Opisthocheiron canayerensis

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Opisthocheiron canayerensis
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Arthropoda
Subphylum: Myriapoda
Class: Diplopoda
Order: Chordeumatida
Family: Opisthocheiridae
Genus: Opisthocheiron
Species:
O. canayerensis
Binomial name
Opisthocheiron canayerensis
Mauriès & Goeffrey, 1982

Opisthocheiron canayerensis is a species of millipede in the family Opisthocheiridae. [1] This species is found in France, far inside deep caves. [2] This millipede is notable as one of only a few species in the order Chordeumatida with only 26 segments in adults (counting the collum as the first segment and the telson as the last), four fewer segments than typically found in adults this order. [3] [4]

Contents

Discovery and distribution

This species was first described in 1982 by the myriapodologists Jean-Paul Mauriès and Jean-Jacques Geoffroy. The original description is based on specimens collected in 1981 from the Baume Layrou cave in Trèves, in the eastern part of the Grands Causses, in the department of Gard in France. These specimens include a male holotype, eight other males, thirteen females, and two juveniles. The type specimens are deposited in the Muséum National d'Histoire Naturelle in Paris. The species is named for the Causse de Canayère, the plateau where the type specimens were found. [5] Since the discovery of this millipede, many more specimens have been collected and studied, not only from the Baume Layrou cave but also from the Cabanes du Trevezel cave and the Bramabieu cave, which are also in the Grands Causses in the department of Gard in France. [3]

Description

Unlike other species in the genus Opisthocheiron , this species lacks pigmentation, an adaptation to life in the darkness of caves. This species also has few ocelli and long legs, which are also common troglomorphic adaptations. Adult males range from 6.5 mm to 7 mm in length, and adult females range from 8 mm to 10 mm in length. [5]

This millipede is one of only a few species in the order Chordeumatida with only 26 segments in adults, the minimum number recorded in this order. [3] [4] Accordingly, the adult female of this species has only 42 pairs of legs, and the adult male has only 40 pairs of walking legs, excluding the eighth and ninth leg pairs, which become gonopods. [3] [4] This reduction in the number of segments and legs distinguishes this species from the other species in the genus Opisthocheiron, which all have the 30 segments in adults that are usually found in adults in the order Chordeumatida. [3]

This species arrives at a lower number of segments and legs through a process of post-embryonic development that deviates from the anamorphosis usually observed in the order Chordeumatida. Like other species in this order, O. canayerensis is teloanamorphic, adding segments and legs through a series of molts until the adult stage, when the molting stops and the adult emerges with a final number of segments and legs. This species, however, reaches maturity and stops molting one stage earlier, in the eighth stage rather than in a ninth stage. Furthermore, O. canayerensis conforms to the pattern usually observed in most species of Chordeumatida only through the first five stages, then adds one fewer segment than usual upon entering the sixth and seventh stages. Thus, in this process, O. canayerensis goes through stages of development with 6, 8, 11, 15, 19, 22, and 24 segments, before emerging as an adult with 26 segments in the final stage. [3] [4]

This process is the same as that observed in the species Chamaesoma broelemanni , one of the other species in the order Chordeumatida with only 26 segments in adults, but with one difference. In O. canayerensis, the transformation of legs into gonopods in the male begins in the seventh stage and continues until the eighth and final stage. In C. broelemanni, however, this process begins in the sixth stage and continues until the eighth stage. [6]

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<span class="mw-page-title-main">Polyxenida</span> Order of millipedes

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<span class="mw-page-title-main">Chordeumatida</span> Order of millipedes

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Trichopolydesmidae is a family of millipedes belonging to the order Polydesmida. This family includes two genera notable for featuring sexual dimorphism in segment number: adult females in these genera have the 20 segments usually found in this order, but adult males have only 19. This family also includes the species Deharvengius bedosae, notable for being among the very few species in this order to feature adults with only 18 segments rather than the 20 segments usually found in polydesmids.

Chordeumatidae is a family of millipedes belonging to the order Chordeumatida. These millipedes range from 7 mm to 18 mm in length and are found in Europe. Adult millipedes in this family have either 28 or 30 segments. This family features distinctive sex-linked modifications to the legs in adults: In the adult female, a legless sternite replaces the third pair of legs, and in the adult male, five pairs of legs are modified in the gonopod complex. These modifications are more extensive than those found in other adult males in this order, which often have only two leg pairs modified into gonopods. With the more extensive modifications to the legs in this family, species with the usual 30 segments feature adult females with only 49 leg pairs and adult males with only 45 pairs of walking legs, and species with only 28 segments feature adult females with only 45 leg pairs and adult males with only 41 pairs of walking legs.

Speophilosomatidae is a family of millipedes belonging to the order Chordeumatida. These millipedes are found in Japan and range from 4 mm to 6 mm in length. Adult millipedes in this family are notable for being among the few in this order with only 26 segments instead of the 30 usually found in chordeumatidans. The adult males in this family are also notable for involving three leg pairs in the gonopod complex rather than the two pairs typically modified into gonopods in this order.

Chamaesomatidae is a family of millipedes belonging to the order Chordeumatida. This family contains 28 species distributed among 11 genera. These millipedes are found in Europe and North Africa.

Hoffmaneumatidae is a family of millipedes belonging to the order Chordeumatida. This family includes two genera, one (Hoffmaneuma) found in the Russian Far East and the other (Japanoparvus) found in Japan. Millipedes in this family range from 4 mm to 6 mm in length. Adult millipedes in this family have only 28 segments, not the 30 segments usually found in this order. Adult males in this family feature a reduced leg pair 10 in addition to the two pairs normally modified into gonopods in this order. In the adult male of the species Hoffmaneuma exiguum, for example, the gonopod complex derives from all three leg pairs rather than from just the usual two.

Entomobielziidae is a family of millipedes belonging to the order Chordeumatida. This family includes 18 species, including 13 in the genus Tianella. Millipedes in this family are found in Romania, central Asia, and the Himalayas.

Kashmireumatidae is a small family of millipedes belonging to the order Chordeumatida. These millipedes range from 5mm to 14mm in length and are found in East Asia. Adult millipedes in this family have only 26 or 28 segments rather than the 30 segments usually found in this order. In the species Vieteuma topali, adults have 26 segments, whereas in all other species in this family, adults have 28 segments.

Opisthocheiridae is a family of millipedes belonging to the order Chordeumatida. This family includes 40 species distributed among seven genera. These millipedes are found in western Europe and Morocco.

Opisthocheiron is a genus of millipedes in the family Opisthocheiridae. These millipedes are found in France and Spain. The French entomologist Henri Ribaut created this genus in 1913 to contain the newly discovered type species Opisthocheiron penicillatum. This genus also includes the cave-dwelling species Opisthocheiron canayerensis, notable as one of only a few species in the order Chordeumatida with only 26 segments in adults, four fewer segments than typically found in adults in this order. The adult female of this species has only 42 pairs of legs, and the adult male has only 40 pairs of walking legs, excluding two pairs of gonopods.

Chamaesoma is a monotypic genus of millipede in the family Chamaesomatidae, and Chamaesoma broelemanni is the only species in this genus. This millipede is notable as one of only a few species in the order Chordeumatida with only 26 segments in adults, four fewer segments than typically found in adults this order. This species lives on the surface of the soil and is distributed across most of France and Luxembourg. The genus Chamaesoma and its only species were first described by the German zoologist Karl W. Verhoeff in 1913 based on type material found by the French zoologists Henri Brölemann and Henri Ribaut under wet leaf litter near St. Béat in the Pyrenees in France.

Haasea hungarica is a species of millipede in the family Haaseidae. This species is a eutroglophile, capable of spending its entire life cycle in a cave but also capable of living on the surface outside of caves. Although these millipedes are often found in caves, this species has also been found on the soil surface in forests.

Lipseuma is a genus of millipedes in the family Kashmireumatidae. This genus contains only two species, the type species L. josianae and its close relative L. bernardi. Both species are troglobites found in caves in China.

Tianella is a genus of millipedes in the family Entomobielziidae. This genus includes eleven species found in Nepal, one species found in Kazakhstan, and one species found in Kyrgyzstan. This genus is notable for including the only species in the order Chordeumatida with 29 segments in adults. Most species in this genus have 29 segments in adults rather than the 30 segments usually observed in this order.

Metamastigophorophyllon is a genus of millipedes in the family Anthroleucosomatidae. This genus includes millipedes found in Azerbaijan, Iran, Russia, and Georgia. All five species in this genus have 31 segments in adults. This genus is notable for including the only species in the order Chordeumatida with 31 segments rather than the 30 segments usually observed in adults in this order.

Neocambrisoma is a genus of millipedes in the family Metopidiotrichidae. Millipedes in this genus are found in Tasmania and New South Wales in Australia. Like other genera in this family, this genus features 32 segments in adults of both sexes, rather than the 30 segments usually observed in adults in the order Chordeumatida. Accordingly, female adults in this genus have 54 pairs of legs, which is not only the maximum number observed in this order but also the maximum number fixed by species in the class Diplopoda.

References

  1. ↑ "MilliBase - Opisthocheiron canayerensis Mauriès & Goeffrey, 1982". www.millibase.org. Retrieved 2024-06-24.
  2. ↑ Kime, Richard Desmond; Enghoff, Henrik (2021-09-22). "Atlas of European millipedes 3: Order Chordeumatida (Class Diplopoda)". European Journal of Taxonomy (769): 1–244 [134]. doi:10.5852/ejt.2021.769.1497. ISSN   2118-9773.
  3. 1 2 3 4 5 6 Geoffroy, Jean-Jacques (1984). "Particularités du Développement Post-embryonaire du Diplopode Craspedosomide Cavernicole Opisthocheiron canayerensis". Mémoires de Biospéologie (in French). 11: 211–220.
  4. 1 2 3 4 Enghoff, Henrik; Dohle, Wolfgang; Blower, J. Gordon (1993). "Anamorphosis in Millipedes (Diplopoda) — The Present State of Knowledge with Some Developmental and Phylogenetic Considerations". Zoological Journal of the Linnean Society. 109 (2): 103–234. doi:10.1111/j.1096-3642.1993.tb00305.x.
  5. 1 2 Mauriès, J.-P.; Geoffroy, J.-J. (1982). "Decouverte, dans les causses majeurs, d'une remarquable espece cavernicole du genre Opisthocheiron Ribaut, 1913 (Diplopoda, Craspedosomida, Opisthocheiridae)". Bulletin de la Société d'histoire naturelle de Toulouse (in French). 118: 131–140 – via Gallica.
  6. ↑ David, Jean-François (1989). "Le cycle biologique de Chamaesoma broelemanni Ribaut et Verhoeff, 1913 (Diplopoda, Craspedosomatida) en forêt d'Orléans (France)". Bulletin du Muséum National d'Histoire Naturelle (4) A, Zoologie (in French). 11: 639–647. doi: 10.5962/p.288286 – via Biodiversity Heritage Library.
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