Heptamegacanthus

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Heptamegacanthus
Scientific classification Edit this classification
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
type locality for H. niekerki is Nqadu Forest, Transkei, South Africa.[1]

Heptamegacanthus is a

rectal wall of its host, and a short, wide trunk. There are 40 to 45 hooks 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
.

The life cycle of H. niekerki remains unknown; however, like other acanthocephalans, it likely involves

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

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 

protonephridia, which are found in other acanthocephalan species for excretion and water regulation.[1]

The

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

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,

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

Diagram of the life cycle of Acanthocephala
Life cycle of Acanthocephala[4][a]
type host of H. niekerki.[6]

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

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]

References

  1. ^
    S2CID 23497546
    .
  2. PMID 32761142
    . Retrieved 1 April 2024.
  3. ^
    doi:10.2305/IUCN.UK.2015-2.RLTS.T4828A21289898.en
    . Retrieved 12 November 2021.
  4. Center for Disease Control. Archived
    from the original on 8 June 2023. Retrieved 17 July 2023.
  5. ^
    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.
  7. ^ a b 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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