A History of the Occurrence of Lymnaea glabra (Gastropoda: Pulmonata) in IrelandAuthor(s): James HurleySource: The Irish Naturalists' Journal, Vol. 20, No. 7 (Jul., 1981), pp. 284-287Published by: Irish Naturalists' Journal Ltd.Stable URL: http://www.jstor.org/stable/25538521 .

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284 Ir. Nat. J. Vol. 20 No. 7 1981

A HISTORY OF THE OCCURRENCE OF LYMNAEA GLABRA

(GASTROPODA: PULMONATA) IN IRELAND

James Hurley

Grange, Kilmore, Co Wexford

Von Siegfried (in lilies 1967, p 102) gives the global distribution of the freshwater snail Lymnaea glabra (Muller, 1774 [= Galba (Omphiscola glabra) (Miiller)] as 'NW

European, extending approximately from Ireland eastwards to Czechoslovakia and from the

French foot-hills of the Pyrenees northwards to southern-most Norway.' Over 100 years

before, Reeve (1863, p 165) noted that 'This is one of the few European inland mollusks which.is peculiar to the Germanic portion of the Continent.'

L. glabra is very rare in Ireland having been reliably recorded on only a few occasions

during the past 150 years. The last record was in 1929. These early records are reviewed and a new record is reported.

EARLY RECORDS OF LYMNAEA GLABRA

BELFAST:

J. G. Jeffreys first recorded/,, glabra (= Limneus elongatus Draparnaud, 1805) from

Ireland in 1833 (1833, p 520). This record was based on the apparent finding of a shell of L.

glabra in Belfast c. 1830 by the Rev James Bulwer. The record was passed to Jeffreys by the Rev Dr Goodall, Provost of Eton, and was accepted as authentic by Jeffreys. He

subsequently included it in his bookBritish Conchology (1862, p 118). William Thompson, who lived in Belfast was in contact with Jeffreys and Bulwer concerning the shell and in his

catalogue of the Land of Freshwater Mollusca of Ireland (1841), included Bulwer's statement that he regarded it as "but a variety ofL. palustris.' It would seem that Thompson doubted the record. It was rejected by Stelfox (1911, p 129) and Phillips (1918, p 79). However Scharff included it in his Irish list (1892, p 151).

CORK:

On 8 June 1840 in a letter from Jeffreys to Thompson about the Bulwer shell, Jeffreys writes 'I have, however, two or three undoubted specimens among a collection of Irish

shells, which I purchased about three months ago from Mr John Humphreys of Cork ? the

tray which contained them was labelled "Cork".' Thompson checked with Humphreys regarding the source of these specimens and learhed that Humphreys 'had not identified the

species, but that the note of locality appended to the shells.was strictly correct' (p 120-121). 'Cork' could refer to either the city or the county. Humphreys (1845, p 6)

explained that L. glabra (= Limneus glaber Gray, 1840) was 'found once near Cork, I

believe near Blarney'. Phillips (1918, p 78) noted that 'in an old manuscript list of Cork shells which I have seen it is stated that Mr. Humphreys could not remember where he had found this species.'

Both Stelfox (loc. cit.) and Phillips (loc. cit.) rejected this record but Stelfox (1929, p 7) subsequently gave Humphreys the benefit of the doubt after the record of Roche (1929) had been reported.

In 1904 Welch stated that Lymnaea glabra was found 'in one station only and that

extremely local' (1904 p 17). He credited the record to Thompson ?

'by Thompson (footnote: Natural History of Ireland Vol 4, p 305) from near Cork (this it would be well to have verified).' This would seem to be an error as Welch gives as his source a copy of

Thompson's Catalogue note of Humphreys' 1840 record.

A second record ofL. glabra from Cork was drawn to my attention by Dr M. P. Kerney (pers. comm.) A transcript of the entry in MS vice-comital census notebooks of the

Conchological Society of Great Britain and Ireland for 1886 relating to L. glabra reads 'Limnaea glabra. Cork, two sent. W. H. Evans [authenticated by] J. W. Taylor, 23.xii.

1886.' Kerney comments ' It is not quite clear whether Cork city or Co Cork are meant, but

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Ir. Nat. J. Vol. 20 No. 7 1981 285

the record has been entered up under Cork Mid (H4). J. W. Taylor would have known this species very well in Yorkshire, and I think one can take the identification as being reliable.'

This record of Evans appears to have gone un-noticed as none of the authors subsequently reviewing the Irish list has referred to it.

A third Cork record forL. glabra came to light in 1918 (Jackson p 77) and relates to a pre-1895 mollusc collection of Lord de Tabley. The collection contained specimens of named L. glabra which were labelled 'Cork'. One the death of de Tabley c. 1895 the collection went to Mrs. Gresham of Knutsford who presented it to the Manchester Museum in about 1918. Jackson (loc. cit.) stated 'all the shells agree closely with English specimens

of L. glabra" and 'are quite unlike any variety of L. palustris known to me.'

These three Cork records, Humphreys c. 1840, Evans 1886 and de Tabley pre-1895 appear to be the only authentic records forL. glabra before 1900. However, R. A. Phillips (1918, p 78-79) commenting on Jackson's note of the de Tabley specimens and reviewing

previous records concluded that the evidence forL. glabra as a native Irish species was 'too

imperfect to be accepted . . . .'

Two other references toL. glabra tend to confuse the situation and may be dismissed:

1 KILKENNY:

P. H. Grierson drew up an annotated list of the Mollusca of Co Kilkenny in the first half of each of the years 1902 and 1903. He recorded some eighty-two species and although he did not findL. glabra himself he stated

' Recorded by Thompson from Kilmacow.' (1903, p

110). This would appear to be an error on Grierson's part and the record has been deleted from those held by the Institute of Terrestrial Ecology (Kerney, pers. comm.). 2 DUBLIN:

In 1911 Stelfox recorded his doubts about L. glabra and did not include it in his Irish list. He suggested that the records of Thompson (Bulwer), Humphreys and others were 'perhaps the young of a slender form of L. palustris'. He continued 'there are several old records for this shell ? Cork, Dublin and Belfast ? but no specimens are forthcoming.'

This is the first mention of Dublin as a site forL. glabra and no source or location is given. Adams' comprehensive list of Co's Dublin and Wicklow Mollusca (1878) does not include L. glabra so it seems probable that Stelfox's inclusion of Dublin as a locality was a slip.

LYMNAEA GLABRA ESTABLISHED AS AN IRISH SPECIES IN WEXFORD In April 1928 Geraldine Roche found 'very large numbers' ofL. glabra in all stages of

development in a ditch near Ballymacar bridge on the main road between New Ross and Wexford, [S 7426] (1929, p 182). This settled the issue of its status in Ireland and Stelfox restored L. glabra to the Irish list (1929).

MOST RECENT RECORD OF LYMNAEA GLABRA IN IRELAND On 7 October 19791 happened upon a small population of L. glabra in a field drain in

Shelmaliere Commons (E.D. Aughwilliam) [S 9617] in Co Wexford (H 12) some 23 km away from the site of Roche's record. The station lay at an altitude of 183 m on the SW slope of the Cambrian quartzite hill called Forth Mountain, 9 km WS W of Wexford Town. The drain bordered one of the few arable fields in a reclaimed podsol landscape dominated by

Calluna heath and young Pinus plantation. The drain itself was narrow (<1 m), poorly defined and overgrown with grasses. It was carpeted by blinks (Montia fontana L.) and there were also sheep sorrels (Rumex acetosella L.) and starworts (Callitriche sp.), all

overhung by brambles (Rubus fruticosus agg.) and hawthorns (Crataegus monogyna J acq.) in the roadside hedgerow. The shallow (c. 160 mm) water flowed, with minimal current, through the excessive growth, often leaving its channel to flood marshy hollows. The water

was acid (pH 4.8) but was not too soft for snails (calcium hardness 30 mgL*1). The muddy substrate was littered with fallen leaves.

The L. glabra colony was confined to a 40 m stretch of drain. Snails were most

commonly found under water on the vegetation at the sides of the drain. One snail was seen crawling on the surface film presumably feeding by the pedal ciliary action common in

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286 Ir. Nat. J. Vol. 20 No. 7 1981

some other Lymnaeidae. Jeffreys (1862, p 118) noted this point ? 'It is an exceedingly

sluggish and timid mollusk, but ventures occasionally on a very short floating excursion . . . .' Several specimens were found with difficulty in the marshy hollows; very few were found on the substrate of mud. Empty shells of dead snails were very rare in the

sievings of the substrate. The locus of maximum concentration was a small pool into which the drain disgorged after being piped under a gateway. Sampling was made difficult by the dense vegetation and the need for conservation but handpicking and dipping with a sieve for

thirty minutes within a single biased square quadrat of side 1 m produced a density of 67 m"2. It appeared that the entire population probably numbered no more than several hundred individuals and was confined to an area of 20 m2. The distribution of shell size peaked at two levels: juveniles (mean 2.4 x 1.3mm) and sub-adults (mean 13.1 x 4.6 mm) indicating a

spawning in late summer/early autumn. Juveniles made up slightly more than 50% of the sample. The largest adult recorded reached a height of 14.6 mm.

Other Mollusca found in association with L. glabra were: Drain Bed: Pisidium casertanum (Poli) ?

abundant; Lymnaea truncatula (Muller) ? rare.

Drain Sides: Nesovitrea hammonis (Strom) ? rare; Oxychilus cellarius (Muller)

? scarce.

Marshy Hollows:/,, truncatula ? scarce; Arion ater (L.) (sensu stricto)

? scarce; P.

casertanum ? scarce.

Subsequent to the original sighting of the colony a number of random checks were made and some observations may be of interest.

General Observations

The falling autumn leaves covered the drain bed and while juveniles were invariably to be found on decaying leaves of Rubus fruticosus they were never seen on the leaves of Crataegus monogyna which were abundant.

Heavy and prolonged thundery rain in the fourth week of October flushed out the drain. Many adults were found up to 70 m down-drain. The depletion of adults was far greater than that of juveniles.

At dusk one foggy evening in mid November large adults were seen leaving the drain and crawling off into the damp grass. Movement was 'brisk' and non-feeding and it

appeared to be within the snails' homoeostatic capabilities to travel some distance from the drain.

On 8 December 1979 the juvenile generation which had a mean height of 2.4 mm on 7 October 1979 now had a mean height of 8.5 mm. Snails were very rare in the marshy hollows.

Roche (1929, p 182) stated that 'all stages, from very young to adult, were found' by her at Ballymacar bridge 'in the third week of April' indicating a spring spawning in the

breeding pattern. I checked the Forth Mountain station for juveniles on 28 April 1980 and

though no juveniles were found several egg masses were seen. Egg masses were typically attached to decomposed dock leaves (Rumex sp.) on the underwater substrate. They were flattened cylinders in shape, straight or slightly curved. Four masses had mean dimensions 10 x 4 mm and mean content of twenty-two eggs. Adults were very rare. The water level

was very low after an exceptionally dry April; there was no current and great masses of feathery filamentous green alga dominated the drain vegetation.

Final Observations and Conclusions

On 18 May 19801 visited the station again to see the juveniles of the spring spawning and found the habitat destroyed. The marshy hollows had been filled, the hedges had been ripped out and an arterial drain some 3 m wide and 2 m deep gashed through the fields. No trace whatever was found of the aquatic community. The only known colony of living L.

glabra in Ireland had been wiped out and its status in Ireland is now uncertain. It appears, from the very little evidence there is of the occurrence of L. glabra in

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Ir. Nat. J. Vol. 20 No. 7 1981 287

Ireland over the past 150 years, that it is confined to the south-east of the country, the

distribution is discontinuous, but that where stations are found populations can be large. Jeffreys (1862) noted that in Britain'Although local, it is plentiful where it occurs . . . / (p 118). Habitat categories in Ireland conform with those noted in Britain (Jeffreys 1862,

Macan 1969): drainage ditches, shallow stagnant pools and marshy grounds which dry out

in summer, i.e. poor hydroseres supporting a small and little-varied molluscan fauna. Von

Siegfried (1967, p 102) gives the global habitat category as freshwater in general, without

specialisation. In Ireland the breeding pattern has included a late April and early autumn spawning;

the life span appears to be short with high fecundity and high mortality. Dispersal methods include active colonisation on damp nights and passive transport via flooding.

Voucher specimens of L. glabra found on 7 October 1979 were lodged with Dr Kerney who forwarded material to the British Museum (Nat. Hist.) Mollusca Section (Ref. No.

1979194). I also lodged specimens with the National Museum of Ireland [NMI 75. 1980

(tube of six juveniles) and NMI 76. 1980 (tube of six sub-adults)].

ACKNOWLEDGEMENTS

I am grateful to Dr M. P. Kerney, Imperial College, London for confirming the

identity of L. glabra, for his interest and for encouraging me to write this paper. I am also

grateful to him for critically reading the draft manuscript. I am indebted to Mrs Elizabeth

Platts, Queen's University, Belfast for her extensive and generous assistance in the

preparation of the final manuscript.

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