THE SEASONAL DISTRIBUTION,ABUNDANCE AND DIVERSITY OF DESMIDS (CHLOROPHYTA) IN A SOFTWATER,NORTH TEMPERATE STREAM1

Suspended and benthic algal communities from a mildly acidic, third-order Rhode Island stream were examined to determine the seasonal distribution, abundance and diversity of the lotic desmids. Within a one-year sampling period, 148 species and 202 subspecific taxa of desmids were identified, representing 23 genera. Species of Cosmarium and Closterium accounted for approximately 70% of the desmids present, and were the most diverse and abundant taxa during all seasons except spring, when Hyalotheca dissiliens was the dominant desmid species. Average abundance and species richness generally were greatest during summer for both suspended and benthic desmids. Most desmids occurred in benthic habitats, and were randomly distributed among substrata. Average seasonal abundance was 7.4 × 10⁴ cells·g^?1 dry wt substratum, among 13 types of substrata. Highest desmid abundance was measured among substrata with intricate morphologies, such as Fontinalis spp., which was associated with 1.2 × 10⁶ desmid cells·g^?1 dry wt substratum, or 1.7 × 10³ cells·cm^?2 substratum. Cell division was observed for 70 desmid taxa, and average seasonal reproduction (based on cell numbers) among all substrata ranged from 4% in winter to 20% during summer. In addition, sexually produced zygospores were found occasionally for H. dissiliens. Desmids were distributed among most substrata examined in this stream, with abundance comparable to reported estimates from softwater lakes and acid bogs. In contrast to established dogma, lotic desmids are not incidental drift organisms, but rather comprise a viable and persistent component of the stream periphyton.     

DESMID-BACTERIAL ASSOCIATIONS IN SPHAGNUM-DOMINATED WISCONSIN PEATLANDS1

In a survey employing epifluorescence microscopy with the DNA fluorochrome DAPI, associations between bacteria and filamentous desmids were found to be commonplace in acidic, Sphagnum-dominated Wisconsin peat-lands. Bacteria were associated with all genera of filamentous desmids encountered including Desmidium, Hyalotheca, Onychonema, Spondylosium, and Teilingia. Although only associations involving filamentous desmids having mucilaginous sheaths are illustrated here, bacteria were also noted on taxa lacking sheaths as well as some unicellular forms. Bacteria on Desmidium majus Lagerheim, D. grevillii (Kütz.) De Bary, and Hyalotheca dissiliens (Smith) Bréb. ex Ralfs tended to be concentrated in small pockets in the sheath material located near the isthmus and in the region between adjacent cells in the filament, whereas those associated with Spondylosium pulchrum (Bail.) Archer were more evenly distributed throughout the sheath. Most bacteria were rodshaped. Those associated with S. pulchrum, D. grevillii, and D. majus ranged from 1.1 to 11.2 μm in length. Bacteria within the sheaths of H. dissiliens and D. grevillii were Gram-negative. A second morphologically distinct population of bacteria was found at the sheath margin in D. majus and D. grevillii. Field collections containing filamentous desmids were examined with scanning electron microscopy and bacteria associated with Desmidium majus were investigated with transmission electron microscopy.     

PHYLOGENY OF THE CONJUGATING GREEN ALGAE (ZYGNEMOPHYCEAE) BASED ON rbc L SEQUENCES

Sequences of the gene encoding the large subunit of RUBISCO (rbcL) for 30 genera in the six currently recognized families of conjugating green algae (Desmidiaceae, Gonatozygaceae, Mesotaeniaceae, Peniaceae, and Zygnemataceae) were analyzed using maximum parsimony and maximum likelihood; bootstrap replications were performed as a measure of support for clades. Other Charophyceae sensu Mattox and Stewart and representative land plants were used as outgroups. All analyses supported the monophyly of the conjugating green algae. The Desmidiales, or placoderm desmids, constitute a monophyletic group, with moderate to strong support for the four component families of this assemblage (Closteriaceae, Desmidiaceae, Gonatozygaceae, and Peniaceae). The analyses showed that the two families of Zygnematales (Mesotaeniaceae, Zygnemataceae), which have plesiomorphic, unornamented and unsegmented cell walls, are not monophyletic. However, combined taxa of these two traditional families may constitute a monophyletic group. Partitioning the data by codon position revealed no significant differences across all positions or between partitions of positions one and two versus position three. The trees resulting from parsimony analyses using first plus second positions versus third position differed only in topology of branches with poor bootstrap support. The tree derived from third positions only was more resolved than the tree derived from first and second positions. The rbcL‐based phylogeny is largely congruent with published analyses of small subunit rDNA sequences for the Zygnematales. The molecular data do not support hypotheses of monophyly for groups of extant unicellular and filamentous or colonial desmid genera exhibiting a common cell shape. A trend is evident from simple omniradiate cell shapes to taxa with lobed cell and plastid shapes, which supports the hypothesis that chloroplast shape evolved generally from simple to complex. The data imply that multicellular placoderm desmids are monophyletic. Several anomalous placements of genera were found, including the saccoderm desmid Roya in the Gonatozygaceae and the zygnematacean Entransia in the Coleochaetales. The former is strongly supported, although the latter is not, and Entransia's phylogenetic position warrants further study.     

Some new and interesting ecological observations on desmids from the Province of Vojvodina (Northern Serbia)

A detailed qualitative investigation of the desmid community in the territory of the Province of Vojvodina (Northern Serbia, part of the Pannonian Plain) revealed a surprisingly high number of desmid taxa. Although most of the desmids were marked as rare, according to the results of physico-chemical analyses of water samples, several taxa were frequently recorded in habitats that are generally deemed unsuitable for desmids. The ecological characteristics of 18 desmid taxa, some of which known as acidophilic and/or oligotrophic, are briefly discussed. The unexpected presence of many desmid taxa is explained by assuming that their tolerance threshold to various physico-chemical parameters has changed considerably. Presented at the International Symposium Biology and Taxonomy of Green Algae V, Smolenice, June 26–29, 2007, Slovakia.     

Diversity and geographic distribution of desmids and other coccoid green algae

Taxonomic diversity of desmids and other coccoid green algae is discussed in relation to different species concepts. For want of unambiguous criteria about species delimitation, no reliable estimations of global species richness can be given. Application of the biological species concept is seriously hampered by lack of sexual reproduction in many species. Molecular analyses demonstrated cases of close affiliation between morphologically highly different taxa and, contrary, examples of little relationship between morphologically similar taxa. Despite the fact that desmids and chlorococcal algae, because of their microbial nature, can be readily distributed, cosmopolitan species are relatively scarce. The geographic distribution of some well-recognizable morphospecies is discussed in detail. Of some species a recent extension of their area could be established, e.g., in the desmids Micrasterias americana and Euastrum germanicum, and in the chlorococcaleans Desmodesmus perforatus and Pediastrum simplex. Special Issue: Protist diversity and geographic distribution. Guest editor: W. Foissner.     

Desmids of Iraq

Forty species and varieties of desmids belonging to the genera Closterium (7), Pleurotaenium (1), Euastrum (3), Cosmarium (28) and Staurastrum (1) have been described from southern Iraq including two new varieties under Cosmarium (i.e. C. cyclicum Lund, var. mesopotamianum var. nov., and C. tyrolicum (Nordst.) Krieger & Gerloff var. minor var. nov.). Most of the taxa are new records for Iraq.     

Application of desmid diversity in assessing the water quality of 12 freshwater resources in Thailand

Desmids from 12 freshwater resources in the northern part of Thailand were investigated during 2002 to 2003. A total of 91 taxa were found. They belonged to 17 genera: Actinotaenium, Spirotaenia, Netrium, Gonatozygon, Pleurotaenium, Closterium, Euastrum, Micrasterias, Cosmarium, Cosmocladium, Stuarastrum, Staurodesmus, Xanthidium, Teilingia, Spondylosium, Hyalotheca and Desmidium. The water qualities in all the water resources were classified as oligotrophic to meso-eutrophic by trophic status. The taxa that could possibly be used as bioindicators of trophic state were Staurastrum gutwinskii, Spondylosium pandurifoemae, Cosmarium capitulum, C. mediosrobiculatum var. egranutum, S. tortum, Closterium gracile var. elongatum, C. kuetzingii and Closterium dianae var. dianae. The most frequently found taxa were Staurastrum limneticum var. burmense, S. tetracerum var. tetraerum, Pleurotaenium trabecula, Closterium ehrenbergii var. ehrenbergii and C. kuetzingii. The rare taxa in this study were Actinotaenium sp. Spirotaenia condensata, Pleurotaenium burmense var. dacchense and Micrasterias apiculata. Forty-one taxa of desmids were identified as new records for Thailand. Presented at the 6th Meeting of the Asian Pacific Society of Applied Phycology, Manila, Philippines.     

Mesocosm studies on the influence of phosphate enrichment on ammonium and nitrate flux in an oligotrophic lake

The fate of ¹⁵NH _inf4 ^sup+ and ¹⁵NOinf3⁻ was followed in control and PO _inf4 ^sup3− enriched 1570 l mesocosms filled with epilimnetic water from an oligotrophic Rocky Mountain lake. Volumetric incorporation of ¹⁵NH _inf4 ^sup+ and ¹⁵NO _inf3 ^sup− into phytoplankton and bacterioplankton (particulates between 280 and 0.7 μm), and crustacean zooplankton > 80 μm was enhanced by PO _inf4 ^sup3− , but no increase in biomass specific rates of uptake by phytoplankton and bacteria occurred for either form of ¹⁵N. Dilution of both ¹⁵NH _inf4 ^sup+ and ¹⁵NO _inf3 ^sup− by ¹⁴NH _inf4 ^sup+ and ¹⁴NO _inf3 ^sup− , respectively, was evident indicating regeneration of these nutrients, but regeneration rates were not effected by PO _inf4 ^sup3− enrichment. The results illustrate the strong trophic coupling between N dynamics and PO _inf4 ^sup3− enrichment in this system.     

Cypsela micromorphology and anatomy in Cirsium sect. Epitrachys (Asteraceae,Carduoideae) and its taxonomic implications

Cirsium Miller, one of the largest genera of the Asteraceae (Carduoideae), contains more than 250 taxa. Turkey is one of its diversity centers and according to recent studies this genus is represented by 80 taxa. In the present study, cypsela morphologies, micromorphologies and anatomical structures of 17 C. sect. Epitrachys taxa distributed in Turkey are characterized in detail by using stereomicroscope, light microscope (LM) and scanning electron microscope (SEM). Cypselas are found to be obovate to narrowly oblong, or rarely oblanceolate. Based on SEM characters, six cypselas surface ornamentation types are identified, pericarp anatomical structures are described, as well as the structure of the testa. Crystal formations were observed in three taxa and secretory materials in the mesocarp were evaluated. Data obtained from this study are compared with previously published results and it is concluded that fruit micromorphological and anatomical characters are useful for the delimitation of taxa in Cirsium and may be useful for supraspecific classification.     

CHROMOSOME COUNTS OF COMPOSITAE FROM THE UNITED STATES AND MEXICO

Chromosome counts are reported for 126 taxa representing 122 species and 61 genera of Compositae. First reports include two genera, Stylocline (n = 14) and Chromolepis (n = 19), 17 species, two infraspecific taxa, and one interspecific hybrid. Five additional taxa have chromosome numbers differing from previously published accounts. Carminatia is reinstated to generic status.     

Desmids in mountain lakes of the subpolar Urals

The species composition of desmids was studied in eight mountain lakes of the Kozhim and Malyi Patok River basins in the “Yugyd Va” National Park (subpolar Urals, Russia). A total of 98 desmid taxa representing 13 genera belonging to 4 families were identified. Geographical and ecological analyses showed that the desmid flora is typical, with a predominance of cosmopolitan species, planktic-benthic forms, acidophilic and pH indifferent species, and halophobic to salinity indifferent species. The investigated lakes can be classified as pristine and in good ecological condition on the basis of their hydrochemical and algal biodiversity characteristics. Presented at the International Symposium Biology and Taxonomy of Green Algae V, Smolenice, June 26–29, 2007, Slovakia.     

Desmids from ephemeral pools and aerophytic habitats from the Czech Republic

The distribution and ecology of desmids in wetland habitats in the Czech Republic were studied during 2003–2007. Samples were taken also from various aerophytic habitats and temporary pools thet had not been sufficiently studied before. Altogether 110 desmids taxa were found in 31 samples which were ordinated on the basis of their desmid species composition using a multivariate statistic method. The discussion focuses on the most interesting findings and on the factors that influence the distribution of desmids in different types of aerophytic habitats. Presented at the International Symposium Biology and Taxonomy of Green Algae V, Smolenice, June 26–29, 2007, Slovakia.     

Contributions to the Cladocera fauna from Papua New Guinea

Twenty-eight taxa of the Cladocera are identified in collections from Papua New Guinea, 17 being new records for New Guinea, bringing the total number of Cladocera taxa reported for this region to 39. Most of the taxa are circumtropical. One species (Sarsilatona papuana) is endemic to Papua New Guinea and northern Australia. The species list includes two species that are normally listed as Holarctic:Alonella nana andAlona rustica. Widespread genera such asDaphnia, Pleuroxus, Disparalona, Acroperus were strikingly absent from the Papua New Guinean material.     

OBSERVATIONS SUR LES BESOINS EN VITAMINES DES DESMIDIÉES (CHLOROPHYCÉES-ZYGNEMATALES)1

The minimal nutrient requirements of 61 strains of desmids belonging to 18 different genera were investigated within 16 axenic cultures and 45 contaminated cultures. Thirty-nine strains were autotrophic: they included all 30 strains belonging to the genera Cosmarium, Staurastrum, and Micrasterias. Twenty-two strains were auxotrophic; they included all 14 strains belonging to the genus Closterium. Of the 22 auxotrophic strains, 13 required only vitamin B₁₂; the specific requirements of the other 9 strains were not determined.     

Desmids of Bangladesh

214 taxa under 21 genera of desmids have been described and illustrated from Bangladesh, of which 3 species and 8 varieties are new to science.     

Physical and chemical effects of macrograzers and micrograzers on enclosed,in situ phytoplankton in a Newfoundland lake

Grazing effects were evaluated by comparisons between phytoplankton populations in the lake water and in bicompartmental chambers, deployedin situ in a Newfoundland lake. Micrograzing effects were evaluated separately from both the physical effects of macrograzers and the chemical effects of macrograzer metabolites on phytoplankton assemblages in bicompartmental chambers. Macrograzer metabolites were able to pass through fine gauze between the compartments. Thus, the chemical effects of the macrograzers were observed in one compartment while the physical effects were the dominant treatment in the other. Micrograzer effects were investigated in chambers without added macrograzers.Densities of some of the desmid species were depressed by the physical effects of macrograzers. This is the first ecological study to demonstrate such a grazing effect on desmids. Some individual taxa, such asArthrodesmus triangularis var.rotundatus (Raciborski)comb. nov., andMesotaenium sp. Nägeli (Zygnemaphyceae), were augmented under the chemical effects of macrograzer metabolites. Evidence suggests that the desmids were not micrograzed. Grazing effects on desmids have not previously been studied in waters in which they were abundant.The Chlorophyceae, which were small species in Hogan's pond, and the microflagellates generally maintained their overall population densities in spite of the presence of macrograzers, however, abundances of some individual species within the assemblages changed in the presence of macrograzers. Micrograzers may also affect the species composition and abundance of the individual chlorophycean taxa.With the exceptions ofSynedra sp. Ehrenberg andTabellaria fenestrata var.lacustris Meister the diatoms were unaffected by the grazers. The Chrysophyceae were little affected by micrograzing and physical effects of macrograzers, in contrast to chemical effects of macrograzer metabolites that were evident for individual species.Several of the Cyanobacteria (Cyanophyceae) were augmented in the presence of micrograzers. Evidence indicates that they were not micrograzed. Some individual species, e.g.,Microcystis aeruginosa Kützing, were augmented by both physical and chemical effects of macrograzers.     

Mediterranean karst springs: diatom biodiversity hotspots under the pressure of hydrological fluctuation and nutrient enrichment

Abstract

Mediterranean karst springs are affected by strong climatic seasonality, with long, dry and hot summers and are increasingly threatened by anthropogenic pressures. In Sardinia (western Mediterranean Sea, Italy), they are largely unexplored and their biocoenoses are mostly unknown. The diatom flora from two substrates (cobbles and macrophytes) in eight springs of different areas of the island was investigated in summer 2016 and winter 2017. A total of 162 diatom taxa (58 genera) were found of which 27 (17 genera) only on cobbles and 26 (18 genera) only on macrophytes. The most abundant species from both substrates were Achnanthidium minutissimum, Amphora indistincta, Amphora pediculus, Cocconeis euglypta, Planothidium frequentissimum and P. lanceolatum. Overall, 67 taxa (40 genera) were recorded in single sites and some of these taxa showed high affinity with specific environmental conditions. Hydrological stability (water flow permanence), discharge and nutrients were the main environmental factors influencing diatom assemblages. Our results suggest that diatoms can reflect important local factors related to the vulnerability of these spring ecosystems and underline the importance of their preservation both for biodiversity and water quality maintenance.     

Seasonal periodicity of planktonic desmids in oligotrophic lake Grane Langsø, Denmark

60 desmids were identified from plankton samples collected during 20 years, bimonthly, or monthly in 5 of the years. Only 5 desmids were perennial, performing cell divisions in a frozen lake at PAR at only 5 cal cm ^–2 day ^–1, below ice-cover. The greatest number of desmids per 100 ml lake water was found in September; it never exceeded 150. Owing to a concentration of free CO₂ of only 0.02 mM l^–1 and a HCO _inf3 ^sup– concentration of 0.002 mM l^–1 the densities of desmid cells were often smaller than 1 cell per 100 ml lake water. A density of 1 cell per 1 ml was attained only by Staurastrum longipes, a desmid showing temporal variation. The relation of the compound phytoplankton quotient to two components of the CO₂-system is discussed. Three new taxa are described: Staurastrum brachiatum Ralfs var. bicorne n. var., Staurastrum thomassonii n.sp. and Xanthidium antilopaeum Kütz. f. bimaculatum n.f..     

Cladistic analysis of morphological characters in the eulophine tribe Cirrospilini (Hymenoptera: Eulophidae)

A total of 56 morphological characters were analyzed for 53 cirrospiline species that represent all of the 17 described genera of the tribe. The other taxa of the Eulophinae included in the analysis were six species of six representative genera in the tribe Eulophini, a species of Elasmus (the only genus comprising the tribe Elasmini), and a species of Trichospilus (unplaced). Trichospilus and two of the six genera of Eulophini examined were placed within Cirrospilini. Monophyly of Cirrospilini (when these two genera of Eulophini and Trichospilus are included) and of the cirrospiline genera for which more than one species were examined was supported, but the relationships between the genera were poorly resolved. An exception was Cirrospilus, the largest genus in the Cirrospilini, monophyly of which was not supported to any extent.