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Complex species structure of Lecithaster salmonis (Digenea: Lecithasteridae), a fish parasite in the Arctic and Pacific Northwest

Published online by Cambridge University Press:  13 January 2025

D. Krupenko*
Affiliation:
Laboratory of Parasitic Worms and Protists, Zoological Institute of the Russian Academy of Sciences, Universitetskaya nab. 1, 199034, Saint Petersburg, Russia Department of Invertebrate Zoology, Saint Petersburg University, Universitetskaya nab. 7–9, 199034, Saint Petersburg, Russia
A. Gonchar
Affiliation:
Laboratory of Parasitic Worms and Protists, Zoological Institute of the Russian Academy of Sciences, Universitetskaya nab. 1, 199034, Saint Petersburg, Russia Department of Invertebrate Zoology, Saint Petersburg University, Universitetskaya nab. 7–9, 199034, Saint Petersburg, Russia
V. Krapivin
Affiliation:
Department of Invertebrate Zoology, Saint Petersburg University, Universitetskaya nab. 7–9, 199034, Saint Petersburg, Russia Center of Parasitology of A.N. Severtsov Institute of Ecology and Evolution of the Russian Academy of Sciences, Leninskii Prospect 33, 117071, Moscow, Russia
G. Kremnev
Affiliation:
Laboratory of Parasitic Worms and Protists, Zoological Institute of the Russian Academy of Sciences, Universitetskaya nab. 1, 199034, Saint Petersburg, Russia
O. Skobkina
Affiliation:
Laboratory of Parasitic Worms and Protists, Zoological Institute of the Russian Academy of Sciences, Universitetskaya nab. 1, 199034, Saint Petersburg, Russia
B. Efeykin
Affiliation:
Center of Parasitology of A.N. Severtsov Institute of Ecology and Evolution of the Russian Academy of Sciences, Leninskii Prospect 33, 117071, Moscow, Russia
*
Corresponding author: D. Krupenko; Email: krupenko.d@gmail.com

Abstract

Studying complexes of cryptic or pseudocryptic species opens new horizons for the understanding of speciation processes, an important yet vague issue for the digeneans. We investigated a hemiuroidean trematode Lecithaster salmonis across a wide geographic range including the northern European seas (White, Barents, and Pechora), East Siberian Sea, and the Pacific Northwest (Sea of Okhotsk and Sea of Japan). The goals were to explore the genetic diversity within L. salmonis through mitochondrial (cox1 and nad5 genes) and ribosomal (ITS1, ITS2, 28S rDNA) marker sequences, to study morphometry of maritae, and to revise the life cycle data. Mitochondrial markers showed that L. salmonis is likely divided into six lineages (referred to as operational taxonomic units, OTUs), which often occur in sympatry, sometimes in a single host specimen. Variation in rDNA was not consistent with that in the mitochondrial markers. Morphometric analysis of maritae was performed for four out of six OTUs; it showed that some OTUs had significant differences from the others, but some did not. The effect of host species on the morphometric characteristics cannot be excluded. Intramolluscan stages were identified for two OTUs; they differed clearly by the structure of cercariae and also by the species of the first intermediate host. The case of L. salmonis is instructive in how different criteria for species delimitation can contradict each other. We regard this as a sign of recent or ongoing speciation and suggest using the name Lecithaster cf. salmonis. The most promising criteria to differentiate genetic lineages within L. cf. salmonis are first intermediate hosts and morphological characteristics of the cercariae: shape of the delivery tube and caudal cyst, and length of the filamentous appendage.

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Type
Research Paper
Copyright
© The Author(s), 2025. Published by Cambridge University Press

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