Coccidia and other apicomplexans in bivalve molluscs
Document Type
Article
Publication Title
Diseases of Bivalves: Historical and Current Perspectives
Publication Date
1-1-2024
Abstract
Coccidia, belonging to the phylum Apicomplexa, constitute a diverse group of unicellular parasites. They are obligate intracellular parasites of both vertebrate and invertebrate hosts. However, their interactions with invertebrate hosts, specifically marine invertebrate hosts, remain poorly understood. In bivalve hosts, coccidia often infect kidney tissues, but can also infect other tissues such as the heart auricle, adductor muscle, and reproductive organs. In most coccidia infections, the host kidney epithelial cells undergo hypertrophy, and kidney tubules become filled with parasites and debris, potentially leading to impaired kidney function and damage under heavy infections. The majority of the named bivalve-infecting coccidia species have been identified from clam and scallop hosts. The earliest documented coccidian species in bivalves, Pseudoklossia (Hyaklossia) pelseneeri, was identified in Tellina sp. and Donax sp. clams from France in 1897. Shortly after, in 1917, the first scallop-infecting coccidia, Pseudoklossia pectinis, was documented in the kidneys of European king scallops, Pecten maximus. Since these initial discoveries, nine coccidia have been named from bivalve hosts; however, many more have been reported but not fully described. Advancements in genomics and transcriptomics hold promise in redefining the Eucoccidiorida and Apicomplexa as a whole, elucidating the taxonomic relationships, and overcoming the limitations of histological methods. A recent study proposed the establishment of a new subgroup within the Apicomplexa, the class Marosporida, based on retained plastid genomes across various species. This proposed class would include the previously described coccidia species P. pectinis, P. (=Merocystis) tellinovum, Margolisiella islandica and Merocystis kathae, along with the newly described Bay Scallop Marosporida (BSM). This novel group would be considered a sister clade to both Coccidia and Hematozoa.
First Page
227
Last Page
250
DOI
10.1016/B978-0-12-820339-2.00018-8
Recommended Citation
Scro, A. (2024). Coccidia and other apicomplexans in bivalve molluscs. Diseases of Bivalves: Historical and Current Perspectives, 227-250. https://doi.org/10.1016/B978-0-12-820339-2.00018-8
ISBN
[9780128203392, 9780128203439]
