On Cavisoma magnum (Acanthocephala: Cavisomidae) in the Persian Gulf Near Basra, with New Morphological Observations and a Molecular Profile

Aims: To supplement the description of Cavisoma magnum (Southwell, 1927) Van Cleave, 1931 which was originally described from a sea bass, Serranus sp. Cuvier and spotted surgeonfish, Ctenochaetus strigosus (Bennett) (Perciformes) off Sri Lanka before its more recent redescription from milkfish in the Philippines in 1995. We also describe its molecular profile for the first time. History: We recently provided a comprehensive revision of this species including SEM images, new systematic observations, metal analysis of hooks, and histopathology in a mullet intestinal tissue for the first time. Adjustments and corrections to previous descriptive accounts were made. The results of our x-ray analysis displayed high levels of sulfur especially at the tips and edges of the proboscis hooks. Study Design: We examined new specimens from Persian Gulf material and produced new SEM and light microscopy images that were not previously known. In addition, we provided the molecular characterization of the nuclear gene (18S) of ribosomal subunit. To elucidate the phylogenetic relationships of the C. magnum and the other genera in the family Cavisomidae, phylogenetic analyses were performed using maximum likelihood (ML) and Bayesian inference (BI). Place and Duration of Study: The study took a few months in the Persian Gulf in 2023 but the molecular analysis was conducted in India for a longer period. Methodology: Routine methods of processing and examination of specimens by light microscopy and SEM imaging were followed. PCR reactions were carried out and the 18S sequence data phylogenetic trees were constructed using maximum likelihood (ML) with MEGA v11. The genetic distances (uncorrected p-distance) were calculated with MEGA v11 Results and Conclusions: New images of various morphological structures and of hosts and recovered worms add more perspective towards the description of this worm and the phylogenetic analysis showed that Cavisomidae has a sister relationship with Rhadinorhynchidae + Gymnorhynchidae. Importance: This work redescribes the taxonomy of Cavisoma magnum and provides new images as well as its molecular analysis for the first time.