Abstract
A new myzostome species, described here as Myzostoma khanhkhoaensis sp. nov., was collected in Nhatrang Bay, central Vietnam, during investigation of symbionts associated with crinoids. Myzostoma khanhkhoaensis sp. nov. was found only on Clarkcomanthus albinotus Rowe, Hoggett, Birtles & Vail, 1986 in dense groups of up to 25 specimens. This species closely matches the colour pattern of the host by adjusting its cryptic colour and infects the distal part of crinoid arms, causing them to become curved. This is the first record of myzostomes that induce deformation of skeletal elements without the formation of galls or cysts. Morphologically M. khanhkhoaensis sp. nov. is close to M. cuniculus and M. pseudocuniculus but clearly differs from both of them by the shape of caudal blade and chaetae. Molecular-genetics analysis based on CO1, 16S and 18S DNA placed M. khanhkhoaensis sp. nov. in a clade including M. cuniculus, M. pseudocuniculus and M. indocuniculus.
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