title: Time and order of eruption of first functional teeth in the upper jaw of post-larval life of Sicyopterus japonicus (Gobiidiae: Sicydiinae) during cranial metamorphosis at the time of river recruitment.
abstract: OBJECTIVE
  The present study was aimed at elucidating the time and order of eruption of first functional teeth in the upper jaw of post-larval life of Sicyopterus japonicus (S. japonicus) during cranial metamorphosis at the time of river recruitment.
  
  
  METHODS
  Fishes were caught at the post-larval stage at a river mouth and maintained for 7 days in a water tank. Each of 10 specimens was evaluated every day for 7 days by using microcomputed tomography, scanning electron microscopy, and light microscopy with peculiar attention to the development of the upper jaw teeth.
  
  
  RESULTS
  Fishes caught at the river mouth were mostly transparent, with a rostral terminal mouth, and no teeth could be found in either the upper or lower jaw. At 2 days after collection, the mouth position changed from terminal to subterminal, resulting from a change in head shape. The initial eruption of first functional teeth was detected at the anterior two-thirds region of each upper jaw. These teeth erupted in adjacent positions, most had a tricuspid crown, and they represented miniature versions of adult teeth. At 5 days, the position of the mouth became further relocated from terminal rostral to ventral. The number of erupted teeth increased, followed by spreading of them anteriorly and posteriorly. At 7 days, they formed a single row of close-set tricuspid teeth along the entire length of each upper jaw.
  
  
  CONCLUSIONS
  The present study demonstrated that even under laboratory conditions a rapid and drastic cranial metamorphosis took place within a week after the time of collection of post-larval S. japonicus from a river. The eruption of first functional teeth in the upper jaw of S. japonicus, which teeth are adapted to scraping algae off the substrate, was initially detected at 2 days after collection, and first functional dentition of the upper jaw was set up within 7 days after it.
authors.affiliation: Department of Hard Tissue Research, Graduate School of Oral Medicine, Matsumoto Dental University, Shiojiri, Nagano, Japan. Electronic address: sahara@po.mdu.ac.jp.
authors.forename: Noriyuki
authors.initials: N
authors.lastname: Sahara
authors.affiliation: Department of Pediatric Dentistry, Matsumoto Dental University, Shiojiri, Nagano, Japan.
authors.forename: Keita
authors.initials: K
authors.lastname: Moriyama
authors.affiliation: Sado Marine Biological Station, Faculty of Science, Niigata University, Sado, Niigata, Japan.
authors.forename: Midori
authors.initials: M
authors.lastname: Iida
authors.affiliation: Bioresource Science, Nihon University, Fujisawa, Kanagawa, Japan.
authors.forename: Shun
authors.initials: S
authors.lastname: Watanabe
mesh_terms: D000818:Animals; D021621:Imaging, Three-Dimensional; D007814:Larva / Q000254:growth & development; D008334:Mandible / Q000254:growth & development; D008437:Maxilla / Q000033:anatomy & histology* / Q000254:growth & development; D008675:Metamorphosis, Biological; D010473:Perciformes / Q000254:growth & development*; D045483:Rivers; D012886:Skull / Q000254:growth & development; D014070:Tooth / Q000254:growth & development; D014078:Tooth Eruption
keywords: Cranial metamorphosis; First functional teeth; Gobiid fish; Sicyopterus japonicus; Teleost; Upper jaw tooth