{ "export": { "source": "https://urth.darkrealm.vip/thread/urth/3056", "note": "Exported from an unofficial mirror of a public mailing list. Copyright in each message remains with the person who wrote it. Email addresses are obscured as `user at host`, the form the original archive published. This file was rebuilt from parsed fields rather than retained headers, so it is faithful in content but not byte-exact.", "addresses": "obscured as 'user at host'" }, "archive": "urth", "thread": { "id": 3056, "subject": "other limb causes", "messages": 2, "voices": 2, "first": "2002-03-20T02:44:21+00:00", "last": "2002-03-20T12:19:10+00:00" }, "messages": [ { "message_id": "", "from": { "name": "maa32", "address": "maa32 at dana.ucc.nau.edu" }, "date": "2002-03-20T02:44:21+00:00", "subject": "(urth) other limb causes", "in_reply_to": null, "reply_link": null, "blocks": [ { "kind": "text", "depth": 0, "text": "Hey, Jerry. Thanks for looking into that stuff more thouroughly. Here is \nsomething else: trematodes that cause extra limbs in X Leavis. (Anyone not \ninterested in this should definitely skip this - it just involves extra limbs \nin frogs)\n\nOf especial note is the statement:\n\n\"The predominant observed limb deformity in both amphibian species was \nmirror-image\nduplication\"\n\n \n(skip if not interested)\nEvidence that Trematodes Cause\n Deformities, including Extra Limbs, in\n Amphibians\n\n Stanley K. Sessions\n\n Department of Biology\n Hartwick College\n Oneonta, NY 13820\n SessionsS at Hartwick.edu\n\n\nThe occasional occurrence of high frequencies of limb abnormalities, including \nmissing limbs\nand extra limbs, in natural populations of amphibians has long been a puzzle. \nRecent reports\nsuggest an \"epidemic\" of such anomalies in natural populations of amphibians \nfrom the\ncentral United States. Here I report the discovery of a population from \nnorthern California\nin which such limb abnormalities appear to be caused by a parasitic flatworm \n(trematode:\nManodistomum syntomentera, family Plagiorchiidae) that uses amphibians as \nsecond\nintermediate hosts in a complex life cycle (Fig. 1).\n\nThe primary host is a vertebrate carnivore (especially garter snakes, genus \nThamnophis)\nwhich releases trematode eggs in its feces. The eggs are eaten by pond snails \n(e.g. Physa\nsp.), which serves as the first intermediate host. Within the pond snail, each \negg undergoes\nat least two rounds of \"polyembryonic amplification\", generating hundreds or \nthousands of\nfree-swimming cercarial trematode larvae. The cercariae attack larval \namphibians (in this\ncase, Pacific treefrogs, Hyla regilla, and Long-toed Salamanders, Ambystoma\nmacrodactylum), aggressively boring into the skin to form cysts \n(metacercariae, (Fig. 2)),\nbut are apparently unable to penetrate the skin of adult metamorphosed Hyla. \nThe cysts are\nnonrandomly localized around the mouth, the cloaca, and the exposed developing \nhind limb\nbuds of the amphibian larvae (Fig. 3).\n\nApproximately 72% of a total of 280 tadpoles and young froglets, presented a \nwide range\nof limb, including missing limbs or parts of limbs, fused skin, ectopic limb \nstructures, and\nduplicated limb structures ranging from extra digits to several extra whole \nlimbs (Fig. 4),\nTable 1). A similar range of deformities was observed in approximately 40% of \na sample of\n4,148 captured and released larval and newly metamorphosed salamanders, and\napproximately 5% of a sample of 1,778 captured and released adult salamanders \n(Tables\n3,4,&5).\n\nThe predominant observed limb deformity in both amphibian species was \nmirror-image\nduplication (Fig. 5), suggesting massive disruption of the positional \nrelationships of cells in\nthe developing limb bud (Fig. 6). I hypothesized that these limb abnormalities \nresult from\nlocalized regulatory responses of developing and regenerating limb tissues to \nmechanical\ndisruption of normal limb pattern forming mechanisms caused by the trematode \ncysts. This\nidea was experimentally confirmed by microsurgically implanting inert resin \nbeads into\ndeveloping limb buds of lab-raised frogs (Xenopus laevis) and salamanders \n(Ambystoma\nmexicanum), a treatment that causes the development of supernumerary limb \nstructures\nand other deformities (Fig. 7).\n\nI conclude that trematode cyst infestation is sufficient to cause the majority \nof observed\ndeformities in natural populations of amphibians. I think that the occurrence \nof such\nphenotypic anomalies in natural populations of amphibians probably reflects a \nsporadic and\nlocalized natural phenomenon, especially fluctuations in pond snail \npopulations (Fig. 8).\nFrogs and trematodes have probably been co-evolving through shifts in the \ntiming of their\ndevelopmental stages, an ancient phenomenon dating back millions of years. \nThese\npossibilities should be explored in all reported but unexplained occurrences \nof a high\nfrequency of limb deformities in natural populations of amphibians.\n\nhttp://www.mp1-pwrc.usgs.gov/naamp3/papers/54/54df.html\n\nHopefully he won't mind me ripping off his paper ...\n\nMarc" } ] }, { "message_id": "", "from": { "name": "matthew.malthouse", "address": "matthew.malthouse at guardian.co.uk" }, "date": "2002-03-20T12:19:10+00:00", "subject": "Re: (urth) other limb causes", "in_reply_to": "", "reply_link": "subject", "blocks": [ { "kind": "quote", "depth": 1, "text": "On 20/03/2002 02:44:21 maa32 wrote:\nI hypothesized that these limb abnormalities result from\nlocalized regulatory responses of developing and regenerating limb\ntissues to mechanical\ndisruption of normal limb pattern forming mechanisms caused by the\ntrematode cysts. This\nidea was experimentally confirmed by microsurgically implanting inert\nresin beads into\ndeveloping limb buds of lab-raised frogs (Xenopus laevis) and salamanders\n(Ambystoma\nmexicanum), a treatment that causes the development of supernumerary limb\nstructures and other deformities" }, { "kind": "text", "depth": 0, "text": "How does this mechanical intervention support your theories of polyploidy?\n It seems irrelevant to either the support of or refutation of the\ntheories you have advanced.\n\nMatthew" } ] } ] }