Using Stata to analyze size frequency of the life cycle of a Mexican desert spider

In biology, the study of the life cycle of plants and animals helps one to understand the phenology of a particular species, which is useful in pest management or in biological conservation. Spiders are one of the most widespread animals on earth. They eat a huge variety of other animals and are good indicators of environmental changes. We studied for the first time the life cycle of an endemic desert spider (Syspira tigrina). Many spider researchers have used the direct estimation of the number of instars to describe the arachnid life cycle. Other methods are based on the analysis of the length-frequency throughout time (indirect methods). Length-frequency distributions are commonly analyzed by histograms. However, this procedure depends on grid origin, and the interval width is discontinuous and uses a fixed interval width. These problems have motivated the interest of statisticians in alternative, more computationally intensive methods. Kernel density estimators (KDEs) do not depend on the origin position and are continuous distribution estimators. In addition, there are several methods for choosing the interval width. In this study, we present in Stata the use of KDEs to examine length-frequency distributions of spider size in combination with the traditional approach using histograms.

Hábitos de alimento de juveniles y adultos de Archosargus probatocephalus (Teleostei: Sparidae) en un estuario tropical de Veracruz

Juvenile and adult food habits of A. probatocephalus were analysed during one annual cycle, sampling bimonthly over 24 h cycles, in two habitat types (with and without submerged vegetation) in the Pueblo Viejo lagoon. The species showed an omnivorous diet, feeding mainly on invertebrates (mostly peracarids) and plants (?80%), with detritus (?20%) as a secondary choice. Juvenile (small individuals) tended to consume more small invertebrates (>57%), while adult individuals (larger ones) fed mainly on plants (>40%). Some of these changes were associated with an increase in the intestine relative length as fish grew up. In the seagrass habitat and during the dry season predominated juvenile individuals, which showed a larger invertebrate consumption (mainly copepods and peracarids), whereas in the habitat without vegetation and during the rainy season, adult individuals were more common, consuming mainly detritus and plant items. Although diet was similar between day and night, feeding intensity was greater during daylight hours (P=0.041), suggesting a diurnal predator condition in this species. In this way, the life history of the species at Pueblo Viejo lagoon shows adaptations towards maximizing the use of trophic resources, according to its seasonal and spatial availability.Para analizar los hábitos de alimento de juveniles y adultos de A. probatocephalus, durante un ciclo anual se realizaron ciclos bimestrales de 24 h, en dos tipos de hábitat (con y sin vegetación sumergida), en la laguna de Pueblo Viejo. La especie mostró una dieta global omnívora constituida por invertebrados (principalmente peracáridos) y plantas (?80%), siendo el detritus (?20%) una fuente secundaria. Los juveniles (individuos pequeños) tendieron a consumir más invertebrados pequeños (>57%), mientras que los adultos (individuos grandes) consumieron más plantas (>40%). Algunos de estos cambios dietéticos están asociados con un aumento de la longitud relativa del intestino a medida que los peces crecieron. En el hábitat con pastos y durante la época de secas predominaron los juveniles, quienes mostraron un mayor consumo de invertebrados como copépodos y peracáridos, mientras que en el hábitat sin vegetación y durante la época de lluvias predominaron los adultos, los cuales consumieron más plantas y detritus. Aunque la dieta fue muy similar entre el día y la noche, la intensidad de la alimentación fue mayor durante el día (P=0.041), lo que sugiere que la especie es un depredador diurno. La historia de vida de la especie en la laguna de Pueblo Viejo, muestra adaptaciones tendientes a maximizar el aprovechamiento de la disponibilidad temporal y espacial, de los recursos tróficos

ANATOMÍA E HISTOQUÍMICA DE LA CORTEZA DE CINCO ESPECIES DE MORACEAE

We have analyzed and compared the anatomical and histochemical features of thesecondary phloem and the peridermis offour species of Ficus and Morus celtidifolia.Anatomical features shared by the four Ficus species here studied are: sieve elementsof polygonal shape arranged in radial clusters are abundant. Heterogeneous, stratifiedrays are formed by square and tangentiallydilated cells; rays form irregular fans. Amonostratified periderm is composed bya layer of sclereids in the pheloderm and asuberized phellem with wall thickenings ofpolyphenolic origin. Parenchyma cellscontain cubical and romboidal crystalsand druses. Laticifers are non articulatedand branched. M. celtidifolia rays do notform fans as in Ficus; axial parenchima dilates and packages of sclereids appear towards the periderm. Heterogeneous rays arenot stratified, laticifers are non articulatedand shorter than in Ficus. Periderm structure is similar, but thicker, than in Ficus.The bark of the species analyzed in this workhas been traditionally used for making an“amate” paper of higher quality than thatproduced with the bark of other species. Theresults of the histochemical analysis showa slightly lignified structure, abundance ofstarch, pectins and water soluble carbohydrates towards the periphery, as well as nonlignified fibers in all the species studied.These features can be related to the ease ofpaper manufacture, to adherence and agglutination properties, to the high qualityof the end product and could explain theintensive use given to these species duringprecolumbian times.En el presente trabajo se estudiaron las características anatómicas e histoquímicas delfloema secundario y peridermis de cuatroespecies de Ficus y de Morus celtidifolia.Las características que comparten las especies de Ficus son: elementos cribosos arreglados en racimos radiales, de contornospoligonales, muy abundantes, los radiosson heterogéneos, y se abren en abanicosirregulares, estratificados, formados por cé-lulas cuadradas y tangencialmente dilatadas. La peridermis formada por un solo estrato se compone de esclereidas en lafelodermis y de felema suberizado y conengrosamientos de la pared de origenpolifenólico. Presentan cristales cúbicos,drusas y cristales romboidales en célulasde parénquima, los laticíferos son de tipono articulados ramificados. Los radios en M. celtidifolia no se dilatan como en Ficus,pero el parénquima axial se dilata y seesclerifica hacia la peridermis. Sus radiosheterogéneos no muestran estratos, presentan laticíferos no articulados de menor longitud y la peridermis es muy similar peromás ancha que las de Ficus.Las especies estudiadas han sido tradicionalmente empleadas para elaborar papelamate, y cuyas cualidades son mejores quepapeles elaborados con corteza de otrasespecies, lo que de acuerdo con el estudiohistoquímico resalta la estructura pocolignificada, abundancia de almidones,pectinas y carbohidratos solubles en aguahacia la periferia que pueden estar relacionados con la manufactura, propiedades deadherencia y aglutinamiento así como confibras sin lignificar, lo que puede explicar engran parte el uso intenso que se le ha dadodesde la época prehispánica

Ceratium balechii sp. nov. (Dinophyceae: Gonyaulacales) from the Mexican Pacific

We propose a new species Ceratium balechii sp. nov., a bloom-producing dinoflagellate in the Mexican tropical Pacific, and often by mistake referred to as C. dens. In order to know its morphological variability, a morphometric study was perfomed, on the basis of 584 cells from 48 populations collected in 11 coastal localities of the Mexican tropical Pacific. Sixteen morphological characters (14 quantitative and 2 qualitative) were studied in each cell, and another 6 characters, relevant for establishing allometric relationships, were taken into account. To perform the statistical analysis, four different cell shapes were distinguished based on their appearance. A discriminant analysis distinguished two forms that were also correlated with water temperature and salinity. Two forms are proposed, C. balechii f. balechii and C. balechii f. longum. The latter occurred in water with temperature higher than 26ºC and salinity less than 32. The species is subjected to cyclomorphosis and intense synchronized autotomy in both antapical horns.The new species is compared with other morphologically similar species and intraspecific taxa (C. dens, C. dens var. reflexa, C. tripos "var. benguela", C. tripos var. dalmaticum, C. tripos var. ponticum, C. californiense, C. ehrenbergii and C. porrectum). The presence of C. dens in the Mexican Pacific is heavily questioned

Some improved Stata ado-files for nonparametric smoothing procedures

In this talk, I introduce some improved programs for nonparametric smoothing that originally were written in a very simple manner. These updated ado-files are simple too, but they are more versatile and more “Stata-like” than the original versions. The ado-files include, for density traces, boxdent (boxcar weight function) and dentrace (boxcar and cosine weight functions); for choosing the smoothing parameter in density-frequency estimation, bandw (which permits kernel specification with automatic bandwidth adjustment); for direct and discretized variable bandwidth density estimation, varwiker and varwike2, respectively; for finding critical bandwidth for a specified number of modes, critiband; and for nonparametric assessment of multimodality, bootsamb (to use in conjunction with the boot command). In spite of its simplicity, this collection of commands has proved to be very useful in the analysis of biological (and other kinds of) data, saving the analyst considerabe amounts of time and effort.