Karl Marx A. Quiazon 1,2 *, Mudjekeewis D. Santos 3 , Darrell D. Blatchley 4 , Roselyn D. Aguila 3,5 , and Tomoyoshi Yoshinaga 2 1 Freshwater Aquaculture Center and College of Fisheries, Central Luzon State University, Science City of Muñoz, Nueva Ecija 3120 Philippines 2 Department of Aquatic Bioscience, Graduate School of Agricultural and Life Sciences The University of Tokyo, Yayoi 1-1-1, Bunkyo-ku, Tokyo 113-8657 Japan 3 Genetic Fingerprinting Laboratory, National Fisheries Research and Development Institute 101 Mother Ignacia St., Quezon City 1103, Philippines 4 D’Bone Collector Museum Inc., Bucana Trading Boulevard Barangay 76-A, Davao City, Philippines 5 Texas A&M University at Galveston 200 Seawolf Parkway, Galveston, Texas, USA Molecular and Morphological Identifications of Anisakis Dujardin, 1845 (Nematoda: Anisakidae) from a Rare Deraniyagala’s Beaked Whale (Mesoplodon hotaula Deraniyagala, 1963) and Blainville’s Beaked Whale (Mesoplodon densirostris Blainville, 1817) Stranded Off Southern Philippines Keywords: Anisakis, ITS region, Mesoplodon hotaula, Mesoplodon densirostris, morphology, mtDNA COX2 gene, Western Pacific region Beaked whales are among the definitive host of the parasitic worm Anisakis Dujardin, 1845. In this study, molecular [using ribosomal internal transcribed spacer (ITS) region and mitochondrial DNA cytochrome c oxidase subunit 2 gene (mtDNA COX2)] and morphological (light microscopy and scanning electron microscopy) identifications of Anisakis from a rare Deraniyagala’s beaked whale Mesoplodon hotaula Deraniyagala, 1963 and Blainville’s beaked whale Mesoplodon densirostris Blainville, 1817 stranded in Davao Gulf, Southern Philippines are presented. Results conclusively revealed that the worm samples were A. ziphidarum, representing an additional geographical record for the species along the West Pacific region and a first record examined from the rare Deraniyagala’s beaked whale, representing a new host record for the species. Interestingly, both molecular and morphological data further revealed that the worms collected from Deraniyagala’s beaked whale consisted of two subgroups under the A. ziphidarum clade suggesting possible cryptic species, one of which is closely related to the Atlantic species while the other could be a local variant specific to the West Pacific. *Corresponding Author: karlmq@clsu.edu.ph 823 Philippine Journal of Science 150 (3): 823-835, June 2021 ISSN 0031 - 7683 Date Received: 18 May 2020