''Geophilus hadesi'' is a

species A species () is often defined as the largest group 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 Taxonomy (biology), ...

of soil centipede in the

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

Geophilidae Geophilidae is a family of soil centipedes in the superfamily Geophiloidea and the order Geophilomorpha. In 2014, a phylogenetic analysis based on morphological and molecular data found this family to be polyphyletic. To avoid this polyphyly, ...

. This

centipede Centipedes (from Neo-Latin , "hundred", and Latin , "foot") are predatory arthropods belonging to the class Chilopoda (Ancient Greek , ''kheilos'', "lip", and Neo-Latin suffix , "foot", describing the forcipules) of the subphylum Myriapoda, ...

is a

troglobite A troglobite (or, formally, troglobiont) is an animal species, or population of a species, strictly bound to underground habitats, such as caves. These are separate from species that mainly live in above-ground habitats but are also able to live u ...

, spending its entire life cycle in a cave environment. This species and '' Geophilus persephones'' are the only two troglobites known in the order

Geophilomorpha Geophilomorpha is an order of centipedes commonly known as soil centipedes. The name "Geophilomorpha" is from Ancient Greek roots meaning "formed to love the earth." This group is the most diverse centipede order, with 230 genera. These centiped ...

. The species ''G. hadesi'' is named after

Hades Hades (; , , later ), in the ancient Greek religion and Greek mythology, mythology, is the god of the dead and the king of the Greek underworld, underworld, with which his name became synonymous. Hades was the eldest son of Cronus and Rhea ...

, god of the underworld in

Greek mythology Greek mythology is the body of myths originally told by the Ancient Greece, ancient Greeks, and a genre of ancient Greek folklore, today absorbed alongside Roman mythology into the broader designation of classical mythology. These stories conc ...

and the husband of

Persephone In ancient Greek mythology and Ancient Greek religion, religion, Persephone ( ; , classical pronunciation: ), also called Kore ( ; ) or Cora, is the daughter of Zeus and Demeter. She became the queen of the Greek underworld, underworld afte ...

, the namesake of the first troglobite discovered among the soil centipedes. The species ''G. hadesi'' has been observed in a cave as far as 1,100 meters below the surface, the deepest underground that any centipede has ever been recorded.

Discovery

This species was first described in 2015 by a team of

biologists A biologist is a scientist who conducts research in biology. Biologists are interested in studying life on Earth, whether it is an individual cell, a multicellular organism, or a community of interacting populations. They usually specialize in ...

led by the Bulgarian myriapodologist Pavel Stoev of the

National Museum of Natural History The National Museum of Natural History (NMNH) is a natural history museum administered by the Smithsonian Institution, located on the National Mall in Washington, D.C., United States. It has free admission and is open 364 days a year. With 4.4 ...

Sofia Sofia is the Capital city, capital and List of cities and towns in Bulgaria, largest city of Bulgaria. It is situated in the Sofia Valley at the foot of the Vitosha mountain, in the western part of the country. The city is built west of the Is ...

Bulgaria Bulgaria, officially the Republic of Bulgaria, is a country in Southeast Europe. It is situated on the eastern portion of the Balkans directly south of the Danube river and west of the Black Sea. Bulgaria is bordered by Greece and Turkey t ...

. The original description of this species is based on three specimens collected by biospeleologists in 2011 from three different caves in the

Velebit Velebit (; ; ) is the largest, though not the highest, mountain range in Croatia. The range forms a part of the Dinaric Alps and is located along the Adriatic coast, separating it from Lika in the interior. Velebit begins in the northwest near ...

mountains in

Croatia Croatia, officially the Republic of Croatia, is a country in Central Europe, Central and Southeast Europe, on the coast of the Adriatic Sea. It borders Slovenia to the northwest, Hungary to the northeast, Serbia to the east, Bosnia and Herze ...

. The first specimen collected, a female

holotype A holotype (Latin: ''holotypus'') is a single physical example (or illustration) of an organism used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of s ...

, was found 250 meters underground in the Munižaba cave. The second, a female

paratype In zoology and botany, a paratype is a specimen of an organism that helps define what the scientific name of a species and other taxon actually represents, but it is not the holotype (and in botany is also neither an isotype (biology), isotype ...

, was found 500 meters underground in the Muda Labudova cave. The third, a male specimen, was found 980 meters underground in the Lukina jama cave, the 15th deepest cave in the world. Another specimen was seen in the same cave at a depth of about 1,100 meters but could not be collected.

Description

Like other soil centipedes, this species is blind, has a flattened body, and is well adapted to life underground. This species also exhibits

troglomorphic Troglomorphism is the morphological adaptation of an animal to living in the constant darkness of caves, characterised by features such as loss of pigment, reduced eyesight or blindness, and frequently with attenuated bodies or appendages. The ter ...

features (reflecting adaption to life in caves), such as elongated appendages (including long antennae, walking legs, and ultimate legs), as well as elongated trunk segments and unusually long claws on its legs. The female specimens range from about 22 mm in length (in the paratype) to a maximum length of 28 mm (in the holotype); the male specimen measures 27 mm in length. Specimens of both sexes have only 33 pairs of legs. The

forcipules Forcipules are the modified, pincer-like, front legs of centipedes that are used to inject venom into prey. They are the only known examples of front legs acting as venom injectors. Nomenclature Forcipules go by a variety of names in both sci ...

feature only a single small denticle, located at the base of the ultimate article. The metasternites in the anterior part of the trunk, except for the first segment, feature pits on the anterior margin. The posterior margin of the metasternites features a field of pores, with these pore-fields forming a single transverse band on each metasternite in the anterior half of the trunk but dividing into two groups in the posterior half of the trunk. This species shares many traits with other centipedes in the

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

Geophilus ''Geophilus '' is a large, heterogeneous genus of soil centipedes in the family Geophilidae largely considered to be synonymous with '' Brachygeophilus''. The generic name first appeared in Brewster's Edinburgh Encyclopaedia in 1814 as '' Geoph ...

''. For example, each of the ultimate legs ends in a claw, and the ventral side of these legs features pores, with most of these coxal pores close to the adjacent

sternite The sternum (: sterna) is the ventral portion of a segment of an arthropod thorax or abdomen. In insects, the sterna are usually single, large sclerites, and external. However, they can sometimes be divided in two or more, in which case the su ...

. Furthermore, the coxosternite of the second

maxillae In vertebrates, the maxilla (: maxillae ) is the upper fixed (not fixed in Neopterygii) bone of the jaw formed from the fusion of two maxillary bones. In humans, the upper jaw includes the hard palate in the front of the mouth. The two maxillar ...

is entire rather than divided, and the coxosternite of the forcipular segment features incomplete chitin-lines. Moreover, as in many species in the same genus, the anterior trunk metasternites feature anterior pits and posterior pore-fields in the form of transverse bands. Two other species in the genus ''Geophilus'' resemble ''G. hadesi'' most closely: ''G. persephones'' and ''G. piae'', which share a number of distinctive traits with ''G. hadesi''. These traits include a modest number of legs: ''G. persephones'' has 29 leg pairs (in the only recorded specimen, a male), and ''G. piae'' can have as few as 35 pairs in males and 37 pairs in females. All three species also feature

sternal The sternum (: sternums or sterna) or breastbone is a long flat bone located in the central part of the chest. It connects to the ribs via cartilage and forms the front of the rib cage, thus helping to protect the heart, lungs, and major blood ve ...

pore-fields that extend to the posterior parts of the trunk. Traits shared by these three species also include second maxillae that end in a stout

tubercle In anatomy, a tubercle (literally 'small tuber', Latin for 'lump') is any round nodule, small eminence, or warty outgrowth found on external or internal organs of a plant or an animal. In plants A tubercle is generally a wart-like projectio ...

with a small tip instead of a curved article that tapers gradually. Furthermore, the species ''G. persephones'' and ''G. hadesi'' also share troglomorphic features, such as long antennae and legs. The species ''G. hadesi'', however, is larger than either ''G. persephones'', which reaches only 16.2 mm in length, or ''G. piae'', which reaches only 11 mm in length. The other two species may also be distinguished from ''G. hadesi'' by the pattern of coxal pores on ventral side of the ultimate legs: In ''G. hadesi'', one pore is isolated in a distinctive position posterior to the other pores.

References

{{Taxonbar, from=Q20635184 hadesi Animals described in 2015 Myriapods of Europe Endemic fauna of Croatia Cave arthropods