Associations of testate rhizopods (Protozoa) in the plankton of a Malaysian estuary and two nearby ponds

Plankton samples were collected from the Chukai-Kemaman estuary in Malaysia in order to determine the distribution of testate rhizopods in relation to salinity. Two nearby freshwater ponds were sampled for comparison.
In the ponds, 35 species of testate rhizopods were found, 13 of which were not found in the estuary. From the estuary 53 species were found, of which 31 were not found in the ponds. Some species appeared to have been lifted into the plankton by the rising tide. At a generic level, the Arcella species were very similar in both ponds and estuary (Sorensen Index 80), the Difflugia species were moderately similar (Sorensen Index 47), while Nebela and Quadrullela were present in the estuarine samples, but absent from the pond samples.
The salinity gradient ranged from sea water down to a conductivity of 27 μS. All the estuarine stations were tidal. The first freshwater testate rhizopods were found in a region where the conductivity was between 3000 and 4000 μS at high tide. Where the conductivity was below 1000 μS at high tide the number of species rapidly increased, and reached a maximum of 25 in the samples from the lowest conductivities. The flowering tree, Hibiscus tiliaceus , appears to be an indicator of the region where the first freshwater testate rhizopods might be encountered upstream from the sea.     

The terrestrial Protozoan fauna of South Georgia

Summary 75 taxa of Protozoa (18 flagellates, 9 naked rhizopods, 20 testate rhizopods and 28 ciliates) were found in 14 samples of mineral materials, peats, soils and guano collected from the sub-Antarctic island of South Georgia. The results confirm the existence of distinct natural communities of protozoan species related to the different classes of habitat in the sub-Antarctic and maritime Antarctic, but suggest that species characteristic of the maritime Antarctic also occur in the sub-Antarctic and species characteristic of bryophyte peats also occur in soils with angiosperm vegetation. The diversity of the fauna of different habitats can be related to degree of soil development and successional stage of associated vegetation. Comparison of the data on the testate rhizopod fauna of South Georgia with those from other sub-Antarctic locations shows a clear trend of faunal pauperization with latitude.     

The temperate-tropical gradient of planktonic Protozoa and Rotifera

Many flagellates, ciliates and rhizopods appear to be cosmopolitan, at least when considered at the morphospecies level. There are indications of tropical endemics among the ciliates and the rhizopods, but the percentage of endemics appears to be low. Among the rotifers there is a well marked latitudinal gradient, but the picture is complicated by the occurrence of warm water species during hot summers in temperate regions. A further complication has been introduced by the artificial development of heated water associated with power stations. The characteristic rotifer associations of the tropics are governed largely by temperature and salinity. A study of the altitudinal distribution of rotifers in Africa reveals an interplay between latitude and altitude in determining the similarities of the associations to those found in the temperate Old World.     

Paläolimnologische Studien an Testaceen aus Bohrkernen des Latnjajaure (Abisko-Gebiet; Schwedisch-Lappland)

1. Rhizopod tests from 16 cores of sediments from lake Latnjajaure, in Swedish Lapland, were studied and found to show the development of the lake since its formation. Latnjajaure is a oligotrophic mountain lake.
2. All cores contained many remains of rhizopods, most of them intact. Most broken tests could be reconstructed. Postglacial development of a lake could thus be elucidated for the first time.
3. The sediment cores contained 24 species of Testacea, 41.6% of the recent fauna. The rank order of species forming 1 % or more of the total number in the cores is nearly identical with the rank order of recent species.
4. The history of lake Latnjajaure is characterized by Centropyxis aërophila, an oligotrophic species. Periods of beginning eutrophication are indicated by a decrease of Centropyxis aërophila and an increase of Difflugia species, but typical eutrophic species were absent. A dystrophic phase in the development could not be ascertained by means of rhizopods.

     

The response of benthic rhizopods to sediment disturbance does not support the intermediate disturbance hypothesis

Disturbance is one of the mechanisms which counteract competitive exclusion of populations in resource-limited communities, thereby facilitating coexistence and maintaining community species diversity. The intermediate disturbance hypothesis predicts maximum diversity at intermediate disturbance intensities and frequencies. This paper reports results of an experimental test of this hypothesis using a coastal benthic community of rhizopods (Protozoa: Rhizopoda), and experimental sediment resuspension as a simulated natural disturbance. We carried out two experiments of 5 d duration which focussed on the effects of resuspension intensity and frequency, respectively, on the abundance, species richness and on the Shannon-Weaver diversity index of rhizopod communities in surface sediments of natural sediment cores from the coastal southern Baltic. Care was taken to adjust the experimental treatments to the natural disturbance regime in this area.
Twenty-four and 28 rhizopod species were present during the intensity and frequency experiment, respectively. Small bacterivorous rhizopods of the Vannellidae, Cochliopodidae, Paramoebidae and Rhizopoda incertae sedis dominated the communities during both experiments. Rhizopod abundance, species richness and diversity increased towards the end of the intensity experiment, but they did not show effects of disturbance intensity. Similarly, no effects of disturbance frequency were found during the frequency experiment. Our results indicate that coexistence and community diversity maintenance in benthic rhizopod communities, and probably in benthic heterotrophic protistan communities in general, may rely on different mechanisms than intermediate disturbance, such as trophic niche separation and high rates of dispersal and colonisation.     

Eisen und Mangan in pazifischen Tiefsee-Rhizopoden und Beziehungen zur Manganknollen-Genese Iron and Manganese in Pacific Deep-sea Rhizopods and Relationships to Manganese Nodule Formation

The Pacific deep-sea bottoms are dominated by rhizopodan Protozoa. Their abundance on manganese nodules and in the associated sediments suggests a contribution to nodule formation, though direct evidence is still lacking. Attention is called to iron contents in solid excretion products of some sessile rhizopods that may contribute to the initiation of manganese deposition and nodule growth. Manganese is scarce in the faecal pellets of sediment-dwelling rhizopods. This is discussed in context with questions regarding manganese mobilization in pelagic sediments.     

Benthic–pelagic coupling: a comparison of the community structure of benthic and planktonic heterotrophic protists in shallow inlets of the southern Baltic

1. The taxonomic composition, abundance and biomass of heterotrophic protists (ciliates, heterotrophic flagellates (HF), rhizopods and actinopods) in the sediment and water column of shallow inlets of the Southern Baltic was studied under a variety of environmental conditions during 1996–1997. A shallow, highly eutrophic station and a deeper, less eutrophic station were compared.
2. Community biomass ranged from 0.12 to 0.34 μg C cm?3 in the water column and from 1.5 to 105 μg C cm?3 in the sediment. Heterotrophic protists dominated zooplankton biomass at both stations (73% and 84% mean contribution), while they were of minor importance within the zoobenthos. Expressed per unit area, benthic biomass contributed a significant part (44% and 49%) to the total heterotrophic protistan community at both stations.
3. Although the methodology for counting ciliates and HF was focussed on a high taxonomic resolution, the results reveal some general trends in the distribution of heterotrophic protists: protozooplankton biomass was dominated by flagellates (80% mean biomass contribution) at the shallow station and by ciliates (73% mean biomass contribution) at the deep station. In the benthos at both stations, ciliates were the dominant protozoans, followed by the hitherto little‐studied rhizopods (25% and 35% mean biomass contribution) and flagellates.
4. The degree of benthic–pelagic coupling differed between taxonomic groups. Benthic and pelagic communities of ciliates showed little taxonomic overlap. In contrast, many heterotrophic flagellate species were found both in the benthos and in the pelagic. These benthic–pelagic species contributed significantly to the biomass of HF in the water column. The planktonic rhizopod community consisted of a subset of those species found in the benthos.
5. The abundance of benthic and pelagic protists was positively correlated at the shallow station, but taxonomic data indicate that the direct exchange between benthic and pelagic communities was only partly responsible.     

The role of the floodplain gradient in structuring of testate amoebae communities in the Ilych River

Forty-two testate amoebae taxa were identified in alluvial soils of floodplain islands in the Ilych River. Among the pedo- and eurybionts, there were aquatic rhizopods. Along the floodplain transect (willow meadow ?? deciduous forest ?? coniferous forest), the testate amoebae community changed directly. There are spatially homogeneous (low beta-diversity) testacean communities but species rich on the local level (high alpha-diversity) within forests. Within willows and meadows, communities are characterized by low alpha-diversity and high heterogeneity that leads to high gamma-diversity.     

Diverse fossil amoebae in German Mesozoic amber

Fossil amoebae are very rare, although their evolutionary history extends back into the Proterozoic. The Cenomanian amber of Schliersee (southern Germany) is very rich in micro-organisms and contains the highest diversity of fossil freshwater rhizopods (Gymnamoebia and Testacealobosia) yet discovered. Altogether seven testate amoebae and one gymnamoebian species are recorded from this Mesozoic amber. The four newly discovered taxa described in this paper can be assigned to the extant species Centropyxis delicatula , Centropyxis hirsuta , Phryganella acropodia and Phryganella paradoxa . Over 200 individuals of Phryganella paradoxa are preserved. Together with their syninclusions, the amoebae are species of limnetic or limnetic–terrestrial microcoenoses. The presence of 100-myr-old fossils with extant representatives suggests evolutionary stasis of these freshwater amoebae. However, not all modern testacean families have been recorded from Mesozoic limnetic habitats. Our experimental studies verify that naked and testate amoebae can be embedded in resins.     

Ecological studies on crater lakes in West Cameroon. Debundsha Lake

Cape Debundsha receives 10 m (400 inches) of rain per year, and the water of the small crater lake on the cape has one of the lowest conductivities in Africa (11–13 µmho/cm/20 C). The lake has a maximum depth of 13·5 m. At the time of our visit in April 1972 the lake was stratified with a depletion of oxygen in the hypolimnion. The phytoplankton was dominated by Botryococcus , and the zooplankton was dominated by the ostracod Oncocypris debundshae. Both these organisms are closely associated with the surface film. Other zooplankters included Thermocyclops hyalitws , and in deeper water during the daytime the larvae of Chaoborus ceratopogones.
The fauna of the lake includes 12 species of testacean rhizopods, six species of rotifers, two oligochaetes, one snail, seven crustaceans, 15 insects and three acarines. Of the last group two species were new to science and one had been found only once previously. The ectoproct polyzoan, Lophopodella carteri , is recorded for the first time from West Africa, and the second time from Africa. The general impression of the fauna is one of sparseness, with an unusually high proportion of larval Odonata.     

弄岗黑叶猴旱季食物营养组分及其对食物选择的影响

正蛋白质与纤维素的比值以及能量高低是影响灵长类动物食物选择的重要因素(Oftedal,1991;Waterman and Kool,1994;Chapman and Chapman,2002;Wasserman and Chapman,2003;Hanya et al.,2007;Huang et al.,2010),但它们是否影响疣猴的食物选择目前尚具有较大的争议。Waterman     

A review on the occurrence and taxonomy of heterotrophic protists in extreme acidic environments of pH values ≤ 3

The occurrence and some important taxonomic problems of heterotrophic protists from extremely acidic (pH 3) environments are briefly discussed. Almost all information on the occurrence of heterotrophic protists from extremely acidic environments is restricted to acid mine drainage (AMD) or streams influenced by AMD. Most of the information is provided for ciliates. Very little information is available on the occurrence of flagellates, rhizopods and heliozoa in this environment. Within the ciliates Urotricha, Vorticella and Oxytricha dominate in acidic mining lakes. Actinophrys sp. is the most important heliozoan in these environments. There are many taxonomic problems which are not solved so far. Live observations and taxonomic methods adapted to the extreme chemical matrix are necessary for correct identification.     

Food choice in Siganus fuscescens: influence of macrophyte nutrient content and availability

Using multiple‐choice feeding experiments, the selection of six species of macrophytes by the herbivorous rabbitfish Siganus fuscescens was examined. The rabbitfish showed distinct food choice in the laboratory; however, selection of macrophytes by S. fuscescens was not related to their absolute nutrient content (nitrogen, carbon, energy and ash free dry mass). Nutrient assimilation estimates showed that the macrophytes which were most preferred were those that S. fuscescens assimilated best. In S. fuscescens , the macrophytes that were preferred passed through the gut significantly faster than the less preferred species. Gut transit time had a significant effect on the absolute value of a food item in terms of net nutrient gain per unit time. This study showed that food value could be inferred from the absolute nutrient content of the macrophytes. Thus both the ability to assimilate nutrients as well as the absolute nutrient content of macrophytes must be quantified when assessing food value.     

Food selection by freshwater snails in the Gezira irrigation canals,Sudan

Stomach content analysis was carried out on samples of the freshwater snail species Biomphalaria pfeifferi, Bulinus truncatus, Bulinus forskalii (Pulmonata, Planorbidae), Lymnaea natalensis (Pulmonata, Lymnaeidae), Melanoides tuberculata, Cleopatra bulimoides (Prosobranchia, Thiaridae) and Lanistes carinatus (Prosobranchia, Ampullariidae) from different irrigation canals in Sudan. In order to evaluate overlap in diet selection among these species, sites with two or more of the above-mentioned species present were selected. For some species food choice was examined in relation to size groupings. In addition, samples of Marisa cornuarietis (Prosobranchia, Ampullariidae) from small ponds in Sudan, samples of Biomphalaria pfeifferi and Helisoma duryi (Pulmonata, Planorbidae) from drainage canals in an irrigation scheme in northern Tanzania, and samples of H. duryi from fish ponds in the coastal area of Kenya were also analysed. The results indicate a great similarity in the food choice of these species, especially among the pulmonate species. All species feed on fine detritus, epiphytic algae and decaying macrophytes. No fresh fragments of aquatic macrophytes were found and animal remains were found only on a few occasions. However, the stomach contents of the ampullarid species were characterized by large fragments of dead macrophyte tissue, while the composition of the finer particles showed a great resemblance to that of the pulmonate species. The diet of the thiarid species is essentially the same as that of the pulmonate species, although in one site Cleopatra bulimoides showed a greater preference for green algae. Apart from the avoidance of blue-green algae, there was little evidence of selection of certain algal components of the Aufwuchs for the pulmonate species. Detritus constitutes the major component of the stomach content of all these snail species.     

Associations of zooplankton in six crater lakes in Arizona, Mexico and New Mexico

Zooplankton associations in six crater lakes have been compared by means of indices of similarity and diversity, and by k -dominance curves. The lakes covered a wide range of salinities and vegetational characteristics.
The total number of species identified were: Protozoa, 34; Rotifera, 48; Gastrotricha, 7; Crustacea, 24; and Chaoborus larvae, 2; giving an overall total of 115. The numbers of zooplankton species in each lake varied from 68, in a richly vegetated fresh crater lake in Arizona, to one in a highly saline lake in New Mexico.
Testate rhizopods and gastrotrichs were not found in the more saline lakes. A comparison of the rotifer associations with those of crater lakes in other parts of the world shows that there is a general tendency for a reduction in the total number of species when the conductivity rises above 400 μS cm⁻¹ 20°C, and when the conductivity reaches 10,000 μS cm⁻¹ 20°C the number of rotifer species is usually reduced to two. The two species found at high salinities show some variation in different parts of the world, but generally include species of Brachionus and Hexarthra.
There is a general tendency for the number of rotifer species in a crater lake to increase with increasing vegetation, at least up to the stage where there is a dense, zoned vegetation, and before a complete mosaic of vegetation covers the lake.     

A re-assessment of the relative importance of ciliates,rhizopods and rotatorians in the ecology of activated sludge

Summary The faunas of two activated sludge plants were surveyed for 12 month periods. Over 60 species were distinguished including annelids, nematododes, rotatorians, and flagellate, rhizopod and ciliate protozoa. The relative qualitative values of the predominant species were found to differ in terms of requency of occurence, average numbers, and mean biomass. Animals predominant in biomass include rotatorians - Lecane sp. ; peritrich ciliates - Vorticella spp. and Epistylis spp. ; and rhizopods - Flabellula sp., Cochhopodium sp. and Arcella sp. The rhizopods appear to be of equal ecological importance as the ciliates, and the rotatorians are also of some significance.

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Resumé On a observé pendant douze mois les faunes des deux installations de tartre active. On a distingué plus de soixante espèces comprenant: annelides, nematodes, rotatoriens et protozoaires flagelles, rhizopodes et ciliés. La relative valeur qualitative des espèces predominantes differaient en terme de fréquence occurentelle, de nombre moyenne, et de biomasse courante. Les animaux prédominants en biomasse comprennent rotatoriens - Lecane Sp., peritriches - Vorticella Spp., et Epistylis Spp., et rhizopodes - Flabellula Sp., Cochhopodium Sp., et Arcella Sp. Les rhizopodes semblent être de même importance écologique que les ciliés, et les rotatoriens sont aussi de quelque importance.

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Chelsea College of Science and Technology, University of London

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Present Address: Department of Zoology, University of Ibadan     

广西扶绥黑叶猴主要食物种类能量含量的初步研究

能量对灵长类食物选择的影响是营养生态学中重要的组成部分。为了研究黑叶猴食物能量及其对食物选择的影响,采用焦点动物取样法和连续记录法在广西扶绥观察记录野生黑叶猴的觅食行为;每月观察结束后采集被取食的植物部位样本,利用全自动氧弹热量计测定其能量。结果表明,黑叶猴食物中嫩叶最高（58.5%）,其次为果实（12.4%）,其他种类依次为成熟叶（12.1%）、种子（10.6%）、花（4.3%）和树皮（2.4%）。在不同的生活型食物中,乔木占48.5%,灌木占34.6%,藤本和草本分别占19.4%和17.2%。各种食物平均能量为17.09 kJ/g,月平均能量在16.52 -17.61 kJ/g之间变化。种子的能量最高,达19.52 kJ/g,最低为成熟叶,仅为16.84 kJ/g。不同生活型植物中,灌木能量最高,达17.52 kJ/g,草本植物最低,仅为15.73 kJ/g。不同植物种类之间能量有显著的差异（P < 0.001）。取食量最多的15种和最少的15种植物之间平均能量有显著差异（P < 0.001）,但在月份间、雨季和旱季间则无显著差异（P > 0.05）。取食不同种类的时间与其平均能量之间无显著相关关系（P = 0.40）,食物能量含量并非影响黑叶猴食物选择的主要原因,其觅食策略需要进一步的研究。     

Ecology of terrestrial testate amoebae assemblages from coastal Lowlands on Devon Island (NWT,Canadian Arctic)

Summary Fifty-seven taxa belonging to 17 genera of testate rhizopods were recorded in samples of mosses, soils and lichens, collected from the Truelove and Sparbo Hardy Lowlands on the high arctic Devon Island (NWT, Canada). Different groups of habitats are characterized by particular assemblages of Testacea species, with the quantity and quality of the available water as important ecological parameters. The Assulina muscorum-Corythion dubium assemblage characterizes the most dry and acidic moss habitats, while the Paraquadrula irregularis assemblage is to be found in wet and rather neutral habitats. The sedge moss meadows with their more moderately coarse textured and poorly drained soils, bear a Plagiopyxis callida-Plagiopyxis declivis soil-dwelling testate amoebae assemblage. The Centropyxis minuta assemblage lives in the most coarsely textured soils. pH seems to play a subordinate role, not only in the mosses but also in the soils. Multivariate methods (cluster analysis and CANOCO) have been used to separate these different assemblages.     

Defining “high quality” food resources of herbivores: the case for meadow voles (Microtus pennsylvanicus)

Summary Food availability, food utilization patterns and levels of some nutritional factors in plants were studied in 1984–85 in an old-field community supporting low to moderate densities of meadow voles (Microtus pennsylvanicus). Food choice and preference indices were positively related to levels of proteins, and negatively related to levels of total phenolics and ADL fibers in plants. High quality resources for voles were resources that had the highest amount of proteins, and the lowest level of total phenolics and ADL fibers among available plant species. There were only two plants species among the available ones that possessed these characteristics, Festuca rubra and Vicia cracca and they represented 25 to 50% of the available biomass during summer. Vole densities of up to 64 animals/ha were therefore not limited by the availability of high quality resources. Fecal analyses performed on 267 animals in 1984 and 269 voles in 1985 showed that all voles ate high quality resources. Meadow voles appear to choose foods with high protein content and low levels of digestion inhibitors, and not on the basis of caloric content or availability. These observations contradict predictions arising from current antiherbivore hypotheses and lead us to reconsider these models in light of this new evidence.