一种雷氏放射孢子虫的鉴定及其特征描述

放射孢子虫(Actinosporean)是黏体动物在其中间宿主水生无脊椎动物体内的一个生活阶段。研究鉴定并描述了一种雷氏放射孢子虫的形态和分子特征。该放射孢子虫的主要形态结构是: 由三个极囊、内含孢原质的孢子体和三个尾突组成, 无孢柄。极囊位于孢子体顶端, 呈梨形, 长5.2 μm, 宽2.9 μm; 孢子体侧面观呈长椭圆形, 长16.4 μm, 宽9.5 μm; 三个尾突基本等长, 呈锚状, 平均长度102.6 μm, 宽9.54 μm, 尾突末端轻微的上翘。每个尾突远侧端表面有许多形状不规则的棘状小刺。18S rDNA序列比对表明, 该雷氏放射孢子虫与国外已报道的Myxobolus cultus 18S rDNA序列一致性最高, 达98.41%, 由此推测该雷氏放射孢子虫可能为M. cultus的对应放射孢子虫阶段。研究丰富了国内放射孢子虫的基础研究。     

Hungactinomyxon,a new actinosporean type and collective group(Myxozoa) from <Emphasis Type="Italic">Branchiura sowerbyi</Emphasis> Beddard (Oligochaeta)

Actinosporeans are characterised by great morphological diversity. As it has been proved that the class Actinosporea is a synonym of the Myxosporea, actinosporean genera have only been regarded only as actinosporean collective groups. While most actinosporeans are released individually by their oligochaete hosts, members of the synactinomyxon, siedleckiella and antonactinomyxon collective groups are released as eight connected structural elements. These actinosporean types are differentiated by the type of unit and junction of the caudal processes. On the basis of these characteristics, a new actinosporean type, constructed from eight echinactinomyxon units, is described as hungactinomyxon. Adjacent units are joined by two of their three processes and form two interconnected cubes, each containing four echinactinomyxons. Molecular biological studies also suggest that this new actinosporean type differs from other actinosporean types built up from eight structural elements for which 18S rDNA sequences are available in GenBank.     

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.     

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。     

Sauropod haemal arches: morphotypes,new classification and phylogenetic aspects

Sauropod haemal arches are caudal bony structures that have been traditionally incorporated into two different types observed in different anatomical views: Y-shaped (anterior view) and forked (lateral view). This research proposes a classification combining information observed in anterior and lateral views. Four types of ‘Y-shaped’ and six types of ‘V-shaped’ chevrons were recognised. Complete chevron series in some eusauropods allows the comparison of topological equivalent structures along the tail and also among taxa. A basal titanosaur from Argentina exhibits mid-caudal chevron morphology in which more than one cranial and caudal process is present, arising from the distal blades as well as from the proximal rami, a condition not seen before in a sauropod dinosaur. The morphological variability seen in sauropod chevrons along the tail is in close relationship with the development and distribution of muscle. caudofemoralis longus, as seen in extant crocodiles and as previously proposed for non-avian theropods and for caudal centra and transverse processes of sauropod dinosaurs. Two new characters related to middle chevrons are proposed here, in which the transitional morphology is described.     

Patterns of morphological variation among native and non-native pumpkinseed (<Emphasis Type="Italic">Lepomis gibbosus</Emphasis>) populations: shared and unique aspects of diversification

Contemporary patterns of morphological variation among populations reflects the interplay between historic and contemporary processes that result from selection and constraint. Using the pumpkinseed (Lepomis gibbosus), a species native to North America and introduced to Europe, we assessed the shared and unique aspects of morphological divergence in lentic and lotic environments among native and non-native populations. Ten native and thirteen non-native pumpkinseed populations were collected between 2003 and 2010 from lakes, rivers and reservoirs within the Iberian Peninsula and east-central North America. Fifteen linear external measurements among homologous landmarks that pertain to body size, fin position and fin size were taken from all sampled individuals. Eleven of these measurements were used to test for morphological differences among populations. Pumpkinseed found in lotic water bodies exhibited a more anterior placement of pectoral and pelvic fins and a deeper caudal peduncle and body than those found in lentic water bodies from the same geographic region. However, pumpkinseed also showed morphological differences between geographic origins: pumpkinseed from native populations exhibit a more posterior placement of pectoral and pelvic fins, a narrower anterior caudal peduncle and a more slender body than pumpkinseed from non-native populations. In addition, unique responses of populations to waterbodies within geographic origins revealed a shift between water body types that was opposite in direction for native and non-native populations. Native populations exhibited shorter and deeper caudal peduncles and deeper bodies in lotic habitats, whereas non-native populations showed longer and slender caudal peduncles and more slender bodies in the same type of habitat. Our study demonstrates that contemporary patterns of morphological variation among native and non-native pumpkinseed populations can be explained by contemporary selection and/or a common plastic developmental response among water bodies, historical effects related to geographic origin and unique responses of populations to habitats within geographic origin, and that the effects of history and the interaction between history and contemporary habitat were larger than contemporary processes in explaining morphological variation at this large spatial scale.     

Molecular relationships and phylogeny in a community of myxosporeans and actinosporeans based on their 18S rDNA sequences

The community of myxosporeans and actinosporeans inhabiting a typical Scottish highland stream and the outflow area of an adjacent salmon hatchery was analysed on the basis of their 18S rDNA sequences. Nine myxosporeans belonging to the genera Sphaerospora, Chloromyxum, Zschokkella, Myxidium, Hoferellus and Myxobilatus were identified from mature spores in different organs of the fish species present. Twelve actinosporean types belonging to the collective groups of neoactinomyxum, aurantiactinomyxon, raabeia, echinactinomyxon and synactinomyxon were found to be released from oligochaete worms collected from sediments. Twenty of the 21 sequences obtained from these myxozoans are new entries to the myxozoan database, and the genera Chloromyxum, Hoferellus and Myxobilatus were entered for the first time. Study of the molecular relationships between the different taxa and with other myxozoan sequences available showed that the myxosporeans inhabiting the urinary system clearly cluster together, independently of host species or spore morphology. However, the sequences of the two Sphaerospora species encountered show considerable differences from other members of this group and all other freshwater myxosporeans, and they were found to occupy an ancestral marine position. Three actinosporeans, i.e. Neoactinomyxum eiseniellae, Aurantiactinomyxon pavinsis and Raabeia 'type 3' were found to represent alternate life cycle stages of Chloromyxum sp., Chloromyxum truttae and Myxidium truttae, respectively (approximately 1400 identical base pairs each). Three other actinosporeans encountered (two echinactinomyxon and one raabeia type) showed over 92% sequence identity with myxosporeans from GenBank, whereas all other actinosporeans formed a closely related group devoid of any known myxosporeans.     

Actinosporean stages of Myxozoan parasites of oligochaetes from Nera River basin, Central Italy

The aim of this study was to check the occurrence of actinosporean stages of Myxozoan parasites of oligochaetes in the Nera River basin (Central Italy). The investigation was conducted near twelve trout farms (rainbow and brown trout) along the Nera River and in the littoral of the Piediluco Lake. Four actinosporean types, belonging to the collective groups aurantiactinomyxon, triactinomyxon, raabeia and echinactinomyxon, were detected in some of the biotopes investigated (Piediluco Lake and Sordo River). Differential diagnosis, carried out on a sub-sample of spores, showed a complete fitting with forms previously described in literature, with the exception of the triactinomyxon type.     

Transmission of Thelohanellus hovorkai Achmerov, 1960 (Myxosporea: Myxozoa) to common carp Cyprinus carpio through the alternate oligochaete host

Thelohanellus hovorkai (Myxosporea: Myxozoa) was transmitted to common carp Cyprinus carpio by exposing fish to Aurantiactinomyxon spores collected from the oligochaete Branchiura sowerbyi. The morphological characteristics of the actinosporean stage are described in detail. B. sowerbyi were exposed to T. hovorkai spores isolated from the experimentally infected carp, and after 3 and 4 months the worms exhibited prevalences of the actinosporean stage at 19.47% (7/36) and 14.6% (6/41), respectively. Control, unexposed worms were negative for the actinosporean infection. This is the first report of an Aurantiactinomyxon transforming into a myxosporean belonging to the suborder Platysporina.     

Description of two new actinosporean types from a brook of Fuji Mountain,Honshu, and from Chitose River,Hokkaido, Japan

Actinospore infection of oligochaetes living in the mud of 3 freshwater biotopes in Japan was studied. Using the cell-well plate method, a new aurantiactinomyxon type was found in 0.77% of the examined Tubifex tubifex oligochaete specimens from a brook near Yamanashi Prefectural Fisheries Experimental Station on Fuji Mountain. In 0.14% of Lumbriculus variagetus collected from Chitose River, near Chitose Salmon Hatchery, a new siedleckiella type was found, while at the same time 8.1% of the Lumbriculus spp. oligochaetes released triactinomyxons of Myxobolus arcticus. Of the examined Rhyacodrilus komarovi oligochaetes collected from the Mena River system, Hokkaido, 0.2, 0.6, 0.5 and 0.8% were infected with echinactinomyxon, neoactinomyxum and 2 types of triactinomyxon spores, respectively, and described in our previous paper. The oligochaetes released actinospores for several weeks. Actinospore infection showed high intensity in positive oligochaetes in the case of all the actinosporean types. Two of the actinospore types (aurantiactinomyxon and siedleckiella) presented here have not been previously described.     

Description of a new synactinomyxon type from the River Sousa, Portugal

Actinospore infection of oligochaetes collected from the mud of 2 freshwater biotopes in Portugal was studied. Using the 'cell-well plate method', a new synactinomyxon type was found in 2 specimens (1.3%) of the examined Tubifex tubifex oligochaetes from the River Sousa north of Porto, Portugal. In Criodrilus lacuum and Dero digitata specimens collected from the same river, no actinosporeans were released during the 12 wk observation period. Infected oligochaetes were only found immediately post-collection, and no further actinosporean release was recorded in Tubifex specimens kept alive for several weeks. Actinospore infection showed high intensity in oligochaetes in both positive cases. No actinosporean stages of myxosporeans have as yet been described from Portugal. On the basis of spore morphology and 18S rDNA sequence data, the synactinomyxon type presented in this paper differs from those already known and described in the literature.     

Actinosporean infections in oligochaetes in a river system in southwest Ireland with descriptions of three new forms

Sediment samples were collected in April, June and August 1998 from a river in southwest Ireland. A total of 1,836 oligochaete specimens were collected from these sediments, and examined for actinosporean infections. Actinosporean-infected oligochaetes have been determined, symptoms and course of infection have been considered and the spores released from them have been described. Spore characteristics for each actinosporean were defined and the prevalence of infection in each oligochaete species was also determined. The overall prevalence of infection with actinosporeans within the oligochaete sample was approximately 2%. Seven types were distinguished, belonging to echinactinomyxon, aurantiactinomyxon and neoactinomyxum forms, from Tubifex ignotus, Lumbriculus variegatus and Limnodrilus hoffmeisteri, and compared with actinosporean types previously reported in the literature. Three of these forms have not been previously described, while the other 4 are morphologically and morphometrically similar to known forms. These actinosporeans may be stages in myxozoan life cycles.     

Taxonomic Reference Libraries for Environmental Barcoding: A Best Practice Example from Diatom Research

DNA barcoding uses a short fragment of a DNA sequence to identify a taxon. After obtaining the target sequence it is compared to reference sequences stored in a database to assign an organism name to it. The quality of data in the reference database is the key to the success of the analysis. In the here presented study, multiple types of data have been combined and critically examined in order to create best practice guidelines for taxonomic reference libraries for environmental barcoding. 70 unialgal diatom strains from Berlin waters have been established and cultured to obtain morphological and molecular data. The strains were sequenced for 18S V4 rDNA (the pre-Barcode for protists) as well as rbcL data, and identified by microscopy. LM and for some strains also SEM pictures were taken and physical vouchers deposited at the BGBM. 37 freshwater taxa from 15 naviculoid diatom genera were identified. Four taxa from the genera Amphora, Mayamaea, Planothidium and Stauroneis are described here as new. Names, molecular, morphological and habitat data as well as additional images of living cells are also available electronically in the AlgaTerra Information System. All reference sequences (or reference barcodes) presented here are linked to voucher specimens in order to provide a complete chain of evidence back to the formal taxonomic literature.     

Detection of myxozoan parasites in oligochaetes imported as food for ornamental fish

To determine the potential for dissemination of myxozoan parasites by transfer of their alternate oligochaete hosts, shipments of tubificid worms obtained from an overseas commercial aquarium supplier were screened for actinospore stages of myxozoan parasites. At least 7 different triactinomyxon types were identified. The morphological characteristics of the actinospores recovered from these tubificids shared characteristics with triactinomyxons characterized in other surveys, particularly from eastern Europe. Analysis of the screened samples by polymerase chain reaction and comparison of morphological data indicated that these actinospores did not correspond to the triactinospore of Myxobolus cerebralis. Although identification of these triactinomyxon types was beyond the scope of this study, these data suggest that the unregulated import-export and exchange of live organisms for ornamental fish food may result in accidental introduction or dissemination of myxozoan parasites.     

Henneguya polarislonga n. sp. (Cnidaria: Myxosporea) parasitizing Astyanax lacustris (Lütken, 1875) with an insight on its life cycle

Henneguya polarislonga n. sp. is described from the gills of Astyanax lacustris (Lütken, 1875) (Characiformes, Characidae) from streams of the Middle Paranapanema River, Upper Paraná River basin, in the São Paulo State, Brazil. The proposed new species is supported by a combination of morphological and molecular characterization (partial fragment of the SSU rDNA). Thirty specimens of A. lacustris were analyzed and myxospores were found in the gill lamellae of one specimen (Prevalence = 3.3%). Henneguya polarislonga n. sp. was morphometrically and genetically distinct from other Henneguya spp. previously described in Astyanax spp., mainly differing in the total length and caudal appendages length of the mature myxospores. Comparative analysis of the SSU rDNA sequences revealed that Seisactinomyxon-type actinospores previously reported parasitizing oligochaetes are developmental stages of the life cycle of Henneguya polarislonga n. sp. (similarity of 99.9%). This is the first time that an actinospore and a myxospore are correlated through molecular analysis in Brazil, contributing to the knowledge of the myxozoan ecology and biodiversity.     

Description of raabeia,synactinomyxon and neoactinomyxum developing stages of myxosporeans (Myxozoa) infecting Isochaetides michaelseni Lastočkin (Tubificidae) in Lake Balaton and Kis-Balaton Water Reservoir,Hungary

Molecular and morphometric investigations were conducted on the actinosporean morphotypes of myxosporeans surveyed in oligochaetes of Lake Balaton and Kis-Balaton Water reservoir. Oligochaetes belonging to the species Isochaetides michaelseni Lasto?kin and Branchiura sowerbyi Beddard as well as to the genera Nais Dujardin, Dero Müller and Aeolosoma Ehrenberg were studied during an 18-month period. Actinosporeans were obtained exclusively from I. michaelseni (7,818 specimens) with very low prevalence (0.01–0.06%). Four new actinosporean morphotypes of the collective groups raabeia (2 types), synactinomyxon (1 type) and neoactinomyxum (1 type) were found and described, including the first synactinomyxon collective group from Hungarian biotopes and a new raabeia morphotype. Except for Synactinomyxon type 1, the 18S rDNA analysis revealed that the spores did not match any myxospore entity found in the GenBank.