Linking phenotypic to genotypic metacestodes from of the Yucatan Peninsula.

is an endemic species of the Yucatan Peninsula. This species sustains the octopus' fishery in the region and is the only cephalopod cultured in Mexico. It is known that harbor a large richness and abundance of metacestodes that have been tentatively identified by light microscopy alone. Since the larval stages of some orders of marine cestodes lack the taxonomic characteristics shown by the adult stages and on which cestode taxonomy is based, identification down to the species level is often unattainable. Hence, the goal of this study was to characterize the parasites, for the first time, at morphological and molecular levels. A total of 60 octopuses were collected from September to December 2017 from four fishery landing ports in Yucatán: Sisal, Progreso, Dzilam de Bravo, and Rio Lagartos (15 hosts per locality). Morphology of metacestodes was characterized by light and Scanning Electron Microscopy (SEM), while the genes 18S and 28S rDNA were sequenced for molecular characterization. Based on phenotypic characters and molecular data, seven taxa of metacestodes were identified, four of them belonging of order Trypanorhyncha: sp., , sp., sp. 1; and the three remaining taxa belonging to the order Onchoproteocephalidea: sp., sp., and sp. This work provides, for the first time, molecular support to the morphological characterization of metacestodes recorded in