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Cyphophthalmi

Cyphophthalmi is a suborder of harvestmen, colloquially known as mite harvestmen. Cyphophthalmi comprises 36 genera, and more than two hundred described species. The six families are currently grouped into three infraorders: the Boreophthalmi, Scopulophthalmi, and Sternophthalmi.[1]

Cyphophthalmi
Temporal range: 99–0 Ma Late Cretaceous-Present
Siro sp., USA
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Arthropoda
Subphylum: Chelicerata
Class: Arachnida
Order: Opiliones
Suborder: Cyphophthalmi
Simon, 1879
Infraorders
Diversity
6 families, > 200 species

Description

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Cyphophthalmi are smaller than the more familiar "daddy long-legs" harvestmen, with adults ranging from 1 to 7 mm in length. Moreover, their legs are relatively short compared to most other harvestmen, typically shorter than the body. Some superficially resemble mites, which is where they get their common name. Their coloration is almost always some shade of brown, with a heavily sclerotized body, and they are quite inconspicuous, residing in leaf litter or in caves.[2] Many Cyphophthalmi are eyeless, and presumably rely on olfactory cues to find food and mates. Very little is known about their behavior, though they likely subsist mostly by scavenging and preying on minute arthropods.[2] They have low dispersal rates and consequently high endemism.[3]

Diagnostic features

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Cyphophthalmi differ from other harvestmen in a number of key ways. Like all harvestmen, they have a pair of ozopores located on the sides of the prosoma. Unlike other harvestmen, however, the ozopores in Cyphophthalmi are located on elevated cone-shaped structures known as ozophores. Although members of most families are eyeless, most members of the families Pettalidae and Stylocellidae do have eyes located on or near the ozophores.[2] These eyes, however, are not homologous to the eyes of other harvestmen, and are instead derived from ancestral lateral eyes, instead of ancestral median eyes, as is the case for other harvestmen.[4] The male genitalia of Cyphophthalmi is unique among harvestmen, as males lack a true penis, and instead have a short spermatopositor, a structure which is not inserted inside the female, but used to deposit a spermatophore. In addition, they are the only harvestmen to lack a genital operculum, and instead exhibit a completely open gonopore. Mating in Cyphophthalmi is not well studied, but in some species at least, males and females do engage in direct contact. They further differ from most harvestmen in that the first 8 opisthosomal tergites and the prosomal carapace are fused together in what is known as a scutum completum, although this feature is also known from the unrelated family Sandokanidae.[2]

Sexual dimorphisms

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Like most animals, Cyphophthalmi express morphological distinctions between male and female individuals. Male Cyphophthalmi possess a structure on their fourth pair of tarsi known as an adenostyle. The adenostyle usually appears as a small hornlike projection, but can take a variety of shapes, depending on species. The function of the adenostyle is currently unknown, but is presumably associated with chemical glands. Aside from the adenostyle, males in many species possess glandular pores on either the underside of the opisthosoma or the anal region, although these glands are not present in all species. Males in several families also possess structural modifications of the anal plate and males of certain species in the family Stylocellidae possess a modified patch of cuticle near the adenostyle known as the Rambla's organ. The exact function of these glands and structures is currently unknown.[2]

Chemical defenses

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Like most harvestmen, Cyphophthalmi rely heavily on chemical secretions for defense. This defensive character is particularly well developed in Cyphophthalmi, when compared to the more familiar Eupnoi and Dyspnoi. Cyphophthalmi possess more elaborate musculature associated with the defensive glands than other harvestmen, and the secretions, which primarily consist of a variety of naphthoquinones and ketones, are thought to be more potent than in Eupnoi and Dyspnoi.[2][5]

Distribution

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Cyphophthalmids are found on all continents, with the exception of Antarctica, where they probably also once lived. As they did not disperse onto any oceanic islands, and it is believed that they did not travel between separate landmasses, they make an interesting subject for biogeography. Each of the six currently recognized families has a distinct distribution:[2]

Colombia shows the largest diversity of cyphophthalmids among countries in South America. This could reflect the large number of ecosystems found there, but could also be due to a high rate of sampling in this country.[6]

Fossil record

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A fossil cyphophthalmid assigned to a modern genus, Siro platypedibus Dunlop & Giribet, 2003 (Sironidae), was described from Paleogene aged Bitterfeld amber of eastern Germany. Another of this genus was described from Eocene Baltic amber as Siro balticus Dunlop & Mitov, 2011. A third fossil, Palaeosiro burmanicum Poinar, 2008, has been described from the Cretaceous (Cenomanian) aged Burmese amber. It was also assigned to Sironidae but is now thought to belong to Stylocellidae (a more typical Asian family).[7] As the fossil record for Cyphophthalmi is so sparse, recent studies have attempted to predict the diversification time of the suborder by using molecular clocks and comparing gene sequences among living taxa. One 2012 study estimated the earliest diversification of the suborder at approximately 332 MYA, in the Carboniferous.[1] Another study, in 2014, recovered a diversification age of approximately 340 MYA.[8] A more recent study in 2017, however, recovered the diversification of the modern Cyphophthalmi lineages to have occurred more recently, during the Jurassic, with the emergence of the suborder as a whole at less than 300 MYA.[9]

Relationships

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Cyphophthalmi is one of the two major lineages of harvestmen; the other, containing the Laniatores, Dyspnoi and Eupnoi, is known as Phalangida.[10] The extinct suborder, Tetrophthalmi, shares several features in common with Cyphophthalmi, and these two suborders may represent sister taxa.[4] They are grouped into the following infraorders: Boreophthalmi, Scopulophthalmi, and Sternophthalmi. The Boreophthalmi and Sternophthalmi together form a monophyletic clade, and comprise 5 of the 6 families of Cyphphthalmi. The Scopulophthalmi, with only 1 family, the Pettalidae, forms the sister group to all the other families. Within the Sternophthalmi, the families Ogoveidae and Neogoveidae are most closely related, and form the superfamily Ogoveoidea, which is the sister group to the family Troglosironidae.[1] The systematics of the Boreophthalmi, however, is not yet fully resolved. In one recent analysis, the Boreophthalmi were recovered as paraphyletic with respect to the Sternophthalmi.[9] Even within the Boreophthalmi, the Sironidae has been recovered either as sister family to Stylocellidae, or as paraphyletic with respect to Stylocellidae.[1] In addition, there are 3 genera of Cyphophthalmi with uncertain affinities that have not been placed in any family or infraorder.[11][1]

Cyphophthalmi
Scopulophthalmi

Pettalidae

Boreophthalmi

Sironidae

Stylocellidae

Sternophthalmi
Ogoveoidea

Neogoveidae

Ogoveidae

Troglosironidae

Recovered by Giribet et al. (2012)
Cyphophthalmi
Scopulophthalmi

Pettalidae

Stylocellidae

Sironidae

Sternophthalmi
Ogoveoidea

Neogoveidae

Ogoveidae

Troglosironidae

Recovered by Fernandez et al. (2017)

Taxonomy

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History of taxonomy

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Originally, Cyphophthalmi was recognized as a single family consisting of two subfamilies, Sironini and Stylocellini. This classification scheme existed until 1980, when a new taxonomy was proposed, separating 5 families into the now-defunct infraorders Temperophthalmi (consisting of Petallidae, Sironidae and, later, Troglosironidae) and Tropicophthalmi (consisting of Stylocellidae, Ogoveidae and Neogoveidae).[2] These two infraorders were never recovered as monophyletic in subsequent studies, and, following a 2012 phylogenetic analysis, a new Cyphophthalmi taxonomy was proposed.[1]

Current taxonomy

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The Cyphophthalmi are currently represented by the following taxa, which represent approximately 200 species, although there are a significant number of undescribed species that have been collected, and the current number of species is believed to be a severe under-representation.[12][13][14] The monophyly of most subgroups of Cyphophthalmi is well supported, although both Boreophthalmi and Sironidae have been recovered as paraphyletic in recent analyses.[1][9]

  • Family Sironidae Simon, 1879 (9 genera, 60 species)
  • Family Stylocellidae Hanson and Sørenson, 1904 (6 genera [3 extinct], 41 species)
  • Family Pettalidae Shear, 1980 (11 genera, 80 species)

See also

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Footnotes

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  1. ^ a b c d e f g Giribet, Gonzalo; Sharma, Prashant P.; Benavides, Ligia R.; Boyer, Sarah L.; Clouse, Ronald M.; De Bivort, Benjamin L.; Dimitrov, Dimitar; Kawauchi, Gisele Y.; Murienne, Jerome (2012-01-01). "Evolutionary and biogeographical history of an ancient and global group of arachnids (Arachnida: Opiliones: Cyphophthalmi) with a new taxonomic arrangement". Biological Journal of the Linnean Society. 105 (1): 92–130. doi:10.1111/j.1095-8312.2011.01774.x. ISSN 1095-8312. S2CID 86347821.
  2. ^ a b c d e f g h Pinto-da-Rocha, Ricardo; Machado, Glauco; Giribet, Gonzalo (2007). Harvestmen: The Biology of Opiliones. Harvard University Press. ISBN 9780674023437.
  3. ^ Cyphophthalmi Research page at Harvard's Museum of Comparative Zoology Archived 2010-07-16 at the Wayback Machine
  4. ^ a b Garwood, Russell J. (2014-05-05). "A Paleozoic Stem Group to Mite Harvestmen Revealed through Integration of Phylogenetics and Development". Current Biology. 24 (9): 1017–1023. doi:10.1016/j.cub.2014.03.039. ISSN 0960-9822. PMID 24726154. S2CID 14841693.
  5. ^ Jones, Tappey H.; Shear, William A.; Giribet, Gonzalo (2009). "The Chemical Defenses of a Stylocellid (Arachnida, Opiliones, Stylocellidae) from Sulawesi with Comparisons to Other Cyphophthalmi". The Journal of Arachnology. 37 (2): 147–150. doi:10.1636/sh08-48.1. JSTOR 40233821. S2CID 86547414.
  6. ^ Benavides Silva, Ligia; Giribet, Gonzalo (2007-06-18). "An Illustrated Catalogue Of The South American Species Of The Cyphophthalmid Family Neogoveidae (Arthropoda, Opiliones, Cyphophthalmi) With A Report On 37 Undescribed Species". Zootaxa. 1509. doi:10.5281/zenodo.177215.
  7. ^ Dunlop, J. A., Penney, D. & Jekel, D. 2014. A summary list of fossil spiders and their relatives. In Platnick, N. I. (ed.) The world spider catalog, version 15.0 American Museum of Natural History, online at http://research.amnh.org/entomology/spiders/catalog/index.html
  8. ^ Sharma, Prashant P.; Giribet, Gonzalo (2014). "A revised dated phylogeny of the arachnid order Opiliones". Frontiers in Genetics. 5: 255. doi:10.3389/fgene.2014.00255. ISSN 1664-8021. PMC 4112917. PMID 25120562.
  9. ^ a b c Fernández, Rosa; Sharma, Prashant P.; Tourinho, Ana Lúcia; Giribet, Gonzalo (2017-02-22). "The Opiliones tree of life: shedding light on harvestmen relationships through transcriptomics". Proceedings of the Royal Society B: Biological Sciences. 284 (1849): 20162340. doi:10.1098/rspb.2016.2340. ISSN 0962-8452. PMC 5326524. PMID 28228511.
  10. ^ Shultz, Jeffrey W. & Pinto-da-Rocha, Ricardo (2007): Morphology and Functional Anatomy. In: Pinto-da-Rocha et al. 2007: 15ff
  11. ^ Shear, W.A. (1985). "Marwe coarctata: A remarkable new cyphophthalmid from a limestone cave in Kenya (Arachnida, Opiliones)". American Museum Novitates. 2830: 1–6. hdl:2246/3584.
  12. ^ Kury, Adriano Brilhante; Giupponi, Alessandro Ponce de Leão (2015-01-26). "A new species of Metagovea Rosas Costa, 1950 from Napo Province, Ecuador (Opiliones, Cyphophthalmi, Neogoveidae)". ZooKeys (477): 1–15. doi:10.3897/zookeys.477.8706. ISSN 1313-2970. PMC 4319056. PMID 25685003.
  13. ^ Giribet, Gonzalo; Benavides, Ligia R.; Merino-Sáinz, Izaskun (2017-08-30). "The systematics and biogeography of the mite harvestman family Sironidae (Arachnida : Opiliones : Cyphophthalmi) with the description of five new species". Invertebrate Systematics. 31 (4): 456–491. doi:10.1071/IS16086. ISSN 1447-2600. S2CID 90781847.
  14. ^ Giribet, Gonzalo; Boyer, Sarah L.; Baker, Caitlin M.; Fernández, Rosa; Sharma, Prashant P.; de Bivort, Benjamin L.; Daniels, Savel R.; Harvey, Mark S.; Griswold, Charles E. (2016-11-01). "A molecular phylogeny of the temperate Gondwanan family Pettalidae (Arachnida, Opiliones, Cyphophthalmi) and the limits of taxonomic sampling". Zoological Journal of the Linnean Society. 178 (3): 523–545. doi:10.1111/zoj.12419. ISSN 1096-3642. S2CID 49331211.

Further reading

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