{{Short description|Genus of parasitic worms}} {{Featured article}} {{Use dmy dates|date=April 2025}} {{Speciesbox | image = Intraproboscis sanghae - 2.jpg | image_alt = Microscope image of the hooked proboscis (long tubular structure with an invagination [the receptacle] about halfway down its length) of a male ''Intraproboscis sanghae'' against a brown background, with an arrow pointing to the outline of the receptacle | image_caption = The proboscis (a tubular organ for attachment to the host's intestinal wall) of a male ''Intraproboscis sanghae'' | parent_authority = Amin, Heckmann, Sist, and Basso 2021<ref name="Amin2021">{{Cite journal |last1=Amin |first1=O. M. |last2=Heckmann |first2=R. A. |last3=Sist |first3=B. |last4=Basso |first4=W. U. |date=2021 |title=A review of the parasite fauna of the black-bellied pangolin, ''Phataginus tetradactyla'' Lin. (Manidae), from central Africa with the description of ''Intraproboscis sanghae'' n. gen., n. sp. (Acanthocephala: Gigantorhynchidae) |journal=The Journal of Parasitology | publisher=Allen Press for the American Society of Parasitologists|volume=107 |issue=2 |pages=222–238 |doi=10.1645/20-126 |pmid=33711161 |url=https://zotero.org/groups/5435545/items/5UXYIEAP }}</ref> | taxon = Intraproboscis sanghae | authority = Amin, Heckmann, Sist, and Basso 2021 | range_map ={{Location map|Africa |relief = yes |caption = The type locality for ''I. sanghae'' is the Dzanga-Sangha Complex of Protected Areas in the extreme southwest part of the Central African Republic.<ref name="Amin2021"/> |label = ''I. sanghae'' |label_width = 9 |lat = 3.6 |long = 16.20 |border = none }} }}
'''''Intraproboscis''''' is a genus of Acanthocephala (thorny-headed or spiny-headed parasitic worms) containing a single known species, '''''Intraproboscis sanghae'''''. Found in central Africa, it infests the black-bellied pangolin and the tree pangolin, which are both threatened with extinction. The genus is described from several females and one incomplete male. Female worms reach up to {{convert|180|mm}} long (mostly trunk) and {{convert|2|mm}} wide; males seem to be smaller in all dimensions.{{#tag:ref|Comparison is made based on a single incomplete male.<ref name="Amin2021b"/>|group=lower-alpha}} The body consists of a long, narrow trunk and a tubular proboscis covered with hooks, which is used for feeding and attachment. The proboscis has 34 to 36 rows of 6 to 7 hooks at the front and 15 to 17 spinelike hooks on the back that are used to pierce and hold the host's intestinal wall.
This genus closely resembles the genus ''Mediorhynchus'' but differs in having mammalian hosts instead of avian hosts, a simple proboscis receptacle that is completely suspended within the proboscis, and a complete lack of neck. The first discovery of a parareceptacle structure, a distinct sac-like structure adjacent to the proboscis receptacle, in the class Archiacanthocephala was from ''Intraproboscis'' and represents an important taxonomic and evolutionary bridge between different acanthocephalan groups.
The life cycle of ''I. sanghae'' remains unknown, but in common with other acanthocephalans, it likely involves a complex life cycle with at least two hosts. The intermediate host of ''Intraproboscis'' has not been definitively identified, but it is believed to be an arthropod, such as an insect. Within this host, the larvae develop into an infectious stage called a cystacanth. When a vertebrate consumes the intermediate host, the cystacanths enter the vertebrate’s intestines where they mature into adult worms and reproduce sexually, and it becomes the definitive host. The resulting eggs are expelled and hatch into new larvae. Infestation by ''I. sanghae'' can cause intestinal perforation and death in the black-bellied pangolin.
==Taxonomy==
''Intraproboscis'' is a genus of acanthocephalans (also called thorny-headed or spiny-headed parasitic worms) containing only the type species, ''I. sanghae''. The genus ''Intraproboscis'' was circumscribed and species ''I. sanghae'' was formally described in 2021 by Amin, Heckmann, Sist, and Basso, from four female specimens extracted from a dead 5-year-old black-bellied pangolin (''Phataginus tetradactyla'').<ref name="Amin2021"/> A second sample which included both females and a single incomplete male was obtained in 2022 from a tree pangolin (''Phataginus tricuspis'').<ref name="Amin2021b"/> The name ''Intraproboscis'' refers to the proboscis receptacle's unusual internal position; ''sanghae'' derives from the Sangha tribal region, a forest divided between the nations of the Central African Republic, Cameroon and the Republic of the Congo, where specimens were collected.<ref name="Amin2021"/>
Six distinct morphological features support ''Intraproboscis''{{'}}s classification within Gigantorhynchidae and distinguish it from the similar genus ''Mediorhynchus''. ''Intraproboscis'' is characterized by: infesting mammals instead of birds, a simple proboscis receptacle that is completely suspended within the proboscis, proboscis retractor muscles that pass through the proboscis receptacle and into the body cavity posteriorly, no neck, a parareceptacle structure (a distinct sac-like structure adjacent to the proboscis receptacle), and a uterine vesicle (a thick-walled, spheroidal compartment between the uterus and the uterine bell, replacing the uterine bell glands and encircled by ducts of unknown function); the last two of these are both absent in ''Mediorhynchus''. As well as morphological differences, an 18S rDNA analysis further confirmed the status of ''Intraproboscis'' as a distinct genus forming a separate lineage from ''Mediorhynchus''.<ref name=Rodriguez2022/> The discovery of a parareceptacle structure in Archiacanthocephala is novel, representing an important taxonomic and evolutionary bridge between different acanthocephalan groups.<ref name="Amin2021"/> Phylogenetic studies have been performed confirming its position in the order Gigantorhynchidae.<ref name="Amin2021"/><ref name=Rodriguez2022>{{Cite journal |last1=Rodríguez |first1=S. M. |last2=Amin |first2=O. M. |last3=Heckmann |first3=R. A. |last4=Sharifdini |first4=M. |last5=D'Elía |first5=G. |date=2022 |title=Phylogeny and life cycles of the Archiacanthocephala with a note on the validity of ''Mediorhynchus gallinarum'' |journal=Acta Parasitologica |publisher = Springer International Publishing (Springer Science + Business Media)|volume=67 |issue=1 |pages=369–379 |doi=10.1007/s11686-021-00472-7|pmid=34618302 }}</ref>
{{cladogram|align=center|title=Archiacanthocephala |caption=Cladogram for select taxa in the class Archiacanthocephala based on a 18S rRNA gene comparison from Rodríguez ''et al.'' (2022).<ref name=Rodriguez2022/> Similar comparisons have been conducted by Gomes ''et al.'' (2019) and Amin ''et al.'' (2020).<ref name="Gomes 2019">{{Cite journal |last1=Nascimento Gomes |first1=Ana Paula |last2=Cesário |first2=Clarice Silva |last3=Olifiers |first3=Natalie |last4=de Cassia Bianchi |first4=Rita |last5=Maldonado |first5=Arnaldo |last6=Vilela |first6=Roberto do Val |date=December 2019 |title=New morphological and genetic data of ''Gigantorhynchus echinodiscus'' (Diesing, 1851) (Acanthocephala: Archiacanthocephala) in the giant anteater ''Myrmecophaga tridactyla'' Linnaeus, 1758 (Pilosa: Myrmecophagidae) |journal=International Journal for Parasitology: Parasites and Wildlife |publisher=Elsevier (for the Australian Society for Parasitology)|volume=10 |pages=281–288 |doi=10.1016/j.ijppaw.2019.09.008 |pmc=6906829 |pmid=31867208 |doi-access=free|bibcode=2019IJPPW..10..281N }}</ref><ref name="Amin2020">{{Cite journal |last1=Amin |first1=O. M. |last2=Sharifdini |first2=M. |last3=Heckmann |first3=R. A. |last4=Zarean |first4=M. |year=2020 |title=New perspectives on ''Nephridiacanthus major'' (Acanthocephala: Oligacanthorhynchidae) collected from hedgehogs in Iran |journal=Journal of Helminthology |publisher=Cambridge University Press|volume=94 |article-number=e133 |doi=10.1017/S0022149X20000073 |pmid=32114988 |s2cid=211725160}}</ref> |cladogram= {{clade |label1=Archiacanthocephala |1={{clade |1={{clade |label1=Oligacanthorhynchidae |1={{clade |1=''Macracanthorhynchus ingens'' |2=''Nephridiacanthus major'' |3=''Oncicola'' sp. }} |label2=Moniliformidae |2={{clade |1=''Moniliformis moniliformis'' }} |label3=Gigantorhynchidae |3={{clade |1={{clade |1=''Mediorhynchus gallinarum'' |2=''Mediorhynchus africanus'' }} |2=''Mediorhynchus grandis'' }} |label4=Gigantorhynchidae |4={{clade |1='''''Intraproboscis sanghae''''' }} }} }} }} }}
==Description== {|class="wikitable floatright" style="text-align: center; font-size: 85%;" |+ Anatomical measurements of ''I. sanghae'' |- ! scope="col" | Measurements<ref name="Amin2021"/> ! scope="col" |Female (mm) ! scope="col" |Male (mm)<ref name="Amin2021b"/>{{#tag:ref|Based on an incomplete male from a seized illegal shipment of tree pangolins from an unknown location in central Africa<ref name="Amin2021b"/>|group=lower-alpha}} |- ! scope="row" |Length of proboscis ||1.56–1.87||1.37 |- ! scope="row" |Width of proboscis ||0.27–0.41 (anterior)<br />0.58–0.74 (posterior)||0.29 (anterior)<br />0.44 (posterior) |- ! scope="row" |Length of proboscis receptacle ||0.77–1.04||0.68 |- ! scope="row" |Width of proboscis receptacle ||0.26–0.36||0.21 |- ! scope="row" |Length of trunk ||63.75–180.00||94.25 |- ! scope="row" |Max width of trunk ||1.12–2.00||1.5 |- ! scope="row" |Cephalic ganglion ||166–229 x 60–100||208 x 94 |- ! scope="row" |Length of lemnisci ||2.08–3.28||4.00 |- ! scope="row" |Width of lemnisci ||0.22–0.38||0.42 |- ! scope="row" |Size of eggs ||0.068–0.083 x 0.038–0.052|| |- ! scope="row" |Size of testes ||||2.90 x 0.60 (anterior)<br />1.32 x 0.55(posterior) |- ! scope="row" |Anterior trunk to anterior testis ||||88.25 |- |} thumb|alt=Two black-and-white line drawings of parasitic worms (''Intraproboscis sanghae''). On the left is a female with the focus on the proboscis and its hooks, and on the right is a male where the whole worm is present and lines showing segmentation are shown on the trunk.|'''Left''': Anterior region of a female ''I.{{nbsp}}sanghae'' showing the retracted anterior proboscis, posteriorly positioned proboscis receptacle, and insertion points for the lemniscus and receptacle; '''Right''': Incomplete male ''I.{{nbsp}}sanghae'' displaying distinct pseudo-segmentation and an everted structure.<ref name="Amin2021b"/> ''I. sanghae'' consists of a proboscis (a tubular organ for attachment to the host's intestinal wall), a proboscis receptacle (a complex structure for housing the proboscis when retracted), and a long and narrow trunk that lacks spines and shows noticeable pseudosegmentation (false divisions resembling segments).<ref name="Amin2021"/> The original description is based on a sample of four pregnant female worms, and was supplemented with a second sample which included both females and a single incomplete male.<ref name="Amin2021b"/> The worms are up to 180 mm long, virtually all of which is the trunk, and 2 mm wide.<ref name="Amin2021"/> There is pronounced sexual dimorphism with the female being larger in all measurements: the sampled male body is 94.25 mm long and 1.5 mm wide.<ref name="Amin2021b"/> The body wall of ''I. sanghae'' is much thicker on the dorsal side compared to the ventral side and contains many fragmented nuclei and a few large nuclei located at the front.<ref name="Amin2021"/>
The proboscis has a truncated cone shape which is cylindrical at the front and conical at the back. The anterior proboscis has two sensory pores (small openings for detecting stimuli) at the tip and many hooks arranged in longitudinal rows. The posterior part also has hooks, with spines forming dome-shaped folds in the tegument (outer body covering). The roots of the hooks (anchor-like extensions) are about as long as the hook blades. Specifically, the proboscis is armed with 34 to 36 rows (32 in the male sample)<ref name="Amin2021b"/> of 6 to 7 tightly packed hooks anteriorly and 15–17 more widely spaced spinelike hooks posteriorly which are used to attach themselves to the intestines of the host. The hooks in the anterior proboscis increase in size as they go down the proboscis. At the apex in the female samples, they are 38–44 μm long by 9–11 μm wide whereas they are 40–50 μm long by 12–14 μm wide in the middle of the proboscis, and 47–54 μm long by 15–16 μm wide at base of the proboscis. The spinelike hooks in the posterior proboscis are more or less similar in size being 20–25 μm long by 5–7 μm wide.<ref name="Amin2021"/> In the male sample, the anterior hooks are 33 μm long by 8 μm wide, the middle hooks are 37 μm long by 11 μm wide, and the posterior hooks are 42 μm long by 13 μm wide. The spinelike hooks in the posterior proboscis are 18 μm long by 4 μm wide.<ref name="Amin2021b"/>
The proboscis receptacle is simple in structure, entirely contained within the proboscis, and has a single layer that is thicker on the dorsal side. It is cylindrical but becomes narrower at the back and widens at the front, attaching at the division between the anterior and posterior portions of the proboscis. Retractor muscles (muscles used to pull the proboscis back) pass through its back end. A large, elliptical cerebral ganglion (a mass of nerve cells acting as a brain) is located near the rear of the receptacle. There is one parareceptacle structure (a secondary attachment structure that is 520–624 μm long) connecting the ventral body wall at the front and the receptacle at the back.<ref name="Amin2021"/>
The organism has no neck. The lemnisci (bundles of sensory nerve fibers) are long, flat, and wide, located at the front of the body within the posterior proboscis, and contain 8 or 9 large nuclei.<ref name="Amin2021"/>
The reproductive system is compact and well developed, with a round uterine vesicle (average size: 387 μm long by 322 μm wide) which stores and transports eggs. This vesicle has anterior and lateral lobes, is encircled by complex tubules of unknown function, and is connected to a large funnel-like uterine bell which directs the eggs. The glandular structures typically found in related species are missing, as is a terminal gonopore (external opening for reproductive discharge). The eggs are oval, with concentric shells (layered coverings); the outer shell is thinner at the poles and is always enclosed within a ligament sac (a protective sac) supported by prominent ligament strands.<ref name="Amin2021"/>
==Distribution== {{multiple image | width = 200 | image1 = Long-tailed Pangolin area.png | alt1 = Map showing the range of a host for ''I. sanghae'', the black-bellied pangolin | image2 = Distribution M. tricuspis.svg | alt2 = Map showing the range of a host for ''I. sanghae'', the tree pangolin | footer = '''Left''': Range of the black-bellied pangolin;<ref name="iucn"/> '''Right''': Range of the tree pangolin,<ref name="iucn2"/> hosts of ''I. sanghae'' }}
The distribution of ''I. sanghae'' is determined by that of its hosts, of which two are known. The black-bellied pangolin (''Phataginus tetradactyla'') is a vulnerable species<ref name="iucn"/> which is at high risk of extinction in the wild.<ref name=Sist2021/> An infested specimen was found in the Dzanga-Sangha Complex of Protected Areas, the type locality, located in the extreme southwest part of the Central African Republic.<ref name="Amin2021"/> This host is native to parts of western and central Africa, having been found as far west and north as Senegal, across the continent to the western border of Uganda, and south into the northern border of Angola. They are found in areas such as the Congo Basin and Guinean forests. There is a distinct gap in the populations with no record of individuals from southwest Ghana through to western Nigeria.<ref name="iucn">{{cite iucn |author=Ingram, D.J. |author2=Shirley, M.H. |author3=Pietersen, D. |author4=Godwill Ichu, I. |author5=Sodeinde, O. |author6=Moumbolou, C. |author7=Hoffmann, M. |author8=Gudehus, M. |author9=Challender, D. |date=2019 |title=''Phataginus tetradactyla'' |volume=2019 |article-number=e.T12766A123586126 |doi=10.2305/IUCN.UK.2019-3.RLTS.T12766A123586126.en |access-date=19 November 2021}}</ref>
The tree pangolin (''Phataginus tricuspis''), which is an endangered species at high risk of extinction,<ref name="iucn2"/> is also a host.<ref name=Amin2021b>{{cite journal |last=Amin |first=Omar M. |year=2022 |title=Amending the description of ''Intraproboscis sanghae'' Amin, Heckmann, Sist, Basso, 2021 (Acanthocephala: Gigantorhynchidae) from a new host, ''Phataginus tricuspis'' Rafinesque in central Africa |journal=International Journal of Zoology and Animal Biology |publisher=MedWin Publishers| volume=5 |issue=6 |pages=1–7 |doi=10.23880/izab-16000429 |url=https://medwinpublishers.com/IZAB/amending-the-description-of-intraproboscis-sanghae-amin-heckmann-sist-basso-2021-acanthocephala-gigantorhynchidae-from-a-new-host-phataginus-tricuspis-rafinesque-in-central-africa.pdf}} </ref> It is native to large portions of central Africa, as far west as Guinea-Bissau in west Africa, as far east as south-western Kenya and north-western Tanzania, and as far south as north-western Zambia and northern Angola.<ref name="iucn2">{{cite iucn |author=Pietersen, D. |author2=Moumbolou, C. |author3=Ingram, D.J. |author4=Soewu, D. |author5=Jansen, R. |author6=Sodeinde, O. |author7=Keboy Mov Linkey Iflankoy, C. |author8=Challender, D. |author9=Shirley, M.H. |date=2019 |title=''Phataginus tricuspis'' |volume=2019 |article-number=e.T12767A123586469 |doi=10.2305/IUCN.UK.2019-3.RLTS.T12767A123586469.en |access-date=19 November 2021}}</ref>
==Hosts and pathology== [[File:Acanthocephala LifeCycle lg.jpg|thumb|left|alt=Diagram of the life cycle of Acanthocephala showing the egg on the bottom, an arrow pointing to the left to the intermediate host (an insect), then an arrow to the top showing the juvenile form, then an arrow to the right showing a human and other animals with the adult form of the parasite, then an arrow pointing back to the egg.|Life cycle of Acanthocephala<ref>{{cite web | url = https://www.cdc.gov/dpdx/acanthocephaliasis/index.html | title = Acanthocephaliasis | last = CDC's Division of Parasitic Diseases and Malaria | date = April 11, 2019 | publisher = Centers for Disease Control and Prevention | access-date = July 17, 2023 | quote = | archive-date = 8 June 2023 | archive-url = https://web.archive.org/web/20230608133736/https://www.cdc.gov/dpdx/acanthocephaliasis/index.html | url-status = live }}</ref>{{#tag:ref|A 2001 survey of the literature found no known cases of human infection by ''I. sanghae''.<ref name="Mathison2021"/>|group=lower-alpha}}]]
The specific life cycle of ''Intraproboscis'' is unknown, but the life cycle of acanthocephala (thorny-headed worms) 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.<ref name=Schmidt1985>{{cite book | last1 = Schmidt | first1 = Gerald D. | last2 = Nickol | first2 = Brent B. | date = 1985 | title = Biology of the Acanthocephala | chapter = Development and life cycles | url = https://core.ac.uk/download/pdf/17218255.pdf | location = Cambridge | publisher = Cambridge University Press | pages = 273–305 | isbn = 978-0521246743 | access-date = 16 July 2023 | archive-date = 22 July 2023 | archive-url = https://web.archive.org/web/20230722191034/https://core.ac.uk/download/pdf/17218255.pdf | url-status = live }}</ref> Although the specific intermediate hosts for the genus ''Intraproboscis'' are unidentified, it is generally accepted that insects serve as the primary intermediaries as they make up the diet of the host.<ref name=Schmidt1985/>
{{multiple image | total_width = 300 | direction = horizontal | image1 = Manis tetradactyla (29645778336).jpg | alt1 = A black-bellied pangolin on a tree branch at night | image2 = Tree pangolin (Phataginus tricuspis) Nyamebe Bepo.jpg | alt2 = A tree pangolin on a tree branch at night | footer = The black-bellied pangolin (left) is the definitive host of ''I. sanghae''. The second host of ''I. sanghae'' discovered is the tree pangolin (right). }}
Inside the intermediate host, the acanthor molts its outer layer, becoming an acanthella (the immature larval stage).<ref name="Mathison2021"/> At this stage it burrows into the host's intestinal wall and continues to grow.<ref name="Amin2021"/> The life cycle culminates in the formation of a cystacanth, a larval stage able to infect the definitive host while retaining juvenile features (differing from the adult only in size and stage of sexual development), which awaits ingestion by the definitive host to mature fully. Once inside the definitive host, these larvae attach themselves to the intestinal wall using the hooks on their proboscis, mature into sexually reproductive adults, and complete the cycle by releasing new acanthors into the host's feces.<ref name="Mathison2021"/>
''I. sanghae'' is known to parasitize two species of pangolin: the black-bellied pangolin, the type host, and the tree pangolin.<ref name="Amin2021b"/> They have been found perforating the intestine, invading the body cavity, and causing secondary septic peritonitis (an infection of the peritoneum, the thin tissue lining the abdomen, that is caused by the parasite). The cause of death for the sampled host was intestinal perforation.<ref name=Sist2021>{{cite journal |last1=Sist |first1=B. |last2=Basso |first2=W. |last3=Hemphill |first3=A. |last4=Cassidy |first4=T. |last5=Cassidy |first5=R. |last6=Gudehus |first6=M. |year=2021 |title=Case report: intestinal perforation and secondary peritonitis due to Acanthocephala infection in a black-bellied pangolin (''Phataginus tetradactyla'') |journal=Parasitology International |publisher=Elsevier Ireland Ltd (an Elsevier imprint)|volume=80 |article-number=102182 |doi=10.1016/j.parint.2020.102182 |pmid=32889100 |url=https://zotero.org/groups/5435545/items/ACM258L8 }}</ref> A survey of the medical literature published in 2021 did not list ''I. sanghae'' as infecting humans.<ref name="Mathison2021">{{cite journal |last1=Mathison |first1=B. A. |display-authors=etal |title=Human acanthocephaliasis: a thorn in the side of parasite diagnostics |journal=Journal of Clinical Microbiology|publisher=American Society for Microbiology (United States) |date=2021 |volume=59 |issue=11 |article-number=e02691-20 |doi=10.1128/JCM.02691-20 |pmid=34076470 |pmc=8525584 }}</ref>
==Notes== {{notelist}}
==References== {{reflist}}
{{Taxonbar|from1=Q120751513|from2=Q129496410}}
Category:Archiacanthocephala Category:Monotypic protostome genera Category:Parasitic animals of mammals Category:Invertebrates of Africa Category:Taxa described in 2021