This page has only limited features, please log in for full access.
Professor of Aquaculture, Nihon University major field field: microbiology of aquaculture environments and fish guts
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.
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 StyleRei 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 StyleRei 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.
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.
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 StyleTaiki 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 StyleTaiki 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.
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.
Hiroyuki Ueda; Shiro Itoi; Haruo Sugita. TTX-Bearing Planocerid Flatworm (Platyhelminthes: Acotylea) in the Ryukyu Islands, Japan. Marine Drugs 2018, 16, 37 .
AMA StyleHiroyuki Ueda, Shiro Itoi, Haruo Sugita. TTX-Bearing Planocerid Flatworm (Platyhelminthes: Acotylea) in the Ryukyu Islands, Japan. Marine Drugs. 2018; 16 (1):37.
Chicago/Turabian StyleHiroyuki Ueda; Shiro Itoi; Haruo Sugita. 2018. "TTX-Bearing Planocerid Flatworm (Platyhelminthes: Acotylea) in the Ryukyu Islands, Japan." Marine Drugs 16, no. 1: 37.
In the original publication, the number of the NCTC strain used was published incorrectly. The authors apologize for the error. The error has no effect on the validity of the results and is corrected
Haruo Sugita; Shun Kitao; Satoshi Narisawa; Ryosuke Minamishima; Shiro Itoi. Correction to: Diversity of culturable bacterial communities in the intestinal tracts of goldfish (Carassius auratus) and their ability to produce N-acyl homoserine lactone. Folia Microbiologica 2017, 63, 125 -125.
AMA StyleHaruo Sugita, Shun Kitao, Satoshi Narisawa, Ryosuke Minamishima, Shiro Itoi. Correction to: Diversity of culturable bacterial communities in the intestinal tracts of goldfish (Carassius auratus) and their ability to produce N-acyl homoserine lactone. Folia Microbiologica. 2017; 63 (1):125-125.
Chicago/Turabian StyleHaruo Sugita; Shun Kitao; Satoshi Narisawa; Ryosuke Minamishima; Shiro Itoi. 2017. "Correction to: Diversity of culturable bacterial communities in the intestinal tracts of goldfish (Carassius auratus) and their ability to produce N-acyl homoserine lactone." Folia Microbiologica 63, no. 1: 125-125.
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.
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 StyleRiko 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 StyleRiko 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.
Intestinal bacteria isolated from goldfish (Carassius auratus) were identified based on 16 ribosomal RNA (rRNA) gene sequences and screened for their ability to produce N-acyl homoserine lactone (AHL), an autoinducer of the quorum sensing (QS) system. The 230 aerobes/facultative anaerobes that were isolated comprised members of the genera Aeromonas (184 isolates), Citrobacter (11), Enterobacter (2), Shewanella (28), Vagococcus (1), and Vibrio (4). Among these genera, the two most abundant species were Aeromonas veronii (163 isolates) and Shewanella xiamenensis (27). In addition, 142 obligate anaerobes consisting of Cetobacterium somerae (139 isolates), Clostridium frigidicarnis (2), and Cetobacterium sp. (1) were also isolated. One hundred seventy isolates (74.2%) belonging to the genera Aeromonas, Citrobacter, Enterobacter, Shewanella, and Vibrio produced AHL, while 155 (67.7%) and 91 (39.7%) isolates possessed the luxR and luxI gene homologs, respectively. None of the obligate anaerobes produced AHL or possessed luxRI homologs. Total viable counts ranged from 1.2 × 107 to 2.2 × 109 CFU/g, which were accounted for 0.8 to 15.2% of direct counts. Aeromonas veronii, S. xiamenensis, and C. somerae were detected from five goldfish at densities ranging from 4.0 × 106 to 1.7 × 109 CFU/g, indicating that these bacteria are dominant components of the culturable gut flora in goldfish. In addition, members of the genera Aeromonas and Shewanella appeared to communicate with each other by using the QS system to some extent when the concentration of AHL reaches a certain threshold. It is therefore suggested that bacteria with the ability to disrupt AHL secretion in intestinal environments are potential candidates for probionts for preventing opportunistic infections in freshwater fish such as goldfish.
Haruo Sugita; Shun Kitao; Satoshi Narisawa; Ryosuke Minamishima; Shiro Itoi. Diversity of culturable bacterial communities in the intestinal tracts of goldfish (Carassius auratus) and their ability to produce N-acyl homoserine lactone. Folia Microbiologica 2017, 62, 263 -267.
AMA StyleHaruo Sugita, Shun Kitao, Satoshi Narisawa, Ryosuke Minamishima, Shiro Itoi. Diversity of culturable bacterial communities in the intestinal tracts of goldfish (Carassius auratus) and their ability to produce N-acyl homoserine lactone. Folia Microbiologica. 2017; 62 (3):263-267.
Chicago/Turabian StyleHaruo Sugita; Shun Kitao; Satoshi Narisawa; Ryosuke Minamishima; Shiro Itoi. 2017. "Diversity of culturable bacterial communities in the intestinal tracts of goldfish (Carassius auratus) and their ability to produce N-acyl homoserine lactone." Folia Microbiologica 62, no. 3: 263-267.
The complete mitochondrial genome of the Japanese gnomefish, Scombrops gilberti, was determined using a PCR-based method. The total length of mitochondrial DNA (mtDNA) is 16 518 bp, which includes 13 protein-coding genes, two ribosomal RNA (rRNA) genes, 22 transfer RNA (tRNA) genes, and one control region. The mitochondrial gene arrangement of S. gilberti was found to be identical to that of other scombropid and indeed, other teleosts as well. Maximum likelihood analysis revealed that Scombropidae forms a sister group to Pempheriformes.
Tadasuke Tsunashima; Riko Yamada; Koko Abe; Shunsuke Noguchi; Shiro Itoi; Shizuko Nakai; Noriyuki Takai; Haruo Sugita. Phylogenetic position of Scombropidae within teleostei: the complete mitochondrial genome of the gnomefish, Scombrops gilberti. Mitochondrial DNA Part A 2015, 27, 3446 -3448.
AMA StyleTadasuke Tsunashima, Riko Yamada, Koko Abe, Shunsuke Noguchi, Shiro Itoi, Shizuko Nakai, Noriyuki Takai, Haruo Sugita. Phylogenetic position of Scombropidae within teleostei: the complete mitochondrial genome of the gnomefish, Scombrops gilberti. Mitochondrial DNA Part A. 2015; 27 (5):3446-3448.
Chicago/Turabian StyleTadasuke Tsunashima; Riko Yamada; Koko Abe; Shunsuke Noguchi; Shiro Itoi; Shizuko Nakai; Noriyuki Takai; Haruo Sugita. 2015. "Phylogenetic position of Scombropidae within teleostei: the complete mitochondrial genome of the gnomefish, Scombrops gilberti." Mitochondrial DNA Part A 27, no. 5: 3446-3448.
This study was conducted to clarify the taxonomic status of Bacteroides type A strains with high vitamin B(12)-producing ability that is widely distributed in the intestinal tracts of freshwater fish. Seventeen strains of Bacteroides type A isolated from five fish species were all rod-shaped and gram-negative. The strains were positive for esculin hydrolysis, nitrate reduction, resistance to bile, acid phosphatase, and negative for the production of catalase and urease and the susceptibility to vancomycin. The G+C content of DNA from the 17 strains was 29 x 1-31 x 9 mol%, and 16S rDNA sequence analysis revealed a close phylogenetic relationship between Bacteroides type A strains and Cetobacterium somerae sharing 99 x 7-100% sequence similarity. In addition, strains were capable of producing vitamin B(12) at a rate of 1 x 82-13 x 98 ng ml(-1) in 48 h. Phenotypic and phylogenetic characteristics indicated that all isolates previously classified as Bacteroides type A strains belong to C. someare. This study provided the important finding of novel niche of vancomycin-resistant bacteria such as C. somerae in the intestinal tract of freshwater fish.
C. Tsuchiya; T. Sakata; H. Sugita. Novel ecological niche of Cetobacterium somerae, an anaerobic bacterium in the intestinal tracts of freshwater fish. Letters in Applied Microbiology 2007, 46, 43 -48.
AMA StyleC. Tsuchiya, T. Sakata, H. Sugita. Novel ecological niche of Cetobacterium somerae, an anaerobic bacterium in the intestinal tracts of freshwater fish. Letters in Applied Microbiology. 2007; 46 (1):43-48.
Chicago/Turabian StyleC. Tsuchiya; T. Sakata; H. Sugita. 2007. "Novel ecological niche of Cetobacterium somerae, an anaerobic bacterium in the intestinal tracts of freshwater fish." Letters in Applied Microbiology 46, no. 1: 43-48.