Redescription and molecular analysis of Corynosoma pseudohamanni Zdzitowiecki, 1984 (Acanthocephala: Polymorphidae) juveniles from Notothenia coriiceps Richardson in the water area of Argentine Islands, West Antarctica.

Corynosoma pseudohamanni Zdzitowiecki, 1984 (Polymorphidae) was described from the intestinal tract of 5 species of seals including the type and main host, the Weddell seal Leptonycotes weddellii (Lesson) in the South Shetlands, West Antarctica. Notothenia coriiceps was the primary paratenic host of 14 fish hosts reported in the original description. We describe excysted juveniles from the body cavity of the major paratenic host, Notothenia coriiceps Richardson collected off Galindez Island, Argentine Islands, West Antarctica for the first time. The original description was not "based on material collected from the final hosts (seals) and paratenic hosts (fish)" as stated since no description of juveniles was given then. Our excysted juveniles were generally smaller than reported adults and many of the other measurements were comparable to those of the adults in the original description. We added many of the incomplete measurements of adults in the original description especially those of the underdeveloped reproductive structures. We compared our morphometric description with the only other one available for juveniles collected from three paratenic fish hosts from Prince Gustav Channel, Antarctica. We have added informative optical microscopy images and SEM images of internal and external structures, previously missed in the original description. Energy Dispersive X-ray analysis revealed the highest levels of calcium in all hooks and hook roots compared to sulfur and phosphorus. We also provide a molecular characterization of the species for the first time. Newly generated sequences of the mitochondrial cytochrome c oxidase subunit 1 (mtcox1) gene from isolates of C. pseudohamanni cystacanths were compared with sequences of other acanthocephalans available in GenBank. Phylogenetic analyses based on maximum likelihood (ML) and Bayesian inference (BI) methods of the cox1 dataset placed all the species of Corynosoma in a single clade, with strong support. The mt cox1 sequences of C. pseudohamanni formed a strongly supported individual clade with the published sequences of Corynosoma nortmeri and Corynosoma magdaleni from the North Sea, Germany. We have determined the genetic diversity of C. pseudohamanni and compare it with other Corynosoma species haplotype diversity and distribution.