Some rotifers from coastal lakes of Brazil,with description of a new rotifer,Lepadella (Xenolepadella) curvicaudata n. sp.

Four relatively rare, two common rotifers and one rotifer new to science are described from some coastal lakes near Rio de Janeiro, Brazil. Each rotifer is described in detail, and several are accompanied by illustrations and mensuration data. Geographic distribution and individual habitats of the rotifers are also discussed. Several species show a larger geographic distribution than previously known.     

A new marine rotifer of the genus Encentrum Its morphology and cultivation

Encentrum linnhei , a new marine rotifer from the west coast of Scotland is described. The structure of the trophi together with other characters clearly distinguish it from other species of the genus Encentrum . The work of Harring & Myers (1928) in clarifying the systematics of the Dicranophorinae greatly facilitated the "running down" of characters. A method of germ-free monoxenic culture of the rotifer is also described.     

Systematics,reproductive isolation and species boundaries in monogonont rotifers

The typological concept of rotifer species and the morphological basis of rotifer systematics is reviewed and alternatives proposed. Occasional sexuality in the cyclical parthenogenetic life cycle of monogononts permits application of the biological species concept to this group. Data from cross-mating experiments with Asplanchna, Brachionus and Epiphanes illustrate the usefulness of reproductive isolation as a criterion for species boundaries. Populations from different geographic regions are often interfertile indicating that rotifer species are genetically integrated over wide areas. The main types of isolating mechanisms operating in monogononts are reviewed. The role of behavioral reproductive isolation in maintaining species boundaries is examined. The use of a mate recognition bioassay which estimates the probability of copulation and quantifies the degree of isolation is described. Recent work of the mechanism of mate recognition is reviewed. It is concluded that the biological species concept is applicable to rotifers and that a more experimental approach to determining species boundaries is both feasible and desirable.     

Variability and instability of planktonic rotifer associations in Lesotho,southern Africa

Seventeen localities over a 1500 m altitudinal range were sampled in January 1991 and October 1992 in the subtropical highlands of Lesotho, southern Africa. Spatial and temporal variability in rotifer assemblages are described briefly, and factors driving community heterogeneity are considered. Predation was identified as one significant factor; some sites with low rotifer diversity had dense populations of large calanoid copepods (Lovenula falcifera, Paradiaptomus warreni), and in other localities, tadpoles of the clawed toad, Xenopus laevis.Gut content analysis demonstrated that both calanoids and tadpoles were consuming rotifers.     

On a new species of Keratella (Rotifera: Monogononta: Brachionidae)

A new species of planktonic rotifer, Keratella sinensis n.sp.is described from Lake Yaoquan, Heilongjiang, P.R. China. Itprobably also occurs in the Republic of Korea and Japan. The newmorphospecies is characterised by an unusually smooth lorica, andstrongly reduced lateral anterior spines. It is the first exampleof a planktonic freshwater rotifer, endemic to North EastAsia.     

New Rotifera from Kenya, with a revision of the Ituridae

Brachionus africanus sp. nov . and Itura symmetrica sp. nov. are described from Kenya. The Ituridae are revised, a key to the species is provided and a cladistic analysis performed. Some remarks on rotifer endemism in Africa are given.     

Some new and rare warmwater rotifers

Two new rotifer species, Lecane (Monostyla) aliger n.sp. and Proales pugio n.sp. are described from the Bahama Islands, Florida and California, and their autecology outlined. Some other rare rotifers are discussed which also prefer subtropical conditions. They are: Epiphanes clavulata, Epiphanes brachionus spinosus, Lecane crepida and Proalides tentaculatus tentaculatus. The existence of subtropical rotifer associations is discussed and supported by ecological data.     

Distribution of rotifers in North Island,New Zealand,and their potential use as bioindicators of lake trophic state

The distribution and ecology of planktonic rotifers was investigated in 33 lakes in the North Island, New Zealand, between 1997 and 1999. A total of 79 species of monogonont rotifer were identified, with an average of 21 species per lake, a diversity which is high in comparison with many previous New Zealand studies. Most species recorded were cosmopolitan taxa, and were widespread in their distribution over the North Island. Multivariate analyses (Multi-Dimensional Scaling and Canonical Correspondence Analysis) did not distinguish distinct lake groupings based on rotifer communities, but rather gradients in assemblages, which were most highly associated with lake trophic state. Based on these responses, the development of potential rotifer bioindicator schemes for lake trophic state is described and discussed.     

Canadian rotifers II. Parc Mont Tremblant,Quebec

Nine lakes in Mont Tremblant Provincial Park were investigated during summer and fall. Data on lake morphometry and water chemistry are tabulated. Most lakes were oligotrophic, some were dystrophic bog lakes. They contain a rich rotifer fauna and some very rare species, which are described in detail.     

On Paradicranophorus aculeatus ((NEISTWESTNOVA-SHADINA, 1935) with Remarks on All Other Species of the Genus (Rotifera: Dicranophoridae)

In 1934, the rotifer Paradicranophorus aculeatus was discovered by Neistwestnova-Shadina in the River Oka near Murom (Russia). She described it as a Dicranophorus species. In 1958, the rheophilic rotifer was rediscovered in the Polish River Grabia by Pawlowski. This paper reports a third occurence in three samples from the Yun Nan Luoxiao River in China, allowing additional studies of this rare species.     

Two new species of the family Dicranophoridae (Rotifera, Ploima) from the littoral psammon, with notes on other brackish water rotifers in Denmark

The rotifer fauna has been investigated at three littoral brackish water localities in the Öresund, Denmark. Samples taken from plankton, periphyton and psammon yielded 14 rotifer species. Two of these are new to science and are described herein. Both species were found in psammon at the same locality. Erignatha longidentata n. sp. is characterised by having toes with swollen bases, convex outer margins and concave inner margins. The trophi have a pair of large subunci and relatively large unci. The other new species, Paradicranophorus wesenberglundi n. sp., is characterised by having two large red pigmented eyespots and large conical toes. The rami are lyrate, and intramallei and supramanubria are present in the mallei.     

几种培养方法对萼花臂尾轮虫(Brachionus calyciflorus)种群密度及其环境因子影响的比较研究

分别利用泥鳅 -藻 -轮虫和罗非鱼 -藻 -轮虫共生隔离培养的方法 ,研究萼花臂尾轮虫 ( Brachionuscalyciflorus)的种群密度和主要环境因子的变化。研究结果表明 :加入泥鳅的培养缸中 ,有 1 1 d轮虫数量超过 1 0 0 ind/ml,其中有 5d超过 2 0 0ind/ml,最高密度达 2 50 ind/ml;在罗非鱼的培养缸中 ,在整个实验过程中 ,种群密度超过 1 0 0 ind/ml以上的时间有 6d(第5～ 1 0天 ) ;单纯利用藻类培养轮虫时 ,种群密度较低 ,且维持时间较短 ,最高种群密度不足 1 0 0 ind/ml,利用藻类 -轮虫 -鱼类共存同一生态系统中 ,并使鱼类和轮虫隔离进行生态培养时 ,能提高轮虫种群密度 ,延长种群高峰期     

Cephalodella edax. sp. nov. A rotifer parasitic in the motile colonial alga Uroglena volvox Ehrenberg

A monogonont rotifer found parasitizing colonies of the motile alga Uroglena volvox Ehrenberg in two north English lakes is described as a new species. Diagnostic taxonomic details are given together with remarks on other rotifers known to occur in motile colonies of algae.     

Rotifers from five high arctic ponds (Cape Herschel,Ellesmere Island,N.W.T.)

Five small ponds on Cape Herschel, Ellesmere Island, N.W.T. (latitude 78° 37 N; 74° 42 W) were investigated, and their rotifer fauna discussed. Although the number of individuals is very low, the rotifer assemblage is remarkably rich (33 species), especially considering the harsh environmental conditions, and the short ice-free period of only six weeks. The shallow ponds are all alkaline, and the rotifer species are either cosmopolitan, or very rare. Proales kostei n. sp. is described.on leave from Concordia University, Montreal, Quebecon leave from Concordia University, Montreal, Quebec     

Species composition,distribution and seasonal dynamics of Rotifera in a Rift Valley lake in Ethiopia (Lake Awasa)

The species composition of rotifers in Lake Awasa was studied and 40 species recorded. Seven species appeared in large numbers in the plankton seasonally. Brachionus and Keratella species made up more than 50% of the rotifer community by numbers during the observation period (1983–1987). The standing stock numbers of rotifer species are low with a maximum of 50 individuals L^–1, and some possible reasons for this observation are discussed. Most rotifer species are distributed randomly in the lake and show 3-fold fluctuations between consecutive days.The seasonal dynamics of most rotifer species are correlated with mixing periods in the lake, and the amplitude of seasonal fluctuation may be as high as 50-fold. Clear-cut seasonal succession of rotifer species was observed during the study period, but no consistent seasonal pattern for individual species was obvious. Also, observations indicate that rotifer biomass is partly sustained by availability of carbon through the bacterial pathway and that competitive exclusion for food by nauplii and ciliates probably keeps rotifer abundance low.     

Rotifera from Peat-Swamps in Phuket Province,Thailand, with the Description of a New Colurella Bory de St. Vincent

The rotifer fauna of three peat-swamps in Phuket province, southern Thailand was investigated. A total of 77 species is identified, 12 of which are new to Thailand. A new species, Colurella sanoamuangae n. sp., is described. The zoogeography of the registered species is discussed.     

FINE STRUCTURE OF THE CILIA OF ROTIFERS

The fine structure of the coronal cilia of the rotifer Philodina citrina has been studied in detail. Specimens were fixed with OsO₄ and embedded in butyl—methyl methacrylate, Epon 812, or Vestopal and sectioned with a Porter-Blum microtome. The details of structure of the rootlets, basal bodies, basal plates, and free cilia are described. The general structure of the rotifer ciliary apparatus conforms well to that established for other species. One of the main observations is the difference in structure of the peripheral filaments in the opposing halves of a cross-section of the free cilium. Also, in longitudinal sections evidence is offered for the existence of a helical structure in the peripheral filaments.     

Application of unicellular algae Chlorella vulgaris for the mass-culture of marine rotifer Brachionus

Condensed suspension of Chlorellavulgaris was used for the food of the rotifer Brachionus plicatilis and B. rotundiformis inplace of Nannochloropsis oculata. Thisreport describes the characteristics of C. vulgaris as arotifer food in comparison with N. oculata and thepresent status of this field.The cell components of C. vulgarissuch as protein content, amino acids, minerals andvitamins are generally similar to those of N. oculata. However, the taxonomic status of thesealgal species are different. Based on thesimilarity of cell components, the dietary value ofC. vulgaris is equal in value to that of N. oculata for rotifer growth. Dietary value ofC. vulgaris can be improved by addition ofvitamin B₁₂. This improved C. vulgaris is currently widely used as an indispensable food organism for rotifer culture. Recent investigationshave shown that the use of the condensed suspensionof C. vulgaris makes it possible tosignificantly increase the rotifer density atharvest. Application of condensed C. vulgaris has made rotifer culture quite easy because theculture of N. oculata is no longer required,and intensive rotifer production in aquaculture cannow be realized.     

Structure of rotifer assemblages in shallow waterbodies of semi-arid northwest Iran differing in salinity and vegetation cover

Rotifers are important components of freshwater ecosystems and sensitive indicators of environmental changes. This study was carried out to test the hypothesis that, among environmental variables, salinity and aquatic vegetation have significant effects on rotifer diversity and abundance. We analyzed rotifer assemblages in the littoral zone of 22 hydromorphologically different shallow waterbodies in West Azarbaijan, Iran. Rotifer diversity and abundance were not significantly associated with basin morphology, but were positively correlated with the percentage of vegetation cover. Salinity and electroconductivity positively influenced rotifer abundance, while they had significantly negative effects on rotifer diversity. Halobiont species from the genera Brachionus, Hexarthra, Synchaeta, and Notholca reached their highest abundances in the waterbodies with pronouncedly higher salinities. Our findings are in agreement with recent records showing that distinct rotifer assemblages occur in saline and non-saline waterbodies. The role of salinity and aquatic vegetation as the most important environmental drivers in shaping rotifer communities is confirmed. The results of this study suggested that environmental changes could be significant on the micro-biogeographical level, and that the interaction of salinity and observed human impact, i.e., trophic level, promote rotifer abundance as sensitive indicators of environmental changes.