Parasitic copepods (Crustacea, Hexanauplia) on fishes from the lagoon flats of Palmyra Atoll, Central Pacific

Caligusselenecola sp. nov. (Siphonostomatoida, Caligidae) parasitic on the hairfin lookdown Selenebrevoortii (Gill) from the Gulf of California, Mexico, with some comments on Caritustolii Rangnekar, 1984

Specimens of a caligid copepod (Siphonostomatoida) were found on the gills of the hairfin lookdown Selenebrevoortii (Gill) (Carangidae) from off Mazatlán, Sinaloa (north-western Mexico). This material represents a new species of Caligus, C.selenecola sp. nov., and is assigned to the diaphanus species group. Within this group, only C.kapuhili Lewis, 1967, C.laticaudus Shiino, 1960, C.macrurus Heller, 1865, and C.selenecola sp. nov., have been described with a reduced outer spine 1 on the second exopodal segment of leg 1. These four species can be readily separated by the relative length of the abdomen, and the presence/absence of a process on the myxal area of the female maxilliped, the sternal furca, the postantennal process, and the spiniform process on the basal antennary segment. A full description of the new species is given with some comments on Caritustolii Rangnekar, 1984.

First record of Caligusdussumieri Rangnekar, 1957 (Copepoda, Siphonostomatoida, Caligidae) from Malaysia, with notes on caligids found from Malaysia and on host-specificity of caligids on lutjanid fishes

Background

In total, 14 species of Caligus have been reported from Malaysia. Amongst them, four species are reported from lutjanid fishes.

New information

Caligusdussumieri Rangnekar, 1957 is reported from Malabar snapper, Lutjanusmalabaricus, purchased from a local wet market in Terengganu, Peninsular Malaysia. This is the first record of this species in Malaysia and it is only the second species assigned to the bonito-group of the genus Caligus to be reported from Malaysia. A key to species of the bonito-group is presented herein. The list of caligids infecting lutjanid fishes and the geographical distributions plus the known hosts of members of the bonito-group of Caligus are discussed.

Parasite communities of the golden snapper Lutjanus inermis (Perciformes: Lutjanidae): inter-annual variations during strange climatic events

Strange oceanographic events such as El Niño and La Niña may have indirect effects on the local transmission processes of intestinal parasites due to the reduction or increase in populations of potential intermediate or definitive hosts. A total of 713 individuals of Lutjanus inermis (Peters) were collected over an 8-year period (October 2015 to July 2022) from Acapulco Bay, Mexico. Parasite communities in L. inermis were quantified and analysed to determine if they experienced interannual variations in species composition and structure as a result of local biotic and abiotic factors influenced by oceanographic events, such as El Niño-Southern Oscillation (ENSO), or La Niña, the cool phase of the ENSO climate pattern. Twenty-six taxa of metazoan parasites were recovered and identified: two Monogenea, eight Digenea, two Acanthocephala, four Nematoda, one Cestoda, seven Copepoda, and two Isopoda. Species richness at the component community level (8 to 17 species) was similar to reported richness in other species of Lutjanus Bloch. Parasite communities of L. inermis exhibited high inter-annual variation in the abundance of component species of parasite. However, the species richness and diversity were fairly stable over time. Climatic episodes of El Niño and La Niña probably generated notable changes in the structure of local food webs, thus indirectly influencing the transmission rates of intestinal parasite species. Changes in species composition and community structure of parasites possibly were due to variations in feeding behaviour during the events and differences in the host body size.

Metazoan parasite communities of the Pacific red snapper, Lutjanus peru (Perciformes: Lutjanidae): interannual variations in parasite communities

Metazoan parasite communities can experience temporal structural changes related to seasonal and/or local variations in several biotic and abiotic environmental factors. However, few studies have addressed this issue in tropical regions, where changes in water temperature are less extreme than in temperate regions, so the factors or processes that can generate variations in these parasite communities are as yet unclear. We quantified and analysed the parasite communities of 421 Lutjanus peru (Nichols & Murphy, 1922) collected from Acapulco Bay in Guerrero, Mexico, over a four-year period (August 2018 to April 2021), to identify any interannual variation due to local biotic and abiotic factors influenced by natural oceanographic phenomena, such as El Niño-Southern Oscillation, or La Niña. Twenty-five metazoan parasite taxa were recovered and identified: seven Digenea species; two Monogenea; one Cestoda; one Acanthocephala; four Nematoda; and ten of Crustacea (seven Copepoda and three Isopoda). The digeneans and copepods were the best represented parasite groups. The parasite communities were characterized by a high numerical dominance of helminth larvae. Species richness at the component community level (13 to 19 species) was similar to reported richness in other Lutjanus spp. The parasite communities of L. peru had a high variability in species composition, but low aggregate variability (e.g. species diversity), suggesting that structure of these communities may be quite stable over time. A clear interannual variation pattern was not observed, suggesting that parasite species of this host may respond differently to variations in environmental factors. Interannual variations were possibly caused by a combination of biotic (i.e. host feeding behaviour and body size) and local abiotic factors (influenced by climatic anomalies) which generated notable changes in the infection levels of several component species.

Interannual variation in the metazoan parasite communities of bigeye trevally Caranx sexfasciatus (Pisces, Carangidae)

Parasite communities in Caranx sexfasciatus were characterized and analyzed to determine any interannual variations in structure and/or species composition. In total, 422 C. sexfasciatus were collected from Acapulco Bay, Mexico, between May 2016 and March 2019. Thirty-two taxa of metazoan parasites were identified: five Monogenea, thirteen Digenea, one Acanthocephala, one Cestoda, three Nematoda, seven Copepoda, and two Isopoda. Monogeneans were the most frequent and abundant parasite species in all sampling years. Parasite species richness at the component community level varied significantly from 8 (May 2016) to 25 (March 2019) and was similar to previous reports for other species of Carangidae. The component communities and infracommunities in C. sexfasciatus were characterized by low parasite species numbers, low diversity, and dominance of a single species (the monogenean Neomicrocotyle pacifica). Parasite community structure and species composition varied between sampling years and climatic seasons. Seasonal or local fluctuations in some biotic and abiotic environmental factors probably explain these variations.

Parasitic nematodes of marine fishes from Palmyra Atoll, East Indo-Pacific, including a new species of Spinitectus (Nematoda, Cystidicolidae)

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.