Accumulation of organotin compounds and marine birnavirus detection in Korean ascidians

Abstract

Recently, a serious disease spread extensively in aquaculture sites of the ascidian Halocynthia roretzi in Korea. To understand circumstances of ascidians in Korean aquaculture sites, residue levels of organotin compounds were analyzed, and detection of a marine birnavirus (MABV) in tissues of H. roretzi was attempted. Korean H. roretzi showed high concentrations of butyltins (mono, di, and tributyltins), especially in the gill, hepatopancreas, and digestive tract. However, there was no significant difference in the residues of butyltins in the hepatopancreas between diseased and non-diseased ascidians. The positive rate of MABV detection was high in the hepatopancreas, but also no significant difference was observed between diseased and non-diseased individuals. These observations suggest that an accumulation of tributyltin and a latency of MABV in H. roretzi tissues does not directly relate to the occurrence of the disease.

Azumiobodo hoyamushi gen. nov. et sp. nov. (Euglenozoa, Kinetoplastea, Neobodonida): a pathogenic kinetoplastid causing the soft tunic syndrome in ascidian aquaculture

“…In the diseased ascidians, the tunics become abnormally thin and soft; the ascidian then dies when the tunic tears. Several attempts have been made to identify the causative agent, and the pathogenic organism of the disease has recently been identified (Jung et al 2001, Choi et al 2006, Azumi et al 2007a,b, Hirose et al 2009, Kitamura et al 2010. Kumagai et al (2010) induced experimental infections by incubating healthy individuals with pieces of softened tunics and found flagellates in the softened tunic.…”

Mass mortality of cultured ascidians Halocynthia roretzi associated with softening of the tunic and flagellate-like cells

“…Hirose et al (2009) also did not find any morphological changes or virus-like particles in the tunic epidermal cells of affected animals using electron microscopy. Although marine birnavirus was detected in various tissues of the ascidian, there was no correlation between the virus detection and the disease (Azumi et al 2007a). Bacterial etiology is also unlikely, since pathogenicity of tunics can be lost by mincing with a food processor.…”

“…Although investigations have been conducted on the soft tunic syndrome in Korea, the cause of the disease is still unknown (Jung et al 2001, Azumi et al 2007a. Because experimental infections of the disease have not been carried out, it is still uncertain whether the disease is infectious or not.…”

Gene Promoter Variation of Phosphoglycerate Kinase, a Glucose Metabolism Enzyme, is a Biomarker for Selection of Disease-resistant Sea Squirt, Halocynthia Roretzi

“…Because the tunics of the diseased ascidians are always thinner and softer than those of healthy individuals, the soft tunic is the most remarkable clinical sign of the disease. Although there is debate regarding the disease-causing agent, it has not yet been identified [1,4]. The tunic is a leathery or gelatinous matrix that entirely covers the epidermis of ascidians.…”