ABSTRACT
The molecular characterization of the daniconematid dracunculoid Mexiconema cichlasomae Moravec, Vidal, and Salgado-Maldonado, 1992 through the sequencing of SSU rDNA from adult individuals is presented herein. Additionally, preliminary genetic relationships of this nematode are inferred from alignment of sequences generated previously for other dracunculoids. Maximum parsimony and maximum likelihood analyses recovered identical trees. As anticipated by previous taxonomic work, M. cichlasomae is putatively closely related to skrjabillanid dracunculoids represented by Molnaria intestinalis (Dogiel and Bychovsky, 1934) and Skrjabillanus scardinii Molnár, 1966 SSU rDNA sequences, but the relationships of this newly discovered clade to other dracunculoid clades remain unresolved.
Subject(s)
DNA, Ribosomal/chemistry , Dracunculoidea/classification , Animals , Cichlids/parasitology , Dracunculoidea/genetics , Fish Diseases/parasitology , Likelihood Functions , Mexico , Phylogeny , RNA, Ribosomal, 18S/genetics , Sequence Alignment/veterinary , Spirurida Infections/parasitology , Spirurida Infections/veterinaryABSTRACT
Megachona chamelensis n. gen., n. sp. is described from the intestinal cecae of blue striped chub Sectator ocyurus (Kyphosidae, Perciformes), from Chamela Bay, Mexico. Megachona n. gen. most closely resembles Beaninema Caspeta-Mandujano, Moravec, and Salgado-Maldonado, 2001; Fellicola Petter and Køie, 1993; and Rhabdochona Railliet, 1916. The main characters that distinguish the new genus from all other rhabdochonids include a longer than wide funnel-shaped prostom and cuticular longitudinal ridges of prostom forming anteriorly subterminal massive toothlike structures followed posteriorly by irregularly arranged smaller teeth. This finding brings the total number of genera of Rhabdochonidae of marine fish in Mexico to 2. The new species is characterized by having a smaller number of cuticular longitudinal ridges in the male prostom than in the female prostom, forming massive toothlike structures in its subterminal portion, followed by more minute teeth in the female than in the male, a slender tail end with a broad tip, the distal part of the left spicule with a lanceolate end, a straight right spicule without a dorsal barb, 1 pair of precloacal and 3 pairs of postcloacal papillae, and a smooth egg surface.
Subject(s)
Fish Diseases/parasitology , Intestinal Diseases, Parasitic/veterinary , Perciformes/parasitology , Spirurida Infections/veterinary , Spiruroidea/classification , Animals , Cecum/parasitology , Female , Intestinal Diseases, Parasitic/parasitology , Male , Mexico , Spirurida Infections/parasitology , Spiruroidea/anatomy & histologyABSTRACT
A phylogenetic analysis of 40 species of Rhabdochona Railliet, 1916, including all 21 valid species in the Americas, resulted in 1733 equally most parsimonious trees and indicates that Rhabdochona is arguably monophyletic. Species from the Americas do not form a monophyletic group, since each of the six clades of Rhabdochona includes species from the Americas and species from other continents. The synapomorphies defining each clade stem from the morphology of the left spicule. Teeth number was consistent in one clade only, suggesting that this character, while useful for taxonomic purposes, is not indicative of phylogeny. Species of Rhabdochona associated with certain host groups, such as salmonids, catostomids and goodeids, do not always form monophyletic assemblages, nor do species associated with smaller discrete areas, such as the Mesa Central of Mexico. This indicates widespread host-switching rather than co-speciation as the main phenomenon in the evolution of this group, at least in the species from the Americas. Phylogenetic patterns reveal an ancient origin for the group that probably pre-dates current continental configurations.
