Conventus Pirogov & Starobogatov, 1974

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 : 331

Genus Conventus Pirogov & Starobogatov, 1974 stat. nov.

Type species: Pisidium conventus Clessin, 1877 .

Diagnosis: The shell is small (up to 3.3 mm in length), oval, or rounded. The beaks are rounded and slightly prominent, and somewhat offset to the posterior edge of the valves ( Figs 5C and 6C ). Pores are rare. Only one (exhalant) siphon is present ( Fig. 7C ). The outer demibranch is completely reduced.

Reproductive biology: The members of the genus are characterized as synchronous brooders (embryos are developing within a distinct brood sac).

Distribution: The range of the genus covers Europe, Southeastern Asia, and North America, including high-latitude (Arctic) regions ( Fig. 3F ).

Remarks: In our phylogenetic trees, the species Odhneripisidium ellisi , Odhneripisidium insigne Gabb, 1868 , O. conventus , and Odhneripisidium sp.1 form a well-maintained clade that was previously designated by Saito et al. (2022) as Neopisidium Odhner, 1921 ( Fig. 2 ; Supporting Information, Fig. S4 ). The type species of the genus Neopisidium is Pisidium torquatum Stelfox, 1918 ( Odhner 1921). However this species considered a synonym of P. moitessierianum ( Korniushin and Glaubrecht 2002, Graf and Cummings 2023, MolluscaBase 2023). According to our phylogenetic trees ( Fig. 2 ; Supporting Information, Fig. S4 ) and previous studies, O. moitessierianum grouped with O. tenuilineatum ( Schultheiss et al. 2008, Saito et al. 2022) or with O. stewarti , belonging to the genus Odhneripisidium ( Clewing et al. 2013) . In this case, the name Neopisidium cannot be applied to the clade containing O. ellisi , O. insigne , O. conventus , and Odhneripisidium sp. 1 , and, thus, we classified this genus as Conventus Pirogov & Starobogatov, 1974 .

Figures

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 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 4. Fossil-calibrated phylogeny of the Sphaeriinae calculated under a lognormal relaxed clock model and a Yule process speciation implemented in BEAST 1.10.4 and obtained for the complete dataset of mitochondrial and nuclear sequences (16S rRNA+28S rRNA). Bars indicate 95% HPD of the estimated divergence times between lineages (Mya). Red numbers above the nodes are mean ages (Mya). Black numbers under the nodes are Bayesian posterior probabilities (BPP). Stratigraphic chart according to the International Commission on Stratigraphy (2022) (URL: http://www.stratigraphy.org/ICSchart/ChronostratChart2022-02.pdf). The node pies indicate ancestral area reconstructions of the Sphaeriinae clades (probability of each area combination) in accordance with the generalized biogeographic model (combination of the S-DIVA+DEC+S-DEC models).

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.