Diversity and phylogenetic insights of monogenean parasites infecting freshwater fishes in Iraq

Abstract

Objective: To document the diversity, host associations and phylogenetic relationships of monogenean parasites infecting freshwater fishes from the Al-Diwaniyah River (Iraq) using integrated morphological and 28S rRNA sequence data.

Methods: From 1 October 2023 to 1 October 2024, 720 fish (three dominant host species) were examined for monogeneans. Parasites were identified morphologically and representative specimens were sequenced for the D1–D3 domains of the 28S rRNA gene. PCR amplicons were Sanger-sequenced, trimmed and assembled into consensus sequences. Sequences were compared to GenBank by BLAST and included in maximum-likelihood (ML) phylogenetic analyses with 1,000 bootstrap replicates. Epidemiological indices (prevalence, mean intensity) were calculated per host.

Results: Specimens assigned to Dactylogyrus spp. and Cichlidogyrus spp. were recovered. Five nominal taxa were identified morphologically: Dactylogyrus baueri, D. minutus, D. formosus, D. holciki and Cichlidogyrus tilapiae; two of these represent new host records for Iraq. Thirteen high-quality 28S consensus sequences (GenBank PV738226–PV738238) were produced and submitted (mapping of accessions to isolates provided in Table 2). Iraqi isolates clustered with Indo-Asian reference sequences but formed distinct terminal branches in several clades; inter-specific pairwise divergence in the amplified fragment reached up to 5.6%, while intra-specific similarity exceeded 98% in most comparisons.

Conclusions: This is the first molecularly anchored record of these monogenean taxa from the Al-Diwaniyah River. The 28S data supply a baseline for regional taxonomy and epidemiology, and indicate local genetic structuring that warrants wider geographic and multilocus investigation for cryptic diversity and aquaculture risk assessment.