120-469: The Kerry slug or Kerry spotted slug ( Geomalacus maculosus ) is a species of terrestrial, pulmonate , gastropod mollusc . It is a medium-to-large sized, air-breathing land slug in the family of roundback slugs, Arionidae . Adult Kerry slugs generally measure 7–8 cm (2.8–3.1 in) in length; they are dark-grey or brown with yellowish spots. The internal anatomy of the slug has some unusual features and some characteristic differences from
240-423: A mutation–selection balance . It is predicted that a viral quasispecies at a low but evolutionarily neutral and highly connected (that is, flat) region in the fitness landscape will outcompete a quasispecies located at a higher but narrower fitness peak in which the surrounding mutants are unfit, "the quasispecies effect" or the "survival of the flattest". There is no suggestion that a viral quasispecies resembles
360-400: A "classical" method of determining species, such as with Linnaeus, early in evolutionary theory. However, different phenotypes are not necessarily different species (e.g. a four-winged Drosophila born to a two-winged mother is not a different species). Species named in this manner are called morphospecies . In the 1970s, Robert R. Sokal , Theodore J. Crovello and Peter Sneath proposed
480-424: A 'smallest clade' idea" (a phylogenetic species concept). Mishler and Wilkins and others concur with this approach, even though this would raise difficulties in biological nomenclature. Wilkins cited the ichthyologist Charles Tate Regan 's early 20th century remark that "a species is whatever a suitably qualified biologist chooses to call a species". Wilkins noted that the philosopher Philip Kitcher called this
600-428: A connected series of neighbouring populations, each of which can sexually interbreed with adjacent related populations, but for which there exist at least two "end" populations in the series, which are too distantly related to interbreed, though there is a potential gene flow between each "linked" population. Such non-breeding, though genetically connected, "end" populations may co-exist in the same region thus closing
720-432: A different species from its ancestors. Viruses have enormous populations, are doubtfully living since they consist of little more than a string of DNA or RNA in a protein coat, and mutate rapidly. All of these factors make conventional species concepts largely inapplicable. A viral quasispecies is a group of genotypes related by similar mutations, competing within a highly mutagenic environment, and hence governed by
840-508: A genetic boundary suitable for defining a species concept is present. DNA barcoding has been proposed as a way to distinguish species suitable even for non-specialists to use. One of the barcodes is a region of mitochondrial DNA within the gene for cytochrome c oxidase . A database, Barcode of Life Data System , contains DNA barcode sequences from over 190,000 species. However, scientists such as Rob DeSalle have expressed concern that classical taxonomy and DNA barcoding, which they consider
960-465: A lineage should be divided into multiple chronospecies , or when populations have diverged to have enough distinct character states to be described as cladistic species. Species and higher taxa were seen from the time of Aristotle until the 18th century as categories that could be arranged in a hierarchy, the great chain of being . In the 19th century, biologists grasped that species could evolve given sufficient time. Charles Darwin 's 1859 book On
1080-446: A member of the order Panpulmonata , is terrestrial; it breathes air with a lung. It is in the clade Stylommatophora , members of which have two sets of retractable tentacles , the upper pair of which have eyes on their tips. Its family is Arionidae , the round-backed slugs. The Kerry slug has no keel on its back, unlike the slugs in the families Limacidae and Milacidae . Many of its anatomical features are shared with species in
1200-492: A misnomer, need to be reconciled, as they delimit species differently. Genetic introgression mediated by endosymbionts and other vectors can further make barcodes ineffective in the identification of species. A phylogenetic or cladistic species is "the smallest aggregation of populations (sexual) or lineages (asexual) diagnosable by a unique combination of character states in comparable individuals (semaphoronts)". The empirical basis – observed character states – provides
1320-449: A particular species, including which genus (and higher taxa) it is placed in, is a hypothesis about the evolutionary relationships and distinguishability of that group of organisms. As further information comes to hand, the hypothesis may be corroborated or refuted. Sometimes, especially in the past when communication was more difficult, taxonomists working in isolation have given two distinct names to individual organisms later identified as
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#17327943225941440-400: A perfect model of life, it is still a useful tool to scientists and conservationists for studying life on Earth, regardless of the theoretical difficulties. If species were fixed and clearly distinct from one another, there would be no problem, but evolutionary processes cause species to change. This obliges taxonomists to decide, for example, when enough change has occurred to declare that
1560-945: A previously unknown population was recorded further north in County Galway . A significant proportion of the Kerry slug's range in Ireland is protected by being included in Special Areas of Conservation (SACs). In response to European environmental legislation, Ireland has designated seven SACs with the slug named as a "selection feature": 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 and Blackwater River (Kerry) . In addition, St. Gobnet's Wood SAC (which
1680-421: A range of measurements of 6–9 cm (2.4–3.5 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). The body of the Kerry slug is glossy and is covered on both sides with about 25 longitudinal rows of polygonal granulations. The slugs have two colour morphs , brown and black. In Ireland the black morph occurs in open habitats and
1800-400: A short way of saying that something applies to many species within a genus, but not to all. If scientists mean that something applies to all species within a genus, they use the genus name without the specific name or epithet. The names of genera and species are usually printed in italics . However, abbreviations such as "sp." should not be italicised. When a species' identity is not clear,
1920-416: A small, thin, shell-like plate or a collection of calcareous (chalky) granules. The Kerry slug has an internal shell or shell plate that resembles those found in land slugs of the genus Limax ; it is ovoid, solid and chalky with a transparent conchiolin (horny) base. The shell plate is usually convex above and concave beneath and has some indistinct, concentric lines of growth. According to Godwin-Austen,
2040-404: A solid plate. The circulatory and excretory systems of the Kerry slug are closely related; the heart is surrounded by the triangular kidney, which has a lamellate (layered) structure and two ureters . In this species, the ventricle of the heart is directed towards, and is very close to, the anal and respiratory openings. The ventricle of the heart is further away and further back than it
2160-404: A specialist may use "cf." before the epithet to indicate that confirmation is required. The abbreviations "nr." (near) or "aff." (affine) may be used when the identity is unclear but when the species appears to be similar to the species mentioned after. With the rise of online databases, codes have been devised to provide identifiers for species that are already defined, including: The naming of
2280-523: A species as groups of actually or potentially interbreeding natural populations, which are reproductively isolated from other such groups. It has been argued that this definition is a natural consequence of the effect of sexual reproduction on the dynamics of natural selection. Mayr's use of the adjective "potentially" has been a point of debate; some interpretations exclude unusual or artificial matings that occur only in captivity, or that involve animals capable of mating but that do not normally do so in
2400-400: A species as determined by a taxonomist. A typological species is a group of organisms in which individuals conform to certain fixed properties (a type), so that even pre-literate people often recognise the same taxon as do modern taxonomists. The clusters of variations or phenotypes within specimens (such as longer or shorter tails) would differentiate the species. This method was used as
2520-483: A species is a binomial or binomen, and comprises two Latin words, the first denoting the genus and the second denoting the species. The scientific name of a subspecies is formed slightly differently in the different nomenclature codes. In zoology, under the International Code of Zoological Nomenclature (ICZN), the scientific name of a subspecies is termed a trinomen , and comprises three words, namely
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#17327943225942640-491: A species. All species definitions assume that an organism acquires its genes from one or two parents very like the "daughter" organism, but that is not what happens in HGT. There is strong evidence of HGT between very dissimilar groups of prokaryotes , and at least occasionally between dissimilar groups of eukaryotes , including some crustaceans and echinoderms . The evolutionary biologist James Mallet concludes that there
2760-426: A species. Botanists and mycologists have the choice of ranks lower than subspecies, such as variety (varietas) or form (forma), to recognize smaller differences between populations. In biological terms, rather than in relation to nomenclature, a polytypic species has two or more genetically and phenotypically divergent subspecies, races , or more generally speaking, populations that differ from each other so that
2880-685: A species. Generally the term includes the unknown element of a distinct act of creation. Many authors have argued that a simple textbook definition, following Mayr's concept, works well for most multi-celled organisms , but breaks down in several situations: Species identification is made difficult by discordance between molecular and morphological investigations; these can be categorised as two types: (i) one morphology, multiple lineages (e.g. morphological convergence , cryptic species ) and (ii) one lineage, multiple morphologies (e.g. phenotypic plasticity , multiple life-cycle stages). In addition, horizontal gene transfer (HGT) makes it difficult to define
3000-417: A subspecies. A common criterion for recognizing two distinct populations as subspecies rather than full species is the ability of them to interbreed even if some male offspring may be sterile. In the wild, subspecies do not interbreed due to geographic isolation or sexual selection . The differences between subspecies are usually less distinct than the differences between species. The scientific name of
3120-528: A taxonomic decision at the discretion of cognizant specialists, is not governed by the Codes of Zoological or Botanical Nomenclature, in contrast to the PhyloCode , and contrary to what is done in several other fields, in which the definitions of technical terms, like geochronological units and geopolitical entities, are explicitly delimited. The nomenclatural codes that guide the naming of species, including
3240-403: A tongue. The ovispermatoduct, along which both eggs and sperm pass, is greatly twisted. This turns into the free oviduct after the vas deferens carrying the sperm branches off. The free oviduct is long and consistently thin. It opens into the atrium near the genital pore, where the muscular atrium is greatly but irregularly enlarged and connected by muscle fibres to the oviduct. The vas deferens
3360-517: A traditional biological species. The International Committee on Taxonomy of Viruses has since 1962 developed a universal taxonomic scheme for viruses; this has stabilised viral taxonomy. Most modern textbooks make use of Ernst Mayr 's 1942 definition, known as the Biological Species Concept as a basis for further discussion on the definition of species. It is also called a reproductive or isolation concept. This defines
3480-447: A variation on the morphological species concept, a phenetic species, defined as a set of organisms with a similar phenotype to each other, but a different phenotype from other sets of organisms. It differs from the morphological species concept in including a numerical measure of distance or similarity to cluster entities based on multivariate comparisons of a reasonably large number of phenotypic traits. A mate-recognition species
3600-515: A variety of reasons. Viruses are a special case, driven by a balance of mutation and selection , and can be treated as quasispecies . Biologists and taxonomists have made many attempts to define species, beginning from morphology and moving towards genetics . Early taxonomists such as Linnaeus had no option but to describe what they saw: this was later formalised as the typological or morphological species concept. Ernst Mayr emphasised reproductive isolation, but this, like other species concepts,
3720-438: Is "an entity composed of organisms which maintains its identity from other such entities through time and over space, and which has its own independent evolutionary fate and historical tendencies". This differs from the biological species concept in embodying persistence over time. Wiley and Mayden stated that they see the evolutionary species concept as "identical" to Willi Hennig 's species-as-lineages concept, and asserted that
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3840-400: Is a group of sexually reproducing organisms that recognise one another as potential mates. Expanding on this to allow for post-mating isolation, a cohesion species is the most inclusive population of individuals having the potential for phenotypic cohesion through intrinsic cohesion mechanisms; no matter whether populations can hybridise successfully, they are still distinct cohesion species if
3960-438: Is a rank below species , used for populations that live in different areas and vary in size, shape, or other physical characteristics ( morphology ), but that can successfully interbreed. Not all species have subspecies, but for those that do there must be at least two. Subspecies is abbreviated as subsp. or ssp. and the singular and plural forms are the same ("the subspecies is" or "the subspecies are"). In zoology , under
4080-458: Is a set of organisms adapted to a particular set of resources, called a niche, in the environment. According to this concept, populations form the discrete phenetic clusters that we recognise as species because the ecological and evolutionary processes controlling how resources are divided up tend to produce those clusters. A genetic species as defined by Robert Baker and Robert Bradley is a set of genetically isolated interbreeding populations. This
4200-521: Is a small, strong, ribbon-like structure that bears numerous complex rows of tiny teeth across it. In the Kerry slug, the radula is 8 mm ( 5 ⁄ 16 in) long and 2 mm ( 1 ⁄ 16 in) wide, and has 240 slightly curved, transverse 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, have one cusp and are slightly shouldered. The lateral teeth have two cusps. The admedian (next to
4320-469: Is a subspecies or a full species, the species name may be written in parentheses. Thus Larus (argentatus) smithsonianus means the American herring gull ; the notation within the parentheses means that some consider it a subspecies of a larger herring gull species and therefore call it Larus argentatus smithsonianus , while others consider it a full species and therefore call it Larus smithsonianus (and
4440-534: Is also possible in this species. Eggs are laid in clusters of 18 to 30, and are held together by a film of mucus. The egg masses are about 3.5 cm × 2 cm (1.38 by 0.79 inches). The eggs are very large compared with the size of the animal. The largest eggs are more elongate, being 8.5 mm × 4.25 mm (0.335 by 0.167 inches); the smallest are more ovoid and are 6 mm × 3 mm (0.24 in × 0.12 in). All are semi-translucent, milky-white or opalescent when fresh, although some of
4560-414: Is called speciation . Charles Darwin was the first to describe the role of natural selection in speciation in his 1859 book The Origin of Species . Speciation depends on a measure of reproductive isolation , a reduced gene flow. This occurs most easily in allopatric speciation, where populations are separated geographically and can diverge gradually as mutations accumulate. Reproductive isolation
4680-412: Is called the specific name or the specific epithet (in botanical nomenclature , also sometimes in zoological nomenclature ). For example, Boa constrictor is one of the species of the genus Boa , with constrictor being the species' epithet. While the definitions given above may seem adequate at first glance, when looked at more closely they represent problematic species concepts. For example,
4800-462: Is considered suspect. Similar distribution patterns have been observed in other species of animals and plants. This particular disjunct distribution in Iberia and Ireland with no intermediate localities is known as a " Lusitanian distribution ". There has been speculation that G. maculosus was introduced to Ireland from Iberia by prehistoric humans; a similar introduction appears to have happened with
4920-403: Is described formally, in a publication that assigns it a unique scientific name. The description typically provides means for identifying the new species, which may not be based solely on morphology (see cryptic species ), differentiating it from other previously described and related or confusable species and provides a validly published name (in botany) or an available name (in zoology) when
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5040-671: Is further weakened by the existence of microspecies , groups of organisms, including many plants, with very little genetic variability, usually forming species aggregates . For example, the dandelion Taraxacum officinale and the blackberry Rubus fruticosus are aggregates with many microspecies—perhaps 400 in the case of the blackberry and over 200 in the dandelion, complicated by hybridisation , apomixis and polyploidy , making gene flow between populations difficult to determine, and their taxonomy debatable. Species complexes occur in insects such as Heliconius butterflies, vertebrates such as Hypsiboas treefrogs, and fungi such as
5160-588: Is generally cool and damp. Because of its perceived rarity and its restricted distribution, the Kerry slug is protected under the Convention on the Conservation of European Wildlife and Natural Habitats (Bern Convention), EIS Bern Invertebrates Project. This decision was backed by studies of its distribution and ecology in Ireland, which concluded that evidence of a decline in Iberia and uncertainty over its status in Ireland tended to support its inclusion in
5280-726: Is hard or even impossible to test. Later biologists have tried to refine Mayr's definition with the recognition and cohesion concepts, among others. Many of the concepts are quite similar or overlap, so they are not easy to count: the biologist R. L. Mayden recorded about 24 concepts, and the philosopher of science John Wilkins counted 26. Wilkins further grouped the species concepts into seven basic kinds of concepts: (1) agamospecies for asexual organisms (2) biospecies for reproductively isolated sexual organisms (3) ecospecies based on ecological niches (4) evolutionary species based on lineage (5) genetic species based on gene pool (6) morphospecies based on form or phenotype and (7) taxonomic species,
5400-502: Is in species of the related genus Arion , the type-genus of the family Arionidae. The gland above the foot, the suprapedal gland , is deeply imbedded in the tissues and reaches far back. The cephalic (head) gland known as Semper's organ is well developed and shows as two strong, flattened lobes. The salivary and digestive glands are the same as those found in Arion species but the vestigial osphradium (kidney-like structure) within
5520-410: Is long, complexly twisted, and rolled in a bundle. The bursa copulatrix for digesting spermatophore and sperm—earlier literature refers to this as the spermatheca—is globular and has a short bursa duct . There is a long retractor muscle from the bursa duct, its other end is anchored near the tail of the slug at the midline. The vas deferens and the bursa duct open nearly together into the far extremity of
5640-417: Is much further north and has a considerably cooler, wetter and more humid climate, the Kerry slug is sometimes active there in the daytime if the weather is humid and overcast. The species has in unusual defensive behaviour; whereas most land slugs retract the head and contract the body but stay firmly attached to the substrate when they are attacked or threatened, the Kerry slug retracts its head, lets go of
5760-403: Is no easy way to tell whether related geographic or temporal forms belong to the same or different species. Species gaps can be verified only locally and at a point of time. One is forced to admit that Darwin's insight is correct: any local reality or integrity of species is greatly reduced over large geographic ranges and time periods. The botanist Brent Mishler argued that the species concept
5880-452: Is not considered an agricultural pest, unlike some other slugs in the family Arionidae. In Ireland, the Kerry slug occurs in woodland with oak trees, oligotrophic open moorland, blanket bogs and lake shores, especially if boulders covered with lichens and mosses are present in these habitats. Although there was a geographical association with sandstone areas, the new locality in Galway
6000-478: Is not valid, notably because gene flux decreases gradually rather than in discrete steps, which hampers objective delimitation of species. Indeed, complex and unstable patterns of gene flux have been observed in cichlid teleosts of the East African Great Lakes . Wilkins argued that "if we were being true to evolution and the consequent phylogenetic approach to taxa, we should replace it with
6120-591: Is on granite. In Iberia it usually occurs in granite mountains, and on slates, quartzite, schists, gneiss and serpentine. The best predictor of its occurrence is high rainfall and high summer temperatures. The food of Geomalacus maculosus includes lichens, liverworts , mosses, fungi ( Fistulina hepatica ) and bacteria that grow on boulders and on tree trunks. In captivity, the Kerry slug has been fed on porridge, bread, dandelion leaves, lichen Cladonia fimbriata , carrot, cabbage, cucumber and lettuce. It can be carnivorous in captivity; there are records of it consuming
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#17327943225946240-505: Is protected by conservation laws in the three countries in which it occurs. It is now known to be less dependent on sensitive, wild habitats than when these laws were introduced. Attempts have been made to establish breeding populations in captivity to ensure the survival of this slug species but these have been only partly successful. The Kerry slug is a gastropod , a class of molluscs that includes all snails and slugs, including terrestrial, freshwater and marine species. The Kerry slug,
6360-586: Is similar to Mayr's Biological Species Concept, but stresses genetic rather than reproductive isolation. In the 21st century, a genetic species could be established by comparing DNA sequences. Earlier, other methods were available, such as comparing karyotypes (sets of chromosomes ) and allozymes ( enzyme variants). An evolutionarily significant unit (ESU) or "wildlife species" is a population of organisms considered distinct for purposes of conservation. In palaeontology , with only comparative anatomy (morphology) and histology from fossils as evidence,
6480-407: Is solid, dark-brown and has about 10 broad flat ribs in the middle part of the jaw. These ribs are absent or scarcely discernible on the side areas. Where the ribs meet the upper edge, they sometimes form crenulations (a scalloped effect) and may also produce the same effect on the lower edge of the jaw. In other individuals, the ribs extend across the jaw, making both the upper and the cutting edges of
6600-449: Is sometimes an important source of genetic variation. Viruses can transfer genes between species. Bacteria can exchange plasmids with bacteria of other species, including some apparently distantly related ones in different phylogenetic domains , making analysis of their relationships difficult, and weakening the concept of a bacterial species. Nominate subspecies In biological classification , subspecies ( pl. : subspecies)
6720-594: Is threatened by hybridisation, but this can be selected against once a pair of populations have incompatible alleles of the same gene, as described in the Bateson–Dobzhansky–Muller model . A different mechanism, phyletic speciation, involves one lineage gradually changing over time into a new and distinct form (a chronospecies ), without increasing the number of resultant species. Horizontal gene transfer between organisms of different species, either through hybridisation , antigenic shift , or reassortment ,
6840-586: The Eurasian pygmy shrew . In support of such an origin or of a more recent human-mediated introduction, the genetic diversity of the Kerry slug in Ireland was found to be greatly reduced compared with that of the Iberian populations. Within Ireland, the Kerry slug is known to occur in areas with sandstone geology in West Cork and County Kerry , an area of around 5,800 km (2,200 sq mi). In 2010,
6960-530: The ICZN for animals and the ICN for plants, do not make rules for defining the boundaries of the species. Research can change the boundaries, also known as circumscription, based on new evidence. Species may then need to be distinguished by the boundary definitions used, and in such cases the names may be qualified with sensu stricto ("in the narrow sense") to denote usage in the exact meaning given by an author such as
7080-559: The International Code of Zoological Nomenclature , the subspecies is the only taxonomic rank below that of species that can receive a name. In botany and mycology , under the International Code of Nomenclature for algae, fungi, and plants , other infraspecific ranks , such as variety , may be named. In bacteriology and virology , under standard bacterial nomenclature and virus nomenclature , there are recommendations but not strict requirements for recognizing other important infraspecific ranks. A taxonomist decides whether to recognize
7200-678: The Peneda-Gerês National Park . In Spain, the distribution of this species includes coastal locations in Galicia and extends through the Cantabrian Mountains as far east as Mount Ganekogorta in the Basque Country . These localities fall within the boundaries of various autonomous communities : Galicia, Asturias , Cantabria , Castile and León (provinces of León , Palencia and Zamora ), and
7320-399: The fly agaric . Natural hybridisation presents a challenge to the concept of a reproductively isolated species, as fertile hybrids permit gene flow between two populations. For example, the carrion crow Corvus corone and the hooded crow Corvus cornix appear and are classified as separate species, yet they can hybridise where their geographical ranges overlap. A ring species is
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#17327943225947440-507: The jaguar ( Panthera onca ) of Latin America or the leopard ( Panthera pardus ) of Africa and Asia. In contrast, the scientific names of species are chosen to be unique and universal (except for some inter-code homonyms ); they are in two parts used together : the genus as in Puma , and the specific epithet as in concolor . A species is given a taxonomic name when a type specimen
7560-600: The type specimens that were used for the formal scientific description were collected. In 1842, a Dublin-based naturalist William Andrews (1802–1880) sent specimens he had found at Caragh Lake in County Kerry to the Irish biologist George James Allman . The next year, Allman exhibited them at the Dublin Natural History Society and published a formal description of the new species and genus in
7680-406: The "cynical species concept", and arguing that far from being cynical, it usefully leads to an empirical taxonomy for any given group, based on taxonomists' experience. Other biologists have gone further and argued that we should abandon species entirely, and refer to the "Least Inclusive Taxonomic Units" (LITUs), a view that would be coherent with current evolutionary theory. The species concept
7800-456: The "vagina"—has "a curious arrangement" of flattened folds. The central part, situated close to the genital pore, has a pointed end. He compared this to the calcareous darts in other genera; on the preceding pages he had described such structures in the Asian slug genus Anadenus ). The radula , which is located inside the mouth, is a feeding structure that is unique to molluscs. Typically, it
7920-728: The Basque Country provinces of Biscay and Álava . There have been unconfirmed findings of this slug from Navarra . Natura 2000 sites for this species in Spain include 48 localities (listed below, grouped by region). As at 2017, some of these sites have yet to be designated as Special Areas of Conservation: The Kerry slug is primarily nocturnal . During daylight hours, the slug usually hides in crevices of rocks and under loose bark on trees. In Iberia, juvenile Kerry slugs become active during twilight and adults become active at night, especially on rainy or very humid nights. Because Ireland
8040-587: The IUCN criteria is vulnerable. Species A species ( pl. : species) is a population of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring , typically by sexual reproduction . It is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity . Other ways of defining species include their karyotype , DNA sequence, morphology , behaviour, or ecological niche . In addition, paleontologists use
8160-499: The London literary magazine The Athenaeum . The full scientific name, including the taxonomic authority , is Geomalacus maculosus Allman, 1843. The synonyms are other binomial names that were given over time to this taxon by authors who were unaware that the specimens they were describing belonged to a species already described by Allman. The species' binomial name is sometimes written as Geomalacus (Geomalacus) maculosus because
8280-626: The Origin of Species explained how species could arise by natural selection . That understanding was greatly extended in the 20th century through genetics and population ecology . Genetic variability arises from mutations and recombination , while organisms themselves are mobile, leading to geographical isolation and genetic drift with varying selection pressures . Genes can sometimes be exchanged between species by horizontal gene transfer ; new species can arise rapidly through hybridisation and polyploidy ; and species may become extinct for
8400-405: The abbreviation "sp." in the singular or "spp." (standing for species pluralis , Latin for "multiple species") in the plural in place of the specific name or epithet (e.g. Canis sp.). This commonly occurs when authors are confident that some individuals belong to a particular genus but are not sure to which exact species they belong, as is common in paleontology . Authors may also use "spp." as
8520-570: The amount of hybridisation is insufficient to completely mix their respective gene pools . A further development of the recognition concept is provided by the biosemiotic concept of species. In microbiology , genes can move freely even between distantly related bacteria, possibly extending to the whole bacterial domain. As a rule of thumb, microbiologists have assumed that members of Bacteria or Archaea with 16S ribosomal RNA gene sequences more similar than 97% to each other need to be checked by DNA–DNA hybridisation to decide if they belong to
8640-467: The atrium, the duct into which both the male and the female systems open and which connects to the outside via the genital pore. A special feature of the genus Geomalacus , is the extremely elongated atrium. The elongated portion of the atrium further from the genital pore than the insertion of the oviduct is termed the atrial diverticulum. In Geomalacus , the penis and its penial retractor muscle have been lost. The atrial diverticulum has been proposed to be
8760-453: The binomen followed by the name of the subspecies. For example, the binomen for the leopard is Panthera pardus . The trinomen Panthera pardus fusca denotes a subspecies, the Indian leopard . All components of the trinomen are written in italics. In botany , subspecies is one of many ranks below that of species, such as variety , subvariety , form , and subform. To identify the rank,
8880-474: The biological species concept, "the several versions" of the phylogenetic species concept, and the idea that species are of the same kind as higher taxa are not suitable for biodiversity studies (with the intention of estimating the number of species accurately). They further suggested that the concept works for both asexual and sexually-reproducing species. A version of the concept is Kevin de Queiroz 's "General Lineage Concept of Species". An ecological species
9000-505: The biological species concept, a cladistic species does not rely on reproductive isolation – its criteria are independent of processes that are integral in other concepts. Therefore, it applies to asexual lineages. However, it does not always provide clear cut and intuitively satisfying boundaries between taxa, and may require multiple sources of evidence, such as more than one polymorphic locus, to give plausible results. An evolutionary species, suggested by George Gaylord Simpson in 1951,
9120-457: The body. The front of the shield is rounded and its rear is bluntly pointed. The surface texture of this area resembles the underside of undyed leather; it is spotted with pale, buff or light-coloured spots that are similar to those on the body but are more uniformly distributed. The foot fringe, a band of tissue around the edge of the foot, is not distinctly separated; it is very pale and somewhat expanded and has indistinct lines on it. The sole of
9240-428: The boundaries between closely related species become unclear with hybridisation , in a species complex of hundreds of similar microspecies , and in a ring species . Also, among organisms that reproduce only asexually , the concept of a reproductive species breaks down, and each clone is potentially a microspecies. Although none of these are entirely satisfactory definitions, and while the concept of species may not be
9360-439: The brown morph occurs in woodland; this correlates with the colours of the surroundings, suggesting camouflage. Experiments indicate the dark colouration is induced by exposure to light as the slug develops. There is also variation in banding; on each side of the body there can be two bands: one band just below the summit of the back and the other band further down the side of the body. When these bands are present they usually extend
9480-433: The concept of a chronospecies can be applied. During anagenesis (evolution, not necessarily involving branching), some palaeontologists seek to identify a sequence of species, each one derived from the phyletically extinct one before through continuous, slow and more or less uniform change. In such a time sequence, some palaeontologists assess how much change is required for a morphologically distinct form to be considered
9600-416: The concept of the chronospecies since fossil reproduction cannot be examined. The most recent rigorous estimate for the total number of species of eukaryotes is between 8 and 8.7 million. About 14% of these had been described by 2011. All species (except viruses ) are given a two-part name , called a "binomial". The first part of a binomial is the genus to which the species belongs. The second part
9720-610: The convention. Since 2006, Geomalacus maculosus has been considered a least concern species in the IUCN Red List ; between 1994 and 2006, however, the slug was rated as vulnerable . Geomalacus maculosus is also protected by the European Union's Habitats Directive and has been listed as an Annex II and Annex IV species since 1992. The principal mechanisms used by the Directive to protect habitats and species are
9840-675: The creation of Special Areas of Conservation (SACs) and the protection of species independently of their habitats by other means. Seven SACs have been designated for this species in Ireland and 49 SCIs in Spain. Threats to the Kerry slug will probably be greatest in areas not specifically protected as SACs. The Habitats Directive protects the Kerry slug outside the SACs by Article 12 (1), which obliges European Union member states to: Conservation status reports from Portugal and Spain were not yet available in August 2009. Its conservation status in Spain for
9960-426: The depiction by Godwin-Austen (1882) to be the most accurate of those by earlier authors; others depicted the atrium too short. The ovotestis —a combination of ovary and testis—is small, compact and darkly pigmented. The hermaphroditic duct, where sperm is stored, is long and convoluted, and ends in a small, spherical, seminal vesicle. The albumen gland, which produces albumen for the eggs, is elongated and shaped like
10080-509: The distribution is centred on the north-western parts of the Iberian peninsula . The Kerry slug has been known in northern Spain since 1868 and in northern Portugal since 1873. The southernmost locality where this species is found is the mountain range Serra da Estrela in Portugal. It is also found in the provinces Beira Alta , Douro Litoral , Minho , Trás-os-Montes e Alto Douro and in
10200-409: The ectocone gradually grows in size and importance as the margin is approached while the mesocone becomes almost correspondingly diminished. The outermost teeth show a more embryonic character. The jaw of the Kerry slug is about 1 mm ( 1 ⁄ 32 in) from side to side and is distinctly arched from front to rear, crescent-shaped and very wide with broad and slightly rounded ends. The jaw
10320-435: The evidence to support hypotheses about evolutionarily divergent lineages that have maintained their hereditary integrity through time and space. Molecular markers may be used to determine diagnostic genetic differences in the nuclear or mitochondrial DNA of various species. For example, in a study done on fungi , studying the nucleotide characters using cladistic species produced the most accurate results in recognising
10440-460: The exterior of the shell plate is covered with a thin, transparent protein layer called the periostracum and with the nucleus—the first part to form—situated near the front. In young Kerry slugs the shell is very thin and convex, abruptly cut off behind, and with an extremely thin layer that projects in front and contains minute granules. Authors have differed in their depictions of the Kerry slug's shell plate but they are consistent in showing it as
10560-651: The eye-spot 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 furcate (split) where it attaches to the back of the buccal bulb (mouth bulb); its other end is anchored on the right side of the body, just behind the site of attachment of the right tentacular muscle. The Kerry slug is a hermaphrodite , as are all pulmonates. Various authors have depicted its reproductive system : Godwin-Austen (1882), Sharff (1891), Simroth (1891, 1894), Taylor (1907), Germain (1930), Quick (1960) and Platts & Speight (1988). Platts & Speight considered
10680-600: The foot is pale grey-yellow and is divided into three indistinct bands; the mid-area is somewhat darker and more transparent than the side bands. There is a caudal mucous pit situated between the foot and the body on the upper surface of the tip of the tail. The pit, which collects extra mucus, is not conspicuous, triangular and opens transversely. The mucous pit often carries a transparent, yellowish ball of mucus. The Kerry slug's upper tentacles are smoky-black or grey, short and thick with oval ends, and have eye spots at their tips. The genital pore or opening lies behind and below
10800-462: The functional equivalent, homoplasy ) of a penis, acting as a copulatory organ. It is presumed that the bursa retractor muscle retracts the atrial diverticulum. In Geomalacus maculosus , the atrial diverticulum is longer than the bursa duct; this situation is reversed in Geomalacus anguiformis . Godwin-Austen noted that the part of the atrium just inside the genital pore—he called this region
10920-446: The genus Arion , also part of Arionidae. The Kerry slug was described in 1843—later than many other relatively large land gastropods present in Ireland and Great Britain—an indication of its restricted distribution and secretive habits. Although the distribution of this slug species includes south-western Ireland —including County Kerry —the species is more widespread in north-western Spain and central-to-northern Portugal. Given that
11040-533: The genus Arion , which is a more species-rich and widely distributed group of slugs within Arionidae. The Kerry slug is placed in the genus Geomalacus , which means "earth mollusc". The Kerry slug's scientific name is Geomalacus maculosus , where maculosus means "spotted" from the Latin word macula , a spot. The English-language common name is derived from County Kerry in the south-west of Ireland, where
11160-670: 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; three species comprise Arrudia . The Kerry slug has been included in molecular phylogenetics studies since 2001. The body length of adult Kerry slugs is 7–8 cm (2.8–3.1 in). These slugs are difficult to measure accurately because of their unusual startle response . Kerry slugs can also elongate themselves within crevices up to 12 cm (4.7 in). Official measurements of this species vary; Kerney et al. (1983) give
11280-556: The jaw clearly toothed in outline. In the Kerry slug, as in all species within the family Arionidae, the alimentary canal of the digestive system forms two loops. The Kerry slug has a discontinuous or disjunct distribution ; it is found only in Ireland —mostly the south-western corner— in north-western Spain , and central-to-northern Portugal . It was once reported as occurring in France but this has not been confirmed and that record
11400-417: The larger and more elongate eggs have a semi-transparent area at the smaller end. The opalescent lustre disappears in a few days and the eggs turn yellowish and later brown or black. The young appear to hatch in six to eight weeks, at this stage the spots on the body are barely present. The lateral bands are distinct and black, and are more conspicuous than they are in mature slugs of this species. In juveniles
11520-467: The mantle chamber is more distinct than it is in Arion species. In the Kerry slug, the cephalic retractors (muscles for pulling in the head) are very similar to those in Arion species. The right and left tentacular muscles, which pull 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, which have eye spots—are darkly pigmented. The right and left muscles that pull in
11640-422: The middle) teeth are larger than the median row and the mesocone—an extra protrusion in the middle of the tooth—is well developed. The only difference between the lateral and marginal series is 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 20th row on the radula. In the marginal series, however,
11760-483: The numerous fungi species of all the concepts studied. Versions of the phylogenetic species concept that emphasise monophyly or diagnosability may lead to splitting of existing species, for example in Bovidae , by recognising old subspecies as species, despite the fact that there are no reproductive barriers, and populations may intergrade morphologically. Others have called this approach taxonomic inflation , diluting
11880-525: The paper is accepted for publication. The type material is usually held in a permanent repository, often the research collection of a major museum or university, that allows independent verification and the means to compare specimens. Describers of new species are asked to choose names that, in the words of the International Code of Zoological Nomenclature , are "appropriate, compact, euphonious, memorable, and do not cause offence". Books and articles sometimes intentionally do not identify species fully, using
12000-674: The person who named the species, while the antonym sensu lato ("in the broad sense") denotes a wider usage, for instance including other subspecies. Other abbreviations such as "auct." ("author"), and qualifiers such as "non" ("not") may be used to further clarify the sense in which the specified authors delineated or described the species. Species are subject to change, whether by evolving into new species, exchanging genes with other species, merging with other species or by becoming extinct. The evolutionary process by which biological populations of sexually-reproducing organisms evolve to become distinct or reproductively isolated as species
12120-467: The rank of variety are taken to be names of subspecies (see International Code of Nomenclature of Prokaryotes ). As in botany, subspecies is conventionally abbreviated as "subsp.", and is used in the scientific name: Bacillus subtilis subsp. spizizenii . In zoological nomenclature , when a species is split into subspecies, the originally described population is retained as the "nominotypical subspecies" or "nominate subspecies", which repeats
12240-487: The result of misclassification leading to questions on whether there really are any ring species. The commonly used names for kinds of organisms are often ambiguous: "cat" could mean the domestic cat, Felis catus , or the cat family, Felidae . Another problem with common names is that they often vary from place to place, so that puma, cougar, catamount, panther, painter and mountain lion all mean Puma concolor in various parts of America, while "panther" may also mean
12360-404: The right eye tentacle. The lower tentacles are pale-grey and translucent. The skin mucus is usually pale yellow and varies in viscosity. The locomotory mucus is tenacious and usually colourless but is sometimes yellow because of mixing with body slime. Within the mantle, most land slugs have the remnants of what was in the evolutionary past a larger, external shell . Usually this remnant is either
12480-586: The ring. Ring species thus present a difficulty for any species concept that relies on reproductive isolation. However, ring species are at best rare. Proposed examples include the herring gull – lesser black-backed gull complex around the North pole, the Ensatina eschscholtzii group of 19 populations of salamanders in America, and the greenish warbler in Asia, but many so-called ring species have turned out to be
12600-418: The same name as the species. For example, Motacilla alba alba (often abbreviated M. a. alba ) is the nominotypical subspecies of the white wagtail ( Motacilla alba ). The subspecies name that repeats the species name is referred to in botanical nomenclature as the subspecies " autonym ", and the subspecific taxon as the "autonymous subspecies". When zoologists disagree over whether a certain population
12720-508: The same species. This concept was narrowed in 2006 to a similarity of 98.7%. The average nucleotide identity (ANI) method quantifies genetic distance between entire genomes , using regions of about 10,000 base pairs . With enough data from genomes of one genus, algorithms can be used to categorize species, as for Pseudomonas avellanae in 2013, and for all sequenced bacteria and archaea since 2020. Observed ANI values among sequences appear to have an "ANI gap" at 85–95%, suggesting that
12840-529: The same species. When two species names are discovered to apply to the same species, the older species name is given priority and usually retained, and the newer name considered as a junior synonym, a process called synonymy . Dividing a taxon into multiple, often new, taxa is called splitting . Taxonomists are often referred to as "lumpers" or "splitters" by their colleagues, depending on their personal approach to recognising differences or commonalities between organisms. The circumscription of taxa, considered
12960-443: The shield shows lyre-shaped markings, as is the case in slugs of the genus Arion . These lyre-shaped markings become indistinct as the slugs grow larger. The Kerry slug probably overwinters in the sexually immature stage. The bodies of preserved juvenile specimens are up to 3 cm (1.2 in) long with a mantle length of 10 mm (0.39 in). Juveniles reach maturity in two years, at a length about 2.6 cm (1.0 in). In
13080-516: The slug has thus far been recorded exclusively at locations in Ireland and north-western Iberia , it can be said to tentatively possess a Lusitanian distribution . The species appears to require environments that have high humidity, warm summer temperatures and acidic soils with no calcium carbonate . The slug is mostly nocturnal or crepuscular but in Ireland it is active on overcast days. It feeds on lichens , liverworts , mosses and fungi , which grow on boulders and tree trunks. The Kerry slug
13200-492: The slug is immune to a similar nematode, P. hermaphrodita . The most serious threat to the Kerry slug is probably the modification of habitat, which reduces its lichen and moss food sources. This can lead to the local disappearance of the species, which was documented in Spain. Other threats include intensification of land use, land reclamation , use of pesticides, overgrazing by sheep, removal of shrubs, tourism, general development pressures, planting of conifer plantations,
13320-405: The snail Vitrina pellucida . The Kerry slug mates in head-to-head position with partners' genital openings facing each other. The sexual organs, called atria—singular:atrium—are funnel-shaped with fluted edges after mating. As in Arion , sperm is transferred in a spermatophore . In the wild, eggs are laid between July and October, and from February to October in captivity. Self-fertilisation
13440-506: The species concept and making taxonomy unstable. Yet others defend this approach, considering "taxonomic inflation" pejorative and labelling the opposing view as "taxonomic conservatism"; claiming it is politically expedient to split species and recognise smaller populations at the species level, because this means they can more easily be included as endangered in the IUCN red list and can attract conservation legislation and funding. Unlike
13560-420: The spread of invasive plants such as Rhododendron ponticum and habitat fragmentation (see also Moorkens 2006). Other potential dangers to the species are climate change and air pollution , which negatively affect the lichens eaten by the Kerry slug. Climate change will probably affect the Iberian populations more acutely because the climate there is already hot and dry relative to that of Ireland, which
13680-563: The subspecific name must be preceded by "subspecies" (which can be abbreviated to "subsp." or "ssp."), as in Schoenoplectus californicus subsp. tatora . In bacteriology , the only rank below species that is regulated explicitly by the code of nomenclature is subspecies , but infrasubspecific taxa are extremely important in bacteriology; Appendix 10 of the code lays out some recommendations that are intended to encourage uniformity in describing such taxa. Names published before 1992 in
13800-631: The substrate and rolls itself into a ball-like shape. This behaviour is unique among species in Arionidae and among slugs in Ireland. It was once thought that Geomalacus maculosus lives only in wild habitats. In the Iberian Peninsula, it occurs on tree trunks in oak ( Quercus ) and chestnut ( Castanea ) forest but it is easiest to find in synanthropic habitats such as rocky walls in oak or chestnut orchards, in ruins, near houses, churches and cemeteries. In Ireland, it also occurs in upland conifer plantations and areas of clear-fell. The Kerry slug
13920-425: The user of the notation is not taking a position). A subspecies is a taxonomic rank below species – the only such rank recognized in the zoological code, and one of three main ranks below species in the botanical code. When geographically separate populations of a species exhibit recognizable phenotypic differences, biologists may identify these as separate subspecies; a subspecies is a recognized local variant of
14040-407: The whole length of the body and are overspread by numerous, ovoid yellow spots that are distributed approximately in five longitudinal zones. Behind the animal's head is the shield-shaped outer surface of the mantle , which is about a third of the length of the body when the slug is actively crawling and thus extended; when the slug is stationary and contracted, the shield is about half the length of
14160-560: The wild, the Kerry slug can live for up to seven years but in captivity, the lifespan rarely exceeds three years. In numerous localities in Spain, very few individuals of the species were observed at any one time. Until 2014, the natural enemies of Geomalacus maculosus were not known. The Kerry slug's predators include larvae of the third instar of the fly Tetanocera elata . G. maculosus suffers parasitism by nematodes . Carnaghi et al 2017 find Phasmarhabditis californica parasitising G. maculosus in Ireland however they also find
14280-540: The wild. It is difficult to define a species in a way that applies to all organisms. The debate about species concepts is called the species problem. The problem was recognised even in 1859, when Darwin wrote in On the Origin of Species : I was much struck how entirely vague and arbitrary is the distinction between species and varieties. He went on to write: No one definition has satisfied all naturalists; yet every naturalist knows vaguely what he means when he speaks of
14400-539: Was designated in relation to other selection criteria) was expanded in 2008 to protect Cascade Wood, a small area of woodland which is inhabited by the slug. The species has also been recorded at other SACs where it is not a selection feature, for example in Derryclogher Bog, County Cork. Despite its first discovery at Caragh Lake and its English common name of Kerry slug, Ireland is at the periphery of this slug species' distribution; in terms of genetic diversity
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