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Bacterial enteritis and the development of the larval digestive tract in olive flounder, Paralichthys olivaceus (Temminck & Schlegel)
Author(s) -
Kim DH,
Han HJ,
Kim SM,
Lee DC,
Park SI
Publication year - 2004
Publication title -
journal of fish diseases
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.819
H-Index - 85
eISSN - 1365-2761
pISSN - 0140-7775
DOI - 10.1111/j.1365-2761.2004.00553.x
Subject(s) - paralichthys , olive flounder , biology , microbiology and biotechnology , vibrio anguillarum , pepsin , brine shrimp , edwardsiella tarda , enteritis , stomach , litopenaeus , bacteria , gene , enzyme , fishery , vibrio , shrimp , biochemistry , fish <actinopterygii> , genetics
Three bacterial isolates obtained from diseased olive flounder larvae, Paralichthys olivaceus , were identified as Vibrio ichthyoenteri based on the results of phenotypic characterization and 16S rRNA gene sequencing studies. Bacterial enteritis was reproduced in 16 and 22 days post‐hatch (dph) larvae by administering brine shrimp nauplii, Artemia salina , dosed with the environmental isolates and reference strains of V. ichthyoenteri . To investigate the effect of the disease on development of the stomach, a pepsin activity assay and reverse transcription‐polymerase chain reaction (RT‐PCR) analysis of the expression of the pepsinogen gene were performed. Expression of olive flounder pepsinogen was detected from 30‐dph larvae and the increased level of pepsin activity coincided with reduced susceptibility to the disease. Growth rates of V. ichthyoenteri , V. anguillarum and Edwardsiella tarda were tested in artificial stomach conditions using HCl and porcine pepsin. All the strains of V. ichthyoenteri were inhibited by low pH conditions which corresponded with an increase in pepsin levels. This suggests that differentiation of the stomach in olive flounder larvae and juveniles, an essential physiological development, also provides the host with a non‐immunological defence mechanism.