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27 (2) 2009

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The taxonomic status of Limnaeus gebleri Middendorff, 1851 (Gastropoda: Pulmonata: Lymnaeidae)

> AbstractThe taxonomic position and geographic distribution of an endemic Siberian lymnaeid species, Lymnaea (Radix) gebleri (Middendorff, 1851), are discussed. This species is closely allied to L. (R.) auricularia (Linnaeus, 1758) but can be dis-tinguished from the latter by its conchological features. L. gebleri is thought to be widely distributed in East Kazakhstan, Mountain Altay and Sayan Mountains (Tuva), however, the examination of all available collections, including the lectotype of L. gebleri, has revealed that all reliable fi ndings of this species were made from Zaisan Lake (East Kazakhstan) only. Perhaps, L. gebleri is an endemic of this large lake and its population needs for special assessment since the hydrological regime of Zaisan has been changed in 1960, when the Bukhtarma Reservoir was organized.

> Kurzfassung Diskutiert werden der taxonomische Status und die geographische Verbreitung der in Sibirien endemischen Art Lymnaea (Radix) gebleri (Middendorff, 1851), die L. (R.) auricularia (Linnaeus, 1758) nahe steht, sich jedoch von letzterer durch den Bau des Gehäuses unterscheidet. Laut Literaturangaben ist die Art in Gewässern Ost-Kasachstans, des Altai-Gebirges und des Sajan (Tuva) verbreitet. Das Studium allen zugänglichen Materials dieser Art, einschließlich des Lectotypus, zeigte, dass die Individuen, die der Originalbeschreibung entsprechen, nur im See Zajsan gefunden wurden. Wahrscheinlich muss L. gebleri als eine für diesen See endemische Art angesehen werden. Der heutige Zustand der Population muss unter dem Aspekt der Veränderung des hydrologischen Regimes des Sees nach dem Bau der Buchtarminsker Talsperre am Fluss Irtysch im Jahr 1960 gründlich untersucht werden.

> Резюме В работе обсуждаются таксономический статус и географическое распространение эндемичного сибирского вида прудовиков Lymnaea (Radix) gebleri (Middendorff, 1851), который близок к L. (R.) auricularia (Linnaeus, 1758), но отличается от последнего по строению раковины. По литературным данным, вид распространен в водоемах Вос-точ ного Казахстана, Горного Алтая и Саян (Тува). Изучение всех доступных материалов по этому виду, включая лекто тип, показало, что особи, соответствующие оригинальному диагнозу вида, обнаружены только в озере Зайсан. Вероятно, L. gebleri следует рассматривать как эндемичный для озера вид, нынешнее состояние популяции которого нуждается в тщательном изучении ввиду изменения гидрологического режима оз. Зайсан после сооружения в 1960 г. Бухтарминского водохранилища на р. Иртыш.

> Key words

Gastropoda, Lymnaeidae, Lymnaea (Radix) gebleri, distribution.

Introduction

The history of malacology in Siberia has started 180 years ago, when the fi rst scientifi c reports about conti-nental molluscs of this region were published (GEBLER 1829a, b). The author, Friedrich-August von Gebler (Fig. 1), was a native of Saxony, who in 1810 emi-

grated to Russia and since 1836 became a citizen of Russian Empire. For almost 40 years Gebler lived in Barnaul City (Altay, south part of Western Siberia) and worked there as a physician. He is known as a pioneer of biological and geographical investigations in the

MAXIM V. VINARSKI

Museum of Siberian Aquatic Molluscs, Omsk State Pedagogical UniversityTukhachevskogo Emb. 14. 644099. Omsk, Russian Federation radix.vinarski@gmail.com

Received on April 30, 2009, accepted on August 11, 2009.

Published online at www.mollusca-journal.de

VINARSKIJ: Taxonomic status of Limnaeus gebleri150

Altay region and as an author of several geographical, botanical and entomological surveys. His malacologi-cal publications (GEBLER 1829a, b) contain the fi rst list of Siberian continental molluscs based on the investiga-tion of collections of the Barnaul Museum. Later, another prominent Russian zoologist of Ger-man origin, Alexander Theodor (Aleksandr Fyodoro-vich) von Middendorff, who performed his famous sci-entifi c travel through Siberia in 1842–1845 (VORONTSOV 2004; SOKOLOV & SHISHKIN 2005), examined Gebler’s malacological collection and found there a new species of lymnaeid snails named after its collector as Limnaeus gebleri Middendorff, 1851 (MIDDENDORFF 1851: 292). Possibly, this species was included in the fi rst Gebler’s list (GEBLER 1829a: 55) as Bulimus auricularis. The taxonomic position of L. gebleri is still not fi xed. Though CLESSIN (1886: 381) considered it to be a distinct species, most subsequent authors regarded it as a probable full synonym of Lymnaea auricularia (L., 1758) [see HUBENDICK 1951: 188] or as a subspe-cies of the latter (LAZAREVA 1967; KRIVOSHEINA 1979). From the WESTERLUND’s (1885, see Register, S. 4) opin-ion, L. gebleri is a synonym of L. ampla var. monnardi (Hartmann). In the present-day Russian taxonomy, the taxon under discussion is treated as a valid species of the subgenus Radix Montfort, 1810 (KRUGLOV & STAR-OBOGATOV 1989, 1993; KRUGLOV 2005; KANTOR et al. 2009) that is closely allied to L. auricularia (L., 1758). This species is believed to be distributed in the Altay-Sayanian malacofaunistic province (KRUGLOV & STAR-OBOGATOV, 1993).

The aim of this brief note is to analyze all available data on L. gebleri in order to clarify its taxonomic po-sition and geographic distribution.

Material and methods

The malacological collection of the Zoological Insti-tute of the Russian Academy of Sciences, Sankt-Pe-tersburg (ZIN, hereafter) was used. The lectotype of Limnaeus gebleri (Fig. 2, A−C) designated by LAZA-REVA (1967) is housed there as well as several decades specimens of this species from waterbodies located in Eastern Kazakhstan and Mountain Altay (collec-tions of L.V. Krivosheina, Ya. I. Starobogatov). The author’s own fi eld investigations were carried out in different parts of the Mountain Altay in the August of 2008. Samples of lymnaeids from the steppe part of the Altay Region from the collection of the Museum of Siberian Aquatic Molluscs (Omsk State Pedagogi-cal University; MSAM, hereafter) were examined as well. In total, nearly 110 specimens of snails labelled as L. gebleri are used. 101 shells of L. gebleri from Zaisan Lake and shells of L. auricularia from some waterbodies of Urals and Siberia were measured along a standard scheme (KRUGLOV 2005) with precision to the nearest 0.1 mm.

Results and discussion

The examination of the ZIN collection has revealed that at least two conchologically distinct forms are placed under the label Lymnaea gebleri. The fi rst of these (Fig. 2) is that inhabits Zaisan Lake situated in Eastern Kazakhstan. This form corresponds to the original description of the species given by MIDDEN-DORFF (1851, see Fig. 3), and the lectotype of L. gebleri itself belongs to this form. It is characterized by a very large aperture (sometimes irregular-shaped) and a di-minutive spire that is almost always hidden behind the aperture (see Fig. 2, A, E). In some shells, the spire is visible but in these cases the uppermost point of the ap-erture is elevated higher than the shell apex (see Fig. 2, D). This trait differs L. gebleri from the common Pal-aearctic species L. auricularia, whose shells have less developed aperture (see below). Though the lectotype is labelled as collected in Barnaul (see Fig. 2, B−C), its shell looks identical with L. gebleri shells from Zaisan Lake, and LAZAREVA (1967) has questioned the true sampling locality of the Gebler’s materials. She sug-gested that shells from the Gebler’s collection were

Fig. 1. Friedrich-August von Gebler (from http://www.agkm.ru/history).

151M o l l u s c a 27 (2) 2009

really collected in Zaisan Lake since snails with such shells were found neither in vicinity of Barnaul nor in other large lakes of Altay. The second conchological form of L. gebleri is distributed in Eastern Kazakhstan and Mountain Altay but it did not record from Zaisan Lake. The shell of this form is of typical for L. auricularia shape (Fig. 4) and can be distinguished from the latter by a slightly lower spire only. The uppermost point of the aperture is always situated below the shell apex and usually below the upper suture of the body whorl (see Fig.

4). Thus, this form does not agree with the original diagnosis of L. gebleri since MIDDENDORFF (1851) de-scribes this species as having an involute shell with aperture expanded over the spire (“apertura … ultra spiram supra expansa”, italics from the author’s origi-nal text). In samples of L. auricularia from the steppe lakes of Altay examined by me, one can fi nd such low-spired shells alongside with shells of normally developed spires (Fig. 5, A−C), and, in my opinion, the second conchological form of L. gebleri is noth-ing but a form of L. auricularia infraspecifi c variation.

Fig 2. Shells of Lymnaea gebleri from Zaisan Lake (ZIN collection). A. The lectotype. B. The original Middendorff’s label. C. The original Gebler’s label. D–E. Shells collected in 1882 (E) and 1965 (D). Scale bars 5 mm.

A

B

C

D E

VINARSKIJ: Taxonomic status of Limnaeus gebleri152

I failed to fi nd any evidence of a morphological hiatus between the second form and L. auricularia inhabit-ing the waterbodies of Western Siberia. The picture of the L. gebleri’s genital structure provided by KRUGLOV (2005: 254) is based on dissection of a specimen from Leninogorsk Town (East Kazakhstan Region), though the shell illustration (KRUGLOV 2005: 250) depicts the lectotype. Having examined shells from Leninogorsk (ZIN), I found that these most probably should be de-termined as belonging to L. auricularia. This sugges-tion is corroborated by the fact that KRUGLOV (2005) did not reveal any signifi cant differences in the genital structure between L. auricularia and L. gebleri, and he reported almost equal values of the index of the copu-lative apparatus (the ratio between lengths of praepu-tium and penis sheath): 1.13 for L. gebleri and 1.10 for L. auricularia. KRUGLOV & STAROBOGATOV (1991) and PROZOROVA & SHARYI-OOL (1999) reported L. gebleri from deep mountain lakes of Tuva (Southern Siberia), however no picture of shell is presented in their arti-cles and the materials from Tuva are absent in the ZIN collection. Hence, I am not able even to hypothesize about the true identity of snails from this region. Thus, the anatomical structure and true range of L. gebleri are still unknown. Most probably, this species is endemic of Zaisan Lake as there are no reliable fi nd-ings of it from another parts of Kazakhstan and South-

ern Siberia. I am inclined to accept LAZAREVA’s (1967) opinion about the true locality of Gebler’s specimens (from Zaisan Lake, not from Barnaul). The situation when a species has a very narrow range of distribu-tion and is recorded from a single waterbody is not so rare in the (sub-)genus Radix. I would like to mention Radix skutaris Glöer et Pešić, 2008 (endemic of Ska-dar Lake, Montenegro; see GLÖER & PEŠIĆ 2008) and Radix pinteri Schütt, 1974, endemic of Prespa Lake (Macedonia, see SCHÜTT 1974) as good examples of this kind. Both species are endemics of large deep lakes that may be compared to Zaisan Lake (105 km in length, maximum depth is 15 meters). Deep ancient lakes are well known among biologists as places of intensive taxonomic diversifi cation in different groups of aquatic animals including molluscs (BOSS 1978; STAROBOGATOV & SITNIKOVA 1990), and there are no a priori reasons to refute the possibility of a speciation event in Zaisan Lake that would have resulted in for-mation of an endemic species of Radix here. However, an alternative explanation treating L. ge-bleri as mere a form of infraspecifi c variation of L. auricularia should be discussed here. Shells of lym-naeid snails inhabiting deep lakes with strong wave action are known to be very variable and these often demonstrate abnormalities in their shape and propor-tions (GEYER 1927, 1929a, b). I have examined several

4 ×Tab. 1. Morphological characteristics of shells of L. auricularia and L. gebleri. Limits of values (above line) and mean values along with the standard deviation (under line) are given.

Parameters Lymnaea auricularia,Bol’schoye Miassovo

Lake, South Urals, Russia (MSAM)

Lymnaea auricularia, Travnoye Lake, lowland Altay, Russia (MSAM)

Lymnaea gebleri, Zaisan Lake,

East Kazakhstan (ZIN)

Number of shells measured 30 34 37Whorls number 4.00 – 4.75

4.43 ± 0.164.00 – 4.504.16 ± 0.15

3.37 – 4.253.57 ± 0.20

Shell heiht (SH), mm 19.8 – 32.825.3 ± 3.1

12.8 – 29.818.0 ± 5.1

16.0 – 29.221.0 ± 3.1

Shell width (SW), mm 14.3 – 25.918.5 ± 2.7

9.4 – 26.614.2 ± 4.9

14.6 – 28.720.0 ± 3.5

Spire height (SpH), mm 5.5 – 8.06.5 ± 0.7

3.5 – 6.04.5 ± 0.7

1.4 – 4.62.7 ± 0.3

Body whorl height (BWH), mm 15.8 – 29.622.0 ± 3.0

10.7 – 27.916.1 ± 5.1

15.2 – 28.120.0 ± 3.1

Aperture height (AH), mm 15.6 – 27.220.0 ± 2.9

8.8 – 25.614.0 ± 5.2

14.0 – 32.220.2 ± 3.9

Aperture width (AW), mm 10.5 – 17.213.6 ± 1.8

6.2 – 20.811.0 ± 4.4

10.3 – 23.515.4 ± 3.1

SW/SH 0.66 – 0.960.74 ± 0.06

0.73 – 0.910.78 ± 0.04

0.82 – 1.050.95 ± 0.05

SpH/SH 0.21 – 0.320.26 ± 0.03

0.18 – 0.350.26 ± 0.05

0.06 – 0.190.13 ± 0.03

BWH/SH 0.70 – 0.920.87 ± 0.04

0.84 – 0.940.88 ± 0.02

0.91 – 1.150.95 ± 0.04

AH/SH 0.73 – 0.840.79 ± 0.03

0.65 – 0.860.75 ± 0.06

0.82 – 1.190.96 ± 0.07

AW/AH 0.56 – 0.760.68 ± 0.04

0.66 – 0.870.78 ± 0.05

0.68 – 0.950.76 ± 0.05

153M o l l u s c a 27 (2) 2009

4

Fig. 3. The facsimile of the original description of Limnaeus gebleri with the illustration of the holotype’s shell (MIDDENDORFF 1851).

Fig. 4. Shells of L. auricularia from East Kazakhstan and Altay labelled as L. auricularia gebleri or as L. gebleri (ZIN). A. Altay Republic, a lake near the entrance of the Chu depression. B–C. East Kazakhstan Region. Ust’-Kamenogorsk City, airport. D. Altay Republic. A lake in the fl oodplain of the Shilovka River. Scale bars 5 mm.

A B C

D

VINARSKIJ: Taxonomic status of Limnaeus gebleri154

thousand of L. auricularia shells from Siberia, Eastern and Central Europe (ZIN, MSAM collections) and I failed to fi nd specimens having such a specifi c shape as shells of L. gebleri have. In the Ob’ River drainage basin, there are two mountain regions with deep lakes of tectonic origin that would induce shell variations of L. auricularia similar to those observed in L. gebleri from Zaisan. None of these lakes, however, is inhab-

ited by L. auricularia with gebleri-like shells. In the South Urals, lacustrine populations of L. auricularia exhibit a quite typical appearance for this species’ shell (see Fig. 5, D−E). In the mountain waterbod-ies of North Kazakhstan (Kokshetau ridge), shells of L. auricularia keep typical shape and proportions though its spires are slightly narrower and more pro-longed as compared with spires of L. auricularia from

Fig. 5. Variation in L. auricularia shells from the steppe Altay and mountain waterbodies of Western Siberia and adjacent territories (MSAM collection). A–C. Peschanoye Lake (Altay). D–E. Bol’shoye Miassovo Lake (South Urals, Ilmeny Nature Reservation). F–G. Bol’shoye Chebachye Lake (North Kazakhstan, Kokshetau ridge). Scale bars 5 mm.

A B

C

F G

D E

155M o l l u s c a 27 (2) 2009

lowlands (see Fig. 5, F−G). Judging from the liter-ary sources, the same situation is observed in another mountain regions of Eurasia. For example, in the Bod-ensee Lake (south Germany), shells of L. auricularia abundantly depicted by GEYER (1929a, b) are highly variable but none of them demonstrate features similar to shells of L. gebleri from Zaisan. Comparative anal-ysis of shell morphology of L. gebleri and L. auricu-laria from deep mountain lakes revealed signifi cant differences between the species (Table 1). Hence, it is unlikely that L. gebleri is only a lacus-trine form of L. auricularia variation. The last reliable fi ndings of L. gebleri in Zaisan Lake were made in 1965 by KRIVOSHEINA (ZIN col-lection). Since 1960, the lake has became a part of the Bukhtarma Reservoir, a large artifi cial waterbody with a regulable hydrological regime. It is not known how these changes might infl uence the population of L. gebleri, and special assessment is needed in order to evaluate the current situation of this interesting en-demic mollusc.

Acknowledgements

I am indebted to Dr Pavel Kiyashko, curator of the ZIN col-lection of land and freshwater molluscs as well as to Mrs. Lidiya Yarochnovitch, who generously helped me during my work with the ZIN collection (this collection has a fi -nancial support from the Russian Ministry of Science and Technologies, grant number 2002-03-16). I want to thank Peter Glöer (Hetlingen, Germany), who provided me with a number of papers by Clessin, Geyer and other German authors. Dipl.-Biol. Katrin Schniebs (Dresden, Germany) is acknowledged for translation of the German Kurzfassung.

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