Abstract
BackgroundMicrocotyle erythrini van Beneden & Hesse, 1863 (Platyhelminthes: Monogenea) and other closely related species of the genus are often considered as cryptic. Records in hosts other than the type-host with no species confirmation by molecular analyses have contributed to this situation.MethodsGill parasites of five sparid fishes, Boops boops (L.), Pagellus erythrinus (L.), P. acarne (Risso), Dentex dentex (L.) and Pagrus pagrus (L.), from the Western Mediterranean off Spain were collected. Specimens of Microcotyle spp. were characterised both molecularly and morphologically. Partial fragments (domains D1-D3) of the 28S rRNA gene and the cytochrome c oxidase subunit 1 (cox1) gene were amplified and used for molecular identification and phylogenetic reconstruction. Principal components analysis was used to look for patterns of morphological separation.ResultsMolecular analyses confirmed the identity of three species: M. erythrini ex P. erythrinus and Pa. pagrus; M. isyebi Bouguerche, Gey, Justine & Tazerouti, 2019 ex B. boops; and a species new to science described herein, M. whittingtoni n. sp. ex D. dentex. The specific morphological traits and confirmed hosts (P. erythrinus and Pa. pagrus) are delimited here in order to avoid misidentifications of M. erythrini (sensu stricto). Microcotyle erythrini (s.s.) is mostly differentiated by the shape of its haptor, which is also longer than in the other congeners. New morphological and molecular data are provided for M. isyebi from the Spanish Mediterranean enlarging the data on its geographical range. Microcotyle whittingtoni n. sp. is described from D. dentex and distinguished from the remaining currently recognised species of the genus by the number and robustness of the clamps.ConclusionsNew diagnostic morphological traits useful to differentiate Microcotyle spp. are suggested: (i) haptor dimensions including lobes; (ii) the thickness of the clamps; (iii) the size and shape of spines of the genital atrium; (iv) the extension of the posterior extremities of vitelline fields; and (v) the shape of egg filaments. The use of new morphological approaches may allow considering these species of Microcotyle as being pseudocryptic. The use of representative undamaged specimens that have been genetically confirmed as conspecific is considered crucial to avoid abnormally wide morphological ranges that prevent species differentiation.
Highlights
Microcotyle erythrini van Beneden & Hesse, 1863 (Platyhelminthes: Monogenea) and other closely related species of the genus are often considered as cryptic
Partial cox1 (434 nt) sequences were generated for a total of 12 isolates, i.e. 4 M. isyebi ex B. boops, 6 M. erythrini (4 ex Pa. pagrus and 2 ex P. erythrinus) and 2 M. whittingtoni n. sp. ex D. dentex
Phylogenetic analysis revealed that the newly sequenced isolates belonged to 3 species: M. erythrini ex P. erythrinus and Pa. pagrus; M. isyebi ex B. boops; and M. whittingtoni n. sp. ex D. dentex
Summary
Microcotyle erythrini van Beneden & Hesse, 1863 (Platyhelminthes: Monogenea) and other closely related species of the genus are often considered as cryptic. Many authors have recorded and described new specimens identified as M. erythrini in different sparid species, mostly in the Mediterranean Sea (see Table 1 in Bouguerche et al [3], for details on the records of M. erythrini) These publications sometimes offered morphological ranges based on a combination of measurements of specimens from different host species With the help of molecular tools (cox partial fragment), M. erythrini has been split into two species, each in a different sparid host off the Algerian coast: M. erythrini ex P. erythrinus and M. isyebi Bouguerche, Gey, Justine & Tazerouti, 2019 ex Boops boops (L.) [3] These authors included the most recent morphometric information on M. erythrini from the type-host P. erythrinus. Bouguerche et al [2, 3] suggested that morphological and molecular characterization of M. erythrini-like specimens infecting different sparid hosts would reveal higher parasite diversity
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