This species was confirmed in the tropics south of Taiwan. However, the authors have confirmed this species to also inhabit near Okinawa Island and Yakushima Island. These were the first records of the species in Japanese waters. Its triangular head is like a clown’s hat which led to its Japanese name piero-kaeruanko. Okinawa Churaumi Aquarium successfully reared and exhibited the individual collected in a northern Okinawan river.

【Authors】Kei Miyamoto, Hidetoshi Wada, Tadanosuke Nagasaka, Hauraka Takano, Hiroyuki Motomura, and Hiroshi Senou (Bold letters: the Churashima Foundation Staff)
【Title】First Japanese records of Antennarius biocellatus (Antennariidae) from Okinawa-jima and Yaku-shima island
【Journal】Ichthy, Natural History of Fishes of Japan

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Male humpback whales produce complex sounds called songs. These songs are heard from the end of the feeding season and throughout the breeding season. Singing songs is thought to be related to breeding.
In the breeding grounds, males form competitive groups searching for females to mate with. These groups usually form just after sunrise, and they remain together during the day. In the afternoon and evening the groups reduce in size, and then break up.
Researchers from the Okinawa Churashima Foundation set up a fixed underwater microphone off the Motobu Peninsula in Okinawa Prefecture. The device recorded 24 hours a day, for 2 weeks during the breeding season. The recordings showed that whales sang more during the night than during the day. Observation surveys conducted from boats, indicated that males only sing when alone.
These results suggest that perhaps song activity is reduced during the day as male humpback whales are more likely to be in groups, and there are fewer males alone. However, male humpback whales may also be moving to different areas from day to night. To study this, researchers will place several fixed underwater microphones further offshore and continue with their research.

【Authors】Nozomi Kobayashi, Haruna Okabe, Naoto Higashi, Hirokazu Miyahara H, Senzo Uchida　(Bold letters: the Churashima Foundation Staff)
【Title】Diel patterns in singing activity of humpback whales in a winter breeding area in Okinawan (Ryukyuan) waters
【Journal】Marine Mammal Science　　DOI: 10.1111/mms.12790

When conducting environmental DNA surveys to determine what species are in the water, it is necessary to filter the water that contains DNA. Previously, expensive equipment and tools were needed to do this. We developed a system, powered by gravity, to filter the water using a rubber hose and a 3D printed adapter. With this inexpensive and compact tool, we can filter outdoors without electricity. It is hoped that this will enable more environmental DNA surveys to be undertaken. Detailed information is in the published scientific paper, and several scientists are now using this system for their research.

【Authors】Shin-ichiro Oka, Masaki Miya, Tetsuya Sado (Bold letters: the Churashima Foundation Staff)
【Title】Gravity filtration of environmental DNA: A simple, fast, and power-free method
【Journal】Methods　X

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Sea pens are marine cnidarians that live in both shallow waters and deep seas around the world. They have tiny crystal-like internal structures called sclerites that vary in shape.
In our research, we found that these sclerites have variations related to the depth at which particular sea pens are living. A distinct evolutionary pattern was discovered. A common ancestor of sea pens, found at depths below 400 meters, has different plate and needle shaped sclerites to those sea pens at shallower depths.

【Authors】Kushida Y, Imahara Y, Wee HB, Fernandez-Silva I, Fromont J, Gomez O, Wilson N, Kimura T, Tsuchida S, Fujiwara Y, Higashiji T, Nakano H, Kohtsuka H, Iguchi A, Reimer JD.
(Bold letters：Staff members of Okinawa Churashima Foundation)
※This research was an international collaboration between research teams that included Okinawa Churaumi Aquarium, the University of Rissho, and the University of the Ryukyus.
【Title】Exploring the trends of adaptation and evolution of sclerites with regards to habitat depth in sea pens.
【Journal】Peer J

Most squid and cuttlefish swim, but the paintpot cuttlefish is unusual in that it prefers to walk. It uses its ventral arms like forelimbs, and its body’s mantle like rear legs to walk.
We observed the cuttlefish’s walking behavior and morphology to better understand the mechanism by which the mantle is used for walking.

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Japan is the main nesting ground for loggerhead turtles in the Northern Pacific. Egg laying takes place from Honshu down to the Ryukyu Islands, and is centered on Yakushima Island. The number of egg-laying loggerhead turtles has declined since 1990. They are threatened with extinction, and are therefore listed as an endangered species on the red list of the IUCN (International Union for Conservation of Nature). 
Since 1994, the staff at Okinawa Churaumi Aquarium, have studied the reproduction and physiological ecology of loggerhead turtles through captive breeding, with the goal of conservation.
Discovering the age of sexual maturation in sea turtles is extremely difficult, and the most effective method is through captive breeding. At our facility, we are rearing a female loggerhead turtle that was born at the aquarium in 1995. Each year we conduct an ultrasound scan of her ovaries, and measure the length of her carapace. The results showed that a reared loggerhead turtle’s sextual maturation begins at around 18 – 22 years old. These results, including the successful breeding of a third successive generation of loggerhead turtle were published in the Herpetological Review, a journal published by the American Society for the Study of Amphibians and Reptiles.

【Author】Shingo Fukada, Isao Kawazu, Ken Maeda, Takahiro Kobuchi, Masae Makabe, Masakatsu Kino, Konomi Maeda, Mariko Omata, Takahide Sasai 
【Title】Breeding Success of a Captive F2 Generation of Loggerhead Sea Turtle in Okinawa Churaumi Aquarium
【Journal】Herpetological Review

Noninvasive and stress-free ultrasound scans were successfully conducted to determine the spawning cycle of an oviparous catshark. The ultrasound scans were conducted every day on the same catshark for approximately six months.

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【Date awarded】May 27th, 2022
【Authors】Sayaka Seto, Suguru Higa, Isao Kawazu
【Title】Suppression of aggressive behavior in a captive pygmy killer whale using behavior modification
【Journal】Journal of Japanese Association of Zoos and Aquariums 66 (3), 42?50, 2021. (in Japanese with English abstract)

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The Indo-Pacific bottlenose dolphin is a small species of toothed whale. They are found in warm coastal areas from the Indian Ocean to the Pacific Ocean.Okinawa Churaumi Aquarium is the only place in Japan that rears them. Kindai University and the Okinawa Churashima Foundation collaborated and conducted a study on the speed of digestion in a reared Indo-Pacific bottlenose dolphin. An Indo-Pacific bottlenose dolphin was given food with a capsule of red carmine dye. Researchers then recorded when this red dye first appeared in the dolphin’s feces. The results showed that it took an average of 254 ± 20.4 minutes for the dye to be first excreted. This suggests that Indo-Pacific bottlenose dolphins excrete within 4 to 6 hours from feeding. The results from this study provide valuable information, allowing a better understanding of feeding and behavior of wild Indo-Pacific bottlenose dolphins.

【Authors】Rikiya Takahashi, Nozomi Kobayashi, Suguru Higa, Mai Sakai (Bold letters: Staff members of Okinawa Churashima Foundation)
【Title】The Passage Time of Prey Through the Digestive Tract of Indo-Pacific Bottlenose Dolphin (Tursiops aduncus)
【Journal】Japanese Journal of Zoo and Wildlife Medicine

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Around the world, captive breeding programs are conducted to protect endangered species such as the hawksbill turtles. However, when rearing hawksbill turtles in captivity, frequent fighting between the turtles leads to injuries and possibly serious infections. Okinawa Churashima Foundation researchers monitored the concentrations of corticosterone in the blood of the turtles, their aggressive behaviors, and resting behaviors. Monitoring was done when the turtles were (1) alone (2) with another turtle with rocks (3) with another turtle without rocks. This was done to evaluate whether the aggressive behavior of captive hawksbill turtles could be controlled. The results showed that the presence of rocks reduced aggressive behaviors, and increased resting. By placing rocks in the tank, it will help reduce the hawksbill turtles from being aggressive with others.

【Authors】Isao Kawazu, Miwa Suzuki, Konomi Maeda (Bold letters: Staff members of Okinawa Churashima Foundation)
【Title】Rock installation reduces aggressive behavior in captive hawksbill turtles
【Journal】Current Herpetology

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Okinawa Churashima Foundation has collaborated with Diagence, Osaka University and Keio University to optimize the identification process of humpback whale tail fins, and have successfully developed an AI automatic identification system for humpback whales based on their tail fins.
With the development of this system, we can expect a rapid improvement in efficiency compared to manually identifying tail fins. Okinawa Churashima Foundation will utilize this system and work together with domestic and international research institutes with the aim of shedding light on the population structure and the seasonal migration routes of humpback whales in the North Pacific Ocean.

【Authors】Yoshikawa T, Hida M, Lee C, Okabe H, Kobayashi N, Ozawa S, Saito H, Kan M, Date S, Shimojo S (Bold letters: Staff members of Okinawa Churashima Foundation).
【Title】Identification of over one thousand individual wild humpback whales using fluke photos.
【Journal(Conference proceedings)】Proceedings of the 17th International Joint Conference on Computer Vision, Imaging and Computer Graphics Theory and Applications. 4: ISBN 978-989-758-555-5, ISSN 2184-4321, 957-967.

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In February 2020, a different sea bream was caught off the coast of Yomitan Village on Okinawa Main Island. A research team, including staff from the Churashima Foundation, determined it was a rare Japanese blue-spotted seabream (Amamiichthys matsubarai), previously only found near Amami Oshima Island.

【Authors】Fukuchi I, Miyamoto K, Tanaka F, Tachihara K　(Bold letters: Staff members of Okinawa Churashima Foundation).
【Title】Record of a Japanese blue-spotted seabream (Amamiichthys matsubarai) off the coast of Okinawa Main Island and observation of its reproductive organs.
【Journal】Ichyhy

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Wild pygmy killer whales are aggressive toward other dolphins, and this is the same in a captive environment. The pygmy killer whale showed frequent aggression toward other dolphins in the tank or the trainers. Social behaviors, such as playing and swimming with others, were also seen less. To encourage more social behavior and reduce aggression, Okinawa Churaumi Aquarium used behavior modification in a similar way to human psychotherapy. This led to an increase in social behavior and significantly reduced aggression. This was done by repeatedly providing a reward of toys, but only when the dolphin showed no signs of aggression.

【Authors】Sayaka Seto, Suguru Higa, Isao Kawazu
【Title】Suppression of aggressive behavior in a captive pygmy killer whale using behavior modification
【Journal】Journal of Japanese Association of Zoos and Aquariums (in Japanese with English abstract)

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Hydrophis stokesii was collected in the coastal water of Okinawajima Island on 30 March 2021. This is the first record of the species from Japanese waters, extending its known range of occurrence toward east-northeast by more than 900 km from southwest of Taiwan.

【Authors】Takahide Sasai,Takumi Yamamoto, Shinichiro Oka, Mamoru Toda (Bold letters: Staff members of Okinawa Churashima Foundation)
【Title】Addition of the Sea Snake, Hydrophis stokesii (Squamata: E lapidae) to the Herpetofauna of Japan
【Journal】Current Herpetology

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Marine debris is a global problem and has been shown to affect many marine animals. Okinawa Churaumi Aquarium managed by the Okinawa Churaumi Foundation dissected the gastrointestinal tracts of 484 stranded, dead sea turtles from 1990 to 2019 to determine the extent of marine debris ingestion by sea turtles around Okinawa Island, through analysis of frequency and type of marine debris ingested.

【Authors】Takahide Sasai, Masakatsu Kino, Kei Miyamoto, Haruna Okabe, Konomi Maeda, Shingo Fukada,
Ken Maeda, Nozomi Kobayashi, Takahiro Kobuchi, Masae Makabe, Isao Kawazu
【Title】Evaluation of Marine Debris Ingestion in Sea Turtles around Okinawa Island, Japan.
【Journal】Marine Turtle Newsletter

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The coconut crab is the largest terrestrial crustacean. It inhabits tropical and subtropical zones of the Indo-Pacific. The global population is decreasing due to overhunting and habitat destruction.
From 2006 to 2019, the Okinawa Churashima Foundation conducted surveys of the coconut crabs that live within Ocean Expo Park. The accumulated data from the 14-year study, including 350 surveys, revealed the rate of growth of coconut crabs and their population size. 506 datasets were obtained from mark-recapture surveys.

【Authors】Shin-ichiro Oka、Koji Tokutake、Tadanobu Inoue （Names in bold : Churashima Foundation Staff）
【Title】Growth analysis and population size estimation of coconut crabs based on a large recapture dataset
【Journal】Crustacean Research　（DOI：10.18353/crustacea.50.0_145）

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Pantropical spotted dolphins inhabit the tropical and subtropical seas globally, but few have been reared in aquariums. The world’s first successful captive reproduction of a pantropical spotted dolphin took place on March 31st, 2017 at Okinawa Churaumi Aquarium.
From this successful reproduction we knew the length of gestation was 352 days, and we knew how the levels of the female hormone progesterone changed during gestation. It took 9.5 hours for the mother to deliver the baby dolphin, and nursing began 4 hours after birth.
The results from this study can contribute to reproduction programs of pantropical spotted dolphins.

【Authors】Shunya Ikeshima, Suguru Higa, Yuuta Mitani, Mariko Omata, Nozomi Kobayashi, Keiichi Ueda, Isao Kawazu
【Title】First Observation of Pregnancy and Parturition in a Captive Pantropical Spotted Dolphin (Stenella attenuata)
【Journal】Mammal Study

WHALE SHARKS – Biology, Ecology, and Conservation, a new book with the latest research on the ecology and conservation of whale sharks, has been published by CRC Press in America.
In several of the book’s chapters, staff members of Okinawa Churaumi Aquarium (managed and operated by the Okinawa Churaumi Foundation), introduce the results of their research and surveys on whale shark ecology. Whale shark health management at our aquarium, including underwater ultrasound imaging and blood analysis, has resulted in a better understanding of whale shark physiology and reproduction. This new information on whale shark ecology can help with the conservation of this species. The chapters in this book look in-depth at all aspects　of whale shark biology including growth, metabolism, migration, ecology, behavior, physiology, and functional anatomy. This book can be read by the public, researchers, conservationists, and resource managers. Okinawa Churaumi Aquarium will continue to rear whale sharks as we conduct research and surveys, while cooperating with research facilities around the world to further shed light on the ecology of whale sharks.

【Chapter Authors】Alistair D.M. Dove, Simon J. Pierce
○Chapter 2：Whale Shark Reproduction, Growth, and Demography.
S.J. Pierce, S.A. Pardo, C.A. Rohner, R. Matsumoto, K. Murakumo, R. Nozu, A.D.M. Dove. (Names in bold : Churashima Foundation Staff)

○Chapter 9：Lessons from Care of Whale Sharks in Public Aquariums.
A.D.M. Dove, R. Matsumoto, C. Schreiber, K. Murakumo, C. Coco, M. Yanagisawa, T. Clauss, L. Hoopes, K. Sato.
(Names in bold : Churashima Foundation Staff)

○Chapter13：Outstanding Questions in Whale Shark Research and Conservation.
Written by all authors (Including Foundation Staff)

【Title】WHALE SHARKS
Biology, Ecology, and Conservation

【Publisher】CRC Press

Link to book

On the 6th of August 2021, a dead whale was found on the shoreline of Chatan Town in Okinawa Prefecture. The dead whale was examined to determine its appearance and skeletal structure, then based on previous research conducted by the Churashima Foundation (Kobayashi et al. 2021a; 2021b), it was identified as a Longman’s beaked whale. This is a rare whale with only 20 recorded strandings in the world. This individual was a young male approximately 5 meters in length. It is the 5th case of this species stranding in Japan. Previously there had been cases in Hokkaido, Kagoshima, and twice in Okinawa (2011 and 2020).

There is limited knowledge on the habitat of the Longman’s beaked whale, but there have now been several strandings in Okinawa. The Okinawa Churashima Foundation plans to work together with Chatan Town, Japanese and international research facilities to carry out further studies which include analysis of stomach contents and DNA.

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On November 26th, 2020, a dead sperm whale was found on the reef just north of the taxiway at Naha Airport. Sperm whales are widely distributed across the world’s oceans. Males can reach 19 meters in length, and females can reach 12 meters in length.

With the deceased whale, we undertook detailed observations before burying the whale carcass on the airport grounds. Dissection and disposal were difficult, due to operational restrictions at the airport, limiting the use of heavy equipment immediately after the stranding.

Our foundation cooperated with various parties to conduct detailed surveys of decomposition over two months from discovery to burial of the carcass. The results of this research were presented at the Okinawan area Conference of Land, Infrastructure and Transport in 2021. There had been no previous detailed reports on the results of leaving a whale carcass to decay and its burial. This presentation was given the Award for Excellence (Innovation Category). Our foundation will continue to conduct scientific marine research with the goals of conservation of whales and dolphins, and assisting the local community.

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Hawksbill turtles are distributed throughout the world’s temperate and tropical coral reefs.
The global population of hawksbill turtles has drastically decreased due to the loss of nesting grounds and fishing bycatch. It is classified as a Critically Endangered (CR) species on the IUCN Red List (International Union for Conservation of Nature) and is threatened with extinction.
Okinawa Churaumi Aquarium managed by the Okinawa Churaumi Foundation is working together with conservationists on Okinawa Island. Research on sea turtle nesting and reproductive ecology was conducted from 1987 to 2017.
July is the height of the hawksbill turtle nesting season. 28 hawksbill turtle nests were confirmed at 11 Okinawa beaches, including Ogimi Village and Motobu Town.
As the population of hawksbill turtles in Okinawa is small, conservation efforts still need to be strengthened, including regulations on legal capture, and improved protection of the sandy beaches where nesting occurs.

【Authors】Isao Kawazu, Kunio Komesu, Muneyuki Kayou, Takashi Inoue,Masakatsu Kino, Konomi Maeda, Shingo Fukada.(Bold letters: Staff members of Okinawa Churashima Foundation)
【Title】Nesting and reproductive ecology of the hawksbill turtle, Eretmochelys imbricata (Reptilia: Cheloniidae), on Okinawajima Island, Japan
【Journal】The Biological magazine Okinawa

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Whale sharks are the world’s largest fish. They can reach over 12 meters in length. Whale sharks mainly eat plankton, and their feeding behavior is complex. One distinctive feature is vertical feeding. When feeding, a whale shark swims vertically with its mouth open so it can suck in plankton floating on the surface.

One mystery about this vertical feeding is that, in general, sharks are denser than water, but whale sharks do not sink during vertical feeding. Whale sharks can even stop moving their tail, but still remain neutrally buoyant while vertical feeding at the surface.

In this research, we estimated the body volume and density of two whale shark reared at the Okinawa Churaumi Aquarium to calculate their weight within the water. Based on the results, we hypothesize that whale sharks suck in air during vertical feeding, and that this extra air in the mouth and gill chamber allow whale sharks to maintain buoyancy. By maintaining buoyancy with sucked air, the whale sharks may save energy during feeding.

【Authors】Taketeru Tomita, Minoru Toda, Kiyomi Murakumo, Kei Miyamoto, Rui Matsumoto,
Keiichi Ueda, Keiichi Sato　
【Title】Volume of the whale shark and their mechanism of vertical feeding
【Journal】Zoology

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During summer, humpback whales in the North Pacific feed in high latitude regions such as the waters of Russia and Alaska. In winter, they breed, give birth, and raise their young in the waters of Okinawa and the Philippines. Individual humpback whales can be identified by the patterns on their tail fins. The Okinawa Churashima Foundation, in collaboration with a research organization in the Philippines (BALYENA.ORG) conducted surveys and identified individual whales. The results shed light on the interchange of humpback whales between Okinawa and the Philippines, and were published in international journals.

【Authors】Acebes J. M. V, Okabe H, Kobayashi N,Nakagun S, Sakamoto T, Hirney B, Higashi N, Uchida S. (Bold letters: Staff members of Okinawa Churashima Foundation)　
【Title】Interchange and movements of humpback whales (Megaptera novaeangliae) between western North Pacific winter breeding grounds in northern Luzon, Philippines and Okinawa, Japan
【Journal】Journal of cetacean research and management

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On July 30th, 2011, a rare species of whale was found deceased and stranded on a beach of Ukibaru Island, Uruma City in Okinawa. Research teams from the Okinawa Churashima Foundation and the Japan Fishery Research and Education Agency collaborated to analyze its appearance, bone structure, and DNA (genetic information) and the results showed that the species was a Longman’s beaked whale, which is a very rare type of whale. The individual was a young male 4.8 meters in length. It was the third specimen found in Japan. Previously an individual was found in Kagoshima, and another in Hokkaido. This was the first reported case of this species stranding in Okinawa. The new information about the species was published in an international journal. We recreated the entire skeleton of this individual and it is currently on display in the Churaumi Plaza at the Okinawa Churaumi Aquarium.

【Authors】Nozomi Kobayashi, Koji Tokutake, Hideyoshi Yoshida, Haruna Okabe, Kei Miyamoto, Haruka Ito, Naoto Higashi, Shingo Fukada, Kei Yamazaki, Suguru Higa, Isao Kawazu, Keiichi Ueda (Bold letters: Staff members of Okinawa Churashima Foundation)
【Title】The First Stranding Record of Longman’s Beaked Whale (Indopacetus pacificus) in Okinawa, Japan.
【Journal】Aquatic Mammals

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Coconut crabs are the world’s largest terrestrial crustaceans. Their claws can produce a pinching force nearly 100 times the crab’s weight. These extreme forces require the crab to have an exceptionally strong structure. The National Institute for Materials Science and the Okinawa Churashima Foundation collaborated to reveal the microstructures of a coconut crab’s claws using cutting-edge technology.

【Authors】Tadanobu INOUE, Shin-ichiro OKA, Toru HARA　
【Title】Three-dimensional microstructure of robust claw of coconut crab, one of the largest terrestrial crustaceans
【Journal】Materials & Design

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Weatherfish Misgurnus sp. OK is a species endemic to the Ryukyu Islands. In recent years, there has been a sharp decline in its population due to habitat degradation. In 2020, it was designated as one of Okinawa’s endangered species. This prohibits its collection without authorization. Okinawa Churashima Foundation, along with researchers from the University of the Ryukyus, Okinawa Institute of Science and Technology Graduate University (OIST), and Nago Museum, conducted a survey on the genetic diversity of wild populations of this species.

【Authors】Shin-ichiro OKA、Takahide Sasai、Nozomi Hanahara、 Kei Miyamoto、 Hirozumi Kobayashi、Naofumi Murata、Ken Maeda (Bold letters: Staff members of Okinawa Churashima Foundation)
【Title】Genetic traits of the weatherfish Misgurnus sp. OK on the Okinawa Islands, southern Japan
【Journal】Fauna Ryukyuana

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On July 13th, 2020, a deceased newborn Longman’s beaked whale was found stranded on a Miyako Island beach in Okinawa Prefecture. This was reported in the scientific journal Marine Biodiversity Records. The Longman’s beaked whale is an extremely rare species of whale with very few cases observed worldwide. Previous research had estimated its maximum body length at around 6 meters, however, the body length of newborns was not known. The newborn Longman’s beaked whale found stranded on Miyako Island was a female, 2.35 meters in length, with fetal folds on the surface of its body. These fetal folds are only seen for the first few weeks after birth, and are formed on the skin due to the calf being curled in its mother’s womb. Due to the presence of visible fetal folds, it is thought the whale was less than a few weeks old. The discovery of the newborn suggests there is a high possibility of Longman’s beaked whales breeding and giving birth in Okinawan waters. This discovery provides extremely important information to better understand the ecology of this species.

【Authors】Nozomi Kobayashi, Sachie Ozawa, Nozomi Hanahara, Koji Tokutake, Takaaki Kaneshi, Ken Inoue, Haruna Okabe, Kei Miyamoto, Keiichi Ueda (Bold letters: Staff members of Okinawa Churashima Foundation)
【Title of Paper】The first record of a Longman’s beaked whale (Indopacetus pacificus) newborn neonate found on Miyako Island, Okinawa, Japan
【Title of Journal】Marine Biodiversity Records

For more details, please click here.

Okinawa Churashima Foundation has successfully identified several species of goby using DNA analysis. Gobies are an extremely diverse family of fish made up of over 2000 species. It is extremely difficult to determine the species of a goby larva only by their appearance, and this has restricted research.
In this study, genetic (DNA) analysis was conducted on specimens of goby larvae. We succeeded in identifying 13 species, including 8 species whose larval morphology had not yet been clarified. Furthermore, we showed an easier method to genetically analyze formalin-fixed specimens under certain conditions. This method will contribute further to a better understanding of the ecology of gobies and their larvae.

【Authors】Nozomi Hanahara, Kei Miyamoto, Shin‑ichiro Oka
【Title of Paper】Morphological and genetic identification of formalin‑fixed gobioid larvae and description of postflexion larvae of Paragunnellichthys sp. and Ctenogobiops feroculus
【Title of journal】Ichthyological Research

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The megamouth shark is a mysterious and rare shark species discovered in the 20th Century. It is known to be a filter feeder, however, the exact feeding mechanism is unclear. One group of researchers had hypothesized that the prominent white band on its upper jaw was a bioluminescent lure. Another group hypothesized that the white band reflected light emitted from bioluminescent prey. Neither theory was proven. This study, conducted in collaboration with a research team from the University of Louvain in Belgium, reexamined the theories on bioluminescence of megamouth sharks.

Researchers used different histological approaches (histological sections, fluorescent in situ hybridization (FISH) and scanning electron microscopy) and spectrophotometry. Researchers determined that the megamouth shark does not have functioning bioluminescent organs. Various forms of tiny placoid scales were found in the white band and in its mouth, which may reflect the bioluminescence produced by its planktonic prey.

Previous theories of the megamouth showing bioluminescence are probably due to the megamouth’s placoid scales reflecting the light from its bioluminescent planktonic prey, or even reflecting scuba diving lights.

【Authors】Laurent Duchatelet, Victoria C. Moris, Taketeru Tomita, Jacques Mahillon, Keiichi Sato, Catherine Behets, Jerome Mallefet（Bold letters: Staff of Okinawa Churaumi Aquari