Gustavo Montejano

First report on the occurrence of microcystins in planktonic cyanobacteria from Central Mexico.

Although toxic cyanobacteria are commonly described worldwide, only one recent paper on the toxicity of cyanobacteria in Mexico has been published reporting the occurrence of cylindrospermopsin and saxitoxins. Microcystins are the most commonly studied cyanotoxins in many countries and those that may cause the most dramatic problems in terms of human health. In this paper, we studied the occurrence of potentially toxic cyanobacteria in different ecosystems in Central Mexico. Samples were collected in natural lakes (Zumpango, Laguna Atotonilco and Cienega Chica), reservoirs (Los Angeles and Valle de Bravo), man-made channels (Cuemanco, Tlameleca) and urban lakes (Chapultepec). A multi-technique approach was applied by the use of molecular, immunological and chemical techniques. Cyanobacteria were found in all the sites, ranging from 1.6 x 10(3) cells/mL in Tlameleca to 7.5 x 10(6) cells/mL in Chapultepec Grande, representing between 67 and 100% of the total phytoplankton density. The concentration of total microcystins varied between 4.9 and 78.0 microg MC-LR eq/L. The results revealed the occurrence of MC-LR in all the sites analyzed by MALDI-TOF, and MC-FR, MC-RR and MC-H(4)YR in two sites. Most of the studied sites are used either as a source of drinking water, as a recreational area, or for agriculture irrigation purposes, so the risk for human health may be high if not properly monitored. This is the first report on the MC profiles and concentrations in blooms collected in Mexico.

Cyanobacteria in ambient springs

Although neglected for a long time by freshwater-ecology research, springs are very important habitats for biodiversity conservation. They are multiple ecotones, and are characterized by a remarkable variety of environmental conditions (e.g., from highly-shaded to UV exposed, from permanent discharge to intermittent flow, from still water to strong currents, from extremely-soft to carbonate-precipitating water, etc.). Moreover, springs are often amongst the last high-integrity, oligotrophic freshwater habitats in densely populated areas. Because of the high quality of their waters, the main impact affecting springs is capturing and water diversion. Climate-change driven reduction in precipitations in many areas is likely to determine an aggravation of this impact. It is thus important to document the rich and peculiar biodiversity of springs, also to establish reference conditions for bioassessment methods. Especially in non-acidic springs with running water, and coarse lithic substrata, cyanobacteria are often one of the most taxa-rich and abundant groups of photoautotrophs. The relatively-scarce information available in the literature is mostly referred to similar habitats, and not to spring habitats in the narrower sense. Papers dealing with the cyanobacteria of ambient springheads (=eucrenal) worldwide are still very rare. These were reviewed separating ambient springs in temperate and warm climate, and with special attention to key species, to cyanobacterial strategies allowing survival in oligotrophic headwaters (e.g., nitrogen fixation, phosphatases, anti-UV compounds, etc.), and to distribution patterns. The review also hopes to bolster new interest and research on this topic, and suggests some promising research directions.

Freshwater Epiphytic Cyanoprokaryotes from Central Mexico: II. Heterogeneity of the Genus Xenococcus

Summary: Second article of the series of studies about the cyanoprokaryotic (cyanophycean, cyanobacterial) species, growing epiphytically on submersed filamentous algae in central Mexico. The traditional genus Xenococcus was found to be heterogeneous and the stability and frequency of inter- and intrageneric characters was studied in natural populations from central Mexican streaming waters, sampled in the period from 1983 to 1993. The types of cellular binary,fission and nanocytic cell division were particularly studied, and from them were derived different life-cycle strategies. The genus Xenothotos gen.n. was separated from the genus Xenococcus on the basis of these results, and seven species were studied from both genera (one new species of Xenococcus and three new species of Xenotholos were described). Characteristics of all species studied are included. Another group of traditional Xenococcus -species, which does not correspond morphologically either to Xenococcus or to Xenotnotos , and cells of which never divide by multiple fission, must be also separated from the genus Xenococcus ( X. minimus type).

Ecology and morphological characterization of gametophyte and 'Chantransia' stages of Sirodotia huillensis (Batrachospermales, Rhodophyta) from a stream in central Mexico

The morphology and phenology of Sirodotia huillensis was evaluated seasonally in a central Mexican first‐order calcareous stream. Water temperature was constant (24–25°C) and pH circumneutral to alkaline (6.7–7.9), and calcium and sulfates were the dominant ions. The gametophyte stages were characterized by the presence of a distinctive mucilaginous layer, a marked difference in phycocyanin to phycoerythrin ratio between female and male plants, and the presence of a carpogonia with a large trichogyne (>60 µm). Occasionally three capogonia were observed on a single basal cell. The ‘Chantransia’ stages were morphologically similar to those described for the other members of Batrachospermales. A remarkable observation was the formation of dome‐shaped structures, consisting of prostrate filaments that are related with the development of new gametophytes. Chromosome numbers were n = 4 for fascicle cells, cortical filament cells and dome‐shaped cells, and 2n = 8 for gonimoblast filament cells and ‘Chantransia’ stage filaments. Gametophytes and ‘Chantransia’ stages occurred in fast current velocities (60–170 cm/s) and shaded (33.1–121 µmol photons/m2/s) stream segments. The population fluctuated throughout the study period in terms of percentage cover and frequency: the ‘Chantransia’ stages were most abundant in the rainy season, whereas gametophytic plants had the highest frequency values during the dry season. These results were most likely a result of fluctuations in rainfall and related changes in current velocity. Some characteristics of this population can be viewed as probable adaptations to high current velocities: the mucilaginous layer around plants that reduces drag; potential increase in fertilization by the elongate and plentiful trichogynes and abundant dome‐shaped structures producing several gametophytes.

Some little known Hydrococcaceae (Cyanoprokaryota) from Central Mexico

The little known genera of Hydrococcaceae Cyanodermatium, Placoma and Hydrococcus are well represented in the epilithic and epiphytic flora of central Mexico. A new marine species of Cyanodermatium, C. gonzaliensis, is established and three freshwater populations of the genera Hydrococcus, Cyanodermatium and Placoma, that represent new records for Mexico are studied. The morphological characteristics of the development of the thalli in several species of the three genera from populations from both marine and continental habitats are described. These genera differ among each other, in the pattern of cell division and growth that result in a characteristic organization of the pseudofilaments and therefore in the shape of the colonies. The proposal made by KOMAREK & ANAGNOSTIDIS (1998) to separate these genera that do not produce baeocytes from those included in the family Hyellaceae to which they are similar in their pseudofilamentous organisation is supported.

Freshwater Epiphytic Cyanoprocaryotes from Central Mexico: I. Cyanocystis and Xenococcus

Summary Three freshwater, epiphytic species of the cyanoprocaryotic (cyanophycean, cyanobacterial) genera Cyanocystis (C. mexicana spec. nova) and Xenococcus (X. willei GARDNER, X. bicudoi spec. nova), which occur commonly in streaming, unpolluted waters of central Mexico, were studied and documented. The generic diacritical features of Cyanocystis and Xenococcus are discussed.

The distribution of Rhodophyta in streams of Central Mexico

The distribution of species of Rhodophyta was investigated in 424 stream segments, sampled from 1981–1999 in three river basins from central Mexico. Red algae occurred in 12% of the stream segments sampled, a low frequency compared to major surveys in other parts of the world (18–65%). Sixteen species of freshwater red algae were found, of which the most widespread were Compsopogon coeruleus (24 sites) and Hildenbrandia angolensis (16 sites). Two groups of species were clearly distinguished on the basis of environmental characteristics. The first group, which included Batrachospermum gelatinosum, Paralemanea annulata, P. mexicana and Sirodotia suecica, is found in temperate climates, high altitudes (>1700 m), and cold or temperate waters (12–18°C) that are slightly acidic (pH 5.5–6.5) and of low specific conductivity (77–86 μS . cm–1). The second group, including Chroodactylon ornatum, Compsopogon coeruleus, Hildenbrandia angolensis, Audouinella eugenea, A. huastecana, A. meiospora, Batrachospermum globosporum, Sirodotia huillensis and Thorea hispida, is of subtropical to tropical climates, low altitudes ( 21°C) that are neutral to slightly alkaline (pH 7.0–8.6) and of high specific conductivity (160–1990 μS.cm–1). Half of the species found in this study were exclusively of calcareous sites from within a highly homogeneous limestone region (56% Ca). The rest of the sites with rhodophytes were found in sub-basins with andesitic-basaltic or calcareous substrates, and in temperate to semidesertic climates that provoke dramatic changes in the water level of the river or even the complete absence of permanent rivers. A high percentage of the currents contained an influx of organic material in which populations of Compsopogon coeruleus, described as tolerant of these conditions, could be found. The sub-basins that were most similar and had the least diversity corresponded to high mountain regions of Central Mexico (HP and HB). The overall species composition for streams and rivers of Central Mexico revealed high similarities with other tropical regions and had few species in common with freshwater red algal floras of other continents.

Are Cyanobacterial Mats Precursors of Stromatolites

Since James Hutton established the principle of uniformitarism in 1788, direct comparisons between ancient and present processes have been key elements in geological and paleontological observations. Lyell and Darwin successfully applied uniformitarism using reasoning and inference to obtain the missing data from incomplete evidence (Gould, 1983). This actualistic approach has also permeated the study of stromatolites and their living analogs, modern microbial mats. As early as 1908, Kalkowsky (1908), who coined the term stromatolites, recognized not only the organic nature of stromatolites, but also the participation of microbial life in their construction (Riding, 2008, and references therein), as he wrote: ‘stromatolites have a fine more or less even layered fabric.…and the participation of simple plants gave rise to limestone precipitation’ (translation from Prof. J. Paul, 2008). The structural similarity between algal mats and intertidal stromatolites was documented since the beginning of the twentieth century; Walcott (1914) even presumed the participation of cyanobacteria by then (Awramik and Grey, 2005). The early observations of Black (1933) also included the participation of cyanobacteria in the modern marine microbialites from the Bahamas. The precipitation of calcium carbonate, erosive boring, and binding of sediments were identified as main processes in these algal carbonates (Fritsch, 1945; Pettijohn, 1957; Sharp, 1970). Later Logan et al. (1964) proposed a popular general classification system to group the main morphologies found in ‘algal stromatolites’ when he analyzed recent stromatolites from Shark Bay in Australia.

Dermocarpella (Cyanoprokaryota / Cyanophyceae / Cyanobacteria) from the Pacific coast of Mexico

Abstract An account of the intricate history of the taxonomy and nomenclature of the genus Dermocarpella (Cyanobacteria / Cyanophyceae / Cyanoprokaryota) is provided. Detailed observations at the population level have allowed the detection of different stages of the life cycle of two species of this genus and have helped to solve some of the uncertainties in the validation of this genus. The species described are D. gardneri as a new name for Dermocarpa hemisphaerica Setchell et Gardner and Dermocarpella stellata sp. nov. An identification key and a comparative table of the diagnostic features of the species of the genus are included.

Taxonomy and life cycle of epiphytic Dermocarpellaceae and Xenococcaceae from central Mexico

In this paper we present a synthesis of several studies on the reproduction, life cyles and taxonomy of epiphytic baeocyte producing cyanoprokaryotes from central Mexico. We have found that thallus structure is closely related with the mechanism of reproduction (binary fission and/or multiple fission), planes of cell division during development and sheath consistency. We propose characteristics for distinguishing among species belonging to the genera. Xenococcus, Xenotholos, (Xenococcaceae), Cyanocystis, and Dermocarpella (Dermocarpellaceae).