Occurrence of the parasite Ergasilus intermedius (Copepoda Ergasilidae) on the gills of Macquarie perch, Macquaria australasica (Percichthyidae)

B.A. Ingram, A.W. Philbey

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The parasitic cyclopoid copepod Ergasilus intermedius is recorded for the first time on the threatened Macquarie perch, Macquaria australasica, which represents the most southerly record of this parasite. Infestations (up to 50 parasites per gill arch) have been observed on broodfish (310-360 mm total length, 270-750 g weight) held in earthen ponds; 47% of fish examined in 1987 and 24% of fish examined in 1988 were infested. Attachment of E.intermedius to the gills induced chronic, segmental branchitis, characterised by localised epithelial hyperplasia, lamellar fusion and mucous metaplasia adjacent to the constriction caused by the clasping antennae. Infested fish held in 2000 L tanks were successfully treated with a single application of 2.0 mg/L Dipterex® for 24 hours. Lower dosages of Dipterex (0.15 and 1.5 mg/L) and other chemicals, such as NaCl and NaCl plus methylene blue in tanks, and malachite green in ponds, failed to eradicate the parasite. Discrepancies in the identity and source of the type host of E. intermedius are discussed. Potential implications for M. australasica conservation programs are briefly outlined.
Original languageEnglish
Pages (from-to)39-44
Number of pages6
JournalProceedings of the Linnean Society of New South Wales
Issue number121
Publication statusPublished - 1 Jan 1999


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