Euglesa kolymensis Bespalaya, Aksenova & Bolotov, 2024

Bespalaya, Yulia V., Vinarski, Maxim V., Aksenova, Olga V., Babushkin, Evgeniy S., Gofarov, Mikhail Yu., Kondakov, Alexander V., Konopleva, Ekaterina S., Kropotin, Alexander V., Mabrouki, Youness, Ovchankova, Nadezda B., Palatov, Dmitry M., Sokolova, Svetlana E., Shevchenko, Alexander R., Travina, Oksana V., Taybi, Abdelkhaleq F., Soboleva, Alena A., Zubrii, Natalia A. & Bolotov, Ivan N., 2024, Phylogeny, taxonomy, and biogeography of the Sphaeriinae (Bivalvia: Sphaeriidae), Zoological Journal of the Linnean Society 201 (2), pp. 305-338 : 323-326

Euglesa kolymensis Bespalaya, Aksenova & Bolotov sp. nov.

( Fig. 11A )

Zoobank number: urn:lsid:zoobank.org:act:BDC94015-12D0-42CB-B21E-F7C950E94EFD .

Type series: The holotype is deposited in RMBH (accession number: MSph-787). The type series includes one holotype .

Type locality: Russia: Yakutia , Srednekolymsk , lake next to the oil depot, Kolyma River Basin , [67°27 ʹ 29″N 153°42 ʹ 22″E], 25. VI.2021, Sokolova & Zubrii leg.

Etymology: This species is named after the Kolyma River.

Description: Shell round-oval in shape, its length is 4.7 mm ( Fig.11A ). The beaks are rounded and slightly protruding, somewhat shifted to the posterior edge of the shell ( Fig.11A ). The cardinal tooth of the right valve slightly curved has a thickening at the ends, the posterior end is branched. The cardinal teeth of the left valve are straight parallel to each other ( Fig. 12C ). The inner cardinal tooth of the left valve is thickened.

Distribution: Eastern Siberia, Kolyma River Basin.

Comments: The 16S and 28S rRNA sequences of this species have no analogues in GenBank and form a clade sister to the E. globularis group ( Fig. 2 ). Considering that E. kolymensis was found in the Kolyma River Basin, we also analysed the original descriptions, and compared our material with the type specimens of some nominal species described from the same river basin: Euglesa czerskii (Starobogatov & Streletskaja, 1967) , Euglesa jacutica (Starobogatov & Streletskaja, 1967) , and Euglesa rotundicostata (Starobogatov & Streletskaja, 1967) (Supporting Information, Fig. S1A, L, M ). The original morphological descriptions and features of these type specimens do not correspond to those of our specimen from the Kolyma River. In addition, all the listed species were subsequently assigned to the genera Henslowiana , Cingulipisidium, and Cyclocalyx according to Korniushin (1996) that are clearly different from the E. globularis group (see Vinarski and Kantor 2016).

Differential diagnosis: The new species can be distinguished from its sister species E. globularis and E. khurbaensis by having a more developed regular ribbing on shell surface, and different shape of the cardinal teeth. Thus, the cardinal teeth of the left valve of the E. globularis are distinctly curved, whereas those of E. kolymensis are straight ( Fig. 11A ). The cardinal tooth of the right valve of the E. globularis and E. khurbaensis is noticeably curved, unlike that of E. kolymensis ( Fig. 11A ).

Molecular diagnosis: The new species also differs from its congeners by two fixed nucleotide substitutions in the 16S rRNA gene fragment (280 C, 291 A). The uncorrected rRNA 16S p-distance of the new species from other congeners is 3.4–8.9% and those based on 28S rRNA is 0.1–4.8 %. The nearest congener of E. kolymensis is E. khurbaensis with the mean uncorrected 16S rRNA p-distance of 4.1 ± 0.8% (± SD).

Figures

Figure 1.Spatial distributionofthe numberofavailable 16S rRNA sequences (A), and species richness of thesubfamily Sphaeriinae (B), in theworld.

Figure 2. The phylogeny of the subfamily Sphaeriinae recovered from ML analysis (W-IQ-TREE) and obtained for the complete dataset of mitochondrial and nuclear sequences (16S rRNA+28S rRNA). Black numbers near nodes are bootstrap support values (BS)/ Bayesian posterior probabilities (BPP). The new taxa are highlighted in red. Subgenera are marked by curly brackets.

Figure 11. New species of Sphaeriinae described in this paper: (A) holotype of Euglesa kolymensis (RMBH No. MSph-787, Russia, Yakutia); (B) holotype of E.kyrgyzyca (RMBH No. MSph-331, Kyrgyzstan); (C) holotype of E. moroccana (RMBH No.MSph-775, Morocco); (D) holotype of Odhneripisidium caucasus (RMBH No. MSph-296, Russia, Krasnodar Region); (E) paratype of O.caucasus (RMBH No. MSph- 327, Abkhazia).Photos: O.V. Aksenova.Scale bar:1 mm.

Figure 12. Morphology and anatomy of new Sphaeriinae species described in this paper (teeth morphology and shell pores, anatomy of gills and siphons): (A) holotype of E. kyrgyzyca (RMBH No. MSph-331, Kyrgyzstan); (B) paratype of E. kyrgyzyca (RMBH No.MSph-331, Kyrgyzstan); (C) holotype of E. kolymensis (RMBH No. MSph-787, Russia, Yakutia); (D) holotype of E. moroccana (RMBH No. MSph-775, Morocco); (E) paratype of Odhneripisidium сaucasus (RMBH No. MSph-327, Abkhazia).Photos: O.V. Aksenova. Scale bars:0.5 mm.