World Aquaculture Magazine - September 2021

WWW.WA S .ORG • WORLD AQUACULTURE • SEP TEMBER 2021 59 ( C O N T I N U E D O N P A G E 6 0 ) surface and buccal cavities of five fish hosts, four species of isopods were identified. Cymothoa eremita and Lobothorax typus were collected from the buccal cavities of Indian halibut Psettodes erumei and largehead hairtail Trichiurus lepturus , respectively. Nerocila longispina was collected from the body surface of spiny-cheeked grunter Terapon puta while Nerocila loveni was collected from the body surfaces of both Dorab wolf herring Chirocentrus dorab and tigertooth croaker Otolithes ruber . It is the first study that recorded C. dorab as a host for N. loveni as the isopod had only been recovered from ponyfish Leiognathus sp. Of the isopod species collected, two have been documented in the Philippines, namely, C. eremita and L. typus . In separate study, 14 species of cymothoid isopods were found in commercially important Malaysian fish species (Anand Kumar et al. 2016). Fish parasites may also be potential biological indicators of ecosystem health. In Indonesia, 189 fish samples consisting of seven fish species collected from a brackishwater lagoon divided into three areas with varying environmental conditions showed a total of 43 species of both ecto- and endoparasites belonging to seven taxa (Rueckert et al. 2009). In the area with higher salinity located near the Indian Ocean, only one marine cymothoid species was found in the buccal cavity of spotted scat Scatophagus argus , with a prevalence of 29 percent. The cymothoid species was not found in other areas of the lagoon because of the lower salinity attributed to freshwater coming from nearby rivers. Cymothoid Isopods in the Philippines Cases of ispopods have been reported in water bodies throughout the Philippines including Sulu Sea, Puerto Galera, Fishing Port Complex in Iloilo City, Panay Gulf, and Lingayen Gulf (Yamauchi et al. 2005, Williams and Madad 2010, Cruz-Lacierda and Nagasawa 2017a, Cruz-Lacierda and Nagasawa 2017b, Bruce and Shimomura 2019). Reports of cymothoid infection in the country were published more than a decade ago (Bruce and Harrison-Nelson 1988, Williams and Bunkley-Williams 1992, Yamauchi et al. 2005). Recent studies on isopod infection of Philippine fish species are few and limited. The most recent study described Corallana spp. on Nile tilapia Oreochromis niloticus (Adorador et al. 2006). N. indica infection of S. crumenophthalmus was first recorded in the Philippines in Panay Gulf, Iloilo (Cruz-Lacierda and Nagasawa 2017a). A total of 81 bigeye scads were examined and prevalence of the cymothoid isopod ranged from 13 to 47 percent. The isopods were asymmetrically shaped to match the shape of the branchial cavity of the bigeye scad. Infection takes place in young fish hosts and the parasite develops along with it. However, such relationship was not observed between the fish hosts and ovigerous female isopods. Infection by cymothoid isopods in the family Gnathiidae of orange-spotted grouper E. coioides was also recorded in Lingayen Gulf, Philippines (Cruz-Lacierda and Nagasawa 2017b). From 17 fish species, there was a prevalence rate of 82 percent on gills and 24 percent in the branchial cavity, with mean intensities of 2.2 and 2.5, respectively. Isopods were connected to hosts through their mouthparts and fed on the host’s blood. Prevalence rates were lower compared to previous reports due to the smaller lengths of the fish samples; this supported a positive correlation between fish size and isopod larvae infection (Heupel and Bennett 1999). were found in the fish, five of which are pathogenic to humans ( Aeromonas hydrophila , Pseudomonas fluorescens , Pseudomonas putida , Citrobacter , and Mycobacteriummarinum ) (Rameshkumar et al. 2013b). Cymothoid Isopods in Southeast Asia Cymothoid isopods are widely distributed along the tropical waters of Southeast Asia, infecting commercially important marine teleost fish of countries such as the Philippines, Thailand, Indonesia and Malaysia (Behera et al. 2016). Although limited, there have been a few studies investigating the incidence of these isopods in Southeast Asian countries. Nagasawa and Petchsupa (2009) recorded N. indica infections of bigeye scad S. crumenophthalmus in the southernmost coast of Thailand. Sixty fish samples were collected between October 2008 and March 2009, with 51 infecting the gill cavity. Isopods were twisted to the right side when attached to the left gill cavity and to the left side when attached to the right. In a separate study, N. indica infections among 155 fish samples from seven different species were examined, but only S. crumenophthalmus was actually infected (Intamong and Kaewviyudth 2014). Fish samples were collected between November 2013 and February 2014, with 117 isopods in the branchial cavities of 49 hosts, resulting in a prevalence of 32 percent. It is the first record of N. indica infection in the easternmost coast of Thailand, indicative of its wide distribution in Southeast Asia. Another study described Anilocra sp. infection of S. crumenophthalmus in Indonesia (Perdana et al. 2019). Anand Kumar et al. (2013) recorded cymothoid parasitic isopods in marine fishes fromMiri, east Malaysia. From the body Ergasilid copepods are attached to the gill filaments of this grouper, readily seen with the naked eye. Over 60 species of ergasilids parasitize freshwater fishes and over 30 species infect marine bony fish (Photo: E. Cruz-Lacierda).