First record of Caligus mutabilis (Copepoda: Caligidae), in sea-farmed Mycteroperca microlepis (Perciformes: Serranidae) in Brazil

Sea lice (copepods) are widespread pathogens in marine teleost cultivation around the world. The sea louse Caligus mutabilis Wilson, 1905, is recorded here for the first time in sea-farmed gag grouper, Mycteroperca microlepis, in Brazil.

Mycteroperca microlepis (Goode & Bean, 1879) is a fish species in the Serranidae family that is distributed from Massachusetts (northeastern United States) to Santa Catarina (southeastern Brazil), and is frequently cultivated in fish farms because of its high growth potential (FIGUEIREDO;MENEZES, 1980;SANCHES et al., 2008a, b). This species is listed as presenting least concern by International Union for Conservation of Nature and Natural Resources (IUCN Red List), although its current population trend in the wild is decreasing (BERTONCINI et al., 2011), and in Brazil it is overexploited in the state of São Paulo (SÃO PAULO, 2010;SANCHES et al., 2010).
Sea lice are copepods belonging to the Caligidae family within the order Siphonostomatoida. There are 36 genera within this family, which include approximately 107 Lepeophtheirus and 239 Caligus species (HO et al., 2000). Sea lice are ectoparasites that feed on the mucus, epidermal tissue and blood of marine fish, and they are among the most notorious pests affecting cultivated marine fish. These copepods erode fishes epithelium and consequently damage their eyes, thus leading to corneal ulceration and secondary bacterial infection. Cataracts and blindness interfere with feeding and result in further loss of condition. Cage cultivation of nonsalmonids is also developing rapidly around the world, and sea lice are becoming increasingly associated with mortality and disease in these fish species too (BOXSHALL; DEFAYE, 1993;LESTER;HAYWARD, 2006).
The genus Caligus includes crustacean ectoparasites that are highly pathogenic to fish, with numerous reports worldwide (HO et al., 2000). According to Luque and Tavares (2007), 24 species of Caligus are found along the Brazilian coast parasitizing 57 fish species. In this paper, we present the first record of a sealouse species (Caligus mutabilis) in farmed fish in Brazil.
Specimens of copepods were collected from cultivated Mycteroperca microlepis (wet weight 4.0 ± 0.3 kg) that were kept in concrete tanks of volume 80 m 3 , in a marine farm at Ilhabela, state of São Paulo, Brazil. Fishes were collected on the rocky shoreline near the site of cultivation and were fed with sardines. After collection, the copepods were fixed and preserved in ethanol (70% GL) and were clarified with lactic acid for identification. Measurements were made in millimeters (mm). The taxonomic determination of the parasites was in accordance with the diagnosis proposed by Cressey and Cressey (1980). Voucher specimens of C. mutabilis (two male and two females) were deposited in the Crustacea Collection of the National Museum, Rio de Janeiro (MNRJ No 23299, 23300). The parasites collected on M. microlepis were spread across the body surface, and were most frequently observed in the fish cephalic region and mouth. The specimens of copepods collected showed great mobility, which caused intense itching that drove the fish to scrape themselves against the floor and walls, thereby causing mucus removal and skin lesions.
The following measurements were made on the specimens of C. mutabilis Wilson, 1905 Caligus mutabilis was originally described by Wilson (1905). Subsequently, Cressey and Cressey (1980) made a detailed redescription with specimens collected from scombrid fish. The specimens collected in the present study corroborate the data collected by Cressey and Cressey (1980). On the coast of the Rio de Janeiro state it is a well-known species and has previously been recorded in fish of the families Carangidae, Scombridae, Sparidae and Ephippidae TAVARES, 2007).
In wild fish stocks high levels of infection are occasionally pathogenic. Regarding the infection site and the life cycle characteristics of this pathogen, the high population density of farmed groupers might favor its dissemination, thereby increasing the parasite burden, since they can migrate from host to host, facilitating rapid spread (LUQUE, 2004). The first record of parasitic copepods in groupers in Brazil was made by Luque et al. (1998), who observed the copepod Lepeophtheirus curtus in black grouper (Mycteroperca bonaci). In other species of marine fish with a potential for cultivation, there are some records of caligid copepods. For example, Caligus bonito (Wilson, 1905) was observed in the gills of the mullet Mugil platanus, off the coast of Rio de Janeiro, with a prevalence of 13.3% (KNOFF et al., 1994). Tavares and Luque (2001) recorded Caligus praetextus Bere, 1936, in juvenile snook (Centropomus undecimalis) from Rio de Janeiro with a prevalence of 11.4%. More recently, Robaldo et al. (2002) observed Caligus sp. parasitizing the Brazilian flounder Paralichthys orbignyanus in captivity. Another well-known example is the caligid copepods of the genus Lepeophtheirus, which have caused mortalities among non-salmonid fishes in Asia (BOXSHALL; DEFAYE, 1993;HO et al., 2000).
Since cultivation of non-salmonids is also developing in Brazil, sea lice may be associated with mortality and disease in these fishes. Since significant numbers of caligid species have been recorded along the Brazilian coast, cultivation of marine fish species may be highly affected, thus making it very important to study these parasites with a view to control and prophylaxis (LUQUE, 2004).