Phylogenetic status and historical origins of the oviparous and viviparous gyrodactylids (Monogenoidea, Gyrodactylidea)

Abstract

Phylogenetic analyses of sequences of the 18S rDNA and MT‐CO2 gene fragments indicated that the oviparous and viviparous gyrodactylid‐like monogenoids formed independent monophyletic clades within the Order Gyrodactylidea, supporting the reinstatement of the Oogyrodactylidae and limiting the Gyrodactylidae to the viviparous species. Analyses further indicated that the clade comprising the two families shared a common ancestor with the Udonellidae. Two clades, that of Aglaiogyrodactylus and that of Phanerothecium, were identified within the Oogyrodactylidae, while Onychogyrodactylus was shown to be polyphyletic and Oogyrodactylus basal within the family. One putative synapomorphy was identified for the Oogyrodactylidae, that is presence of a massive Mehlis’ gland. The Gyrodactylidae was limited to species having a viviparous mode of reproduction, although relationships within the family were generally poorly resolved. Several putative synapomorphies were found for the Gyrodactylidae, including viviparity and protogyny, a bulbous and armed MCO, absence of a vitellarium, and presence of a knob‐like deep anchor root (Fig. 3e). Ultrametric analyses suggested that the initial divergence of the clade of the gyrodactylid‐like monogenoids and Udonellidae occurred about 335 mya (based on the 18S rDNA fragment) and about 400 mya (based on the MT‐CO2 gene fragment). Using the 18S rDNA fragment and three calibration points, ultrametric analyses indicated that the Gyrodactylidae and Oogyrodactylidae diverged at approximately 278 mya, with initial diversification within the Gyrodactylidae (about 211 mya) occurring earlier than that of the Oogyrodactylidae (about 133 mya), the latter coinciding with the breakup of Gondwana and the initial diversification of the armoured catfishes (Loricariidae). Finally, diagnoses were provided for the Gyrodactylidae and Oogyrodactylidae along with a list of genera assigned to each family.

Neotropical sisterhood: new species of Gyrodactylus von Nordmann, 1832 (Platyhelminthes: Monogenea) infecting Rhamdia guatemalensis and Rhamdia laticauda (Siluriformes: Heptapteridae) in Mexico

“…The Amazon basin is one of the most diverse biomes for fish and parasite species in the world (Luque & Poulin, 2007; Nelson et al , 2016), and a place where evolutionary novelties/oddities occurred in the Monogenea. For instance, continental waters in Brazil are the only place where oviparous gyrodactylids have been recorded, with 23 species described from armoured (Loricariidae) and long-whiskered (Pimelodidae) catfishes; and it has recently been suggested that Oogyrodactylidae diversified following the Gondwana breakup and the separation of Africa and South America (Boeger et al , 2020). Also, the speciose family Dactylogyridae, which primarily includes gill-infecting species and has undergone a marked evolutionary radiation in Africa (e.g.…”

A new species of Phanerothecium (Monogenea, Oogyrodactylidae), in Hypostomus regani (Loricariidae) from southeast Brazil

“…Subsequently, Boeger & Kritsky (1993) consider Oogyrodactylidae synonymy of Gyrodactylidae due to the absence of synapomorphic features, thus uniting oviparous and viviparous species. Recently, through the use molecular data of 18S rDNA and COII (cytochrome oxidase II -mtDNA) Oogyrodactylidae (oviparous species) was reconsidered valid, separating this from species of Gyrodactylidae (viviparous species), thus both families were considered monophyletic and sister-groups (Boeger et al 2021).…”

“…Phanerothecium Kritsky & Thatcher, 1977 was considered monophyletic (Boeger et al 2021) and contains six species. In Brazil species of Phanerothecium were described only in Hypostomus Lacépède, 1803 hosts (Kritsky & Boeger 1991, Boeger, Kritsky & Belmont-Jégu 1994, Kritsky, Vianna & Boeger 2007.…”

“…Loricariidae Rafinesque, 1815 is one of the families included in this order and the second richest with 1192 valid species (Fricke et al 2021). Loricariids usually harbor oogyrodactylids (Harris 1983, Boeger et al 2021, although they can also concomitantly harbor species of gyrodactylids (Vianna & Boeger 2019).…”

Neuromuscular organization and haptoral armament of Polyclithrum ponticum (Monogenea: Gyrodactylidae)

“…Gyrodactylidae van Beneden et Hesse, 1832 is one of the most species-rich groups of monopisthocotylid monogeneans, common in all oceans and freshwater ecosystems of all continents infecting not only fish, like most monogeneans, but also crustaceans, amphibians and cephalopods (Boeger et al , 2003). Recently, this family has been restricted only to the viviparous gyrodactylids, with the oviparous species placed in a separate family Oogyrodactylidae Harris, 1983 (Boeger et al , 2021). The defining trait of reproductive biology within Gyrodactylidae sensu stricto is the phenomenon of hyperviviparity, whereby several daughter generations of embryos can gestate one inside another within the parental uterus (Bakke et al , 2007).…”