DAO 21:7-11 (1995)  -  doi:10.3354/dao021007

Chemoresponse of actinosporean spores of Myxobolus cultus to skin mucus of goldfish Carassius auratus

Yokoyama H, Ogawa K, Wakabayashi H

ABSTRACT: Chemoresponse of actinosporean spores of Myxobolus cultus to goldfish mucus was studied and determination of the reactants was attempted. Reactivity was counted as the percentage of empty actinosporean spores after mixing with the mucus. The activity of mucus was maintained at -80*C, but was mostly lost within 1 d at 5*C. Heating at 30 to 80*C for 30 min did not affect the activity. While neutral pH favored the reaction, strong acid and alkali decreased the reaction. Phosphate buffer saline and sodium chloride solutions with molarity >0.05 M inhibited the reaction. A shrinkage of sporoplasms inside the epispore cavity caused by the high osmotic pressure was observed. Purification of the reactants from goldfish mucus by gel filtration and ultrafiltration revealed that they were low-molecular-weight substances (< 6000 MW). Additionally, fish mucus from other fish species (such as common carp Cyprinus carpio, loach Misgurnus anguillicaudatus, rainbow trout Oncorhynchus mykiss, catfish Parasilurus asotus, and Japanese eel Anguilla japonica), as well as mucin from bovine submaxillary gland were similarly active. It is suggested that actinosporean spores recognize fish hosts with low-molecular-weight mucin components in skin mucus, and that the portal of entry is the outer surface of fish.

KEY WORDS: Myxosporean . Actinosporean . Myxobolus cultus . Goldfish . Carassius auratus . Skin mucus

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