Redescription and first genetic characterisation of Procamallanus (Spirocamallanus) macaensis Vicente & Santos, 1972 (Nematoda: Camallanidae), including re-evaluation of the species of Procamallanus (Spirocamallanus) from marine fishes off Brazil

Abstract

Newly collected specimens of Procamallanus (Spirocamallanus) macaensis Vicente & Santos, 1972 from the intestine of Paralonchurus brasiliensis (Steindachner), off Rio de Janeiro, Brazil, are redescribed and genetically characterised. Additionally, all congeners deposited in the Coleção Helmintológica do Instituto Oswaldo Cruz (CHIOC) parasitic in marine fishes of the South Atlantic, including types of P. (S.) macaensis, were re-evaluated. The following features are described for the first time in P. (S.) macaensis: morphology and arrangement of cephalic structures, shape of deirids and location of phasmids. The position of the excretory pore, the number and arrangement of caudal papillae in males, the structure of the spicules and of tail end in both males and females are rectified. Most specimens deposited in the CHIOC identified as P. (S.) pereirai Annereaux, 1946 were transferred to P. (S.) macaensis and others were designated as Procamallanus (S.) sp. Procamallanus (S.) cruzi Guimarães, Cristófaro & Rodrigues, 1976 is considered a species inquirenda due to its poor description and the lack of match of its original description with the type-material re-examined. Moreover, several taxonomic problems were noted after observations of the specimens (mostly poorly preserved), including inadequate morphological reports as well as misidentifications. Phylogenies inferred using sequences of the SSU rDNA from camallanids (Nematoda: Camallanidae) mostly generated weakly supported clades; however, Camallanus Railliet & Henry, 1915 and Procamallanus Baylis, 1923 do not seem to be monophyletic. Based on the present results and the lack of molecular data, it would be pertinent to adopt the widely-used classification for the subgenera of Procamallanus.

Incipient genetic divergence or cryptic speciation? Procamallanus (Nematoda) in freshwater fishes (Astyanax)

“…Also, such study would contribute to generate additional empirical data to resolve the problematic related to the subgeneric status of the species included in the genus Procamallanus . Several authors have provided molecular data demonstrating that the subdivision of the genus into several subgenera based on the structure of the buccal capsule should be abandoned (Černotíková et al, 2011; Sardella et al 2017; Ailán‐Choke et al, 2019). We took a conservative position and decided to still use the traditional classification, as Procamallanus ( Spirocamallanus ) neocaballeroi .…”

An integrative approach assesses the intraspecific variations ofProcamallanus(Spirocamallanus)inopinatus, a common parasite in Neotropical freshwater fishes, and the phylogenetic patterns of Camallanidae

“…However, to confirm this assertion, specimens with the whole buccal capsule occupied by spiral ridges need to be genetically characterized and compared to the present data. It should be mentioned that, based on genetic evidence, the morphology of buccal capsule seems to bear some degree of artificiality in the systematics of genera and subgenera of Camallanidae (Wijová et al ., 2006; Sardella et al ., 2017; Ailán-Choke et al ., 2019), which may be also true at the species level, as suggested here.…”

“…Indeed, the phylogenetic aspects of Camallanidae are far from being elucidated due to the lack of genetic data, which is aggravated by the fact that the morphology-based systematics of the family is problematic and taxonomic labelling of some sequences available in genetic databases (e.g. GenBank) seems to be inaccurate (Černotíková et al ., 2011; Sardella et al ., 2017; Ailán-Choke et al ., 2019).…”

Novel information on the morphology, phylogeny and distribution of camallanid nematodes from marine and freshwater hosts in South Africa, including the description of Camallanus sodwanaensis n. sp.

“…and Camallanus spp., albeit without support. Later, Sardella et al (2017) redescribed S. macaensis Vicente et Santos, 1972 and included this species in the phylogenetic analyses of the Camallanidae based on 18S rDNA gene data. Similarly, in studies of Černotíková et al (2011), Procamallanus , Spirocamallanus and Camallanus formed weakly supported clades.…”