A new species of Cuscuta (Convolvulaceae) from Michoacán, Mexico

A new species, Cuscuta cotijana, is described and illustrated from the Trans-Mexican Volcanic Belt in northwestern Michoacán, Mexico. The species is most closely related to Cuscuta jalapensis, C. mitriformis, C. rugosiceps and C. lindsayi, from which it differs by the large spur-like projections on the outer calyx lobes and the ovoid to conical capsule with a small intrastylar aperture.     

Detecting Karenia brevis blooms and algal resuspension in the western Gulf of Mexico with satellite ocean color imagery

Blooms of the toxic dinoflagellate, Karenia brevis, have had detrimental impacts on the coastal Gulf of Mexico for decades. Detection of Karenia brevis blooms uses an ecological approach based on anomalies derived from ocean color imagery. The same anomaly product used in Florida produces frequent false positives on the Texas coast. These failures occurred during wind-driven resuspension events. During these events resuspension of benthic algae significantly increases chlorophyll concentrations in the water, resulting in confusion with normal water column phytoplankton, such as Karenia. A method was developed to separate the resuspended chlorophyll from the water column chlorophyll, decreasing the false positives used with the detection method.     

The role of maternal cognitive ability on child health

Little is known about the mechanisms through which mother's cognitive ability operates in enhancing her children's health. This paper analyzes how maternal returns to cognitive ability on children's height reflect contemporaneous endowments and childhood background of the mother. Results suggest that maternal returns to cognitive ability on child height are less likely to reflect observed mother's childhood endowments as measured by parental transmission of knowledge or school quality, but are more likely to be associated with learning to be a mother, and with a better capacity to take advantage of household and community available resources.     

Observations on Some Species of Chaetoceros (Bacillariophyceae) with Reduced Number of Setae from a Tropical Coastal Lagoon

Species of Chaetoceros with less than four setae per cell are not common. In this study, five different taxa presenting this characteristic were found in the Sontecomapan lagoon, Mexico, a small tropical coastal lagoon on the Gulf of Mexico:Chaetoceros minimus, C. subtilis var. abnormis f. abnormis, C. subtilis var. abnormis f. simplex, C. throndsenii var. throndsenia, and C. thondsenii var. trisetosa. Using an electron microscope to make observations of C. subtilis var. abnormis f. simplex made evident the absence of rimoportulae suggesting a close relationship to C. minimus. According to our observations, we believe that the reduction in the number of setae in Chaetoceros is related to solitary forms. The five species studied here are associated with quiet brackish-water enclosed environments and can be considered worldwide-distributed organisms.     

Palaeoecological significance of Barremian ammonite assemblages and facies variations from Southwest Mexico

Analyses of ammonite shell forms of two Barremian stratigraphic sections from Southwest Mexico consist of two well-defined morphotypes: (1) Small uncoiled, mostly leptoceratoid ancyloconic shells of the families Ancyloceratidae and Hamulinidae, and (2) middle-sized involute to moderately evolute oxycone to discocone shells of the family Pulchelliidae. Index taxa allow the recognition of standard ammonite biozones for the Barremian, which permit the relative dating of different processes that occurred through the water column in the environment of deposition. The vertical distribution of ammonite morphotypes and facies suggests changes of the palaeoceanographic and sedimentological conditions that prevailed in the area during Barremian time. Petrologic data, analyses of the organic carbon and carbonate contents of the rocks support the idea that oxygen-deficient bottom waters existed within a shallow marine, tectonically active area with little carbonate deposition during the early early Barremian (upper part of the Taveraidiscus hugii Zone through the base of the Nicklesia pulchella Zone). These conditions in the basin caused a proliferation of middle-water depth ammonites of Morphotype 1 but prevented the abundance of nektobenthic forms of Morphotype 2. Oxic conditions on a more calcareous and open normal marine environment seem to have been reestablished progressively during a transgressive episode from late early-early late Barremian (upper part of the Nicklesia pulchella Zone through the Gerhardtia sartousiana Zone). This environmental setting supported more facies dependent nektobenthic ammonites of Morphotype 2 to flourish within the basin.     

Lake Patzcuaro (Mexico): a controversy about the ecosystem water regime approached by field references, climatic variables, and GIS

In this paper, a basic question is asked about a well-documented case study in Mexico: how well do we know Lake Patzcuaro? We address water balance as fundamental to the question. Past studies provide ambiguous explanations about the role of either underground infiltration and/or runoff, relative to the lake-level fluctuation. Thus, our suspicions over the database reliability led us to inspect historic records on water levels and climatic variables; check out the altitude of ground references, and analyze traces of runoff watercourses over the terrestrial basin by means of GIS. By making data re-arrangement and corrections, it became evident that the lake is subject to long-term cycles with ca. 40-year peaks, including short-term seasonal cycles within. Sensitivity to climatic conditions was determined, as well as the active influence of runoff as an important hydrologic component that contributes to cause serious damage to the land surface by erosion. Rearrangement of raw data highlights the occurrence of past misinterpretations founded on biased information.     

Chemical composition of the sponge Chondrosia reniformis from [2pt] the Canary Islands

Lake Zempoala was studied throughout 16 months in 1996–1997. It is a shallow monomictic lake situated at 2800 masl at the Neovolcanic Belt, well within the Mexican tropical zone. Most of the phytoplankton species in this lake may be characterized as temperate, according to their geographical distribution. A break down in phytoplankton biomass was observed before the lake's circulation, and open to question if a clear-water phase could be present in a tropical lake.     

Characterization of small shallow ponds with color video imagery in Central Mexico

We present a method to evaluate ecological characteristics of small shallow ponds in Central Mexico based on video remote sensing and image processing techniques in a GIS environment. We used a set of color video imagery obtained from heights lower than 700 m above ground. Our analysis established statistical correlations between the average reflectance values contained in video imagery (digital numbers DN per Blue-Green-Red band) and the average values of limnetic variables: (1) water suspended solids concentration; (2) water turbidity; (3) total macrophytes coverage; (4) free floaters and emergent macrophytes coverage; (5) zooplankton abundance; and (6) chlorophyll-a concentration in water. We found strong correlation between DN values and vegetation presence, suspended solids concentration and water turbidity (R= 0.85 to 0.98), but weak correlations with phytoplankton and zooplankton abundance. This cheap and fast method can be used to describe general conditions of ponds related with vegetation abundance, turbidity and suspended solids.