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Gayana. Botánica
Print version ISSN 0016-5301On-line version ISSN 0717-6643
Gayana Bot. vol.62 no.1 Concepción 2005
http://dx.doi.org/10.4067/S0717-66432005000100002
| Gayana Bot. 62(1): 1-8, 2005 SILICA-SCALED CHRYSOPHYTES FROM ECUADOR
CRISOFITAS ESCAMOSAS DE ECUADOR
Daniel E. Wujek & Ryan M. Dziedzic
Department of Biology, Central Michigan University, Mount Pleasant, MI 48859 USA ABSTRACT Thirty silica-scaled chrysophytes, from 60 Ecuadorian water bodies, were observed using transmission and scanning electron microscopy. The taxa comprised 27 Synurophyceae (19 Mallomonas spp., 7 Synura spp., and one Chrysodidymus species) and three Chrysophyceae (two species of Paraphysomonas and one species of Spiniferomonas). All are new reports for Ecuador, and one taxon (Mallomonas lychenensis f. ecuadorensis) is described as new. The number of taxa per sample varied from none to ten. Keywords: Chrysophyceae, South America, Synuraceae. RESUMEN Treinta crisófitas escamosas, obtenidos de 60 cuerpos de agua en Ecuador, fueron observados mediante microscopía electrónica. Los taxones comprenden 27 Synuraceae (19 Mallomonas spp., siete Synura spp., y una especie de Chrysodidymus) y tres Chrysophyceae (dos Paraphysomonas spp. y una especie de Spiniferomonas). Todas son nuevos informes para Ecuador y un taxon (Mallomonas lychenensis f. ecuadorensis) se describe como nuevo. El número de taxones por muestra varió de ninguno a diez. Palabras clave: América del Sur, Chrysophyceae, Synuraceae.
INTRODUCTION The Chrysophyceae and Synurophyceae, characterized by an exogenous siliceous envelope composed of scales and/or bristles have long been recognized as important indicators of environmental conditions. These silica-scaled chrysophytes are second in importance only after diatoms as indicators of the past ecology of lacustrine environments (Smol 1995; Stoermer 1999). For example, the effects of acid rain were demonstrated by examining present and past sediments for scaled chrysophytes to demonstrate changes in the environment over time (Smol 1995). Identifications of scaled chrysophytes are based upon the morphology of scales that often are preserved in sediments. Identifications based on light microscopy are of limited value as electron microscopy (EM) is usually necessary to distinguish sufficient morphology for species identification in the two groups (Kristiansen 1979). Information is now becoming available on the ecology and distribution of Central and South American silica-scaled chrysophytes. An extensive literature based on EM has accumulated from several Latin American countries, especially Argentina (Vigna & Kristiansen 2002), Brazil (Franceschini & Kristiansen 2004), Chile (Dürrschmidt (1980, 1981, 1982a, 1982b, 1983a, 1983b, 1983c), and Costa Rica (Wujek 1984; Wujek et al. 1998). Reports from Mexico (Kristiansen & Tong 1995), Colombia (Vigna & Escobar 1999) and Belize (Carty & Wujek 2003) have also been published. his study presents an account of scale-bearing chrysophytes (Chrysophyceae and Synurophyceae) from the equatorial area of Ecuador using scanning (SEM) and transmission electron microscopy (TEM). Correlations of these organisms with ecological conditions are discussed briefly.
MATERIALS AND METHODS Sixty different sites from Ecuador were sampled (Table I). Most sites were located using a global positioning system. Plankton net samples were taken with 10 or 20 µm mesh nets. Samples were preserved with acid Lugol's solution (Gifford 1991) in plastic screw-cap vials. Collecting sites included rivers, ponds, lakes, temporarily flooded fields, and ephemeral ponds. Samples for TEM were subsampled onto Formvar-coated, carbon stabilized, 3 mm copper grids. After air drying, they were examined with a JEOL CM-10 TEM. Samples for scanning electron microscopy were prepared as described previously (Wujek & Elsner 1992).
RESULTS Thirty taxa representing five genera were observed in the 60 samples (Table II). Taxa, including one new form of Mallomonas, are all new reports for Ecuador (Figs. 1-31). The taxon list includes 19 Mallomonas taxa, seven Synura taxa, including two forms of S. petersenii, two Paraphysomonas taxa, and one taxon each of Chrysodidymus and Spiniferomonas. The number of scale-bearing chrysophyte taxa observed per sample varied from none to ten (Table I). The most frequently observed species was Paraphysomonas vestita (Stokes) de Saedeleer (16% of samples). This was followed by three taxa in the genus Synura: S. echinulata Korshikov (12%), S. petersenii Korshikov f. petersenii (7%) and S. spinosa Korshikov (5%). Common species frequently observed from Mallomonas were M. matvienkoae var. matvienkoae (8%), and three taxa each at 5%, M. mangofera f. foveata Dürrschmidt, M. papillosa Harris & Bradley, and M. striata var. serrata Harris & Bradley. Mallomonas akrokomos Rutter, M. fenestrata Cronberg & Hickel, M. lychenensis Conrad, M. lychenensis f. ecuadorensis Wujek & Dziedzic, M. parvula Dürrschmidt and M. pillula f. valdiviana Dürrschmidt, and Synura uvella Ehrenberg em. Korshikov were only observed once. A pond with large quantities of horse dung (sample 46) had the highest diversity (10 taxa). A small marsh (sample 45) and a shallow tributary of Lake Zancudo Cocha (sample M3), whose surface was covered by a "scum" were second with seven. Over half of the sites had four or fewer species each. One new form of Mallomonas lychenensis, M. lychenensis f. ecuadorensis, was observed (Fig. 9). The epithet "ecuadorensis" refers to the type locality. Mallomonas lychenensis Conrad f. ecuadorensis Wujek et Dziedzic f. nov. Latin diagnosis: Differt a f. lychenensis fasci scuti. Scutum 6-8 magnis lacunis irregulariter distributis. Scutum squamae areis papillarum dense obtectum. Squamae 3-3.5 x 5-6 mm. Lacunae magnae (0.5-1.2 mm diametro) scutarum quasi quadrangulares tres aut quatuor seriebus duabus distributae. Nec setae nec cystae observatae. Typus: Die 12 junii, anno 2001 in stagnum gramineum (02º46.58'S, 79º13.93'W), Ecuador. Figuris 9 monstratus, in collectione Universitatis Michiganensis Centralis, Mount Pleasant, Michigan. Holotypus: Fig. 9. Description: This species differs from M. lychenensis f. lychenensis in the appearance of 6-8 large, irregularly arranged pits in the shield. The shield of scales is covered with well developed patches of closely spaced papillae (Fig. 9). The scales are 3-3.5 x 5-6 µm. Large pits (0.5-1.2 µm diameter) occur in two rows, three to four pits in each row. Bristles and cysts not observed. Type locality: Pool with grass (02º46.58'S, 79º13.93'W), Ecuador, South America, 12 June 2001; deposited in the Central Michigan University Herbarium (CMC). Type figure: Fig. 9. The unique size of the large pores in the shield separates this taxon from other forms. While the papillate shield area is structurally similar to M. lychenensis our taxon possess the very large double row of pits terminating with a large pit at the proximal end. Such a pit is lacking in f. lychenensis. It also resembles M. lychenensis f. symposiaca Skogstad & Kristiansen, but lacks the elongated and often irregular-shaped depressions or channels along the shield.
DISCUSSION The scaled chrysophyte flora of Ecuador is similar to that reported for other parts of South and Central America. The species found are distributed in temperate and tropical regions (Cronberg 1989, 1996; Hansen 1996). Most surprising was the low occurrence of Synura uvella, a ubiquitous species which was observed in only one of our samples (Table II). Mallomonas lanalhuensis (Fig. 7) is reported for only the second time since its original description from Chile (Dürrschmidt 1983a). Similarly, the occurrence of Mallomonas fenestrata (Fig. 4) from a small marsh represents the fourth report of a species to date found only in South America (Cronberg & Hickel 1985; Cronberg 1989; Kristiansen & Menezes 1998). Some of the other taxa that we observed were originally described from South and Central America, but have since been shown to be cosmopolitan. Examples include Mallomonas cristata, M. guttata, M. multisetigera, M. parvula and M. pillula f. valdiviana. The number of species in each sample was relatively low. The total is considerably less than might have been expected considering that, with only two exceptions, all of the samples came from sites where pH was less than 7.0 (Table I). This is surprising, because acidic conditions have been shown to be optimal for scaled chrysophyte growth (Roijackers & Kessels 1986; Siver 1988, 1989, 1991). Although water temperatures were not taken at time of sampling, the species observed tolerate wide ranges and are therefore considered as eurythermal (Takahashi 1978). Future South American studies should include this ecological parameter. Roijackers and Kessels (1986) have demonstrated in temperate waters the abundance of a particular species is mostly controlled by water temperature. In subtropical and tropical areas, Saha and Wujek (1990) and Wujek and Saha (1996) have suggested that where average air or water temperatures are at 20°C continuously, these temperatures could affect development and diversity of scaled chrysophyte populations. This paper raises the known silica-scaled chrysophyte flora of Ecuador to a total of 30 taxa. This is far fewer than the numbers observed from Argentina (58), Brazil (52) and Chile (40). However these three countries have had their scaled chrysophyte flora studied more extensively. It is hoped our study will stimulate further Ecuadorian studies. Collections and observations representing other seasons and/or other Ecuadorian geographic regions and habitat types will undoubtedly yield additional species. Some types of habitat have yet to be thoroughly studied worldwide, including in Ecuador. Kristiansen (1986) has stated that one such habitat type in need of research is high altitude lakes in tropical mountains. This is supported by Cronberg (1989) who states "that many more species belonging to this algal group will be found if systematic investigations of the tropics at different seasons of the year and over several years are undertaken".
Figures 19-31. Mallomonas striata var. serrata, body scale. Figs. 20-26. Synura. 20. S. curtispina, body scale. 21. S. echinulata, body scale. 22. S. petersenii f. petersenii, body scale. 23. S. petersenii f. kufferathii, body scale. 24. S. sphagnicola, body scale. 25. S. spinosa, body scale. 26. S. uvella, body scale. Fig. 27. Chrysodidymus synuroideus, body scale. Figs. 28-29. Paraphysomonas. 28. P. vestita, body scales. 29. P. imperforata, body scale. Figs. 30-31. Spiniferomonas trioralis. 30. Spine scale. 31. Plate scales. Scale bar = 1 mm. Table II. Taxa observed in the Ecuador collections. See Table I for locations.
ACKNOWLEDGMENTS We thank Drs. Susan Carty and Miriam Kennan for the samples, Dr. Jørgen Kristiansen for examining several of our micrographs, Geoffrey Williams for the preparation of the carbon-stabilized grids, and G. Williams and Amanda Weber with the figures. This study was supported by a CMU FRCE Award.
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