Malacological news from the Czech and Slovak Republics in 2021

This paper presents important faunistic records conducted in the Czech and Slovak Republics during 2021. In the Šumava Mts, South Bohemia, a hydrobiid snail of the genus Alzoniella was found. Monacha cantiana s. lato was genetically confirmed for the first time in the city of Bratislava, Slovakia. New sites of Cornu aspersum (Prague) and Tandonia kusceri (southern and central Slovakia) were confirmed. A new colony of the slug Limacus maculatus was found in SE Moravia. New records of several endangered species, e.g. Vertigo angustior , V. moulinsiana , Anisus septemgyratus , Gyraulus acronicus , G. rossmaessleri , Planorbis carinatus , Pisidium amnicum , P. globulare , P. moitessierianum , P. pseudosphaerium and P. tenuilineatum , are also presented. Location data are published with all


Introduction
Since the last comprehensive monograph on molluscs of the Czech and Slovak Republics has been published in 2013 (Horsák et al. 2013), we decided to publish malacological news from the territory of former Czechoslovakia annually in order to keep track of new important records. All these new data are used to regularly update an annotated checklist of molluscs and distribution maps of selected species (Horsák et al. 2022). The previous summary of new records covers the years 2015-2019 (Čejka et al. 2020) and 2020 (Čejka et al. 2021). In this paper, we present important faunistic records conducted in the Czech and Slovak Republics during 2021. The rules

Comments on individual species (genera)
Alzoniella sp. A single fresh empty shell, which clearly resembles the genus Alzoniella because of its size (height < 1 mm) and shape ( Fig. 1), was found in South Bohemia in the Šumava Mts, near the town of Volary. From the conchology, it looks identical to A. slovenica (Ložek & Brtek, 1964), a subterranean microsnail endemic to the west part of the Western Carpathians (Horsák et al. 2013(Horsák et al. , 2022. The shell has fine spiral lines that are not present in A. slovenica, which instead has fine and regular growth lines. Since the shells of many subterranean snails lack diagnostic characters, identification needs to be confirmed by molecular analysis. This is even more important in this case, as the occurrence of A. slovenica in Šumava Mts would be very surprising, both geographically and ecologically. Further studies are needed to obtain data on the distribution and habitats occupied in the Šumava Mts since the shell was found during a hydrobiological survey in the alluvial pools of the river Vltava and was only accidentally sorted out in the field from a sample taken in one of the sampled pools (Fig. 2). Since the pools are saturated with hyporheic water and the shell of this species is very fragile, it is very unlikely that the shell was washed away from a distant source.

Anisus septemgyratus (Rossmässler, 1835)
A rare freshwater snail that inhabits larger and non-temporary pools. It is rare, especially in the lowlands of the  eastern part of the Slovak Republic (Východoslovenská nížina). We have discovered a new isolated site of this species in the Teplý vrch reservoir in Rimavská kotlina (basin in south Slovakia).

Arion intermedius Normand, 1852
These two records in eastern Bohemia are from areas not previously occupied by this species, and their relationship to native mountain populations is questionable because of the recent invasion of this species (Fig. 3) (see Čejka et al. 2020 and 2021).

Cepaea nemoralis (Linnaeus, 1758)
The recent eastward spread of this species is also confirmed by a new record from central Moravia, in a private garden in the town of Drásov, NW of Brno (see also Čejka et al. 2021).

Cornu aspersum (O. F. Müller, 1774)
Three new sites of this species were found in the central part of the Czech Republic, two sites were also found in the western part of the Slovak Republic (in the city of Bratislava and the municipality of Diviacka Nová Ves, W Slovakia). See Čejka et al. (2020) for more information about the species.

Gyraulus acronicus (A. Férussac, 1807)
Rare snail with a scattered distribution in the Czech Republic and Slovakia. During a meeting of Czech and Slovak malacologists in 2021 (Malacodays 2021) new localities were discovered in South Bohemia.

Gyraulus rossmaessleri (Schmidt, 1852)
Rare snail inhabiting temporary pools and wetlands, scattered in the Czech Republic and the southwestern part of Slovakia. Two new sites were found in the known area of its occurrence (Silesia, South Moravia), while the finding in Lhota is the first record in South Bohemia.

Limacus flavus (Linnaeus, 1758)
Three new sites have been reported for this species, one in the southwestern part of the Slovak Republic ( Fig. 4) and two in the Czech Republic, in the central and southeastern parts. See Čejka et al. (2020) for more information about the species. For the taxonomic status of L. flavus and L. maculatus, see Čejka et al. (2020).

Limacus maculatus (Kaleniczenko, 1851)
It was first reported from SE Moravia in 2019 (Čejka et al. 2020). The colony at this site was repeatedly confirmed, and in 2021 a new colony was discovered at a nearby site of the pond Mlýnský rybník. Due to its nocturnal activity, this colony was also discovered by an entomologist collecting insects in the light at night (Fig. 5).

Monacha cantiana (Montagu, 1803) sensu lato
Four individuals of the genus Monacha were collected in Slovakia in the locality Bratislava -Dúbravka, Polianky (Fig. 6). They were initially identified as Monacha claustralis/cartusiana based on shell morphology, but genetic analysis by DNA barcoding using the standard mitochondrial cytochrome c oxidase (COI) gene showed that in all four cases the species belonged to Monacha cantiana s. l. and clearly different from the M. claustralis/cartusiana clade. Following BLAST results, we included in phylogenetic analysis representatives of the clades CAN-1 to CAN-6, which constitute the species complex of M. cantiana (Pieńkowska et al. 2020 and references therein), and also sequences of M. claustralis and M. cartusiana from Čejka et al. (2020). Of the four individuals, three appeared in clade CAN-2, previously reported only from northern Italy, and one in the rather divergent clade CAN-3, previously found in northern Italy and Wien, Austria (Fig. 7). Without nuclear sequence data and considering the difficult and unsettled taxonomy of the species complex, we call our samples provisionally M. cantiana s. l. The phylogenetic results indicate poor correspondence between mi-    tochondrial lineages and species in the M. cantiana complex. All sequences of M. cantiana SNMMo89-92 have been deposited in the BOLD database (accession numbers SNMMo89-SNMMo92) and GenBank (accession numbers OP100310-OP100313).

Monacha cartusiana (O. F. Müller, 1774)
A mollusc that has appeared in recent years in ruderal and semi-natural habitats in the Czech Republic. The first new record is from a xerothermic site near the railroad line in the town of Strakonice. A new record compared to 2021 from this town. The second new record comes from grassland on a road embankment in Malý Újezd near Mělník.

Pisidium amnicum (O. F. Müller, 1774)
In 2021, the abundant population of this pea mussel was found in the stream Řečice. This population is the only known recent population in the Vysočina region (Beran 2022). See Čejka et al. (2021) for more information about the species.

Pisidium globulare Westerlund, 1873
Some new sites with the occurrence of this rare and endangered species were found in the Czech Republic (Silesia, Southern Bohemia) and south Slovakia (near the village of Hrušovo, Revúcka vrchovina -upland in south Slovakia). See Čejka et al. (2020) for details about the species. Fig. 7. The phylogenetic tree was reconstructed by the Maximum Likelihood method and Hasegawa-Kishino-Yano model (Hasegawa et al. 1985) as the best-fitting model based on COI sequences and distances calculated with Kimura-2 parameter distances model (Kimura 1980)

Pisidium moitessierianum Paladilhe, 1866
The occurrence of this rare and endangered species was in 2021 confirmed in the river Ohře. For more information about the species see Čejka et al. (2020).

Pisidium pseudosphaerium J. Favre, 1927
The occurrence of this critically endangered species was in 2021 confirmed at several sites in Central Bohemia (Hrabanovská černava National Nature Monument) and Eastern Bohemia (Bohdanečský rybník National Nature Reserve). For more information about the species see Čejka et al. (2020).

Pisidium tenuilineatum Stelfox, 1918
In 2021, this pea mussel was found in the stream Řečice (Fig. 8). This population is the only known recent population in the Vysočina region (Beran 2022). See Čejka et al. (2020) for more information about the species. The known distribution in the Czech Republic is mentioned in Beran (2022) and in Slovakia in Beran & Čejka (2019).

Planorbis carinatus O. F. Müller, 1774
The occurrence of this rare species has been confirmed in the oxbow lakes of the river Vltava in Šumava and on the periphery of the Brdy Mts. See Čejka et al. (2020) for more information about the species.

Potamopyrgus antipodarum (Gray, 1843)
In 2021, some new sites were discovered. Only the more remarkable records outside the known range are mentioned (fringes of the Brdy Mts, Beskydy Mts). See Čejka et al. (2020) for more information about the species.

Pseudanodonta complanata (Rossmässler, 1835)
The persistent occurrence of this rare species has been confirmed in the rivers Odra, Labe, Dyje and Nežárka. See Čejka et al. (2020) for more information about the species.

Radix ampla (Hartmann, 1821)
Only notable new finds outside the known range in the upper section of the river Svratka are mentioned.

Radix lagotis (Schrank, 1803)
The occurrence of this species in the Czech Republic and Slovakia is still poorly known. The new finding comes from Eastern Bohemia. See Čejka et al. (2021) for more information about the species.

Segmentina nitida (O. F. Müller, 1774)
This species lives mostly in vegetated pools and ponds at lower latitudes, especially in floodplains of rivers. Notable new records outside its known range in the Brdy Mts are mentioned (Fig. 9).

Sinanodonta woodiana (Lea, 1834)
A non-native species that has been spreading rapidly lately. The new finding in the pond in the Brdy Mts is remarkable. See Čejka et al. (2020) for more information about the species.

Sphaerium nucleus (Studer, 1820)
A species that lives mostly in vegetated stagnant waters at lower latitudes, and its distribution is not well known. Occurrence in many areas in the Czech Republic was confirmed in 2021. See Čejka et al. (2020) for more information about the species.

Tandonia kusceri (Wagner, 1931)
Two new sites were recorded in the Slovak Republic (cemeteries in the towns of Dunajská Streda and Zvolen). See Čejka et al. (2020) for more information about the species.

Theodoxus danubialis (C. Pfeiffer, 1828)
This species is very rare in the Czech Republic and its recent occurrence is known only from the lower section of the river Dyje, while in Slovakia it is more common in the Danube. The persistent occurrence of a rich population in the Dyje was confirmed in 2021.

Unio crassus Philipsson, 1788
Some valuable records of this endangered species were documented in the Czech Republic in 2021. The occurrence of the extensive population of U. crassus was confirmed in the river Odra (Fig. 10) and a channel of the river Bečva in Hovězí. The surviving small population was confirmed in the stream Martinický potok. New sites with the occurrence of this bivalve were found in the Pardubice region (the stream Trotina) and in the Olomouc region (the river Morava in Olomouc). For more information about the species, see Čejka et al. (2020, 2021).

Vertigo angustior Jeffreys, 1830
An isolated new population was found in southern Bohemia on the edge of the Lhota u Dynína (natural monument). Another new and isolated site of this species was found in the area of the town of Stupava in a small wetland in the floodplain of a stream (Čačaný & Čejka 2020) (Fig. 11). See Čejka et al. (2020) for more information about the species.

Vertigo moulinsiana (Dupuy, 1849)
This rare species, adapted to vegetation above flooded sites, seems to occur somewhat more frequently in the lowland meadows of the Bílé Karpaty PLA, even in nature reserves and other well-known sites which has often been visited in the past. The identification in the field was confirmed especially by comparison with Vertigo antivertigo (Draparnaud, 1801), which also lives in the same lowland meadow. Two new records of V. moulinsiana in the Chmelinec Nature Reserve and in the Mechnáčky Nature Reserve in 2021 are based on routine biomonitoring of malacological assemblages. The record of this species in the Hrnčárky Nature Reserve reported from 2020 was also independently confirmed. There are several more places on the list to be visited during the current monitoring cycle, where this largest Vertigo could also be found. How does it conquer new places and what has changed in the area and in the fens to make this possible or necessary, that is the question. Malacologists, as regular visitors to fen sites, have already been excluded from the possible vectors.

Zonitoides arboreus (Say, 1816)
This species is native to North America and is now very common in moist greenhouses in CZ and SK. Shells of this species were found in a greenhouse in the substrate used for growing orchids. The orchids were exhibited during several months of public exhibition in the city of Strakonice.