Featured Article Summary #139

Intraproboscis is a genus of spiny-headed parasitic worms (Acanthocephala) with only one known species, Intraproboscis sanghae. It lives in central Africa and infects two threatened pangolins—the black-bellied pangolin and the tree pangolin. The female worms can grow up to 180 mm long, and they have a long trunk and a tubular proboscis covered in hooks used to attach to and feed from the host’s intestine. This genus is similar to Mediorhynchus, but it differs in its mammal hosts, the structure of its proboscis receptacle, and the absence of a neck. Although the exact life cycle of I. sanghae is unknown, it likely uses at least two hosts: an arthropod intermediate host where larvae form cystacanths, and a vertebrate definitive host where the worms mature and reproduce. In pangolins, infection can damage the intestines, sometimes causing perforation and death. Intraproboscis is a genus of thorny-headed parasitic worms with only one known species, I. sanghae. It was described in 2021 from female worms taken from a dead 5-year-old black-bellied pangolin, with additional specimens found in 2022 from a tree pangolin. The name “Intraproboscis” comes from the unusual placement of its proboscis receptacle, and its anatomy includes several distinctive features that separate it from the similar genus Mediorhynchus, confirmed by genetic (18S rDNA) and phylogenetic analyses. The discovery of a parareceptacle in this group is also considered a new, important evolutionary link between different acanthocephalan groups. I. sanghae is an intraproboscis worm with a proboscis, a receptacle that holds the proboscis when it retracts, and a long trunk showing faint false segmentation; females are larger than males. The proboscis is covered with many hooked and spinelike structures used to attach to the host’s intestine, while the proboscis receptacle has specialized muscles and nerve tissue. Its reproductive system is compact, with a well-developed egg-storage uterine vesicle and oval eggs with layered shells, but it lacks some glandular structures and a typical external reproductive opening. I. sanghae lives wherever its hosts live, and two host pangolin species are known. An infested black-bellied pangolin was found in the Dzanga-Sangha Complex in the Central African Republic, a vulnerable pangolin species spread across western and central Africa, though it has a population gap from southwest Ghana to western Nigeria. The tree pangolin is also a host; it is endangered and ranges widely through central Africa, from Guinea-Bissau to Kenya and Tanzania, and south to Zambia and northern Angola. The life cycle of Intraproboscis is not fully known, but acanthocephalan (thorny-headed worm) cycles usually begin with eggs released in a vertebrate host’s feces, which become infective forms eaten by an insect intermediate host. Inside the insect, the larvae develop, form a cystacanth, and are then eaten by the vertebrate, where they attach to the intestine, mature, and release new infective eggs in feces. I. sanghae has been found in pangolins, where it can perforate the intestine, spread into the body cavity, and cause severe peritoneum infections, with death linked to intestinal perforation; it has not been reported infecting humans in medical literature up to 2021.