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Bell Pettigrew Museum of Natural History Interpretative Panels Text: Dr Iain Matthews Design: Steve Smart & Cavan Convery A University of St Andrews Development Fund Project School of Biology http://biology.st-andrews.ac.uk 10:7 Pentastomida P hy l u m Pentastomida S u b p hy l u m Super class Class The pentastomids, or tongue worms, are a small phylum of around 100 species of blood-consuming parasites. The adults of most species parasitize the pulmonary and nasal cavities of predatory vertebrates and 90% of species specifically have reptilian hosts, mainly snakes. The larval stages have a wider range of hosts including insects and humans. Adult pentastomids are generally elongated (measuring 1–20cm in length) and cylindrical with a soft cuticle containing chitin. They have a complete digestive system with a mouth and anus, however they do not posses a respiratory, excretory or circulatory system. The body appears segmented , but this is only superficial, forming distinct annuli or false segments. The anterior end of the body bears sensory papillae and five short protuberances. Four of these are tipped with hooks and are used for attachment to the host. The mouth is located on the fifth protuberance, the snout. The name pentastomid, meaning five mouths, was erroneously based on the belief that each of the protuberances had a mouth. The body, especially in the female, is dominated Body Plan: • Bilaterally symmetrical • Triploblastic • Protostome • Haemocoelic cavity with through gut • Unsegmented with 2 pairs of claw-bearing legs • Lack excretory, circulatory or gaseousexchange organs • Chitonous cuticle forming a soft exoskeleton Gut Endoderm Body Cavity Mesoderm Ectoderm Exoskeleton by the reproductive system and after fertilisation, which is internal, up to 500,000 eggs are released. The primary larval stage develops within the egg, prior to release into the host’s respiratory tract. These are then either sneezed out or swallowed and passed out in the faeces. When a suitable intermediate host ingests the primary larval stage, it hatches, penetrates the intestinal wall and migrates into the abdominal cavity. After several moults the larva metamorphoses into a quiescent nymph. When a determinate host (usually a snake), eats the intermediate host (usually a fish, amphibian, reptile or small mammal) the nymph is released into the digestive tract and then bores into the lungs where it matures. Classification within Pentastomida Class: Pentastomata Order: Cephalobaenida Order: Porocephalida See specimen. Tongue Worms Adult tongue worms all live as parasites in the respiratory tract of vertebrates. Most species live in the lungs of snakes. For a parasite to survive inside a host it has to stop the host’s immune system from attacking it. To avoid detection, pentastomids secrete mucus that has been found to exactly mimic the secretions found in the lungs of their host. This means that the host can’t distinguish the tongue worm from its own lungs. Tongue worms are rare in humans. However eating raw goat or sheep can lead to a condition called halzoun or nasopharyngeal linguatulosis. The symptoms of the disease, common in Lebanon and Sudan, include a severe itching sensation in the ears and throat. Coughing and sneezing can dislodge the nymphs, however if they are not removed they can cause abscesses of the auditory canal, paralysis and death.