DAO 109:251-256 (2014)  -  DOI: https://doi.org/10.3354/dao02744

NOTE
Azumiobodo hoyamushi, the kinetoplastid causing soft tunic syndrome in ascidians, may invade through the siphon wall

Euichi Hirose1,*, Akira Kumagai2, Akatsuki Nawata3, Shin-Ichi Kitamura4,5

1Department of Chemistry, Biology and Marine Science, Faculty of Science, University of the Ryukyus, Nishihara, Okinawa 903-0213, Japan
2Miyagi Prefecture Fisheries Technology Institute Freshwater Fisheries, Experimental Station, Taiwa, Miyagi 981-3625, Japan
3Miyagi Prefecture Fisheries Technology Institute, Ishinomaki, Miyagi 986-2135, Japan
4Department of Biology, Faculty of Science, Ehime University, Matsuyama, Ehime 790-8577, Japan
5Center for Marine Environmental Studies (CMES), Ehime University, Matsuyama, Ehime 790-8577, Japan
*Corresponding author:

ABSTRACT: The infectious kinetoplastid Azumiobodo hoyamushi causes ‘soft tunic syndrome’, a serious problem in aquaculture of the edible ascidian Halocynthia roretzi. Infection tests using diseased tunics demonstrated that juvenile (0.8 yr old) individuals never developed soft tunic syndrome, but all individuals in the other age groups (1.8, 2.8, and 3.8 yr old) showed the disease symptoms. In the infection tests, tunic softening was first observed at the tunic around siphons. Based on ultrastructural observation of the inner wall of the branchial siphon, the tunic lining the inner wall in juveniles (0.5 yr old) was completely covered with cuticle, which had a dense structure to prevent bacterial and protist invasion. In contrast, the tunic was often partly damaged and not covered with cuticle in healthy adults (≥2.5 yr old). The damaged tunic in the siphon wall could be an entrance for A. hoyamushi into the tunic of adult hosts.


KEY WORDS: Halocynthia roretzi · Edible ascidian · Aquaculture · Age-dependent susceptibility · Tissue damage · Tunic cuticle · Ultrastructure


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Cite this article as: Hirose E, Kumagai A, Nawata A, Kitamura SI (2014) Azumiobodo hoyamushi, the kinetoplastid causing soft tunic syndrome in ascidians, may invade through the siphon wall. Dis Aquat Org 109:251-256. https://doi.org/10.3354/dao02744

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