Redescription of the larva of Neoerythromma cultellatum (Hagen in Selys, 1876) (Odonata: Coenagrionidae: Coenagrioninae).

The final instar of Neoerythromma cultellatum (Hagen in Selys, 1876) is redescribed and illustrated based upon reared specimens from Turrialba, Cartago, Costa Rica. This is a detailed complement of the original description provided by García-Díaz (1938) and illustrated with high quality photos of the larval morphology. The larva of N. cultellatum is characterized by a slender, spinulose, and yellow to yellowish-brown body, premental setae 3+1, five palpal setae, male cerci long, and caudal lamella lanceolate, with obvious node, spotted, and markedly tracheate.

Variación estacional y características fisicoquímicas e hidrológicas que influyen en los macroinvertebrados acuáticos, en un río tropical / Seasonal variation, physicochemical and hydrological characteristics that influence aquatic macroinvertebrates, in a tropical river

Introducción: La distribución de los macroinvertebrados acuáticos en los ríos puede estar determinada por el tipo del sustrato, la forma del canal del río, el régimen hidrológico y las interacciones con factores bióticos y abióticos. En Costa Rica se desconoce en gran parte de los ríos, las variaciones en la distribución de los macroinvertebrados acuáticos producto de las transiciones y consecuentes variaciones en características fisicoquímicas e hidrológicas. Objetivos : 1) Estudiar el cambio del ensamblaje de macroinvertebrados acuáticos en dos sitios dentro del cauce del Río Naranjo, durante los cuatro periodos hidrológicos del año; 2) determinar la relación entre las variables fisicoquímicas, sustrato y el caudal con el ensamblaje. Metodología: El estudio se realizó en el Río Naranjo, Costa Rica, en dos sitios de muestreo durante un año, evaluando los cuatro periodos hidrológicos del año. En cada sitio de muestreo se obtuvieron valores de velocidad y profundidad del agua, caudal, oxígeno disuelto, pH, conductividad, sulfatos, amonio, nitrato, silicatos, fosfatos y sustrato, y se obtuvo una muestra de macroinvertebrados acuáticos por cada tipo de microhábitat determinado por la velocidad del agua. Se realizó una prueba PERMANOVA de dos vías, para determinar si existe una diferencia entre la abundancia de macroinvertebrados acuáticos, por periodo y entre sitios. Se hizo un análisis de correspondencia canónica para observar la relación entre los macroinvertebrados acuáticos y los factores ambientales. Por último, se realizó una prueba de Spearman para determinar la relación positiva o negativa de las variables con los macroinvertebrados Resultados: Hubo una mayor abundancia durante la estación seca, mientras que durante la transición de la estación seca a la lluviosa se registró la menor abundancia de organismos. El ACC indicó que el primer eje presentó una relación positiva con el sustrato limo y arena, y una relación negativa para las variables velocidad de corriente y sustrato rocoso. El segundo eje presentó una relación positiva con el caudal y los nitratos, y negativa para el sustrato canto rodado. La mayoría de los organismos mostraron una respuesta negativa al aumento del flujo y los nitratos. Discusión: Conforme aumenta el caudal, aumenta la velocidad del agua y no todos los organismos registrados en el Río Naranjo cuentan con características para sobrevivir a estas condiciones. Además, la profundidad también aumenta junto con la fuerza de arrastre, provocando el movimiento de los sustratos de menor tamaño y una remoción de organismos. El aumento de nitratos puede generar una disminución de los organismos más sensibles como Plecoptera y Ephemeroptera. A pesar de las variaciones fisicoquímicas y de caudal registradas en el Río Naranjo, éstas no fueron lo suficientemente fuertes como para variar el ensamblaje de macroinvertebrados acuáticos, por lo que la cuenca por el momento no cuenta con factores estresantes que elimine organismos durante uno o varios meses del año.

Introduction: The distribution of aquatic macroinvertebrates in rivers may be determined by the type of substrate, the shape of the river channel, the hydrological regime, and interactions with biotic and abiotic factors. Variations in the distribution of aquatic macroinvertebrates due to transitions and variations in physicochemical and hydrological characteristics are unknown in most rivers. Objectives: 1) to study the change in the aquatic macroinvertebrates assemblages in two sites in Naranjo River, during the four hydrological seasons; 2) to determine the relationship between the physicochemical variables, substrate and flow with the assemblages. Methodology: The study was conducted in the Naranjo River, Costa Rica, at two sampling sites during one year, evaluating the four seasons of the year. In each station we measure, values of water velocity and depth, flow rate, dissolved oxygen, pH, conductivity, sulfates, ammonium, nitrate, silicates, phosphates, and substrate were obtained, and a sample of aquatic macroinvertebrates was obtained for each type of microhabitat determined by water velocity. Two-way PERMANOVA was made to determine if there is a difference among aquatic macroinvertebrate abundance, per period and between sites. Canonical correspondence analysis was used to observe the relationship between aquatic macroinvertebrates and environmental factors. Finally, a Spearman's rank correlation coefficient was performed to determine the positive or negative relationship of variables with macroinvertebrates. Results: There was a greater abundance during the dry season, while during the transition from dry to the rainy season, the lowest abundance of organisms was recorded. The CCA indicates that the first axis presented a positive relationship with the silt and sand substrate and a negative relationship for the current velocity and rock substrate variables. The second axis showed a positive relationship with flow and nitrates and negative for the pebble substrate. Most organisms showed a negative response to increased flow and nitrates. Discussion: As flow increases, current velocity increases, and not all organisms recorded in the Naranjo River have the characteristics to survive these conditions. In addition, the depth also increases along with the drag force, causing movement of smaller substrates and removal of organisms. Increased nitrates can lead to a decrease in more sensitive organisms, such as Plecoptera and Ephemeroptera. In spite of the physicochemical and flow variations registered in the Naranjo River, these were not strong enough to vary the assemblages of aquatic macroinvertebrates, so the basin does not have stressful factors that eliminate organisms during one or several months of the year.

Primer registro del género Interocoris (Heteroptera: Naucoridae) en Centroamérica y observaciones sobre Interocoris mexicanus / First record of the genus Interocoris (Heteroptera: Naucoridae) from Central America and observations on Interocoris mexicanus

Introducción: La familia Naucoridae, de distribución mundial, se encuentra dividida en cinco subfamilias, de las cuales cuatro de ellas y seis géneros han sido reportados hasta la fecha en Centroamérica. El género Interocoris (Laccocorinae) es monotípico y anteriormente sólo se había registrado en México. Objetivo: Reportar el primer registro confirmado de I. mexicanus para Costa Rica y Centroamérica, así como proporcionar descripciones complementarias de los adultos, ninfa V y microhábitat asociado. Métodos: Se realizó una comparación de la morfología externa (medidas y proporciones) de los ejemplares recolectados en dos localidades de Costa Rica con la información y el material tipo de I. mexicanus, recolectado en México. Resultados: A partir de la comparación morfológica se obtuvo una identificación positiva de la especie, por lo que se reporta por primera vez a I. mexicanus de Costa Rica y Centroamérica. Los especímenes recolectados coincidieron en general con las mediciones y relaciones del material tipo de I. mexicanus, con ligeras diferencias, algunas de ellas incluso reportadas para los ejemplares de la serie tipo en la descripción original. Se presentan descripciones complementarias de adultos y se describe por primera vez la morfología de la ninfa V. Conclusiones: Con este nuevo registro se expande significativamente el rango del género Interocoris, así como de la especie I. mexicanus desde México a Costa Rica. Además, se aumentan a seis los géneros de Naucoridae en Costa Rica y a siete en Centroamérica.

Introduction: The family Naucoridae, of worldwide distribution, is divided into five subfamilies, with four of them and six genera reported to date in Central America. The genus Interocoris (Laccocorinae) is monotypic and was only recorded from Mexico. Objective: To report the first confirmed record of Interocoris mexicanus from Costa Rica and Central America, and to provide complementary descriptions of adults and nymphal instar V and associated microhabitat. Methods: A comparison of the external morphology (measurements and proportions) was made of specimens collected from two localities in Costa Rica with the type material of I. mexicanus from Mexico. Results: A positive identification of the species was obtained from the morphological comparison, which is why it is reported for the first time from Costa Rica and Central America. The specimens collected generally coincided with the measurements and relationships of the type material of I. mexicanus, with slight differences, some of them even reported for the specimens of the type series in the original description. Complementary descriptions of adults are presented and the morphology of nymph V is described for the first time. Conclusions: With this new record, the range of the genus Interocoris as well as the species I. mexicanus is expanded significantly from Mexico to Costa Rica. In addition, the reported number of genera of Naucoridae is increased to six in Costa Rica and to seven in the Central American region.

Descriptions of the larvae of Acanthagrion speculum and A. trilobatum from Costa Rica (Odonata: Coenagrionidae).

Description of the final instar of Acanthagrion trilobatum Leonard, 1977 and A. speculum Garrison, 1985 is based on associated specimens from San José, Turrialba and Sarapiquí Provinces, Costa Rica. Illustrations of these two species and a comparative table summarizing the main features of all larvae of Acanthagrion described to date are provided. The larva of A. trilobatum is distinguished from that of A. speculum by shorter lateral caudal lamellae (length 7 mm vs. 8.2 mm), lateral carina of abdominal segments 2-8 with spiniform setae on posterior 1/3 (lateral carinae of only S6-8 with spiniform setae in A. speculum), and male gonapophyses incurved (straight in A. speculum).

La colección de Entomología Acuática del Museo de Zoología, Universidad de Costa Rica: lista actualizada de géneros, importancia y retos futuros

Los macroinvertebrados acuáticos, y en especial los insectos, son el grupo de organismos más utilizado para determinar el estado de conservación de los ecosistemas acuáticos en estudios de calidad del agua y biomonitoreo acuático. La colección científica más importante de este grupo en el país se encuentra en el Museo de Zoología de la Universidad de Costa Rica y contiene material proveniente tanto de proyectos de investigación, tesis y trabajos de estudiantes como muestras recolectadas durante estudios y monitoreos ambientales realizados por consultores y diversas instituciones. En este trabajo se presenta un listado actualizado del material depositado, el cual incluye 98 familias y 341 taxones identificados (géneros, tribus o subfamilias) de once órdenes de insectos, siendo Coleoptera y Diptera los órdenes de mayor riqueza taxonómica. Se citan los trabajos que se han generado a partir de revisiones de la colección y los cuales incluyen registros nuevos de especies, géneros y de una familia para el país, así como las descripciones de especies nuevas y asociaciones de estadios inmaduros con sus adultos. Los principales desafíos para esta colección incluyen la identificación taxonómica de ciertos grupos, así como mantenerse al día con el constante crecimiento de la colección y la actualización de su base de datos.

Aquatic macroinvertebrates, and especially insects, are the group of organisms most commonly used to determine the health of ecosystems in water quality studies and freshwater biomonitoring. The most important scientific collection of this group in Costa Rica is located in the Zoological Museum of the University of Costa Rica (MZUCR) and includes material from scientific research, thesis and student projects, as well as samples from environmental studies and aquatic monitoring by consultants and institutions. In this work, an updated list of the collection's material is presented, which includes 98 families and 341 identified taxa (genera, tribes or subfamilies) from eleven insect orders, with Coleoptera and Diptera as the most taxonomical diverse orders. Studies which resulted from revisions of the collection material are cited, including new species, genera, and family records, as well as descriptions of new species and associations of immature stages with their adults. The main challenges for this collection include the taxonomic identification of certain groups, keeping up with the constant collection growth and updating the associated database.

The water striders (Hemiptera: Heteroptera: Gerridae) of Costa Rica: new species, checklist, and new records.

Brachymetra bernaldi Cordeiro, sp. nov. (Hemiptera: Heteroptera: Gerridae) from Heredia, Costa Rica, is herein described, illustrated, and compared with congeners. The new species resembles B. albinervus (Amyot Serville, 1843), but can be separated from it by the weak median carina of the pronotum, male abdominal mediotergite I with weak lateral notches, male abdominal mediotergite VII quadrate, male abdominal segment VIII in natural position almost entirely inserted into the abdominal cavity, and paramere narrow, with acute apex. We also provide the first checklist of the Gerridae of Costa Rica and new records, based on collection material and field sampling. All totaled, 31 species representing 13 genera and six subfamilies are recorded from the country. Five species and the genera Brachymetra Mayr, 1865 and Neogerris Matsumura, 1913 are registered for the first time from Costa Rica, and new provincial records are presented for 15 other species.

Description of the larva and pupa of Limnephilus hamifer Flint 1963 (Trichoptera, Limnephilidae) from Costa Rica.

The larva and pupa of Limnephilus hamifer Flint 1963 are described and illustrated for the first time. The description is based on material collected and reared from the Cerro de la Muerte mountain range in Costa Rica, and from additional specimens deposited at the Zoological Museum of the University of Costa Rica. The distribution of this species is restricted to high mountain areas of Costa Rica and Panamá and constitutes the most southern distribution of the genus on the American continent.

A new species of Anacroneuria Klapálek 1909 (Plecoptera: Perlidae) and notes on the altitudinal distribution of the genus in Costa Rica.

Anacroneuria is the most widespread genus of Perlidae throughout the Neotropical region and 30 species have been reported from Costa Rica. In this paper, we describe and illustrate a new species from a high elevation cloud forest, A. quetzali sp.n., increasing to 31 the number of described species for Costa Rica. In addition, we examine the altitudinal distribution of Anacroneuria in Costa Rica to determine possible patterns, using the data available on its altitudinal range (10-2700 masl). We divided the elevational range in seven categories, using 500 m intervals. We found that most species (90.3%) are distributed in elevations that range from 500 to 1500 masl, followed by low-elevations (35.5%). Interestingly, despite the fact that Plecoptera are known to inhabit clean, fast flowing water at high elevations, only 16.1% of the species have been found at high elevations in Costa Rica (above 2000 masl). Thus, it seems that most Anacroneuria species are distributed in middle elevations, which are the areas that have a high diversity of freshwater habitats.

Two new species of Rhagovelia (Hemiptera: Heteroptera: Veliidae) from Costa Rica, with a key and new records from the country.

Rhagovelia danpolhemi sp. nov., from the Caribbean Slope of Costa Rica and R. springerae sp. nov., from the northern portion of the country, are described, illustrated, compared with similar species, and included in a key to species recorded from the country. Rhagovelia calopa Drake & Harris, R. spinosa Gould, and R. tantilla Drake & Harris are recorded for the first time from Costa Rica. New provincial records are provided for R. acuminata Bacon, R. angustipes Uhler, R. armata (Burmeister), R. bisignata Bacon, R. crassipes Champion, R. elegans Uhler, R. femoralis Champion, R. solida Bacon, R. spinigera Champion, R. tenuipes Champion, and R. uncinata Champion. Additional distributional information is given for these species and for R. formosa Bacon and R. scabra Bacon.

New species of Potamocoris Hungerford (Heteroptera, Potamocoridae) from Costa Rica and a key to the species .

A new potamocorid species, Potamocoris sitesi NEW SPECIES, with its two wing morphs (coleopteroid and macropterous) are described from Costa Rica.  Descriptions are supported with photographs and illustrations. Parameres become progressively narrower, ending in a sharp needle-like point. This is the third species of Potamocoris known from Central America. A key to the species of the genus is provided.

Downstream effects of hydropower production on aquatic macroinvertebrate assemblages in two rivers in Costa Rica.

Despite the fact that little is known about the consequences of hydropower production in tropical areas, many large dams (> 15 m high) are currently under construction or consideration in the tropics. We researched the effects of large hydroelectric dams on aquatic macroinvertebrate assemblages in two Costa Rican rivers. We measured physicochemical characteristics and sampled aquatic macroinvertebrates from March 2003 to March 2004 in two dammed rivers, Peñas Blancas and San Lorenzo, as well as in the undammed Chachagua River. Sites above and below the dam had differences in their physicochemical variables, with wide variation and extreme values in variables measured below the dam in the San Lorenzo River. Sites below the dams had reduced water discharges, velocities, and depths when compared with sites above the dams, as well as higher temperatures and conductivity. Sites above dams were dominated by collector-gatherer-scrapers and habitat groups dominated by swimmer-clingers, while sites below dams had a more even representation of groups. In contrast, a comparison between two sites at different elevation in the undammed river maintained a similar assemblage composition. Tributaries might facilitate macroinvertebrate recovery above the turbine house, but the assemblage below the turbine house resembled the one below the dam. A massive sediment release event from the dam decreased the abundance per sample and macroinvertebrate taxa below the dam in the Peñas Blancas River. Our study illustrates the effects of hydropower production on neotropical rivers, highlighting the importance of using multiple measures of macroinvertebrate assemblage structure for assessing this type of environmental impact.

[Effect of sampling effort on taxa richness of aquatic macroinvertebrates and the BMWP/Atitlán index]. / Efecto del esfuerzo de muestreo en la riqueza de táxones de macroinvertebrados acuáticos y el índice BMWP/Atitlán.

Aquatic macroinvertebrates are the group of organisms most commonly used to determine ecosystem health in water quality studies and freshwater biomonitoring. Nevertheless, the methods and collecting time of biomonitoring have not yet been sufficiently adapted and tested in tropical aquatic environments. Twelve rivers in the Lago de Atitlán watershed in Guatemala were assessed with different collecting times, during the dry season. The method involved the collection of organic and inorganic material including benthic organisms, from different microhabitats, for a pre-established time period (5, 10, 15 min) with a D-frame net. Samples were preserved with 95% ethanol in the field, and sorted in the laboratory. As expected, the analysis showed that the abundance and taxonomic richness was higher with increasing sampling effort. The water quality categories obtained from the newly proposed BMWP/Atitlán index varied among sampling times. However, the Kruskal-Wallis test showed no significant differences between the categories obtained with the index and the number of taxa collected at 10 and 15 min. Therefore, we recommend a reduction of sample time, but maintaining the tree subsamples in order to include most variety of microhabitats and assure a representative sample of the aquatic macroinvertebrates.

Downstream effects of hydropower production on aquatic macroinvertebrate assemblages in two rivers in Costa Rica

Despite the fact that little is known about the consequences of hydropower production in tropical areas, many large dams (>15m high) are currently under construction or consideration in the tropics. We researched the effects of large hydroelectric dams on aquatic macroinvertebrate assemblages in two Costa Rican rivers. We measured physicochemical characteristics and sampled aquatic macroinvertebrates from March 2003 to March 2004 in two dammed rivers, Peñas Blancas and San Lorenzo, as well as in the undammed Chachagua River. Sites above and below the dam had differences in their physicochemical variables, with wide variation and extreme values in variables measured below the dam in the San Lorenzo River. Sites below the dams had reduced water discharges, velocities, and depths when compared with sites above the dams, as well as higher temperatures and conductivity. Sites above dams were dominated by collector-gatherer-scrapers and habitat groups dominated by swimmer-clingers, while sites below dams had a more even representation of groups. In contrast, a comparison between two sites at different elevation in the undammed river maintained a similar assemblage composition. Tributaries might facilitate macroinvertebrate recovery above the turbine house, but the assemblage below the turbine house resembled the one below the dam. A massive sediment release event from the dam decreased the abundance per sample and macroinvertebrate taxa below the dam in the Peñas Blancas River. Our study illustrates the effects of hydropower production on neotropical rivers, highlighting the importance of using multiple measures of macroinvertebrate assemblage structure for assessing this type of environmental impact. Rev. Biol. Trop. 62 (Suppl. 2): 179-201. Epub 2014 April 01.

Existe poca información publicada sobre el efecto de grandes represas hidroeléctricas (>15m alto) en ríos tropicales. Investigamos los efectos de estas represas en las comunidades de macroinvertebrados acuáticos en dos ríos de Costa Rica. Medimos características físico-químicas y recolectamos macroinvertebrados a lo largo del año en dos ríos represados, Peñas Blancas y San Lorenzo, así como en el río Chachagua, el cual no era utilizado para la producción hidroeléctrica. Los sitios arriba y debajo de las represas presentaron diferencias físico-químicas, con amplia variación y valores extremos en las variables medidas debajo de la represa en el Río San Lorenzo. Los sitios arriba de las represas estaban dominados por colectores-recolectores-raspadores y nadadores-colgadores, mientras que debajo de las represas hubo una representación más equitativa de grupos funcionales. En contraste, las comunidades fueron semejantes en dos sitios a diferente elevación en el río sin represa. La presencia de afluentes podría haber facilitado la recuperación de macroinvertebrados arriba de la casa de máquinas, pero las comunidades fueron similares bajo la casa y abajo de la represa. Una liberación masiva de sedimentos disminuyó la abundancia y el número de táxones bajo la represa en el Río Peñas Blancas.

Efecto del esfuerzo de muestreo en la riqueza de táxones de macroinvertebrados acuáticos y el índice BMWP/Atitlán

Effect of sampling effort on taxa richness of aquatic macroinvertebrates and the BMWP/Atitlán index. Aquatic macroinvertebrates are the group of organisms most commonly used to determine ecosystem health in water quality studies and freshwater biomonitoring. Nevertheless, the methods and collecting time of biomonitoring have not yet been sufficiently adapted and tested in tropical aquatic environments. Twelve rivers in the Lago de Atitlán watershed in Guatemala were assessed with different collecting times, during the dry season. The method involved the collection of organic and inorganic material including benthic organisms, from different microhabitats, for a pre-established time period (5, 10, 15min) with a D-frame net. Samples were preserved with 95% ethanol in the field, and sorted in the laboratory. As expected, the analysis showed that the abundance and taxonomic richness was higher with increasing sampling effort. The water quality categories obtained from the newly proposed BMWP/Atitlán index varied among sampling times. However, the Kruskal-Wallis test showed no significant differences between the categories obtained with the index and the number of taxa collected at 10 and 15min. Therefore, we recommend a reduction of sample time, but maintaining the tree subsamples in order to include most variety of microhabitats and assure a representative sample of the aquatic macroinvertebrates. Rev. Biol. Trop. 62 (Suppl. 2): 291-301. Epub 2014 April 01.

Los macroinvertebrados son los organismos más utilizados para determinar el estado de salud de los ecosistemas en estudios de calidad del agua y biomonitoreo acuático. No obstante, los métodos para monitoreo y tiempos de recolecta no han sido efectivamente adaptados a ambientes acuáticos tropicales. En la cuenca del Lago de Atitlán, Guatemala, se evaluaron 12 ríos con diferentes tiempos de recolecta, durante la temporada seca. El método consistió en la recolecta de material orgánico e inorgánico incluyendo organismos bénticos, en diferentes microhabitats, por un periodo de tiempo (5, 10, 15min) con una red “D” y preservados en etanol al 95%; la separación y clasificación se realizó posteriormente en el laboratorio. Como se esperaba, los análisis de datos revelaron que la abundancia y riqueza de taza es mayor al incrementar el esfuerzo de muestreo. Las categorías de calidad del agua obtenidas del cálculo del índice biótico BMWP/Atitlán variaron con el esfuerzo de muestreo. Sin embargo, el análisis de Kruskall-Wallis no mostró diferencias significativas entre las categorías obtenidas con el índice y el número de táxones recolectados en los 10 y 15min. Por lo tanto, recomendamos que el tiempo mínimo de recolecta puede ser de 10 minutos, siempre y cuando se mantenga el mismo número de submuestras (tres) para que se incluya la mayor variedad posible de micro-hábitats durante el muestreo.

[Freshwater macroinvertebrates from Cocos Island, Costa Rica: species and comparison with other islands of the Eastern Tropical Pacific]. / Macroinvertebrados dulceacuícolas de la Isla del Coco, Costa Rica: especies y comparación con otras islas del Pacifico Tropical Oriental.

Freshwater macroinvertebrates from Cocos Island, Costa Rica: species and comparison with other islands of the Eastern Tropical Pacific. Cocos Island is an oceanic island in the Eastern Pacific, at 496km from Cabo Blanco, Costa Rica. This 24 km2 island is surrounded by a protected marine area of 9640 km2. it was declared National Park in 1978 and a World Heritage by UNESCO in 1997. Freshwater macroinvertebrate fauna was collected in 20 sites covering three rivers (Genio, Chatam and Sucio) and two creeks (Minuto and an unnamed creek behind the park rangers' house). Tank bromeliads or phytotelmata were also examined for aquatic macroinvertebrates. Physicochemical parameters were determined in 13 study sites. Additionally, a comparison with other islands in the Eastern Tropical Pacific was conducted to determine the most important factors controlling the diversity in Tropical Pacific islands. A total of 455 individuals were collected belonging to 20 taxa (mostly identified to genus level) from 15 families of aquatic insects. Other macroinvertebrates such as Palaemonid shrimps, Hidrachnida and Oligochaeta were also collected. The family Staphylinidae (Coleoptera) was the most abundant, followed by Chironomidae (Diptera). Diptera was the order of insects with the highest taxonomic richness. A relationship between distance and the number of families was observed supporting the premises of the Theory of island Biogeography. This relationship was improved by correcting area by island elevation, indicating that mountainous islands had the richest faunas, potentially due to high cloud interception that feeds freshwater environments favoring the establishment of aquatic fauna. Physicochemical variables were similar in all sites, possibly due to the geology and the absence of significant sources of pollution on the island.

Macroinvertebrados dulceacuícolas de la Isla del Coco, Costa Rica: especies y comparación con otras islas del Pacífico Tropical Oriental / Freshwater macroinvertebrates from Cocos Island, Costa Rica: species and comparison with other islands of the Eastern Tropical Pacific

Cocos Island is an oceanic island in the Eastern Pacific, at 496km from Cabo Blanco, Costa Rica. This 24km² island is surrounded by a protected marine area of 9 640km². It was declared National Park in 1978 and a World Heritage by UNESCO in 1997. Freshwater macroinvertebrate fauna was collected in 20 sites covering three rivers (Genio, Chatam and Sucio) and two creeks (Minuto and an unnamed creek behind the park rangers’ house). Tank bromeliads or phytotelmata were also examined for aquatic macroinvertebrates. Physicochemical parameters were determined in 13 study sites. Additionally, a comparison with other islands in the Eastern Tropical Pacific was conducted to determine the most important factors controlling the diversity in Tropical Pacific islands. A total of 455 individuals were collected belonging to 20 taxa (mostly identified to genus level) from 15 families of aquatic insects. Other macroinvertebrates such as Palaemonid shrimps, Hidrachnida and Oligochaeta were also collected. The family Staphylinidae (Coleoptera) was the most abundant, followed by Chironomidae (Diptera). Diptera was the order of insects with the highest taxonomic richness. A relationship between distance and the number of families was observed supporting the premises of the Theory of island Biogeography. This relationship was improved by correcting area by island elevation, indicating that mountainous islands had the richest faunas, potentially due to high cloud interception that feeds freshwater environments favoring the establishment of aquatic fauna. Physicochemical variables were similar in all sites, possibly due to the geology and the absence of significant sources of pollution on the island.

La Isla del Coco es una isla oceánica localizada en el Pacífico Tropical Oriental a unos 492km de Cabo Blanco. La isla cuenta con un área terrestre de 24km² y un área marina protegida de 9 640km². Fue declarada Parque Nacional en 1978 y Patrimonio de la Humanidad por la UNESCO en 1997. Se realizó una gira de recolecta del 22 de mayo al 12 junio 2008. Se recolectaron macroinvertebrados acuáticos en 20 tramos de tres ríos (Genio, Chatham y Sucio) y dos quebradas (Minuto y quebrada sin nombre atrás de estación de guarda parques). En 13 sitios se toma- ron parámetros fisicoquímicos. En total se recolectaron 455 individuos de 20 táxones de 15 familias de insectos acuáticos y otros macroinvertebrados. La familia Staphylinidae presentó la mayor abundancia seguida por Chironomidae, los dípteros fueron el orden con mayor riqueza taxonómica. Una relación entre distancia y número de familias se observó apoyando en parte la Teoría de Biogeografía de Islas. La relación mejoró al corregir área con elevación, indicando que islas montañosas tenían alta riqueza, posiblemente debido a la mayor intercepción de nubes que alimentan los ambientes dulceacuícolas que favorecen el establecimiento de la fauna acuática. Las variables ambientales fueron similares en todos los sitios.

[Fresh water macroinvertebrates of Costa Rica I]. / Macroinvertebrados de agua dulce de Costa Rica I.

This is the first in a series of three volumes on the freshwater macroinvertebrates of Costa Rica. The present volume includes an introductory chapter summarizing the major types of freshwater environments, the biology of freshwater macroinvertebrates (habitats, food, respiration, osmoregulation, etc.), ecological and economic importance, conservation and a synopis of the major groups, followed by a simplified key. The next two chapters discuss collecting methods and biomonitoring. These are followed by chapters on mayflies (Ephemeroptera: 10 families), dragonflies (Odonata: 13 families), stoneflies (Plecoptera: 1 family) and caddisflies (Trichoptera: 15 families). Both in this volume and in those to follow, the chapters treating individual taxa include a summary of the natural history, importance, taxonomy, collecting methods, morphology and an illustrated key to the families; each family is discussed separately and an illustrated key to genera is provided; each chapter ends with a bibliography and a table listing all the genera with information on number of species, distribution, habitat and tolerance to water pollution. While the emphasis is on families and genera known from Costa Rica, additional taxa occurring elsewhere in Central America are mentioned. The present volume also includes numerous color plates of aquatic macroinvertebrates.