The radiation of Thaparocleidus (Monogenoidea: Dactylogyridae: Ancylodiscoidinae): phylogenetic analyses and taxonomic implications inferred from ribosomal DNA sequences

Abstract

The monophyly of Thaparocleidus Jain 1952 and its phylogenetic relationship with Pseudancylodiscoides were assessed using the D1-D2 domains of the large-subunit ribosomal deoxyribonucleic acid sequences, and taxonomic implications were discussed concerning the relative taxonomic importance of the characters of the reproductive complex and those of the haptoral scleties for future genus erection and combination within the Ancylodiscoidinae. Thaparocleidus contained divergent genetic lineages and was not resolved as a monophyletic group. The first lineage was represented by two species found on Pangasium sutchi (Pangasidae), and the second one contained 12 species all from Silurus astus (Siluridae). Three clades were observed for species from S. astus, consistent with results of morphological analyses, indicating that 12 Thaparocleidus species could be divided into three groups by morphological examinations of the male copulatory organ (MCO). Pseudancylodiscoides spp. was more closely related to Thaparocleidus spp. from S. astus, and morphologically, it was found that shapes of MCOs of these species were the same type but different from that of Thaparocleidus spp. from P. sutchi. Therefore, based on results of molecular phylogenetic analyses and morphological examinations, we propose to abolish Pseudancylodiscoides and to erect a new genus to accommodate Thaparocleidus species from S. astus and Pseudancylodiscoides spp. It is also suggested to erect another new genus to accommodate two Thaparocleidus species from the P. sutchi, whose MCO shapes are different from other Thaparocleidus species.

Speciation inThaparocleidus(Monogenea: Dactylogyridae) Parasitizing Asian Pangasiid Catfishes

“…The morphology of the haptor is considered useful for parasite determination at the genus level, while the reproductive organ is more suitable for identification at the species level, probably because of its higher rate of change [27, 61, 62]. However, in some cases, identification is problematic at the generic as well as the specific level.…”

“…As mentioned above, Thaparocleidus is not monophyletic; that is, Thaparocleidus parasitizing Siluridae and Thaparocleidus parasitizing Pangasiidae comprise different clades. Therefore, Wu et al [27] proposed taxonomic revision of the species recently included in Thaparocleidus . Hence, T. siluri and T. vistulensis may be included as outgroup taxa.…”

“…Nonmonophyly of Thaparocleidus was shown by Wu et al [27]. To date, 43 Thaparocleidus species have been described from 18 species of Pangasiidae ([28] and references therein).…”

Study on species composition of parasite in striped catfish (Pangasianodon hypophthamus Sauvage, 1878) based on morphological and genetic characters

“…Tuy nhiên, tình hình dịch bệnh ở cá tra phức tạp do sự bùng phát bệnh ký sinh trùng (KST), một tác nhân gây bệnh phổ biến. Trên thế giới đã có nhiều nghiên cứu về thành phần loài KST cá tra dựa trên đặc điểm hình thái [10,11,12,13] và di truyền [14,15,16,17], còn ở Việt Nam chủ yếu chỉ dừng lại ở nghiên cứu hình thái [4,5,7]. Nghiên cứu này kết hợp nghiên cứu đặc điểm hình thái và di truyền để xác định thành phần loài ký sinh trùng và xác định vị trí phân loại một số loài ký sinh trùng ký sinh trên cá tra…”

Supplementary taxonomic description of Demidospermus pinirampi (Monogenoidea, Dactylogyridae), with a new host record and an expansion of its distribution range

“…This characteristic was also observed in the holotype examined (INPA 059), although it was not clear in the drawing from the original description (Kritsky et al 1987). Although the morphology of the vaginal atrium contributes little to the phylogenetic proposal for some dactylogyrids (Wu et al 2007), its proper characterization is useful for the discrimination of species, especially for closely related taxa (Wu et al 2007;Wu et al 2008;Aguiar et al 2011).…”