寄生于锯腿树蛙多盘吸虫属单殖吸虫一新种记述

记述了锯腿树蛙多盘吸虫Polystoma carvirostris sp.nov.。新种宿主为锯腿树蛙Rhacophorus carvirostris Guenther,1868,采自云南屏边县。新种中央大钩基部截形,国外近似种大钩基部分叉状。新种虫体全长平均5·07mm,体型小于屏边多盘吸虫Polystoma pingbianensis和斑腿树蛙多盘吸虫P.leucomystax。新种肠管内侧盲肠分支多数过腹中线,且于中后部交叉联合成网状;屏边多盘吸虫P.pingbianensis肠管内侧盲肠分支多数过中线,仅1个肠联合;斑腿树蛙多盘吸虫P.leucomystax肠管内侧盲肠分支均过中线,肠联合与分支肠管交错排列。     

华西雨蛙寄生多盘虫科单殖吸虫一新种

在云南省新平县(24°N,101°32’E)采集的华西雨蛙Hyla a.annectans膀胱内检获多盘虫属1新种,新平多盘虫Polystoma xinpingensis sp.nov.。124只华西雨蛙中18只华西雨蛙感染,自然感染率为14.5%。新种与多盘虫属记录种最显著的区别在于:虫体体型小,其体长仅为2967μm。内侧肠管于虫体后1/3处仅形成2条横跨虫体的联合肠管,其它记录种肠管分支多数或形成较复杂的网状。睾丸巨大,呈滤泡状,分散分布直达虫体中部。新种的正、副模式标本保存在云南师范大学生命科学学院。     

无声囊泛树蛙寄生多盘虫属单殖吸虫一新种

从海南尖峰岭的无声囊泛树蛙Polypedates mutus膀胱内检获多盘虫属Polystoma单殖吸虫1新种,以宿主种名命名为无声囊泛树蛙多盘虫Polystoma mutus sp.nov.。新种以后吸器长相对于虫体全长较小(1.0:7.9～1.0:8.2),锚钩形态,具9根生殖棘等特征而区别于近似种。本种为海南岛多盘虫属单殖吸虫的首次报道。模式标本保存于华南师范大学生命科学学院鱼类寄生虫学研究室。     

滇蛙体内寄生单殖吸虫一新种记述

从滇蛙Rana pleuraden Boulenger膀胱内检获单殖吸虫多盘科双睾属1新种,以采集地命名为石林双睾虫Diplorchis shilinensis sp.nov.,新种为目前国内记录双睾属吸虫中体型最小的虫种.描述了新种的形态特征,并与近似种做了比较.新种模式标本保存于云南师范大学生命科学学院动物学教研室.     

海南大绿臭蛙寄生双睾虫属一新种(单殖吸虫纲,多盘虫科)

从海南五指山的大绿臭蛙Ranalivida膀胱内检获多盘科Polysto matidae双睾虫属Diplorchis单殖吸虫1新种,以宿主种名命名为大绿臭蛙双睾虫Diplorchis lividae sp.nov.。新种以肠支侧突明显而区别于蛙双睾虫、拉氏双睾虫和无指盘臭蛙双睾虫;与石林双睾虫的区别是本种的肠支末端进入后吸器;本种中央大钩的形状与杭州双睾虫的大钩基部具深裂的缺刻明显不同;与黑斑蛙双睾虫的区别是本种中央大钩的内突上附有向前延伸的长条形肌腱,另本种卵巢较小、长度与卵相近,而黑斑蛙双睾虫的卵巢长度超过卵长的一倍。本种为海南多盘类单殖吸虫的首次报道。模式标本保存于华南师范大学生命科学学院鱼类寄生虫研究室。     

无指盘臭蛙体内寄生双睾虫属多盘吸虫一新种

于云南一平浪镇无指盘臭蛙Rana grahami Boulenger膀胱内检获单殖吸虫多盘科双睾虫属l新种,以宿主名命名为无指盘臭蛙双睾虫Diplorchis grahami sp. Nov..检查36只无指盘臭蛙,感染率为19.4%,感染虫体1～94枚,平均感染强度为31,相对密度为6.02.新种模式标本具有典型双睾属多盘吸虫的特征:消化道两侧均未形成肠盲突,末端不形成联合,不延伸进入后吸器.阴道孔隆起明显,子宫具升支和降支,向后延伸至后吸器内.卵黄腺发达,滤泡状,沿肠管两侧分布至后吸器内.生殖棘7枚排列为冠状.本双睾虫体长平均4.627 mm,虫体最宽处平均1.611mm,与黑斑蛙双睾虫、拉氏双睾虫和杭州双睾虫均属于大型虫体,但新种的几丁质结构与上述3种已记录的双睾虫存在显著差异,其后吸器相对较小,平均为0.681 mm×1.178mm,吸盘直径平均284.22μm,大钩较小,平均295.87μm,X/Y为1.255;但与小型的石林双睾虫比较,大钩X/Y值差异不显著.     

基于28S rDNA C1-D2区的鳞盘虫科单殖吸虫系统学初步研究

首次利用核糖体28S rDNA C1-D2区序列对鳞盘虫科开展初步的系统学分析,探讨鳞盘虫科各亚科是否成立及其相互关系,并考察鳞盘虫属的单系性问题.结果表明:1)寄生在黄姑鱼Nibea albiflora上的Sinodiplectanotrema属虫种与鳞盘虫科虫种表现出较近的亲缘关系,因虫种后吸器不具鳞盘,故应纳入鳞盘虫科4亚科之一的Murraytrematoidinae亚科;2)本研究不支持Murraytrematoidinae亚科的单系性,并支持Doumingous(2004)废除Murraytrematoidinae亚科并将其中的Lobotrema和Murraytrema二属归入Diplectaninae亚科这一做法;3)对于Doumingous(2004)所提议的新Diplectaninae亚科是否为单系群需进一步探讨;4)本研究支持Lamellodiscinae亚科的单系性;5)7种鳞盘虫属虫种的分析结果显示鳞盘虫属具有明显的非单系性.今后需要将形态学分析和分子系统学分析结合起来,通过分析更多的虫种,才有可能理解鳞盘虫属及鳞盘虫科其它种类的适应辐射问题.     

寄生于杜氏泛树蛙多盘虫属单殖吸虫一新种记述

于云南屏边县杜氏泛树蛙Polypedates dugritei David膀胱内检获单殖吸虫多盘科多盘虫属1新种:屏边多盘吸虫Polystoma pingbianensis sp.nov.,对其形态结构及宿主特异性问题进行了初步研究.据宿主膀胱内寄生的产卵成虫测量形态分类数据和描述鉴定特征.虫体全长平均9.428 mm,后吸器大小平均0.869 mm×0.784 mm,后吸器吸盘的直径平均434.4μm,后吸器上两个中央大钩全长平均403.2μm.朝向外侧肠管无盲突,朝向内侧肠管每侧形成13～14个盲突,有1个或无过腹中线的肠联合,肠管于后端合并向后延伸至后吸器内,不形成盲突.卵巢较小,位于单个睾丸之前,卵巢长平均711.52 μm.卵相对较大,卵长平均306.6μm,卵宽平均164.6μm.     

尖吻鲈寄生拟合片虫属一新种描述(单殖吸虫纲,鳞盘虫科)

描述了采自广东省阳江市海水网箱养殖尖吻鲈鳃上寄生的单殖吸虫鳞盘虫科Diplectanidae Bychowsky,1957、拟合片虫属Pseudorhabdosynochus Yamaguti,1958中的1新种,文中量度μm,模式标本保存于中山大学华南寄生生物研究中心.     

黑斑蛙重盘吸虫的线粒体基因组特征及其系统发育研究

重盘科Diplodiscidae Cohn, 1904复殖吸虫是两栖动物最为常见的寄生虫,形态多样,目前未见基于线粒体基因组的遗传多样性研究。本研究记述并分析了寄生于滇蛙Dianrana pleuraden肠道的重盘科重盘属Diplodiscus Diesing, 1836黑斑蛙重盘吸虫D.nigromaculati的线粒体全基因组序列,为后续开展此类吸虫的遗传结构及遗传多样性研究提供了新的数据。黑斑蛙重盘吸虫线粒体基因组全长14 697 bp(GenBank登录号：MW698822),由22个tRNA基因、12个蛋白编码基因、2个rRNA基因和1个非编码区组成;AT含量(60%)高于GC含量(40%),但AT含量为目前已报道同盘总科Paramphistomoidea Fischoeder, 1901中最低;trnG基因和trnE基因的互换成为同盘总科吸虫线粒体基因组遗传结构的重要特征。基于12个蛋白编码基因的系统发育树支持重盘属隶属于重盘科。本研究中,滇蛙为黑斑蛙重盘吸虫的宿主新记录。     

Origin and evolution of African Polystoma (Monogenea: Polystomatidae) assessed by molecular methods

Among Polystomatidae (Monogenea), the genus Polystoma, which mainly infests neobatrachian hosts, is the most diverse and occurs principally in Africa, from where half the species have been reported. Previous molecular phylogenetic studies have shown that this genus originated in South America, and later colonised Eurasia and Africa. No mention was made on dispersal corridors between Europe and Africa or of the origin of the African Polystoma radiation. Therefore, a molecular phylogeny was inferred from ITS1 sequences of 21 taxa comprising two species from America, seven representatives from Europe and 12 from Africa. The topology of the phylogenetic tree reveals that a single event of colonisation took place from Europe to Africa and that the putative host carrying along the ancestral polystome is to be found among ancestral pelobatids. Percentage divergences estimates suggest that some presumably distinct vesicular species in unrelated South African anurans and some neotenic forms found in several distinct hosts in Ivory Coast, could, in fact, belong to two single polystome species parasitising divergent hosts. Two main factors are identified that may explain the diversity of African polystomes: (i), we propose that following some degree of generalism, at least during the juvenile stages of both hosts and parasites, distinctive larval behaviour of polystomes engenders isolation between parasite populations that precludes sympatric speciations; (ii), cospeciation events between Ptychadena hosts and their parasites are another factor of diversification of Polystoma on the African continent. Finally, we discuss the systematic status of the Madagascan parasite Metapolystoma, as well as the colonisation of Madagascar by the host Ptychadena mascareniensis.     

A Paedomorphic parasite associated with a neotenic amphibian host: phylogenetic evidence suggests a revised systematic position for Sphyranuridae within anuran and turtle Polystomatoineans

The phylogenetic relationships of the families Polystomatidae and Sphyranuridae (subclass Polystomatoinea) within tetrapod monogenean parasites were investigated using partial 18S rDNA sequences. About 600 nucleotides of 11 species were sequenced, including 7 species of the most common subfamilies of Polystomatidae found in anurans and turtles, 1 species of the family Sphyranuridae parasitizing exclusively urodelans, and 3 species of the subclass Oligonchoinea infesting teleostean fishes. The phylogenetic analyses were performed using three reconstruction methods: neighbor-joining, maximum-parsimony, and maximum-likelihood. Polystomatoineans but not polystomatids were shown to be monophyletic. Within the polystomatoineans there are two clades: one includes the amphibian monogeneans (anuran polystomatids and urodelan sphyranurids) and the other includes the turtle polystomatids. Polystomatoineans may have coevolved with amphibian hosts, and an ancestral "polystome" dispersed at least 200 million years ago, either from the basal stem of lissamphibians or from an anuran ancestral stock, to freshwater turtles. Furthermore, the urodelan genus Sphyranura, initially assigned to the family Sphyranuridae on the basis of morphological and ontogenetic evidence, is clearly nested within polystomatids, suggesting that its systematic status must be revised. This supports recent findings which argue that species of the family Sphyranuridae may be paedomorphic parasites exclusively infesting neotenic mudpuppies.     

Polystoma gallieni: Experimental evidence for chemical cues for developmental plasticity

Among monogeneans that display direct life cycles, plastic developmental strategies may have been selected to counter the lack of transmission opportunities. Within amphibian polystomatids, some species of the genus Polystoma develop into two different phenotypes depending on the host physiological stage to which free swimming larvae attach. When oncomiracidia infest old tadpoles, they develop slowly and migrate during host metamorphosis towards the bladder where they reach maturity. On the other hand when larvae infest young tadpoles, they develop rapidly into neotenic phenotypes that reproduce in the branchial chamber. These alternative developments are explored through experimental infestations with Polystoma gallieni, the specific polystome of the stripeless tree frog Hyla meridionalis. When oncomiracidia were left for 6 h in water in which young tadpoles had been previously maintained for one day, they mainly developed into the neotenic phenotype regardless of the tadpole stage they encountered later. This indicates that P. gallieni could collect released host-derived signals before physical contact with its host.     

Historical biogeography of amphibian parasites, genus Polystoma (Monogenea: Polystomatidae)

Aim  The present-day geographical distribution of parasites with a direct biological life cycle is guided mostly by the past dispersal and vicariance events that have affected their hosts. The Amphibia– Polystoma association (which satisfies these criteria) also exhibits original traits, such as host specificity and world-wide distribution. This biological model was thus chosen to investigate the common historical biogeography of its widespread representatives.
Location  North and South America, Eurasia and Africa.
Methods  We investigated the phylogeny of 12 species of neobatrachian parasites sampled from North and South America, Eurasia and Africa. Hosts belonged mostly to hyloids and ranoids of families Bufonidae, Hylidae, Leptodactylidae, Ranidae and Hyperoliidae. Phylogenetic reconstructions were inferred from maximum likelihood and maximum parsimony analyses from complete ITS1 sequences.
Results  The group of American species appeared paraphyletic with one species at the base of a Eurafrican clade, within which two lineages were seen: one composed of only Eurasian species, and the other of European and African species, with the two European species basal to an African clade.
Main conclusions  The route of Polystoma evolution is deduced from the phylogenetic tree and discussed in the light of host evolution. We conclude that Polystoma originated in South America on hyloids, after the separation of South America from Africa. The genus must have colonized North America in Palaeocene times and Eurasia by the mid-Cainozoic, taking advantage of the dispersal of either ancestral bufonids or hylids. Africa, however, appears to have been colonized more recently, during the Messinian period.     

Syntopic occurrence of new species ofPolystoma andMetapolystoma (Monogenea: Polystomatidae) inPtychadena porosissima in South Africa

Polystoma sodwanensis n. sp. andMetapolystoma porosissimae n. sp. are described as new species of the Polystomatidae parasitic in the urinary bladder of adultPtychadena porosissima collected in northern Natal, South Africa. Of 26 frogs examined, 11 host individuals were infected with one of the two parasite species, while in five both parasite species occurred. This is the first record of two different genera of polystomatids occurring together in one host species and the first record ofMetapolystoma in South Africa. The exceptional nature of the reported double infection is discussed in terms of host specificity within the Polystomatidae. Relevant information is given on the ecology and distribution of the host,Ptychadena porosissima.To whom correspondence should be addressed.     

The influence of climate on the distribution of monogeneans of anurans in Nigeria

Investigations undertaken on the monogeneans of amphibians in Nigeria have shown that host ecology has an influence on the distribution of these monogeneans. Amphibians from humid environments of the rainforest, a freshwater swamp and mangrove harboured no monogeneans, whereas those occurring in drier conditions in the savannah-mosaic and guinea savannah yielded five species of polystomatid parasites: Polystoma prudhoei from Bufo regularis, Polystoma galamensis from Rana galamensis, Eupolystoma alluaudi from Bufo regularis and Bufo maculatus, and two unidentified Polystoma species from Bufo regularis and Ptychadena oxyrynchus, respectively. Some of these monogeneans appear to have reproduction cycles which are synchronized with those of the hosts. The prevalence of E. alluaudi in Bufo spp. caught in New Bussa (68.4% in B. regularis and 82.3% in B. maculatus) were higher than those reported for this parasite in other locations in West Africa and for Eupolystoma anterorchis in Bufo pardalis from the Cape Flats of South Africa.     

Origin and evolution of alternative developmental strategies in amphibious sarcopterygian parasites (Platyhelminthes, Monogenea, Polystomatidae)

Most integrative studies involving phylogenetic, developmental and ecological trends showed that the diversity of developmental modifications among the Platyhelminthes was linked to transmission opportunity pressures. For parasitic flatworms with complex life cycles it was suggested that the evolutionary forces that constrained or enhanced developmental strategies implied heterochronic patterns. Similar patterns were also reported from the Monogenea with direct life cycles, especially for Polystomatidae, which infest amphibious Sarcopterygians. Polystoma, whose members are recovered almost exclusively from anuran hosts of the Neobatrachia, is capable of following two alternative developmental strategies depending on the physiological stage of its host. Processes by which parasites reach maturity are strikingly different, and lead to discrete adult phenotypes within the same parasite species. In the present study, we investigate the origin and evolution of developmental patterns of polystomatids in a phylogenetic framework, using an integrative approach of heterochrony and evolutionary ecology. The results suggest that both phenotypes have coexisted during the early stages of polystome evolution, and that neither of them can be considered as the ancestral one. The two developmental pathways, each associated with one life cycle, may have arisen independently prior to polystome diversification, when strictly aquatic sarcopterygians attempted colonization of temporary freshwater environments. The occurrence of these two patterns within species of the genus Polystoma is suggested to reflect the ancestral condition, and to have allowed both developmental strategies to be successful depending on shifts in transmission opportunities. Thus, host evolutionary ecology may be the main factor in shaping developmental strategies within polystomatids.     

A view of early vertebrate evolution inferred from the phylogeny of polystome parasites (Monogenea: Polystomatidae)

The Polystomatidae is the only family within the Monogenea to parasitize sarcopterygians such as the Australian lungfish Neoceratodus poisteri and freshwater tetrapods (lissamphibians and chelonians). We present a phylogeny based on partial 18S rDNA sequences of 26 species of Polystomatidae and three taxon from the infrasubclass Oligonchoinea (= Polyopisthocotylea) obtained from the gills of teleost fishes. The basal position of the polystome from lungfish within the Polystomatidae suggests that the family arose during the evolutionary transition between actinopterygians and sarcopterygians, ca. 425 million years (Myr) ago. The monophyly of the polystomatid lineages from chelonian and lissamphibian hosts, in addition to estimates of the divergence times, indicate that polystomatids from turtles radiated ca. 191 Myr ago, following a switch from an aquatic amniote presumed to be extinct to turtles, which diversified in the Upper Triassic. Within polystomatids from lissamphibians, we observe a polytomy of four lineages, namely caudatan, neobatrachian, pelobatid and pipid polystomatid lineages, which occurred ca. 246 Myr ago according to molecular divergence-time estimates. This suggests that the first polystomatids of amphibians originated during the evolution and diversification of lissamphibian orders and suborders ca. 250 Myr ago. Finally, we report a vicariance event between two major groups of neobatrachian polystomes, which is probably linked to the separation of South America from Africa ca. 100 Myr ago.     

A new species of Polystoma (Monogenea: Polystomatidae) parasitic in Hyperolius marmoratus (Anura: Hyperoliidae) in South Africa

Polystoma marmorati n. sp. is described as a new polystomatid species parasitic in the urinary bladder of the painted reed frog Hyperolius marmoratus marmoratus collected in southern Natal, South Africa. Parasite prevalence varied from 14.5 to 47.4% and the mean intensity from 1.0 to 1.1. The hamuli of the new species have a characteristic, partly fragmented appearance, a feature also seen in Polystoma batchvarivi, the only other polystome described from a species of the genus Hyperolius. The similarity between the two species, in spite of their geographical separation, is commented upon.