Unexpected response of a captive blackeye thicklip, Hemigymnus melapterus (Bloch), from Lizard Island, Australia, exposed to juvenile isopods Gnathia aureamaculosa Ferreira & Smit

Abstract

Gnathiid isopods (Crustacea: Isopoda: Gnathiidae) have complex, biphasic life cycles demonstrating protelian parasitism; the reproductive adults are freeliving, and the juveniles are haematophagous ectoparasites feeding on either teleost or elasmobranch fish (Raibaut & Trilles 1993; Smit & Davies 2004). Pathological effects resulting from gnathiid blood feeding are reported in aquaria, fish farming and in the wild (Marino, Giannetto, Paradiso, Bottari, De Vico & Macri´ 2004; Smit & Davies 2004; Jones & Grutter 2005; Hayes, Smit & Davies 2007). The action of cleaner fish in removing juvenile gnathiids from client fish on coral reefs has been well recognized in recent years, especially on the Great Barrier Reef (GBR), Australia (Grutter 2008; Grutter, Pickering, McCallum & McCormick 2008; Penfold, Grutter, Kuris, McCormick & Jones 2008). However, relatively little is known of the rapid, direct effects of juvenile gnathiids feeding on their hosts in this ecological system. Here, we report briefly on the death and associated histopathology observed when a specimen of captive H. melapterus (Teleostei: Labridae) was experimentally exposed to juveniles of Gnathia aureamaculosa Ferreira & Smit (in Ferreira, Smit, Grutter & Davies 2009) at Lizard Island Research Station, GBR, Australia (14°40′S; 145°28′E), in 2004.