鲤肠道寄生岳阳碘泡虫新种的形态特征及系统发育分析

在洞庭湖岳阳地区开展鱼类寄生虫调查中,发现一种寄生于鲤Cyprinus carpio L.肠道的黏孢子虫。该黏孢子虫的孢囊呈白色,椭圆形,大小为(1.0±0.2) mm (0.8—1.2 mm)。成熟孢子具有壳瓣,壳面观近似圆形,后端有4—6个“V”形褶皱;缝面观呈纺锤形,缝脊直而粗;孢质均匀,含有一个嗜碘泡;孢子长(9.8±0.6) μm (9.6—10.0 μm),孢子宽(8.2±0.3) μm (8.0—8.5μm),孢子厚(7.3±0.1) μm (7.0—7.5 μm);2个极囊梨形,位于孢子顶端,大小相等,呈“八”字形;极囊长(4.4±0.4) μm (3.8—5.1 μm),宽(2.7±0.2) μm (2.2—3.2 μm),极丝4—5圈。该黏孢子虫与肠膜碘泡虫、丑陋圆形碘泡形态特征非常相似,但其极囊/孢子小于1/2;与文献已报道的鲤肠道寄生北京碘泡虫和鲤肠碘泡虫相比较,其在孢子形态、孢子和极囊大小方面分别存在明显差异。基于该黏孢子虫18S rDNA基因序列(GenBank登录号KY203795)比对分析,该黏孢子虫与山东碘泡虫相似率最高,仅为96%。系统发育分析发现,该黏孢子虫与山东碘泡虫、倪李碘泡虫、住心碘泡虫、Myxobolus encephalicus、Sphaerospora molnari、多涅茨尾孢虫和Henneguya zikaweiensis聚为独立分支,和其他已报道的黏孢子虫亲缘关系较远。综合形态学和18S rDNA基因序列数据,文章报道的鲤肠道寄生黏孢子虫为碘泡虫属一新物种,将其命名为岳阳碘泡虫。     

海城碘泡虫(黏体动物门，黏孢子纲)补充描述及基于18S rDNA系统发育分析

海城碘泡虫原始描述中形态数据较为简单,且存在多个宿主及寄生部位,其有效性有待确定。利用现行主流的黏孢子虫形态特征和基因标记系统分析相结合的分类学方法,对采自太湖棒花鱼鳃丝的海城碘泡虫进行了补充描述。该碘泡虫孢囊呈白色,圆形,大小为(0.6—1.1) mm。成熟孢子正面观近似椭圆形,上端稍尖,侧面观呈纺锤型,孢子长(10.8±0.7) μm (10.1—11.5 μm),孢子宽:(8.1±0.5) μm (7.5—9.0 μm),孢子厚:(5.7±0.4) μm (5.2—9.0 μm);两极囊呈梨形,大小存在细微差别,极囊顶端存在突起,大极囊长:(4.7±0.5) μm (4.8—6.7 μm),宽:(2.5±0.2) μm (3.2—4.3 μm),小极囊长:(4.4±0.2) μm (4.1—4.8 μm),宽:(2.2±0.1) μm (2.0—2.5 μm);极丝盘绕4—5圈。基于18S rDNA序列(GenBank登录号:KY965936)比对分析,该碘泡虫与放射孢子虫Hexactinomyxon type 2相似率最高,为97%。系统发育分析表明,该碘泡虫与Hexactinomyxon type 2、Hexactinomyxon type 1、Hexactinomyxon type SH-2006、Myxobolus pfeifferi、Myxobolus caudatus和Myxobolus squamae聚为独立分支,和其他已报道的黏孢子虫亲缘关系较远。研究在补充了海城碘泡虫形态学、基因标记序列信息基础上,推断了该虫生活史。     

海城碘泡虫(黏体动物门,黏孢子纲)补充描述及基于18S rDNA系统发育分析（英文）

海城碘泡虫原始描述中形态数据较为简单,且存在多个宿主及寄生部位,其有效性有待确定。利用现行主流的黏孢子虫形态特征和基因标记系统分析相结合的分类学方法,对采自太湖棒花鱼鳃丝的海城碘泡虫进行了补充描述。该碘泡虫孢囊呈白色,圆形,大小为(0.6—1.1)mm。成熟孢子正面观近似椭圆形,上端稍尖,侧面观呈纺锤型,孢子长(10.8±0.7)μm(10.1—11.5μm),孢子宽:(8.1±0.5)μm(7.5—9.0μm),孢子厚:(5.7±0.4)μm(5.2—9.0μm);两极囊呈梨形,大小存在细微差别,极囊顶端存在突起,大极囊长:(4.7±0.5)μm(4.8—6.7μm),宽:(2.5±0.2)μm(3.2—4.3μm),小极囊长:(4.4±0.2)μm(4.1—4.8μm),宽:(2.2±0.1)μm(2.0—2.5μm);极丝盘绕4—5圈。基于18S r DNA序列(Gen Bank登录号:KY965936)比对分析,该碘泡虫与放射孢子虫Hexactinomyxon type 2相似率最高,为97%。系统发育分析表明,该碘泡虫与Hexac-caudatus和Myxobolus squamae聚为独立分支,和其他已报道的黏孢子虫亲缘关系较远。研究在补充了海城碘泡虫形态学、基因标记序列信息基础上,推断了该虫生活史。     

尖形碘泡虫(黏体门: 碘泡虫科)的重描述及其分子系统学研究

研究基于形态和分子信息重描述了寄生于嘉陵江重庆段鲫(Carassius auratus Linnaeus)鳃部和胆囊的尖形碘泡虫(Myxobolus acutus Wu and Chen, 1987), 并获得了该虫体的18S rDNA和ITS1 rDNA序列。尖形碘泡虫成熟孢子壳面观呈梨形, 前端稍尖, 后端钝圆, 缝面观呈宽纺锤形。孢子长(13.6±0.9) μm [(11.4—15.3) μm], 宽(10.2±0.9) μm [(7.5—12.8) μm], 厚(7.6±0.6) μm [(6.9—8.3) μm]。两梨形极囊开口处紧靠并位于孢子前端, 极囊大小不等, 大极囊长(6.2±0.4) μm [(5.1—7.5) μm], 宽(3.8±0.4) μm [(2.8—4.7) μm], 极丝盘绕5—8圈, 小极囊长(2.7±0.4) μm [(1.7—3.7) μm], 宽(1.4±0.2) μm [(0.9—1.9) μm], 极丝盘绕2—3圈。基于18S rDNA为分子标记的系统发育分析显示: 尖形碘泡虫与中华单极虫(Thelohanellus sinensis)有最近的亲缘关系, 两物种形成的进化支与贝壳碘泡虫(M. musseliusae)、苍梧碘泡虫(M. tsangwuensis)和鳃基碘泡虫(M. basilamellaris)形成的进化支呈姐妹群关系。通过系统发育与寄生部位关系的分析结果推测, 尖形碘泡虫的初始寄生部位可能为鳃, 而胆囊则是该物种后来适应的新的寄生部位。     

黄颡单尾虫(粘体门,双壳目)的重描述及基于28S rDNA和ITS-5.8S序列的系统地位分析

采用形态分类学方法与以28S rDNA和ITS-5.8S序列为基础的分子系统学研究方法,对采自嘉陵江重庆市磁器口江段的黄颡单尾虫Unicauda pelteobagrusMa,1998进行了形态学和分子生物学的研究。基于28S rDNA数据探讨了黄颡单尾虫以及单尾虫属与相邻种属粘孢子虫间的系统地位;基于5.8S rDNA数据比较分析了粘孢子虫的系统地位。补充了黄颡单尾虫重庆种群形态学信息和28S rDNA、ITS-5.8S rDNA序列的分子信息。     

几种放射孢子虫的形态特征和分子鉴定

为阐明黏孢子虫病的传播途径, 在2018—2019年期间作者调查了异育银鲫养殖池塘, 从底栖寡毛类苏氏尾鳃蚓中共检测出10种放射孢子虫。基于形态特征鉴定, 10种放射孢子虫分别属于6个集合类群, 其中雷氏放射孢子虫1种、桔瓣放射孢子虫2种、新放射孢子虫2种、三突放射孢子虫2种、棘放射孢子虫2种和匈牙利放射孢子虫1种; 这些物种中有4种与作者实验室前期描述种类一致, 5种为新发现的物种。研究描述了其形态特征并通过SSU rDNA序列比对分析对应的黏孢子虫种类。结果表明新发现的Triactinomyxon HZ和DF与文献中同类群的Triactinomyxon CZ (GenBank登录号 JX477771) 序列相似性最高(93.39%和94.48%), Echinactinomyxon LY1与金鱼肌肉寄生Myxobolus lentisuturalis (GenBank登录号AY119688)相似性最高(96.88%), Echinactinomyxon type LY2 与Hungactinomyxon (GenBank登录号 AY779062)相似性最高(97.86%), Neoactinomyxum type LY与文献报道的Thelohanellus sp. (GenBank登录号 MK412938)相似性最高(92.48%)。文章报道的Hungactinomyxon DF与匈牙利发现的Hungactinomyxon(GenBank登录号 AY779062)序列相似度达99.41%—99.64%, 为同一物种。系统发育分析表明文章所报道的Triactinomyxon HZ和DF与鱼体寄生四极虫亲缘关系较近; Hungactinomyxon DF 和Echinactinomyxon LY1及LY2与碘泡虫属亲缘关系较近; Neoactinomyxum LY与单极虫聚为一支。研究新报道的放射孢子虫进一步丰富了对养殖环境中黏孢子虫多样性的认识, 为开展黏孢子虫病生态防控奠定基础。     

田中碘泡虫的重描述及系统发育分析

基于形态学和分子数据(18S rDNA)重新描述了寄生于重庆江津地区金鱼 (Carassius auratus auratus)鳃丝的田中碘泡虫 (Myxobolus tanakai Kato, et al., 2017), 并结合系统发育分析对其近缘种进行了比较研究。形态学特征: 该虫种孢子为后端钝圆的长梨形, 大小为(14.58±0.54) μm×(6.09±0.37) μm; 两个极囊等大; 极丝与极囊长轴垂直缠绕8—10圈; 囊间突起位于极囊前端呈三角形; 具有嗜碘泡。分子特征: 共获得3个分离样本的18S rDNA序列, 其一级结构序列与日本黑川地区鲤 (Cyprinus carpio) 鳃丝寄生的田中碘泡虫的一致性达99.3%—99.6%, 且在系统发生树中聚为一支。结果表明: 本研究种与日本的田中碘泡虫为同种, 此为中国新记录; 金鱼为田中碘泡虫的宿主新记录。18S rDNA的V2、V4和V7区二级结构的比较结果表明: 田中碘泡虫已发生了明显的种内变异, 推测可能因宿主差异和地理隔离同时所致。此外, GenBank中报道的数个野鲤碘泡虫的序列是否为同种有待进一步厘清。     

楔形两极虫(黏体门,双壳目)的形态学重描述及其近缘种的分子系统学研究

两极虫属Myxidium和楚克拉虫属Zschokklella在形态上非常相似,形态鉴定界限模糊。为进一步厘清两者的分类学关系,本研究对采自涪江重庆市潼南县江段的楔形两极虫M.cuneiforme Fujita,1924进行了形态学重描述,并对其分子系统学进行了研究。楔形两极虫孢子壳面观呈长条形,中部稍凹陷或孢子一边突出,壳瓣上有6~8条与缝嵴平行的条纹;缝嵴直,缝面观呈梭形。孢子长12.5μm±0.3μm,宽5.4μm±0.3μm(n=20)。极囊2个,呈梨形,分布于孢子两极端;极囊长4.3μm±0.2μm,宽3.1μm±0.2μm(n=20),极丝细长且明显,盘曲5~6圈。以18S rDNA为分子标记,对楔形两极虫及其近缘种进行了保守区变异、遗传距离、序列相似度和分子系统发育分析,结果表明:两极虫属和楚克拉虫属均非单系发生,两属间物种相互交叉聚支;两极虫属与楚克拉虫属物种间具有很近的亲缘关系。本文基于形态和分子数据的研究结果支持将两极虫属和楚克拉虫属合并为一个属的观点。     

洪湖碘泡虫的再描述及其近缘种的鉴别性研究

研究基于形态特征和18S rDNA序列相似度、遗传距离、变异位点、GC含量和系统发育比较分析,对采自河南龙湖的寄生于异育银鲫鳃部的一种黏孢子虫以及相似性极高且易混淆的黏孢子虫种类(洪湖碘泡 Myxobolus honghuensis Liu,et al. 2012、瓶囊碘泡虫Myxobolus ampullicapsulatus Zhao,et al. 2008、咽碘泡虫Myxobolus pharynae Lu,et al. 2012和吴李碘泡虫Myxobolus wulii (Wu Li,1986) 进行了系统的鉴别研究。研究结果显示: 河南龙湖异育银鲫鳃部所检获的黏孢子虫为洪湖碘泡虫,该种群对所寄生的异育银鲫未造成疾病症状; 咽碘泡虫与洪湖碘泡虫各种群在形态上极相似,两者间18S rDNA序列相似度为99%-100%,遗传距离为0-0.0013,GC含量均为44.31%,变异位点为2个,表明咽碘泡虫与洪湖碘泡虫应为同一物种。     

东北虎源等孢球虫的发现

对东北虎粪便进行虫卵检查,分离获得了自然感染的球虫卵囊。对球虫卵囊的形态和经培养发育后的各阶段的卵囊形态进行了观察。东北虎源球虫卵囊符合等孢属球虫的形态学特征。根据Genbank 上发表的猫等孢球虫18S rDNA 序列(L74671)设计一对特异性引物,利用PCR 技术对东北虎源球虫的18S rDNA 进行了扩增。扩增得到一段360 bp 的DNA 片段,并对该片段进行了序列测定。测序结果和其它17 种原虫的相应序列进行序列同源性比较分析,分析显示东北虎源球虫和其它等孢属球虫单独聚为一类。结合对东北虎源球虫的卵囊形态、卵囊发育情况及序列分析结果,确定其为等孢属球虫。      

鲫寄生碘泡虫属一新种

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First record of an actinosporean (Myxozoa) in a marine polychaete annelid

The marine polychaete Nereis (Hediste) diversicolor (Annelida) from shallow water in the Oresund, Denmark, was found to be infected with an actinosporean stage of a myxozoan parasite. The body length of the pyriform actinospore is 12-16 microm and its maximum width is 10-12 microm. The spore is triangular in apical view, with the 3 spherical polar capsules distally. The spore is without caudal processes. Eight spores develop in each pansporocyst. Free spores and pansporocysts were found in the musculature and parapodia but not in the intestine. The myxosporean stage in fish is unknown. This is the first record of an actinosporean stage in a marine polychaete, but because marine oligochaetes are rare, compared with polychaetes, the latter are believed to play an important role as invertebrate (alternate) hosts in marine myxozoan life cycles.     

A new myxozoan parasite from the Amazonian fish Metynnis argenteus (Teleostei, Characidae): light and electron microscope observations

Myxobolus metynnis n. sp. (Phylum Myxozoa) is described in the connective subcutaneous tissues of the orbicular region of the fish, Metynnis argenteus (Characidae), collected in the lower Amazon River, near the city of Peixe Boi, Pará State, Brazil. Polysporic, histozoic plasmodia were delimited by a double membrane with numerous microvilli on the peripheral cytoplasm. Several life-cycle stages, including mature spores, were observed. An envelope formed by numerous fine and anastomosed microfibrils was observed at the spore surface. The spore body presented an ellipsoidal shape and was about 13.1 microm long, 7.8 microm wide, and 3.9 microm thick. Elongated-pyriform polar capsules were of equal size, measuring 5.2 microm in length, 3.2 microm in width, and possessing a polar filament with 8-9 turns around the longitudinal axis. The binucleated sporoplasm contained a vacuole and numerous sporoplasmosomes. These were circular in cross-section, showing an adherent eccentric, dense structure, with a half-crescent section. Based on the morphological differences and host specificity, we propose that the parasite is a new species named Myxobolus metynnis n. sp.     

Myxobolus myleus n. sp. infecting the bile of the Amazonian freshwater fish Myleus rubripinnis (Teleostei: Serrasalmidae): morphology and pathology

Myxobolus myleus n. sp. is described from the gall-bladder of the freshwater fish Myleus rubripinnis collected near the city of Oriximiná in the Amazon System, Brazil. The spores obtained from the bile contained two equal symmetrical and smooth valves, each forming the spore wall. The spores were large, with a cone-like form, a semi spherical basal contour and measured (in μm) 19.3 ± 0.5 (n = 25) × 8.3 ± 0.5 (n = 25) × 4.0 ± 0.3 (n = 15). The apical end of the spores contained two elongate, equal and pointed conical polar capsules measuring 13.2 ± 0.4 μm (n = 25) in length and 3.0 ± 0.3 μm (n = 15) in width, each having a slightly tapering polar filament with 19 to 21 turns. The polar capsules were extended below at about 4/5 of the total length of the spores. The sporoplasm was binucleate and contained some sporoplasmosomes. All infected fish presented hypertrophy of the gall-bladder due to presence of the brownish parasite floating in the bile. In this paper we describe this new species of myxosporean based on light and ultrastructural observations, together with its associated pathology.     

Ultrastructural data on the spore of Myxobolus maculatus n. sp. (phylum Myxozoa), parasite from the Amazonian fish Metynnis maculatus (Teleostei)

Light and electron microscopy studies of a myxosporean, parasitic in the intertubular interstitial tissue of the kidney of the freshwater teleost fish Metynnis maculatus Kner, 1860 (Characidae) from the lower Amazon River (Brazil), are described. We observed polysporic histozoic plasmodia delimited by a double membrane and with several pinocytic channels and containing several life cycle stages, including mature spores. The spore body was of pyriform shape and was 21.0 microm long, 8.9 microm wide and 7.5 microm thick. Elongated-pyriform polar capsules were of equal size (12.7 x 3.2 microm) and contained a polar filament with 14 or 15 coils. The spore features fit those of the genus Myxobolus. Densification of the capsular primordium matrix, which increased in density from the inner core outwards, differentiating at the periphery into small microfilaments measuring 45 nm each, and tubuli arranged in aggregates and dispersed within the capsular matrix of the mature spores, are described. Based on the morphological differences and specificity of the host, we propose the creation of a new species named Myxobolus maculatus n. sp.     

Novel Myxobolus and Ellipsomyxa species (Cnidaria: Myxozoa) parasiting Brachyplatystoma rousseauxii (Siluriformes: Pimelodidae) in the Amazon basin,Brazil

We describe two novel myxosporean parasites from Brachyplatystoma rousseauxii, an economically important freshwater catfish from the Amazon basin, Brazil. Myxobolus tapajosi n. sp., was found in the gill filaments of 23.5% of 17 fish, with myxospores round to oval in frontal view and biconvex in lateral view: length 15 (13.5–17) μm and width 10.7 (9.6–11.4) μm; polar capsules equal, length 5.8 (4.6–7.1) μm and width 3 (2.3–3.8) μm containing polar tubules with 6–7 turns. Ellipsomyxa amazonensis n. sp. myxospores were found floating freely or inside plasmodia in the gall bladder of 23.5% of fish. The myxospores were ellipsoidal with rounded extremities: length 12.8 (12.3–13.6) μm and width 7.6 (6.7–8.7) μm; with two equal, slightly pyriform polar capsules, length 3.8 (3.8–4.0) μm and width 3.1 (2.5–3.4) μm, containing polar tubules with 2–3 turns. We combined spore morphometry, small-subunit ribosomal DNA data, specific host, and phylogenetic analyses, to identify both of these parasites as new myxozoan species. Maximum likelihood and Bayesian analyses showed that Myxobolus tapajosi n. sp. clustered in a basal branch in a subclade of parasites from exclusively South American pimelodid fishes. Ellipsomyxa amazonensis n. sp. clustered within the marine Ellipsomyxa lineage, but we suspect that although the parasite was collected in freshwater, its hosts perform a large migration throughout the Amazon basin and may have become infected from a brackish/marine polychaete host during the estuary phase of its life.     

Testicular myxosporidiasis in anurans,with a description of Myxobolus fallax n. sp.

During studies of amphibian sperm cryopreservation, a new species of myxosporidean parasite (Myxozoa, Myxosporae) was observed in the testes of the Australian dwarf green tree frog Litoria fallax (Peters). Myxosporidiasis was found to have no affect on L. fallax body condition or sperm numbers. Myxobolus spores from L. fallax are morphologically distinct from Myxobolus hylae spores (infecting the sympatric Litoria aurea Lesson) and the three previously named (exotic to Australia) Myxobolus species found in anurans. Myxobolus fallax n. sp. is characterised by: pseudocyst white, spherical to ovoid, 141 x 74 to 438 x 337 microm in diameter (mature); plasmodium with spores loosely arranged within interior. Spores ovoid 13.4 +/- 0.5 (12.6-14.6) microm length, 9.5 +/- 0.4 (8.3-10.6) microm width, 6.8 +/- 0.4 (6.5-7.6) microm depth, 1.4 +/- 0.1 (1.3-1.6) length/width; polar capsules broadly pyriform and equal in size 4.2 +/- 0.3 (3.3-4.7) microm length, 2.4 +/- 0.2 (2.1-2.8) microm width; filament coils 7-8, wound tightly and perpendicular to the longitudinal axis of the capsule; polar filament 34 +/- 7.0 (18-50) microm length; intercapsular appendix and sutural ridge folds absent; and iodinophilous vacuole and mucous envelope lacking. In addition to this new species, data from archival samples of M. hylae are provided which show two morphologically distinct spore types. Both appeared rarely in the same pseudocysts and we cautiously retain the single species.     

Morphological,ultrastructural, and molecular analysis of a new species of Myxobolus (Cnidaria,Myxosporea) parasitizing Apareiodon piracicabae (Characiformes,Parodontidae) from Brazil

About forty-two species of Myxobolus have been previously described to parasitize characiform fishes in South America. Here, we described a new myxozoan species, Myxobolus parodontidis n. sp., in the gills of Apareiodon piracicabae (Characiformes, Parodontidae) from the streams of the Middle Paranapanema River basin, Brazil. The proposed new species is supported by a combination of morphological, ultrastructural, and molecular characterization (small subunit ribosomal DNA). Thirteen specimens of A. piracicabae were analyzed and 30.8% was infected by Myxobolus parodontidis n. sp. The myxospores was classified as intralamellar asymmetric type. A few aberrant myxospores with three polar capsules were observed: the spore length and width were the same of normal myxospores, but the polar capsules had smaller sizes. Ultrastructural analysis showed that the plasmodial membrane of Myxobolus parodontidis n. sp. was in direct contact with the host tissue and a connective capsule surrounding the plasmodium was not observed. The phylogenetic analysis showed that the main influence in the clustering of species of myxobolids seems to be related to the phylogenetic relationships established among fish hosts, mainly at the level of family and order. This is the first record of a myxozoan species parasitizing parodontid fish, contributing to the knowledge of the biodiversity of myxozoans from Brazil.     

Two new species of Myxozoa, Myxobolus inaequus sp. n. and Henneguya theca sp. n. from the brain of a South American knife fish, Eigemannia virescens (V.)

Two new species of Myxozoa from the brain of the green knife fish Eigemannia virescens are described: Myxobolus inaequus sp. n. has an unusually large spore body and extremely unequal polar capsules, and Henneguya theca sp. n. has an attenuated spore encased in a sheath not previously described in other Myxozoa . Only spores of the two species were observed, and infections caused no obvious pathological changes in the brain.