Principal directions of the evolution of Monimotrochida

Phylogenetic relations among the main groups of Monimotrochida are considered. The principal directions of monimotrochid evolution were defined by comparative investigations of mastax morphology (SEM), basic body structures, and general biology. On the basis of these results we propose a revision of previous rotifer taxonomy. We suggest to place the Monimotrochida in the order Protoramida divided into two suborders Flosculariina and Conochilina.     

Bdelloid Rotifers (Rotifera, Bdelloidea) as a Component of Soil and Land Biocenoses

Morphological, physiological, and ecological adaptations of bdelloid rotifers (phylum Rotifera, class Bdelloidea) to the conditions of soil and land biocenoses are described. The morphological structures, obligate parthenogenesis, and anhydrobiosis allowed these rotifers to colonize various semiaquatic areas with sharp fluctuations of environmental conditions: the edaphon, coniferous and deciduous litters, mosses, and lichens. The role of bdelloid rotifers in the food web and environmental indication is noted. Controversial problems concerning the origin of this group of worms are considered.     

On the evolutionary pathways of speciation in the genus Notholca

An attempt is undertaken to determine criteria and limits of taxonomic rank in the genus Notholca proceeding from the standpoint of level-values of the characters evolution. Level-values of characters were established using Vavilov's principle of homologic series of hereditary variability. As a result of taxonomic revision such terms as group of species, species and subspecies are recommended. Analysis of the scheme of relations between representatives of the genus and data on their ranges gives a clue to relations between phylogeny and geographic distribution of the group over the vast territory of the Asian continent which may have been its centre of speciation.     

Mastax morphology under SEM and its usefulness in reconstructing rotifer phylogeny & systematics

Biological response could not be predicted based on chemical concentration of the sediment contaminants. Bioassays integrate the response of test organisms to contaminants and nutrients. Comparative results of five acute bioassays indicated that Neubauer phytoassay was the most sensitive. The microbial biomass and algal growth tests indicated a response to the availability of contaminants and nutrients. These results suggest the usefulness of a diversity of bioassays in toxicity testing of sediment contamination.     

Larval metamorphosis in sessile rotifers

Postnatal development of six species of sessile rotifers in the families Flosculariidae (Floscularia decora, Lacinularia flosculosa, Limnias ceratophylli, Ptygura crystallina) and Collothecidae (Collotheca ornata, Stephanoceros fimbriatus) was investigated by observing free-swimming and newly settled larvae until they metamorphosed into adults. Three variants of metamorphosis were observed. A hypothetical explanation of changes of the coronal construction of orders Gnesiotrocha and Pseudotrocha is considered.     

Notholca dongtingensis (Rotifera: Monogononta: Brachionidae), a new species from Dongting Lake,China

Notholca dongtingensis n.sp. was found in the second largest lake of China, Dongting Lake. It is related to Notholca labis Gosse, 1887 and N. kozhovi Vassilijewa & Kutikova, 1969. Its main distinguishing taxonomic features are a square-oval lorica, very short anterior spines, anterior lateral spines curving outwards and protrusile posterior margin of the ventral plate. This revised version was published online in July 2006 with corrections to the Cover Date.     

Phenomenon of obligate parthenogenesis in rotifer (Rotifera, Bdelloida)

A comparative analysis of biological and morphological organization of obligate parthenogenous bdelloids and heterogonic monogononts clarifies the specificity of bdelloids' environmental adaptation and variability. It is shown that phenotypic polymorphism of bdelloids differs from that of monogononts. The heterogonic Monogononta are characterized by tremendous phenotypic diversity in body structure adapted to different biotopes in continental waters. This diversity is reflected also in structure of corona and mastax used as major criteria for definition of high range taxa (classes, orders). The polymorphism of bdelloids manifests itself in variability of tiny morphological structures connected with living in restricted volumes of water, mainly in terrestrial biotopes. Being isolated from other Rotifera at the first stages of evolution, bdelloids have been specialized for living under extremely unstable terrestrial conditions that led to the development of anhydrobiosis and loss of amphimixis. Variability of bdelloids is not connected with characters of high taxonomic ranks and has principally different nature in comparison with monogononts. Tempo of specialization seems to be slower in obligate parthenogenous rotifers than in heterogonic ones.     

Brachionus calyciflorus Pallas (Rotatoria) in Inland Waters of Tropical Latitudes Brachionus calyciflorus Tropical in Waters

The widely distributed Brachionus calyciflorus was studied for morphological variation based on material from all tropical areas. The subspecies B. calyciflorus borgerti Apstein is redescribed and its subspecific status affirmed. Various forms with local distributions were noted and described and the morphological differences are attributed to a variety of possible factors. From the distribution patterns it is clear that rotifers are governed by the general principles that apply to other invertebrates and are not cosmopolitan. There are evidently dispersal centres for Brachionus calyciflorus and its subspecies borgerti.     

Parallelism in the evolution of rotifers

The carbon uptake by the roots of three common submersed macrophytes, Myriophyllum spicatum, Heteranthera dubia and Vallisneria americana, was measured in situ under a range of pH and dissolved inorganic carbon (DIC) concentrations. After 4–8 weeks of growth in ¹⁴C labelled sediments, less than 1.5% of the total C found in the shoots originated from root uptake. Between species, significant differences in C uptake by the root were found and root development alone could explain most of the observed variance (84%). C uptake by the roots of aquatic macrophytes thus appears to be restricted to small, rosette-shaped plants growing in poorly mineralized waters.