Where Can Organisms From the Family Peripatidae and Peripatopsidae Be Found

Diversity

Phylum Onychophora, or velvet worms, contains approximately 180 species of bilaterally symmetrical, coelomate organisms that somewhat resemble caterpillars. Onychophorans range from 5 mm to fifteen cm in length, with homonomous bodies and small heads. The head carries a pair of annulated, fleshy antennae and a pair of small optics at their bases, with large, chitinous lenses and a well-developed retinal layer, as well as a pair of jaws surrounded past circular lips, and a pair of fleshy oral papillae, likewise known as slime papillae. The sticky secretions produced past the latter structures are used to capture casualty, which includes other pocket-size invertebrates. Living species are divided into 2 families, Peripatidae and Peripatopsidae, which live in mutually exclusive geographical regions; peripatids are circumtropical, while peripatopsids are circumaustral. Members of the ii families differ in their number of legs (more often than not greater in peripatids), the position of their gonopore (on a more than posterior body segment in peripatopsids), and their reproductive habits. All of the currently known living species are terrestrial, living mainly in night, moist microhabitats. Research indicates that they are either modified arthropods or represent a link between annelids and arthropods, almost contempo molecular phylogenies favor the first hypothesis. (Brusca and Brusca, 2003; Monge-Nájera, 1995; Shapiro, 2012; Zhang, 2011)

Geographic Range

The two onychophoran families live in mutually exclusive regions. Peripatids are circumtropical, unremarkably establish in Chile, South Africa, and Australasia, while peripatopsids are circumaustral, found in Southeast Asia, due west equatorial Africa, northern Due south America, Central America, Mexico, and the Antilles. (Brusca and Brusca, 2003; Monge-Nájera, 1995)

• nearctic
  • native
• palearctic
  • native
• oriental
  • native
• ethiopian
  • native
• neotropical
  • native
• australian
  • native

• holarctic

Habitat

All currently living onychophoran species are terrestrial, although the fossil record shows they were likely aquatic at some betoken, the shift to land probably took identify during the Ordovician period. They are nocturnal and photonegative, living primarily in dark, moist microhabitats such every bit forest litter and soil, within bromeliads, or in rotten logs. A few species are cave habitation or live in drier woodlands and grasslands. (Brusca and Brusca, 2003; Monge-Nájera, 1995)

• temperate
• tropical
• terrestrial

• savanna or grassland
• forest
• rainforest
• scrub forest

Systematic and Taxonomic History

Early researchers considered onychophorans to exist a link betwixt annelids and arthropods, as they share characteristics with both phyla. Recent molecular research has suggested that onychophorans are actually modified arthropods, supporting the shared morphological characteristics between these phyla, including a chitinous cuticle, every bit well as features of their respiratory system and embryogenesis. Onychophorans and arthropods as well share an evolutionary human relationship with phylum Tardigrada, and together form the unranked taxon Panarthropoda. This clade belongs to superphylum Ecdysozoa, which contains other molting invertebrates, such equally nematodes, kinorhynchs, and loriciferans, simply the evolutionary relationships between these larger groups are still the field of study of active debate. As relatively poorly studied organisms, research on the evolutionary relationships within the phylum is sparse, although the monophyly of the phylum and its 2 families has consistently been strongly supported. (Ballard, et al., 1992; Monge-Nájera, 1995; Podsiadlowski, et al., 2008; Telford, et al., 2008)

• Synapomorphies

  • slime papillae and associated secretions
  • mandibles of the 2d body segment
  • extensively cross-linked nervus strands extending along the underside of body segments
  • unique tracheal morphology

Physical Description

Onychophorans range from 5 mm to 15 cm in length, with homonomous bodies and modest heads. The head houses a pair of annulated, fleshy antennae and a pair of pocket-size eyes at their bases, which are direct, with big, chitinous lenses and a developed retinal layer; a pair of jaws surrounded by circular lips; and a pair of fleshy oral papillae, as well known as slime papillae. These animals are covered in a thin, flexible, permeable, chitinous cuticle, which overlays a thin epidermis. The cuticle is characteristically covered in tubercles or papillae with sensilla, arranged in rings or bands around the torso and appendages. These protrusions are covered in scales, giving the animals a velvety advent that gives rise to their common name. Under the epidermis, onychophorans have a dermis of connective tissue and layers of circular, diagonal and longitudinal muscles. These animals have smooth and striated muscle tissue and their hemocoels are partitioned into sinuses; the coelom is restricted to the gonodal cavities. They accept hemocoelic, hydrostatic skeletons. Onychophorans are generally blueish, black, light-green or orangish. Onychophorans have 13 to 43 pairs of lobopodal walking legs; peripatopsid species accept a fixed number of legs, while peripatid species may have a variable number of legs. The conical legs are filled with hemocoelomic fluid and have extrinsic muscle extensions. Each leg has a multi-spined concluding hook and a distal transverse pad on which it rests while walking. Onychophorans are typically sexually dimorphic, females are larger than males. In species where the number of leg pairs are variable, females also have more legs. (Brusca and Brusca, 2003; Monge-Nájera, 1995; Shapiro, 2012; Waggoner, 1999)

The mouth opens into a chitin-lined pharynx and esophagus (foregut), which lead to a long, straight intestine where most digestion and absorption occurs. The hindgut typically loops over the intestine before it leads to the anus located on the last body segment (terminally or ventrally). Each leg-begetting body segment as well has a pair of nephridia with associated nephridiopores almost the base of operations of each leg, with the exception of the 4th and fifth legs, where nephridiopores are located distally on transverse pads, and the segment where the gonopores are located, which has no nephridia. Nephridia are connected internally to a sacculus (coelomic cease sac) which leads to a nephridioduct, together; the sacculus and nephridioduct are called the segmental gland. Each nephridioduct has a contractile float that opens via the nephridiopore. Some species have eversible sacs via hemocoelic pressure, or vesicles opening near the nephridiopores as well, which may help to accept up moisture. (Brusca and Brusca, 2003; Ruppert, et al., 2004)

Velvet worms also take well-adult circulatory systems, similar to arthropods. The centre is tubular, opens at both ends, and lies in a pericardial sinus. The blood, which is colorless and has no oxygen binding capabilities, enters the heart through lateral ostia and leaves anteriorly, flowing throughout the hemocoel within the trunk's sinuses. Hemal channels are besides located nether the cuticle, between the circular muscle and oblique muscle layers, and are likely important as part of the hydrostatic skeleton. Gas exchange occurs via improvidence beyond the body wall and through tracheae, which open through modest spiracles located between the bands of body tubercles. Tracheal units are pocket-sized and just provide gases to the tissues immediately adjacent to them. (Brusca and Brusca, 2003; Ruppert, et al., 2004)

• ectothermic
• heterothermic
• bilateral symmetry

• female larger
• sexes shaped differently

Evolution

Onychophorans may be oviparous, viviparous or ovoviviparous. In oviparous species, large, oval, yolky eggs (up to 2 mm in diameter), with chitinous shells are produced and laid through an ovipositor. Early, superficial, intralecithal cleavage occurs, due to the large size of the yolk, followed past the development of a germinal disc. Ovoviviparous species may produce large yolky eggs (up to 1.5 mm in bore), or smaller eggs (0.v mm in diameter) with little to no yolk and sparse membranes. Early cleavage of ovoviviparous embryos is intralecithal in those eggs with yolks; development has non been described well for not-yolky ovoviviparous eggs. Viviparous species produce small, spherical, non-yolky eggs and may or may not take placentas, when no placenta is nowadays, eggs are even smaller and cleavage is total and equal. Vivipary is the most commonly observed reproductive strategy for this phylum. Onychophorans develop directly and hatch, or are born as juveniles with developed torso segments and organs. (Brusca and Brusca, 2003; Eriksson and Tait, 2012)

Reproduction

Mating behavior has seldom been observed and seems to vary widely amongst species. Both dermal and vaginal inseminations are known. Males of some species (Florelliceps stutchburyae, Planipapillus annae) accept specialized caput structures with which they transfer a spermatophore direct to a female's genital opening; during the transfer, a male is held in identify by the female'southward lodopod claws. Others deposit spermatophores on females' bodies, triggering a breakup of integument and then that the sperm may pass into the hemocoelic fluid, through which it travels to the ovaries. Females of some species have seminal receptacles, which are enlargements of the uterus. Although the mating systems of most onychophorans have not been adamant, polygyny is most probable, equally vivipary is the nearly common reproductive strategy. ("Velvet Worm", 2010; Brusca and Brusca, 2003; Monge-Nájera, 1995; Tait and Norman, 2001)

• polygynous

Onychophorans are dioecious, with the exception of i known parthenogenetic species (Epiperipatus imthurni), and sexually dimorphic, females are larger than males, and potentially accept more than legs. Males accept a pair of elongated testes, their sperm ducts bring together into a unmarried tube, where spermatophores up to 1 mm in length are formed. The unmarried sperm tube opens in a posteroventral gonopore. Females have a pair of ovaries that are by and large fused and located in the posterior region of their bodies, connecting to gonoducts that fuse into a uterus, likewise opening through a posteroventral gonopore. Fertilization is internal. (Brusca and Brusca, 2003; Monge-Nájera, 1995; Read, 1988)

Peripatopsids may be oviparous, oviviparous or viviparous and produce 6 to 23 offspring a year, while peripatids are viviparous and only produce 1 to 8 offspring per yr. Peripatopsid eggs develop inside six to 17 months, or are born afterwards 11 to xiii months of gestation; the gestation flow for peripatids is approximately 1 year. Some onychophorans breed once a year, while others may breed multiple times in a yr. Gestation in viviparous species can be up to xv months, a female may take embryos of varied ages developing in her uterus at whatsoever given fourth dimension. (Eriksson and Tait, 2012; Monge-Nájera, 1995)

• iteroparous
• seasonal breeding
• year-round breeding
• gonochoric/gonochoristic/dioecious (sexes split up)
• parthenogenic
• sexual
• asexual
• fertilization
  • internal
• viviparous
• ovoviviparous
• oviparous

Across gamete production, the parental investment exhibited by onychophorans is unknown. In captivity, some species have been observed in adult-newborn groups, in the wild, groupings of young individuals are often found. (Monge-Nájera, 1995)

• no parental involvement
• pre-hatching/birth
  • provisioning
    • female

Lifespan/Longevity

Onychophorans typically live several years; females are not known to reproduce until reaching at least one.four years of age. (Brusca and Brusca, 2003; Monge-Nájera, 1995)

Behavior

Onychophorans are typically solitary; they are also photonegative and nocturnal. They are well-nigh agile in boiling and clammy environments; activity profoundly decreases during dry periods. Onychophorans motion using their lopodal legs and extending and contracting their bodies using hydrostatic forces. Movement is from front to back, in a wave; when an anterior segment elongates, their legs lift and movement frontwards and, when information technology contracts again, inductive legs and segments are pulled forward. (Brusca and Brusca, 2003; Monge-Nájera, 1995; Shapiro, 2012)

• terricolous
• nocturnal
• motile
• sedentary
• solitary

Communication and Perception

Onychophorans have large, bilobed cerebral ganglia dorsal to the pharynx, which are fastened to a pair of ventral nerve cords (via transverse segmental commissures) and supply fretfulness to the caput elements, also giving rise to the paired fretfulness of the appendages and body wall. The tubercles and papillae on their body surfaces are covered in sensilla. They take a small dorsolateral eye at the base of operations of each antenna, which are direct, with a chitinous lens and well-developed retinal layer. There is show that males of some onychophoran species secrete a pheromone from papillae on their legs, attracting both males and females in order to disperse and colonize new habitats such as rotting logs. (Barclay, et al., 2000; Brusca and Brusca, 2003; Monge-Nájera, 1995; Ruppert, et al., 2004; Shapiro, 2012)

• visual
• tactile
• chemic

• pheromones

• visual
• tactile
• chemical

Food Habits

Onychophorans are carnivorous, typically feeding on small invertebrates such as beetles, termites, and other insects, as well as snails and worms. They sometimes pursue their prey into small spaces. Onychophorans produce a powerful adhesive in their slime glands, which open at the end of their oral papillae; they tin shoot this substance upwardly to 30 cm to trap casualty. Onychophorans use their jaws to grasp and cutting casualty and inject salivary secretions, which are produced past paired salivary glands and delivered along a median dorsal groove on the jaws. These secretions begin to digest the prey then the semi-liquidized tissues can be sucked into the mouth. (Brusca and Brusca, 2003; Monge-Nájera, 1995; Shapiro, 2012)

• carnivore
  • insectivore
  • eats non-insect arthropods
  • molluscivore

Predation

The adhesive substance used by onychophorans to ensnare prey may also exist used to evade predators. Likewise, the lighter coloration of juveniles may be a blazon of camouflage. Their predators include birds, centipedes, and spiders, also every bit Hemprichi'due south coral snakes, which are believed to feed almost exclusively on onychophorans. (Brusca and Brusca, 2003; Monge-Nájera, 1995; Monge-Nájera, et al., 1993; Shapiro, 2012)

• ambiguous

• Known Predators

  • Hemprichi's coral snakes (Micrurus hemprichii)
  • clay-colored thrushes (Turdus grayi)
  • centipedes (Grade Chilopoda, Phylum Arthropoda)
  • spiders (Society Araneae, Phylum Arthropoda)

Ecosystem Roles

The regular molting cycles of onychophorans may be, in part, an anti-ectoparasite machinery. Phoretic mites have been reported on some onychophorans, as have unspecified bacteria reproducing in their mid-line cuticular pits. (Monge-Nájera, 1995)

Economic Importance for Humans: Positive

Outside of scientific inquiry, there are no known positive effects of onychophorans on humans. (Brusca and Brusca, 2003)

• research and educational activity

Economical Importance for Humans: Negative

There are no known adverse effects of onychophorans on humans. (Brusca and Brusca, 2003)

Conservation Status

Onychophorans are not considered threatened or in danger of extinction. ("Velvet Worm", 2010)

• IUCN Ruby List [Link]

  Not Evaluated

This phylum was part of the early Cambrian marine diversification and has an all-encompassing fossil record throughout Due north America and Asia. Beyond their motility from water to land, petty has changed for these species over the last 530 million years. (Bergstrom and Hou, 2001; Brusca and Brusca, 2003; Monge-Nájera, 1995)

Contributors

Jeremy Wright (author), University of Michigan-Ann Arbor, Leila Siciliano Martina (editor), Animal Diversity Web Staff.

Glossary

Australian

Living in Commonwealth of australia, New Zealand, Tasmania, New Republic of guinea and associated islands.

Ethiopian

living in sub-Saharan Africa (south of 30 degrees north) and Madagascar.

Nearctic

living in the Nearctic biogeographic province, the northern part of the New Earth. This includes Greenland, the Canadian Arctic islands, and all of the North American every bit far south as the highlands of primal United mexican states.

Neotropical

living in the southern function of the New Globe. In other words, Central and Due south America.

Palearctic

living in the northern part of the Erstwhile World. In otherwords, Europe and Asia and northern Africa.

asexual

reproduction that is not sexual; that is, reproduction that does non include recombining the genotypes of two parents

bilateral symmetry

having body symmetry such that the animal can exist divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

carnivore

an animal that mainly eats meat

chemical

uses smells or other chemicals to communicate

cryptic

having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural surround; being difficult to see or otherwise detect.

ectothermic

animals which must use heat caused from the surround and behavioral adaptations to regulate body temperature

fertilization

marriage of egg and spermatozoan

forest

forest biomes are dominated by trees, otherwise forest biomes tin vary widely in corporeality of precipitation and seasonality.

heterothermic

having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly adult mechanism for regulating internal body temperature.

holarctic

a distribution that more than or less circles the Chill, and then occurring in both the Nearctic and Palearctic biogeographic regions.

Found in northern Due north America and northern Europe or Asia.

insectivore

An creature that eats mainly insects or spiders.

internal fertilization

fertilization takes place within the female person's body

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and beyond multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic status changes).

molluscivore

eats mollusks, members of Phylum Mollusca

motile

having the chapters to move from one place to another.

native range

the expanse in which the fauna is naturally found, the region in which it is endemic.

nocturnal

active during the night

oriental

found in the oriental region of the world. In other words, Republic of india and southeast Asia.

oviparous

reproduction in which eggs are released past the female person; development of offspring occurs outside the mother'south body.

ovoviviparous

reproduction in which eggs develop within the maternal body without additional nourishment from the parent and hatch inside the parent or immediately subsequently laying.

parthenogenic

development takes place in an unfertilized egg

pheromones

chemicals released into air or h2o that are detected by and responded to by other animals of the same species

polygynous

having more than i female person every bit a mate at once

rainforest

rainforests, both temperate and tropical, are dominated by trees often forming a closed awning with little calorie-free reaching the ground. Epiphytes and climbing plants are as well abundant. Precipitation is typically not limiting, but may be somewhat seasonal.

scrub woods

scrub forests develop in areas that experience dry seasons.

seasonal breeding

breeding is bars to a particular season

sedentary

remains in the aforementioned area

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

tactile

uses touch to communicate

temperate

that region of the World between 23.5 degrees North and 60 degrees Due north (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and sixty degrees South (between the Tropic of Capricorn and the Antarctic Circumvolve).

terrestrial

Living on the basis.

tropical

the region of the earth that surrounds the equator, from 23.five degrees north to 23.5 degrees south.

tropical savanna and grassland

A terrestrial biome. Savannas are grasslands with scattered individual trees that exercise not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Commonwealth of australia.

savanna

A grassland with scattered trees or scattered clumps of copse, a type of community intermediate between grassland and woods. See also Tropical savanna and grassland biome.

temperate grassland

A terrestrial biome plant in temperate latitudes (>23.5° N or Southward latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the corporeality of wet bachelor. Fire and grazing are important in the long-term maintenance of grasslands.

visual

uses sight to communicate

viviparous

reproduction in which fertilization and development take identify inside the female body and the developing embryo derives nourishment from the female.

year-circular breeding

breeding takes place throughout the year

References

2010. "Velvet Worm" (On-line). Australian Museum. Accessed March 22, 2013 at http://australianmuseum.net.au/Velvet-worm.

Ballard, J., G. Olsen, D. Organized religion, W. Odgers, D. Rowell, P. Atkinson. 1992. Evidence from 12S ribosomal RNA sequences that onychophorans are modified arthropods. Science, 258: 1345-1348.

Barclay, S., D. Rowell, J. Ash. 2000. Pheromonally mediated colonization patterns in the velvet worm Euperipatoides rowelli (Onychophora). Periodical of Zoology, 250/4: 437-446. Accessed March 22, 2013 at http://journals.cambridge.org/action/displayAbstract?fromPage=online&assistance=40803.

Bergstrom, J., Ten. Hou. 2001. Cambrian Onychophora or Xenusians. Zoologischer Anzeiger, 240: 237-245.

Brusca, R., G. Brusca. 2003. Invertebrates (2d Edition). Sunderland, MA: Sinauer Associates.

Eriksson, B., N. Tait. 2012. Early development in the velvet worm Euperipatoides kanangrensis Reid 1996 (Onychophora: Peripatopsidae). Arthropod Structure and Development, 41/five: 483-493. Accessed March 22, 2013 at http://world wide web.ncbi.nlm.nih.gov/pmc/articles/PMC3437555/.

Leishman, M., M. Eldridge. 1990. Life history characteristics of ii sympatric onychophoran species from the Blueish Mountains, New S Wales. Proceedings of the Linnaean Society of New South Wales, 112: 173-185. Accessed March 22, 2013 at http://biostor.org/reference/68211.

Monge-Nájera, J. 1995. Phylogeny, biogeography and reproductive trends in the Onychophora. Pp. 21-60 in M Walker, D Norman, eds. Onychophora: Past and nowadays, Vol. 114. London, England: Academic Press. Accessed March 22, 2013 at http://www.tropinature.com/biogeo/papers/Phylogeny.pdf.

Monge-Nájera, J., Z. Barrientos, F. Aguilar. 1993. Behavior of Epiperipatus biolleyi (Onychophora: Peripatidae) under laboratory conditions. Revista de Biologica Tropical, 41/3: 689-696. Accessed March 22, 2013 at http://www.tropinature.com/cvitjmn/publications/artcient/onicof/behavior.pdf.

Podsiadlowski, Fifty., A. Braband, G. Mayer. 2008. The complete mitochondrial genome of the onychophoran Epiperipatus biolleyi reveals a unique transfer RNA set and provides further support for the ecdysozoa hypothesis. Molecular Biology and Evolution, 25/1: 42-51.

Read, V. 1988. The Onychophora of Trinidad, Tobago and the Bottom Antilles. Zoological Journal of the Linnaean Guild, 93/3: 225-257. Accessed March 22, 2013 at http://onlinelibrary.wiley.com/doi/10.1111/j.1096-3642.1988.tb01362.10/abstract.

Ruppert, E., R. Fox, R. Barnes. 2004. Invertebrate zoology: A functional evolutionary approach (7th edition). Belmont, CA: Thomson-Brooks/Cole.

Shapiro, L. 2012. "Onychophora: Velvet Worms" (On-line). Encyclopedia of Life. Accessed March 22, 2013 at http://eol.org/pages/6927/overview.

Tait, N., J. Norman. 2001. Novel mating behaviour in Florelliceps stutchburyae gen. november., sp. nov. (Onychophora: Peripatopsidae) from Australia. Periodical of Zoology, 253/3: 301-308.

Telford, M., S. Bourlat, A. Economou, D. Papillon, O. Rota-Stabelli. 2008. The evolution of the Ecdysozoa. Proceedings of the Imperial Lodge B: Biological Sciences, 363: 1529-1537. Accessed March 22, 2013 at http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2614232/.

Waggoner, B. 1999. "Introduction to the Onychophora" (On-line). University of California Museum of Paleontology. Accessed March 22, 2013 at http://www.ucmp.berkeley.edu/onychoph/onychophora.html.

Zhang, Z. 2011. Animal biodiversity: an introduction to college-level nomenclature and taxonomic richness. Zootaxa, 3148: 7-12.

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Source: https://animaldiversity.org/accounts/Onychophora/

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