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Shiro Itoi
Department of Marine Science and Resources, Nihon University, Fujisawa, Kanagawa 252-0880, Japan

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Journal article
Published: 06 July 2021 in Aquatic Toxicology
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Tetrodotoxin (TTX), also known as pufferfish toxin, has been detected in marine edible bivalves worldwide. In this study, several bivalve species, Azumapecten farreri subsp. akazara, Patinopecten yessoensis and Mytilus galloprovincialis, collected from the Pacific side of the northern Japanese Islands, were studied for the accumulation of TTX in the presence of toxic planocerid larvae. LC-MS/MS analysis demonstrated that TTX was detected only in the midgut gland of A. farreri subsp. akazara. Toxic flatworm-specific PCR and direct sequencing of the amplicons showed that the DNA fragments of the Planocera multitentaculata COI gene were detected in the gut contents of the toxified bivalves. The planocerid larvae were also detected in the environmental seawaters. Toxification experiments in the aquarium demonstrated that the mussel M. galloprovincialis was also toxified by feeding on the toxic flatworm larvae. These results suggest that the source of TTX accumulation in edible bivalves is toxic flatworm larvae.

ACS Style

Taiki Okabe; Rion Saito; Kohei Yamamoto; Riku Watanabe; Yoshiki Kaneko; Mutsumi Yanaoka; Seika Furukoshi; Shino Yasukawa; Masaaki Ito; Hikaru Oyama; Rei Suo; Miwa Suzuki; Tomohiro Takatani; Osamu Arakawa; Haruo Sugita; Shiro Itoi. The role of toxic planocerid flatworm larvae on tetrodotoxin accumulation in marine bivalves. Aquatic Toxicology 2021, 237, 105908 .

AMA Style

Taiki Okabe, Rion Saito, Kohei Yamamoto, Riku Watanabe, Yoshiki Kaneko, Mutsumi Yanaoka, Seika Furukoshi, Shino Yasukawa, Masaaki Ito, Hikaru Oyama, Rei Suo, Miwa Suzuki, Tomohiro Takatani, Osamu Arakawa, Haruo Sugita, Shiro Itoi. The role of toxic planocerid flatworm larvae on tetrodotoxin accumulation in marine bivalves. Aquatic Toxicology. 2021; 237 ():105908.

Chicago/Turabian Style

Taiki Okabe; Rion Saito; Kohei Yamamoto; Riku Watanabe; Yoshiki Kaneko; Mutsumi Yanaoka; Seika Furukoshi; Shino Yasukawa; Masaaki Ito; Hikaru Oyama; Rei Suo; Miwa Suzuki; Tomohiro Takatani; Osamu Arakawa; Haruo Sugita; Shiro Itoi. 2021. "The role of toxic planocerid flatworm larvae on tetrodotoxin accumulation in marine bivalves." Aquatic Toxicology 237, no. : 105908.

Journal article
Published: 18 January 2021 in Marine Drugs
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Several polyclad flatworm species are known to contain high levels of tetrodotoxin (TTX), but currently TTX-bearing flatworms seem to be restricted to specific Planocera lineages belonging to the suborder Acotylea. During our ongoing study of flatworm toxins, high concentrations of TTXs were detected for the first time in the flatworm Prosthiostomum trilineatum, suborder Cotylea, from the coastal area of Hayama, Kanagawa, Japan. Toxin levels were investigated by high performance liquid chromatography-tandem mass spectrometry (LC-MS/MS), revealing that this species contains comparable concentrations of toxins as seen in planocerid flatworms such as Planocera multitentaculata. This finding indicated that there may be other species with significant levels of TTXs. The distribution of TTXs among other flatworm species is thus of great interest.

ACS Style

Rei Suo; Maho Kashitani; Hikaru Oyama; Masaatsu Adachi; Ryota Nakahigashi; Ryo Sakakibara; Toshio Nishikawa; Haruo Sugita; Shiro Itoi. First Detection of Tetrodotoxins in the Cotylean Flatworm Prosthiostomum trilineatum. Marine Drugs 2021, 19, 40 .

AMA Style

Rei Suo, Maho Kashitani, Hikaru Oyama, Masaatsu Adachi, Ryota Nakahigashi, Ryo Sakakibara, Toshio Nishikawa, Haruo Sugita, Shiro Itoi. First Detection of Tetrodotoxins in the Cotylean Flatworm Prosthiostomum trilineatum. Marine Drugs. 2021; 19 (1):40.

Chicago/Turabian Style

Rei Suo; Maho Kashitani; Hikaru Oyama; Masaatsu Adachi; Ryota Nakahigashi; Ryo Sakakibara; Toshio Nishikawa; Haruo Sugita; Shiro Itoi. 2021. "First Detection of Tetrodotoxins in the Cotylean Flatworm Prosthiostomum trilineatum." Marine Drugs 19, no. 1: 40.

Original article
Published: 03 June 2020 in Marine Biotechnology
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Oncorhynchus masou, including subspecies of Oncorhynchus masou masou (yamame) and Oncorhynchus masou ishikawae (amago), is one of the salmonid groups impacted by human activity such as dam construction and release of non-native salmonids. In this study, we investigated the genetic structure of O. masou populations in the Sakawa and Sagami Rivers, Japan, by sequencing the mitochondrial control region. We hoped to identify genetically the O. masou populations specific to and originally native to Kanagawa Prefecture, where the two subspecies are thought to be present. The populations found in the upstream tributaries, where there has been no human impact and no upstream migration of fishes, were assumed to be descendants of the local O. masou populations in both river systems, and the morphological features seen here were similar to amago and yamame. However, both populations were genetically related to amago. In addition, only six haplotypes were detected in 315 individuals collected from 20 localities in the two river systems. Furthermore, haplotype diversity and nucleotide diversity of these populations were low, and high Fst values were observed. These results suggest that the population size is restricted and genetic diversity is decreasing in the O. masou populations of the Sakawa and Sagami Rivers.

ACS Style

Taiki Okabe; Naoyuki Suguro; Tomoko Koito; Kento Endo; Haruo Sugita; Shiro Itoi. Genetic and Morphological Characteristics in the Local Population of the Landlocked Salmon Oncorhynchus masou Originally Distributed in Kanagawa Prefecture, Japan. Marine Biotechnology 2020, 22, 812 -823.

AMA Style

Taiki Okabe, Naoyuki Suguro, Tomoko Koito, Kento Endo, Haruo Sugita, Shiro Itoi. Genetic and Morphological Characteristics in the Local Population of the Landlocked Salmon Oncorhynchus masou Originally Distributed in Kanagawa Prefecture, Japan. Marine Biotechnology. 2020; 22 (6):812-823.

Chicago/Turabian Style

Taiki Okabe; Naoyuki Suguro; Tomoko Koito; Kento Endo; Haruo Sugita; Shiro Itoi. 2020. "Genetic and Morphological Characteristics in the Local Population of the Landlocked Salmon Oncorhynchus masou Originally Distributed in Kanagawa Prefecture, Japan." Marine Biotechnology 22, no. 6: 812-823.

Original article
Published: 15 May 2020 in Marine Biotechnology
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Tetrodotoxin (TTX), also known as pufferfish toxin, causes a respiratory disorder by blocking neurotransmission, with voltage-gated sodium channel inhibition on muscle and nerve tissues. The toxin is widely distributed across vertebrates, invertebrates and bacteria. Therefore, it is generally thought that TTX in pufferfish accumulates via the food webs, beginning with marine bacteria as a primary producer. Polyclad flatworms in the genus Planocera are also known to be highly toxic, TTX-bearing organisms. Unlike the case of pufferfish, the source of TTX in these flatworms is unknown. In this study, taxonomical distribution patterns of TTX were investigated for acotylean flatworms from coastal waters using molecular phylogenetic analysis and high performance liquid chromatography-tandem mass spectrometry (LC-MS/MS). A maximum likelihood tree based on the 28S rRNA gene sequence showed that the flatworms belonged to several different lineages among the genera Planocera, Stylochus, Paraplanocera, Discocelis, Notocomplana, Notoplana, Callioplana and Peudostylochus. After LC-MS/MS analysis, the distribution of TTX was mapped onto the molecular phylogenetic tree. TTX-bearing flatworm species were seen to be restricted to specific Planocera lineages, suggesting that the TTX-bearing flatworm species have common genes for TTX-accumulating mechanisms.

ACS Style

Maho Kashitani; Taiki Okabe; Hikaru Oyama; Kaede Noguchi; Haruka Yamazaki; Rei Suo; Tetsushi Mori; Haruo Sugita; Shiro Itoi. Taxonomic Distribution of Tetrodotoxin in Acotylean Flatworms (Polycladida: Platyhelminthes). Marine Biotechnology 2020, 22, 805 -811.

AMA Style

Maho Kashitani, Taiki Okabe, Hikaru Oyama, Kaede Noguchi, Haruka Yamazaki, Rei Suo, Tetsushi Mori, Haruo Sugita, Shiro Itoi. Taxonomic Distribution of Tetrodotoxin in Acotylean Flatworms (Polycladida: Platyhelminthes). Marine Biotechnology. 2020; 22 (6):805-811.

Chicago/Turabian Style

Maho Kashitani; Taiki Okabe; Hikaru Oyama; Kaede Noguchi; Haruka Yamazaki; Rei Suo; Tetsushi Mori; Haruo Sugita; Shiro Itoi. 2020. "Taxonomic Distribution of Tetrodotoxin in Acotylean Flatworms (Polycladida: Platyhelminthes)." Marine Biotechnology 22, no. 6: 805-811.

Journal article
Published: 14 February 2020 in Chemosphere
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Tetrodotoxin (TTX), a potent neurotoxin, is found in various phylogenetically diverse taxa. In marine environments, the pufferfish is at the top of the food chain among TTX-bearing organisms. The accumulation of TTX in the body of pufferfish appears to be of the food web that begins with bacteria. It is known that toxic pufferfishes possess TTX from the larval/juvenile stage. However, the source of the TTX is unknown because the maternally sourced TTX is extremely small in quantity. Therefore, the TTX has to be obtained from other organisms or directly from the environment. Here, we report evidence that the source of TTX for toxic fish juveniles including the pufferfish (Chelonodon patoca) and the goby (Yongeichthys criniger) is in the food organisms, as seen in their gut contents. Next generation sequencing analysis for the mitochondrial COI gene showed that the majority of the sequence recovered from intestinal contents of these toxic fishes belonged to the flatworm Planocera multitentaculata, a polyclad flatworm containing highly concentrated TTX from the larval stage. PCR specific to P. multitentaculata also showed that DNA encoding the planocerid COI gene was strongly detected in the intestinal contents of the goby and pufferfish juveniles. Additionally, the planocerid specific COI sequence was detected in the environmental seawater collected from the water around the sampling locations for TTX-bearing fish. These results suggest that planocerid larvae are the major TTX supplier for juveniles of TTX-bearing fish species.

ACS Style

Shiro Itoi; Tatsunori Sato; Mitsuki Takei; Riko Yamada; Ryuya Ogata; Hikaru Oyama; Shun Teranishi; Ayano Kishiki; Takenori Wada; Kaede Noguchi; Misato Abe; Taiki Okabe; Hiroyuki Akagi; Maho Kashitani; Rei Suo; Tomoko Koito; Tomohiro Takatani; Osamu Arakawa; Haruo Sugita. The planocerid flatworm is a main supplier of toxin to tetrodotoxin-bearing fish juveniles. Chemosphere 2020, 249, 126217 .

AMA Style

Shiro Itoi, Tatsunori Sato, Mitsuki Takei, Riko Yamada, Ryuya Ogata, Hikaru Oyama, Shun Teranishi, Ayano Kishiki, Takenori Wada, Kaede Noguchi, Misato Abe, Taiki Okabe, Hiroyuki Akagi, Maho Kashitani, Rei Suo, Tomoko Koito, Tomohiro Takatani, Osamu Arakawa, Haruo Sugita. The planocerid flatworm is a main supplier of toxin to tetrodotoxin-bearing fish juveniles. Chemosphere. 2020; 249 ():126217.

Chicago/Turabian Style

Shiro Itoi; Tatsunori Sato; Mitsuki Takei; Riko Yamada; Ryuya Ogata; Hikaru Oyama; Shun Teranishi; Ayano Kishiki; Takenori Wada; Kaede Noguchi; Misato Abe; Taiki Okabe; Hiroyuki Akagi; Maho Kashitani; Rei Suo; Tomoko Koito; Tomohiro Takatani; Osamu Arakawa; Haruo Sugita. 2020. "The planocerid flatworm is a main supplier of toxin to tetrodotoxin-bearing fish juveniles." Chemosphere 249, no. : 126217.

Journal article
Published: 25 November 2019 in Toxicon
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Planocerid flatworms and the related species (Platyhelminthes: polycladida) are known as tetrodotoxin (TTX)-bearing organisms, and they contribute to toxification of marine organisms at higher trophic levels, such as pufferfish and sea slugs. However, little is known of their biology or ecology. In this study, we therefore investigated the occurrence and toxicity of two sympatric planocerids, Planocera multitentaculata and Planocera reticulata, in intertidal zones of the central region of mainland Honshu, Japanese Islands. Planocera multitentaculata was much more abundant than P. reticulata. Body weight was greater in P. multitentaculata than in P. reticulata. Although a significant difference in TTX concentration was not observed between the two species, total TTX content per individual was greater in P. multitentaculata.

ACS Style

Shiro Itoi; Sora Tabuchi; Misato Abe; Hiroyuki Ueda; Hikaru Oyama; Ryuya Ogata; Taiki Okabe; Ayano Kishiki; Haruo Sugita. Difference in tetrodotoxin content between two sympatric planocerid flatworms, Planocera multitentaculata and Planocera reticulata. Toxicon 2019, 173, 57 -61.

AMA Style

Shiro Itoi, Sora Tabuchi, Misato Abe, Hiroyuki Ueda, Hikaru Oyama, Ryuya Ogata, Taiki Okabe, Ayano Kishiki, Haruo Sugita. Difference in tetrodotoxin content between two sympatric planocerid flatworms, Planocera multitentaculata and Planocera reticulata. Toxicon. 2019; 173 ():57-61.

Chicago/Turabian Style

Shiro Itoi; Sora Tabuchi; Misato Abe; Hiroyuki Ueda; Hikaru Oyama; Ryuya Ogata; Taiki Okabe; Ayano Kishiki; Haruo Sugita. 2019. "Difference in tetrodotoxin content between two sympatric planocerid flatworms, Planocera multitentaculata and Planocera reticulata." Toxicon 173, no. : 57-61.

Short report
Published: 23 July 2019 in Ichthyological Research
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Scombrops boops and Scombrops gilberti are commercially important species inhabiting waters around the Japanese archipelago, and recently another undescribed species Scombrops sp. was found. Here, we developed a method using PCR-RFLP on cytochrome b gene sequences of known scombropids to distinguish among these taxa. Comparison of RFLP of the PCR products among scombropids produced a species-specific banding pattern, identifying them with close to 100% accuracy. Two misidentified specimens were identified correctly by the PCR-RFLP analysis developed previously using 16S rRNA sequences. These results showed that PCR-RFLP analysis, using 16S rRNA and cytochrome b sequences in tandem, correctly distinguishes among the three scombropids. We applied this method to 190 individuals collected around the Yonagunijima Island and got some insights into reproductive biology of the three species of Scombrops.

ACS Style

Shiro Itoi; Minori Tanaka; Yukako Mochizuki; Hikaru Oyama; Shu Togawa; Riko Yamada; Takeshi Ito; Hirotoshi Shishido; Yasuji Masuda; Koko Abe; Shizuko Nakai; Noriyuki Takai; Haruo Sugita. Tandem PCR-RFLP analysis helps distinguish among three Japanese gnomefish (Teleostei: Scombropidae: Scombrops). Ichthyological Research 2019, 67, 197 -202.

AMA Style

Shiro Itoi, Minori Tanaka, Yukako Mochizuki, Hikaru Oyama, Shu Togawa, Riko Yamada, Takeshi Ito, Hirotoshi Shishido, Yasuji Masuda, Koko Abe, Shizuko Nakai, Noriyuki Takai, Haruo Sugita. Tandem PCR-RFLP analysis helps distinguish among three Japanese gnomefish (Teleostei: Scombropidae: Scombrops). Ichthyological Research. 2019; 67 (1):197-202.

Chicago/Turabian Style

Shiro Itoi; Minori Tanaka; Yukako Mochizuki; Hikaru Oyama; Shu Togawa; Riko Yamada; Takeshi Ito; Hirotoshi Shishido; Yasuji Masuda; Koko Abe; Shizuko Nakai; Noriyuki Takai; Haruo Sugita. 2019. "Tandem PCR-RFLP analysis helps distinguish among three Japanese gnomefish (Teleostei: Scombropidae: Scombrops)." Ichthyological Research 67, no. 1: 197-202.

Journal article
Published: 11 July 2019 in Toxins
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The pufferfish Takifugu niphobles (at present Takifugu alboplumbeus) possesses highly concentrated tetrodotoxin (TTX), an extremely potent neurotoxin that provides effective protection from predators, at least at the larval stages. However, the source of the toxin has remained unclear. Recently, DNA from the toxic flatworm Planocera multitentaculata was detected in the intestinal contents of juveniles and young of the pufferfish, suggesting that the flatworm contributes to its toxification at various stages of its life. In this study, we describe the behavior of the pufferfish in the intertidal zone that appears to contribute to its toxification before and during its spawning period: pufferfish were found to aggregate and ingest flatworm egg plates by scraping them off the surface of rocks. DNA analysis based on 28S rRNA and cytochrome c oxidase subunit I (COI) genes identified the egg plates as those of P. multitentaculata. Liquid chromatography with tandem mass spectrometry analysis revealed that the egg plates contain highly concentrated TTX. The feeding behavior of the pufferfish on the flatworm egg plates was also observed in the aquarium. These results suggest that pufferfish feed on the flatworm egg plate, which enables them to acquire toxicity themselves while providing their offspring with the protective shield of TTX.

ACS Style

Taiki Okabe; Hikaru Oyama; Maho Kashitani; Yuta Ishimaru; Rei Suo; Haruo Sugita; Shiro Itoi. Toxic Flatworm Egg Plates Serve as a Possible Source of Tetrodotoxin for Pufferfish. Toxins 2019, 11, 402 .

AMA Style

Taiki Okabe, Hikaru Oyama, Maho Kashitani, Yuta Ishimaru, Rei Suo, Haruo Sugita, Shiro Itoi. Toxic Flatworm Egg Plates Serve as a Possible Source of Tetrodotoxin for Pufferfish. Toxins. 2019; 11 (7):402.

Chicago/Turabian Style

Taiki Okabe; Hikaru Oyama; Maho Kashitani; Yuta Ishimaru; Rei Suo; Haruo Sugita; Shiro Itoi. 2019. "Toxic Flatworm Egg Plates Serve as a Possible Source of Tetrodotoxin for Pufferfish." Toxins 11, no. 7: 402.

Mito communication
Published: 02 January 2019 in Mitochondrial DNA Part B
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The fish family Scombropidae consists of a single genus, Scombrops, and is distributed in the waters of the northwestern Pacific Ocean, southwestern Indian Ocean and western Atlantic Ocean, including the Caribbean Sea. Among these, the population of South Africa has been renamed from Scombrops dubius to Scombrops boops, which is known to be distributed in waters around Japanese Archipelago. We are skeptical of this revision as the two populations are geographically isolated between the waters of the Far East and the southern end of the Africa coast. Recently, our lab determined the sequences of the complete mitochondrial genome of three Japanese gnomefish, S. boops, Scombrops gilberti and an undescribed scombropid species (Scombrops sp.). Here, we compared the partial sequence of cytochrome c oxidase subunit I (COI) from the three Japanese gnomefish with that of the African population. The African sequences showed 95.5–96.6% identity with the Japanese sequences, while the corresponding sequences from the Japanese species showed 98.2–100% identity with each other. A maximum likelihood tree based on the partial sequence of COI also demonstrated that the clade of African gnomefish is distinct from those of Japanese species including S. boops. These results suggest that the scombropid fish in the African waters is a different species from S. boops and that it is appropriate to resurrect the name Scombrops dubius for the African population.

ACS Style

Hikaru Oyama; Shiro Itoi; Hiroyuki Ueda; Yukako Mochizuki; Minori Tanaka; Takeshi Ito; Hirotoshi Shishido; Yasuji Masuda; Noriyuki Takai; Haruo Sugita. Genetic difference between African and Japanese scombropid populations based on cytochrome c oxidase subunit I gene sequences. Mitochondrial DNA Part B 2019, 4, 1016 -1020.

AMA Style

Hikaru Oyama, Shiro Itoi, Hiroyuki Ueda, Yukako Mochizuki, Minori Tanaka, Takeshi Ito, Hirotoshi Shishido, Yasuji Masuda, Noriyuki Takai, Haruo Sugita. Genetic difference between African and Japanese scombropid populations based on cytochrome c oxidase subunit I gene sequences. Mitochondrial DNA Part B. 2019; 4 (1):1016-1020.

Chicago/Turabian Style

Hikaru Oyama; Shiro Itoi; Hiroyuki Ueda; Yukako Mochizuki; Minori Tanaka; Takeshi Ito; Hirotoshi Shishido; Yasuji Masuda; Noriyuki Takai; Haruo Sugita. 2019. "Genetic difference between African and Japanese scombropid populations based on cytochrome c oxidase subunit I gene sequences." Mitochondrial DNA Part B 4, no. 1: 1016-1020.

Journal article
Published: 17 August 2018 in Scientific Reports
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Beginning with the larval stages, marine pufferfish such as Takifugu niphobles contain tetrodotoxin (TTX), an extremely potent neurotoxin. Although highly concentrated TTX has been detected in adults and juveniles of these fish, the source of the toxin has remained unclear. Here we show that TTX in the flatworm Planocera multitentaculata contributes to the toxification of the pufferfish throughout the life cycle of the flatworm. A species-specific PCR method was developed for the flatworm, and the specific DNA fragment was detected in the digesta of wild pufferfish adults. Predation experiments showed that flatworm larvae were eaten by the pufferfish juveniles, and that the two-day postprandial TTX content in these pufferfish was 20–50 μg/g. Predation experiments additionally showed flatworm adults were also eaten by pufferfish young, and after two days of feeding, TTX accumulated in the skin, liver and intestine of the pufferfish.

ACS Style

Shiro Itoi; Hiroyuki Ueda; Riko Yamada; Mitsuki Takei; Tatsunori Sato; Shotaro Oshikiri; Yoshiki Wajima; Ryuya Ogata; Hikaru Oyama; Takahiro Shitto; Kazuya Okuhara; Tadasuke Tsunashima; Eitaro Sawayama; Haruo Sugita. Including planocerid flatworms in the diet effectively toxifies the pufferfish, Takifugu niphobles. Scientific Reports 2018, 8, 1 -10.

AMA Style

Shiro Itoi, Hiroyuki Ueda, Riko Yamada, Mitsuki Takei, Tatsunori Sato, Shotaro Oshikiri, Yoshiki Wajima, Ryuya Ogata, Hikaru Oyama, Takahiro Shitto, Kazuya Okuhara, Tadasuke Tsunashima, Eitaro Sawayama, Haruo Sugita. Including planocerid flatworms in the diet effectively toxifies the pufferfish, Takifugu niphobles. Scientific Reports. 2018; 8 (1):1-10.

Chicago/Turabian Style

Shiro Itoi; Hiroyuki Ueda; Riko Yamada; Mitsuki Takei; Tatsunori Sato; Shotaro Oshikiri; Yoshiki Wajima; Ryuya Ogata; Hikaru Oyama; Takahiro Shitto; Kazuya Okuhara; Tadasuke Tsunashima; Eitaro Sawayama; Haruo Sugita. 2018. "Including planocerid flatworms in the diet effectively toxifies the pufferfish, Takifugu niphobles." Scientific Reports 8, no. 1: 1-10.

Journal article
Published: 01 June 2018 in Toxicon
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It is known that tetrodotoxin (TTX), also known as pufferfish toxin, is an extremely potent neurotoxin and had been detected in various taxa. However, the exact function of the toxin in TTX-bearing organisms has remained unclear. In Takifugu pufferfish species, it has been suggested that TTX is utilized to protect larvae from predators but no experimental proof exists. In the present study, we used pufferfish Takifugu alboplumbeus larvae from wild and cultured parents to determine the effects of the maternal TTX on the survival of toxic and non-toxic pufferfish larvae, respectively. TTX contents in the larval pufferfish differed between the larvae derived from wild and cultured parents (1.23 ± 0.20 ng/individual vs. undetectable levels, respectively). Immunohistochemical staining with anti-TTX monoclonal antibody demonstrated that the TTX-specific signals were primarily observed at the body surface of the larvae of wild parents, but not of cultured parents. Predation experiments demonstrated that the juveniles of Girella punctata and Chaenogobius gulosus, used as predator fish, ingested the pufferfish larvae derived from either type of parents, but instantly spat out those from wild parents only. These results indicate that larvae, which are at the most vulnerable stage in the life of pufferfish, are protected by maternal TTX.

ACS Style

Shiro Itoi; Miwa Suzuki; Kiyoshi Asahina; Eitaro Sawayama; Junki Nishikubo; Hikaru Oyama; Mitsuki Takei; Nanae Shiibashi; Tomohiro Takatani; Osamu Arakawa; Haruo Sugita. Role of maternal tetrodotoxin in survival of larval pufferfish. Toxicon 2018, 148, 95 -100.

AMA Style

Shiro Itoi, Miwa Suzuki, Kiyoshi Asahina, Eitaro Sawayama, Junki Nishikubo, Hikaru Oyama, Mitsuki Takei, Nanae Shiibashi, Tomohiro Takatani, Osamu Arakawa, Haruo Sugita. Role of maternal tetrodotoxin in survival of larval pufferfish. Toxicon. 2018; 148 ():95-100.

Chicago/Turabian Style

Shiro Itoi; Miwa Suzuki; Kiyoshi Asahina; Eitaro Sawayama; Junki Nishikubo; Hikaru Oyama; Mitsuki Takei; Nanae Shiibashi; Tomohiro Takatani; Osamu Arakawa; Haruo Sugita. 2018. "Role of maternal tetrodotoxin in survival of larval pufferfish." Toxicon 148, no. : 95-100.

Article
Published: 19 January 2018 in Marine Drugs
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Polyclad flatworms comprise a highly diverse and cosmopolitan group of marine turbellarians. Although some species of the genera Planocera and Stylochoplana are known to be tetrodotoxin (TTX)-bearing, there are few new reports. In this study, planocerid-like flatworm specimens were found in the sea bottom off the waters around the Ryukyu Islands, Japan. The bodies were translucent with brown reticulate mottle, contained two conical tentacles with eye spots clustered at the base, and had a slightly frilled-body margin. Each specimen was subjected to TTX extraction followed by liquid chromatography with tandem mass spectrometry analysis. Mass chromatograms were found to be identical to those of the TTX standards. The TTX amounts in the two flatworm specimens were calculated to be 468 and 3634 μg. Their external morphology was found to be identical to that of Planocera heda. Phylogenetic analysis based on the sequences of the 28S rRNA gene and cytochrome-c oxidase subunit I gene also showed that both specimens clustered with the flatworms of the genus Planocera (Planocera multitentaculata and Planocera reticulata). This fact suggests that there might be other Planocera species that also possess highly concentrated TTX, contributing to the toxification of TTX-bearing organisms, including fish.

ACS Style

Hiroyuki Ueda; Shiro Itoi; Haruo Sugita. TTX-Bearing Planocerid Flatworm (Platyhelminthes: Acotylea) in the Ryukyu Islands, Japan. Marine Drugs 2018, 16, 37 .

AMA Style

Hiroyuki Ueda, Shiro Itoi, Haruo Sugita. TTX-Bearing Planocerid Flatworm (Platyhelminthes: Acotylea) in the Ryukyu Islands, Japan. Marine Drugs. 2018; 16 (1):37.

Chicago/Turabian Style

Hiroyuki Ueda; Shiro Itoi; Haruo Sugita. 2018. "TTX-Bearing Planocerid Flatworm (Platyhelminthes: Acotylea) in the Ryukyu Islands, Japan." Marine Drugs 16, no. 1: 37.

Journal article
Published: 05 September 2017 in Aquatic Biology
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ACS Style

T Tsunashima; M Hagiya; R Yamada; T Koito; N Tsuyuki; S Izawa; K Kosoba; S Itoi; H Sugita. A molecular framework for the taxonomy and systematics of Japanese marine turbellarian flatworms (Platyhelminthes, Polycladida). Aquatic Biology 2017, 26, 159 -167.

AMA Style

T Tsunashima, M Hagiya, R Yamada, T Koito, N Tsuyuki, S Izawa, K Kosoba, S Itoi, H Sugita. A molecular framework for the taxonomy and systematics of Japanese marine turbellarian flatworms (Platyhelminthes, Polycladida). Aquatic Biology. 2017; 26 ():159-167.

Chicago/Turabian Style

T Tsunashima; M Hagiya; R Yamada; T Koito; N Tsuyuki; S Izawa; K Kosoba; S Itoi; H Sugita. 2017. "A molecular framework for the taxonomy and systematics of Japanese marine turbellarian flatworms (Platyhelminthes, Polycladida)." Aquatic Biology 26, no. : 159-167.

Journal article
Published: 25 February 2017 in Marine Drugs
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Tetrodotoxin (TTX) is a potent neurotoxin that acts specifically on voltage-gated sodium channels on excitable membranes of muscle and nerve tissues. The biosynthetic process for TTX is unclear, although marine bacteria are generally thought to be the primary producers. The marine flatworm Planocera multitentaculata is a known TTX-bearing organism, and is suspected to be a TTX supplier to pufferfish. In this study, flatworm specimens were collected from an intertidal zone in Hayama, Kanagawa, Japan, the TTX content of the flatworm was measured using liquid chromatography with tandem mass spectrometry (LC-MS/MS), and seasonal changes in TTX content were investigated. No significant difference in TTX concentration of the flatworm body was found between the spawning period and other periods. However, the TTX content in individual flatworms was significantly higher in the spawning period than at other times. The TTX content rose in association with an increase in the body weight of the flatworm.

ACS Style

Riko Yamada; Tadasuke Tsunashima; Mitsuki Takei; Tatsunori Sato; Yoshiki Wajima; Makoto Kawase; Shotaro Oshikiri; Yusuke Kajitani; Keita Kosoba; Hiroyuki Ueda; Koko Abe; Shiro Itoi; Haruo Sugita. Seasonal Changes in the Tetrodotoxin Content of the Flatworm Planocera multitentaculata. Marine Drugs 2017, 15, 56 .

AMA Style

Riko Yamada, Tadasuke Tsunashima, Mitsuki Takei, Tatsunori Sato, Yoshiki Wajima, Makoto Kawase, Shotaro Oshikiri, Yusuke Kajitani, Keita Kosoba, Hiroyuki Ueda, Koko Abe, Shiro Itoi, Haruo Sugita. Seasonal Changes in the Tetrodotoxin Content of the Flatworm Planocera multitentaculata. Marine Drugs. 2017; 15 (3):56.

Chicago/Turabian Style

Riko Yamada; Tadasuke Tsunashima; Mitsuki Takei; Tatsunori Sato; Yoshiki Wajima; Makoto Kawase; Shotaro Oshikiri; Yusuke Kajitani; Keita Kosoba; Hiroyuki Ueda; Koko Abe; Shiro Itoi; Haruo Sugita. 2017. "Seasonal Changes in the Tetrodotoxin Content of the Flatworm Planocera multitentaculata." Marine Drugs 15, no. 3: 56.

Mitogenome announcement
Published: 01 January 2017 in Mitochondrial DNA Part B
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The complete mitochondrial genome of an undescribed gnomefish species of the genus Scombrops was determined using a PCR-based method. The total length of mitochondrial DNA (mtDNA) was 16,521 bp, and included 13 protein-coding genes, two ribosomal RNA (rRNA) genes, 22 transfer RNA (tRNA) genes and one control region. The mitochondrial gene arrangement of this gnomefish species was identical to that of two previously described scombropid species, Scombrops boops and Scombrops gilberti, and also to those of other teleosts. Maximum likelihood analysis showed that the undescribed scombropid species is most closely related to S. boops.

ACS Style

Yukako Mochizuki; Riko Yamada; Hirotoshi Shishido; Yasuji Masuda; Shizuko Nakai; Noriyuki Takai; Shiro Itoi; Haruo Sugita. Complete mitochondrial genome of an undescribed gnomefish of the genusScombrops(Teleostei, Scombropidae) from southern waters off Kyushu Island, Japan. Mitochondrial DNA Part B 2017, 2, 106 -108.

AMA Style

Yukako Mochizuki, Riko Yamada, Hirotoshi Shishido, Yasuji Masuda, Shizuko Nakai, Noriyuki Takai, Shiro Itoi, Haruo Sugita. Complete mitochondrial genome of an undescribed gnomefish of the genusScombrops(Teleostei, Scombropidae) from southern waters off Kyushu Island, Japan. Mitochondrial DNA Part B. 2017; 2 (1):106-108.

Chicago/Turabian Style

Yukako Mochizuki; Riko Yamada; Hirotoshi Shishido; Yasuji Masuda; Shizuko Nakai; Noriyuki Takai; Shiro Itoi; Haruo Sugita. 2017. "Complete mitochondrial genome of an undescribed gnomefish of the genusScombrops(Teleostei, Scombropidae) from southern waters off Kyushu Island, Japan." Mitochondrial DNA Part B 2, no. 1: 106-108.

Journal article
Published: 01 May 2016 in Toxicon
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To investigate seasonal changes in the whole body content and tissue distribution of tetrodotoxin (TTX) in the pufferfish Takifugu niphobles, wild individuals were collected from the coastal waters around Miura Peninsula from November 2010 to May 2012, and their tissues were subjected to LC-MS/MS analysis. Fish that were sexually mature were classified as being in the maturation period (April), the spawning period (May – July) or the “ordinary period” (i.e., other months). In both sexes, gonad somatic index rapidly increased during the maturation period and then decreased during the spawning period. Whole body TTX content was significantly higher during the maturation/spawning period than in the ordinary period. Through all seasons, TTX was localized in the skin or ovary in females and in the skin or liver in males: the difference in TTX localization between females and males was particularly evident during the spawning period.

ACS Style

Shiro Itoi; Kento Ishizuka; Ryoko Mitsuoka; Narumi Takimoto; Naoto Yokoyama; Ayumi Detake; Chie Takayanagi; Saori Yoshikawa; Haruo Sugita. Seasonal changes in the tetrodotoxin content of the pufferfish Takifugu niphobles. Toxicon 2016, 114, 53 -58.

AMA Style

Shiro Itoi, Kento Ishizuka, Ryoko Mitsuoka, Narumi Takimoto, Naoto Yokoyama, Ayumi Detake, Chie Takayanagi, Saori Yoshikawa, Haruo Sugita. Seasonal changes in the tetrodotoxin content of the pufferfish Takifugu niphobles. Toxicon. 2016; 114 ():53-58.

Chicago/Turabian Style

Shiro Itoi; Kento Ishizuka; Ryoko Mitsuoka; Narumi Takimoto; Naoto Yokoyama; Ayumi Detake; Chie Takayanagi; Saori Yoshikawa; Haruo Sugita. 2016. "Seasonal changes in the tetrodotoxin content of the pufferfish Takifugu niphobles." Toxicon 114, no. : 53-58.

Journal article
Published: 01 December 2015 in Toxicon
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Pufferfish (Takifugu spp.) possess a potent neurotoxin, tetrodotoxin (TTX). TTX has been detected in various organisms including food animals of pufferfish, and TTX-producing bacteria have been isolated from these animals. TTX in marine pufferfish accumulates in the pufferfish via the food web starting with marine bacteria. However, such accumulation is unlikely to account for the amount of TTX in the pufferfish body because of the minute amounts of TTX produced by marine bacteria. Therefore, the toxification process in pufferfish still remains unclear. In this article we report the presence of numerous Takifugu pardalis eggs in the intestinal contents of another pufferfish, Takifugu niphobles. The identity of T. pardalis being determined by direct sequencing for mitochondrial DNA. LC-MS/MS analysis revealed that the peak detected in the egg samples corresponded to TTX. Toxification experiments in recirculating aquaria demonstrated that cultured Takifugu rubripes quickly became toxic upon being fed toxic (TTX-containing) T. rubripes eggs. These results suggest that T. niphobles ingested the toxic eggs of another pufferfish T. pardalis to toxify themselves more efficiently via a TTX loop consisting of TTX-bearing organisms at a higher trophic level in the food web.

ACS Style

Shiro Itoi; Ao Kozaki; Keitaro Komori; Tadasuke Tsunashima; Shunsuke Noguchi; Mitsuo Kawane; Haruo Sugita. Toxic Takifugu pardalis eggs found in Takifugu niphobles gut: Implications for TTX accumulation in the pufferfish. Toxicon 2015, 108, 141 -146.

AMA Style

Shiro Itoi, Ao Kozaki, Keitaro Komori, Tadasuke Tsunashima, Shunsuke Noguchi, Mitsuo Kawane, Haruo Sugita. Toxic Takifugu pardalis eggs found in Takifugu niphobles gut: Implications for TTX accumulation in the pufferfish. Toxicon. 2015; 108 ():141-146.

Chicago/Turabian Style

Shiro Itoi; Ao Kozaki; Keitaro Komori; Tadasuke Tsunashima; Shunsuke Noguchi; Mitsuo Kawane; Haruo Sugita. 2015. "Toxic Takifugu pardalis eggs found in Takifugu niphobles gut: Implications for TTX accumulation in the pufferfish." Toxicon 108, no. : 141-146.

Journal article
Published: 01 February 2014 in Toxicon
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Marine pufferfish contain tetrodotoxin (TTX), an extremely potent neurotoxin. All species of the genus Takifugu accumulate TTX in the liver and ovaries, although the tissue(s) in which it is localized can differ among species. TTX is the major defense strategy the pufferfish appears to use against predators. TTX is also used as a male-attracting pheromone during spawning. Here we demonstrate an additional (and unexpected) use of maternal TTX in the early larval stages of the Takifugu pufferfish. Predation experiments demonstrated that juveniles of all the species of fish used as predators ingested pufferfish larvae, but spat them out promptly. Liquid Chromatography-Tandem Mass Spectrometry (LC-MSMS) analysis revealed that the pufferfish larvae contain a small quantity of TTX, which is not enough to be lethal to the predators. Immunohistochemical analysis with anti-TTX monoclonal antibody revealed that the TTX is primarily localized in the body surface of the larvae as a layer of protection. Our study showed the female parent of the Takifugu pufferfish vertically transfers TTX to the larvae through its accumulation in the ovaries, and subsequent localization on the body surface of the larvae

ACS Style

Shiro Itoi; Saori Yoshikawa; Kiyoshi Asahina; Miwa Suzuki; Kento Ishizuka; Narumi Takimoto; Ryoko Mitsuoka; Naoto Yokoyama; Ayumi Detake; Chie Takayanagi; Miho Eguchi; Ryohei Tatsuno; Mitsuo Kawane; Shota Kokubo; Shihori Takanashi; Ai Miura; Katsuyoshi Suitoh; Tomohiro Takatani; Osamu Arakawa; Yoshitaka Sakakura; Haruo Sugita. Larval pufferfish protected by maternal tetrodotoxin. Toxicon 2014, 78, 35 -40.

AMA Style

Shiro Itoi, Saori Yoshikawa, Kiyoshi Asahina, Miwa Suzuki, Kento Ishizuka, Narumi Takimoto, Ryoko Mitsuoka, Naoto Yokoyama, Ayumi Detake, Chie Takayanagi, Miho Eguchi, Ryohei Tatsuno, Mitsuo Kawane, Shota Kokubo, Shihori Takanashi, Ai Miura, Katsuyoshi Suitoh, Tomohiro Takatani, Osamu Arakawa, Yoshitaka Sakakura, Haruo Sugita. Larval pufferfish protected by maternal tetrodotoxin. Toxicon. 2014; 78 ():35-40.

Chicago/Turabian Style

Shiro Itoi; Saori Yoshikawa; Kiyoshi Asahina; Miwa Suzuki; Kento Ishizuka; Narumi Takimoto; Ryoko Mitsuoka; Naoto Yokoyama; Ayumi Detake; Chie Takayanagi; Miho Eguchi; Ryohei Tatsuno; Mitsuo Kawane; Shota Kokubo; Shihori Takanashi; Ai Miura; Katsuyoshi Suitoh; Tomohiro Takatani; Osamu Arakawa; Yoshitaka Sakakura; Haruo Sugita. 2014. "Larval pufferfish protected by maternal tetrodotoxin." Toxicon 78, no. : 35-40.

Journal article
Published: 07 January 2014 in Folia Microbiologica
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Lactococcus lactis subsp. lactis has been isolated from the intestines of marine fish and is a candidate probiotic for aquaculture. In order to use the bacterium as a probiotic, properties such as bile tolerance need to be assessed. Here, we compared bile tolerance in L. lactis strains derived from different sources. Three L. lactis subsp. lactis strains from marine fish (MFL), freshwater fish (FFL), and cheese starter (CSL) were used along with an Lactococcus lactis subsp. cremoris strain from cheese starter (CSC). The four strains were grown under various culture conditions: deMan-Rogosa-Sharpe (MRS) broth containing bile salts/acids, MRS agar containing oxgall, and phosphate-buffered saline (PBS) containing fish bile. Survival/growth of the strains in the presence of sodium cholate and sodium deoxycholate varied in the order MFL, CSL > CSC > FFL; in the presence of sodium taurocholate, the order was MFL > CSL > CSC > FFL. In liquid media containing various concentrations of oxgall, survival of the strains was observed in the order MFL > CSL > FFL and CSC. The survival of MFL was not affected by bile collected from the goldfish (Carassius auratus subsp. auratus) or the puffer fish (Takifugu niphobles), although the other strains showed significant inhibition of growth. It is a novel and beneficial finding that MFL has the highest resistance to bile acid.

ACS Style

Shihori Takanashi; Ai Miura; Koko Abe; Junya Uchida; Shiro Itoi; Haruo Sugita. Variations in bile tolerance among Lactococcus lactis strains derived from different sources. Folia Microbiologica 2014, 59, 289 -293.

AMA Style

Shihori Takanashi, Ai Miura, Koko Abe, Junya Uchida, Shiro Itoi, Haruo Sugita. Variations in bile tolerance among Lactococcus lactis strains derived from different sources. Folia Microbiologica. 2014; 59 (4):289-293.

Chicago/Turabian Style

Shihori Takanashi; Ai Miura; Koko Abe; Junya Uchida; Shiro Itoi; Haruo Sugita. 2014. "Variations in bile tolerance among Lactococcus lactis strains derived from different sources." Folia Microbiologica 59, no. 4: 289-293.

Journal article
Published: 29 November 2013 in Annals of Microbiology
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Lactic acid bacteria (LAB) were isolated from the intestinal tract of the wild clam Meretrix lamarckii caught from the coastal waters of Kashima, Ibaraki, Japan. As many as 415 isolates were obtained using the culture method, of which 70 were considered presumptive LAB strains based on phenotypic tests. Phylogenetic analysis of these presumptive isolates of LAB based on the sequence of the 16S rRNA gene demonstrated that the species belonged to several genera of Lactobacillus, Lactococcus and Pediococcus. Interestingly, however, the species composition was different between the samples in July and October 2010. Further analyses based on the fermentation profiles revealed that the LAB from the clam caught in July 2010 were identified to be Lactobacillus curvatus, Lactobacillus plantarum, Lactococcus lactis subsp. cremoris and Pediococcus pentosaceus, whereas those in October 2010 were identified to be Lactobacillus plantarum, Lactococcus lactis subsp. lactis and P. pentosaceus. The diversity of LAB in the intestinal tract of the clam suggests that the filter feeder bivalves such as M. lamarckii are a rich repository of marine isolates of LAB.

ACS Style

Shiro Itoi; Junya Uchida; Shihori Takanashi; Tomoyo Narita; Koko Abe; Satomi Naya; Haruo Sugita. The clam Meretrix lamarckii (Bivalvia: Veneridae) is a rich repository of marine lactic acid bacterial strains. Annals of Microbiology 2013, 64, 1267 -1274.

AMA Style

Shiro Itoi, Junya Uchida, Shihori Takanashi, Tomoyo Narita, Koko Abe, Satomi Naya, Haruo Sugita. The clam Meretrix lamarckii (Bivalvia: Veneridae) is a rich repository of marine lactic acid bacterial strains. Annals of Microbiology. 2013; 64 (3):1267-1274.

Chicago/Turabian Style

Shiro Itoi; Junya Uchida; Shihori Takanashi; Tomoyo Narita; Koko Abe; Satomi Naya; Haruo Sugita. 2013. "The clam Meretrix lamarckii (Bivalvia: Veneridae) is a rich repository of marine lactic acid bacterial strains." Annals of Microbiology 64, no. 3: 1267-1274.