A NEW SPECIES OF BYTHIOSPEUM ( PROSOBRANCHIA : HYDROBIOIDEA : MOITESSIERIIDAE ) FROM SOUTHERN POLAND

In the paper the authors describe Bythiospeum neglectissimum, a new species of Bythiospeum Bourguignat, 1882 found at a few stations in Southern Poland. It is characterised by its stout and Iow, conical and minute shell with the aperture closely adjoining and narrow, and by the slender, multifolded verge having a terminal dagger-shaped filament and medially an apparent lobe. The description comprises the shell, operculum, mantle, head, ctenidium, osphradium, radula, stomach, verge, and female reproductive organs. The species surpasses far the known range of the genus Bythiospeum, and its bionomy is completely unclear. key WordS: shell, mantle/head pigmentation, verge, female reproductive organs Folia Malacologica 3/1989 was originally published as No. 1216 of Scientific Bulletins of University of Mining and Metallurgy, Cracow. This digitalised version was prepared by the Association of Polish Malacologists and first published on-line on December 30th, 2016. http://dx.doi.org/10.12657/folmal.003.006 Folia Malacol. 3: 95–101

A NEW SPECIES OF BYTHIOSPEUM (PROSOBRANCHIA: HYDROBIOIDEA: MOITESSIERIIDAE) FROM SOUTHERN POLAND Ab s t r a c t : In the paper the authors describe 8ythiospeum neglectissimum, a new species of 8ythiospeum Bourguignat, 1882 found at a few stations in Southern Poland.It is characterised by its stout and low, conical and minute shell with the aperture closely adjoining and narrow, and by the slender, multifolded verge having a terminal dagger-shaped filament and medially an apparent lobe.The description comprises the shell, oper~ulum, mantle, head, ctenidium, osphradium, radula, stomach, verge, 9nd female reproductive organs.The species surpasses far the known range of the genus Bythiospeum, and its bionomy is completely unclear .Bythiospeum neglectissimum n. sp.

DIAGNO.SIS
A species of Bythiospeum Bourguignat, 1882 with a stout and low shell With the aperture narrow and closely adjoining, and the verge slender, multifolded, terminally with a dagger-shaped filament while medially with an apparent lobe.DESCRIPTION She 11 : conical and rather low and stout (Figs 1 -6), sometimes more slender (Fig. 5).Whorls' growth regular but rapid.Body whorl broad and high, slightly variable in height.Whorls moderately convex, suture rather shallow and usually poorly marked.Whorl number: 4 1/2 -5 1/2, 1mm Figs l-8 -Bythiospeum neglectissimum from the locus typicus: 1 -holotypus, 2-6 -shell variability, 1 -cte~dium and osphradium 8 -renal and pallial regions of female reproductive orgare .usually about 5. Apex narrow but rather blunt.Mouth relatively small and narrow, elliptical in outline, angle in its right upper part marked rather strongly -strongly.Mouth not protruded but closely adjoining to body whorl.Peristome nearly continuous or continuous but parietal lip slightly marked.Outer lip absent.Umbilicus conspicuous and always present, although more or less trough-shaped since partly covered with parietal lip.Holotypus (Fig. 1) dimensions: shell height: 1.85 mm, shell breadth: 1.16 mm, mouth height: 0.75 mm, mouth breadth: 0.66 mm; 5 whorls .Variability range of shell dimensions: height: 1.85 -2.31 mm, mean: 2.08 mm, standard deviation: 0.17~5; breadth: 1.12 -1.37 mm, mean: 1.2~ mm, standard deviation: 0 .0930.Shell proportions slightly variable (correlation coefficient for shell height and breadth: f = 0.9041).Shell yellow to brownish, translucent, dark-pigmented mantle clearly visible through shell walls.Shell surface smooth and glossy, without any conspicuous sculpture: only With very fine and slightly marked.growth lines.Shell variability slight.
0 p e r c u 1 u m : conchiolin and spiral, extremely thin and transparent, nearly colourless.R a d u l a : resembles the radulae of Paladilhiopsis photographed by Pez-20li andGiusti (1975 and1980).All cusps prominent, long and narrow, and Sharp.Central tooth formul~ 3 i !i l , especially basal cusps as well as three central ones at tooth plate markedly long .Lateral tooth: 1 -1 -3, domination of biggest cusp sharply marked.
V e r g e : straight and uni -armed b~t with an apparent lobe on its left 8 ide (Fig. 13).Long and slender, proximally and medially with numerous folds, distally in the form of a long and narrow, unfolded, dagger-shaped filament.Vas deferens clearly visible inside filament.Penis length: about 0.6 mm.
De r i vat i o no minis: from Latin: neglectum, -issimum -the most neglected, since the occurrence of any representative of the genus ~thiospeum in Poland and/or neighbouring countries was astonishingly o~ verloDked for so long.
L o c us t y p i c u s : Brama Krako.wskaRocks in the Prqdnik Valley, Ojcow National Park.In the litter covering the ground in the close neighbourhood of the rocks, in a deciduous forest.The Prqdnik Valley is composed of Jurassic limestones.

MATERIAL EXAMINED, KNOWN DISTRIBUTION
The material from the locus typicus consisted of eight empty shells and nine animals still alive although dormant and desiccated.After keeping the animals for a few days in 100% humidity, the material was ready for dissection.The holotypus (Fig. 1) as well as all the paratypes, are in the collection of the Zoological Museum of Jagiellonian University, Krak6w, Poland.
Besides the locus typicus, some specimens of B. neglectissimum were found also in the Mnik6~ Valley and at Panie~skie Skaly in Krak6w.Both the localities are similar in character to the locus typicus.

DISCUSSION
Taxonomy: both the shell and soft part morphology and anatomy, When compared with drawings and descriptions in the literature (e. g.Gayer 1927, Balling 1965, Boaters 1971, Bernasconi 1976, 1984and 1985, and Giusti and Pezzoli 1980) confirm the pla~ement of the described new spe-Cies within the genus Bythiospeum.All the above data, however, confirm the species disti.nctn•ess of the Polish Bythiospeum which displays several distinct character states.On the other hand, the question of the relations between this species and the qther known representatives of Bythiospeum remains open.It must also be checked if B. neglectissimum is the only ~hiospeum species occurring in Poland.
Z o o g e o g r a p h y : the occurrence of Bythiospeum is especially note-Worthy since the closest localities of the genus are about 500 km far from the Polish ~nes.This throws a new light on the distribution character of some hydrobioid gastropods.E c o 1 o g y : the representatives of the genus Bythiospeum are commonly known as inhabitants of underground waters.In connection with this habitat character, they usually have the mantle slightly pigmented or even unpigmented, and rudimentary eyes.B. neglecUssifWm has the mantle intensively deeply pigmented black, and the eyes well developed, relatively very big.In general, \he troglobiotic animals may have no eyes or enormously big ones.B. neg-lectissimym may be the latter case.Anyway, the species seems only facultatively 'l:ragDbiotic.It has not been found in any spring in Poland, and all its stations known are typically terrestrial.Only some periodical water percolation might occur there, although it still has not been observed.The collected gastropods weFe dormant, their rectums and bursae copulatrix empty, but still alive.Hence, the bionomy of B. neglectissimum seems enigmatic and unusual, and needs further study.
J FALNIOWSKI AND ..JOZEF §TEFFEK 5 o f t p a r t e x t e. r n a l m or ph o l o g y : mantl~ on body whorl .uniformlydeep black; outer surface of visceral hump somehow less intensi-Vely pigmented black, pigment diluted laterally.Head (Figs 10 -12) typically hydrobioid, with moderately long snout and rather slender tentacles.Tentacles and foot with no pigment, while snout intensively pigmented black.Head pigmentation (Figs 10 -12) , in gene r al, composed of black and grey big spots combined with an area completely lacking pigment.Eyes very big, Proportionally twice bigger than in Bythinella.C ten id i u m : typically hydrobioid (Figs 7 -8), with 15 -19 moderately long and straight lamellae.0 s ph radium: long and narrow, almost straight, tube-shaped (Figs 7 -8).