Johnson Pieter T J, Calhoun Dana M, Achatz Tyler J, Greiman Stephen E, Gestos Adrian, Keeley William H
Ecology and Evolutionary Biology, University of Colorado, Boulder, CO, USA.
Department of Natural Sciences, Middle Georgia State University, Macon, GA, 31206, USA.
Int J Parasitol Parasites Wildl. 2024 Jul 14;24:100965. doi: 10.1016/j.ijppaw.2024.100965. eCollection 2024 Aug.
The detection of severe limb malformations in metamorphosing northern leopard frogs () from a Colorado pond in August 2022 prompted questions about the cause(s) and concern over the implications. Northern leopard frogs, which are a Tier 1 Species of Greatest Conservation Need in Colorado, have declined over much of their range in the state, particularly along the Front Range. Although malformations in amphibians have been reported in other parts of the USA, they are rare in Colorado, and the current case represents the most severe hotspot reported in the state for over 70 years. Across three survey events in late summer and early fall of 2022, approximately 68% of captured leopard frogs (late-stage larvae and metamorphic frogs) exhibited one or more malformations. Malformations exclusively affected the hind limbs and were dominated by skin webbings (51.7% of the total), bony triangles (32.2%), and extra limbs or digits (11%). Many animals had multiple malformations that limited the movement of one or both limbs (average of 2.3 malformations per malformed frog). Dissection of a subset of animals coupled with 28S rDNA genetic sequencing revealed the occurrence of the trematode at an average of 75.2 trematode cysts (metacercariae) per frog. The parasite was also detected in 2.6% of dissected snails (), which function as the trematode's first intermediate host. The relatively high loads of infection detected here - coupled with the similarity of observed malformations to those previously linked to in experimental studies and from other malformation hotspots in the USA - offer compelling evidence that the current case is the result of parasite infection. Unresolved questions include why malformation prevalence was so high in 2022 and the degree to which such abnormalities will affect population persistence for local leopard frogs, particularly if malformations continue.
2022年8月，在科罗拉多州一个池塘中对正在变态的北方豹蛙（）进行检查时，发现了严重的肢体畸形，这引发了人们对病因的疑问以及对其影响的担忧。北方豹蛙是科罗拉多州最需要保护的一级物种，在该州大部分分布范围内数量都有所下降，尤其是在山前地带。虽然美国其他地区曾报告过两栖动物畸形现象，但在科罗拉多州较为罕见，而此次事件是该州70多年来报告的最严重的畸形热点地区。在2022年夏末和秋初的三次调查活动中，大约68%被捕获的豹蛙（晚期幼虫和变态期青蛙）出现了一种或多种畸形。畸形仅影响后肢，主要表现为皮肤蹼（占总数的51.7%）、骨质三角（32.2%）和多余的肢体或趾头（11%）。许多动物有多种畸形，限制了一个或两个肢体的活动（每只畸形青蛙平均有2.3种畸形）。对一部分动物进行解剖并结合28S rDNA基因测序发现，每只青蛙平均有75.2个吸虫囊肿（尾蚴）。在2.6%的解剖蜗牛（）中也检测到了这种寄生虫，蜗牛是该吸虫的第一中间宿主。此处检测到的相对较高的感染负荷，以及观察到的畸形与实验研究和美国其他畸形热点地区先前与相关的畸形的相似性，提供了有力证据表明此次事件是寄生虫感染的结果。尚未解决的问题包括为什么2022年畸形发生率如此之高，以及这种异常将在多大程度上影响当地豹蛙的种群持续性，特别是如果畸形现象持续存在的话。
