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The Kerry slug or Kerry spotted slug, scientific name Geomalacus maculosus, is a rare species of medium-sized to large air-breathing land slug. It is a terrestrial pulmonate gastropod mollusc in the family Arionidae, the roundback slugs. An adult Kerry slug generally measures 7–8 cm (2.8–3.2 in) in length and is a dark grey colour with yellowish spots. The internal anatomy shows some unusual features, and some characteristic differences from the genus Arion, which is the type genus of the family. The species was described in 1843, rather late compared to many other relatively large land gastropods that form a part of the fauna of the British Isles; this is one indication of this slug's rarity and its secretive habits. The distribution of this slug species includes wild habitats in southwestern Ireland, in north-west Spain and from central to northern Portugal, but in no other countries between Ireland and Spain. The Kerry slug appears to require environments with acidic soil and high humidity. The slug is mostly nocturnal or crepuscular, although in Ireland it is active on overcast days. It eats lichens, liverworts, mosses and fungi growing on boulders and on trees. This slug species is officially protected by conservation laws that apply in the three countries in which it occurs. The survival of this species is at risk because it lives only in completely wild, unspoiled habitat of a particular type, certain acidic woodlands and moorlands that support the species of lower plants on which it relies for food. This habitat type is at risk from a number of different factors ranging from climate change to the construction of roads. Attempts have been made to establish breeding populations in captivity, but with only limited success.
[edit] TaxonomyThe Kerry slug is a gastropod, as are all other snails and slugs, whether they are marine, aquatic, or terrestrial. This is an air-breathing land slug, a pulmonate. It is in the clade Stylommatophora, which means that its primitive eyes or eye spots are carried on the tips of its two upper tentacles. It is an arionid, or round-backed slug (it has no keel on its back), and it shares numerous anatomical features with other genera in the family Arionidae, including the Arion slugs, which are most typical of that family. The Kerry slug's binomial name is Geomalacus maculosus. It is in the genus Geomalacus, which literally means "earth mollusc". Its specific name maculosus means spotted, from the Latin word macula "spot".[3] The English vernacular name is derived from County Kerry, the county in the southwest of Ireland where this species was first collected and described. The scientific name of the species is also sometimes written as Geomalacus (Geomalacus) maculosus. This is because the genus Geomalacus contains two subgenera: the nominate subgenus (subgenus of the same name) Geomalacus and a second subgenus Arrudia Pollonera, 1890. The subgenus Geomalacus contains only one species, the Kerry slug. The subgenus Arrudia includes three species. This slug species was originally described and named from specimens collected in Ireland. An Irish naturalist named William Andrews (1802–1880) sent material he had found at Caragh Lake in County Kerry to the Irish naturalist George James Allman in 1842,[2] who then introduced the slug to science as a new species. [edit] Description The body length of adults is 7–8 cm (2.8–3.2 in).[4] It is difficult to measure these slugs because of their startle behaviour (see below). Kerry slugs can also elongate themselves within crevices up to 12 cm (4.8 in).[4] Because of the variability in apparent length of individuals, "official" measurements vary, for example, Kerney et. al. (1983)[5] gives slightly different measurements for the species: 6–9 cm (2.4–3.6 in). The body of a fixed (preserved) adult specimen was 7 cm (2.8 in) long with a mantle length of 3 cm (1.2 in).[4] The body is glossy, covered on the left and right sides with about 25 longitudinal rows of polygonal granulations (very small knobs). The slugs are usually blackish or dark-grey, sometimes with indistinctly indicated darker subdorsal (just below the summit of the back) and lateral (side) bands, which usually extend the whole length of the body, being overspread by numerous, somewhat oval, yellowish spots. These spots are distributed more or less perceptibly in five longitudinal zones.[6]  The shield (the shield-shaped outer surface of the mantle) is about a third of the length of the body when crawling, but only about half of that when contracted. The shield is rounded in front and bluntly pointed behind. The surface resembles the underside of untanned leather. It is spotted with pale buff or whitish spots similar to those on the body but more uniformly distributed.[6] The foot-fringe—a band of tissue around the edge of the foot—is not very distinctly separated: it is very pale and somewhat expanded, with indistinct lines on it.[6] The sole is pale dusky-ochreous—a grey yellow in colour—and is divided into three indistinct bands, with the mid-area somewhat darker and more transparent than the sides.[6] The caudal mucous pit on the upper surface of the tip of the tail is triangular, not very conspicuous, and opens transversely between the foot and the body. The mucous pit often carries a transparent yellowish ball of slime (mucus).[6] The upper tentacles are smoky-black or grey, short and thick, but with oval ends, and having the usual eye spots at their tips. The genital pore (or opening) lies close to the tentacles.[7] The lower tentacles are pale translucent grey.[6] The dermal-mucus (skin mucus) is usually pale-yellow and variable in its degree of viscosity. The locomotory-mucus (mucus for crawling on) is tenacious and usually colourless, but may be stained by having mixed with the body slime.[6] [edit] Internal anatomy Most land slugs have, within the mantle, the remnants of what was once (in the evolutionary past), a larger external shell, and this exists either in the form of an internal shell (a thin shelly plate), or a collection of shelly granules. In this species there is an internal shell or shell plate which resembles that found in land slugs of the genus Limax. In other words the shell plate is oval in shape, solid and calcareous (chalky), with a transparent conchiolin (horny) base. It is usually somewhat convex above and concave beneath, with a few indistinct concentric lines of growth, and covered outwardly with a very thin transparent epidermis (protein layer), and with the nucleus (the oldest growth part) near the front. In young animals, the shell is very thin and convex, abruptly cut off behind, but with an extremely thin layer that projects in front and contains minute granules.[6] The circulatory and excretory system are closely related, in that the heart is surrounded by the triangular kidney. The kidney has a lamellate (layered) structure and it has two ureters. In this slug species, the ventricle of the heart is directed towards, and is very close to, the anal and respiratory openings, whereas the ventricle of the heart is further away and in a further back position than it is in species of the related genus Arion.[6]  The suprapedal gland is deeply imbedded in the tissues, and reaches far back. The cephalic (head) gland known as the Semper's organ is well developed, and chiefly shown as a pair of strong flattened lobes. The salivary and digestive glands show no differences from that of Arion species, but the vestigial osphradium (kidney-like structure) within the mantle chamber is more distinct than it is in Arion species.[6] As for the muscles of the slug, the cephalic retractors (muscles for pulling in the head) are very much the same as they are in Arion species. The right and left tentacular muscles (for pulling in all four of the tentacles) divide early for the upper and lower tentacles, but only the muscles of the ommatophores (the two upper tentacles that have eye spots) are darkly pigmented. The right and left muscles that pull in the eyespot tentacles are attached at the base to the back edge of the mantle on the right and left respectively. The pharyngeal (throat) retractor muscle is, as usual, furcate (split) for attachment to the back of the buccal bulb (mouth bulb), and the root of this muscle is fixed on the right side of the body, just behind where the right tentacular muscle is attached.[6]  Before the reproductive system is described, it first needs to be pointed that all pulmonate land snails and slugs are hermaphrodites, each one having a full set of elaborate and unfamiliar male and female organs, and because of this, the reproductive system in all of these animals is complex and very hard to understand. The Kerry slug's reproductive organs are as follows: there is a small, compact, and darkly pigmented ovotestis (a combination of ovary and testis). There is a hermaphroditic duct (male and female duct) which is very long and greatly convoluted, and ends in a small spherical vesicula seminalis (seminal vesicle). The albumen gland (which creates albumen for the eggs) is elongated and shaped like a tongue. The ovispermatoduct (a duct that carries both eggs and sperm) is very much twisted. The free oviduct (duct that carries eggs only) is rather long and thin, but without any enlargement. The vas deferens (carries sperm) is very long, complexly twisted, and rolled up in the form of a bundle. The spermatheca (for storing sperm) is globular, with a short stem, but is quite distant from the genital pore (where the whole elaborate system opens to the outside world). The spermatheca is distant from this opening because of the remarkable elongation of the atrium or vestibule (a common area which is usually just inside the genital pore, the atrium is an area where both the male and the female systems open). There is a long retractor muscle from the vesicle, and its stem is fixed internally to the back of the slug in the median line (midline of the body) near the caudal end (tail end) of the body. The vas deferens and the spermatheca open nearly together into the far extremity of the atrium, which is prolonged in an attenuate form (drawn out in length) to an enormous extent. The very thin free oviduct (egg-carrying duct) opens into the atrium much nearer the near end, where the muscular vestibule is greatly but irregularly enlarged, and connected to the oviduct by a number of muscular fibres. Within the vagina (the female organ which receives the penis during copulation) there is a curious series of flattened folds, the central part has a pointed end which is situated close to the genital pore, and this pointed end may possibly be a sarcobelum (a very much reduced version of an organ that makes love darts) and thus may be the homologue (a similar structure because of shared ancestry) of the love dart in the Helicidae.[6] The radula is a small but strong ribbon-like structure with numerous complex rows of tiny teeth. A radula is found only in molluscs. In this species of slug the radula is 8 mm (5/16 in) long and 2 mm (1/16 in) wide, and has 240 slightly curved transverse (crosswise) rows of denticles (tiny teeth). Each row of teeth is composed of one median tooth and 10 lateral and marginal teeth on each side. The median teeth are small, and are clearly unicuspid (having one cusp), though they are slightly shouldered. The lateral teeth are bicuspid (having two cusps) but the admedian (next to the middle) teeth are noticeably larger than the median row, and the mesocone (an extra protrusion in the middle of the tooth) is well developed. There is however, no distinction between the lateral and marginal series except that the ectocone (extra little side protrusion) present on the admedian teeth recedes in position and slightly diminishes in size in the succeeding teeth up to about the twentieth row on the radula, but in the marginal series, the ectocone gradually grows in size and importance as the margin is approached, while the mesocone becomes almost correspondingly diminished, the outermost teeth showing a more embryonic (more like that of an embryo) character.[6]   The jaw measures about 1 mm (1/32 in) from side to side, and is distinctly arcuate (arched) from front to rear, lunate (crescent-moon shaped) in shape, but very wide, with broad and slightly rounded ends. The jaw is solid, dark-brown and has about 10 broad flat ribs only in the middle part of the jaw. These ribs are absent or scarcely discernible on the side areas. The ribs sometimes crenulate the upper edge (making that edge have small rounded teeth) and sometimes do the same thing to the lower edge of the jaw, or the ribs may extend all the way across the jaw and make both the upper and the cutting edges of the jaw denticulate (toothed in outline).[6] The alimentary canal of the digestive system is similar to that of the genus Arion.[6] [edit] Distribution Geomalacus maculosus has what is known as a disjunct distribution (in other words, it occurs in discontinuous locations). The distribution is limited to southwestern Ireland, north-west Spain, and from central Portugal to northern Portugal.[8] The occurrence of this slug in southwest Ireland seems out-of-place, but has been observed in a few other species of organism; this type of disjunct distribution in Iberia and in Ireland without any intermediate localities is called "Lusitanian". Within Ireland, the slug is known from sandstone geology areas in West Cork and County Kerry,[9] a total area of around 5,800 km2 (2,239.4 square miles).[4] Special Areas of Conservation (SACs) for this species in Ireland include 7 areas:[10] Glengarriff Harbour and Woodland; Caha Mountains; Sheep's Head; Killarney National Park, Macgillycuddy's Reeks and Caragh River Catchment; Lough Yganavan and Lough Nambrackdarrig; Cloonee and Inchiquin Loughs, Uragh Wood; Blackwater River in County Kerry. Despite its first "discovery" at Caragh Lake, and its English common name of "Kerry slug", Ireland is not at the centre of this slug species' distribution; instead the distribution of this species is centred in continental Iberia.[11] This slug has been known from northern Spain since 1868, and from northern Portugal since 1873.[9] It was once reported as occurring in France, but this was never confirmed, and so that record is considered suspect.[9] The southernmost locality where it is found is the mountain range Serra da Estrela in Portugal. Other Portuguese localities include the provinces Beira Alta, Douro Litoral, Minho, Trás-os-Montes e Alto Douro and Peneda-Gerês National Park, a protected area.[8][12] Its distribution in Spain includes coastal locations in Galicia, and extends through the Cantabrian Mountains as far east as Mount Ganekogorta in the Basque Country. The localities in question fall within the boundaries of various autonomous communities: Galicia, Asturias, Cantabria, Castile and León (provinces of León and Palencia), and the Basque Country (provinces of Biscay and Álava).[8][12] There have been unconfirmed findings reported from Navarra.[12] Special Areas of Conservation (SACs) for this species in Spain include 49 areas:[10]
Upper valleys of the Nansa and Saja and Alto Campoo;
Lake Sanabria and its vicinities; Natural Park of Fuentes Carrionas and Fuente Cobre-Montaña Palentina;
Anllóns river; Baixa Limia; Carballido (A Fonsagrada, province of Lugo); Carnota— Monte Pindo;Cíes Islands; Costa Ártabra; Costa da Morte - two areas, Costa da Morte and Costa da Morte (Northern); Encoro de Abegondo—Cecebre; Eo river (included among the Galician sites although the estuary forms the boundary with Asturias); Costa de Ferrolterra—Valdoviño; Fragas do Eume; Macizo Central, Ourense (province); Monte Aloia; Negueira; Serra do Cando; Sil river canyon; Tambre - two areas, the river and its estuary;
Picos de Europa - two areas dividing the Picos de Europa mountain range and the corresponding National Park between on the one hand Castile and León and on the other Asturias;
Liébana; Liebana; Ancares; Baixa Limia—Serra do Xurés; Ancares—Courel; A Marronda; Cruzul—Agüeira; Monte Maior; Serra do Xistral; Bidueiral de Montederramo; Pena Veidosa; Tâmega river; Ulla river system—Deza; Baixo Minho; Serra de Candán; Sobreirais do Arnego; Camesa river; Sierra de los Ancares; Montes Aquilanos; Montes Aquilanos y Sierra de Teleno; Sierra de la Cabrera; Hoces de Vegacervera; Pena Trevinca.  [edit] BehaviourThis slug is primarily nocturnal, and so during the daylight hours it usually lies hidden in crevices of rocks and under loose bark on trees.[13] In Iberia, juveniles become active during twilight, and adults become active at night, especially on rainy or very humid nights.[4][8][13] In Ireland, which is considerably further north, the temperatures are cooler, there is more rain, and the air is often quite damp, and therefore in Ireland this slug is active in the daytime when the weather is suitably humid and overcast.[14] This species has a very unusual defensive behaviour. When they are attacked, most land slugs will simply retract the head and contract the body a little, but they stay attached to the substrate. In contrast, when this slug is threatened, it retracts its head, lets go of the substrate, rolls up completely, and stays contracted in a ball-like shape.[4] This is a unique feature among all the Arionidae,[5] and among all slugs in Ireland[4]. [edit] Ecology
[edit] HabitatGeomalacus maculosus lives only in wild habitats[9] and thus it is never an agricultural pest,[9] unlike some other slugs in the family Arionidae. In Ireland this slug inhabits wild woodland with oak trees, and oligotrophic open moorlands, as long as there are boulders covered with lichens and mosses in these habitats.[9] In Spain it usually occurs in granite mountains.[13] The Kerry slug usually prefers acidic soil and high humidity environments, living on moss and lichen-covered rocks and trees (mainly the chestnut Castanea sativa and some species of oak). It may also occur in open areas, such as hydrophilic pastures near oligotrophic water bodies.[8] [edit] FeedingThe food of Geomalacus maculosus includes lichens, liverworts, mosses, fungi and bacteria growing on boulders and on trees.[8][9][15] In captivity, this species has been fed on porridge, bread, dandelion leaves, lichen Cladonia fimbriata and various vegetables (carrot, cabbage, cucumber, lettuce).[4][6] It can be also carnivorous in captivity and has been documented as devouring the snail Vitrina pellucida.[6] [edit] Life cycle The mating of this species is described in Platts & Speight (1988).[14] Eggs are laid in July to October in the wild,[4] and from February to October in captivity.[15] Self-fertilisation is also possible in this species.[4] The eggs are laid in clusters of 18 to 30,[4] and held together by a film of mucus. The egg masses are about 3.5 x 2 cm in overall size.[15] The eggs are very large compared with the size of the animal, but vary within certain limits. The largest eggs are more elongate, being 8.5 × 4.25 mm; the smallest eggs are more regularly oval, and are only 6 × 3 mm. All are semitranslucent milky-white or opalescent when fresh,[16] although some of the larger and more elongate ones show a somewhat transparent area at the smaller end. The opalescent lustre becomes lost in a few days, and the eggs turn yellowish, and later brown,[6] or black.[15] The young appear to hatch in from 6[15] to 8 weeks, at which period the spots are barely present, but the lateral bands are distinct and black, and the shield shows lyre-shaped markings, as in slugs of the genus Arion, but these become indistinct as growth proceeds. They probably pass the winter in the immature stage, and when immature their bodies show lateral banding which is much more conspicuous than it is in mature slugs of this species.[6] The body of fixed juvenile specimens is up to 3 cm (1.2 in) long with a mantle length of 10 mm.[4] Juveniles reach maturity in 2 years, at a length about 2.6 cm.[4][15] The life span of Geomalacus maculosus is up to seven years,[4] but the lifespan in captivity is rarely over three years.[15] In numerous different localities in Spain, it was consistently the case that no more than a very few individuals of the species were observed.[13] [edit] Threats The most serious threat to the species include modification of the habitat, which reduce its lichen and moss food sources.[9] This can lead to the local disappearance of the species, which was documented in Spain.[9][13] Other threats include: intensification of land use (land reclamation, using of pesticides, overgrazing by sheep, removing of shrubs, building gardens, burning, and building roads and highways), tourism, general development pressure, coniferous forest plantations, the spread of invasive species of plants such as Rhododendron ponticum and habitat fragmentation[9][17] (see also Moorkens 2006). Potential dangers to the species include climate change and air pollution, because these negatively affect the lichens which are a food source for the slug. Climate change will probably affect the Iberian populations more seriously, because the climate there is already on the hot and dry side relative to Ireland, which is generally rather cool and damp.[9] [edit] ConservationBecause of its perceived rarity and restricted distribution, Geomalacus maculosus is protected under the Convention on the Conservation of European Wildlife and Natural Habitats (Bern Convention), EIS Bern Invertebrates Project. This was backed by studies of its distribution and ecology in Ireland[14] which concluded that evidence of a decline in Iberia plus uncertainty over its status in Ireland supported its inclusion in the Convention. Platts and Speight noted in 1988 that it occurs in only three protected sites in Ireland: Glengariff Forest, West Cork; Uragh Wood Nature Reserve, South Kerry; and Killarney National Park, North Kerry. They concluded that the species could not be adequately safeguarded with only three sites, and therefore supported its inclusion in the Bern list, to which the Irish government is a signatory.[14] Since 2006, Geomalacus maculosus has been considered as least concern species in the IUCN Red List,[1] however during 1994 to 2006 it was considered to be vulnerable.[9] It has been protected by the Irish Wildlife Act of 1976 since 1990, as it was added by regulation SI 112/1990.[18] This is the only gastropod protected by this regulation in Ireland. Geomalacus maculosus is protected by the European Union's Habitats Directive and is listed as an Annex II and Annex IV species since 1992.[18] Seven Special Areas of Conservation (SACs) have been designated for this species in Ireland and 49 in Spain.[10] The Species Action Plan for this species for Ireland was published in January 2008.[9] Its conservation status in Ireland in 1988–2007 is favourable (FV) in all evaluated criteria (range, population, habitat and future prospects) in the report for the European Commission in accordance with the Habitats Directive.[4][17] Conservation status reports from Portugal and from Spain are not available yet in August 2009.[19] Its conservation status in Spain for the IUCN criteria is vulnerable.[12] The species has been successfully bred in captivity in terraria in the "Endangered Species Breeding Unit" in the WWT Martin Mere centre since 1990. This is a project of the conservation organisation Wildfowl and Wetlands Trust located in Martin Mere, England.[15] Slugs from the breeding program were given out to a number of different zoos and individuals during the 1990s, but unfortunately only a very few of these breeding groups survived.[15] [edit] ReferencesThis article incorporates public domain text from Taylor (1907).[6]
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