SEM observations on the cuticles of some decapod crustaceans

The cuticles of the crayfish Austropotamobius pallipes (Lereboullet), and the crabs Cancer pagurus L. and Carcinus maenas (L.), have been examined with the scanning electron microscope. Laminae are composed of sheets of horizontal fibres which subsequently are into the inter-laminae. The inter-laminae contain sheets of fibres which are at a slight angle from the horizontal between sucessive laminae. The disposition of the pore canals is clearly related to fibre pattern. The sinuous macrofibres described by Dennell (1973) are discrete from the pore canals.     

A revised checklist of planktonic diatoms and dinoflagellates from Helgoland (North Sea,German Bight)

A checklist based on net samples taken twice weekly from 2001 until May 2003 is presented. Identification is based on observations under direct light microscopy and after taking some organisms in culture. The checklist includes 227 taxa observed at the Helgoland Reede sampling station. One hundred and thirty-two species of diatoms from 53 genera and 95 species of dinoflagellates from 35 genera have been recorded from net samples and cultures. Thirty-five diatom and 28 dinoflagellate taxa were documented in the Helgoland phytoplankton for the first time. The list does not claim to be complete, but provides an updated list of the taxa found at Helgoland and, for convenience, also includes data published for different adjacent areas.Communicated by K. Wiltshire     

Benthic diatoms in the salinas of the Dry Creek saltfields,South Australia

Given that diatom assemblages are a well-recognised method of characterising the water quality in freshwater streams, it seems reasonable to investigate its applicability to solar saltfields. A summer collection of benthic diatoms was undertaken in the salinas of the Dry Creek solar saltfields in South Australia for this purpose. The facility inputs seawater both from a low nutrient samphire creek and poorer quality, high nutrient samphire creek. Salinity and nutrient status of the pools and concentrating salinas have been thoroughly characterized over many years. The addition of JJ periphytometers to the sampling regime in the summer of 2001–2002 allowed the collection of benthic diatoms from these sites. Of the 69 species collected during the study, 16 species occurred only in oligotrophic waters with salinities less than 70 g/l TDS (total dissolved solids). Twenty species of diatoms occurred only in the eutrophic waters with salinities less than 70 g/l TDS, eight species were restricted to the hypersaline ponds and the remainder were undiscriminating in their ecological preferences. Guest Editor: John M. Melack Saline Water and their Biota     

Diatom communities from the sub-Antarctic Prince Edward Islands: diversity and distribution patterns

During an extensive survey of the freshwater and moss-inhabiting diatoms of the Prince Edward Islands, a total of 214 taxa belonging to 60 genera were found. Three main communities can be found on the two islands. A large part of the samples was grouped into an aquatic group, bringing together all samples from lentic and lotic waterbodies. A second, contrasting, group was formed by all dry samples whereas in a third group all habitats with higher mineral contents were found. The habitats differed clearly in taxa composition reflecting that way possible environmental differences. Although the diatom composition between the two islands of this island group (Marion and Prince Edward Island) showed some minor qualitative differences, no marked quantitative differences have been observed. The diatom flora shows a distinct similarity with the other islands in the southern Indian Ocean, such as the Crozet archipelago and the Kerguelen Islands forming a biogeographical entity in this part of the ocean, distinctly separated from the non-marine diatom flora in other parts of the (sub-)Antarctic Region.     

Fish species diversity as indicator of pollution in Ikpoba River, Benin City, Nigeria

The composition and distribution of fish in the Ikpoba reservoir were investigated. A total of fifty-seven species of fish belonging to thirty-nine genera and twenty-three families were recorded. Of these, 46 species were recorded at the upstream station, 35 at the reservoir, 24 at the slope and 32 at the downstream station. The percentage compositions were 81%, 61%, 42% and 56% respectively. There were 21 ubiquitous species while the distribution of the other species showed variability indicating effects of habitat condition. Species diversity indices showed that the upstream section was richer, more diverse with species more evenly distributed than the other stations. Heavy metal analysis of the dominant fish species showed higher mean levels than the background levels. Metal contamination factor and bioaccumulation quotient were variable in the fishes and in the stations but followed a ranked order of 3 > 2 > 4 > 1 by station. Comparison of stations using ANOVA revealed a significant difference (P < 0.05) between the upstream and the slope stations.     

The influence of irradiance,photoperiod and temperature on the growth kinetics of three planktonic diatoms

The influence of irradiance, photoperiod and temperature was determined for the growth kinetics of the diatoms Aulacoseira subarctica, Stephanodiscus astraea and Stephanodiscus hantzschii and the results compared with those of cyanobacteria. Irradiance and photoperiod relationships were qualitatively similar to those for cyanobacteria in that: (1) growth rate (K) was proportionally greater under short photoperiods, with ratios of K under continuous light to K under 3:21 light:dark (LD) cycles of 1·50, 1·80 and 2·96 for A. subarctica, S. astraea and S. hantzschii respectively; (2) at subsaturating irradiances, K was proportional to irradiance and independent of temperature with a negligible predicted maintenance growth rate requirement. Apparent growth efficiencies (GE) at subsaturating irradiances were 0·26±0·03, 0·42±0·03 and 0·50±0·03 divisions mol^-1m² for A. subarctica, S. astraea and S. hantzschii with the values for Stephanodiscus species comparable to values for Oscillatoria species. Under a 3:21 LD cycle at 4 °C, light-saturated growth rates were 0·066±0·004, 0·197±0·033 and 0·285±0·018 divisions day^-1 for A. subarctica, S. astraea and S. hantzschii. S. hantzschii growth rate at 4 °C exceeded maximum Oscillatoria growth rates at 23 °C and the S. astraea growth rate at 4 °C was equivalent to O. agardhii growth rate at 20 °C. Temperature increases above 4 °C gave Q₁₀ values between 4 °C and 12 °C of 3·68, 2·39 and 1·92 for A. subarctica, S. astraea and S. hantzschii, but higher temperatures resulted in minor increases in K. S. astraea growth rate peaked at 16 °C, declining sharply at higher temperatures. February to March in situ growth rates in Lough Neagh, mean temperature 4·3 °C, showed that the A. subarctica in situ K of 0·058 divisions day^-1 was close to the laboratory K at 4 °C, but that S. astraea in situ K of 0·101 divisions day^-1 was lower than the laboratory K at 4 °C.     

Taxonomy and distribution of some katydids (Orthoptera Tettigoniidae) from tropical Africa

Results of the study of specimens collected in tropical Africa and preserved in different European collections and museums are reported and extensively illustrated. The following three new species are described: Horatosphaga aethiopica sp. n., Dapanera occulta sp. n. and Cestromoecha laeglae sp. n. In addition, new diagnostic characters or distributional data for Ruspolia differens (Serville, 1838), Thyridorhoptrum senegalense Krauss, 1877, Horatosphaga leggei (Kirby, 1909), Horatosphaga linearis (Rehn, 1910), Preussia lobatipes Karsch, 1890 and Dapanera eidmanni Ebner, 1943 are reported. Finally, Symmetropleura plana (Walker, 1869) is proposed to be transferred to the genus Symmetrokarschia Massa, 2015, Conocephalus carbonarius (Redtenbacher, 1891) to the genus Thyridorhoptrum Rehn & Hebard, 1915; the genus Gonatoxia Karsch, 1889 is proposed to be synonymized with Dapanera Karsch, 1889.     

On a new species of electric catfish from Kainji, Nigeria, with some observations on its biology

A new species of electric catfish, Malapterurus minjiriya , from Kainji, Nigeria, is described and a key for separating it from the two other known species is given. Notes on some aspects of the biology of the electric catfishes in Lake Kainji, Nigeria are included.     

New genera,species and records of Phaneropterinae (Orthoptera,Phaneropteridae) from sub-Saharan Africa

The results of the study of many specimens preserved in different European museums are reported. The tribe Terpnistrini Brunner von Wattenwyl, 1878 is resurrected. The distribution of the following species is enhanced: Pardalota asymmetrica Karsch, 1896, Diogena denticulata Chopard, 1954, Diogena fausta (Burmeister, 1838), Plangiopsis adeps Karsch, 1896, Poreuomena sanghensis Massa, 2013 and Tylopsis continua (Walker, 1869). Further, for their peculiar characteristics, two African representatives of the American genus Symmetropleura Brunner von Wattenwyl, 1878 are included in two new genera: Symmetrokarschia africana (Brunner von Wattenwyl, 1878), comb. n. and Symmetroraggea dirempta (Karsch, 1889), comb. n. A new genus and species from the Democratic Republic of Congo, Angustithorax spiniger gen. n., sp. n., and a new genus and species from Tanzania, Arostratum oblitum gen. n., sp. n. are described. Finally Melidia claudiae sp. n. and Atlasacris brevipennis sp. n. are described and compared with related species.     

The diversity and distribution of diatoms: from cosmopolitanism to narrow endemism

It has been claimed that microbial taxa will not exhibit endemism because their enormous populations remove dispersal as an effective constraint on geographical range. Here we review evidence that challenges this ubiquity hypothesis for the most speciose group of microbial eukaryotes, the diatoms. Detailed taxonomic inventories using fine-grained morphological characteristics, molecular markers, and crossing experiments have revealed that the geographic distribution of diatoms ranges from global to narrow endemic. Records of human-mediated introductions of exotic species further provide a strong indication that geographic dispersal was limiting in the past. Finally, recent studies have revealed that diatom community structure and diversity are influenced by geographical factors independent of environmental conditions. Diatom communities are thus regulated by the same processes that operate in macro-organisms, although possibly to a different degree, implying that dispersal limitation is significant and the endemism observed in isolated areas is real. These results underscore the pressing need to (1) continue research into diatom biology, ecology and the factors driving diatom species diversity and geographic distributions, and (2) protect relatively isolated areas against further introductions of exotic species. Special Issue: Protist diversity and geographic distribution. Guest editor: W. Foissner.     

Valve formation in diatoms and the fate of the silicalemma and plasmalemma

Summary In two species of the diatom genusMelosira the inner profile of the silicalemma fuses with the plasmalemma covering the older part of the cell at, or slightly before, maturity of the new siliceous cell wall component. Subsequently, the outer profile of the silicalemma and the remainder of the plasmalemma are cut off. Though there are indications that the valves may continue to add silica after this time the wall component now lies to the outside of a membrane which must,de facto, be considered the plasmalemma. When cingula move apart as development continues the membrane fragments are allowed to disperse and it is thought unlikely that they contribute to the formation of an organic investment of the siliceous components of the frustule.     

The occurrence of potentially toxic dinoflagellates and diatoms in a subtropical lagoon, the Indian River Lagoon, Florida, USA

The occurrence of potentially toxic phytoplankton species was examined over a 5-year period in a region of the Indian River Lagoon in Florida that has recently been subject to ecologically significant events, putatively related to algal toxins. The results of the study reveal a significant presence of two species of phytoplankton that have been shown to be toxic in Florida or other regions of world, the dinoflagellate Pyrodinium bahamense var. bahamense and the diatom Pseudo-nitzschia pseudodelicatissima. Concentrations of the former species reached 638,000 cells l⁻¹ and concentrations of the latter reached 23.9 million cells l⁻¹. In addition, the abundance of one of these species, P. bahamense var. bahamense appears to have increased over the 5-year study period from 1997 to 2002. It may be hypothesized that rainfall events following a regional drought period resulted in a flushing of bioavailable phosphorus and nitrogen into the Indian River Lagoon that stimulated P. bahamense var. bahamense blooms. The significance of these results is discussed within the context of the ecology of this flow-restricted lagoon.     

Development of molecular tools for the detection of freshwater diatoms

This study was undertaken to develop a reliable and reproducible procedure for the detection and quantitative determination of diatoms in environmental samples. A comparative study of seven different DNA extraction kits was carried out to establish conditions for analysis of diatom containing samples. The best performers were identified using both standard and real-time PCR. We show that the yield of diatom DNA is generally quite low when using commercially available extraction kits; in addition, a new protocol was devised to obtain samples suitable for DNA amplification without the need to perform all the steps required for DNA extraction. This method was tested on environmental samples spiked, in a wide range of total cell mass, with the rarely occurring diatom Neidium affine together with a highly species-specific oligonucleotide designed on the small subunit (SSU) rRNA gene. Thus, we propose a fast and effective procedure that, combined with the use of species-specific oligonucleotide probes can detect minute amounts of a spiked diatom within a complex diatom community. This study provides experimental conditions for a fast and accurate detection of diatoms, and demonstrates the feasibility of the use of molecular tools in the evaluation of water quality.     

An ecological study of three freshwater ponds of hyderabad-India IV. the phytoplankton (diatoms,euglenineae and myxophyceae)

Data on the ecology of Diatoms, Euglenineae and Myxophyceae in three freshwater ponds, differing in chemical composition and algal flora, situated in the vicinity of Hyderabad-India are presented. An attempt has been made to isolate various genera into groups, as their multiplication depended on particular ranges of a single chemical factor or set of factors. Several species could be separated into seasonal forms as they occur in particular periods of the year. Others could be grouped under indifferent forms as these are neither influenced by fluctuations in chemical factors nor by seasonal changes.     

Influence of environmental factors on the development of the valve in diatoms

Summary The species-specific form and structure of the diatom shell is variable within a given genetical reaction-norm, depending on the dynamic interrelation between cell and environment. The appearing modifications—based on quantitative disarrangement of construction-units as well as on a change in size and outline—can be understood as the morphological expression of a changed metabolism which has become necessary for adaption to adverse conditions. The diatoms react very sensitively, especially to the salinity factor, whereby actually two alternatives of adaption occur: a vegetative, in building resting spores (f.i., Navicula cuspidata) and a generative (f.i., Anomoeoneis sphaerophora, Surirella peisonis).Teratologies have been found in totally unbalanced surroundings (especially under conditions of ion unbalance), where the usually symmetrical forms have lost the coordination of the construction-units to each other (f.i., Surirella peisonis). They supply good criteria in clarifying the problems concerning pattern development.Dedicated to Univ.-Prof. Dr. H. A. v.Stosch's 70th Birthday.     

On the phytoplankton of Awba reservoir, Ibadan, Nigeria

The physico-chemical characteristics and phytoplankton of Awba reservoir in the University of Ibadan, Nigeria, were monitored to determine the impact of eutrophication on phytoplankton composition. The principal component analysis identified three major components influencing the physicochemistry of the water, namely trace metals, dissolved oxygen and ionic composition. Comparative analysis with a previous study showed a phenomenal increase in zinc, copper and iron levels over a 10-year period. Furthermore, the ferruginous nature of the soil contributed to the high levels of iron which exceeded the World Health Organization Standards for drinking water quality. The most abundant phytoplankton species was Microcystis aeruginosa which has been implicated in toxic blooms in freshwaters. The conditions favouring cyanophyte blooms and their implications are discussed.     

Cladistic analysis of some freshwater araphid diatoms (Bacillariophyta) with particular reference toDiatoma andMeridion

Interrelationships of the ribbed araphid diatoms have been reinvestigated using a cladistic analysis of a revised morphological dataset. The presence of silicified transapical ribs has previously been used to distinguish between different groups and its ability to serve as a distinguishing feature is reevaluated. The importance of valve symmetry, not fully appreciated in a previous paper, is examined. The evolution of heteropolarity, and its importance in taxonomy appear more complex than is implied by a simple dichotomy dividing groups of species into heteropolar and isopolar forms, involving an inferred evolutionary transformation from one condition to the other. This analysis proposes a close relationship betweenDiatoma, Fragilariforma, Asterionella, Distrionella, Meridion, Tabellaria, andTetracyclus. It also confirms the sub-division ofDiatoma into two closely related taxa. The genusMeridion, however, should not include both heteropolar and isopolar species in a single genus. Although the species are closely related, the isopolar species are more closely related toTabellaria andTetracyclus than they are to the heteropolar species ofMeridion.     

Geothermal diatoms: a comparative study of floras in hot spring systems of Iceland,New Zealand,and Kenya

Diatom floras were examined from geothermal environments in three contrasting tectonic settings. These included subduction-related acid and alkaline springs in New Zealand; alkaline springs along a divergent plate boundary on Iceland; and alkaline springs in the Kenya Rift. These shallow (<1 cm) aquatic environments vary considerably (e.g., temperature: 21.3–99°C; pH: 2.1–9.65; 56.41–643 mg l⁻¹ SiO₂). Diatoms form an important component of geothermal floras at temperatures of <45°C. The floras from New Zealand are distinguished by the common occurrence of Pinnularia. Icelandic springs have a variety of Fragilariaceae. Navicula and Anomoeoneis are most common in the Kenyan springs. Statistical analyses suggest that the diatoms cluster into seven major groups. The most common taxa include: Achnanthidium exiguum v. heterovalvum (Kras.) Czarn., Anomoeoneis sphaerophora (Ehrenb.) Pfitz, Brachysira brebissonii f. thermalis Grun., Caloneis bacillum (Grun.) Cl., Craticula cuspidata (Kütz.) Mann, Diadesmis confervacea Kütz., Epithemia argus (Ehrenb.) Kütz., Frustulia rhomboides (Ehrenb.) DeT., Hantzschia amphioxys (Ehrenb.) Grun., Navicula tenelloides Hust., Nitzschia amphibia Grun., Nitzschia inconspicua Grun., Nitzschia invisitata Hust., Nitzschia frustulum (Kütz.) Grun., Nitzschia sigma (Kütz.) W, Smith., Pinnularia chapmaniana Fog., Pinnularia appendiculata (Ag.) Cl., Pinnularia molaris (Grun.) Cl., Pinnularia acoricola Hust., Rhopalodia gibberula (Ehrenb.) O. Müll., Staurosira construens v. venter (Ehrenb.) Ham., Staurosira elliptica (Schum.) Will. & Round, and Staurosirella pinnata (Ehrenb.) Will. & Round. Canonical correspondence analysis shows clear correlations between species, alkalinity, pH, and conductivity, with less strong correlations for silica and temperature. Other factors include substrate type, current velocity, and light conditions. The preservation potential of host deposits varies considerably, being lowest for springs on clastic deltas and highest where travertine or sinter is accumulating. Handling editor: J. Padisak     

Influence of light quality and gassing on the vertical migration of diatoms inhabiting the Wadden Sea

Diatoms inhabiting the Wadden Sea show a rhythmic migration pattern, which is superimposed by the tidal rhythm. In addition to light intensity, light quality has a pronounced influence on the upward-directed migration, thus giving some information on the nature of the relevant photoreceptors. Maximum diatom migration occurred when sediment surfaces were illuminated with blue light. The cell densities in blue light exceeded those of white light control experiments 1.8-fold. Furthermore, we registered a minor peak in the red light region, which reached approximately 60% of the white light controls. Cryptochrome and/or phototropin may thus be involved and act as photoreceptors for the vertical migration pattern. Flushing sediment surfaces of freshly mixed Wadden Sea sediments with air, O₂, CO₂ or N₂ did not show a significant influence of O₂ on the upward migration. The disappearance of diatoms from sediment surfaces which were flushed with CO₂ is most probably caused by the acidification of the sediment bed.Communicated by E. Rachor     

SEM and stereoscope microscope observations on the seeds of some Ornithogalum (Hyacinthaceae) species

The paper presents the results of the study on seed morphology of four following Ornithogalum species: O. boucheanum Asch., O. nutans L., O. pyrenaicum L., and O. umbellatum L. Several macro-and micro-morphological characters were observed using stereoscope and scanning electron microscope. Differences were found especially in micromorphological characters of the seed surface, the shape of raphe and micropylar pole. These characters can be used as an additional taxonomic criterion at specific level for this genus. Only the seeds of O. boucheanum and O. nutans — two closely related and morphologically very similar species are practically undistinguished.