Euglesa Jenyns, 1832

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 : 322-323

Genus Euglesa Jenyns, 1832

Type species: Tellina pusilla W. Turton, 1819 (non Tellina pusilla Lamarck, 1806 ) = Euglesa personata (Malm, 1855) .

Diagnosis: This genus comprises not less than 35 valid species ( Table 1 ). The shell is small sized (min–max shell length 2.5– 6.0 mm). The beaks are shifted to the posterior edge or located near the middle of the shell ( Figs 5A , 6A ). Similar to Pisidium , only the exhalant siphon and a branchial mantle opening are present in the species of this genus. The branchial siphon is reduced. The outer demibranch (with certain reduction) and inner demibranch usually present ( Fig. 7A ). In addition, some species are characterized by a very small outer demibranch, as well as its complete reduction. For example, both states of this character were observed in the North American species Euglesa compressa ( Korniushin and Glaubrecht 2002) .

Reproductive biology: This genus is characterized as synchronous brooders (embryos are developing within a distinct brood sac).

Distribution: The genus has wide (subcosmopolitan) distribution, covering Eurasia, Africa, North America, and Australia, including high-altitude and high-latitude regions ( Fig. 3B ).

Figures

Figure 3. Maps of approximate geographic distribution of six genera of the Sphaeriinae in the world based on available 16S rRNA sequences: (A) Sphaerium; (B) Euglesa; (C) Pisidium s.s.; (D) Odhneripisiduim; (E) Hindupisidium; (F) Conventus.

Figure 5. Representatives of valid genera in the subfamily Sphaeriinae:(A) Euglesa casertana, Russia, Yamalo-Nenets Autonomus Okrug, Gydan Peninsula; (B) Hindupisidium nevillianum (Myanmar, Inle Lake); (C) Conventus conventus, Russia (Arkhangelsk Region, Novaya Zemlya); (D) Pisidium amnicum (Russia, Nenets Autonomus Okrug, Vashutkiny Lakes); (E) Sphaerium corneum (Russia, Arkhangelsk Region, Bolshoy Solovetsky Island); (F) Sphaerium lacustre (Russia, Irkutsk Region, Angara River). Photos:O.V.Aksenova. Scale bar: 1 mm.

Figure 6. Teeth morphology and shell pores of representatives of the genera in the subfamily Sphaeriinae: (A) Euglesa casertana (Russia, Yamalo-Nenets Autonomus Okrug, Yamal Peninsula); (B) Hindupisidium nevillianum (Myanmar, Inle Lake); (C) Conventus conventus (Russia, Arkhangelsk Region, Novaya Zemlya); (D) Pisidium amnicum (Russia, Nenets Autonomus Okrug, Vashutkiny Lakes); (E) Sphaerium corneum (Russia, Arkhangelsk Region, Bolshoy Solovetsky Island).Photos: O.V. Aksenova.Scale bars: teeth—0.5 mm; pores—20 µm. The left-hand, central column—right and left valves, respectively; the right-hand column—pores.

Figure 7. Anatomy of siphons and gills of representatives of the genera in the subfamily Sphaeriinae: (A) Euglesa casertana (Russia, Vaigach Island); (B) siphon of Hindupisidium nevillianum (Myanmar, Inle Lake); (C) siphon of Conventus conventus (Russia, Arkhangelsk Region, Novaya Zemlya); (D) siphon of Pisidium amnicum (Russia, Tyumen Region); (E) siphon of Sphaerium corneum (Russia, Arkhangelsk Region, Bolshoy Solovetsky Island); (F) siphon of Sphaerium lacustre (Russia, Irkutsk Region, Angara River); (G) gill with embryos of E. casertana (Russia, Vaigach Island); (H) gills with embryos of P.amnicum (Russia, Nenets Autonomus Okrug, Vashutkiny Lakes); (I) gills with embryos of S. lacustre (Russia, Irkutsk Region, Angara River). Photos:O.V.Aksenova. Scale bars: 0.5 mm.