Heptamegacanthus

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Heptamegacanthus
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Acanthocephala
Class: Archiacanthocephala
Order: Oligacanthorhynchida
Family: Oligacanthorhynchidae
Genus: Heptamegacanthus
Spencer-Jones, 1990 [1]
Species:
H. niekerki
Binomial name
Heptamegacanthus niekerki
Spencer-Jones, 1990
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Red pog.svg
H. niekerki
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The type locality for H. niekerki is Nqadu Forest, Transkei, South Africa. [1]

Heptamegacanthus is a monotypic genus of acanthocephalans (thorny-headed or spiny-headed parasitic worms). It contains a single species, Heptamegacanthus niekerki, parasite of the endangered giant golden mole (Chrysospalax trevelyani) found only in isolated forests near East London and in the Transkei, both 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. There are 40 to 45 of these 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 the 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 with minimal sexual dimorphism.

Contents

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.

Taxonomy

Heptamegacanthus is a monotypic genus of acanthocephalans (also called thorny-headed or spiny-headed parasitic worms). The genus and species Heptamegacanthus niekerki was formally described in 1990 by Mary E. Spencer Jones, curator at the British Museum, from specimens (5 females and 5 males) collected live, preserved, and sent from south-east Africa. The genus name Heptamegacanthus refers to the seven large hooks on its proboscis and the specific name niekerki derives from Jan van Niekerk, who collected the species in the field. [1]

The classification of the genus Heptamegacanthus within the family Oligacanthorhynchidae is supported by six distinct morphological features. Firstly, its proboscis is more or less spherical, and equipped with hooks that feature an anterior strong base (manubrium) and a robust root for attachment. Additionally, sensory papillae on the proboscis enhance its sensory capabilities. The proboscis receptacle, a complex structure for housing the proboscis when retracted, consists of a thin, non-muscular outer layer and a thicker, muscular inner layer, which is pierced dorsally by muscles that retract the proboscis. The lemnisci, which are long, flattened structures containing several giant nuclei, play a role in the worm's sensory system. The presence of eight cement glands, each with a large central nucleus, is another distinguishing feature; these glands produce a substance used in the reproductive process. Finally, the eggs of Heptamegacanthus have an oval shape and distinctly textured outer shell. It differs from other worms in the family Oligacanthorhynchidae mainly by its smaller size, and the number and greater size of hooks in the anterior ring. [1] The National Center for Biotechnology Information does not indicate that any phylogenetic analysis has been published on Heptamegacanthus that would confirm its position as a unique genus in the family Oligacanthorhynchidae. [2]

Description

Heptamegacanthus niekerki consists of a proboscis covered in hooks, a proboscis receptacle, and a trunk with a length twice that of the width. Sexual dimorphism is minimal, with the male being 3.49–4.23 mm long by 1.42–2.14 mm wide, only slightly larger than female at 3.15–3.59 mm long by 1.53–1.94 mm wide. This is unusual for acanthocephalans where the female is usually much larger than the male, but has been found in other acanthocephalans including Corynosoma . Heptamegacanthus is also very small for a member of the family Oligacanthorhynchidae. Although acanthocephalans are able to survive in accidental hosts without completing their devoplemented rendering them smaller than normal, this dwarfism has been ruled out for Heptamegacanthus as the samples collected were mature and females contained eggs indicating that the giant golden mole (Chrysospalax trevelyani) is a definitive and not a paratenic (organism that harbors the sexually immature parasites) or accidental host. [1]

The proboscis is nearly spherical being 256–381  μm long and 435–604 μm wide in males and 281–381 μm long and 416–635 μm wide in females. It is armed with 40 to 45 hooks that are not radially symmetrical, with seven large anterior hooks. The hooks come in four distinct types: the first two rings of hooks have large bases (manubria) and roots, with the hooks in the very front (243–275 μm long in males and 256–297 μm long in females) being twice the size of those in the second row (81–180 μm long in males 103–199 μm long in females). Hooks towards the rear are spine-like, tapering to smaller sizes (43–84 μm to 28–52 μm long in males and 34–71 μm to 31–58 μm long in females long in males). One sensory papilla is present on each side of neck and on the apex of the proboscis. The proboscis receptacle originates on the body wall at about one quarter of body-length from the anterior end of the worm. The proboscis receptacle is single walled, having a small, non-muscular layer and inner large, muscular wall with well-developed retractor muscles penetrating the receptacle wall dorsally. The brain is located in the mid-region of the proboscis receptacle. The lemnisci (bundles of sensory nerve fibers) are long, extending nearly half the body length, flat, and contain several giant nuclei (0.832–1.635 mm long and 89–333 μm wide in the female). The worm does not have protonephridia, which are found in other acanthocephalan species for excretion and water regulation. [1]

The testes of the male are large and tilted, 409 to 832 μm long and 204 to 525 μm wide, and are positioned towards the front half of the body before the central (pre-equatorial) dividing line. During copulation, the male injects semen from its seminal vesicle into the copulatory bursa (a fluid filled sac). The Saefftigen's pouch (a muscular sac 832–877 μm long and 236–365 μm wide) then contracts, ejecting fluid causing the eversion of the copulatory bursa. The shape of the copulatory bursa grips the female during copulation. There are eight pre-equatorial cement glands that are 281–404 μm long and 243–436 μm wide, which are used to temporarily close the posterior end of the female after copulation, each with a single giant nucleus. [1]

Females have a short, muscular reproductive system, including a uterine bell (a funnel like opening continuous with the uterus) that is large and short (179–218 μm long to 140–173 μm wide), a uterus (396–461 μm long and 166–224 μm wide), and a vagina (102–186 μm long and 32–173 μm diameter). Females produce numerous oval eggs that are 56–96 μm long and 43–52 μm wide with highly sculptured outer shells, stored in a space called the pseudocoel. [1]

Distribution

The distribution of H. niekerki is determined by that of its host, the giant golden mole. Heptamegacanthus niekerki has been found in South-East Africa in the Nqadu Forest, Transkei, South Africa, the type locality. The giant golden mole's range is very limited, being an endangered species, [3] and consists only of isolated forest ranges in Pirie Forest and Komgha near King William's Town, East London, and Port St. Johns in the Transkei. [1] The giant golden mole, and thus H. niekerki, is threatened primarily by the urbanization of the East London area causing fragmentation of forests and subsequent habitat loss. The forests are also being degraded by the exploitation of the forest for firewood, bark, timber harvesting and livestock overgrazing/trampling. [3]

Hosts

Life cycle of Acanthocephala Acanthocephala LifeCycle lg.jpg
Life cycle of Acanthocephala
The giant golden mole is the type host of H. niekerki. NHM Chrysospalax trevelyani (cropped).JPG
The giant golden mole is the type host of H. niekerki.

The specific life cycle of Heptamegacanthus is unknown but the life cycle of any thorny-headed worm, or acanthocephalan, 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. [7] Although the specific intermediate hosts for the genus Heptamegacanthus remain unidentified, it is generally accepted that, for the broader order Oligacanthorhynchida to which it belongs, insects serve as the primary intermediaries. [7] Once inside the intermediate host, the acanthor sheds its outer layer in a process called molting, transitioning into its next stage, the acanthella. [5] At this stage, which for H. niekerki measures between 38–60 μm in length and 19–26 μm in width, it burrows into the host's intestinal wall and continues to grow. [1] The life cycle culminates in the formation of a cystacanth, a larval stage that retains juvenile features (differing from the adult only in size and stage of sexual development) and awaits ingestion by the definitive host to mature fully. Once inside the definitive host, these larvae attach themselves to the intestinal walls, mature into sexually reproductive adults, and complete the cycle by releasing new acanthors into the host's feces. [5]

Heptamegacanthus niekerki has been found attached to the wall of the rectum in the giant golden mole. [1] There are no known paratenic hosts where Heptamegacanthus might reside without undergoing further development or reproduction. There are no reported cases of H. niekerki infesting humans in the English language medical literature. [5]

Notes

  1. ↑ There are no known aberrant human infections for H. niekerki species. [5]

Related Research Articles

<span class="mw-page-title-main">Giant golden mole</span> Species of mammal

The giant golden mole is a small mammal found in Africa. At 23 centimetres (9.1 in) in length, it is the largest of the golden mole species. This mole has dark, glossy brown fur; the name golden comes from the Greek word for green-gold, the family Chrysochloridae name.

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.

<i>Gigantorhynchus</i> Genus of parasitic worms

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.

<i>Moniliformis</i> Genus of worms

Moniliformis is a genus of parasitic worms in the Acanthocephala phylum.

Promoniliformis is a monotypic genus of acanthocephalans containing a single species, Promoniliformis ovocristatus, that infests tenrecs in Madagascar. The genus PromoniliformisDollfus and Golvan, 1963 is characterized by possessing two distinct kinds of proboscis hooks. There is only one species in this genus.

<span class="mw-page-title-main">Oligacanthorhynchidae</span> Order of thorny-headed worms

Oligacanthorhynchida is an order containing a single parasitic worm family, Oligacanthorhynchidae, that attach themselves to the intestinal wall of terrestrial vertebrates.

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.

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.

<i>Pachysentis</i> Genus of worms

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.

<i>Oncicola</i> Genus of worms

Oncicola is a genus of parasitic worms belonging to the family Oligacanthorhynchidae. Oncicola belongs to the phylum Acanthocephalans that include many thorny-headed worms. This family contains 12 genera including the genus Oncicola. Oncicola is a part of the phylum Acanthocephalans that include many thorny-headed worms. The name comes from the prefix onc- meaning “barbed” and -cola meaning “to inhabit” in Latin. It was named and discovered in 1916 by Travassos. These worms are defined by their parasitic nature which involves hook structures found at their front end.

<i>Macracanthorhynchus</i> Genus of thorny-headed worms

Macracanthorhynchus, also known as the giant thorny-headed worm of swine, is a member of the Oligacanthorhynchidae which contains four species.

Multisentis is a monotypic genus of acanthocephalans. It contains a single species, Multisentis myrmecobius , parasite of the numbat from which it derives its species name. It was found in south-western Australia.

Neoncicola is a genus of parasitic worms containing nine species and belongs to the family Oligacanthorhynchidae.

Oligacanthorhynchus is a genus of parasitic worms belonging to the family Oligacanthorhynchidae.

Atactorhynchus is a genus in Acanthocephala which contains two species, A. verecundus and A. duranguensis.

Cathayacanthus is a genus in Acanthocephala.

Pararaosentis is a monotypic genus of acanthocephalans containing a single species, Pararaosentis golvani.

Triaspiron is a monotypic genus of acanthocephalans containing a single species, Triaspiron aphanii.

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.

References

  1. 1 2 3 4 5 6 7 8 9 10 11 Jones, Mary E. Spencer (1990). "Heptamegacanthus niekerki n. g., n. sp. (Acanthocephala: Oligacanthorhynchidae) from the south-east African insectivore Chrysospalax trevelyani (Günther, 1875)". Systematic Parasitology. 15 (2): 133–140. doi:10.1007/BF00009991. S2CID   23497546.
  2. ↑ Schoch, Conrad L; Ciufo, Stacy; Domrachev, Mikhail; Hotton, Carol L; Kannan, Sivakumar; Khovanskaya, Rogneda; Leipe, Detlef; Mcveigh, Richard; O’Neill, Kathleen; Robbertse, Barbara; Sharma, Shobha; Soussov, Vladimir; Sullivan, John P; Sun, Lu; Turner, Seán; Karsch-Mizrachi, Ilene (2020). "NCBI Taxonomy: a comprehensive update on curation, resources and tools". Database : The Journal of Biological Databases and Curation. NCBI. doi:10.1093/database/baaa062. PMC   7408187 . PMID   32761142 . Retrieved 1 April 2024.
  3. 1 2 Bronner, Gary Neil (2015). "Chrysospalax trevelyani". IUCN Red List of Threatened Species . 2015: e.T4828A21289898. doi: 10.2305/IUCN.UK.2015-2.RLTS.T4828A21289898.en . Retrieved 12 November 2021.
  4. ↑ CDC’s Division of Parasitic Diseases and Malaria (11 April 2019). "Acanthocephaliasis". www.cdc.gov. Center for Disease Control. Archived from the original on 8 June 2023. Retrieved 17 July 2023.
  5. 1 2 3 4 Mathison, Blaine A.; Ninad, Mehta; Couturier, Marc Roger (2021). "Human acanthocephaliasis: a thorn in the side of parasite diagnostics". Journal of Clinical Microbiology. 59 (11): e02691-20. doi:10.1128/JCM.02691-20. PMC   8525584 . PMID   34076470.
  6. ↑ Halajian, A; Smales, LR; Tavakol, S; Smit, NJ; Luus-Powell, WJ (2018). "Checklist of Acanthocephalan parasites of South Africa". ZooKeys (789): 1–18. Bibcode:2018ZooK..789....1H. doi: 10.3897/zookeys.789.27710 . PMC   6193052 . PMID   30344432.
  7. 1 2 Schmidt, Gerald D.; Nickol, Brent B. (1985). "Development and life cycles". Biology of the Acanthocephala (PDF). Cambridge: Cambridge University Press. pp. 273–305. Archived (PDF) from the original on 22 July 2023. Retrieved 16 July 2023.
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