Resumo As espécies simpátricas de caranguejo-da-lama Panopeus americanus e Panopeus austrobesus são encontradas em ambientes entremarés associados a habitats lamacentos e rochosos, bem como em simpatria na costa do Atlântico Ocidental. Portanto, constituem um sistema modelo adequado para ser utilizado em estudos focados na investigação de aspectos de coexistência biológica entre espécies semelhantes, como estrutura populacional e habitat. Os objetivos do presente estudo são descrever e comparar a microdistribuição de duas espécies simpátricas de caranguejo-da-lama – P. americanus e P. austrobesus – com base na avaliação de sua distribuição espacial e temporal, em uma área estuarina complexa e com baixo impacto antrópico. A hipótese de que estas duas espécies apresentam microdistribuição semelhante, embora uma espécie seja mais abundante que a outra, foi testada. A amostragem foi realizada na zona entremarés de uma área específica do complexo estuarino de Cananeia, Estado de São Paulo, Sudeste do Brasil, em diferentes períodos durante dois anos. Ambas as espécies apresentaram microdistribuição e frequência semelhantes, principalmente nas zonas entremarés média e alta. Entretanto, Panopeus americanus foi mais abundante e apresentou menor tamanho médio em todas as zonas amostrais. A pronunciada disparidade de tamanho entre as espécies sugere preferências alimentares divergentes, potencialmente relacionadas ao tamanho das presas possibilitando a coexistência dessas espécies simpátricas. A predominância dessas duas espécies nas zonas intermareais superiores também indica uma estratégia para evitar a competição com os camarões alfeídeos. caranguejodalama caranguejo da lama rochosos Ocidental Portanto semelhantes habitat P temporal antrópico semelhante outra testada Cananeia Paulo Brasil anos alta Entretanto amostrais divergentes alfeídeos

Abstract Sympatric mud crab species Panopeus americanus and Panopeus austrobesus are found in intertidal environments associated with muddy and rocky habitats in the Western Atlantic coast. Therefore, they are a suitable model system to be used in studies focused on investigating biological coexistence aspects between close species, such as population structure and habitat. The aims of the current study are to describe and compare the distribution of two sympatric mud crab species – P. americanus and P. austrobesus – based on their spatial and temporal distribution, in a low human impact estuarine complex area. The hypothesis that these two species show similar distribution, although one species is more abundant than the other, was herein tested. Sampling was carried out in the intertidal zone of a specific area in Cananeia estuarine complex, São Paulo State, Southeastern Brazil, in different periods of time for two years. Both species presented similar pattern distribution and frequency, with predominance in the middle and high intertidal zones, including all demographic categories. However, Panopeus americanus was more abundant and presented smaller mean size in all sampling zones. The pronounced disparity in size between the species suggests divergent dietary preferences, potentially related to prey size allowing the coexistence of these sympatric and syntopic species. The predominance of these two species in the upper intertidal zones was understood as a strategy for avoiding competition with the intertidal alpheid shrimps. coast Therefore habitat P other tested State Brazil years frequency categories However preferences shrimps

Abstract We provide morphological and genetic evidence to establish the presence/occurrence of Alpheus angulosus, Alpheus buckupi, and Axianassa australis on the coast of Maranhão, Brazil. The specimens were collected in December 2019 by actively searching the estuaries and rocky shores of São Luís Island, northeast of Brazil. In addition to morphological analyses, two mitochondrial genes were obtained (Cytochrome C Oxidase I and 16S), and a phylogenetic analysis was conducted to verify the specimens’ identity. Accurate identification is an essential tool to obtain reliable information about the occurrence of the species and thus help assess biodiversity in a highly diverse region. These finding also serve to stimulate future studies in poorly studied areas as well as set a baseline for biodiversity conservation and preservation strategies. presenceoccurrence presence angulosus buckupi Maranhão Brazil 201 Island analyses Cytochrome 16S, 16S S , 16S) identity region strategies 20 2

Resumen Este estudio representa un esfuerzo sin precedentes para evaluar la diversidad de los decápodos Brachyura y Anomura del infralitoral rocoso del Parque Estatal Marino Laje de Santos, un área preservada y protegida localizada en la costa sureste de Brasil. Las muestras se tomaron trimestralmente durante 1 año con la combinación de sustrato de refugio artificial para captura pasiva y buceo autónomo para captura activa. Se determinaron un total de 987 individuos distribuidos en 32 especies, 22 géneros y 11 familias. Presentamos un reporte taxonómico de las especies y se discuten sus registros de distribución. El ermitaño Pagurus brevidactylus y el cangrejo Mithraculus forceps fueron las especies más abundantes de Anomura y Brachyura, respectivamente. Como se esperaba, la combinación de los métodos de muestreo mostró un valor más alto del índice de diversidad de Shannon (H = 5.7) que los métodos individuales de captura pasiva (H = 5.6) y captura activa (H = 4.4). Este estudio provee el primer reporte de crustáceos decápodos para el parque, por lo tanto, puede ser usado como línea base para programas de monitoreo de fauna local y en los planes de conservación.

Abstract This study represents an unprecedented effort to assess the diversity of rocky infralittoral decapods Brachyura and Anomura from the Marine State Park of Laje de Santos, a preserved and protected area located in the southeastern Brazilian coast. Sampling was carried out quarterly for 1 year, using the combination of artificial refuge substrate (ARS) for the passive capture of specimens, and SCUBA diving for active capture. A total of 987 individuals distributed into 32 species, 22 genera, and 11 families were determined. We present a taxonomic account of the species and their distribution records are discussed. The hermit crab Pagurus brevidactylus and the crab Mithraculus forceps were the most common species of Anomura and Brachyura, respectively. As expected, the combination of the sampling methodologies showed a higher Shannon diversity index value (H = 5.7), than the individual methods of ARS (H = 5.6) and active capture (H = 4.4). This study provides the first record of decapod crustaceans for the park, therefore it can be used as a baseline for local fauna monitoring programs and conservation planning.

Abstract Potimirim is one of the 40 genera of Atyidae restricted to America, which occurs in coastal freshwater habitats and questions about population status and variability have been emerging. Potimirim brasiliana occurs in Brazil from the northeastern to southeastern region. In order to evaluate the hypothesis of genetic structure among populations, we performed molecular analyses with specimens from all known limit of distribution of the species. The molecular markers used were COI and 28S. Phylogenetic trees were obtained by maximum likelihood and Bayesian analyses, and a haplotype network was obtained based only on COI. We found clear separation between P. brasiliana, P. potimirim, P. glabra and Potimirim sp 2. No pattern of structuration was found among P. brasiliana, but the haplotype network showed geographic pattern of structuration for the congener P. potimirim. The lack of genetic structuration among P. brasiliana can be explained by its life cycle that requires brackish water to complete their larval development. The larvae and juvenile in contact with these habitats can spread through oceanic currents, especially in higher rainfall seasons, maintaining the gene flow. The explanation for the geographical pattern found among P. potimirim is still missing and aspects about its lifecycle and larval development should be investigated.

Abstract Here, we report the first occurrence of Trizocarcinus Rathbun, 1914 (Brachyura: Euryplacidae) from the South Atlantic (Brazil). Trizocarcinus tacitus Chace, 1940 was collected in the upper continental slope of the Potiguar Basin, northeastern Brazil. The new record expands by 3000 km the southern distribution of the species in the Western Atlantic.

Biodiversity and spatial-temporal distribution of hermit crabs captured as bycatch in the non-selective fishery of shrimp were analyzed in this study from July 2010 through June 2011 off coast Santa Catarina State (southern Brazil). Ecological indexes and redundancy analyses were conducted to understand the hermit community and their relationship with environmental factors. In total, 644 specimens were collected, representing two families, five genera, and six species, demonstrating remarkable species richness in the study area, mainly because Santa Catarina is a subtropical region. Isocheles sawayai showed the highest abundance, followed by Loxopagurus loxochelis. Both species demonstrated correlation with temperature (positive) and sediment grain size (negative). The highest richness and evenness values were estimated at the deeper area (17 m). However, in 5 m deep area showed the lowest evenness because of the high dominance of I. sawayai, resulting in a lower estimated diversity. During a period of lower temperature and higher salinity (July), higher levels of diversity were registered, probably because of the lower dominance of tropical species (I. sawayai) and the presence of some species distributed in offshore regions (Petrochirus diogenes, Dardanus insignis and Pagurus exilis). Thus, we detected that the capture effort designated in the shrimp fishery activities had a strong influence in the diversity of hermit crabs and other associated fauna, especially because of catch specimens in expressive abundance at various stages of development, including juveniles. This profile makes us argue in favor of constant monitoring of bycatch resources in order to preserve the marine fauna.

Se analizó la biodiversidad y distribución espacio-temporal de los cangrejos ermitaños, como descartes en la pesca no selectiva de camarón, entre julio de 2010 y junio de 2011 en la costa del Estado de Santa Catarina. Los índices ecológicos y análisis de redundancia se analizaron para describir el desarrollo de la comunidad de ermitaños y su relación con los factores ambientales. Se encontró una notable riqueza específica en una región subtropical, como fue la de Santa Catarina, donde se obtuvieron 644 individuos pertenecientes a dos familias, cinco géneros y seis especies. Isocheles sawayai presentó la mayor abundancia, seguida de Loxopagurus loxochelis; ambas especies mostraron correlación con la temperatura y tamaño de las partículas del sedimento. Los mayores valores de riqueza y uniformidad se dieron en la zona más profunda estudiada (17 m). Sin embargo, a 5 m de profundidad se encontró la equirepartición más baja debido al predominio de I. sawayai. Durante un período de baja temperatura y mayor salinidad (julio) se registraron altos valores de diversidad, probablemente debido la baja dominancia de especies costeras tropicales (I. sawayai) y presencia de algunas especies de aguas oceánicas (Petrochirus diogenes, Dardanos insignis y Pagurus exilis). Se detectó que el esfuerzo de captura aplicado en las pesca del camarón tuvo una fuerte influencia en la diversidad de los cangrejos ermitaños y fauna asociada, especialmente debido a que en las muestras se observaron diversas etapas de desarrollo de las especies, incluyendo juveniles. Estos resultados son argumentos a favor de una vigilancia constante de los descartes a fin de preservar la fauna marina.

Abstract The aim of this study was to characterize the pattern of gastropod shell occupation in the field and selection of shell size and type under laboratory conditions by the hermit crab Pagurus criniticornis (Dana, 1852), inhabiting the infralittoral area of Anchieta Island, São Paulo, Brazil. Hermit crabs were obtained monthly during 1999 by SCUBA diving. For experiments under laboratory conditions, samplings were performed in 2002. The hermit crabs occupied 16 species of gastropods shells. Cerithium atratum (Born, 1778) was the most occupied shell (89.31%), followed by Morula nodulosa (4.73%) (Adams, 1845). No difference was observed in the pattern of occupation between males and females. The equations that best demonstrated the relationship between hermit crabs and their shells were those that involved Shell Wet Weight (SWW) and Shell Internal Volume (SIV). The laboratory experiments were in accordance to the pattern of occupation observed in the field; the mean value of SAI (Shell Adequacy Index) recorded to the population studied was 1.13 with a trend to increase this value in the last size classes. The results obtained corroborate with the hypothesis of the occupation process of shells governed not only by availability of shells, but also by its architecture. In addition, the shell stock in the area is one another important condition related to the exhibited pattern of shell occupation by P. criniticornis, and allows the stable coexistence among the island assemblage. The pattern of occupation observed promotes a high reproductive profile for the population studied, maximizing the populational growth.

Abstract We designed 14 new primers for amplification of the COI barcode region of decapod crustacean species. We tested, with high level of success, the generation of ~ 640 ± 49 base-pair sequences in selected groups of decapods (hermit crabs, squat lobsters, marine and freshwater crabs and shrimps), encompassing representatives of 27 genera of 15 families, 11 of Pleocyemata (Anomura, Brachyura, and Caridea) and 4 of Dendrobranchiata. Based on the results we expect the applicability of these primers for several studies with different taxa within Decapoda.

ResumoDecápodes desenvolveram uma ampla variedade de estratégias reprodutivas. Neste estudo foram investigadas características reprodutivas da espécie de PalaemonidaeLeander paulensis. Os indivíduos foram coletados na região costeira de Ubatuba, São Paulo, Brasil. Foram examinadas 46 fêmeas ovígeras quanto aos seguintes aspectos reprodutivos: fecundidade, investimento reprodutivo, perda de ovos e volume dos ovos. Leander paulensis produz uma grande quantidade de pequenos ovos, com fecundidade média de 635 ± 246 ovos. O volume dos ovos aumentou significativamente quando comparado o estágio inicial (0.034 ± 0.008 mm3) com o estágio final de desenvolvimento (0.05 ± correlação com o tamanho das fêmeas. Fêmeas com ovos no estágio 2 apresentaram massa corpórea seca significativamente maior que aquelas carregando ovos no estágio inicial. Esse aumento de massa parece ser decorrente da recuperação de reservas energéticas das fêmeas, que teriam sido utilizadas durante a produção de ovos. Além disso, deve-se considerar neste tipo de avaliação o aumento da massa corpórea em relação ao investimento reprodutivo, assim como da perda de ovos relacionada à massa das fêmeas ou qualquer outra variável dependente do peso.

AbstractDecapod species have evolved with a variety of reproductive strategies. In this study reproductive features of the palaemonid shrimp Leander paulensiswere investigated. Individuals were collected in the coastal region of Ubatuba, São Paulo, Brazil. In all, 46 ovigerous females were examined in terms of the following reproductive traits: fecundity, reproductive output, brood loss and egg volume. Leander paulensis produces a large number of small eggs with an average fecundity of 635 ± 246 eggs. Egg volume increased significantly from early (0.034 ± 0.008 mm3) to late development stage (0.05 ± 0.012 mm3). The reproductive output did not correlate with female size. The weight of females bearing stage 2 eggs was significantly higher than that of females carrying stage 1 eggs. We assume that the reason for this weight gain is the recovery of female reserves that have been depleted for egg production. Moreover, we emphasize that this weight gain must be considered when evaluating weight-dependent variables such as reproductive output or brood loss in relation to female weight. Otherwise, an overestimation of these variables might lead to inaccurate results.

Differences on reproductive performance between two sampling points of the porcelain crab Pachycheles monilifer from Ubatuba (São Paulo, Brazil), one from Itaguá Beach (living on Schizoporella errata) and the other from Grande Beach (living on Phragmatopoma caudata) has been previously observed. Therefore could be expected a specific behavior in substrate preference to optimize the best biogenic habitat. Considering this premise, our goal was to test the substrate preference of this species when both substrates were simultaneously available. In total, 185 individuals were collected in these same localities and they were submitted to substrate selection experiments. The trials were conducted on containers with quiet seawater at 28 ± 1°C and under dark photoperiod. Specimens were exposed to substrates by 30 min. Trials started with the release of one animal per treatment in the middle of the opposite side to the substrate inside the containers. After the established time, the substrate preference of each porcelain crab was verified. As result, no preference pattern was found and the choices in the experiment were not significantly different from the expected. This lack of preferences may be an indication that porcelain crabs are generalists in habitat use regardless of sex of individuals and potential benefit in fitness. Therefore, the differences on the reproductive aspects of the P. monilifer probably are associated with environment factors not simulated in this study and may indicate the occurrence of plasticity in habitat selection behavior.

O gênero Callinectes Stimpson, 1860 atualmente é composto por 16 espécies, seis das quais são registradas para a costa brasileira. No presente estudo foi obtido o primeiro estagio de zoea deCallinectes bocourti, C. danae, C. exasperatus, C. ornatus e C. sapidus a partir de fêmeas ovigeras coletadas no Brasil. Os caracteres morfológicos e merísticos de todas estas larvas foram descritos e ilustrados. Para C. bocourti, C. danae e C. sapidus tais estruturas foram redescritas e comparadas com descrições previas, listando-se as diferenças. Os caracteres larvais destas espécies foram verificados em busca de diferenças interespecíficas, bem como os aspectos larvais para distinguir o gênero Callinectes dentro de Portunidae. Em complemento, foram feitas comparações com outros gêneros e espécies de portunídeos, cujo primeiro estágio de zoea é conhecido, com atenção especial para aquelas espécies presentes na mesma área geográfica. Nossos achados corroboram estudos moleculares prévios e discutimos tal complexidade dentro do grupo.

The genus Callinectes Stimpson, 1860 currently consists of 16 species, six of which are reported in Brazilian coast. In the present study, the first zoeal stages of Callinectes bocourti,C. danae, C. exasperatus, C. ornatus and C. sapidus from Brazil were obtained from ovigerous females. The morphological and meristic characters of all these larval stages are described and illustrated. Those of C. bocourti, C. danae and C. sapidus are redescribed and compared with the previous descriptions, and differences are listed. Larval characters of these species were examined for interspecific differences, as well as larval features to distinguish the genus Callinectes within Portunidae. In addition, other portunid genera and species with a known first zoeal stage are compared, with special attention to those species present in the same geographical area. Our findings concord with some previous molecular studies, and we discuss the complexity within the group.

Size structure within a population, relative growth of secondary sexual characters in both sexes, and fecundity of females were assessed from field samples of Microphrys bicornutus in the vicinity of Bocas del Toro, Caribbean Sea, Panama. The study was based upon 135 individuals captured by hand and a kick net. Carapace width ranged from 6.5 to 14.4 mm for ovigerous females, 4.2 to 16 mm for non-ovigerous females, and 5.9 to 17.4 mm for males. The relative growth of carapace length versus carapace width was isometric in males and negatively allometric in females. Relative growth of the chela length and abdomen width, compared to the carapace width, exhibited 2 phases, immature and mature, for males and females, respectively. The carapace widths at which 50% of males and females reached morphometric maturity were 13.6 and 8.5 mm, respectively. The mean value of the reproductive output was 3.6, the relative fecundity was 2041.91 eggs, and the relative size at the onset of sexual maturity was 0.4. As in most brachyuran species, the studied population of M. bicornutus showed a strong positive correlation between fecundity and body size. Differences in those parameters for previously studied populations from Venezuela, Jamaica and Brazil may be due to latitudinal or regional environmental effects.

Se estudió la estructura de la población, el crecimiento relativo de los caracteres sexuales secundarios de ambos sexos y la fecundidad de las hembras de Microphrys bicornutus de Bocas del Toro, Panamá. Se recolectó manualmente y con red un total de 135 individuos. Las hembras ovígeras midieron 6,5-14,4 mm de ancho de caparazón (AC), las no ovígeras 4,2-16 mm, y los machos 5,9-17,4 mm. El crecimiento relativo del largo del caparazón versus el ancho de caparazón fue isométrico en los machos y alométrico negativo en las hembras. El crecimiento relativo del largo de la quela y el ancho del abdomen respecto del ancho de caparazón mostró la presencia de 2 fases, madura e inmadura, para machos y hembras, respectivamente. La talla en la cual el 50% de los machos y las hembras alcanzaron la madurez morfométrica fue 13,6 y 8,5 mm, respectivamente. El valor medio del output reproductivo fue de 3,6, la fecundidad relativa de 2041,91, y la talla relativa de madurez sexual fue de 0,4. Como la mayoría de los cangrejos Brachyura, M. bicornutus mostró una fuerte correlación positiva entre la talla de la hembra y la fecundidad. Una comparación entre los parámetros reproductivos descriptos en el presente trabajo y los de las poblaciones de M. bicornutus en Venezuela, Jamaica y Brasil mostró algunas diferencias, por lo tanto, podría sugerirse que las mismas se deberían a efectos latitudinales o ambientales.

A recent taxonomic revision indicated that Macrobrachiumpotiuna, an endemic prawn in Brazilian freshwater drainages, exhibits wide morphological variability along its limited geographical distribution. However, in some cases, taxonomic doubts at the species level have no clear morphological resolution. Considering that no molecular data of M. potiuna along its distribution were available to provide a complete and integrated overview, we analyzed 21 partial sequences (531 bp) from the mitochondrial 16S rRNA gene of M. potiuna and 9 sequences from outgroup species, by maximum likelihood and parsimony, in order to investigate the possibility of the existence of cryptic species, within the morphologically based M. potiuna. The topologies obtained revealed that M. potiuna represents a monophyletic clade. Nevertheless, two clades supported by both analyses were formed within the M. potiuna taxon. The mean genetic divergence between these two groups was 0.044 ± 0.007, and within each group (i.e., M. potiuna "sensu stricto" andM. potiuna "Affinis-Clade") the divergences were 0.010 ± 0.003 and 0.028 ± 0.005, respectively. As far as we know, this is the first report to show a genetic separation between populations of prawns with abbreviated larval development in South American drainages. Pending additional analysis, to propose a conclusive inference, the existence of these distinct genetic groups must be considered in future studies with the morphologically based M. potiuna. In addition, we extended the known northern distribution with a record from the state of Bahia.

Una revisión taxonómica reciente reveló que el camarón endémico, Macrobrachium potiuna, distribuido en riachuelos brasileños, presenta una alta variabilidad morfológica a lo largo de su limitada distribución geográfica. Sin embargo, los problemas taxonómicos a nivel de especie no parecen tener clara resolución en algunos casos. Considerando que no hay datos moleculares disponibles de M. potiuna a lo largo de su distribución, que puedan proveer una visión general completa e integrada, se analizaron 21 secuencias parciales (531pb) del gen mitocondrial 16S, de M. potiuna y 9 secuencias del grupo externo, usando máxima verosimilitud y máxima parsimonia, para investigar la posibilidad de que exista una especie críptica dentro de M. potiuna. Las topologías obtenidas mostraron que M. potiuna es un grupo monofilético. Sin embargo, se formaron dos clados internos, bien soportados por ambos análisis. La divergencia genética promedio entre estos dos grupos fue de 0,044 ± 0,007; dentro de los clados (i.e., M. potiuna "sensu stricto" y M. potiuna "Affinis-Clade") las divergencias fueron de 0,010 ± 0,003 y 0,028 ± 0,005, respectivamente. Hasta donde se sabe, este es el primer estudio que muestra una separación entre las poblaciones de camarones de agua dulce de Sudamérica con desarrollo larval abreviado. En espera de un análisis más exhaustivo, que proponga una conclusión definitiva, la existencia de estos dos grupos genéticos distintos debe ser considerada en estudios futuros de M. potiuna, basados únicamente en morfología. De manera adicional, este trabajo incluye una extensión en la distribución norte de M. potiuna hasta el estado de Bahía.

The caridean freshwater shrimp Atya scabra is a common resident of stream systems of tropical rainforests in America, including Brazilian drainages. This shrimp has an amphidromous life cycle, which increases its vulnerability when facing habitat fragmentation. Since information on the reproduction of this species is still limited, we present here data on egg production, egg loss, and energy investment, to achieve a better understanding of reproductive features of A. scabra. Specimens were collected between 2006 and 2007 in São Sebastião Island, southeastern Brazil, in 13 locations. The fecundity of 21 ovigerous females analyzed ranged between 414 and 19,250 eggs, which were higher than previously reported. However, the larger size of females analyzed may explain the observed intraspecific difference in egg production. During embryogenesis, egg volume and water content increased by 103 and 22.6%, respectively. The initial egg volume of A. scabra in the present study (0.027 mm³) was slightly lower, but comparable to the values reported previously from the same study area. During incubation, females of A. scabra lost 15% of their initially produced eggs. The reproductive output (average RO of 3.6%) is the first report for any atyid species. Its value is fairly low compared to other freshwater shrimps, and it is hypothesized that this might be related to a high energy investment in morphological adaptations, which allows the shrimp to cling on to the substrate in the fast flowing environment they inhabit. Additionally, the long life span, a well-known phenomenon in atyid shrimp, may allow the species to invest a relatively low amount of energy per brood in egg production, but over a longer time span.

El camarón carídeo de agua dulce, Atya scabra, es un residente común del sistema de arroyos de los bosques tropicales de América, incluyendo drenajes brasileños. Este camarón tiene un ciclo de vida anfídromo, lo que aumenta su vulnerabilidad al enfrentar la fragmentación del hábitat. Dado que la información sobre la reproducción de esta especie es todavía limitada, se presentan datos sobre producción de huevos, pérdida de huevos e inversión energética, para lograr una mejor comprensión de los aspectos reproductivos de A. scabra. Los especímenes fueron recolectados entre 2006 y 2007 en la isla São Sebastião, al sureste de Brasil, en 13 localidades. La fecundidad de las 21 hembras ovígeras analizadas varió entre 414 y 19,250 huevos, valores que son más altos que los reportados previamente, sin embargo, el mayor tamaño de las hembras analizadas podría explicar la diferencia intraespecífica en la producción de huevos. Durante la embriogénesis, el volumen del huevo y el contenido de agua aumentó en 103 y 22,6%, respectivamente. El volumen inicial del huevo de A. scabra en este estudio (0,027 mm³), fue ligeramente inferior, pero comparable con los valores reportados anteriormente para la misma área de estudio. Durante el periodo de incubación, las hembras de A. scabra pierden el 15% de los huevos producidos inicialmente. El rendimiento reproductivo (RO promedio de 3,6%), es el primer valor reportado para cualquiera de las especies de la familia Atyidae. Este valor, es relativamente bajo en comparación con otros camarones de agua dulce, y se plantea la hipótesis de que esto podría estar relacionado con una alta inversión energética en adaptaciones morfológicas, lo que permitiría al camarón aferrarse al sustrato en las fuertes corrientes que habita. Además, la alta expectativa de vida, un fenómeno bien documentado en atyidos, podría permitir a las especies una menor inversión energética por camada de huevos, pero por un periodo de tiempo más prolongado.

During the last decades, knowledge on biodiversity of freshwater decapods has increased considerably; however, information about ecology of these crustaceans is scarce. Currently, the freshwater decapod fauna of Costa Rica is comprised by representatives of three families (Caridea: Palaemonidae and Atyidae; Brachyura: Pseudothelphusidae). The present study aims to describe the species diversity and distribution of freshwater crabs inhabiting the basin of the Rio Grande de Térraba, Pacific slope of Costa Rica, where the Instituto Costarricense de Electricidad (ICE) plans to implement one of the largest damming projects in the region. Samples were collected in 39 locations at an altitude ranging from 20 to 1,225 m. Sampling was carried out during several months in 2007, 2009 and 2010. We collected a total of 661 crabs, comprising eight species of Pseudothelphusidae of three genera, representing 53% of the 15 pseudothelphusid crab species currently recorded from Costa Rica. The most common species was Ptychophallus paraxanthusi followed by P. tristani. Freshwater crabs were more frequently encountered in the middle-low region of the basin (between 311 and 600 m) and less frequently in the medium-high basin (between 601 and 1,225 m). Ptychophallus paraxanthusi showed the widest distribution and was collected in altitudes ranging from 20 to 700 m. The Rio Grande de Térraba region can be considered as a relatively small, but highly diverse system. Therefore, any alteration of the basin of Rio Grande de Térraba, and especially the possible construction of a hydroelectric power plant, needs to be carefully analyzed to mitigate the damaging effects of this project on the freshwater crabs. More ecological information about freshwater crabs from Costa Rica and the Central American region are needed to reach a first reasonable overview on the ecological role of these decapods in freshwater systems.

El conocimiento de la biodiversidad de decápodos de agua dulce ha aumentado considerablemente durante las últimas décadas. Sin embargo, información sobre la ecología de estos crustáceos es limitada. Actualmente, la fauna de los decápodos de agua dulce está compuesta por representantes de tres familias (Caridea: Palaemonidae y Atyidae; Brachyura: Pseudothelphusidae). El presente estudio describe la diversidad de especies y la distribución de cangrejos de agua dulce de la cuenca del Río Grande de Térraba, vertiente Pacífica de Costa Rica, donde el Instituto Costarricense de Electricidad (ICE) está planeando construir una de las plantas hidroeléctricas más grandes de la región. Las muestras fueron recolectadas en 39 localidades a una altitud entre 20 y 1.225 m. El muestreo se efectuó durante varios meses de los años 2007, 2009 y 2010. Se colectó un total de 661 cangrejos de ocho especies de Pseudothelphusidae de tres géneros, lo que representa un 53% de las 15 especies de Pseudothelphusidae actualmente reportado para Costa Rica. La especie más frecuentes fue Ptychophallus paraxanthusi, seguida por P. tristani. Los cangrejos de agua dulce fueron más frecuentes en la región medio-baja de la Cuenca (entre 311 y 600 m) y menos frecuentes en la región medio-alta (entre 601 y 1.225 m). Ptychophallus paraxanthusi demostró la distribución más amplia y fue colectado en altitudes entre 20 y 700 m. Se puede considerar el Río Grande de Térraba un sistema pequeño, pero altamente diverso. Por lo tanto, cualquier alteración de la Cuenca del Rio Grande de Térraba, y especialmente la posible construcción de la planta hidroeléctrica, requiere un análisis cuidadoso para mitigar efectos dañinos de este proyecto sobre los cangrejos de agua dulce. Se requiere más información ecológica sobre los cangrejos de agua dulce de Costa Rica y la región de Centro América para obtener una primera visión razonable del rol ecológico de estos decápodos en los sistemas dulceacuícolas.