Light and ultrastructural description of Meglitschia mylei n. sp. (myxozoa) from Myleus rubripinnis (Teleostei: Serrasalmidae) in the Amazon River system

Meglitschia mylei n. sp. found in the gall bladder of the teleostean fish Myleus rubripinnis (Serrasalmidae) from the middle Amazonian region of Brazil is described using light and transmission electron microscopy. The spores observed in the bile averaged 24.6±0.8 μm long, 8.7±0.4 μm wide and 5.1±0.3 μm thick and were strongly furcate and arcuate ∩-shaped composed of two symmetric equal-sized valves, up to ～70 nm thick. Each valve possessed one opposed tapering appendage, 20.1±0.7 μm long, oriented parallel towards the basal tip of the appendages and joined along a right suture line forming a thick strand. The strand goes around the central part of the spore, which in turn surrounds two equal and symmetric spherical polar capsules (PC), 2.1±0.3 μm in diameter, located at the same level. Each capsule contains a polar filament with five (rarely six) coils. The binucleate sporoplasm was irregular in shape, contained several sporoplasmosomes, ～175 nm in diameter and filled all the space of the two caudal appendages. Based on the arc shape of the spore with two tapering caudal appendages oriented to the basis of spores, on the number and position of the PC and of the polar filament coils and arrangements, and on the host specificity, we propose the name M. mylei n. sp. for this new myxozoan. Accordingly, this is the second described species of this genus.     

Ultrastructure of Myxobolus brycon n. sp. (Phylum Myxozoa), parasite of the piraputanga fish Brycon hilarii (Teleostei) from Pantanal (Brazil)

Light and electron microscopy studies of a myxosporean, parasitizing the gill filaments of the freshwater fish Brycon hilarii (Valenciennes, 1850) (Characidae) collected in the Paraguay River (18°49'S, 57°39'W) (Pantanal), Brazil, is described. This parasite produces spherical to ellipsoidal polysporic histozoic plasmodia (Pmd) (up to ～180 μm in diameter) delimited by a double membrane and with several pinocytic channels. The plasmodial cyst contained the youngest developmental stages at the cortical periphery and immature and mature spores more internally. The Pmd developed near the cartilaginous structure of the gill filament, forming a prominent deformation where the gill lamellae disappear. Pyriform spores measured 6.9±0.6 (range 6.5-7.2) μm long, 4.2±0.5 (range 3.9-4.8) μm wide, and 2.5±0.7 (range 1.9-2.8) μm thick. The spores composed of two equal shell valves (～70 nm thick), adhering together along the straight suture line, surrounded two equal symmetric and elongated to pyriform polar capsules (PC) 4.2±0.6 (range 3.8-4.7) × 1.9±0.6 (1.7-2.5) μm; each PC contained a coiled polar filament with eight or nine (rarely 10) turns and a binucleated sporoplasm cell. Dense irregular masses were observed among the polar filaments coils. An intercapsular appendix was not observed. The sporoplasm contained several globular sporoplasmosomes randomly distributed among an extensive rough endoplasmic reticulum system with numerous vesicles and cisternae. Based on the morphological and ultrastructural differences and specificity of the host, we establish the new species, Myxobolus brycon n. sp.     

Myxidium volitans sp. nov., a parasite of the gallbladder of the fish, Dactylopterus volitans (Teleostei: Triglidae) from the Brazilian Atlantic coast--morphology and pathology

Myxidium volitans sp. nov. (Myxozoa: Myxidiidae) parasitizing the hypertrophied green-brownish gallbladder of the teleost Dactylopterus volitans, collected in the Atlantic coast near Niterói, Brazil was described based on ultrastructural studies. The spores were fusiform, sometimes slightly crescent-shaped on average 21.7 ± 0.3 μm (mean ± standard deviation) (n = 50) long and 5.6 ± 0.4 μm (n = 30) wide. The spore wall was thin and smooth, comprising two equally-sized valves joined by a hardly visible sutural ridge. Spores containing two pyriform polar capsules (PC) (5.0 ± 0.4 × 2.3 ± 0.3 μm) (n = 30) are situated in each extremity of the spore. The PC wall was composed of hyaline layer (0.20-0.29 μm thick) and by a thin external granular layer. Each PC contains a polar filament (PF) with irregular arrangements that was projected from its apical region to the bases of PC and coiled laterally from bases to the tip of PC. Some regular striations and S-like structures in the periphery of the PFs with four-five irregular sections were observed. Based on the spore morphology, ultrastructural differences and the specificity of the host we describe this parasite as a new myxosporidian, named M. volitans sp. nov.     

Ceratomyxa aegyptiaca n. sp. (Myxozoa: Myxosporea) from the gall-bladder of Solea aegyptiaca Chabanaud (Pleuronectiformes: Soleidae) in a Tunisian coastal lagoon

A new marine myxosporean species, Ceratomyxa aegyptiaca n. sp. is described from the gall-bladder of Solea aegyptiaca Chabanaud collected from the Ghar El Melh Lagoon in northeastern Tunisia. Mature spores are elongate and crescent-shaped, measuring 8-11?μm in length and 48-58?μm in width. The polar capsules are spherical, 3.2-4?μm in diameter and equal in size. Trophozoites are polysporous and float free in the bile or are attached on the epithelium of the gall-bladder. Morphological data and molecular analysis based on 18S rDNA sequences are provided. The 18S rDNA of C. aegyptiaca is readily distinguishable from that of other myxozoan species, as the genetically most similar myxozoan parasite, C. seriolae Yokoyama & Fukuda, 2001 (AB530265) collected from Seriola quinqueradiata Temminck & Schlegel in Japanese waters, shares with it only 67.5% identical nucleotides over a 1,680-bp long fragment of 18S rDNA.     

A new species of Myxozoa, Henneguya rondoni n. sp. (Myxozoa), from the peripheral nervous system of the Amazonian fish, Gymnorhamphichthys rondoni (Teleostei)

Henneguya rondoni n. sp. found in the peripheral lateral nerves located below the two lateral lines of the fish Gymnorhamphichthys rondoni (Teleostei, Rhamphichthyidae) from the Amazon river is described using light and electron microscopy. Spherical to ellipsoid cysts measuring up to 110 microm in length contained only immature and mature spores located in close contact with the myelin sheaths of the nervous fibres. Ellipsoidal spores measured 17.7 (16.9-18.1)-microm long, 3.6 (3.0-3.9)-microm wide, and 2.5 (2.2-2.8)-microm (n=25) thick. The spore body measuring 7.0 (6.8-7.3)-microm long was formed by two equal symmetric valves, each with an equal tapering tail 10.7 (10.3-11.0) microm in length. The tails were composed of an internal dense material surrounded by an external homogeneous sheath of hyaline substance. The valves surrounded two equal pyriform polar capsules measuring 2.5 (2.2-2.8)-microm long and 0.85 (0.79-0.88)-microm (n=25) wide and a binucleated sporoplasm cell containing globular sporoplasmosomes 0.38 (0.33-0.42) microm (n=25) in diam. with an internal eccentric dense structure with half-crescent section. Each polar capsule contains an anisofilar polar filament with 6-7 turns obliquely to the long axis. The matrix of the polar capsule was dense and the wall filled with a hyaline substance. The spores differed from those of previously described species. Based on the ultrastructural morphology of the spore and specificity to the host species, we propose a new species name H. rondoni n. sp.     

葡萄碘泡虫、似葡萄碘泡虫和茄形碘泡虫的鉴别及系统发育

葡萄碘泡虫Myxobolus acinosus Nie & Li, 1973、似葡萄碘泡虫Myxobolus pseudoacinosus Guo, et al., 2018和茄形碘泡虫Myxobolus toyamai Kudo, 1917形态非常相似, 有着共同的宿主和相同的寄生部位, 是病原鉴定中容易混淆的种。文章基于形态学和18S rRNA基因信息对三者进行了鉴别和分子系统学研究。成熟孢子形态特征的比较分析显示, 三者形态存在显著差异。葡萄碘泡虫与似葡萄碘泡虫18S rDNA序列相似度为98.4—98.8%, 遗传距离为0.013—0.020; 葡萄碘泡虫与茄形碘泡虫18S rDNA序列相似度为96.1—97.2%, 遗传距离为0.038—0.042; 似葡萄碘泡虫和茄形碘泡虫18S rDNA序列相似度为96.4—97.6%, 遗传距离为0.033—0.040。18S rDNA序列比对显示, 葡萄碘泡虫含有15个关键变异位点, 可将该虫与似葡萄碘泡虫和茄形碘泡虫区分; 似葡萄碘泡虫含有5个关键变异位点, 可将该虫与葡萄碘泡虫和茄形碘泡虫区分; 茄形碘泡虫含有33个关键变异位点可将该虫与葡萄碘泡虫和似葡萄碘泡虫区分。18S rRNA二级结构V4区的E23-2构型可将葡萄碘泡虫与似葡萄碘泡虫和茄形碘泡虫区分, 而V7区的H43构型可将茄形碘泡虫与葡萄碘泡虫和似葡萄碘泡虫区分。以上表明, 三者无论在形态上还是在遗传上均具有独立物种的特征。系统发育分析显示, 葡萄碘泡虫、似葡萄碘泡虫和茄形碘泡虫为系统树中分化较晚的一支。     

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。     

Fine structure of Chloromyxum menticirrhi n. sp. (Myxozoa) infecting the urinary bladder of the marine teleost Menticirrhus americanus (Sciaenidae) in Southern Brazil

A myxosporidian was found in the urinary bladder of the teleost Menticirrhus americanus Linnaeus, 1758 (Sciaenidae) collected from the South Atlantic coast of Brazil. Polysporic amoeboid plasmodia containing sporoblasts, developing pansporoblasts and spores were free in the bladder lumen. The prevalence of infection was 17.64% (15/85). Unfixed spores were spherical to subspherical, on average 10.5 μm long, 9.8 μm wide and 10.1 μm thick (n=25), and fixed spores measured 10.1×9.5×9.7 μm. The two spore valves were of equal size and each possessed prominent sutural lines and about 41 (37–45) surface ridges aligned parallel with the suture line. These ridges gave transverse sections a cog-wheel-like outline. The spores contained four pyriform polar capsules of equal size (3.20×2.0 μm) (n=25) (fixed), each with a polar filament having 3–4 (rarely 5) coils. The binucleate sporoplasm was irregular in shape, with granular matrix and randomly distributed dense bodies. The shape and dimensions of the spore, as well as the number, position and arrangement of the surface ridges, polar capsules and polar filament indicate that this is a new species, herein designated Chloromyxum menticirrhi. The gill, liver, gall bladder and intestine of the host showed no abnormalities.     

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.     

A new species of myxosporean (Sphaeromyxidae), a parasite of lined seahorses, Hippocampus erectus, from the Gulf of Mexico

Sphaeromyxa cannolii sp. n. is described from the bile ducts of aquaria-maintained lined seahorses (Hippocampus erectus) from the Gulf of Mexico. Spores of the new species are linear, 17-18 μm long and 5-6 μm wide, with flattened tips; polar capsules measure 4 × 3 μm. Routine necropsies of H. erectus following planned death revealed liver inflammation, bile duct obstruction, bile accumulation, and myxozoan parasites in the bile ducts of 11 of 40 animals sampled (27.5%). The presence of S. cannolii in an aquaculture setting should prompt keepers to carefully quarantine new animals and exclude annelid fauna, a potential intermediate host of myxozoans.     

<Emphasis Type="Italic">Myxobolus imparfinis</Emphasis> n. sp. (Myxozoa: Myxosporea), a new gill parasite of <Emphasis Type="Italic">Imparfinis mirini</Emphasis> Haseman (Siluriformes: Heptapteridae) in Brazil

A new species of myxozoan, Myxobolus imparfinis n. sp. is described based on material from the gills of Imparfinis mirini (Haseman) (Heptapteridae). Mature myxospores are round, measuring 7.1–8.4 (7.9 ± 0.3) μm in length, 4.5–6.2 (5.5 ± 0.5) μm in width and 3.1–4.2 (3.7 ± 0.3) μm in thickness. The polar capsules are of unequal size, the larger polar capsule measuring 3.4–4.5 (3.9 ± 0.3) μm in length and 1.4–2.0 (1.7 ± 0.1) μm in width and the smaller capsule measuring 3.1–3.8 (3.4 ± 0.2) μm in length and 1.2–1.8 (1.5 ± 0.2) μm in width. The polar filament presents 6–7 coils. Spores had a prevalence of infection of 75% (6/8). In histological analyses we detected the development site of spores in primary filaments, in afferent branchial artery, thus classifying the type of infection to the filamental type and vascular subtype. The phylogenetic analyses of a dataset including species Myxobolus Bütschli, 1882 and Henneguya Thélohan, 1892 from South America recovered M. imparfinis n. sp. as a sister species of Myxobolus flavus Carriero, Adriano, Silva, Ceccarelli & Maia, 2013. To our knowledge, this is the first record of a myxozoan species parasitising I. mirini.     

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.     

Ellipsomyxa tucujuensis n. sp. (Myxozoa: Ceratomyxidae), a parasite of Satanoperca jurupari (Osteichthyes: Cichlidae) from the Brazilian Amazon

The present study describes a new coelozoic, eukaryotic microparasite of the genus Ellipsomyxa Køie, 2003 (Ceratomyxidae: Myxozoa) found parasitizing the gallbladder of Satanoperca jurupari Heckel, 1840 collected in the Curiaú River Environmental Protection Area in Macapá, Amapá state, Brazil. The fish were collected using mesh cast net. The gallbladders were examined, preserved in 80% alcohol for molecular analysis (SSU rDNA gene), and fixed in Davidson for histological slide preparation. The new parasite had a prevalence of 81% in the gallbladder, asymmetric plasmodia, irregular free spores in the bladder fluid, with no cyst formation. The spores are elliptical, with characteristics of the genus Ellipsomyxa, and they had a mean length of 10.11 (8.56–10.5) μm, mean width of 7.81 (5.96–9.56) μm, and thick walls. The polar capsules are sub-spherical in shape, slightly asymmetrical, with a mean length of 3.12 (2.31–3.99) μm and mean width of 2.5 (2.22–2.95) μm, containing polar filament with five or six coils perpendicular to the longitudinal axis of the capsule. The Bayesian Inference assigned the new species to a subclade formed by a lineage of Ellipsomyxa species from the Amazon region. Ellipsomyxa tucujuensis n. sp. is the sixth species of this genus described in fish from the Amazon region, and the first for the state of Amapá.     

Light and Electron Microscopy of the Spore of Myxobolus heckelii n. sp. (Myxozoa), Parasite from the Brazilian Fish Centromochlus heckelii (Teleostei, Auchenipteridae)

ABSTRACT. A myxosporean parasitizing the gill filaments of the freshwater teleost fish Centromochlus heckelii collected in the Tocantins River (Lower Amazonian Region, Brazil) is described using light and electron microscopy. This parasite produces spherical to ellipsoidal cyst-like plasmodia up to 250 μm in diameter, with a thick wall strengthened by several stratified juxtaposed crossed collagen layers, whose thickness varies according to the number of the layers. Several compressed fibroblasts are observed among the collagen fibrils. Deposits of spherical dense material are scattered at the internal periphery of the cysts. Plasmodia and different developmental stages, including immature and mature spores, filled the central region of the cysts. The spore body is ellipsoidal in valvar view and biconvex in sutural view. It is formed by two equal-sized and symmetric valves measuring 12.7 μm long (12.2–13.1) ( n =50), 6.6 μm wide (6.3–6.9) ( n =25), and 4.0 μm (3.7–4.4) ( n =20) thick. A thin layer formed by fine and anastomosed microfibrils is observed at the spore surface. Two equal, elongated pyriform polar capsules measure 2.9 μm (2.7–3.3) × 1.7 μm (1.4–2.0) ( n =25), each containing four or five oblique polar filament coils. The binucleated sporoplasm contains numerous spherical sporoplasmosomes, glycogen particles, and a large vacuole with fine granular matrix. Based on the morphological and ultrastructural differences and specificity of the host, we describe this isolate as a new myxosporidian, Myxobolus heckelii n. sp. (Myxozoa, Myxosporea).     

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。     

Developmental stages of Hepatozoon hemprichii sp. nov. infecting the skink Scincus hemprichii and the tick Hyalomma impeltatum from Saudi Arabia

The life cycle of Hepatozoon hemprichi n. sp. is described; the vertebrate host is Scincus hemprichii and it is vectored by Hyalomma impeltatum. Erythrocytic stages of 18 ± 1.8 × 4 ± 0.8 μm developed in the hemocoel of ticks to sporozoites within 16-18 days. Schizogony occurred in the liver parenchyma and the endothelial cells of blood capillaries in lung and spleen. Mature schizonts measuring 27 ± 3.11 × 20.13 ± 3.0 μm produced 28 merozoites (on average). The merozoites were 13 ± 1.21 × 1.21 ± 0.72 μm with nuclei 5 ± 0.65 × 2.1 ± 0.51 μm. Syzygy and differentiation of gamonts took place in tick's hemocoel up to the third day post-infection (PI). The microgamont (16 ± 0.31 × 18 ± 0.42 μm) produced 4, uniflagellated microgametes at 4-5 days PI. The microgamete measured 15.2 ± 0.31 μm while the flagellum was always at least 26 μm. The macrogamete was very large in size (31 ± 3.11 μm) with a central nucleus. After fertilization, (5-6 days PI) zygotes developed into oocysts (55 ± 3.41 × 52 ± 4.11 μm) in which repeated mitotic divisions with centripetal invaginations occurred; each contained 18 banana-shaped sporozoites, 13.61 ± 0.8 × 1.2 ± 0.31 μm in size. Experimental transmission was successfully carried out by oral administration or by intra-peritoneal inoculation of the infective stages (sporozoites) to uninfected skinks and led to the appearance of blood stages after 5 wk and 4 wk, respectively.     

Ultrastructural and molecular characterization of a new microsporidium parasite from the Amazonian fish, Gymnorhamphichthys rondoni (Rhamphichthyidae)

A new species of a microsporidium found in the freshwater teleost Gymnorhamphichthys rondoni, collected on the lower Amazon River, is described based on light, ultrastructural, and phylogenetic studies. This parasite develops in the skeletal muscle of the abdominal cavity, forming whitish cyst-like structures containing numerous spores. Mature spores, lightly pyriform to ellipsoidal with rounded ends and measuring 4.25 ± 0.38 × 2.37 ± 0.42 μm (n = 30), were observed. The spore wall, which measured about 102 nm, was composed of 2 layers with approximately the same thickness. The isofilar polar filament was coiled, with 9-10 (rarely 8) turns. The posterior vacuole appeared as a pale area, occupying about 1/3 of the spore length, and contained a spherical posterosome composed of granular material that was denser at the periphery. The myofibrils located near the spores appeared to be in advanced degradation. Molecular analysis of the rRNA genes, including the ITS region, and phylogenetic analyses using maximum parsimony, maximum likelihood, and Baysesian inference were performed. The ultrastructural characteristics of the spores and the phylogenetic data strongly suggested that it is a new species related to Kabatana, Microgemma, Potaspora, Spraguea, and Tetramicra. We named this new microsporidian from Amazonian fauna as Kabatana rondoni n. sp.     

Scanning electron microscopy and molecular characterization of a new Haplosporidium species (Haplosporidia), a parasite of the marine gastropod Siphonaria pectinata (Mollusca: Gastropoda: Siphonariidae) in the Gulf of Mexico

Based on scanning electron microscopy and the small subunit ribosomal RNA (SSU rRNA), Haplosporidium tuxtlensis n. sp. (Haplosporidia), a parasite found in the visceral tissues of the false limpet Siphonaria pectinata (Linnaeus, 1758), is described. The spores are ellipsoidal (3.61 ± 0.15 μm × 2.69 ± 0.19 μm), with a circular lid (2.94 ± 0.5 μm) representing the operculum. The spore wall bears filaments occurring singly, or in clusters, of 2 to 8, fusing distally. Phylogenetic relationships of H. tuxtlensis n. sp. were assessed with other described species using the SSU rRNA sequence. Haplosporidium tuxtlensis n. sp. is sister taxon to Haplosporidium pickfordi Barrow, 1961. The morphological characteristics (spore wall structure, shape, size, and filament structure) and the unique host identity corroborate it as a new species. Additionally, this is the first record of Haplosporidia infecting striped false limpets in the Gulf of Mexico.