Pachysentis

The genus Pachysentis was established with three species by Anton Meyer in 1931, with P. canicola designated as the type species. Phylogenetic analyses have also been conducted on Oncicola, a genus morphologically nearly identical to Pachysentis apart from the number of hooks on the proboscis, and have also placed it in the family Oligacanthorhynchidae. ==Description==

Pachysentis looks identical to the closely related Oncicola apart from the number of hooks on the proboscis. Species of Oncicola have 36 or fewer hooks whereas species of Pachysentis have more. The probosces of Pachysentis species are not quite spherical and contain 42 to 102 hooks arranged into 12 longitudinal rows of 3 to 12 hooks each. Depending on the species, the rows may be regularly or irregularly alternating and straight or crooked. Hooks have tips with or without barbs, and the larger hooks with complex heads (manubria) and roots with the remaining spines being rootless. The trunk is around twice as long as wide with the anterior half usually wider than the posterior half. The testes are in tandem with at least one located before the middle of the worm. There are eight cement glands compactly arranged each with a single giant nucleus used to temporarily close the posterior end of the female after copulation. The eggs have a sculptured outer membrane. Species can be distinguished based on the number and arrangements of proboscis hooks, whether these hooks are barbed, the arrangement of the cement glands, host, and the length of lemnisci (bundles of sensory nerve fibers). ==Species==

The genus Pachysentis contains eleven species, although P. septemserialis is of uncertain taxonomic status. • Pachysentis angolensis (Golvan, 1957) P. angolensis was found infesting the side-striped jackal (Canis adustus). The proboscis has a total of 42 hooks without barbs in 12 regularly alternating rows of three and four hooks (six rows of each). the golden jackal (Canis aureus) also in Iran, captive maned wolves (Chrysocyon brachyurus) in a zoo in Texas, and the striped skunk (Mephitis mephitis) found nearby. It was also found infesting the western diamondback rattlesnake (Crotalus atrox), a Paratenic hosts (hosts where parasites infest but do not undergo larval development or sexual reproduction). It is the type species of the genus Pachysentis. It is named after the parasitologist Robert-Philippe Dollfus. This species is named after Christian Gottfried Ehrenberg who was a pioneer in the study of microorganisms in the 19th century, and had a role in collecting the original type specimens. • Pachysentis gethi (Machado-Filho, 1950) P. gethi was originally described in 1950 by Machado-Filho infesting tayra (Eira barbara) in Pará and Rio de Janeiro, Brazil but this remained the only record until it was rediscovered in 2016 infesting the wild lesser grison (Galictis cuja), also in Rio de Janeiro, with smaller measurements. The proboscis has 42 hooks without barbs arranged into six rows of four hooks followed by six rows of three hooks. The eight cement glands occur in pairs. • Pachysentis procyonis (Machado-Filho, 1950) The proboscis has 42 hooks without barbs arranged into six rows of four hooks followed by six rows of three hooks. Distinguishing features include eight clustered cement glands and very short lemnisci that do not reach the anterior testis. The proboscis is armed with 42 hooks without barbs arranged into six rows of four hooks each followed by six rows of three hooks each. This species can be identified by its clustered cement glands and long leminisci that reach the anterior testis. and the absence of samples or measurements of adult males. Morphologically, new observations by Gomes et al. in 2019 suggest it is synonymous with P. lenti. Specifically, the original description of one paratype described the lack of a collar at the base of the proboscis whereas a collar was observed in the paratype by Gomes et al. in 2019 (suggesting affiliation with the genus Prosthenorchis). A second discrepancy from another paratype is the number of hooks; 12 longitudinal rows of four hooks with total of 48 hooks were observed by Gomes et al. in 2019 but contradicts the seven rows of seven hooks with a total of 49 hooks given in the original description by Machado-Filho in 1950. The name septemserialis refers to the seven rows one after the other (in series). ==Distribution==

The nearly cosmopolitan distribution of Pachysentis species is determined by that of its many hosts. Pachysentis species have been found in South America (Brazil), Africa (Egypt and Angola), and Asia (Egypt and Iran). ==Hosts==

|Life cycle of Acanthocephala The life cycle an acanthocephalan in general unfolds in three distinct stages. It begins when an egg develops into an infective form known as an acanthor. This acanthor is released with the feces of its definitive host, typically a vertebrate, and must be ingested by an intermediate host, an arthropod such as an insect, to continue its development. The intermediate hosts of Pachysentis species are not known, though one research group speculates that the intermediate hosts of P. canicola are beetles or cockroaches. Inside the intermediate host, the acanthor molts its outer layer, becoming an acanthella (the immature larval stage). File:Side-striped Jackal (Canis adustus)- rare sighting of this nocturnal animal ... (13799300905).jpg|alt=A side-striped jackal walking in front of grass|The side-striped jackal is one of the hosts of P. angolensis. File:Fox - British Wildlife Centre (17429406401).jpg|alt=A red fox walking on grass|The red fox is one of the hosts of P. canicola and P. procumbens. File:Common brown lemur (Eulemur fulvus) male.jpg|alt=A Common brown lemur on the side of a tree branch|The common brown lemur is one of the hosts of P. dollfusi. File:Tayra - Male, Brazil.jpg|alt=A Tayra on a grassy field|The tayra is one of the hosts of P. gethi. File:Nasenbaer Nasua nasua Zoo Augsburg-04.jpg|alt=A South American coati on a branch in a forest|The South American coati is one of the hosts of P. louroi. File:Geoffroy's Marmoset 1.jpg|alt=A White-headed marmoset on a tree|The white-headed marmoset is one of the hosts of P. lenti. File:CostaRica ManuelAntonioNationalPark Racoon (pixinn.net).jpg|alt=A crab-eating racoon eating a fruit on a beach|The crab-eating raccoon is one of the hosts of P. procyonis. File:Sapajus libidinosus paraguayanus.jpg|alt=Azaras's capuchin on a branch in a forest|The Azaras's capuchin is one of the hosts of P. rugosus. File:Crotalus atrox USFWS.jpg|alt=Western diamondback rattlesnake in grass in a threatening pose|The western diamondback rattlesnake is a paratenic host of P. canicola. File:Naja haje (1).jpg|alt=Head of the Egyptian cobra|The Egyptian cobra is a paratenic host of P. ehrenbergi. ==Notes==