Morphological and Molecular Analyses of Aponurus laguncula Looss, 1907 (Digenea: Lecithasteridae) Parasitic in Atlantic Spadefish Chaetodipterus faber (Broussonet, 1782) (Acanthuriformes: Ephippidae) from Brazilian Coastal Zone

Objectives: An integrative taxonomic description of Aponurus laguncula (Lecithasteridae), a digenean parasitic species of Chaetodipterus faber (Acanthuriformes) from Brazilian Southeast, is provided. Morphological techniques, as whole mounted slides, histology and scanning electron microscopy, and molecular analyses supported that integrative description.

Methods: Fifteen digenean specimens were stained in hydrochloric carmine and mounted on permanent slides. Two specimens were stained in hematoxylin and eosin following histological routine processing. Four parasites were dehydrated through a graded ethanol series, critical point dried with carbon dioxide and coated with gold to scanning electron microscopy analysis. Sequence of the large ribosomal subunit (28S rDNA) gene was generated and used to construct a phylogeny based on maximum likelihood and Bayesian inference analyses.

Results: Morphological description and morphometric data obtained in present study were in accordance with previous studies of the species. Use of another morphological techniques, as scanning electron microscopy and histology, corroborated the observed features of whole mounted slides. Also, they provided a better observation of previous reported characteristics and new features reporting, such as an elongated hermaphroditic duct, a smooth tegument and cells that compose the prostatic gland. The molecular sequence obtained in the present study formed a robust clade with available sequences of species of Aponurus.

Conclusions: The integrative taxonomic approach successfully combined morphological observations, including both previously reported features and new descriptions from histological and electron microscopy analyses, with molecular data to identify these specimens as A. laguncula. Moreover, the detailed characterization of structures, such as the gonads in A. laguncula, that would be challenging to analyze using a single technique, was possible. Further molecular studies with less conserved genetic markers should be conducted to understand phylogenetic relationships between Aponurus species.