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 are smaller than the more familiar "daddy long-legs" harvestmen, with adults ranging from 1 to 7mm 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
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
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
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
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]
Troglosironidae: found exclusively in New Caledonia.
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
A fossil cyphophthalmid assigned to a modern genus, Siro platypedibusDunlop & Giribet, 2003 (Sironidae), was described from the OligoceneBitterfeld amber of eastern Germany. A slightly older representative of this genus was described from Eocene Baltic amber as Siro balticusDunlop & Mitov, 2011. A third fossil, Palaeosiro burmanicumPoinar, 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
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
History of taxonomy
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
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]
↑ 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
↑ Shultz, Jeffrey W. & Pinto-da-Rocha, Ricardo (2007): Morphology and Functional Anatomy. In: Pinto-da-Rocha et al. 2007: 15ff
↑ 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.
↑ 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. ISSN1447-2600. S2CID90781847.
The Opiliones are an order of arachnids colloquially known as harvestmen, harvesters, harvest spiders, or daddy longlegs. As of April 2017, over 6,650 species of harvestmen have been discovered worldwide, although the total number of extant species may exceed 10,000. The order Opiliones includes five suborders: Cyphophthalmi, Eupnoi, Dyspnoi, Laniatores, and Tetrophthalmi, which were named in 2014.
Dyspnoi is a suborder of harvestmen, currently comprising 43 extant genera and 356 extant species, although more species are expected to be described in the future. The eight families are currently grouped into three superfamilies: the Acropsopilionoidea, Ischyropsalidioidea, and Troguloidea.
The Sironidae are a family of harvestmen with more than 60 described species.
Caddoidea superfamily of harvestmen arachnids with a single family Caddidae, which now only contains 2 extant species. The family previously contained many more taxa under a previous wider concept, but the familial definition was narrowed after restudy.
Troglosironidae is a family of harvestmen with seventeen described species in a single genus, Troglosiro, which is found on the island of New Caledonia, in the Pacific Ocean.
Ogoveidae is a family of harvestmen with three described species in one genus, Ogovea, which is found in equatorial West Africa.
The Neogoveidae are a family of harvestmen with 27 described species in eight genera. However, eight species of Huitaca, 17 species of Metagovea and 12 species of Neogovea are currently awaiting description.
The Stylocellidae are a family of harvestmen with about 40 described species, all of which occur in Southern or Southeastern Asia. Members of this family are from one to seven millimeters long. While Stylocellus species have eyes, these are absent in the other two genera.
The Pettalidae are a family of harvestmen with 75 described species in 10 genera. Several undescribed species are known or assumed in some genera.
Ischyropsalididae is a family of harvestmen with 35 described species in 3 genera, found in Europe and North America.
Nemastomoides is an extinct genus of harvestmen known from the Carboniferous fossil record. The genus is the only member of the family Nemastomoididae and contains three described species. Nemastomoides elaveris was found in the Coal Measures of Commentry in northern France, together with Eotrogulus fayoli.
Harvestmen (Opiliones) are an order of arachnids often confused with spiders, though the two orders are not closely related. Research on harvestman phylogeny is in a state of flux. While some families are clearly monophyletic, that is share a common ancestor, others are not, and the relationships between families are often not well understood.
Tetrophthalmi is an extinct suborder of Opiliones that had both median and lateral eyes. First described in 2014, it is known from two extinct species. Phylogenetic analysis suggests that this eye arrangement is the ancestral condition for harvestmen, placing Tetrophthalmi and Cyphophthalmi in a basal position within Opiliones.
Gonzalo Giribet is a Spanish-American invertebrate zoologist and Alexander Agassiz Professor of zoology working on systematics and biogeography at the Museum of Comparative Zoology in Harvard University. He is a past president of the International Society for Invertebrate Morphology, of the Willi Hennig Society, and vice-president of the Sociedad Española de Malacología.
Huitaca boyacaensis is a species of neotropical harvestmen in the family Neogoveidae, first described by Ligia Benavides and Gonzalo Giribet in 2013.
Neosiro exilis is a species of mite harvestman in the family Sironidae. It is found in North America.
Holosiro calaveras is a species of mite harvestman in the family Sironidae. It is found in North America, specifically California in Calaveras county.
Acropsopilionoidea is a superfamily of harvestmen with 1 family and 3 genera, found in North America and the Southern Hemisphere.
Neosiro is a genus of mite harvestman in the family Sironidae. It is found in North America, only in the USA.
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