Salmincola markewitschi or S. carpionis (Copepoda: Lernaeopodidae)? A requirement for taxonomic revision due to their high morphological variations

Abstract

Salmincola markewitschi Shedko et Shedko, 2002 (Copepoda: Lernaeopodidae) is an ectoparasitic copepod mainly infecting the buccal cavities of white-spotted charr Salvelinus leucomaenis (Pallas) (Salmonidae). This species has only been recorded from Northeast Asia, where a morphologically similar congener Salmincola carpionis (Krøyer, 1837) is also distributed, using the same host species. These copepods are hard to distinguish from each other because of their similarities. We thus examined the newly collected specimens morphologically and genetically from five populations of white-spotted charr in Japan. Most of the specimens were morphologically consistent with S. markewitschi but showed great variations in the numbers of spines on the exopods of the antennae, shape of the maxilliped myxal palps, and the bulla diameter. Consequently, some specimens shared characteristics with S. carpionis. In addition to the mophological continuities, genetic analyses of 28S rDNA and COI mitochondrial DNA confirmed that all specimens belong to a single species. Further taxonomic revisions are required to draw conclusions of whether S. markewitschi is a valid species different from S. carpionis, by collecting samples from across their wide distributional ranges, such as Europe, North America, and Northeast Asia. A key to identification of species of Salmincola Wilson, 1915 occurring in Japan is also provided.

The first report of co-infection with Sphaerirostris picae and Ascaridia galli in the Oriental magpie (Pica serica) in Beijing, China

“…In the past, traditional methods of identifying and classifying parasites relied heavily on morphological features, host speci city and parasite location, which were highly dependent on sample integrity and the experience of the identi er [23,24]. In this species identi cation process, we used both stereoscopic microscope and scanning electron microscope and molecular biology methods to better identify the species.…”

Disentangling the causality between parasite infections and poor host conditions in the wild population

“…These copepods were identified as S. cf. markewitschi based on morphological observations and molecular analysis in a previous study (Figure 1; Hasegawa et al, 2022b).…”

Molecular identification and environmental DNA detection of gill lice ectoparasites associated with Brook Trout declines

“…High levels of morphological and genetic variation have been documented in copepods (e.g., Goedknegt et al 2018;Hasegawa et al 2022b), indicating that local reference sequences are necessary to confirm species identity and account for genetic variation in our eDNA assay design. However, aside from 28S ribosomal RNA (which is relatively conserved among species), only a few sequences are currently available to assess genetic variation in S. edwardsii: just two unique mitochondrial cytochrome c oxidase I (COI) gene haplotypes from Wilmurt Lake, New York (Table S1 available in the Supplementary Information in the online version of this article).…”

“…Few parasitic copepods have been genetically characterized, and many have highly modified, reduced, and/or cryptic morphology, which can complicate efforts to identify and differentiate closely related species (Goedknegt et al 2018;Hasegawa et al 2022b). Geographic locality is also of little taxonomic value given that many species have pancontinental distributions and infected host fish introductions are likely common and widespread (e.g., Ruiz et al 2017;Boone and Quinlan 2019;Mullin and Reyda 2020;Lepak et al 2022).…”

“…Geographic locality is also of little taxonomic value given that many species have pancontinental distributions and infected host fish introductions are likely common and widespread (e.g., Ruiz et al 2017;Boone and Quinlan 2019;Mullin and Reyda 2020;Lepak et al 2022). Examples of morphologically similar Salmincola species occurring in sympatry (Ruiz et al 2017), including some that utilize the same host fish species (Hasegawa et al 2022b), have made Salmincola species particularly challenging to identify. In these situations, molecular-based approaches that include evaluations of genetic diversity and phylogeny can be useful for species confirmation and diagnosing cryptic taxa (Katz et al 2015), including parasitic copepods (Ruiz et al 2017;Goedknegt et al 2018;Hasegawa et al 2022aHasegawa et al , 2022b.…”