Proporción sexual y hermafroditismo del molusco, Anadara tuberculosa (Bivalvia: Arcidae) en Panamá / Sexual proportion and hermaphroditism of the mollusc, Anadara tuberculosa (Bivalvia: Arcidae) in Panama

Introducción: El bivalvo Anadara tuberculosa es un recurso pesquero y económico importante en el Pacífico Este Tropical. La proporción sexual varia a lo largo de su área de distribución, con casos de aparición de hermafroditismo, ocasional para algunas poblaciones, normal en otras. Estas características podrían ser una respuesta a presiones antropogénicas y ambientales. Objetivo: Evaluar la proporción sexual y el hermafroditismo en la especie en el Pacífico de Panamá. Métodos: Se analizó información reproductiva de A. tuberculosa generada entre 1994 y 2020 para el Golfo de Montijo, así como datos de 2017 para el manglar de David. Se aplicaron procedimientos macroscópicos, contrastados con histológicos y se generó un factor de corrección para ajustar la proporción sexual macroscópica, debido al efecto, sobre la proporción sexual, que ocasiona los organismos indeterminados. Resultados: Para el Golfo de Montijo, la histología indicó una proporción sexual hembra a macho de 1:1 hasta 3.2:1, entre 1994 y 2017, mientras que la macroscopía varió de 1.9:1 a 5.1:1 entre 2004 y 2020. Para el manglar de David, la histología indicó una proporción sexual de 3.7:1, y de 7.9:1 por macroscopía en el 2017. En ambas localidades, especímenes más grandes mostraron mayor variación en la proporción sexual, pese a la técnica implementada, así como hermafroditismo protándrico no casual en el 2017. Conclusiones: La aparición del hermafroditismo protándrico y los cambios en la proporción sexual indican que la población de A. tuberculosa, en ambas localidades, está respondiendo a presiones antropogénicas y ambientales.

Introduction: The bivalve Anadara tuberculosa is an important fishery in the Eastern Tropical Pacific. The sex ratio varies along its geographic range and there are cases of hermaphroditism, occasional in some populations, normal in others. These characteristics may be a response to anthropogenic and environmental pressure. Objective: To evaluate sex ratio and hermaphroditism of the species in the Panamanian Pacific. Methods: Data on reproductive features of A. tuberculosa generated between 1994 and 2020 for Gulf of Montijo, as well as 2017 data from mangroves of David was analyzed. Macroscopic diagnosis of individual sex is sensitive to the problem of indeterminate individuals, which in turn can skew the sex ratio analysis; therefore, the macroscopic method was compared with histological sections to generate a correction factor to adjust the macroscopically determined sex ratio. Results: For Montijo, histology indicated that the female to male sex ratio ranged from 1:1 to 3.2:1 between 1994 and 2017, while macroscopy indicated 1.9:1 to 5.1:1 between 2004 and 2020. For David, histology indicated a ratio of 3.7:1, and macroscopy 7.9:1. At both localities, larger specimens had more sex ratio variation, independently of the technique, and there was non-casual protandric hermaphroditism in 2017. Conclusion: The occurrence of protandric hermaphroditism and sex ratio changes suggest anthropogenic and environmental pressure in all populations.

Design and optimization of an experimental maintenance system for yellow clam broodstock Amarilladesma mactroides (Reeve, 1854) / Desenvolvimento e otimização de um sistema de manutenção experimental para reprodutores de marisco branco Amarilladesma mactroides (Reeve, 1854)

The yellow clam is a sand-burrowing bivalve that inhabits the dissipative beaches from southern Brazil to the north coast of Argentina. In the last decades, populations of this species have been impacted by mass mortality events, overfishing and other anthropogenic activities. The production of juveniles in captivity would allow feasibility studies to be carried out to restore the natural stock as well as the production in aquaculture systems. Given the scarcity of studies on the maintenance of this species in captivity, a culture system and a management protocol were developed and tested. Wild-caught clams (total length ≥50 mm) were used in a series of 14 day-long trials. Survival was higher in clams that were allowed to bury into the sand. A permanent ink marker covered with a thin layer of a quick-hardening adhesive proved to be a reliable method to tag clams. The maintenance of yellow clams in this system resulted in high survival and growth, increases in the condition factor and oocyte diameter, and a relative advancement of gonadal development.

O marisco branco é um bivalve de areia que habita as praias dissipativas do sul do Brasil até a costa norte da Argentina. Nas últimas décadas, as populações desta espécie têm sido afetadas por eventos de mortalidade maciça, sobrepesca e outras atividades antropogênicas. A produção de juvenis em cativeiro permitiria a realização de estudos de viabilidade para restaurar o estoque natural, assim como a produção em sistemas de aquicultura. Dada a escassez de estudos sobre a manutenção desta espécie em cativeiro, um sistema de cultivo e um protocolo de manejo foram desenvolvidos e testados. Mariscos branco selvagens (comprimento total ≥50 mm) foram utilizados em uma série de ensaios de 14 dias de duração. A sobrevivência foi maior nos mariscos que podiam ser enterrados na areia. Um marcador de tinta permanente coberto com uma fina camada de adesivo de endurecimento rápido provou ser um método confiável para marcar os mariscos. A manutenção dos mariscos neste sistema resultou em alta sobrevivência e crescimento, aumento do fator de condição e do diâmetro do ovócito, e um relativo avanço do desenvolvimento gonadal.

Biosseguridade para sistemas de produção de peixes em tanque-rede em função da colmatação agravada por Limnoperna fortunei / Biosecurity for fishfarming cage systems due to the highly clogged screen aggravated by Limnoperna fortunei

Este trabalho avaliou a colmatação por Limnoperna fortunei em diferentes materiais para confecção de telas de arame, a dinâmica da colmatação pelo molusco e a relação custo-benefício dos materiais usados em tanques-rede. Utilizaram-se amostras de telas de simples torção de malha 19mm, de cinco tipos diferentes de revestimentos, colocadas na barragem de Salto Caxias, no Rio Iguaçu, estado do Paraná, entre julho de 2012 e julho de 2014. A cada seis meses, foi verificado o ganho de peso das telas em razão da colmatação, além da contagem do número de mexilhões aderidos. Após as coletas dos dados, foi realizado o teste estatístico de Kruskal-Wallis para se avaliar o ganho de peso das telas devido à colmatação. Realizou-se também uma pesquisa com 21 empresas para se obter o preço comercializado de telas para confecção de tanques-rede e se avaliar a expectativa de durabilidade dos materiais. Verificou-se que os diferentes materiais avaliados para as telas influenciam na colmatação e aderência do mexilhão-dourado; além disso, constatou-se que a tela mais eficiente quanto ao custo/ano é a de arame galvanizado plastificado e, para baixa colmatação, a de arame Bezinal.(AU)

This research evaluated degree of clogging by Limnoperna fortunei in different materials for wire mesh fabrication, the dynamics of mollusk sealing and the cost-benefit ratio of these materials used in tank-nets. Samples of single-twist screens of 19 mm mesh were used, from five different types of coatings were placed in the Salto Caxias dam on the Iguaçu River in the Paraná state, between July 2012 and July 2014. Every six months, it was verified the weight gain of the screens due to clogging and counting of the number of mussels adhered. After the data collection was performed Kruskal-Wallis statistical test to evaluate the weight gain of the screens due to clogging. In addition, a survey was carried out with 21 companies to obtain the commercialized price of screens for the production of net tanks and to evaluate the expected durability of the materials. The different materials evaluated for the screens influenced the sealing and adhesion of the golden mussel. In addition, the most cost-per-year screen is that of plastic-coated galvanized wire and for low clogging it is the Bezinal wire.(AU)

Reproductive periods of Lucina pectinata (BIVALVE; LUCINIDAE) in the Paranaguá Estuarine Complex, Paraná - Brazil / Período reprodutivo de Lucina pectinata (BIVLAVE; LUCINIDAE) no Complexo Estuarino de Paranaguá, PR - Brasil

Abstract The objectives of the present study is to describe the size for exploitation and gonadal maturation of L. pectinata in Peças Island in Paraná coast. Twenty two individuals were sampled every month, from an intertidal flat of the Peças River, Municipality of Guaraqueçaba, during two periods – summer/autumn and winter of the 2009. Environmental parameter data was obtained at the same time of the biological sampling: temperature, salinity and seawater transparency at the Peças River mouth. The animals’ height, length, width, gross weight, wet weight of meat and dry weight of meat were measured at the lab. The gonad development stages (GDS), condition index (CI) and yield index (Y) were calculated. Sex identification was conducted by direct observation of the gonads and gametes under an optic microscope. Individuals were classified as males (M), females (F) or undetermined (U). The medium height observed was of 49.62 ± 6.84 mm. Period of more expressive gonad repletion were observed in summer when water temperature was higher. Results of GDS in both periods showed a predominance of partially filled gonad stages. This may be related with the fact that L. pectinata has intense gametogenesis activity, that is, the organisms do not have a resting interval, but go back to gonad restructuring rapidly after releasing the gametes. The continuity of the reproductive cycle of the specimens found in both studied periods could demonstrate a possible continuous reproduction of the species and a size for exploitation above 40.00 mm of height.

Resumo O presente estudo tem como objetivo descrever o tamanho de exploração e a maturação gonadal de L. pectinata na Ilha das Peças no litoral do Paraná. Vinte e dois indivíduos foram amostrados mensalmente na região entre-marés no Rio das Peças, Município de Guaraqueçaba, durante 2 períodos – verão/outono e inverno de 2009. Paralelamente às amostragens, foram obtidos dados dos parâmetros ambientais: temperatura, salinidade e transparência da água do mar na foz do Rio das Peças. A altura, comprimento, largura, peso bruto, peso úmido da carne e peso seco da carne dos animais foram medidos no laboratório. Foram calculados os estágios de desenvolvimento gonadal (EDG), índices de condição (IC) e de rendimento (R). A Identificação do sexo foi realizada por observação direta das gônadas e gametas sob microscópio óptico. Os indivíduos foram classificados como: machos (M), fêmeas (F) ou indeterminados (I). A altura média observada foi de 49,62 ± 6,84 mm. O período de maior repleção gonadal foi observado no verão, quando a temperatura da água foi mais elevada. Resultados dos EDG em ambos os períodos mostrou um predomínio de gônadas parcialmente cheias. Isso pode estar relacionado com o fato de que L. pectinata tem atividade gametogênese intensa, ou seja, os organismos não têm um intervalo de repouso, mas voltam a reestruturação das gônadas rapidamente após liberação dos gametas. A continuidade do ciclo reprodutivo dos espécimes encontrados em ambos os períodos estudados, pode demonstrar possível reprodução contínua da espécie e tamanho de exploração superior a 40,00 mm de altura.

Growth and production of Donax striatus(Bivalvia: Donacidae) from Las Balsas beach, Gibara, Cuba / Crecimiento y producción de Donax striatus (Bival-via: Donacidae) en playa Las Balsas, Gibara, Cuba

Abstract:Clams of the genus Donaxare worldwide the dominating group of the invertebrate community on sandy beaches. They are primary consumers that provide a significant abundance and biomass to the ecosystem. In the Caribbean, Donax striatushas an important role for nature and human, nonetheless studies on the population dynamics of this beach clam are scarce and no information exists on secondary production of this species. Growth parameters and secondary production of D. striatuswere estimated from February 2008 to November 2009 at Las Balsas beach, Northeastern Cuba, in order to provide basic information for management purposes. In each month 45 samples were taken by means of a PVC corer of 0.025 m2 area and sieved with a 1 mm mesh. Animals were measured and weighted with and without shell. A total of 5 471 specimens were collected during the sampling period. Shell length ranged from 2.7-33.3 mm. Growth parameters estimated from length frequency data were Lm = 36.1 mm, K= 0.8/yr and t0 = 0.2/yr. The growth performance resulted in values of 0'= 3.02. Life span was 2.4 yrs and mortality rate was 3.07 /yr. In 2008, mean abundance of D. striatusranged between 17.1770.7 ind./m2. In 2009 the lowest mean abundance was 34.4 and the highest was 892.5 ind./m2. During 2009 biomass and production was more than twice higher in comparison with 2008. Individual production showed highest values in the 24 mm shell size (3.74 g/m2.yr) and 25 mm (0.71 g/m2.yr), considering mass with shell and without shell, respectively. During 2009 abundance of individuals with 15 mm shell length or more increased resulting in higher biomass and production, compared to 2008. Using the conversion factor of wet mass to ash free dry mass (AFDM), annual production ranged between 2.87-6.11 g AFDM/m2.yr, resulting in a turnover rate (P/B) between 5.11 and 3.47 in 2008 and 2009, respectively. The rapid growth and high turnover rate of D. striatussuggest a rapid recovery of the population. These results support the idea that this beach clam is an important resource at Las Balsas beach. Thus its exploitation must continue with caution, and only at the level of a recreational fishery.

Resumen:Los estudios sobre la dinámica poblacional de la almeja de playa Donax striatusson escasos y no existe información sobre la producción secundaria de alguna población de esta especie. Los parámetros del crecimiento y la producción secundaria de D. striatusfueron estimados a partir de datos de muestreo obtenidos entre febrero 2008 y noviembre 2009 en playa Las Balsas en la zona norte oriental de Cuba para aportar información básica para su manejo. Cada mes se recolectaron 45 muestras usando un núcleo de PVC de 0.025 m2, el sedimento fue tamizado en malla de 1 mm. Los individuos recolectados fueron medidos y pesados con concha y sin concha. La longitud de la concha fue de 2.7-33.3 mm. Los parámetros de crecimiento estimados a partir de las frecuencias de tallas fueron: Lm= 36.1 mm, K= 0.8/año y t0 = 0.2/año. El índice de crecimiento fue de 0'= 3.02. El tiempo de vida estimado de 2.4 años y la mortalidad 3.07/año. En 2008 la abundancia media de D. striatusfluctuó entre de 17.1-770.7 ind/m2. En 2009 la menor abundancia fue de 34.4 y la mayor de 892.5 ind/ m2. En 2009 la biomasa y la producción fueron más del doble que las estimadas en 2008. La mayor producción somática individual fue aportada por individuos de 24 mm (3.74 g/m2.año) y 25 mm (0.71 g/m2.año), considerando la masa total con concha y sin concha respectivamente. Durante 2009 la abundancia de individuos de 15 mm de longitud o más, se incrementó resultando en mayor bio-masa y producción en comparación con 2008. Usando el factor de conversión de peso húmedo a peso seco libre de cenizas (PSLC), la producción anual en 2008 fue de 2.87 y en 2009 fue 6.11 g PSLC/m2.año, lo que resulta en una tasa de renovación (P/B) de 5.11 en 2008 y 3.47 en 2009. Estos resultados apoyan la idea que la almeja de playa es un recurso importante y su explotación debe continuar con cautela y solo a un nivel de una pesquería recreativa.

Intra-specific variability in life-history traits of Anadara tuberculosa (Mollusca: Bivalvia) in the mangrove ecosystem of the Southern coast of Ecuador / Variaciones en la historia de vida de Anadara tuberculosa (Mollusca: Bivalvia) en el ecosistema de manglar de la costa Sur de Ecuador

Anadara tuberculosa is one of the most important bivalves along the Western Pacific coast because of its commercial value. Nevertheless, the variability in growth, longlife span, natural mortality and reproductive parameters of this mangrove cockle has not yet been described. The aim of this study was to analyze these lifehistory traits in three areas of the Southern coast of Ecuador. Empirical and length-based methods were used to estimate these biological parameters. Body size data were collected from the commercial fishery between 2004 and 2011 in landing ports near to the Archipelago of Jambeli [Puerto Bolivar (PB), Puerto Jeli (PJ) and Puerto Hualtaco (PH)]. The von Bertalanffy growth parameters for combined sex were estimated between 70.87 to 93.45mm for L∞ and 0.22 to 0.80/year for k. The growth indices (Φ’) ranged from 3.17 to 3.85, while the overall growth performance (OGP) ranged from 5.03 to 5.82. The mean of long-life span (t max), size and age at maturity (L50% and t50%) were estimated in 7.71±2.53years, 39.13±2.24mm and 1.46±0.56years for PB; 9.51±2.85years, 37.78±1.95mm and 1.37±0.41years for PJ and 5.81±2.11years, 39.73±3.31mm and 0.94±0.41years for PH. Natural mortality (M) ranged from 0.46 to 1.28/year. We concluded that significant intra-specific variation was observed in a temporal scale in Φ’ and OGP indices as well as L50% and M. Therefore, temporal changes in these life-history traits should be taken into account when assessing the status of the mangrove cockle fishery.

La pesquería de la concha prieta (Anadara tuberculosa) es una de las más importantes a lo largo de la costa del Pacifico. Las variaciones intra-especificas en el crecimiento, longevidad, mortalidad natural y parámetros reproductivos de la concha prieta, aún no han sido descritas. Por lo tanto, el objetivo de este estudio fue analizar esos parámetros biológicos en tres áreas al Sur de Ecuador. Métodos empíricos y basados en tallas fueron empleados para estimar los parámetros de historia de vida. Los datos de tallas analizados correspondieron al periodo 2004-2011 y son provenientes del muestreo de los desembarques de los puertos adyacentes al Archipiélago de Jambeli [Puerto Bolivar (PB), Puerto Jeli (PJ) y Puerto Hualtaco (PH)], al Sur de Ecuador. Los parámetros de crecimiento oscilaron entre 70.87 y 93.45mm de L∞ y 0.22 a 0.80/año de k. Mientras que los índices de crecimiento entre 3.17 a 3.85 de Φ’ y 5.03 a 5.82 de OGP. Los valores promedio de longevidad (t max), talla y edad de madurez (L50% y t50%) fueron de 7.71±2.53años, 39.13±2.24mm y 1.46±0.56años en PB; 9.51±2.85años, 37.78±1.95mm y 1.37±0.41años en PJ y de 5.81±2.11años, 39.73±3.31mm y 0.94±0.41años en PH. Las estimaciones de mortalidad natural (M) oscilaron entre 0.46 y 1.28/año. Importantes cambios intra -especificos se observaron a escala temporal tanto en los índices Φ’ y OGP, así como en L50% y M. Por lo tanto, se sugiere considerar las variaciones temporales en los parámetros biológicos de A. tuberculosa, al momento de caracterizar el estatus de su pesquería y más aun si es sometida a altos niveles de extracción.

Modelación del crecimiento individual del callo de hacha Atrina maura (Bivalvia: Pinnidae) a partir de la inferencia multi modelo / Individual growth modeling of the penshell Atrina maura (Bivalvia: Pinnidae) using a multi model inference approach

Growth models of marine animals, for fisheries and/or aquaculture purposes, are based on the popular von Bertalanffy model. This tool is mostly used because its parameters are used to evaluate other fisheries models, such as yield per recruit; nevertheless, there are other alternatives (such as Gompertz, Logistic, Schnute) not yet used by fishery scientists, that may result useful depending on the studied species. The penshell Atrina maura, has been studied for fisheries or aquaculture supplies, but its individual growth has not yet been studied before. The aim of this study was to model the absolute growth of the penshell A. maura using length-age data. For this, five models were assessed to obtain growth parameters: von Bertalanffy, Gompertz, Logistic, Schnute case 1 and Schnute and Richards. The criterion used to select the best models was the Akaike information criterion, as well as the residual squared sum and R² adjusted. To get the average asymptotic length, the multi model inference approach was used. According to Akaike information criteria, the Gompertz model better described the absolute growth of A. maura. Following the multi model inference approach the average asymptotic shell length was 218.9mm (IC 212.3-225.5) of shell length. I concluded that the use of the multi model approach and the Akaike information criteria represented the most robust method for growth parameter estimation of A. maura and the von Bertalanffy growth model should not be selected a priori as the true model to obtain the absolute growth in bivalve mollusks like in the studied species in this paper.

El molusco bivalvo Atrina maura (Sowervy 1835) habita aguas marinas someras y estuarios en la costa del Pacífico desde Baja California, México hasta Perú. Es un organismo cuyo crecimiento individual ha sido insuficientemente modelado. El objetivo del estudio fue modelar su crecimiento individual absoluto mediante el uso de datos de longitud a la edad obtenidos de una región del Golfo de California. Los parámetros fueron obtenidos con el uso de cinco modelos de crecimiento; von Bertalanffy, Gompertz, Logístico, Caso 1 de Schnute y Schnute & Richards. Se seleccionó el mejor modelo usando el criterio de información de Akaike, AIC, pero se calcularon también la suma de residuos al cuadrado y la R² ajustada. Para obtener la longitud asintótica se siguió el enfoque de inferencia multi modelo IMM. Según el AIC el modelo que mejor describe el crecimiento absoluto de A. maura es el de Gompertz y colocó en cuarto lugar jerárquico el de von Bertalanffy. La longitud asintótica promedio encontrada, siguiendo la IMM, fue de 218.9mm (IC 212.3-225.5) de longitud de concha. Se concluye que tanto la IMM como el AIC representan las herramientas más sólidas para evaluar parámetros de crecimiento individual de A. maura y que el modelo de crecimiento de von Bertalanffy no debe ser seleccionado a priori como la opción para describir el crecimiento individual en moluscos bivalvos como la especie estudiada.

Reproductive cycle of Tagelus plebeius (Mollusca: Bivalvia) in the estuary of the Cachoeira River, Ilhéus, Bahia, Brazil / Ciclo reprodutivo de Tagelus plebeius (Mollusca: Bivalvia) no estuário do Rio Cachoeira, Ilhéus-Bahia, Brasil

This study characterized the reproductive cycle of the stout razor clam Tagelus plebeius in the estuary of the Cachoeira River, Ilhéus, Bahia, northeastern Brazil. Samples of 20 animals per collection were taken biweekly from August 2005 to August 2006. The 480 specimens were measured on the antero-posterior axis (length) and then removed from the shell. After macroscopic analysis, the gonads were fixed in Davidson's solution, processed by routine histology and stained by Harris hematoxylin and eosin. The gonads of both males and females appeared milky white, without sexual dimorphism. Microscopic analyses indicated a M: F ratio of 1.06: 1 and continuous reproduction of T. plebeius in the region. The period from August to October showed the most intense spawning. This study provides another example of continuous reproduction of bivalves in tropical waters, and because this species is a heavily exploited fishery resource in the region, it draws attention to the need for a management plan aimed at reducing harvests.

Neste estudo, objetivou-se caracterizar o ciclo reprodutivo de Tagelus plebeius na região estuarina do Rio Cachoeira, Ilhéus-Bahia. As amostragens, 20 animais/coleta, foram feitas quinzenalmente, entre agosto de 2005 e agosto de 2006. Os 480 animais, depois de medidos quanto ao seu eixo ântero-posterior (comprimento), foram removidos da concha e, após análise macroscópica, as gônadas foram fixadas em solução de Davidson, processadas por técnica rotineira de histologia e coradas com hematoxilina de Harris e eosina. As gônadas de machos e fêmeas apresentaram aspecto branco leitoso e não houve dimorfismo sexual. As análises microscópicas evidenciaram razão sexual M:F de 1,06:1 e reprodução contínua de T. plebeius na região. O período entre agosto e outubro foi caracterizado como o de maior eliminação de gametas. O estudo fornece outro exemplo de reprodução contínua de bivalves em regiões tropicais e, por ser um recurso pesqueiro intensamente explorado na região, chama a atenção para a criação de um plano de manejo que vise à redução de sua coleta.

Condición somática de la almeja Polymesoda solida (Veneroidea: Corbiculidae) durante el periodo lluvioso, enel Parque Natural Isla de Salamanca, Caribe colombiano

Somatic condition of the clam Polymesoda solida (Veneroidea: Corbiculidae) in the rainy season of the Salamanca Island Natural Park, Colombian Caribbean. The estuarine clam Polymesoda solida is the main fishery resource in the Salamanca Island Natural Park. I sampled the clam in three interconnected lagoons (Poza Verde, El Torno and Atascosa) during the rainy period (April to November 2004). Sixty individuals were monthly collected by hand on each lagoon; 30 to analyze two condition indexes (relationship between body and shell weight and between soft dry and wet weight), yield (meat percentage) and length-weight relationships. Maturity of female gonad smears was assessed on the remaining individuals. Measures of salinity, temperature, pH, dissolved oxygen, transparency and depth, were also taken at the collection places. Increases of the condition indexes occurred when the Magdalena River showed some decreases in its level, especially at Poza Verde and El Torno. The condition indexes were higher at 27-33mm, (range where maturity size was reached). Clams from Poza Verde, the lagoon nearest to the Magdalena River, had the highest values in condition indexes, yield, fresh weight and maturity frequency. Yield was directly correlated to the condition indexes and sexual maturity. The condition index (body weight/shell weight) showed a highest multiple regression coefficient with salinity, pH and transparency (R²=74%), indicating the relevance of the hydrological regime in the regulation of the condition of the organisms. P. solida seems to be more adapted to the lowest salinities of the system (0.0-0.4), corresponding to Poza Verde, where the influence of the Magdalena river is more direct and steady. Additionally, differences found between sites in the assessed variables, emphasize the importance of considering spatial heterogeneity of this kind of lagoon estuaries, and should be taken into account for future fisheries management in the rainy period and conservation of P. solida populations. Rev. Biol. Trop. 58 (1): 131-145. Epub 2010 March 01.

Se evaluó la condición somática de la almeja Polymesoda solida en tres lagunas del Parque Isla de Salamanca (abril a noviembre de 2004), durante el periodo lluvioso. En 60 individuos por laguna, se analizaron mensualmente índices de condición, rendimiento, relación talla-peso y madurez gonadal en fresco. También se midió salinidad, temperatura, pH, oxígeno disuelto, transparencia y profundidad del agua. Los mayores índices de condición coincidieron con descensos en el nivel del río Magdalena, especialmente en Poza Verde y El Torno. Estos índices fueron más altos en tallas entre 27mm y 33mm, donde también se ubicó la talla media de madurez sexual. En Poza Verde, laguna con mayor influencia del río, se presentaron los mayores índices de condición, rendimiento, peso húmedo y frecuencia de madurez, revelando una mejor condición de los organismos. El índice de condición (peso cuerpo/ peso concha) presentó mayor coeficiente de regresión múltiple con la salinidad, pH y transparencia, sugiriendo la importancia del régimen hidrológico en su regulación. Las diferencias espaciales en las variables evaluadas, resaltan la necesidad de tener en cuenta la heterogeneidad de este tipo de estuarios para la conservación y manejo adecuado de la pesquería de P. solida.

Crecimiento y mortalidad de la concha nácar Pteria sterna en bancos silvestres de Baja California Sur, México

Growht and mortality of the mollusk Pteria sterna in wild banks of Southern Baja California, Mexico. The Gulf of California nacre shell Pteria sterna is an important marine resource in Mexico, and the main species for "half" and round pearl production in the American continent. Wild spat can only be extracted legally for research or culture activities. This study calculates growth and mortality parameters for wild stocks in the eastern coast of Southern Baja California. Height’s data (353 dorso-ventral measurements) were taken from 1997 to 1999 at Santa Rosalía, Mulegé and Loreto Bay coast. The maximum length was estimated at 130.35 mm (124.22-136.48 mm, p>0.95). The length frequency data were set in a "virtual year". Seasonal von Bertalanffy growth parameters were calculated in the ELEFAN I routine, the values are: L∞ = 156.02 mm, k = 0.48 year-1, t0 = -0.216 years, C = 0.43, WP = 0.73. and t s = 0.5. The growth performance index was Φ’ = 4.068. The total mortality was calculated from length-converted catch curve Z = 3.34 year-1. The length-weight relationship was fixed for the equation W = 0.000756 * L(i)2.7075 (r²= 0.90, n = 233). The growth parameters values in experimental repopulation conditions are quite different, in contrast with the growth estimated in wild stocks oysters. The value of total mortality is similar to the estimations for Pinctada fucata populations from the Red Sea and P. radiata from the Mediterranean Sea. Rev. Biol. Trop. 57 (3): 659-670. Epub 2009 September 30.

La concha nácar Pteria sterna sustenta los perlicultivos en México, y es la base de producción de perlas en el continente Americano. Está bajo protección especial desde 1994, y solo puede capturarse semilla natural para cultivo e investigación. Determinamos su crecimiento y mortalidad en bancos silvestres, registrando la altura de ostras de Santa Rosalía, Mulegé y Bahía de Loreto (1997-99). La longitud máxima estimada fue 130.35 mm (124.22-136.48 mm, P>0.95). Las frecuencias de longitudes se ordenaron en un "año virtual" (Guanco 1991). Los parámetros de crecimiento de von Bertalanffy estimados con el programa ELEFAN I fueron: L∞= 156.02 mm, k=0.48año-1, t0=-0.216 años, C= 0.43 y WP = 0.73; el índice de desempeño de crecimiento fue Φ’ = 4.068. La mortalidad total fue de Z = 3.34 año -1por longitud convertida a curva de captura. La regresión del peso total y la altura tuvo la expresión W = 0.000756 * L(i)2.7075 (r²=0.90, n=233). Mostramos la diferencia entre los parámetros de crecimiento en condiciones de repoblamiento experimental y aquellos de individuos silvestres de P. sterna. El valor de mortalidad total es comparable a aquellos de Pinctada fucata en el mar Rojo o P. radiata en el mar Mediterráneo.

First occurrence of Limnoperna fortunei (Dunker, 1857) in the Rio Tietê watershed (São Paulo State, Brazil) / Invasão de Limnoperna fortunei (Dunker, 1857) na bacia do rio Tietê (SP)

This paper describes the recent expansion of the geographical distribution of Limnoperna fortunei (Dunker, 1857) in the Tietê River watershed, São Paulo State, Brazil. Estimations related to the velocity of invasion and its causes are presented. Ecological implications related to biodiversity and possible changes in the food chain are discussed.

Este artigo descreve a recente expansão da distribuição geográfica de Limnoperna fortunei (Dunker, 1857) na bacia hidrográfica do rio Tietê, estado de São Paulo, Brasil. Foram apresentadas estimativas da velocidade de invasão destes organismos e sua via de entrada no rio Tietê. Foram discutidas as possíveis modificações na cadeia alimentar e as implicações ecológicas da invasão do mexilhão-dourado.

Parasitas em ostras de cultivo (Crassostrea rhizophorae e Crassostrea gigas) da Ponta do Sambaqui, Florianópolis / Parasites in cultured oysters (Crassostrea rhizophorae and Crassostrea gigas)from Ponta do Sàmbaqui, Florianópolis

Estudou-se a presença de parasitas e realizaram-se exames macroscópicos e histológicos em ostras (Crassostrea rhizophorae e Crassostrea gigas) cultivadas. Entre agosto de 2002 a maio de 2003, 30 indivíduos adultos de cada espécie foram coletados sazonalmente, totalizando 240 ostras. Os animais, provenientes de desova em laboratório, foram mantidos em lanternas de cultivo, em sistema suspenso tipo espinheI, com densidade de 40 ostras/andar. A cada coleta era registrada a mortalidade das ostras, a temperatura e a salinidade da água. A temperatura variou de 19 a 28,5°C e a salinidade, 31 a 350/00. A mortalidade foi de 48,3 para C. gigas e 70,8 para C. rhizophorae. A infestação pelo poliqueta Polydora websteri em C. gigas foi 100 durante todo o período e em C. rhizophorae, 100 em fevereiro e maio. O mal do pé foi observado em novembro (3,3) e maio (23,3) em C. gigas e maio (6,6) em C. rhizophorae. As maiores prevalências do protozoário Nematopsis sp. foram de 70 e 60 em C. gigas e C. rhizophorae, respectivamente. O protozoário Trichodina sp. ocorreu em 1,6 de C. rhizophorae, e larvas do cestóide Tylocephalum sp. foram observadas em 2,5 de C. gigas. Nenhum dos parasitas encontrados foi associado à mortalidade das ostras.

Diversidad y abundancia de moluscos de la epifauna en la comunidad sublitoral de Punta Patilla, Venezuela / Diversity and abundance of mollusks in the sublittoral epifaunal community of Punta Patilla, Venezuela

The diversity of a sublittoral epifaunal mollusk community of Punta Patilla, Sucre State, Venezuela, was studied from September 1990 to September 1991. We identified 25 species (14 bivalves and 11 gastropods) of mollusks that inhabit gravel, soft sand and bottoms covered by Thalassia testudinum.Total diversity indices were H´= 3.42, J´= 0.74 and 1-D = 0.85. Monthly diversity reached its maximum in March 1991 (3.12 bits/ ind.), June 1991 (2.88 bits/ind.) and September 1991 (2.95 bits/ind.); minimum diversity was recorded in August 1991 (1.20 bits/ind.).A log series model showed a diversity index alpha = 4.56 for species abundance data and alpha = 3.11 for biomass data. The more abundant species were Chione cancellata, Antigona listeri, Chione granulata and Arca zebra among the bivalves, and Chicoreus brevifrons, Turritella variegata and Phyllonotus pomum among the gastropods (which present maximum biomass). The average total biomass (56.80 g/m2 )is low when compared to reports from other tropical zones

Se estudió la diversidad de una comunidad malacológica sublitoral en Punta Patilla, Estado Sucre, Venezuela, desde septiembre 1990 hasta septiembre 1991. Se identificaron 25 especies, 14 bivalvos y 11 gasterópodos. Los parámetros de diversidad total en número de la comunidad fueron H´=3.41 bits/ind., J´=0.74 y 1-D =0.85. Las máximas diversidades mensuales se observaron en marzo 1991 (3.12 bits/ind.), junio 1991 (2.88 bits/ind) y septiembre 1991 (2.95 bits/ind.) y la mínima ocurrió en agosto 1991 (1.20 bits/ind.). Los datos del número de individuos conforman una línea recta ajustada por la serie logarítmica con un índice alfa =4.56 y alfa =3.11 para los de biomasa. Las especies más abundantes fueron Chione cancellata, Antigona listeri, Chione granulata y Arca zebra entre los bivalvos, y Chicoreus brevifrons, Turritella variegata y Phyllonotus pomum entre los gasterópodos, estos presentaron las máximas biomasas individuales. La biomasa total promedio de la comunidad (56.80 g/m2 ) es baja cuando se compara con otros reportes de áreas tropicales. Los moluscos habitaron fondos de grava y arenofangoso cubiertos por praderas de Thalasia testudinum

In vitro explant culture of mantle epithelium of freshwater pearl mussel.

The in vitro culture of nacre secreting pallial mantle explants of freshwater pearl producing mussel, Lamellidens marginalis (Lamarck) included depuration of pearl mussels with different physical and chemical agents to eradicate various commensals, removal of pallial mantle ribbon, aseptic preparation of explants from the ribbon and transfer of those explants into tissue culture petri dishes. Special synthetic tissue culture media enriched with additives viz., inactivated calf fetal serum and antibiotics were poured into plates with explants. The culture plates were incubated at 30 degrees C in a CO2 incubator at 5%, CO2. The cultures could be maintained for 42-45 days without any contamination. After 12 hr epithelial like cells began to migrate out and formed a complete cell sheet surrounding the explant within 12-15 days. The epithelial cells in the culture indicated functional viability as subsequently after 38-40 days of culture, typical aragonitic 'nacre' crystals of CaCO3 could be observed throughout the culture plates.

Embrionary and larval development of the marine clam Tivela mactroides (Bivalvia: Veneridae)in Zulia State, Venezuela

The marine clam,Tivela mactroides ,from Caño Sagua beach,Venezuela,was spawned and reared under laboratory conditions to monitor its early development.Spawning was spontaneous but in some cases it had to be induced by the additon of eggs and sperm.After fertilization,the embryonic development occurred at 5 hr approximately. Trochophore larvae were observed between eight and ten hours later.Straight-hinged veliger stage appeared 15 hr after fertilization.Transition from veliger stage to the umbo stage occurred about eight days after fertilization.Pediveliger stage was observed 22 days after fertilization.Metamorphosis of T.mactroides was not successful under our laboratory conditions;probably the bacterial contamination and subsequent mortalities were important factors constraining the final phase of the larval cycle.However,in a few cases young individuals were observed.We suspect that this was due to unfavorable conditions (e.g.:bacterial contamination, unsuitable food availability,etc.)and the broad variation in developmental times,suggesting that these stages might be particularly sensitive to environmental changes.These results may not necessarily reflect what happens under natural conditions

La almeja Tivela mactroides ,de la playa Caño Sagua, Venezuela,fue desovada y cultivada bajo condiciones de laboratorio,monitoreando su desarrollo embrionario y larvario.El desove fue espontáneo,sin embargo,en algunos casos se indujo adicionando óvulos y espermatozoides. El desarrollo embrionario se produjo en cinco horas, aproximadamente.La larva trocófora fue observada a las diez horas,mientras que la prodisoconcha aparece a las 15 horas después de la fertilización.La larva disoconcha aparece ocho días después de la fecundación y la veliconcha,aproximadamente a los 20 días.La metamorfosis de T.mactroides no fue satisfactoria bajo estas condiciones, ya que la contaminación bacterial fue uno de los principales factores que provocó la mortalidad de las larvas durante la fase final del ciclo,sin embargo,en algunos casos, se observaron juveniles.Las condiciones no favorables (contaminación bacteriana,disponibilidad de alimentos, etc.)y la variación en los tiempos de desarrollo,sugieren que estos estadios son muy sensibles a los cambios ambientales. Estos resultados no necesariamente reflejan lo que ocurre en el medio natural

Efecto de la alimentación sobre la condición fisiológica del mejillón Perna viridis (Bivalvia: Mytilidae), según el cociente ARN/ADN / Food effect on the physiological condition of the Perna viridis mussel (Bivalvia: Mytilidae), using the RNA/DNA quotient

The green mussel, Perna viridis, became widespread in the northern coast of Sucre State since its arrival to Venezuela in 1993. RNA/DNA and Protein/DNA ratios were used to study the effect of starvation on its instantaneous growth. The mussels were collected in La Esmeralda and Chacopata, acclimatized in the laboratory for four weeks and maintained for another six weeks in two groups: one fed ad libitum and another without food (this later group was later fed for two additional weeks). Protein (colorimetric method), and nucleic acid concentrations (RNA and DNA, fluorometric method with ethidium bromide) were measured in adductor muscle, digestive gland and gills. The instantaneous growth was assessed using RNA/DNA and Protein/DNA rations. These indexes were always higher in the fed organisms. Animals from Chacopata were in better physiological condition that those from La Esmeralda during the abstinence time (six weeks). Muscle was the best tissue to determine instantaneous growth. The RNA/DNA ratio is a reliable index to determine the physiological condition and instantaneous growth of this species.

Biometría de Modiolus capax (Bivalvia: Mytilidae) en Playa Ocotal, Guanacaste, Costa Rica / Biometry of Modiolus capax (Bivalvia: Mytilidae) in Playa Ocotal, Guanacaste, Costa Rica

155 specimens of mussels (Modiolus capax) were gathered during March 1993 in a subtidal bed, located in northern Ocotal, Guanacaste, Costa Rica. For each individual in the random sample, shell length, breadth and height were measured and total weight, shell weight empty and meat weight were controlled. Analysis of data determined relationships of length to weight, length to breadth and length to height of Lt = 1.31977 Pt + 29.05478, Lt = 0.36605 D + 3.98744 and Lt = 0.50434 A + 2.73786. The mean Conditional Index for the population was 39 +/- 0.07