| Atactorhynchus | |
|---|---|
Scientific classification  | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Acanthocephala |
| Class: | Eoacanthocephala |
| Order: | Neoechinorhynchida |
| Family: | Neoechinorhynchidae |
| Genus: | Atactorhynchus Chandler, 1935 [1] |
| Type species | |
| Atactorhynchus verecundus Chandler, 1935 [1] | |
| Other species | |
| |
Atactorhynchus is a genus in Acanthocephala (thorny-headed worms, also known as spiny-headed worms) which contains two species, A. verecundus and A. duranguensis.
The genus was described by Chandler in 1935 who gave it a new genus as it was the only genera in the family Neoechinorhynchidae with more than four horizontal rows of hooks on the proboscis apart from Tanaorhamphus (which has a large and long proboscis with 20 or more transverse rows of large hooks and a body that is cylindrical or enlarged anteriorly) and Pandosentis (which has a short cylindrical proboscis with hooks that are not U-shaped but bent at right angles, very short lemnisci, and short retractor muscles). [1] Phylogenetic analysis has been performed on A. duranguensis [2]
Atactorhynchus species consist of a proboscis covered in very irregularly arranged hooks and a trunk. The proboscis is very small and armed with about eight diagonally transverse rows of hooks with about eight hooks in anterior rows, and about twice as many hooks that are half as large in the posterior rows. The hooks are U-shaped, with large rod-shaped roots and slender spines with only the tips projecting through the cuticle. The proboscis sac is about twice as long as the proboscis. [1]
The body is small, stout, ventrally curved, with greatest diameter behind the middle. The retractor muscles for the proboscis sac are attached behind middle of body. The lemnisci are very long and large, extending about to middle of body, one containing one nucleus, the other two. The testes are large, more or less spherical ad contiguous. The syncytial cement gland, which are used to temporarily close the posterior end of the female after copulation, are in contact with testes. There is a seminal vesicle with two ducts and a well-developed cement reservoir. [1]
The genus AtactorhynchusChandler, 1935 contains two species.
A. duranguensis has been found in the intestine of the Mezquital pupfish (Cyprinodon meeki) from in-land near Durango, Mexico. The body is small, stout, ventrally curved; small cylindrical proboscis armed with 16 alternating vertical rows of four or five hooks; anterior two or three hooks are conspicuous, stout and larger than other hooks, and have large, rod-shaped roots with a markedly and abruptly enlarged base; three posterior hooks of each row are smaller and rootless; single-walled proboscis receptacle; lemnisci equal in length, elongate and robust; and cement gland syncytial, larger than testis. A. duranguensis is smaller than A. verecundus with smaller hook lengths and slightly smaller proboscis. A. duranguensis is also shaped differently: it has a proboscis shape that is not widest at the apex, and the greatest width of the trunk is in about the middle contrasting A. verecundus where the trunk is widest posteriorly, and the proportion of large apical proboscis hooks in relation to the small basal hooks is different: the basal hooks of A. verecundus are about half the size of the anterior hooks and but only about a quarter of the size in A. duranguensis. Unlike A. verecundus, the base of the roots are markedly and abruptly enlarged in the new species. Finally, the eggs of the new species are smaller (23-27 x 8-10 um) than those of A. verecundus (27-30 x 12-13 um). [3]
A. verecundus was found in the intestines of about 30 to 40 percent of the sampled Sheepshead minnow (Cyprinodon variegatus) in upper parts of Galveston Bay in very large numbers in some hosts. Very few A. verecundus were found from hosts sampled near Galveston Island. [1]
The proboscis is very small and nearly cylindrical, but slightly expanded distally, about 0.15 mm long and 0.06 mm in diameter. The proboscis is covered in hooks arranged irregularly in about eight diagonally transverse rows. The first four or five rows occupy the anterior two-thirds of proboscis, with about eight hooks each. The last two or three rows are smaller but with more hooks with the last row having about 16, which are about half the size of anterior hooks. The hooks are U-shaped, with broad, bluntly rounded roots and slender sharp points, with only the tips projecting through the cuticle. Measured from top of bend both points and roots about 18um to 19um long in hooks at the anterior end of the proboscis and only 9um to l0um long for the hooks of the posterior row. [1]
Behind the proboscis, the body tapers posteriorly until it is bluntly rounded with the maximum diameter behind middle of body. The body contains a proboscis sac about twice length of the proboscis. The retractor muscles of the proboscis sac are long and slender and attached behind the middle of body, so that the anterior end of body can be retracted. The lemnisci are long (about half length of body) and in males terminate at about anterior margin of anterior testis. [1]
There is sexual dimorphism in this species with the females up to 6.5 mm in length, with maximum diameter about 0.63 mm and the males up to 4.5 long, with maximum diameter of 0.6 mm. The testes (300um to 400m long and about two-thirds as wide) are in the posterior half of body and contiguous. Syncytial cement glands are just behind the testes and roughly the same in size. The cement reservoir is bag-shaped and located just behind cement gland. The seminal vesicle is rounded, dorsal to anterior end of cement reservoir, and connected with genital aperture by two ducts. In the female, the eggs in uterus are 27um to 30um long and 12um to 13um wide. [1]
The distribution of Atactorhynchus is determined by that of its hosts. They were found in Galveston Bay [1] and in-land near Durango. [3]
The life cycle of an acanthocephalan consists of three stages beginning when an infective acanthor (development of an egg) is released from the intestines of the definitive host and then ingested by an arthropod, the intermediate host. Although the intermediate hosts of Atactorhynchus are not known, they are always an arthropod. When the acanthor molts, the second stage called the acanthella begins. This stage involves penetrating the wall of the mesenteron or the intestine of the intermediate host and growing. The final stage is the infective cystacanth which is the larval or juvenile state of an Acanthocephalan, differing from the adult only in size and stage of sexual development. The cystacanths within the intermediate hosts are consumed by the definitive host, usually attaching to the walls of the intestines, and as adults they reproduce sexually in the intestines. The acanthor is passed in the feces of the definitive host and the cycle repeats. There may be paratenic hosts (hosts where parasites infest but do not undergo larval development or sexual reproduction) for Atactorhynchus. [6]
Atactorhynchus parasitizes animals. There are no reported cases of Atactorhynchus infesting humans in the English language medical literature. [5]
Acanthocephala is a group of parasitic worms known as acanthocephalans, thorny-headed worms, or spiny-headed worms, characterized by the presence of an eversible proboscis, armed with spines, which it uses to pierce and hold the gut wall of its host. Acanthocephalans have complex life cycles, involving at least two hosts, which may include invertebrates, fish, amphibians, birds, and mammals. About 1420 species have been described.
Apororhynchus is a genus of small parasitic spiny-headed worms. It is the only genus in the family Apororhynchidae, which in turn is the only member of the order Apororhynchida. A lack of features commonly found in the phylum Acanthocephala suggests an evolutionary branching from the other three orders of class Archiacanthocephala; however no genetic analysis has been completed to determine the evolutionary relationship between species. The distinguishing features of this order among archiacanthocephalans is a highly enlarged proboscis which contain small hooks. The musculature around the proboscis is also structured differently in this order. This genus contains six species that are distributed globally, being collected sporadically in Hawaii, Europe, North America, South America, and Asia. These worms exclusively parasitize birds by attaching themselves around the cloaca using their hook-covered proboscis. The bird hosts are of different orders, including owls, waders, and passerines. Infestation by an Apororhynchus species may cause enteritis and anemia.
Gigantorhynchus is a genus of Acanthocephala that parasitize marsupials, anteaters, and possibly baboons by attaching themselves to the intestines using their hook-covered proboscis. Their life cycle includes an egg stage found in host feces, a cystacanth (larval) stage in an intermediate host such as termites, and an adult stage where cystacanths mature in the intestines of the host. This genus is characterized by a cylindrical proboscis with a crown of robust hooks at the apex followed by numerous small hooks on the rest of the proboscis, a long body with pseudosegmentation, filiform lemnisci, and ellipsoid testes. The largest known specimen is the female G. ortizi with a length of around 240 millimetres (9.4 in) and a width of 2 millimetres (0.08 in). Genetic analysis on one species of Gigantorhynchus places it with the related genus Mediorhynchus in the family Gigantorhynchidae. Six species in this genus are distributed across Central and South America and possibly Zimbabwe. Infestation by a Gigantorhynchus species may cause partial obstructions of the intestines, severe lesions of the intestinal wall, and may lead to death.
Mediorhynchus is a genus of small parasitic spiny-headed worms. Phylogenetic analysis has been conducted on two known species of Mediorhynchus and confirmed the placement along with the related genus Gigantorhynchus in the family Gigantorhynchida. The distinguishing features of this order among archiacanthocephalans is a divided proboscis. This genus contains fifty-eight species that are distributed globally. These worms exclusively parasitize birds by attaching themselves around the cloaca using their hook-covered proboscis. The bird hosts are of different orders.
Moniliformidae is a family of parasitic spiny-headed worms. It is the only family in the Moniliformida order and contains three genera: Australiformis containing a single species, Moniliformis containing eighteen species and Promoniliformis containing a single species. Genetic analysis have determined that the clade is monophyletic despite being distributed globally. These worms primarily parasitize mammals, including humans in the case of Moniliformis moniliformis, and occasionally birds by attaching themselves into the intestinal wall using their hook-covered proboscis. The intermediate hosts are mostly cockroaches. The distinguishing features of this order among archiacanthocephalans is the presence of a cylindrical proboscis with long rows of hooks with posteriorly directed roots and proboscis retractor muscles that pierce both the posterior and ventral end or just posterior end of the receptacle. Infestation with Monoliformida species can cause moniliformiasis, an intestinal condition characterized as causing lesions, intestinal distension, perforated ulcers, enteritis, gastritis, crypt hypertrophy, goblet cell hyperplasia, and blockages.
Moniliformis is a genus of parasitic worms in the Acanthocephala phylum.
Oligacanthorhynchida is an order containing a single parasitic worm family, Oligacanthorhynchidae, that attach themselves to the intestinal wall of terrestrial vertebrates.
Arhythmacanthidae is a family of parasitic worms from the order Echinorhynchida.
Dendronucleata is a genus of small parasitic spiny-headed worms. It is the only genus in the family Dendronucleatidae. This genus contains three species that are distributed globally, being collected in North America and Asia. The distinguishing features of this genus among Archiacanthocephalans is the presence of randomly distributed dendritically branched giant hypodermic nuclei. Dendronucleata parasitize freshwater fish and a salamander by attaching themselves in the intestines using their hook covered proboscis and adhesives secreted from cement glands.
Neoechinorhynchidae is a family of parasitic worms from the order Neoechinorhynchida.
Australiformis is a monotypic genus of acanthocephalans containing a single species, Australiformis semoni, that infests marsupials in Australia and New Guinea. Its body consists of a proboscis armed with hooks which it uses to pierce and hold the gut wall of its host, and a long trunk. This genus resembles species in the genus Moniliformis but is characterized by a lack of spiral muscles in the outer wall of the proboscis receptacle. The proboscis is armed with 12 rows of 13 to 15 hooks which are used to attach themselves to the small or large intestines of the host. The female worms range from 95 to 197 millimetres long, virtually all of which is the trunk, and 1.75 to 3.5 millimetres wide. There is pronounced sexual dimorphism in this species as females are around twice the size of the males whose trunks range from 46 to 80 millimetres long and 2 millimetres (0.079 in) wide. Infestation by A. semoni may cause debilitating inflammation of the stomach (gastritis) with granulomatous ulcers.
Heptamegacanthus is a monotypic genus of acanthocephalans. It contains a single species, Heptamegacanthus niekerki, parasite of the endangered giant golden mole found in South Africa. Its body consists of a proboscis armed with hooks which it uses to pierce and hold the rectal wall of its host, and a short, wide trunk. The proboscis is armed with 40 to 45 hooks arranged in rings that are not radially symmetrical, with seven large anterior hooks. The hooks in the anterior ring are twice as large as those in second ring and the remaining hooks decrease progressively in size posteriorly. The worms are about 4 millimetres (0.2 in) long and 2 millimetres (0.08 in) wide. The life cycle of H. niekerki remains unknown; however, like other acanthocephalans, it likely involves complex life cycles with at least two hosts. Although the intermediate host for Heptamegacanthus is not definitively identified, it is presumed to be an arthropod. In this host, the larvae develop into an infectious stage known as a cystacanth. These are then ingested by the definitive host, where they mature and reproduce sexually within the intestines. The resulting eggs are expelled and hatch into new larvae.
Pachysentis is a genus in Acanthocephala that parasitize primates and carnivorans. They are distributed across Africa, the Middle East, and the Americas. Pachysentis species attach themselves to the inner lining of the gastrointestinal tract of their hosts using their hook-covered proboscis. Their life cycle includes an egg stage found in host feces, a cystacanth (larval) stage in an intermediate host such as the Egyptian cobra, and an adult stage where cystacanths mature in the intestines of the host. This genus appears identical to the closely related Oncicola apart from a greater number of hooks on the proboscis. There are eleven species assigned to this genus, although P. septemserialis is of uncertain taxonomic status. The female worms range from 12 millimetres (0.47 in) long and 1.6 millimetres (0.063 in) wide in P. lauroi to 50 millimetres (2.0 in) long and 4 millimetres (0.16 in) wide in P. dollfusi. Virtually all of the length is the trunk, with a short proboscis. There is pronounced sexual dimorphism in this species as females are around twice the size of the males.
Oligacanthorhynchus is a genus of parasitic worms belonging to the family Oligacanthorhynchidae.
Pararaosentis is a monotypic genus of acanthocephalans containing a single species, Pararaosentis golvani.
Raosentis is a genus of Acanthocephala that parasitize the intestine of fish.
Triaspiron is a monotypic genus of acanthocephalans containing a single species, Triaspiron aphanii.
Pallisentis is a genus in Acanthocephala.
Intraproboscis is a monotypic genus of acanthocephalans that infest African black-bellied pangolin in the Central African Republic. Its body consists of a proboscis armed with hooks which it uses to pierce and hold the gut wall of its host, and a long trunk. It contains a single species, Intraproboscis sanghae. This genus resembles species in the genus Mediorhynchus but is characterized by infesting a mammal instead of birds, and having a simple proboscis receptacle that is completely suspended within the proboscis, the passage of the retractor muscles through the receptacle into the body cavity posteriorly, absence of neck, presence of a parareceptacle structure, and a uterine vesicle. The proboscis is armed with 34–36 rows of 6 to 7 hooks anteriorly and 15–17 spinelike hooks posteriorly which are used to attach themselves to the intestines of the host. The female worms are up to 180 millimetres long, virtually all of which is the trunk, and 2 millimetres wide.
Mayarhynchus is a monotypic genus of acanthocephalans containing a single species, Mayarhynchus karlae, that infests animals.
