New perspectives on morphological and genetic variability of Corynosoma bullosum [Linstow, 1892] parasitizing southern elephant seals from the Antarctic Peninsula

SOTO, F. A.; RODRIGUEZ, S.; LEONARDI, M. S.; NEGRETE, J.; CREMONTE, F.

JOURNAL OF HELMINTHOLOGY

CAMBRIDGE UNIV PRESS

Lugar: Cambridge; Año: 2023

0022-149X

Previous descriptions of Corynosoma bullosum (Linstow, 1892) show that the specimens vary greatly for the proportions of the different body structures, measurements of females and males, number of rows of hooks, and egg measurements, among others. We describe this species from specimens found in the southern elephant seal feces, from King George Island. We also provide a molecular characterization, in addition to 5.8s and ITS existing sequences. We examined 41 elephant seals, and 30 adult acanthocephalans were found in 15 of them. The specimens were identified as belonging to the genus Corynosoma due to the tubular body with an inflated anterior part forming a thorny disk and the posterior part bearing somatic spines on the ventral surface, and genital spines surrounding the genital pore. The morphology of the individuals corresponded to C. bullosum: large size, marked sexual dimorphism, and proboscis with 16-18 rows of spines with 11-15 spines per row. The molecular profile of three specimens of C. bullosum was analyzed using 18S rDNA. We inferred phylogenetic relationships of the family Polymorphidae using maximum likelihood and Bayesian inference. We provided an updated morphological redescription for C. bullosum including electron microscopy photographs and molecular data. The 18S gene sequences showed low genetic variation and that C. bullosum is a sister to C. australe.