Description of a new actinosporean type from South African freshwaters

Actinospore infection of oligochaetes collected from the mud of 2 freshwater biotopes in South Africa was studied. Using the 'cell-well plate method', a new aurantiactinomyxon type was found in 1.1% of the examined Branchiura sowerbyi oligochaete specimens from the Rietvlei River, north of Johannesburg, Gauteng, South Africa. In 1.5% of B. sowerbyi collected in a pond (Padda Dam), near the Rand Afrikaans University, Johannesburg, the same aurantiactinomyxon type was found. Infected oligochaetes were found only after collection and no actinosporean release was recorded in Branchiura specimens kept alive for several weeks. Actinospore infection showed a high intensity in oligochaetes in both positive cases. Until now, no actinosporean stages of myxosporeans have been described from South Africa. The aurantiactinospore type presented in this communication differs from the known types already described in the literature.     

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.     

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.     

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.     

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.     

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.     

Prevalence and susceptibility of infection to Myxobolus cerebralis,and genetic differences among populations of Tubifex tubifex

The prevalence of infection and susceptibility of the aquatic oligochaete Tubifex tubifex to Myxobolus cerebralis, was examined in 2 studies on the upper Colorado River, Colorado, USA, where whirling disease occurs in wild trout populations. In the first study, the prevalence of infection ranged from 0.4 to 1.5%, as determined by counting the number of T. tubifex releasing triactinomyxons of M. cerebralis directly following their collection from the field. The susceptibility of those T. tubifex not releasing triactinomyxons was assessed by the number of these oligochaetes releasing triactinomyxons 3 mo following experimental exposures to spores of M. cerebralis. The prevalence of infection following experimental exposures of these T. tubifex ranged from 4.2 to 14.1%. In a second study, all T. tubifex collected at 2 different times directly from the 2 field sites in Colorado were exposed to spores of M. cerebralis. Individual oligochaetes representing those groups of T. tubifex releasing and those groups not releasing triactinomyxons at 3 mo were screened with molecular genetic markers. T. tubifex populations found at the 2 study sites consisted of 4 genetically distinct lineages that varied with respect to their susceptibility to experimental exposure to M. cerebralis. Lineages I and III contained the most oligochaetes susceptible to M. cerebralis and were the most prominent lineages at Windy Gap Reservoir, a site of high infectivity for wild rainbow trout on the upper Colorado River. In contrast, at the Breeze Bridge site which is below Windy Gap Reservoir and where M. cerebralis infections are less severe in wild trout, oligochaetes in lineages V and VI that are resistant to M. cerebralis were more prominent. These results suggest that certain habitats, such as Windy Gap Reservoir, are conducive to large and more homogenous populations of susceptible T. tubifex lineages that may serve as point sources of infection for M. cerebralis. Although not a direct objective of this study, there was no evidence of M. cerebralis infections among any oligochaetes other than those that would be classified as T. tubifex by standard morphological characteristics.     

Survival of glochidial larvae of the freshwater pearl mussel, Margaritifera laevis (Bivalvia: Unionoida), at different temperatures: a comparison between two populations with and without recruitment

The viability of free-living glochidia of the freshwater pearl mussel (Margaritifera laevis) was studied in the laboratory at water temperatures of 10 degrees C, 15 degrees C and 20 degrees C. To obtain glochidia, gravid female mussels were collected from the Chitose River, inhabited by adult and juvenile mussels, and from the Abira River, where only adult mussels were found. Daily survival rates of glochidia from each population at various water temperatures were significantly different, and survival time was longest at the lowest temperature in each population. Maintenance of some field mussel populations might become difficult at higher water temperatures due to the short survival time of glochidia and expected low density of host fish. Daily survival rates of glochidia were compared between the Abira population at 15 degrees C and the Chitose population at 20 degrees C, since these temperatures were close to the mean water temperature during the period of glochidial release in the respective rivers. Daily mean survival rates were significantly different between the Abira population at 15 degrees C and the Chitose population at 20 degrees C. Mean glochidial survival rate for the Chitose population changed from 85.3% to 66.2% from 9 to 13 h, whereas that for the Abira population dropped suddenly from 80.4% to 34.2% from 10 to 14 h after the initiation of experiment. Absence of juveniles in the Abira River might have been caused by the low glochidial viability. Survival times of free-living glochidia in Margaritiferidae tend to be shorter than in other families in Unionoida. A trade-off is suggested between high fertility and low glochidial survival rate in Margaritiferidae.     

A new species of shrike (Laniidae: Laniarius) from Somalia, verified by DNA sequence data from the only known individual

A new species of bush-shrike is described on the basis of the only known individual. The bird was captured in a disturbed Acacia thicket near the town of Bulo Burti by the Shabeelle River in central Somalia. Believed to represent a species near extinction, the bird was kept alive, studied in captivity and then released. The type material comprises moulted feathers, blood samples and DNA extracted from feather quills. For comparison, DNA from other bush-shrikes was obtained from old museum skins and three live birds. Comparisons of base sequences from the cyt-b gene of mitochondrial DNA support the judgement that the bird represents a full species and is not a colour morph or hybrid of examined taxa. This procedure confirms that, in situations where collecting is not desirable, tissue from live individuals can be used to define taxa, and for comparisons with DNA from museum specimens of other taxa.     

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.     

The life cycle of Sphaerospora truttae (Myxozoa: Myxosporea) and some features of the biology of both the actinosporean and myxosporean stages

A previously undescribed echinactinomyxon type actinosporean was shown experimentally to be the alternate stage of Sphaerospora truttae. The echinactinomyxon type spores were found to be released from Lumbriculus variegatus and occasionally Tubifex tubifex. Overall infection prevalence of the echinactinomyxon was 0.14%. Peak release was in March-May each year. S. truttae spores developed in experimentally infected salmon 4.5 mo post-exposure to echinactinomyxon spores. Extrasporogonic stages of S. truttae first appeared in naturally infected salmon in early July and persisted for 8 to 10 wk. Correlation between peak release of echinactinomyxon spores and appearance of extrasporogonic stages of S. truttae is discussed.     

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.     

Maesaipsyche mekongensis sp. n. – the Third Species of the Genus from South-East Asia (Trichoptera,Arctopsychidae)

Maesaipsyche mekongensis sp. n. is described from Laos. The type series was collected near the Mekong River, which is suggestive of a potamobiontic habitat of the larvae. The male genitalic apparatus is illustrated.     

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.     

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.     

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.     

Description of a new Echinorhynchid species (Acanthocephala) from the European eel, Anguilla anguilla, in Germany, with a key species of Acanthocephalus in Europe

Acanthocephalus rhinensis n. sp. is described from the European eel. Anguilla anguilla (Linnaeus, 1758), collected in the Rhine River near the city of Karlsruhe, Germany. It is the sixth species of Acanthocephalus Koelreuther, 1771 described from European fish. Four other species are known from amphibians. The new species is distinguished from the other 5 species infecting fish by having a 1.2-mm-long proboscis armed with 15-21 rows of 13-16 hooks each, lemnisci about as long as receptacle, oblong and slightly pre-equatorial testes, and thin fusiform eggs, measuring 85-95 X 15-18 micro. Testes in the other European species are usually round to ovate, except in Ac. anguillae (Müller, 1780) Lühe, 1911 where they are also elongated but postequatorial. It aslo has an orange-brown belt encircling the anterior end of the trunk. The comparative distribution of Acanthocephalus in Europe and North America, and the validity of 2 presumably questionable species are discussed, Acanthocephalus falcatus (Froelich, 1789) Lühe, 1911 and Ac. Paronai (Cendorelli, 1897) Meyer, 1932. A dichotomus key distinguishing Ac. rhinensis from the other 9 European species is also included. The new species was only found in 3 of 390 eels examined during 11 yr; this may be related to the changing benthos community in the Rhine River.