Revista de Biología Tropical

The scientific journal that researchers want for the 21^st. century: the problems of language and scope

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Photosynthetic efficiency in rhizophoracean mangroves with reference to compartmentalization of photosynthetic pigments

Photosynthetic pigments are localized in protein complexes of chloroplast membranes and their role in photosynthesis has long been established but their efficiency has not been measured in many species. The photosynthetic efficiency of four rhizophoracean mangroves, Rhizophora apiculata, R. mucronata, Bruguiera cylindrica and Ceriops decandra was studied in randomly collected propagules from Pichavaram mangrove forest (southeast coast of India) by estimating the concentration of photosynthetic pigments in protein complexes of the thylakoid membrane. Reaction centre chlorophyll (RC-chl) was maximum in B. cylindrica and minimum in R. mucronata. Of the total amount of chlorophylls, RC-chl constitutes about 50%. The light harvesting complex chlorophyll (LHC-chl) was highest in C. decandra and lowest in R. mucronata. Net photosynthesis was found to be higher in B. cylindrica and lower in R. mucronata with the respective CO2 fixation of 20.52 and 10.83 m mol m-2 s-1. A positive correlation was obtained between RC-chl and net photosynthesis. The stomatal conductance to CO2 influx was also found to be high and low in B. cylindrica and R. mucronata respectively. We refer the chlorophylls present in the reaction centre and light harvesting complex as " membrane bound chlorophyll" and propose to use this as an index for measuring the productivity of mangrove species.

Patterns of calcium oxalate crystals in young tropical leaves: a possible role as an anti-herbivory defense

Calcium oxalate crystal formation and leaf toughness were measured and compared in five species, (Cyclanthus subpalmata, Pandanus leram, Crinum amabile, Heliconia longiflora and Guzmania zahnii) pre-selected for known leaf raphide production and toughness. Nine to eleven representative individuals from each species were randomly selected for the same microenvironment. The study was conducted in Las Cruces, Costa Rica. Leaves from each species were classified as two age classes: young and mature. Leaf crystal number was quantified by light microscopy. Leaf toughness was measured with a penetrometer. For all five species, the number of crystals was highest in young leaves and lowest in mature leaves. In addition, crystal formation was inversely related both to the leaf age class and to leaf toughness. It is proposed that crystal formation may be an alternative plant defense to toughness in young leaves.

Se comparó cristales de oxalato de calcio y la dureza de la hoja en cinco especies, (Cyclanthus subpalmata, Pandanus leram, Crinum amabile, Heliconia longiflora, y Guzmania zahnii), pre-seleccionadas por tener ráfidos, clasificando las hojas como jóvenes y viejas. Se contó los cristales por microscopia de luz. La dureza de la hoja fue medida con un penetrómetro. En todas los especies, la cantidad de cristal fue mayor en hojas jóvenes y la formación estuvo inversamente relacionada con edad y dureza de la hoja. La formación de cristales puede ser una defensa alternativa a la dureza de las hojas jóvenes.

Reabsorción de nitrógeno y fósforo foliar en árboles de bosques montanos en los Andes centrales de Colombia

Mature leaves and litterfall were collected between November 1992 and February 1993 from one to three individuals of five canopy tree species of a lower montane rain forest (LMRF) at 1850 m. and five canopy tree species of an upper montane rain forest (UMRF) at 2800 m. in the Central Andes of Colombia, to determine the concentrations and percentage retranslocation of nitrogen and phosphorus. The availability of these two nutrients was measured in the soils, by means of extracts of NH3-NH4, NO2-NO3 and PO4, and incubations of surface soil samples (0-10 cm) to measure the rates of nitrogen mineralization and nitrification. In the species of the LMRF the average concentration of N in mature leaves (1.19 % dry weight) and litterfall (0.87 %) was significantly higher than in mature leaves (0.90 %) and litterfall (0.59 %) of the tree species of the UMRF. Percentage retranslocation of N and P were not significantly different between the species of these two forests. In spite of this, P retranslocation tended to be higher in the species of the LMRF where the available P in the soil was significantly lower (3.2 ppm vs. 9.0 ppm). A negative and statistically significant correlation was found between the percentage retranslocation of P and the concentration of this element in mature leaves of 12 different tropical montane forests. These results suggest that percentage retranslocation of foliar P in montane forests, could be partially controlled by the availability of this element. There were no statistically significant correlations between percentage retranslocation of N and P and specific leaf area for the ten tree species of this study. The lack of correlation may be the result of a small sample size and should be explored with a higher number of species.

Se determinaron las concentraciones y los porcentajes de reabsorción de nitrógeno y fósforo foliar en cinco especies de árboles de un bosque montano bajo (BMB) a 1850 m.s.n.m. y en cinco de un bosque montano alto (BMA) a 2800 m.s.n.m en la Cordillera Central colombiana, asi como la disponibilidad de nitrógeno y fósforo del suelo. Los porcentajes de reabsorción de N y P no fueron significativamente diferentes entre las especies de estos dos bosques. A pesar de esto, se observó que la reabsorción de P foliar tendió a ser mayor en las especies del BMB donde la concentración de P en el suelo fue significativamente más baja (3.2 ppm vs. 9.0 ppm). Cuando la reabsorción de P foliar se expresó como función de la concentración en hojas maduras en 12 tipos de bosques montanos tropicales, se encontró una correlación negativa y estadísticamente significativa. Estos resultados sugieren que los porcentajes de reabsorción de P foliar en bosques montanos estarían controlados parcialmente por la disponibilidad del elemento.

Crecimiento y mortalidad en juveniles de siete especies arbóreas en un bosque muy húmedo tropical intervenido de Costa Rica

Diameter and height growth patterns, as well as the incidence of seedling (individuals e0.3 m and <1.5 m in height) and sapling (individual e1.5 m in height and 9.9 cm DBH) mortality were studied for four years in a forest under two types of silvicultural intervention. The study is based on anual measurements of individuals from the two size categories marked one year after harvest. In the case of the seedlings, the parameters evaluated were: total height and diameter at 10 cm from the base. For the sapling category, the diameter at 1.30 m was also measured. The Clark and Clark methodology was used to evaluate the crown illumination index of all individuals. Seven tree species were studied: Cecropia (two species), Cecropia insignis Liebm. and Cecropia obtusifolia Bertol., Laetia procera (Poepp.) Eichler, Rollinia pittieri Saff, Apeiba membranacea Spruce ex Benth., Virola koschnyi Warb. y Virola sebifera Aubl. The Cecropia spp. seedlings showed the highest diameter and height growth rates, with annual mean increments in diameter of 7.8 mm/years and height of 188 cm/years. The L. procera saplings had the greatest diameter and height growth, with rates of 7.0 mm/year and 86 cm/year, respectively. Only in the case of Cecropia spp. and V. sebifera are diameter and height growth significantly correlated with the crown light index. Seedlings had the highest mortality rates in all species except Cecropia spp. and R. pittieri, where the sapling mortality was greater.

Se estudiaron por un período de cuatro años los patrones de crecimiento en diámetro y altura, así como la mortalidad de brinzales (individuos e 0.30 m altura y < 1.5m altura) y latizales (individuos e 1.5 m altura y 9.9 cm DAP) en un bosque sometido a dos tipos de intervención. El estudio se basa en mediciones anuales de individuos de las dos categorías de tamaño, marcados un año después de la aplicación del aprovechamiento. Siete especies arbóreas fueron estudiadas: Cecropia (dos especies) Cecropia insignis y Cecropia obtusifolia, Laetia procera, Rollinia pittieri, Apeiba membranacea, Virola koschnyi. y Virola sebifera. A nivel de brinzal las especie que presentaron el mayor crecimiento en diámetro y en altura fueron las especies del género Cecropia, mientras que en la categoría de latizal, fue L. Procera. El crecimiento en diámetro y en altura se correlacionó significativamente con el índice de iluminación de copa, únicamente en el caso de las dos especies de Cecropia y V. sebifera. Las tasas de mortalidad más altas se encontraron en los brinzales.

Biología floral y sistema reproductivo dePhaseolus vulgaris var. aborigineus (Fabaceae)

Observations made in Salta, northern Argentina, for a complete flowering season of five plants from several patches, allowed the authors to conclude: 1. anthesis lasts 9-13 hours and consists of two floral phases, in the last of which the stigma is not receptive; 2. stigma is receptive in the bud when anthers are not dehiscent, hence the flowers are protogynous; 3. nectar is secreted during phase 1 only; 4. the nectar composition fits that of melittophylous plants; 5. rain or drizzle do not affect the nectar composition or pollen viability because they are highly protected but do affect visitation by pollinators; 6. flowers are flag-blossom pollination units with pollen presented on stylar subapical trichomes, adapted to medium-sized hymenopterans, which transfer the pollen on their heads; 7. the ISI and RRS reproductive indeses show that the variety is partially self-compatible, but insect visitation increases reproductive success; 8. individuals of Centris sp. and a breed of Bombus atratus are the most important legitimate visitors because they work on all conspecific plants and suck nectar in few flowers ( phase 1) per plant during each visit, while individuals of Bombus opifex, the other breed of B.atratus and Megachile spp. are also legitimate pollinators but less frequent or not constant; 9. some Lepidoptera are nectar robbers because they suck nectar but do not trigger the pollen transfer mechanism.

Las observaciones realizadas sobre la biología floral y los experimentos realizados para conocer el sistema reproductivo permiten concluir que: 1. la antesis dura de 9-13 horas y pueden reconocerse dos fases florales, en la segunda el estigma no está receptivo; 2. el estigma se encuentra receptivo en los capullos, cuando las anteras no están dehiscentes, por lo tanto las flores son protóginas; 3. el néctar es secretado durante la fase 1; 4. la composición del néctar reúne las características de las plantas melitófilas; 5. ni la lluvia ni la llovizna afectan la composición del néctar o la viabilidad polínica debido a que se encuentran protegidos, pero afectan el trabajo de los polinizadores; 6. las flores son papilionadas, están adaptadas a himenópteros medianos y la transferencia polínica es nototriba; ell polen es presentado en los tricomas estilares, 7. los valores obtenidos del ISI y del RRS muestran que la variedad es parcialmente autocompatible, por lo tanto su éxito reperoductivo aumenta si trabajan los polinizadores; 8. individuos de Centris sp. y una casta de Bombus atratus son los visitantes legítimos más importantes, porque trabajan en todas las plantas conespecíficas y liban néctar en pocas flores (en fase 1) por planta durante cada visita, mientras que individuos de Bombus opifex, otra casta de Bombus atratus y Megachile spp., aunque son visitantes legítimos, trabajan con menor frecuencia y constancia; 9. algunos lepidópteros son ladrones de néctar porque liban pero no desencadenan el mecanismo de transferencia polínica.

**Morfogénesis de la fase sexual de seis especies mexicanas de helechos del género Dryopteris (Dryopteridaceae)**

The development of the sexual phase of six Mexican species of the fern Dryopteris is described and compared. The spores of all six species are monolete, ellipsoid, the perine is folded, brown to dark brown, with a tubercled outline. The germination pattern of the species is Vittaria-type and the development pattern of the prothallia is Aspidium-type. The gametangia are the common sort for the leptosporangiate advanced ferns, the necks of the archegonia have four rows of cells, with 4-5 cells each and appear 53-218 days after the sowing of the spores. The antheridia appear 46-234 days after the sowing, have three cells surrounding the androgenic cell. The first leaves of the sporophytes appear 60-262 after the sowing and, apparently in D. munchii and D. wallichiana the sporophytes have an apogamic origin.

Se describe y se compara la morfogénesis de la fase sexual de seis especies de Dryopteris. Las esporas son monoletes, elipsoidales con perina de color pardo a pardo obscuro, su superficie es rugosa de contornos tuberculados y la perina en forma de pliegues. El patrón de germinación en todas las especies es tipo Vittaria y el desarrollo protálico tipo Aspidium. Los gametangios son del tipo común de los helechos leptosporangiados del tipo avanzado, los cuellos de los arquegonios tienen cuatro hileras de células con 4 a 5 células cada una, se forman entre los 53-218 días. Los anteridios de las seis especies se formaron entre los 46-234 días después de sembradas las esporas y tienen 3 células que rodean a la célula androgénica. Los esporofitos se formaron entre los 60-262 días después de sembradas las esporas, como producto de la fecundación en D. cinnamomea, D. karwinskyana, D. maxonii y, D. rossii y son de origen apogámico en D. munchii y D. wallichiana.

**Desarrollo protálico de Lygodium heterodoxum y Lygodium venustum (Schizaeaceae)**

The development of the gametophytes of Lygodium heterodoxum Kunze and Lygodium venustum Sw. is described on the basis of spores collected in the States of Veracruz and Sinaloa, México. The germination of the spores is of the Vittaria-type or Lygodium-type. Prothallial development is of the Adiantum-type with transition to Ceratopteris-type. The gametangia are the usual for leptosporangiate ferns. The first leaf of the sporophyte appeared 85 days after spore sowing; it is digitate-flabelliform, with unicellular club shaped trichomes in margin and both surfaces, and the stomata anomocytic. Unisexual gametophytes (only with antheridia or archegonia) were found in the cultures, so the presence of hormonal substances with "antheridogenic effects" is suggested.

Se describe la morfogénesis y la morfología adulta de los gametofitos de Lygodium heterodoxum Kunze y Lygodium venustum Sw. El patrón de germinación corresponde al tipo Vittaria de acuerdo con Nayar y Kaur (1971) o al tipo Lygodium en opinión de Raghavan (1989). El desarrollo protálico es tipo Adiantum con transición al tipo Ceratopteris. Los gametangios son del tipo común de los helechos leptosporangiados y el esporofito se desarrolla a los 85 días a partir de la siembra, sus hojas son flabeliformes, con tricomas en forma de clava, unicelulares, en el margen y ambas superficies de la lámina; los estomas son anomocíticos. El experimento desarrollado transfiriendo un fragmento de medio de cultivo en el que hubieron crecido gametofitos arquegoniados y gametofitos anteridiados mas peque os a una nueva caja de cultivo en la que se sembraron esporas, dió como resultado el que, a los 14 días después de la siembra crecieran gametofitos inicialmente anteridiados con tendencia a forma espatulada sin zona meristemática ni cojinete; los anteridios se mostraron normales con anterozoides activos en agua. Se demuestra de esta manera la presencia en el medio de cultivo de sustancias con actividad anteridogénica.

**Morfología y anatomía del gametofito de Didymochlaena truncatula (Dryopteridaceae)**

Sexual phase development was studied in Didymochlaena truncatula, on the basis of spores collected in Península Moreno and Tebanca, Catemaco, Veracruz, México. The spores are monolete, ellipsoid, with perine, and non-clorophyllic. The germination pattern is of the Vittaria-type and the prothallial development is of the Adiantum-type, the adult gametophytes are cordiform to reniform and without trichomes; the gametangia are typical of the leptosporangiate ferns. The first leaf of the sporophyte appears 100 days after the sowing of the spores, the lamina is spatulate-shaped, with dichotomous venation and short capitate, unicellular marginal hairs.

En este trabajo se presenta el estudio de la fase sexual de Didymochlaena truncatula. Las espora son monoletes con perina, elipsoidales, no clorofílicas. Su germinación es tipo Vittaria y su desarrollo protálico es tipo Adiantum, el gametofito adulto es cordiforme-espatulado a cordiforme-reniforme, no presentan ningún tipo de tricoma, los rizoides no tienen cloroplastos, sus gametangios son del tipo común de los helechos leptosporangiados, las primeras hojas del esporofito se forman después de 100 días de haber sido sembradas las esporas, son de forma espatulada con venación dicotómica y tricomas unicelulares marginales, cortos y capitados.

Los quetognatos (Chaetognatha) del banco de Campeche en abril-mayo de 1986

The chaetognaths of the Campeche Bank were studied in April-May, 1986. Organisms were collected at 24 sampling stations with bongo trawls. The taxonomical identity of the specimens collected was determined with basis on McLellands key and descriptions. We calculated density (expressed as a number of organisms per 100m3), frequency of occurrence and Importance Value (as the sum of relative density and frequency) for each species and species richness for each sampling station. A dendrogram of sampling stations was constructed using the Morisita`s similarity index and the unweighted pair-group method that uses arithmetic means. Twelve species were recorded. The highest species richness was found at sampling stations located near the continental slope, whereas only one or two species were recorded at the Campeche Sound. Flaccisagitta enflata was the most abundant and widely distributed species in the study area; Sagitta tenuis was the second most abundant species and it ocurred in 79% of the sampling stations. Krohnitta pacifica and Flaccisagitta lyra were the least frequent species. The highest density of quetognaths (5 000 organisms/100m3) was recorded at some stations located at the Campeche Sound; values from 1 000 to 5 000 orgs./100m3 were recorded in the Western part of the Yucatan Peninsula. Three species groups could be recognised with basis on the species` Importance Values: The first group (IV: 75) includes F. enflata, S. tenuis, Ferosagitta hispida, K. subtilis and Serratosagitta serratodentata. The second group (IV:36) comprises four species and the third group (IV:<15) includes the least frequent and abundant species Mesosagitta decipiens, K. pacifica and Flaccisagita lyra. From the dendrogram constructed from the Morisita`s similarity index, five groups of sampling stations were distinguished. The first group included two stations located off the Northern part of the continental slope, where M. minima was the dominant species and the Simpson`s dominance index reached its lowest value (0.215). Most of the species recorded in these stations have an oceanic distribution. The second group comprised seven stations located near the upwelling zone, where F. enflata coexists with five to nine other species and the Simpson`s dominance index had an intermediate value (0.243). The species recorded in these stations have an essentially oceanic distribution and occur northwards from Cabo Catoche. The third group included 10 stations, most of which were located westward from the Campeche Sound and another one in the Yucatan Channel. In these stations F. enflata was the dominant species and the Simpson`s index reached its highest value (0.683). The fourth group included one station located in the upwelling zone, were the dominance index has its lowest value and S. serratodentata was the dominant species. The fifth group included coastal stations where F. enflata was the dominant species and the Simpson`s index reached high values. The most important characteristics of the study area during this period were: 1. Two distinct zones. The Campeche Sound in the Western part of the area and the Northern coastal stations, where F. enflata was the dominant species and the Simpson`s dominance index reached its highest values, and the oceanic Northern zone off the Yucatan Peninsula where F. enflata had low abundance and there was a higher abundance and diversity of other chaetognath species. 2. F. enflata, S. tenuis, F. hispida and K. subtilis were the dominant chaetognath species.

Al analizar la distribución, frecuencia, abundancia y Valor de Importancia de 12 especies de quetognatos encontradas en 24 estaciones de muestreo durante abril-mayo de 1986 en el banco de Campeche, se observa que la mayor riqueza específica ocurrió en estaciones oceánicas cerca del talud, en tanto que los sitios con mayor densidad de quetognatos (más de 5 000 org./ 100 m3) se ubicaron en la parte oeste del área de estudio. Las especies que formaron el elenco taxonómico son principalmente oceánicas, de aguas tropicales y subtropicales, de éstas las que obtuvieron los mayores Valores de Importancia fueron: Flaccisagitta enflata, Sagitta tenuis, Ferosagitta hispida, Krohnitta subtilis y Serratosagitta serratodentata. La similitud de Morisita entre estaciones y la dominancia de Simpson permiten definir dos regiones: una de ellas formada por las estaciones norteñas costeras y las de la sonda de Campeche donde domina F. enflata y los valores de dominancia de Simpson fueron altos y la otra que comprende las estaciones oceánicas norteñas del Banco de Campeche donde no hubo una especie claramente dominante y por tanto los valores del índice de Simpson fueron bajos.

**Periodo reproductivo y talla de madurez masiva del camarón de roca Sicyonia penicillata (Decapoda: Sicyoniidae) en Bahía Kino, Sonora, México**

The reproductive pattern of the rock shrimp (Sicyonia penicillata) was studied from January through December (1996) by sampling from boats twice a month (commercial shrimp fleet and one research cruise). Reproductive activity begins at 25 mm of tail length, but massive maturity or critical size is 55 mm of tail length. Mature organisms were found year round, but recruitment pattern analysis indicates that massive reproduction is from August through January; a second, less intense reproductive peak, occurs in March-April. Results are coincident with the gonadical maturity analysis. A migration pattern of juveniles towards shallow areas of Bahía Kino is suggested.

Se estudia el periodo reproductivo del camarón de roca Sicyonia penicillata en el área de Bahía Kino, Sonora, de enero a diciembre de 1996 mediante muestreos quincenales efectuados a bordo de embarcaciones de la flota camaronera comercial y un crucero de investigación durante julio. La actividad reproductiva de la especie inicia a partir de los 25 mm de longitud abdominal, pero la talla de madurez sexual masiva de la especie se ubicó en 55 mm de longitud abdominal. Se encontraron organismos maduros todo el año, pero el patrón de reclutamiento indica que existe un periodo reproductivo masivo de agosto a enero; un segundo periodo, menos intenso ocurre en marzo y abril. Estos resultados son coincidentes para los meses en los que se cuenta con datos de madurez gonádica. Se postula la idea de un posible patrón de migración de juveniles hacia áreas someras de Bahía Kino.

**Comparación de la tasa de crecimiento de Penaeus vannamei (Decapoda: Penaeidae) en cultivos semi-intensivos de invierno y de verano**

The growth rates of Penaeus vannamei in Sinaloa, Mexico, during winter and summer semi-intensive cultures, were compared using a linear regression model that considered age and accumulated temperatures as independent variables. In the first case, the growth curves slope differed significantly, indicating a slower growth in winter; when using accumulated temperatures there was no difference in growth rates indicating that P. vannamei at 12 g (cocktail size) may be harvested when the accumulated weekly temperature reaches 300-350°C, depending on the initial size of the organisms in culture.

Cangrejos braquiuros (Brachyura) del arrecife de Cabo Pulmo-Los Frailes y alrededores, Golfo de California, México

Fragments of the coral Pocillopora elegans collected in 1988 and 1989 produced 281 specimens of brachyurans. There were 30 species and subspecies in eight families, and 22 are new records for the Cabo Pulmo-Los Frailes reef. Including earlier records, there are now 61 species and subspecies (19 families) from the area. Majidae had the largest number of species (23), followed by Panopeidae (9), and Xanthidae (6). Most abundant were Trapezia ferruginea (71 specimens), Theleophrys cristulipes (39) and Microcassiope xantusii xantusii (29). The species were sorted out in four zoogeographic groups: Indopacific (8.5%), Amphiamerican (5.1%), Eastern Pacific (76.3%), and Mexican Pacific endemics (10.1%). The reef represents only 0.004% of the Gulf area but harbors 21% of all species recorded from the gulf of California, western coast of Baja California Sur and exclusive economic zone of Nayarit and Sinaloa.

El análisis de los fragmentos del coral Pocillopora elegans recolectados en siete campañas de muestreo durante 1988 y 1989 resultó en 281 ejemplares de braquiuros, identificándose 30 especies de ocho familias, de las cuales 22 especies son nuevos registros para el área. Había 39 especies de braquiuros registradas; ahora hay 61 especies de braquiuros, repartidas en 16 familias. Majidae contiene el mayor número de especies (23), seguida por Panopeidae (9) y Xanthidae (6). Las especies más abundantes fueron Trapezia ferruginea (71 ejemplares), Theleophrys cristulipes (39) y Microcassiope xantusii xantusii (29). Todas las especies se agruparon en cuatro grupos zoogeográficos: indopacífico (8.5%), anfiamericano (5.1%), Pacífico oriental (76.3%) y endémico del Pacífico mexicano (10.1%). Las especies de braquiuros de este arrecife (con sólo 0.004% de la superficie de la región) representan el 21% de todas las especies registradas para la región del golfo de California, costa occidental de Baja California Sur, áreas costeras de Nayarit y Sinaloa y zona económica exclusiva de estos estados.

Dry mass estimates of some tropical aquatic insects

Relationships of body mass and head capsule width were developed for Thraulodes sp., Haplohyphes sp. (Ephemeroptera), Leptonema sp., Phylloicus sp. Nectopsyche sp. (Trichoptera), and Anacroneuria sp. (Plecoptera). The organisms were collected with a Surber net (0.1296 m² and 0.286 mm mesh size) on the Orituco river, Venezuela. The number of specimens used in the analysis for the species studied, was different (from 84 to 103 specimens). Regression analysis indicated that all relationships were best expressed by a power function rather than by linear or exponential equation. Analyses of the relationships reveal interspecific differences among insects of the same order. Species-specific relationships are recommended to be used whenever possible since, depending on the species, the underestimation of mass could be as much as 56%.

Se calcularon las relaciones entre la masa del cuerpo y el ancho de la capsula cefálica para Thraulodes sp., Haplohyphes sp. (Ephemeroptera), Leptonema sp., Phylloicus sp., Nectopsyche sp. (Trichoptera), y Anacroneuria sp. (Plecoptera). Los análisis de regresión indicaron que todas las relaciones se expresan adecuadamente mediante la función potencial en vez de la función exponencial o linear. El análisis de las relaciones obtenidas revela diferencias entre los insectos pertenecientes a un mismo Orden. Se recomienda el uso de relaciones específicas para cada especie siempre y cuando sea posible, debido a que, dependiendo de la especie, la subestimación de la masa puede llegar a ser hasta de un 56%.

Dry mass estimation of tropical aquatic insects using different short-term preservation methods

Relationships of body mass and head capsule width were calculated for Thraulodes sp., Haplohyphes sp. (Ephemeroptera), Leptonema sp. and Nectopsyche sp. (Trichoptera), and Anacroneuria sp. (Plecoptera) using different preservatives (Freezing, Formaldehyde 4% and Kahle). The organisms were collected monthly during a year on the Orituco river, Venezuela with a Surber net (0. 1296 m² and 0.286 mm mesh size). The data presented here are representative of the organism conditions year around. No attempt was made to quantify intersample variation. Regression analysis indicated that all relationships were highly correlated for any of the fixatives used. Changes in dry mass per unit change of head capsule width, vary among species and preservatives with no clear relationship among them. Changes in dry mass calculated as the difference between dry mass of preserved samples to those of unpreserved ones, indicate that all fixatives underestimate dry mass by as much as 85.4%, except for Nectopsyche sp. whose dry mass was always overestimated. These results provide further evidence on the effect of preservatives on dry mass losses. Even when working with tropical species, any study in which biomass is going to be determined should consider the effect of preservatives on dry mass.

Se calcularon las ecuaciones para las relaciones entre la masa del cuerpo y el ancho de la cápsula cefálica para Thraulodes sp., Haplohyphes sp. (Ephemeroptera), Leptonema sp., Nectopsyche sp. (Trichoptera) y Anacroneuria sp. (Plecoptera) usando diferentes preservativos (Congelamiento, Formol 4% and Kahle). El análisis de regresión indicó que todas las relaciones obtenidas son altamente significativas para cada uno de los preservativos utilizados. Los cambios en la masa del cuerpo por unidad de cambio en el ancho de la cápsula cefálica, son diferentes para cada especie y preservativo, sin haberse obtenido una clara relación entre ellos. La compararación entre los valores de masa obtenidos con los diferentes preservativos y los obtenidos con muestras no preservadas, indica que todos los preservativos subestiman la masa seca hasta en un 85,4%, excepto en el caso de Nectopsyche sp. cuya masa corporal fue siempre sobre-estimada. Los resultados presentados en este trabajo nuevamente indican, aún trabajando con insectos acuáticos tropicales, que cualquier estudio en el cual la biomasa va a ser determinada, debe de tener en cuenta el efecto que los preservativos producen en la disminución de la masa corporal.

**Spiders (Araneae) captured by Trypoxylon (Trypargilum) lactitarse (Hymenoptera: Sphecidae) in southeastern Brazil**

Fifty one nests and 200 cells of Trypoxylon (Trypargilum) lactitarse were obtained from trap-nests (cut bamboo stems) in Santa Carlota Farm (in two habitats: Itaoca Section-IS and Santana Section-SS), Cajuru and on the São Paulo University Campus, Ribeirão Preto (RP), both in the State of São Paulo, Brazil. The prey (spiders) of 18 cells from IS, 38 from SS and 70 from RP were identified. Nesting most frequently occurred during the hot and wet seasons (September to April). T. lactitarse preyed upon representatives of ten spider families. Araneidae (96.6%) (orb-weaver spiders) were the most frequent. Eustala sp.1 was the most frequently collected species in the three habitats (31.6% in IS, 20.1% in SS and 48.7% in RP), followed by Acacesia hamata (19.5%) and Alpaida leucogramma (10%) in IS, by Parawixiaaudax (16%) and A. hamata (15.4%) in SS and by P.audax (17.9%) and Eustala sp.2 (12%) in RP. The sizes of the reproductive niches were significantly different. There was a positive correlation between reproductive niche width and evenness.

New North American Lachesilla in the Forcepeta group (Psocoptera: Lachesillidae)

Ten species of Lachesilla, belonging in species group Forcepeta, are here described and ilustrated; three of them occur exclusively in the United States, six are exclusive to México and one occurs mostly in Mexico, extending also to Guatemala. They differ among themselves, and are separated from other species in the group, mostly on genital characters. The location of the types is indicated in each description.

Se describen e ilustran, diez especies de Lachesilla en el grupo Forcepeta. Tres de ellas han sido recolectadas exclusivamente en los Estados Unidos, seis son exclusivas de México, y una se ha registrado en el suroeste de los Estados Unidos, en México y en Guatemala. Las especies descritas son: L. carinata n. sp., de Chiapas, Campeche, Hidalgo, Morelos, Oaxaca, San Luis Potosí, Tabasco, Tamaulipas y Veracruz; L. carinatoides n. sp., de la Isla María Madre, Guerrero y Oaxaca; L. cladiumicola n. sp., de una sola localidad en Levy County, Florida; L. estradaorum n. sp., de una sola localidad en Los Tuxtlas, Veracruz; L. filicicola n. sp., de una sola localidad en Tabasco; L. floridana n. sp., de varias localidades en Florida; L. laciniosiforceps n. sp., de Florida, Louisiana, Chiapas, Coahuila, Guerrero, Hidalgo, Jalisco, Nuevo León, Puebla, San Luis Potosí, Tamaulipas, Veracruz, Yucatán, y Guatemala; L. maculata n. sp., de Chiapas, Tabasco y Veracruz; L. rectiforceps n. sp., de Veracruz, Chiapas y Oaxaca, y L. typhicola n. sp. de Florida, Illinois, Indiana, Michigan y Minnesota. Todas ellas difieren entre sí, y de las otras especies del grupo, en caracteres de venación y, principalmente, en caracteres genitales de los dos sexos. La locación de los tipos se indica en las descripciones respectivas.

Diversidad de hormigas (Hymenoptera: Formicidae) en un gradiente sucesional del bosque nublado (Nariño, Colombia)

We evaluate the potential use of ants as indicator taxa of cloud forest recovery in La Planada Reserve, at southwestern Andine slope in Nariño, Colombia. The ants were sampled from February through August 1995, using pitfall traps, tuna baits and manual collection, in seven localities representing forest successional stages: cattle ground, grassland (three year old), two ten year old forests and 20 year old, exploit and primary forests. We found 63 species (29 genera) with a 20-26 species richness per locality, with the exception of the ten year old forest (12 species). There were no any statistical differences in species richness and diversity among samples and study sites. Nevertheless taxonomic composition was associated with the successional stage (Simple Matching Coefficient). Ants can be used as indicators of forest recovery at La Planada.

Para evaluar el uso de las hormigas como indicadores ecológicos del grado de recuperación del bosque en la Reserva Natural La Planada (Nariño, Colombia), se colectaron hormigas entre Febrero y Agosto de 1995 en siete lugares correspondientes a un gradiente sucesional: potrero, pastizal, dos bosques de 10 años y uno de 20 y bosques entresacado y maduro. Se encontraron 63 especies de hormigas (29 géneros), con una riqueza entre 20 y 26 especies por lugar de estudio, excepto uno de los bosques de 10 años (12 especies). No se hallaron diferencias estadísticamente significativas en la riqueza y diversidad de especies entre los muestreos ni entre los lugares de estudio. Sin embargo, la composición de especies de hormigas si cambió entre los diferentes estadios sucesionales y los discriminó y asoció al analizarla con el índice de similaridad Simple Matching. Se propone la utilización de las hormigas en planes de monitoreo en La Planada utilizando la composición de especies como parámetro indicador.

Cross-shelf distribution of nutrients, plankton, and fish larvae in the San Blas Archipelago, Caribbean Panamá

To investigate possible seasonal patterns in water quality and plankton distribution, weekly samples were collected in a coral reef lagoon and in surrounding nearshore waters over a two year period. Additionally, two oceanographic surveys were also conducted in a larger area surrounding the primary study site during the seasonal extremes. The resulting information corroborated previous observations that this area is as an oligotrophic environment. The larger-scale sampling revealed seasonal variation in cross-shelf gradients in plankton, fish-egg and larval densities that are probably related to the strong onshore winds that are typically present during the dry season. Although some limited nutrient enrichment occurs in parts of the nearshore area during the rainy season, the highest plankton density and biomass were recorded in shallow nearshore waters during the windy dry season. Larvae of numerous fish taxa were collected in these nearshore areas during the dry season, suggesting seasonal aggregation. During the rainy season, fish larvae were spread more evenly across the shelf and into nearshelf waters.

Con el propósito de investigar posibles cambios estacionales en la calidad del agua y en la distribución del plancton se realizaron colectas semanales en un área de arrecifes coralinos. En adición, se llevaron a cabo alrededor del sitio de estudio, dos cruceros oceanográficos cubriendo un área geográfica mayor durante condiciones estacionales extremas. La información obtenida corrobora que el área de estudio es un ambiente oligotrófico. Los muestreos de mayor escala geográfica indican la presencia de variación estacional en los gradientes de plancton, huevos y larvas de peces a lo largo de la plataforma continental, lo que posiblemente está relacionado con los fuertes vientos del norte típicos de la estación seca. Aunque un limitado enriquecimiento con nutrientes ocurre en el área cercana a la costa durante la estación lluviosa, la mayor densidad y biomasa del plancton se observó durante la temporada seca. Larvas de numerosas taxa de peces se recolectaron en las áreas cercana a la costa durante la estación seca, lo que sugiere un proceso de concentración estacional. Sin embargo, durante la estación lluviosa ocurrió una distribución más homogénea de larvas a lo largo de la plataforma continental y en aguas adyacentes.

Status of some populations of Mexican salamanders (Amphibia: Plethodontidae)

Populations of Mexican plethodontid salamanders have been surveyed non-systematically over the last 25 years. In light of many reports of disappearance of amphibians around the world, we checked for persistence of reported species at ten of these sites. All of the commoner species persist (we observed individuals representing a total of 30 species). While observed densities of many species of Mexican plethodontids are lower to much lower than was the case 20 to 25 years ago, evidence for recent extinctions, such as has been reported for amphibian taxa elsewhere, is equivocal or lacking. Habitat modification has contributed to difficulties in finding certain species.

Poblaciones de varias especies de salamandras pletodóntidas en México han sido monitoreadas de manera no sistemática durante los últimos 25 años. Diez de éstas poblaciones fueran visitadas recientemente con el propósito de verificar la persistencia de las especies reportadas para dichas localidades. Nuestras observaciones confirman la persistencia local de más de 30 especies cuyo estatus era desconocido, aunque la frecuencia de observación de estas especies es en general menor que en fechas anteriores. Estas observaciones son particularmente relevantes dada la situación actual de preocupación por la disminución mundial de anfibios.

**Anidación de la tortuga Dermochelys coriacea (Testudines: Dermochelyidae) en playa Gandoca, Costa Rica (1990 a 1997)**

The nesting of the leatherback sea turtle was studied in Gandoca Beach, an important nesting beach on the southeastern Caribbean coast of Costa Rica, in the Gandoca/Manzanillo National Wildlife Refuge. Nesting was recorded from 1990 to 1997 (each February through July). Nesting peaked in April and May (depending on the year); 16 biological paramenters were recorded and part of the rookery was tagged with monel tags. During this period 1 045 females were studied and 3 484 nests were recorded; 534 nests was the yearly mean, (range 226-1 135), 20.8 % of the nests were relocated to hatcheries, as a conservation effort to prevent loss of nests. Mean curve carapace length was 154.65 cm and width 112.83 cm. Mean normal number of eggs/nest was 79.28 and 35 yolkless. Each turtle laid an average of 2.5 nests per season with an internesting interval of 9 days. In 1997, 39% of the nesting females had been previously tagged in Gandoca Beach and a few also in Colombia (Urabá Gulf), Pacuare and Tortuguero (Costa Rica). Poaching activity, beach debris and extensive erosion represent the main hazards that are leading to a decline of the sea turtles in Gandoca.

La anidación de la tortuga baula fue estudiada en playa Gandoca, una importante playa de anidación de tortugas marinas localizada al sureste de la costa Caribeña de Costa Rica, dentro de los límites del Refugio Nacional de Vida Silvestre Gandoca/Manzanillo (82° 37' O, 09° 37' N). Entre 1990 y 1997, se desarrollaron campañas de observación de la anidación entre los meses de febrero a julio de cada año; 16 variables de la anidación fueron anotadas y una parte de la colonia fue marcada con marcas monel y 3 484 nidos fueron encontrados; durante este periodo se depositaron un promedio de 534 nidos por temporada, 1,135 nidos fue el máximo de anidación anual, mientras que 226 nidos fue el mínimo, el 20.8% de los nidos fueron relocalizados en los viveros. El promedio de la longitud curva del caparazón de las hembras fue de 154.65 cm y el promedio del ancho curvo del caparazón fue de 112.83 cm. Las observaciones mostraron que el promedio de huevos normales para este periodo fue de 79.28, mientras que el promedio de huevos vanos fue de 35. La recolección ilegal de huevos, la basura sobre la playa y la erosión intensiva son parte de los problemas más importantes que están causando el declive de las tortugas en Gandoca.

**Colonization of Socorro Island (Mexico), by the tropical house gecko Hemidactylus frenatus (Squamata: Gekkonidae)**

Conducta alimentaria de cuatro especies de aves playeras (Charadriiformes:Scolopacidae) en Chametla, B.C.S., México

Feeding behaviour of four species for large shorebirds (Scolopacidae) was studied in a tidal mudflat, Chametla, Mexico, to determine the foraging efficiency of Limosa fedoa, Numenius phaeopus, Numenius americanus and Catoptrophorus semipalmatus in a stopover/wintering area; and their activity with the tide cicle. The study area was visited in the winter of 1993 during the daylight hours. Each species was observed for 15 min during each tide type. The tide type does not affect the frequency with which the species use the different foraging strategies. In general, probing was more efficient than pecking. Considering distribution and prey, L. fedoa had the highest efficiency with this feeding strategy. Both species of Numenius were more efficient with pecking than other species. C. semipalmatus has the highest efficiency because it is an oportunistic species, L. fedoa is generalistic, both Numenius are especialists and C. semipalmatus is oportunistic.

A technique for extraction and Thin Layer Chromatography visualization of fecal bile acids applied to neotropical felid scats

Fecal bile acid patterns have been used successfully to identify scats. Neotropical felid scats are capable of this biochemical identification because they present low concentrations of plant pigments that would interfere in fecal bile acids detection. However, neotropical felid scats have poor quantities of bile acids, so we developed in this work a proper technique for their extraction, visualization and determination. Twenty eighth feces of seven different felid species, collected from Zoological and Wildlife Parks, were dried and pulverized. The procedure for analyzing feces is : Take one g of pulverized feces and shake for 3 hr at room temperature in 20 ml benzene : methanol; filter and evaporate to 5 ml. Spot on TLC plate and develop in toluene :acetic acid:water. Dry and visualize with anisaldehyde. Field collected scats could be identified by the bile acids pattern revealed by this specific technique and ,then, used as a source of information for distribution, density and food habits studies.

Los patrones de ácidos biliares fecales han sido utilizados satisfactoriamente para identificar heces. Las heces de félidos neotropicales son propicias para ser identificadas bioquímicamente, ya que contienen baja concentración de pigmentos vegetales que pudieran interferir en la detección de ácidos biliares. Sin embargo los ácidos biliares se encuentran en bajas concentraciones en las heces, por lo cual desarrollamos en este trabajo una técnica apropiada para su extracción, visualización y determinación. Veintiocho heces de diferentes félidos recolectadas de Zoológicos y Estaciones de Fauna Silvestre fueron secadas y pulverizadas. El procedimiento para analizar las heces es : Tomar un gramo de feca pulverizada y agitar en 20 ml de benceno :metanol a temperatura ambiente durante 3 hr ; luego filtrar y evaporar hasta 5 ml. Sembrar en placa de TLC y desarrollar en tolueno :ác. acético :agua. Secar y revelar con anisaldehído. Las heces recolectadas en el campo podrían ser identificadas a través de los patrones de ácidos biliares evidenciados con esta técnica específica, y ser entonces utilizadas como fuente de información en estudios sobre distribución, densidad y hábito alimenticio.

Mamíferos terrestres de la Reserva de la Biosfera de Sian Kaan, Quintana Roo, México

Based on sampling at seven localities and an extensive bibliographic research, we present a species list of terrestrial mammals of the Sian Kaan Biosphere Reserve, Quintana Roo, Mexico. During 57 days of fieldwork we used Sherman and Tomahawk traps, mist nets, rifles, collected data of trails and made direct observations. We recorded 70 species, eight orders, 22 families, and 57 genera. Six new records are added: Marmosa mexicana, Micronycteris microtis, Micronycteris schmidtorum, Eptesicus furinalis, Rhogeessa parvula, and Ototylomys phyllotis. Twelve species are listed as threatened following the Official Mexican Norm: Tamandua mexicana, Micronycteris brachyotis, Lonchorhina aurita, Alouatta pigra, Ateles geoffroyi, Herpailurus yagouaroundi, Leopardus pardalis, Leopardus wiedii, Panthera onca, Eira barbara, Potos flavus and Tapirus bairdii. Thirteen species are endemic to Mesoamerica: M. mexicana, T. mexicana, Mormoops megalophylla, Tonatia evotis, Bauerus dubiaquercus, A. pigra, A. geoffroyi, T. bairdii, Sciurus deppei, Sciurus yucatanensis, Heteromys gaumeri, O. phyllotis, Reithrodontomys gracilis and one endemic to Mexico: Peromyscus yucatanicus. We present tables of records for every locality and corresponding vegetation types for every species. Of 65 registered species, all were recorded in medium semievergreen forest, with 50% exclusively for this vegetation type. A reference collection was established with 200 specimens, representing 43 species.

Con base en el muestreo de siete localidades y una extensa revisión bibliográfica, se obtuvo la lista de especies de mamíferos terrestres de la Reserva de la Biosfera de Sian Kaan estado de Quintana Roo, México. Durante 57 días de campo, se utilizaron trampas Sherman, Tomahawk, redes de niebla y escopetas, se registraron rastros y observaciones directas. Se registraron 70 especies, ocho órdenes, 22 familias y 57 géneros. Se encontraron seis especies como nuevos registros: Marmosa mexicana, Micronycteris microtis, Micronycteris schmidtorum, Eptesicus furinalis, Rhogeessa parvula y Ototylomys phyllotis. Doce especies son catalogadas bajo algún riesgo ecológico según la Norma Oficial Mexicana; trece especies son endémicas a Mesoamérica y una endémica de México. Se presentan cuadros de abundancia relativa, registro por localidades y por tipo de vegetación de cada especie.

**Late dry season habitat use of common opossum, Didelphis marsupialis (Marsupialia: Didelphidae) in neotropical lower montane agricultural areas**

Three Didelphis marsupialis were radio tracked during late dry season (23 February-26 April, 1983) in agricultural area at 1500 m elevation in Central Valley, Costa Rica. All animals were nocturnally active, significantly more so between 2100-0300 h. Fifty diurnal den site locations were found, 96% inside tree cavities in living fence rows or abandoned squirrel nests in windbreaks. Two females occupied 3.4 and 3.1 ha 95% home ranges, moving an average 890 and 686 m nightly respectively. The male occupied a 5.6 ha 95% home range for 42 days overlapping 90% of females' home ranges. Over the next 15 days, he moved 1020 m south, establishing three temporary home ranges. During nocturnal movements, windbreaks and living fence rows were used in higher proportion than available, while pasture, roads and cultivated lands were used less then available within 100% home ranges. Abandoned coffee and spruce plantations, fruit orchards and overgrown pastures were used in equal proportions to availability in 100% home ranges. Opossum conservation techniques in coffee growing areas include promoting spruce windbreaks, living fence rows, and garbage dumps.

Reproduction and dental age classes of the little water opossum **(Lutreolina crassicaudata) in Buenos Aires, Argentina**

Distribución geográfica y depredación de Porites lobata (Anthozoa: Scleractinia) en la costa occidental de México

The hermatypic coral Porites lobata Dana, 1846 is one of the most important species in Central American reef communities, recorded in México only in 1992, at the Revillagigedo Archipelago. This paper describes the geographic distribution and predation pressure on P. lobata in the west coast of México, based on field observations and literature data. The species is distributed in México on a coastal section of about 200 km, from Nayarit (20° N) to Colima (19° N), and in the Revillagigedo Islands (18° N); P. lobata does not occur in the Gulf of California (23° to 30° N), or at coral communities placed from 17° N to 15° N. Its disjunct distribution can be explained considering the Revillagigedos as larval emiter to the mainland, using the Northequatorial Countercurrent as dispersal mechanism. Comparing coral communities where P. lobata is found, it was more abundant in the Revillagifedos than at the mainland. However, predator damage seems to be greater in Nayarit-Jalisco-Colima than in the oceanic islands, possibly because corallivore fishes were less abundant in the latter. Population density of coral bioeroders (sponges, polychaetes, spinculans and bivalves) in P. lobata eas similar and sometimes higher at the Revillagigedos than in coastal sites, suggesting the possibility of a primary productivity diffeerential among those locations.

El coral hermatípico Porites lobata Dana, 1846 es, una de las especies más importantes en las comunidades arrecifales de América Central, pero fue registrada en México hasta 1992, en el Archipiélago de Revillagigedo. El objetivo del presente trabajo fue el de dar a conocer la distribución geográfica y algunos aspectos de la biología de P. lobata en la costa occidental de México, a partir de observaciones de campo y datos de literatura. Esta especie se distribuye en México dentro de un segmento de costa de aproximadamente 200 km, desde Nayarit (20° N) hasta Colima (19° N), y en las Islas Revillagigedo (18° N); P. lobata no aparece en el Golfo de Califomia (23° a 30° N), o en comunidades coralnas situadas de los 17° N a los 15° N. Su distribución disjunta puede ser explicada tomando en cuenta que el emisor larval hacia el continente deben ser las Revillagigedo, utilizando la Contracorriente Norecuatorial como mecanismo de transporte y dispersión. Comparando las comunidades coralinas donde ha sido localizado, P. lobata era mucho más abundante en las Revillagigedo que en el continente. Sin embargo, los daños causados por los dedepredadores parecen ser mayores en Nayarit- Jalisco- Colima que en las islas oceánicas, quizá debido a que los peces coralívoros son poco comunes allí. La densidad poblacional de los bioerosionadores (esponjas, poliquetos, sipuncúlidos y bivalvos) fue similar y a veces mayor en las colonias de P. lobata de las Revillagigedo que en aquellas de la costa continental, lo que sugiere la posibilidad de que haya un diferencial en la productividad primaria de esas localidades.