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Биология отдельных таксонов Мейоформы
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Биология отдельных таксоновМейоформыВодотоки: турбеллярииFreshwater Biology Volume 44 Issue 1 Page 5 - May 2000 The biology and ecology of lotic microturbellarians Jurek Kolasa Summary 1. More than 200 known species of Microturbellaria occur in running waters world-wide but discovery of many more is likely. Their population density varies greatly as a function of substratum, productivity, phenology and hydrology. The density may exceed 7 000 individuals m-2. The number of species in a single small sample may reach 20. 2. Many species appear to have microhabitat or stream section specialisation but community patterns are obscured to a certain extent by common and eurytopic species. The specialisation is particularly evident in the smaller, lower-order streams. 3. Some of this habitat specialisation is attributable to the ecological origin of species that may include terrestrial, underground, marine and lentic species pools. 4. Feeding habits of Microturbellaria range from omnivory to specialised predation. 5. Quantitative field studies require extraction and examination of live specimens from samples. Such samples pose transportation and storage problems and must be processed within hours of collection. 6. Taxonomy is well resolved for the Northern Hemisphere but is likely to be a major challenge in other parts of the world. In any region, however, new species may demand caution while using current keys to their identification.
Volume 44 Issue 1 Page 15 - May 2000 The biology and ecology of lotic rotifers and gastrotrichs Claudia Ricci* and Maria Balsamo Summary 1. The occurrence of Rotifera and Gastrotricha in the meiobenthos of lotic habitats is reviewed. About 150 rotifer and 30 gastrotrich species are reported in such habitats worldwide. 2. The two phyla share some morphological and biological features that might account for their presence in the meiofauna. Small-size, a soft and elongate body, adhesive glands on the posterior body end, movement through cilia, relatively short life cycles, parthenogenesis and dormant stages are common characteristics. 3. Most species of both taxa inhabiting the superficial sediments in streams and rivers may move downward into the hyporheos in response to both biotic (predation) and abiotic (spates, erosion, desiccation) disturbances. Водотоки: нематоды.Freshwater Biology Volume 44 Issue 1 Page 29 - May 2000 The biology and ecology of lotic nematodes Walter Traunspurger Summary 1. Morphological structures for identifying freshwater nematodes, e.g. buccal cavity, sensory receptors, oesophagus, reproductive organs and tail are described. 2. Most freshwater nematodes belong to the Adenophorea and are characterised by the presence of setae, adhesive glands and conspicuous amphids. 3. Methods for collecting nematodes from the sediments of running water (e.g. corer, pumps), within plants and aufwuchs are listed. Methods for fixation, extracting and preparing nematodes for identification are described. 4. Life history parameters (e.g. generation time, eggs per female) are not available for lotic nematodes but are summarised for free-living nematodes in soil, lakes and seas. Field studies indicate that, in contrast to laboratory experiments with nematode cultures, many species will have a generation time of several months. 5. Abundance and species diversity of nematodes of lotic habitats are provided; more than 100 nematode species inhabit lotic habitats and densities can reach 230 individuals per ml. 6. Links between meiobenthic nematodes and the micro- and macrobenthos are unclear at present. Evidence such as the increased bacterial activity due to nematode grazing suggests that such interactions may be significant. Водотоки: клещи.Freshwater Biology Volume 44 Issue 1 Page 47 - May 2000 The biology and ecology of lotic water mites (Hydrachnidia) A. di Sabatino * R. GereckeAND P. Martin Summary 1. The Hydrachnidia (water mites, Hydracarina) are the most diversified group of the Acari in freshwaters and are abundant and speciose in lotic habitats. Lower-order streams may contain up to 50 species (including benthic and hyporheic forms) and small springs up to 20 crenobiont species. 2. Water mites are grouped into 8 superfamilies, 50 families, 300 genera containing more than 5 000 species. Representatives of all superfamilies (about 3 000 species worldwide) occur in lotic ecosystems, although most lotic species belong to the Hydryphantoidea, Lebertioidea and Hygrobatoidea. Identification of water mite families, genera and subgenera, throughout the world, is possible using taxonomic publications. Keys to species level are also available but mainly for local faunas. Descriptions of larvae and deutonymphs are rare. 3. The life cycle of the Hydrachnidia is unique among the Acari and is similar to that of holometabolous insects, with a heteromorphic parasitic/phoretic larva and two pupa-like resting stages. The larva parasitises mainly insect hosts with apparently no strict host-specificity. Deutonymphs and adults are voracious predators feeding mainly on insect eggs, insect larvae and microcrustaceans. In some cases, water mite parasitism and predation may substantially affect the structure of lotic communities. 4. Most species show a high degree of habitat/microhabitat specialization. Temperature, current-speed, substratum type, physiographic and geomorphological factors are the major determinants of species composition in water mite communities. 5. The complex, fully aquatic, life cycle and multilevel biocoenotic interactions make water mites well suited for the detection of physical and chemical disturbances to lotic ecosystems. 6. Future research should address the distribution, biology, autecology, community dynamics and ecological interactions of lotic water mites.
Volume 44 Issue 1 Page 93 - May 2000 The biology and ecology of lotic Tardigrada Diane R. Nelson* and Nigel J. Marley Summary 1 Tardigrades comprise a micrometazoan phylum that is a sister group of the arthropods. 2 They are components of the meiobenthos in lotic habitats, and 50-70 species have been reported in such habitats world-wide. Approximately 800 species have been identified from all marine, freshwater, and terrestrial habitats. 3 Taxonomy is based primarily on the morphology of the claws, buccal- pharyngeal apparatus, cuticle and eggs. 4 Reproductive modes include sexual reproduction (amphimixis) and parthenogenesis. The sexual condition of individuals may be either gonochorism, unisexuality, or hermaphroditism. Moulting occurs throughout the life of the tardigrade. 5 Latent states (cryptobiosis, including encystment, anoxybiosis, cryobiosis, osmobiosis and anhydrobiosis) enable tardigrades to withstand unfavourable environmental conditions. 6 Population densities, life histories, dissemination and biogeography of freshwater species are poorly known. жүктеу/скачать 1.21 Mb. Достарыңызбен бөлісу:
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