Genetic and morphological variation in Pennella sp. (Copepoda: Siphonostomatoida) collected from Pacific saury, Cololabis saira

摘要: In this paper, we describe three morphotypes of large parasitic copepods identified as Pennella Oken, 1815 (Siphonostomatoida, Pennellidae), which are found on the commercial fish Pacific saury Cololabis saira (Brevoort, 1856) (Beloniformes, Scomberesocidae). Of (Pennella sp. (PSP), parasite A (PA), and indeterminate individuals (IDI)), PSP had feather-like abdominal brushes egg sacs were characters typical Pennella, PA lacked sacs, IDI few but no sacs. Nucleotide sequence differences mitochondrial cytochrome oxidase subunit I (COI) nuclear ribosomal internal transcribed spacer 1 (ITS1) regions between types small comparable with within a type, indicating that conspecific. Mean body length was significantly larger than those IDI, suggesting immature morphs or ceased development prior to maturation.