Agenodesmus reticulatus

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Agenodesmus reticulatus
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Arthropoda
Subphylum: Myriapoda
Class: Diplopoda
Order: Polydesmida
Family: Fuhrmannodesmidae
Genus: Agenodesmus
Species:
A. reticulatus
Binomial name
Agenodesmus reticulatus
Loomis, 1934

Agenodesmus reticulatus is a species of millipede in the family Fuhrmannodesmidae, [1] which some authorities consider a junior synonym of Trichopolydesmidae. [2] [3] [4] This millipede is among the very few species in the order Polydesmida to feature adults with only 18 segments (including the telson) rather than the 20 segments usually found in this order. [5] This species is notable as the first polydesmidan millipede discovered with only 18 segments in adults, the smallest number recorded in the order Polydesmida. [6] [5] Before the discovery of A. reticulatus, polydesmidans were known to have only 19 or 20 segments in adults. [6]

Contents

Discovery and distribution

The American biologists Orator F. Cook and Harold F. Loomis found the first specimens of A. reticulatus, including the male type specimen and several females, in Haiti in June 1927. Eleven more specimens were found in 1930 and 1932, including mature females as well as young, in not only Haiti but also Saint Kitts, Saint Lucia, Dominica, and Grenada. Loomis first described the genus Agenodesmus and its type species A. reticulatus in 1934 based on these specimens. [6] The male holotype is deposited in the National Museum of Natural History in Washington, D.C. [7] [8]

A closely related species with only 18 segments in adults, Hexadesmus lateridens , was discovered in Cuba in 1931, with Loomis finding additional specimens in Saint Kitts and Carriacou in 1932. Loomis described the monotypic genus Hexadesmus and its type specimen H. lateridens based on these specimens in 1933, [9] before he described A. reticulatus in 1934. Loomis also collected a young specimen of H. lateridens in Haiti in July 1927. [6] Thus, H. lateridens was the first species formally described with so few segments in adults but the second such species to be discovered. [6]

Description

This millipede is notable not only for featuring only 18 segments in adults but also for its tiny size. The maximum size recorded is only 2 mm in length and 0.25 mm in width. [6]  This species is the smallest millipede in the Western hemisphere [10] [11] and one of the smallest millipedes known. [6] [7]

Polydesmidan millipedes with only 18 segments as adults go through the same stages of teloanamorphosis observed in other polydesmidans until reaching maturity, which occurs two molts earlier than in the typical polydesmidan. [12] Thus, the species A. reticulatus goes through only six stages of development rather than the usual eight stages, reaching maturity with only 18 segments. In the sixth and final stage, female adults of this species have 27 pairs of legs, and male adults have 26 leg pairs (excluding the eighth leg pair, which become gonopods). [5]

This species is white with a slight tinge of pink. The surface of the head and the dorsal surface of the body segments are reticulated. The head is large with many tiny bristles but no median furrow. The antennae are markedly clavate (club-shaped). [6]

The dorsal surface of the body features transverse rows of markedly clavate setae but no tubercles. The first segment has an oval shape, about twice as wide as long, with a broad transverse depression in the middle. This segment is narrower than the head or the other segments. The second segment features keels that are slightly longer than those on the next two segments. The anterior and posterior corners of all the keels are rounded except for the three segments in front of the telson, which have keels with acute (sharply pointed) posterior corners. The telson is as long as or longer than the penultimate segment. The tail end of the telson curves slightly downward. [6]

The ozopores are large and rimless. Each one appears at the top of a slight swelling of the dorsal surface. These ozopores appear on the posterior corners of segments 5, 7, 9, 10, 12, 13, 15, 16, and 17. [6]

The basal joint of each gonopod is hooded and somewhat covered with bristles. The apical joint of each gonopod is small and simple, emerging from an opening in the inner surface of the basal joint near the front. Each of these apical joints curves upward, outward, and backward and terminates in two branches with similar lengths, the anterior branch heavy and foliate at the apex, the posterior branch slender and attenuated. [6]

This millipede is smaller than the only other species in the genus Agenodesmus, A. nullus , which reaches a maximum size of 2.75 mm in length and 0.25 mm in width. [7] Both species of Agenodesmus are smaller than their close relative H. lateridens, which can reach 3.8 mm in length and 0.3 mm in width. [9] Both species of Agenodesmus may be distinguished from H. lateridens by not only their sizes but also the shape of their dorsal setae: the setae of Agenodesmus are clavate, whereas the setae of H. lateridens are slender and acute. [7] [6]

The two species of Agenodesmus may be distinguished from one another by not only their sizes but also the ozopores on the dorsal surface of their body segments. Whereas the distribution of ozopores among these segments in A. reticulatus resembles the distribution typically observed in the order Polydesmida, [6] [13] A. nullus features a more unusual distribution. The distribution in A. nullus differs from that observed in A. reticulatus insofar as A. nullus features an ozopore on segment 14, a vestigial pore on segment 16, and no ozopore on segment 17. Furthermore, although adult males of the species A. nullus have 18 segments, like both male and female adults in the species A. reticulatus, adult females of the species A. nullus have 20 segments. [7]

Habitat and ecology

This millipede is usually found in moist dead leaves. [11] This species has probably been distributed among the Caribbean islands in its range by humans. [8] The small size of this millipede makes this species likely to be transported in soil undetected and spread inadvertently by humans. [7]

Related Research Articles

<i>Harpaphe haydeniana</i> Species of millipede

Harpaphe haydeniana, commonly known as the yellow-spotted millipede, almond-scented millipede or cyanide millipede, is a species of polydesmidan ("flat-backed") millipede found in the moist forests along the Pacific coast of North America, from Southeast Alaska to California, however, also seen in northern Brazil. The dark coloration with contrasting yellow-tipped keels warn of its ability to exude toxic hydrogen cyanide as a defense. The cyanide secretions are not dangerous to humans, but can cause irritation and pain if it contacts sensitive areas such as the mouth, eyes, or nose.

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

Polydesmida is the largest order of millipedes, with more than 5,000 species, including all the millipedes reported to produce hydrogen cyanide (HCN). This order is also the most diverse of the millipede orders in terms of morphology. Millipedes in this order are found in all regions of the world other than Antarctica.

<span class="mw-page-title-main">Xystodesmidae</span> Family of millipedes

Xystodesmidae is a family of millipedes in the suborder Leptodesmidea within the order Polydesmida. The family Xystodesmidae was created by the American biologist Orator F. Cook in 1895 and named after the genus Xystodesmus. This family includes more than 390 known species distributed among 62 genera. Many species, however, remain undescribed: for example, it is estimated that the genus Nannaria contains over 200 species, but only 25 were described as of 2006. By 2022, 78 species in Nannaria have been described.

Tridontomidae is a small family of millipedes. Its members are endemic to Guatemala. These millipedes range from 22 mm to 28 mm in length and are uniformly grayish in color; their legs and antennae are unusually long and slender. This family includes the remarkable species Aenigmopus alatus, in which adult males feature no gonopods. This millipede is the only species in the infraclass Helminthomorpha without gonopods.

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

Chordeumatida is a large order of millipedes containing more than 1,400 species. Also known as sausage millipedes, they are found nearly worldwide. Chordeumatida is the largest order in the superorder Nematophora, a group also known as spinning millipedes because their telsons feature spinnerets used to build nests of silk. These millipedes produce this silk to create chambers in which to molt or to lay their eggs.

<i>Siphoniulus</i> Genus of millipedes

Siphoniulus is a poorly known genus of millipede containing only two living species: S. alba from Indonesia, and S. neotropicus from Mexico and Guatemala. An additional two fossil species are known from Cretaceous amber. Siphoniulus species are the only members of the family Siphoniulidae and order Siphoniulida, making Siphoniulida the smallest millipede order. Few specimens are known, and their classification is contentious, although most recent studies place them as basal members of the Helminthomorpha.

<span class="mw-page-title-main">Platyrhacidae</span> Family of millipedes

Platyrhacidae is a family of polydesmidan millipedes distributed in Southeast Asia and tropical Central and South America.

<span class="mw-page-title-main">Haplodesmidae</span> Family of millipedes

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<span class="mw-page-title-main">Ammodesmidae</span> Family of millipedes

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<span class="mw-page-title-main">Conotylidae</span> Family of millipedes

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<span class="mw-page-title-main">Metopidiotrichidae</span> Family of millipedes

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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.

<i>Stenoniodes</i> Genus of millipedes

Stenoniodes, commonly known as the Borneo tractor millipede, is a genus of millipede in the family Platyrhacidae. It contains six species, five of which occur on Borneo and one on Sibutu Island. Its common name originates from the likeness of its 20-segmented body to the tread of a tractor's tire.

Agenodesmus is a genus of millipedes in the family Fuhrmannodesmidae, which some authorities consider a junior synonym of Trichopolydesmidae. This genus is notable for being among the very few genera in the order Polydesmida to feature adults with only 18 segments rather than the 20 segments usually found in this order. The genus Agenodesmus contains only two species, A. reticulatus and A. nullus. The type species A. reticulatus is notable as the first polydesmidan millipede discovered with only 18 segments in adults, the smallest number recorded in the order Polydesmida. Before the discovery of A. reticulatus, polydesmidans were known to have only 19 or 20 segments in adults.

Devillea is a genus of flat-backed millipedes in the family Xystodesmidae. These millipedes are rare and limited to caves. Species in this genus are found in Sardinia, Capri, and southern France in the Maritime Alps. These species are notable for featuring more than the 20 segments usually found in the order Polydesmida. This genus is one of only two genera in this order to feature these extra segments and the first such genus to be discovered.

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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.

Devilliea tuberculata is a species of flat-backed millipedes in the family Xystodesmidae. Like other members of the genus Devillea, this species is limited to caves. This millipede has been found in several caves in the Alpes-Maritimes department of France. This species is notable as the first millipede in the order Polydesmida found to feature more than the 20 segments usually found in this order.

References

  1. ↑ "ITIS - Report: Agenodesmus reticulatus". www.itis.gov. Retrieved 2024-08-17.
  2. ↑ "MilliBase - Fuhrmannodesmidae Brölemann, 1916". www.millibase.org. Retrieved 2024-08-17.
  3. ↑ Golovatch, Sergei (2013-10-04). "A reclassification of the millipede superfamily Trichopolydesmoidea, with descriptions of two new species from the Aegean region (Diplopoda, Polydesmida)". ZooKeys (340): 63–78 [74]. Bibcode:2013ZooK..340...63G. doi: 10.3897/zookeys.340.6295 . ISSN   1313-2970. PMC   3800799 . PMID   24146592.
  4. ↑ Enghoff, Henrik; Golovatch, Sergei; Short, Megan; Stoev, Pavel; Wesener, Thomas (2015-01-01), "Diplopoda — taxonomic overview", Treatise on Zoology - Anatomy, Taxonomy, Biology. The Myriapoda, Volume 2, Brill, pp. 363–453, doi:10.1163/9789004188273_017, ISBN   978-90-04-18827-3 , retrieved 2024-06-05
  5. 1 2 3 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 [108-109, 147-150]. doi:10.1111/j.1096-3642.1993.tb00305.x.
  6. 1 2 3 4 5 6 7 8 9 10 11 12 13 Loomis, H. F. (1934). "Millipeds of the West Indies and Guiana, collected by the Allison V. Armour Expedition in 1932". Smithsonian Miscellaneous Collections. 89 (14): 1-69 [40-41].
  7. 1 2 3 4 5 6 Shear, William A.; Peck, Stewart B. (1987-11-01). "Millipeds (Diplopoda) of the Galapagos Islands, Ecuador". Canadian Journal of Zoology. 65 (11): 2640–2645. doi:10.1139/z87-400. ISSN   0008-4301.
  8. 1 2 Hoffman, Richard L.; Hoffman, Richard L. (1999). Checklist of the millipeds of north and middle America. Martinsville, VA: Virginia Museum of Natural History. p. 464. ISBN   978-1-884549-12-0.
  9. 1 2 Loomis, H.F. (1933). "Three new Cuban millipeds, with notes on two little-known species". Bulletin of the Museum of Comparative Zoology. 75 (9): 357–363 – via Biodiversity Heritage Library.
  10. ↑ Pérez-Asso, A.R.; Pérez-Gelabert, D.E. (2001). "Checklist of the Millipeds (Diplopoda) of Hispaniola". Boletín de la Sociedad Entomológica Aragonesa. 28: 67-80 [77].
  11. 1 2 Loomis, Harold F. (1936). "The Millipeds of Hispaniola, with descriptions of a new family, new genera and new species". Bulletin of the Museum of Comparative Zoology at Harvard College. 80: 1–191 [156].
  12. ↑ Shear, William A.; Ferreira, Rodrigo Lopes; Iniesta, Luiz Felipe Moretti; Marek, Paul (2016-10-25). "A millipede missing link: Dobrodesmidae, a remarkable new polydesmidan millipede family from Brazil with supernumerary rings (Diplopoda, Polydesmida), and the establishment of a new suborder Dobrodesmidea". Zootaxa. 4178 (3): 371–390 [381]. doi:10.11646/zootaxa.4178.3.4. ISSN   1175-5334. PMID   27811714 – via ResearchGate.
  13. ↑ Mesibov, Robert (2019). "External Anatomy of Polydesmida: Gonopods". www.myriapodology.org. Retrieved 2024-08-17.
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