Description of Acanthocephalus anguillae balkanicus subsp. n. (Acanthocephala: Echinorhynchidae) from Proteus anguinus Laurenti (Amphibia: Proteidae) and the cave ecomorph of Asellus aquaticus (Crustacea: Asellidae) in Slovenia

Abstract

Acanthocephalus balkanicus Batchvarov et Combes, 1974 was incompletely described from the northern crested newt, Triturus cristatus (Laurenti) (Amphibia: Salamandridae), a possible synonym of the Balkan crested newt, Triturus ivanbureschi Arntzen et Wielstra, from a pond in village of Pesnopoy, southern Bulgaria. We provide a full description of adult males and females of the same taxon from the olm, Proteus anguinus Laurenti (Amphibia: Proteidae), the only exclusively aquatic cave-dwelling vertebrate in Europe, captured in Postojna-Planina Cave System in Slovenia. Cystacanths were also collected from the cave ecomorph of Asellus aquaticus (Linnaeus) (Crustacea: Asellidae) in the same location. Molecular analysis of specimens from Slovenia revealed that they are genetically almost identical to those of Acanthocephalus anguillae (Müller, 1780), a common parasite of European freshwater fishes. We propose to recognise the morphological and host differences by describing A. balkanicus as a new subspecies of A. anguillae. Acanthocephalus anguillae balkanicus is rather small and cylindrical with cylindrical proboscis having 10 rows of 6 hooks with simple roots each, long neck, large balloon-shaped lemnisci, small spherical anterior testis, and 6 club-shaped cement glands in 3 pairs. SEM images reveal more morphological details and the X-ray scans of gallium cut hooks shows considerably higher levels of phosphorus and calcium in adult hooks than in cystacanth hooks, especially in basal areas. Sulfur levels were higher in the arch and basal area of cystacanth hooks than adult hooks. Considering that both definitive and intermediate hosts of the Slovenian population of this acanthocephalan are bound to cave life, it is possible that its entire life cycle is uniquely completed underground.

Unravelling the hidden biodiversity – the establishment of DNA barcodes of fish-parasitizing Acanthocephala Koehlreuther, 1771 in view of taxonomic misidentifications, intraspecific variability and possible cryptic species

“…Sequences of A. anguillae from Germany are found in two haplotypes, separated from the central haplotype by three and one mutation steps, respectively (mean p- distance 0.5%, Table 4). Eight mutation steps (1.8%) separate the central haplotype from a sequence from GenBank assigned to the recently described subspecies Acanthocephalus anguillae balkanicus (Amin et al ., 2019). Finally, a GenBank sequence of A. dirus is separated by seven mutation steps (mean genetic p -distance of 1.6%).…”

“…The clustering of A. dirus within the A. anguillae clade was already attributed to a probable misidentification by Amin et al . (2019). The isopod Asellus aquaticus (L.) was reported as the host of the latter specimen (García-Varela and Nadler, 2006) and, since the life cycle of these helminths is not completed yet in the intermediate host, the specimen probably was at larval stage which might have impeded correct morphological identification.…”

“…Another reason for misidentification might be due to morphological variation within A. anguillae sensu lato: the two lateral extensions were previously described as one of the most characteristic identification traits of the species (e.g. Meyer, 1933; Petrochenko, 1956), but they were not observed (or only rudimentary) in A. a. balkanicus , a recently described subspecies of A. anguillae parasitizing in Proteus anguinus Laurenti, 1768 (Amin et al ., 2019). Therefore, the specimen from the USA could represent an additional lineage of A. anguillae sensu lato which lacks the lateral extensions, too.…”

“…[MK612497–MK612545 (Reier et al ., 2019)], Acanthocephalus spp. [KP261016 (Wayland et al ., 2015), AM039836, AM039837, AM039864–AM039866 (Benesh et al ., 2006), DQ089718 (García-Varela and Nadler, 2006), MN416027–MN416030 (Amin et al ., 2019)] and Echinorhynchus spp. [KP261013, KP261014, KP261017–KP261019 (Wayland et al ., 2015), AY218095 (Giribet et al ., 2004), DQ089710 (García-Varela and Nadler, 2006)].…”

“…Median joining ( MJ ) haplotype networks (Bandelt et al ., 1999) were calculated for the species P. tereticollis , P. bosniacus , E. cinctulus , A. anguillae sensu lato (according to Amin et al ., 2019) and A. lucii using PopART 1.7 software (). For A. lucii , to allow inclusion of shorter GenBank sequences from Finland [AM039878, AM039880–AM039884 (Benesh et al ., 2006)], the alignment was trimmed to 428 bp.…”