HOST SWITCHING IN DICYEMIDS (PHYLUM DICYEMIDA)

• Published in: The Journal of parasitology Vol. 110; no. 2; p. 159
• Main Authors: Nakajima, Hiroaki, Fukui, Ayako, Suzuki, Kazutaka, Tirta, R Yusrifar Kharisma, Furuya, Hidetaka
• Format: Journal Article
• Language: English
• Published: United States 16.04.2024
• Subjects: Animals; Decapodiformes - parasitology; Invertebrates - anatomy & histology; Invertebrates - genetics; Octopodiformes; Parasites; Phylogeny; Co-speciation; Endosymbionts; Renal organs; Intra-host speciation; Phylogeny; Cuttlefishes; Octopuses; Speciation; Cephalopods; Host switch
• ISSN: 1937-2345
• DOI: 10.1645/23-52

Dicyemids (phylum Dicyemida) are the most common and most characteristic endosymbionts in the renal sacs of benthic cephalopod molluscs: octopuses and cuttlefishes. Typically, 2 or 3 dicyemid species are found in a single specimen of the host, and most dicyemids have high host specificity. Host-specific parasites are restricted to a limited range of host species by ecological barriers that impede dispersal and successful establishment; therefore, phylogenies of interacting groups are often congruent due to repeated co-speciation. Most frequently, however, host and parasite phylogenies are not congruent, which can be explained by processes such as host switching and other macro-evolutionary events. Here, the history of dicyemids and their host cephalopod associations were studied by comparing their phylogenies. Dicyemid species were collected from 8 decapodiform species and 12 octopodiform species in Japanese waters. Using whole mitochondrial cytochrome c oxidase subunit 1 (COI) sequences, a phylogeny of 37 dicyemid species, including 4 genera representing the family Dicyemidae, was reconstructed. Phylogenetic trees derived from analyses of COI genes consistently suggested that dicyemid species should be separated into 3 major clades and that the most common genera, Dicyema and Dicyemennea, are not monophyletic. Thus, morphological classification does not reflect the phylogenetic relationships of these 2 genera. Divergence (speciation) of dicyemid species seems to have occurred within a single host species. Possible host-switching events may have occurred between the Octopodiformes and Decapodiformes or within the Octopodiformes or the Decapodiformes. Therefore, the mechanism of dicyemid speciation may be a mixture of host switching and intra-host speciation. This is the first study in which the process of dicyemid diversification involving cephalopod hosts has been evaluated with a large number of dicyemid species and genera.