Resolution of the identity of three species of Diplostomum (Digenea: Diplostomidae) parasitising freshwater fishes in South Africa, combining molecular and morphological evidence

Abstract

Reliable data on the diversity of the genus Diplostomum (Digenea: Diplostomidae) parasitising freshwater fishes in South Africa, as well as in Africa, is almost non-existent. Most of the morphology-based identifications of species within this genus reported from Africa require critical revision. The aim of the present study was to determine the diversity of Diplostomum metacercariae in South African fishes applying molecular and traditional morphological techniques. To achieve this aim, a total of 216 fishes belonging to 21 species collected in the Rivers Phongolo, Riet, Usuthu and Mooi in three provinces of South Africa were examined. Metacercariae of Diplostomum were recovered from the eye lenses of 38 fishes belonging to five species of the families Anguillidae, Cichilidae and Mochokidae, with an overall low prevalence of infection (18%). Metacercariae were subjected to morphological study and molecular sequencing of the partial mithochondrial cox1 and ribosomal 28S rDNA genes as well as of ribosomal ITS1-5.8S-ITS2 region. Morphological and phylogenetic analyses revealed the presence of three species which matched those previously reported from Nigeria, Iraq and China, therefore those from Tilapia sparrmanii and Synodontis zambezensis were named Diplostomum sp.; those from Anguilla labiata, Oreochromis mossambicus and S. zambezensis were named Diplostomum sp. 14; and those from Pseudocrenilabrus philander were named Diplostomum sp. 16. Geographic distribution of several species of Diplostomum appeared to be wider than expected. Morphological description and novel sequence data generated during this study will contribute to the elucidation of the life cycles of Diplostomum sp., Diplostomum sp. 14 and Diplostomum sp. 16 and advance further research of diplostomids in Africa.

Parasites of Oreoleuciscus potanini (Cyprinidae) from lakes of Khar Us Nuur National Park (Mongolia)

“…They were less numerous in fish from the lakes Khar and Khar Us only. Diplostomum pseudospathaceum seems to have the same list of hosts as D. spathaceum (Pérez-del-Olmo et al, 2014;Locke et al, 2015;Hoogendoorn et al, 2020). The host range and geographical distribution of Diplostomum sp.…”

“…But in general, P. torulosus is a widespread parasite of Cyprinidae fish in the Holarctic (Anikieva et al, 1987;Pugachev, 2002;Anikieva, 2004). The trematodes Diplostomum spp., Posthodiplostomum brevicaudatum, Ornithodiplostomum scardinii, and Tylodelphys clavata are common in the Palearctic waters (Locke et al, 2015;Stoyanov et al, 2017;Hoogendoorn et al, 2020). Allocreadium isoporum is a widespread parasite of Cyprinidae fish in the Palearctic (Petkevičiūtė et al, 2010), while the status and biology of Allocreadium transversale, as well as its distribution, need further research.…”

“…Some of the investigations concerned the parasite communities and species composition in different fish species (Mudry & Anderson, 1977;Boomker, 1994;Murcia et al, 2006;Morozińska-Gogol, 2007, 2009Butorina et al, 2008;Shukerova & Kirin, 2008;Moravec & Bakenhaster, 2010;Sandlund et al, 2010;Shukerova et al, 2010Shukerova et al, , 2017Sokolov & Gordeev, 2014;Chunchukova et al, 2016;Chunchukova & Kirin, 2018;Rubtsova & Kutsokon, 2018;Utevsky et al, 2018). Other studies devoted to different systematic groups include data on fish parasites in Protected Areas (Sasal et al, 2004;Galli et al, 2007;Kirjušina & Vismanis, 2007;Székely et al, 2009;Wood et al, 2013;Halajian et al, 2018;Hoogendoorn et al, 2020). Some results make it possible to describe new parasite species or revise previous data on morphology, molecular characteristics and phylogeny, host specificity of fish parasites in Protected Areas (Moravec, 2001;Székely et al, 2012;Borkhanuddin et al, 2014;Stunžėnas et al, 2014;Molnár et al, 2015;Presswell & Blasco-Costa, 2019;Scholz et al, 2019).…”

Conserving Freshwater Biodiversity in an African Subtropical Wetland: South Africa’s Lower Phongolo River and Floodplain

“…Before the present study the only fish parasites recorded from the PR was two monogenean species by Price et al [71] from the gills of Tilapia sparrmanii and Enteromius trimaculatus, respectively (see [72]). Svitin et al [73] studied the diversity of camallanid nematodes from two catfishes, providing novel information on their morphology and genetic data; Hoogendoorn et al [74] studied the diversity of digenean metacercariae (Diplostomidae) and also provided novel information on the morphology and genetic data of these parasites from freshwater fishes; Smit et al [75] recorded for the first time trypanosomes in freshwater fish and in their leech vectors from this region, providing morphological and molecular characterisation Table 2 and some of the fish parasites are shown in Figure 9. Amphibians are well suited hosts for parasites, as most parasites rely on aquatic infective stages for transmission and reproduction, much in the same way that amphibians depend on extended exposure to aquatic systems for reproduction and their life history.…”

Molecular and morphological characterisation of Diplostomum phoxini (Faust, 1918) with a revised classification and an updated nomenclature of the species-level lineages of Diplostomum (Digenea: Diplostomidae) sequenced worldwide

“…Intensive sampling and molecular analyses predominantly of the larval stages of Diplostomum spp. from their intermediate hosts, freshwater lymnaeid snails and fishes, have resulted in delineation of more than 40 species/species-level lineages (Locke et al, 2010a(Locke et al, , 2010b(Locke et al, , 2015(Locke et al, , 2020Georgieva et al, 2013;Blasco-Costa et al, 2014;Faltýnková et al, 2014;Pérez-del-Olmo et al, 2014;Selbach et al, 2015;Kudlai et al, 2017;Soldánová et al, 2017;Gordy and Hanington, 2019;Hoogendoorn et al, 2020;Lebedeva et al, 2021). Complete mitochondrial genomes have been characterised for four species, Diplostomum spathaceum (Rudolphi, 1819) and D. pseudospathaceum Niewiadomska, 1984 (see Brabec et al, 2015), D. ardeae Dubois, 1969 (see Locke et al, 2020) and Diplostomum baeri Dubois, 1937 (see Landeryou et al, 2020).…”