Oligochaeta from profundal zones of Spanish reservoirs

The profundal benthic fauna of 63 Spanish reservoirs was studied during 1972–75. Samples were taken in the deepest part of each reservoir with a modified Van Veen grab. The fauna was dominated by tubificid worms and chironomids. Sixteen species of Oligochaeta were found, two of them new for the Spanish fauna (Potamothrix heuscheri and Haber pyrenaicus). This was the first time H. pyrenaicus was found since the species was described in 1974 from the Pyrenees. Four species were frequent in the reservoirs (Limnodrilus hoffmeisteri, Tubifex tubifex, L. claparedeianus and Dero digitata) but only the first two were abundant as mature individuals. Another interesting fact is the high abundance of immature animals in all samples, accounting for more than 80% of the total individuals examined. The geographical distribution of all species in Spain and their relationship with the typology of Spanish reservoirs are discussed. There seems to be a correlation between the throphic status of the reservoirs and the relative proportion of L. hoffmeisteri as compared to T. tubifex, the number of individuals of the first species increasing with water eutrophication.     

Experimental detection of the actinospores of Myxobolus pseudodispar (Myxosporea: Myxobolidae) in oligochaete alternate hosts

The development of Myxobolus pseudodispar Gorbunova, 1936, an intracellular myxosporean muscle parasite of the roach Rutilus rutilus L., was studied in experimentally infected oligochaetes. In one experiment, uninfected Tubifex tubifex Müller and Limnodrilus hoffmeisteri (Claparéde) were exposed to mature spores of M. pseudodispar. Triactinomyxon spores developed both in T. tubifex and L. hoffmeisteri specimens. Triactinospores were first released from the oligochaetes 76 d after initial exposure. At that time, pansporocysts containing 8 triactinospores were located in the gut epithelium of experimentally infected oligochaetes, but free actinosporean stages were also found in their gut lumen. Each triactinospore had 3 pyriform polar capsules and an elongated cylindrical sporoplasm with 8 secondary cells. The spore body joined the 3 caudal projections with a relatively long style. One of the 3 caudal projections was shorter than the other two. The total length of the triactinospore was on average 206.5 microns.     

Distribution of aquatic Oligochaeta in the Finnish Lake District

SUMMARY. The distribution of oligochaetes was examined at sampling stations grouped into three types: (1), in eutrophic and dystrophic areas or in areas polluted by pulp-mill wastewaters; (2), slightly eutrophic stations; (3), 'clean' stations unaffected by sewage or other inputs. Limnodrilus hoffmeisteri and Potamothrix hammoniensis were practically the only species in group 1, and the same species accounted for two thirds of the total numbers in group 2, although Peloscolex ferox and some other species also occurred. At the cleanest stations the dominating species were P. ferox, Psammoryctides barbatus, Stylodrilus heringianus and Tubifex tubifex . A factor analysis showed that L. hoffmeisteri and P. hammoniensis were associated with increased nutrients and water colour in the lower part of the epilimnion. In the metalimnion the relationship of S. heringianus and P. ferox to water colour and total nitrogen differed from that of L. hoffmeisteri and P. hammoniensis . Winter oxygen content was important for S. heringianus .     

The development of Eustrongylides tubifex (Nematoda: Dioctophymatoidea) in oligochaetes

Egg development of Eustrongylides tubifex (Nitzsch in Rudolphi, 1819) J?gerski?ld, 1909, was studied at 5, 10, 15, 20, 25, and 30 C. Eggs developed at 20, 25, and 30 C. Development ceased at 0, 5, 10, and 15 C but resumed when temperatures were raised. Eggs contained first-stage larvae in 23-26 days at 25 C. Seven species of aquatic oligochaetes were exposed experimentally to eggs of E. tubifex containing first-stage larvae. Third-stage larvae of E. tubifex developed in the aquatic oligochaetes, Limnodrilus hoffmeisteri Claparède, 1862, and Tubifex tubifex (Müller, 1774). Larvae developed in the ventral blood vessel of oligochaetes. Second-stage larvae were seen first in oligochaetes 30 days postinfection and third-stage larvae were seen 70-109 days postinfection at 25 C. Third-stage larvae in oligochaetes retained the cuticle of the first and second molt.     

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.     

The role of environmental factors in the ecology of tubificid oligochaetes - an experimental study

The effects of temperature, oxygen and substrate on growth rates of three tubificid oligochaetes were examined in the laboratory. Two species Tubifex tubifex and Limnodrilus hoffmeisteri (Tubificidae, Oligochaeta) had similar narrow temperature ranges over which growth occurred, from 10–13°C and both showed a considerable tolerance to extended periods of anoxia, of at least 16 and 10 weeks respectively. However no growth was observed under anoxic conditions. A third common species Ilyodrilus templetoni was sensitive to anoxia and could not survive more than four weeks. There was no evidence of differences in substrate quality affecting growth rates of either T. tubifex or L. hoffmeisteri . The temperature and oxygen responses of these three species may explain their distribution in some lakes of the English Lake District.     

What is Tubifex tubifex (O. F. Müller) (Oligochaeta,Tubificidae)?

A review of the fairly muddled conditions in the early history of Tubifex tubifex (O. F. Müller, 1774) is given. The identity of Müller's (1774) Lumbricus tubifex is discussed, analytical examinations of samples from the most likely type-locality of the species are accounted for, and a neo type has been selected. For comparison, other "Tubifex" specimens, both European and American, are likewise analysed and a scrutiny of the literature concerning the species and its synonyms is undertaken. The survey results in a clearer picture of T. tubifex and a revised view of the qualifying characters on the specific level. Diagnoses of the species T. tubifex (O. F. Müller) and T. fissidens sp.n., Kernall, MS, 1914, are given.     

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     

Oligochaeta of the middle Po River (Italy): principal component analysis of the benthic data

The application of principal component analysis to two types of habitat (the benthos of macrophytes and of central river bed) enabled us to single out some of the factors that affect the dynamics and the structure of the oligochaete population and its various reactions to environmental conditions. As regards macrophytes, the distribution of the variables on the basis of the first component is correlated, to a certain extent, with a seasonal factor without any significant differences among sites. The largest population is most closely correlated with the summer months. In fact, we found that the Naididae and Tubificidae species generally develop in larger numbers at higher temperatures. For the Tubificidae, we could detect a precise seasonal cycle. In the central river bed habitat, the first component was correlated with the river discharge, which determines the granulometric characteristics of the sediment; we noticed a correlation among the sites that have the same characteristics, regardless of sampling site or date. The species which correlate most closely among themselves are the Tubificidae Limnodrilus hoffmeisteri, Tubifex tubifex, L. udekemianus and L. profundicola, which are very characteristic of environments that contain abundant organic matter. The second component is correlated with temperature, and hence with the availability of oxygen, which determines the presence and the abundance of more sensitive species.     

A field course survey of three English river systems

A hydrobiological field course for undergraduates in the Department of Biology, University of Salford has proved useful in investigating river pollution, and parts of the course may be suitable for upper school studies. The course compares the Lancashire rivers Lune, Ribble and Irwell, but could be adapted for still waters.

The water quality was assessed by simple chemical methods and the bacteriological quality by multiple tube and membrane filtration techniques. These assessments were then related to the benthic inverte-brates in the rivers—dipteran larvae, oligochaete worms, leeches, molluscs, stoneflies and mayflies. The Irwell was found to be grossly polluted, the Ribble mildly polluted and the Lune relatively unpolluted.     

The chemical environment of tubificid and lumbriculid worms according to the pollution level of the sediment

In Lake Geneva (Switzerland), 14 tubificid and 2 lumbriculid worm species were collected in a total of 170 samples of sediment. The sediment was analysed through ten chemical variables: organic carbon, total phosphorus, Cd, Zn, Sn, Pb, Hg, Cu, Cr, Mn. The chemical environment characterizing the presence of every worm species was defined by the mean value of each of these ten variables in all samples where the species was found. The multivariate comparison of the chemical environment typical of every species enabled six groups of species to be distinguished, each characterized by the high value of one chemical variable: (1) Peloscolex ferox, Potamothrix hammoniensis, Limnodrilus claparedeanus, and Cd. (2) Psammoryctides barbatus, and Zn. (3) Limnodrilus hofmeisteri, L. udekemianus, L. profundicola, and total P. (4) Potamothrix heuscheri, Aulodriluspluriseta, A. limnobius, Tubifex tubifex, Ilyodrilus templetoni, Stylodrilus heringianus, and organic C. (5) Potamothrixvejdovskyi, and, Hg. (6) Peloscolex velutinus, Stylodrilus lemani, and Mn. Pollution level of the sediment decreased from group 1 to 6, so each of these groups may be used to define a different level of pollution. The pooled coefficient of variation of the ten chemical variables used to define the chemical environment of each species diminished from group 1 to 6: the most opportunistic species colonized the most polluted areas.     

中国长足摇蚊幼虫和霍普水丝蚓扰动下沉积物氧气特征分析

为研究中国长足摇蚊幼虫(Tanypus chinensis)和霍普水丝蚓(Limnodrilus hoffmeisteri)扰动对表层沉积物氧气渗透及空间分布的影响,采集梅梁湾表层沉积物,借助高精度溶氧微电极,研究两种生物扰动作用下,太湖梅梁湾表层沉积物氧气渗透深度和空间分布的变化,并根据氧气在流动培养体系中浓度的变化和在扩散边界层中的扩散过程这两种方法计算界面氧气交换速率。结果表明,中国长足摇蚊幼虫和霍普水丝蚓两种底栖生物扰动均能提高沉积物界面氧气交换速率,且微电极法的计算值要低于流动培养法。通过溶氧微电极剖面能够准确的获得氧气渗透深度的信息。结果发现:长足摇蚊幼虫的扰动能提高沉积物氧气渗透深度并造成氧气在沉积物内空间分布的差异,长足摇蚊幼虫扰动后沉积物氧气渗透深度由无扰动的6 mm增至10 mm。与长足摇蚊幼虫相比,霍普水丝蚓扰动没有增加沉积物氧气渗透深度及造成空间分布差异。对比两种计算方法发现,在生物扰动作用下,由于生物作用的影响,根据氧气在扩散边界层的扩散得到的值可能会低估氧气的界面交换速率。       

Seasonal changes in vertical distribution, biomass and faecal production of tubificids in the profundal region of a shallow Japanese lake

Two tubificid species Limnodrilus hoffmeisteri and L. claparedeianus formed more than 93% of the total number of oligochaetes in the profundal. Limnodrilus spp. worms were found down to 33 cm in the sediment but in great numbers in the upper zone in June and October. Worms confined to the top 15 cm of sediment accounted for 53-92% of the total number. There were two annual maxima in population density and biomass, one in late spring (66000 inds m⁻², 17 g wet wt m⁻²) and the other in mid autumn (97000 inds m⁻², 176 g wet wt m⁻²). Two regression lines describing the effect of temperature on faecal production rate were obtained; Log F = 0.0604 T (°C) −0.7660 (below 15°C), Log F = 0.0266 T – 0.2170 (above 15°C). In total 26.8 kg dry wt m⁻² of sediment was defecated annually by Limnodrilus spp. The sediment in the 0–10 cm stratum may pass through the guts of the worms 2.3 times a year. Sedimentation rates in profundal region were very low with respect to the faecal production rates of the tubificids.     

Host-parasite relationships of caryophyllaeid cestodes and aquatic oligochaetes: II. Effects of host age and mixed infections

Experiments were conducted to assess the relationship between annelid age and susceptibility of the annelid as an intermediate host for a caryophyllaeid, as well as the effect a mixed-species infection has on rate of metacestode development and parasite mortality. Four host-parasite systems were studied: Biacetabulum biloculoides and Hunterella nodulosa in Limnodrilus hoffmeisteri and Glaridacris catostomi in Ilyodrilus templetoni and Tubifex tubifex. Annelids were divided into 3 age classes: immature, approximately 7 days old; intermediate, approximately 14 days old; and mature, approximately 30 days old. Immature oligochaetes in all groups were more susceptible to infection, their parasites exhibited a lower mortality rate than 30-day-olds, and the total number of parasites in this group was higher than for the other age classes. Metacestodes reached the infective stage earlier in immature as compared to older oligochaetes. Interspecific competition between B. biloculoides and H. nodulosa resulted in increased parasite mortality and a slower rate of parasite development for the species that became established second. A prior infection with one species of cestode also affected the susceptibility of L. hoffmeisteri to infection with another species.     

The severity of whirling disease among wild trout corresponds to the differences in genetic composition of Tubifex tubifex populations in central Colorado

We analyzed the geographic distribution of Tubifex tubifex from various river drainages in central Colorado by genetic screening with specific mitochondrial 16S ribosomal DNA (mt 16S rDNA) markers. Four distinct mt 16S rDNA lineages are evident. The sites varied with respect to land- and water-use practices. All sites represented habitats presumed capable of supporting oligochaetes. At the locations where whirling disease has had the greatest impact on resident rainbow trout, T. tubifex, representing lineages I and III (genotypes known to be susceptible to Mxyobolus cerebralis), were most commonly found. In contrast, at sites less affected by whirling disease, T. tubifex of lineages V and VI that are more resistant to M. cerebralis infections were more abundant. The predominance of resistant T. tubifex worms (lineages V and VI) at low-impact sites supports the conclusion that when these genotypes are in greater abundance, the potential for more severe effects of whirling disease on wild rainbow trout populations may be diminished.     

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。     

The fauna of the muddy sediments of Lough Neagh, with particular reference to eutrophication

SUMMARY. The main groups of animals found in the muddy sediments of Lough Neagh were Chironomidae (Diptera) and Oligochaeta (mainly Tubificidae). At 8 m depth, the average biomass of the main species in these groups was: Chironomus anthracinus , 2.64gm⁻²; Procladius , 342.8 mgm⁻²; tubificids ( Tubifex, Potamothrix, Aulodrilus, Limnodrilus ), 418.7mgm⁻². At 25m depth C. anthracinus and Procladius were less abundant, C. plumosus was present and among the tubificids Limnodrilus had a higher density (up to 50000m⁻²) often an order of magnitude greater than at 8m. Kinnego Bay, a semi-enclosed, polluted area of the lough, had fewer chironomids than the open lough, with chiefly C. plumosus and Procladius. Limnodrilus was more abundant than at 8m. Dero obtusa (Naididae) was also present, sometimes in large numbers (31000m⁻²).
The response of this fauna to eutrophication in L. Neagh appears to be a diminution in the number of species present, with C. plumosus gradually replacing C. anthracinus as the dominant Chironomus , and tubificids, particularly Limnodrilus , becoming more abundant, A further stage, shown in Kinnego Bay, has Procladius as the most numerous' chironomid. Average total biomass at the three sites was 3.9gm⁻² at 8m, 13.2gm⁻² at 25 m in the main lake, 2.8gm⁻² in Kinnego Bay. At 8m depth, C. anthracinus contributed 76% of the total biomass, at 25m Limnodrilus contributed 74% and C. anthracinus 15%, and in Kinnego Bay, Limnodrilus contributed 40%, C. plumosus 28% and Procladius 20%.     

On the ecology of littoral Oligochaeta of an oligotrophic Finnish lake

In material sampled from 0.5–6 m on two sampling dates and three subareas the dominant Oligochaeta were Limnodrilus hoffmeisteri Claparède and Peloscolex ferox (Eisen), both composing more than 30% of the abundances of oligochaetes present. The numbers of Oligochaeta were mostly higher in August than in May. Regional differences could be found although the lake seems to be very homogenous. Temporal and vertical variations were detectable in separate subareas. The oligochaete biomass was maximal at 2 m depth. In soft bottom sediments the oligochaetes composed 15.9% of macrobenthos biomass and 12.2% of numbers, but on the stony bottom only 1.9% of numbers. The ratio of Oligochaeta/Chironomidae was similar to those in profundals of oligotrophic lakes. Correlation coefficients between species and two measures of niche overlap were in partial agreement. A temporal niche seems to occur: when the chironomid larvae decrease during the summer, the oligochaetes increase.     

Characterisation of two novel types of hexactinomyxon spores (Myxozoa) with subsidiary protrusions on their caudal processes

Two types of hexactinomyxon spores, Hexactinomyxon type 1 nov. and Hexactinomyxon type 2 nov., are reported from freshwater tubificid oligochaetes, Limnodrilus hoffmeisteri and L. udekemianus. Spores are triradially symmetrical and comprise a spore body, style and 6 caudal processes. The caudal processes arise from the division of each of the 3 valve cells into an equal pair of projections at the base of the style. One of each pair is fused conspicuously to its nearest neighbour for the initial 1/5 to 1/4 of their total length. Distally, each process possesses subsidiary protrusions which are irregularly distributed and irregularly shaped extensions of the valve cell. Scanning electron microscopy of Hexactinomyxon type 2 nov. revealed that these protrusions are a seamless extension of the valve cell wall which branch distally, occasionally laterally, and terminate in a distinct bulbous structure; they also form the terminus of each process. The small subunit ribosomal DNA gene (18S) of both hexactinomyxon types was amplified through a nested PCR, then digested with the restriction enzymes Dde I and Hha I. The resultant cleavage patterns suggested the presence of 2 forms. Subsequent partial sequencing of 18S rDNA confirmed the identification of 2 novel types.