Abstract
Here, we present the results of a taxonomic survey of the nematodes parasitizing fishes from the lagoon flats of Palmyra Atoll, Eastern Indo-Pacific. We performed quantitative parasitological surveys of 653 individual fish from each of the 44 species using the intertidal sand flats that border the atoll’s lagoon. We provide morphological descriptions, prevalence, and mean intensities of the recovered seven species of adult nematode (Pulchrascaris chiloscyllii, Capillariidae gen. sp., Cucullanus bourdini, Cucullanus oceaniensis, Pseudascarophis sp., Spinitectus (Paraspinitectus) palmyraensissp. nov., Philometra pellucida) and three larval stages (Pulchrascaris sp., Hysterothylacium sp., Cucullanus sp.). We recorded: Pulchrascaris chiloscyllii from Carcharhinus melanopterus; Capillariidae gen. sp. from Chaetodon lunula, Lutjanus fulvus, and Ellochelon vaigiensis; Cucullanus bourdini from Arothron hispidus; Cucullanus oceaniensis from Abudefduf sordidus; Pseudascarophis sp. from Chaetodon auriga, Chaetodon lunula, and Mulloidichthys flavolineatus; Spinitectus (Paraspinitectus) palmyraensissp. nov. from Albula glossodonta; Philometra pellucida from Arothron hispidus; and three larval forms, Pulchrascaris sp. from Acanthurus triostegus, Acanthurus xanthopterus, Rhinecanthus aculeatus, Platybelone argalus, Carangoides ferdau, Carangoides orthogrammus, Caranx ignobilis, Caranx melampygus, Caranx papuensis, Chaetodon auriga, Chanos chanos, Amblygobius phalaena, Asterropteryx semipunctata, Valencienea sexguttata, Kyphosus cinerascens, Lutjanus fulvus, Lutjanus monostigma, Ellochelon vaigiensis, Mulloidichthys flavolineatus, Upeneus taeniopterus, Gymnothorax pictus, Abudefduf septemfasciatus, Abudefduf sordidus, and Stegastes nigricans; Hysterothylacium sp. type MD from Acanthurus triostegus, Carangoides ferdau, Chaetodon lunula, Chanos chanos, Kyphosus cinerascens, Abudefduf sordidus, and Arothron hispidus; and Cucullanus sp. from Caranx ignobilis. Spinitectus (Paraspinitectus) palmyraensissp. nov. (Cystidicolidae) is described from the intestine of roundjaw bonefish Albula glossodonta. All the nematode species reported in this study represent new geographical records. We discuss how our survey findings compare to other areas of the Indo-Pacific, and the way the relatively numerical dominance of trophically transmitted larval stages likely reflect the intact food web of Palmyra Atoll, which includes a large biomass of large-bodied top predator sharks and ray-finned fishes.
Highlights
Few studies have surveyed the parasites of all the fish species found in a habitat
Larvae identified as Pulchrascaris sp. are identical to those in the shark, and they could belong to the same species, but until studies on the life cycle or molecular analysis are carried out, we considered them as separate taxa
Several of the fish species we examined (16 of 44) were not parasitized by nematodes at all, even with large sample sizes for some fish species (e.g. Osteomugil engeli (Bleeker) (Mugilidae) n = 63, Istigobius ornatus (Rüppell) (Gobiidae) n = 26). Other fish species such as C. melanopterus, C. melampygus, C. papuensis, and E. vaigiensis with a single species of nematodes infecting them in this study (Table 1), have previous records of Terranova type II, Anisakis typica, Hysterothylacium type II, and Camallanus carangis (Deardorff et al 1982; Moravec et al 2006; Shamsi et al 2011; Jabbar et al 2012)
Summary
Few studies have surveyed the parasites of all the fish species found in a habitat. In the Eastern Indo-Pacific, several studies have reported parasitic nematodes of marine fishes from Australia, French Polynesia, Okinawa (Japan), Palawan (Philippines) Indonesia, off New Caledonia,and the Hawaiian Islands (Johnston and Mawson 1951; Schmidt 1969; Deardorff et al 1982; Lester and Sewell 1989; Bruce and Cannon 1990; Hasegawa et al 1991; Rigby et al 1997, 1999; Morand and Rigby 1998; Justine 2007; Lafferty et al 2008; Moravec and Justine 2010; Palm and Bray 2014; Moravec and Justine 2018). The survey by Lafferty et al (2008) is the only one to examine parasitic nematodes of marine fishes in Palmyra Atoll, listing helminths from five fish species in the fore-reef (a habitat adjacent to the one we surveyed); their analysis was limited to broad patterns of richness and abundance of morphospecies, conservatively grouped into broad taxonomic categories. Palmyra Atoll is one of the northern Line Islands located in the Eastern IndoPacific marine ecoregion (Spalding et al 2007), 1680 km south-south-west of Hawaii. It is a National Wildlife Refuge managed by the US Fish and Wildlife Service (The Nature Conservancy 2006), where visitation is restricted to a small staff and a few visiting scientists or volunteers. All fishing has been prohibited at Palmyra since it became a US National Wildlife Refuge in 2000, and before that, the atoll’s remoteness kept fishing pressure low) (Stevenson et al 2007)
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