Natural hosts of four melon viruses (cucumber mosaic virus o CMV, papaya ringspot virus o PRSV, watermelon virus 2 o WMV-2 and zucchini yellow mosaic virus o ZYMV) were identified in two commercial melon farms in Costa Rica. The farms differed in management practices. Farm A had a long history of melon production in rotation with corn, sorghum and rice. Weed control was poor. Farm B was previously used as pastureland, had a shorter history of melon production, and was frequently plowed for weed control. Plant species diversity was monitored in 100 m2 quadrants on each farm over a one year period. In addition to the cultivated areas, four distinct plant communities (improved pasture field, drainage ditches, secondary forest and fallow field) in farm A, and three (spontaneus mixed species pasture field, fallow field and secondary forest) in farm B were included in the study. The number of quadrants sampled was dependent on the total cultivated area on each farm. Five sampling dates were selected during rainy and dry seasons and transition periods between seasons. Plants of each species represented in the quadrants were collected at each sampling date and identified using reference collections. Four plants of each species showing virus-like symptoms in the field were tested for the presence of the four viruses by ELISA. The total number of plant species, and the percent ground cover of each species infected at least with one of the viruses were recorded on each of the five sampling dates. A total of 86 and 72 plant species were identified in sites A and B, respectively. Fourteen plant species, 16% of the total plant species represented in site A, and six species in site B (8%) were found to be infected with at least one of the four melon viruses at different times throughout the year. All four viruses were detected in each location at each of the five sampling dates, indicating that weed species naturally occurring in and around areas of commercial melon production serve as reservoirs for the melon viruses and ensure the survival of the viruses from one production season to the next. Several new host species of three of the melon viruses (PRSV, WMV-2 and ZYMV) were identified. Previously unreported hosts of PRSV included Tridax procumbens, Cleome viscosa, Cleome spinosa, Malvaviscus arboreus and Sida rhombifolia. New hosts of WMV-2 included C. viscosa, Crotum argenteus, Musa pardisiaca and Ponsetia heterophylla. New hosts of ZYMV included Guazuma ulmifolia, Rauvolfia tetraphylla, Malachra alceifolia, Boerhavia diffusa, P. heterophylla and C. viscosa.

Las especies hospederas naturales de los virus (PRSV, WMV-2, CMV y ZYMV) que infectan el cultivo de melón (Cucumis melo L.) para la exportación en Costa Rica se identificaron en plantaciones comerciales de dos fincas ubicadas, una en la provincia de Guanacaste, y la otra en la provincia de Puntarenas. En ambas fincas se cultiva el melon con irrigación durante la época seca, pero su manejo cultural es diferente. La finca A con una larga trayectoria en el cultivo de melón en rotación con maíz, sorgo y arroz, y con poco control de malezas; mientras que la finca B con una corta trayectoria en la producción del melón y un mayor control de malezas. La diversidad de especies vegetales fue estudiada en cuadrantes de 100 m2 en cinco diferentes comunidades de plantas previamente seleccionadas en la finca A (cultivo, canal de drenaje, charral, potrero mejorado, y semi-bosque) y tres en la finca B (cultivo, charral, pastizal natural, semi-bosque). El número de cuadrantes estudiados dependió del área total cultivada en cada una de las fincas. Todas las especies de plantas representadas en cada cuadrante se recolectaron e identificaron pero solo aquellas especies que presentaron síntomas virales en el campo fueron analizadas por ELISA para determinar la presencia de los cuatro virus estudiados. La diversidad de especies, porcentaje de cobertura y época de aparición de las especies hospederas fue monitoreada durante un año calendario en cinco fechas diferentes. Un total de 86 y 72 especies de plantas fueron identificadas en las fincas A y B respectivamente. Catorce encontradas positivas por lo menos para uno de los cuatro virus. Los cuatro virus fueron encontrados en cada finca en cada fecha de muestreo indicando que la permanencia y abundancia de algunas especies hospederas garantiza la permanencia de los cuatro virus en el campo como fuente de inóculo primario para la próxima siembra. Varias especies de plantas hospederas silvestres previamente no informadas en la literatura fueron encontradas para PRSV, WMV-2 y ZYMV.

The effect of nutrient enrichment (N and P) on the phytoplankton community of La Mariposa reservoir (Venezuela) was studied. Polyethylene bags (microcosms) were filled with 10 l of filtered epilimnetic water of the reservoir, and enriched with different nutrient proportions, simulating an eutrophication process. Chlorophyll 'a', total nitrogen, total phosphorus, and phytoplankton abundance were determined. There was an increase in phytoplankton abundance because of nutrient enrichment, specially when both nutrients were present. After the experiments, Cryptophyta, Euglenophyta, and Pyrrophyta dissappeared from the microcosms, whereas Chlorophyta and Cyanobacteria increased. Numeric proportions of diatoms decreased at higher nitrogen concentration. Although the results obtained with microcosm experiments could be limited in ecological significance, they permit an useful approach to the natural situation.

Para evaluar el efecto del enriquecimiento con nutrientes sobre la comunidad del fitoplancton del embalse La Mariposa (Venezuela), se establecieron microcosmos "in situ" durante 6 días. Los microcosmos consistieron en bolsas de polietileno con 10 l de agua epilimnética filtrada del embalse, sometidos a diferentes combinaciones de enriquecimiento con fósforo y nitrógeno, para así simular un proceso de eutroficación. Se determinaron las concentraciones de clorofila 'a', la concentración de nitrógeno total y fósforo total y la proporción numérica de los diferentes grupos del fitoplancton. Como consecuencia del enriquecimiento de nutrientes, se produjo un aumento en la biomasa del fitoplancton, siendo las respuestas más pronunciadas en los tratamientos donde ambos nutrientes estaban presentes. Los grupos Cryptophyta, Euglenophyta y Pyrrophyta desaparecieron de los microcosmos fertilizados al finalizar el período de estudio, mientras que las Chlorophyta y las Cyanobacteria aumentaron sus proporciones relativas. Las diatomeas disminuyeron su proporción relativa a altas concentraciones de nitrógeno. Aunque la técnica del microcosmos tiene limitaciones en su significado ecológico, permite obtener una valiosa aproximación para entender lo que ocurre en las situaciones naturales.

An in vivo model to study the antimalaric effect of plant extracts is described. White mice (25-30g body weight) are treated subcutaneously with 0.6ml of the diluted extract starting seven days before P. berghei infection; treatment continues until death or for 30 days. Simultaneously 0.2ml of the extract are applied per os starting three days before infection. In a test of the model, treated and non-treated animals differed in body weight, survival time, haematocrite, parasitemia development, and spleen or liver weight of recent dead or killed mice.

Se cultivó plántulas de Qualea grandiflora a partir de semillas de "Cerrado", con distintas cantidades de agua, en invernadero o cámara de crecimiento, eligiendo 5 o 10 plantas al azar. Reaccionaron al limitado aporte hídrico disminuyendo la conductividad estomática y los potenciales hídrico y de turgencia. En las plantas bajo deficit hídrico no se observó ajuste osmótico. La relación raiz: vástago fue más alta bajo estrés hídrico, presentando la parte aérea menor crecimiento debido a la menor producción y expansión foliares.

The flora of the continental Island of Gorgona (Colombia) and that of the forests on the Chocó biogeographical region of Colombia and Ecuador were compared with species-area curves and species diversity indexes, either previously published or calculated using the original data of the vegetation surveys. The curves and the Shannon diversity index showed that the forest of Gorgona is less rich in tree species than the mainland sites. Furthermore, the Shannon equitability index in five continental lowland forests was higher that in Gorgona, suggesting that the number of trees per species is more evenly distributed in the continental forests. In Gorgona, seed and fruit dispersal was primarily carried out by birds (49.7 % of the species), as reported for the islands of Galapagos in Ecuador (60 %) and in the biogeographic island of the cloud forest of the Serranía de Macuira, Guajira, in the north of Colombia (51 %). In contrast, dispersal by mammals was the main mechanism for tree species in the continental forests of Cabo Corrientes, Bajo Calima (Colombia) and Los Tuxtlas (México). Although the forest at Gorgona is not particularly rich on tree species, it plays an important role in the protection of marine ecosystems. A reduction in forest cover would result in an increase in soil erosion rates and landslides that would greatly affect marine biota, particularly of coral reefs.

En este trabajo se hizo una comparación entre la flora de la isla Gorgona (Colombia) y la de los bosques del Chocó biogeográfico (Colombia y Ecuador). Para esta comparación se utilizaron curvas de acumulación de especies e índices de riqueza y diversidad, tanto publicadas por diferentes autores o generadas a partir de los inventarios florísticos originales. La riqueza del bosque de la isla Gorgona calculada a partir de curvas especie-área y del índice de diversidad de Shannon fue inferior a la de varios bosques colombianos y ecuatorianos en las tierras bajas del continente. Adicionalmente, el índice de equitabilidad de Shannon en cinco bosques del Pacífico colombo-ecuatoriano fue mayor que el de la isla Gorgona, lo cual sugiere que en los bosques continentales las especies están representados por un número similar de individuos. La ornitocoria fue el mecanismo de dispersión más importante en la isla Gorgona (49.7%), en forma similar a lo encontrado para las islas Galápagos en Ecuador (60 %) y para la isla biogeográfica del bosque nublado de la Serranía de la Macuira, Guajira, en el norte de Colombia (51 %). En contraste, la dispersión por mamíferos fue el mecanismo más importante para las especies de árboles del bosque continental de Cabo Corrientes, de Bajo Calima (Colombia) y los Tuxtlas (México). A pesar de que los bosques de la Isla Gorgona, no son especialmente ricos en especies, cumplen una importante función protectora de los ecosistemas de coral que rodean la isla. Una reducción de la cobertura boscosa tendría como consecuencia un aumento de las tasa de erosión y avalanchas que afectarían gravemente los ecosistemas marinos, en particular los arrecifes de coral.

Twenty two species of zooxanthellate scleractinian corals from the Pacific of Costa Rica are described and illustrated with macrophotographs. Keys to the genera and species are included. Their geographic distributions in Costa Rica and world-wide are noted, as well as aspects of the natural history of the species. Sixteen species have wide distributions, from the Red Sea or Indian Ocean to the Pacific coast of America, two species are endemic to the eastern Pacific, four species are found only in the Pacific Ocean; there are no species in common with the Caribbean-Atlantic. Two species, Leptoseris scabra and Pavona xarifea, are new records for the eastern Pacific.

Se describen veinte y dos especies de corales ecleractinios zooxantelados del Pacífico de Costa Rica se describen. Se incluyen claves para los géneros y especies. Se presenta su distribución geográfica en Costa Rica y en todo el mundo, así como aspectos de la historia general de las especies. Dieciséis especies tiene distribuciones muy amplias, desde en Mar Rojo o el Océano Indico hasta la costa Pacífica de América, dos especies son endémicas del Pacífico Oriental, y cuatro especies se encuentran solo en Océano Pacífico; no hay ninguna especie en común con el Caribe-Atlántico. Dos especies, Leptoseris scabra y Pavona xarifae, son registros nuevos para el Pacífico Oriental.

The life cicle of Latrodectus variegatus from cocoons collected in Bariloche, Argentina, is described. In stage IV (first free stage) 361 individually bred spiders were isolated and fed Drosophila melanogaster in the juvenile stage and Musca domestica after wards. "Stage I" is the stage following eclosion. For the study of survival, and average life expectancy, a week was taken as age interval, the first free stage was "age zero". The web is disordered, lacking a nest and located near the ground. The cocoon is pyriform, (similar to L. antheratus), but and with several layers of thread like L. mirabilis. It measures 14-18 mm, close to L. corallinus. The eggs are similar in size to other argentinian Lactrodectus. Each cocoon had a mean of 183 eggs (66% fertile, N° =549). In males, the number of moults to maturity is six in 78% of the cases and seven in 22% (similar to L. corallinus and L. antheratus). In females it is seven in 56% of the cases, eight in 39% and nine in 5%. When compared with other argentinian species females L. variegatus appear to be missing one moult. There are two critical periods of mortality: in stage IV, when specimens begin their webs to capture food and in stage VII when the male life cycle ends. The survival curves for several Latrodectus show a high mortality in the first stages of development. Nevertheless, the survival curves of L. variegatus, L. corallinus and L. diaguita share a sharp descent in the first age intervals followed by a gradual decline. This abrupt decrease is not known for L. mirabilis and L. antheratus. The life expectancy at age zero and maximum longevity in L. Variegatus are 17.32 and 73 weeks respectively, 9.01 and 54 in L. mirabilis, 5.36 and 81 in L. corallinus, 14.76 and 100 in L. antheratus and 7.76 and 62 in L. diaguita.

A group of Annona cherimolia (Mill:Annonaceae) trees was studied in Barva, Heredia, Costa Rica (June 1991-August 1992) to record egg-laying sites of the butterfly Oenomaus ortignus (Lepidoptera: Lycaenidae). Used fruits often dehydrated and fell before maturity. Eggs are laid in fruits independently of fruit ontologic state and of height above ground. Tree parts less frequently used to lay eggs are flower primordia, leaves and stems, but the larvae move to fruits when food reserves are depleted. Pupation occurs outside the fruit. Pupae emit sound, possible for defence.

Adults of soursop seed borer Bephratelloides pomorum (Hymenoptera: Eurytomidae) were collected from fruits in Maceió, State of Alagoas, Brazil. The courtship and copulation behaviours of B. pomorum were described under 27.6 ± 0.1±C, R.H. of 77.50 ± 0.8%. A virgin couple of B. pomorum was placed daily in a glass cage for observing the courtship and copulation behaviour during a period of 12 days. This procedure was repeated ten times by using groups of 10 to 12 virgin couples per replicate. The observations for each replicate were ended after the first copulation. In general, males emerged first and newly emerged females elicited male courtship and mating behaviours. The behavioural patterns of males consisted of well-defined sequences such as approaching to female, wing fanning, regulatory body movements, copulation, rubbing aedeago on female abdome, antennae and mouthparts grooming.

Foraging habitats as well as the fluctuations in vespid species abundance in Mato Grosso State, Brazil, were determined, through sampling effort per hour per collector in four cerrado sensu lato habitats, "campo úmido" (Cu), "campo sujo" (Cs), "cerrado sensu stricto" (Css), and "gallery forest" (Mg), during four periods consisting of two dry (August 1988 and June 1989) and two wet (October and December 1988) season periods. For "campo úmido", some species seem to be highly seasonal, either in the dry or wet seasons, whereas very few species occur year-round. The abundance, species composition and richness varied between habitats types and between seasons.

Specimens (733) of Istiohporus platypterus caught by sport fishing in the southern of the California Gulf were measured. The fourth spine of the dorsal fin was collected to estimate the age and individuals from 1 to 8 years were found. The majority of the specimens were between 180 and 210 cm in lower jaw-fork length. The Bertalanffy growth ecuation estimated using length was: Lt=203.6[-e-08(t+0.0015)]. Growth was shown to very fast in the early years.

A literature review and examination of several lots of tadpoles representative of the high Venezuelan Andes species (at least one species per genus) allowed identification of 41 useful characters. These are presented (with some illustrations) in a detailed description of their external morphology. Angle measurements (related to body longitudinal axis) are recommended to describe tail tip shape and location of oral apparatuses. Additionally, nineteen meristic data were used to assert morphological proportions. The identification key is based exclusively on external morphology (presence/absence, size, shape, number, location, etc.), that remains mostly unmodified in larval early and intermediate development. The key allows identification to genus for frogs and toads that occur in the region (six families, 11 genera). As a model of this proposal, the tadpole of Hyla pelidna is described and illustrated for the first time; it fits the larval characteristics of the H. labialis group (keratodont rows formula 1/2 or 2/2, marginal papillae in multiple rows, rostral gap present, dextral cloacal opening abdominal [separated from the ventral fin], caudal fins widest than caudal musculature at tail midlength, narial opening with fleshy, smooth, not protuberant rim). This is a first effort to establish an anuran larval terminology in Spanish.

Se hizo una revisión de las referencias pertinentes y se examinaron una serie de lotes de renacuajos representativos (al menos una especie por cada género) de los anuros altoandinos de Venezuela. Se presentan también una lista de 41 caracteres con algunas ilustraciones explicativas, intentando describir en detalle la morfología externa larvaria de esos anuros. Se propone emplear la medición de ángulos respecto al eje longitudinal del cuerpo para establecer la forma de la punta de la cola y la ubicación del aparato oral. Igualmente, se tomaron 19 medidas para determinar las proporciones morfológicas. Se incluye una clave para identificar a partir exclusi-vamente de caracteres morfológicos externos (presencia/ausencia, tamaño, forma, número, ubicación, etc.), los cuales no se modifican (o apenas se modifican ligeramente) a lo largo de los estadios de desarrollo larvario más jóvenes e intermedios. Esta clave sirve para identificar los renacuajos al nivel de familia y género de las ranas y sapos que habitan en la región antes mencionada. La clave abarca seis familias y 11 géneros. Adicionalmente, y como un modelo de este trabajo, se describe e ilustra por primera vez el renacuajo de Hyla pelidna, coincidiendo bastante bien con las características larvarias del grupo de H. labialis (fórmula de filas de queratodontes 1/2 o 2/2, papilas marginales en filas múltiples, diastema rostral presente, abertura cloacal diestra y abdominal [separado de la aleta ventral], aletas caudales más anchas que la musculatura caudal a la mitad de su longitud, abertura narinal con un anillo carnoso, liso, no protuberante). Este trabajo representa el primer esfuerzo para compilar en idioma español la morfología larvaria de los anfibios anuros.

Using Mark-Recapture methods the growth effort of Sceloporus scalaris was studied at La MichilÌa Biosphere Reserve, Durango, Mexico. A total of 146 recaptures on 68 individuals were obtained over four years on a 50 000 m 2 transect. To calculate the growth rate of Sceloporus scalaris individuals, we analyzed the data from two sources. The first using the recapture records of the same individuals over different seasons and the second using the records of cohorts during different periods. The growth effort of S. scalaris drastically diminishes as the organism grows. The growth rate of males and females is about equal for individuals from both clutches. In adults, where it is possible to compare among seasons, we measure quicker growth during the spring. The growth pattern of S. scalaris at La MichilÌa follows the predictions proposed by the Bertalanffy model. Maximum growth rates are in the younger age classes and these rates decrease as size increases. The growing period of S. scalaris is correlated with the seasons at La MichilÌa Biosphere Reserve. Newborn S. scalaris appear when the availability of nourishment is still the most propitious for growth at faster rates. Such adaptations to the environment determine many key population attributes of this species in this zone. The sexual maturity age of S. scalaris is very early at La MichilÌa, only 4.5 to 6 months. Undoubtedly, the growth pattern of S. scalaris at La MichilÌa Biosphere Reserve can help explain the structure and dynamics of this population.

Usando métodos de Marca-Recaptura estudiamos el esfuerzo de crecimiento de Sceloporus scalaris en la Reserva de la Biosfera de La MichilÌa, Durango, México. Se analizaron 146 registros de recaptura sobre 68 individuos en cuatro años de estudio en un transecto de 50 000 m2. El esfuerzo de crecimiento disminuye drasticamente conforme el individuo crece, es casi igual para los machos y hembras de las dos puestas, y en el caso de los adultos se registró un crecimiento más rápido en primavera. El patrón de crecimiento sigue las predicciones propuestas por el modelo de Bertalanffy. Los recién nacidos de S. scalaris eclosionan cuando la disponibilidad de alimento es todavÌa la m·s propicia. La madurez sexual de los individuos es muy precoz en La Michilía: de 4.5 a 6 meses. El patrón de crecimiento de S. scalaris en La Michilía ayuda a explicar la estructura y dinámica de esta población.

A survey of the electrophoretic variation at eleven loci -red blood cell enzymes, hemoglobins and serum proteins- was performed on a sample of 59 Miskitos stemming from the southernmost part of the Mosquito shore of Nicaragua. Seven loci, ALB, a-, b-, d-globins, LDHA, LDHB, and TPI were monomorphic; AP1, CP, HP and TF were polymorphic representing a proportion of polymorphic loci (P) of 0.364 and an average heterozygosity (H) of 0.077. Both values are within a range covered by ten Chibchan tribes of Costa Rica and Panama evaluated for the same loci -(P) = 0.364-0.182; (H) = 0.104-0.052-. The data allowed an estimation of minimum (ml = 0.0), mean (mm = 7.34) and maximum (ms = 21.9) percentages of racial admixture with blacks. For comparison, admixture was also calculated from the data -mainly blood groups- of a previous survey performed in 1960 by A. Matson and his group on a sample of a region near the border between Nicaragua and Honduras; results (ml = 6.05), (mm = 11.0) and (ms = 18.1). The values showed no statistical difference, for the mean estimates, under the assumption that the non-Indian alleles are Poisson-distributed (P=0.42). The documentation of what is supposed to be the beginning of the racial admixture of the Miskito with blacks in 1641 permitted the calculation of the rate of admixture per generation -generation length: 27 years-; its maximum value lies between 1.68 and 1.91 percent. These results indicate that the Miskito gene pool has a preponderance of features characteristic of Amerindian populations.

Se estudió la variación electroforética de 11 loci que codifican para enzimas eritrocíticas, globinas y proteínas séricas en una muestra de 59 indígenas misquitos originarios de la región sur de la Mosquitia de Nicaragua. Siete loci, ALB, a-, ò-y d-globinas, LDHA, LDHB y TPI fueron monomórficos, mientras que AP1, CP, HP y TF fueron polimórficos. Esto se traduce en una proporción de loci polimórficos (P) de 0.364 y una heterocigosis media ( ) de 0.077. Ambos valores se encuentran dentro del ámbito de variación mostrado por diez grupos indígenas de estirpe chibchense de Costa Rica y Panamá evaluados para los mismos loci [(P) = 0.364-182, ( ) = 0.104-0.052]. El análisis permitió una estimación de los porcentages mínimo (ml = 0.0), medio (mm = 7.34) y máximo (ms = 21.9) de mezcla racial con negros. A manera de comparación, esta mezcla se calculó también a partir de los resultados de A. Matson y su grupo, quienes estudiaron, en 1960, la variación genética, usando primordialmente grupos sanguíneos, en una muestra de misquitos de la región fronteriza entre Nicaragua y Honduras. Los resultados (ml = 6.05), (mm = 11.0) y (ms = 18.1) no fueron diferentes estadísticamente, para los valores medios, bajo la suposición de que los alelos no-indígenas siguen la distribución de Poisson (P=0.42). Además, la disponibilidad de una fecha en la que se supone se inició la mezcla de los mísquitos con negros, en 1641, permitió el cálculo de la tasa de mezcla por generación. Dada una duración generacional de 27 años, su valor máximo se encuentra entre el 1.68 y el 1.91 %. Estos resultados indican que el acervo genético de los mísquitos aun conserva características propias de los grupos amerindios.