Abstract
The African continent has a rich diversity of fish and amphibians in its inland water systems that serve as hosts for monogeneans of seven genera of the Gyrodactylidae van Beneden et Hesse, 1832. In August 2011, eight gyrodactylid parasites were collected from the gills of two specimens of bulldog, Marcusenius macrolepidotus (Peters), from Lake Kariba, Zimbabwe. Morphometric evaluation and sequencing of 18S rDNA confirmed that the specimens represented a species of a new viviparous genus, Tresuncinidactylus wilmienae gen. et sp. n. The attachment apparatus consists of a single pair of large slender hamuli with prominently flattened roots that are connected by a simple, narrow dorsal bar. The ventral bar is small and possesses a thin lingulate membrane but no evident anterolateral processes. There are 16 marginal hooks of one morphological type, but of three different sizes, with large falculate sickles that are proportionaly equal in length to the length of their handles. The two largest pairs of marginal hooks are positioned closest to the opisthaptoral peduncle, the neighbouring two pairs of medium-sized marginal hook sickles are situated along the lateral margins of the opisthaptor. Four pairs of smallest marginal hooks are positioned along the posterior margin of the opisthaptor. The male copulatory organ consists of a muscular pouch armed with approximately 30 gracile spines. Phylogenetic analyses of partial sequences of the 18S rDNA using Maximum Likelihood and Bayesian Inference placed the new genus within the lineage of solely African genera and suggests Afrogyrodactylus Paperna, 1968, Citharodactylus Přikrylová, Shinn et Paladini, 2017 and Mormyrogyrodactylus Luus-Powell, Mashego et Khalil, 2003 as genera most closely related to the new genus.
Highlights
The family Gyrodactylidae van Beneden et Hesse, 1832 currently contains 24 valid genera of viviparous monogeneans (Boeger et al 2020)
The internal transcribed spacers (ITS), 5.8S and 18S rDNA regions have become most used in studies on taxonomy, phylogeny and cophylogeny (Huyse et al 2002, Gilmore et al 2012, Přikrylová et al 2013, García-Vásquez et al 2018, 2019, Boeger et al 2020)
The presence of a developing embryo within the uterus of a few specimens indicated that the specimens were viviparous and that they belong to the Gyrodactylidae, but the overall arrangement of the opisthaptoral hard parts, as well as the unique morphology of the male copulatory organ (MCO), indicated that the discovery represented a new genus
Summary
The family Gyrodactylidae van Beneden et Hesse, 1832 currently contains 24 valid genera of viviparous monogeneans (Boeger et al 2020). Seven gyrodactylid genera are currently known from Africa of which six are geographically limited to this continent (Přikrylová et al 2017a, Řehulková et al 2018) These genera are Afrogyrodactylus Paperna, 1968, Citharodactylus Přikrylová, Shinn et Paladini, 2017, Diplogyrodactylus Přikrylová, Matějusová, Musilová, Gelnar et Harris, 2009, Gyrdicotylus, Macrogyrodactylus Malmberg, 1957, and Mormyrogyrodactylus Luus-Powell, Mashego et Khalil, 2003. While ITS and 5.8S rDNA sequences have limited utility for investigating phylogeny within the Gyrodactylidae at the intergeneric level (Vanhove et al 2011, Přikrylová et al 2013), they are suitable for inferring relationships within the genus Gyrodactylus (see Cable et al 1999, Matějusová et al 2001, Gilmore et al 2012). 18S rDNA sequences are available for 14 of the 23 genera within the Gyrodactylidae, including five African genera (Kritsky et al 2013, Přikrylová et al 2013)
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