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.     

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.     

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.     

Occurrence of actinosporean stages of myxosporeans in an inflow brook of a salmon hatchery in the Mena River System,Hokkaido, Japan

Actinospore infection of oligochaetes living in the mud and on the roots of vegetation in an inflow brook of a Hokkaido salmon hatchery was studied within the framework of a Japanese-Hungarian research program. Two triactinomyxon types, 1 echinactinomyxon, and 1 neoactinomyxum type were isolated from the oligochaete Rhyacodrilus komarovi Timm, 1990 collected during the survey. The aurantiactinomyxons were recorded over a period of 3 mo starting from the day after oligochaete collection. The oligochaetes released actinospores for several weeks from the first day of the study. Spore excretion of individual oligochaetes was not synchronous. Of the oligochaetes examined, 0.7, 7, 3 and 3%, were infected with the echinactinomyxon, neoactinomyxum and the 2 types of triactinomyxon spores, respectively. Actinospore infection was intense in the positive oligochaetes in all 4 types. Of the 4 actinospore types presented here, 3 are described for the first time.     

Description of a new Neoactinomyxum type actinosporean from the oligochaete <Emphasis Type="Italic">Branchiura sowerbyi</Emphasis> Beddard

Actinosporean infection of oligochaetes living in the mud of a commercial gibel carp pond with myxosporean disease was studied. Six actinospore types were detected exclusively from the oligochaete Branchiura sowerbyi Beddard with very high prevalence (18%). Five out of the six types were identified as the same actinosporeans described in previous reports, the sixth actinosporean was identified as a new Neoactinomyxum type and described here based on morphological and molecular characterisation. Spore body of the actinospore was globular, much smaller than caudal processes. Three caudal processes were disc-like in apical view, hemispherical in side view, closer together and encircling the spore body. The number of sporoplasm cells was detected as eight in one specimen. The new actinosporean markedly differed from other Neoactinomyxum types in literature having much bigger caudal processes. DNA sequence analyses further confirmed the morphological identification, and revealed the actinosporean described here (KU641392) possessed less than 94% sequence similarity with myxozoans available in the GenBank database.     

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.     

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.     

Species composition,distribution, and abundance of oligochaetes in the Kanawha River,West Virginia

Species composition, distribution, and abundance of oligochaetes in the Kanawha River, West Virginia, were investigated. Eighteen taxa of oligochaetes including 7 tubificids, 8 naidids, and representatives of the families Enchytraeidae, Lumbriculidae, and Aelosomatidae were collected. While most of the species collected are cosmopolitan, Pristina synclites and Stephensoniana sp. previously reported only from Asia and Africa were collected in the Kanawha. Other peculiarities of the Kanawha oligochaete fauna included the common occurrence of specimens of Limnodrilus cervix and Limnodrilus hoffmeisteri with atypical penis sheaths. The dominant and most widely distributed of the Kanawha River oligochaetes were immature tubificids lacking capilliform chaetae, Branchiura sowerbyi, Dero cf. obtusa, Limnodrilus hoffmeisteri, and Aulodrilus pigueti.Oligochaete densities ranged from 401–2403 individuals/m² in areas presumed to be nonpolluted, to 1–671 individual/m² at sites with suspected toxicity. The highest density of oligochaetes (2835 individuals/m²) occurred at a site of organic enrichment.     

Evaluation of a vector-control strategy of haemorrhagic thelohanellosis in carp,caused by Thelohanellus hovorkai (Myxozoa)

The life cycle of Thelohanellus hovorkai (Myxozoa), the causative agent of haemorrhagic thelohanellosis of carp Cyprinus carpio, involves the alternate oligochaete host Branchiura sowerbyi, which plays the role of vector in the parasite's transmission. Field investigations in carp farms suggested that oligochaete fauna were closely associated with the substrate type of the pond. The pond bottom in the enzootic farm consisted of clay soil and soft sediments comprised of organic mud, in which B. sowerbyi dominated in high densities, with a maximum of 5.6 ind. kg(-1) soil. In another case, in a carp farm with no previous history of the disease, the pond bottom was sandy soil, in which small-sized oligochaetes, composed mainly of Limnodrilus socialis, dominated. Laboratory studies on the substrate preference of oligochaetes proved that B. sowerbyi prefers mud to sand, whereas L. socialis has no tendency to substrate tropism. The delicate body surface of B. sowerbyi was subject to damage by rugged-edged sand particles, which inflicted severe injuries to the worms. Transmission experiments showed that L. socialis, which are non-susceptible to T. hovorkai, suppressed the production of T. hovorkai actinospores in B. sowerbyi in a mixed assemblage of oligochaetes. Field and experimental evidence in this study imply that substrate replacement in culture ponds might regulate the benthic oligochaete communities, resulting in minimization of the impact of haemorrhagic thelohanellosis. We propose that ecological control of oligochaete fauna by environmental management is a promising strategy against myxozoan diseases.     

放射孢子虫在中国的首次发现

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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。     

Development of Myxobolus macrocapsularis (Myxosporea: Myxobolidae) in an oligochaete alternate host,Tubifex tubifex

The development of Myxobolus macrocapsularis Reuss, 1906, a myxosporean parasite of the gills of common bream Abramis brama L., was studied in experimentally infected oligochaetes. In 3 experiments uninfected Tubifex tubifex Muller and Limnodrilus hoffmeisteri (Claparéde) were exposed to mature myxospores of M. macrocapsularis. In all experiments, typical triactinospores developed in T. tubifex specimens but no infection was found in L. hoffmeisteri. Triactinospores were released from oligochaetes 66 to 99 d after initial exposure. At that time pansporocysts containing 8 triactinospores were located in the gut epithelium of experimental oligochaetes, but free actinosporean stages were also found in the gut lumen of the oligochaetes. Each triactinospore had 3 pyriform polar capsules and a barrel-shaped sporoplasm with 32 secondary cells. The spore body joined the 3 caudal projections with a stout style.     

广东省6座水库及其入库河流底栖动物调查与综合评价

2010年8月对广东省6座水库及其入库河流的大型底栖无脊椎动物群落进行采样调查,并分别利用Goodnight-Whitley指数和BPI指数对水库及入库河流的水质进行评估。结果表明,水库共检出底栖动物13种,优势种为霍甫水丝蚓(Limnodrilus hoffmeisteri)、苏氏尾鳃蚓(Branchiura sowerbyi)和八斑多足摇蚊(Polypedilum masudai),种类丰富度变动范围为2～5种,平均密度为277ind/m²,变动范围160～480ind/m²。入库河流的种类丰富度和密度均高于水库,共检出底栖动物28种,优势种为苏氏尾鳃蚓、霍甫水丝蚓、花翅前突摇蚊(Procladius choreus)和河蚬(Corbicula fluminea),种类丰富度变动范围为2～7种,底栖动物平均密度为382ind/m²,变动范围192～816ind/m²。水质评价结果表明,6座水库的水质状况总体良好,但入库河流均受到不同程度的污染,污染较为严重的黄岗河和黄羌河,其水库汤溪水库和公平水库也产生了污染。     

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...     

Development of Myxobolus portucalensis Saraiva & Molnár, 1990 (Myxosporea: Myxobolidae) in the oligochaete Tubifex tubifex (Müller)

The extrapiscine development of Myxobolus portucalensis, a myxosporean parasite of the subcutaneous connective tissue of eel Anguilla anguilla L. was studied in the experimentally infected oligochaete Tubifex tubifex. After infecting parasite-free tubificids with mature spores of M. portucalensis, development of actinosporean stages was first observed with a light microscope 26 days after infection. Triactinospores of M. portucalensis emerged from the worms after 160 days of intra-oligochaete development. It was observed in histological sections that early pansporocysts were located in the gut epithelium of the experimental oligochaetes. Mature pansporocysts, each containing eight triactinospores, appeared 149 days after infection. After the rupture of pansporocysts, free actinospores were found in the lumen of the oligochaete gut. Released actinospores were floating in the water and showed a typical triactinomyxon form. Each triactinospore had three pyriform polar capsules, a sporoplasm with 32 secondary cells, a moderately long style and three slightly curved, sharply pointed caudal processes. The prevalence of infection in T. tubifex proved to be 52.5% (n = 40). No infection was found in Limnodrilus hoffmeisteri or in control Tubifex specimens     

The food of a community of East African freshwater fishes

Quantitative data on the food of the fishes inhabiting Lake Mcllwaine, Rhodesia, show that the feeding of the dominant species in this community ( Clarias gariepinus (Burchell), Hydrocynus vittatus (Castelnau), Tilapia melanopleura Dumeril, Tilapia mossamhica Peters, Tilapia macrochir Boulenger, Labeo altivelis Peters, and Gnathonemus macrolepidotus (Peters)) covers a wide spectrum, and almost all elements of the potential food supply are utilized. Exceptions are noted, however, and the introduction of the Indian carp, Catla catla (Cuv. & Val.), is advocated in order to utilize the large blooms of phyto- and zooplankton. The oligochaete, Branchiura cf. sowerbyi , which forms over 50% of the benthic biomass is also not utilized as a source of fish food. However, no fish species is known to feed on oligochaetes to any large extent. Predation by the Tigerfish, Hydrocynus vittatus , is shown to have severe effects upon recruitment to the valuable Tilapia fishery, and the reduction of the abundance of H. vittatus by means of selective fishing techniques is advocated.