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.

Studies on the morphology of cercariae obtained from freshwater snails at Erawan Waterfall, Erawan National Park, Thailand.

The morphology of cercariae of freshwater snails from Erawan Waterfall, Erawan National Park, Kanchanaburi Province was studied between December 2002 and August 2003. The snail samples were collected by handpicking using a counts per unit of time sampling method. The cercariae, larva stage of a trematode, were investigated using the shedding method where they were categorized into three groups and six species. The first group, Pleurolophocercous cercariae, consists of Haplorchis pumillo (C1) and Stictodora tridactyla (C3). The second group, Furcocercous cercariae, consisted of Mesostephanus appendicalatus (C2), Transversotrema laruei (C6) and Cardicola alseae(C4). The third group, Xiphidio cercariae, has only one species which is Loxogenoides bicolor (C5). Out of 1163 snails, only 62 were found to be infected by cercariae, equivalent to a 5.33% infection rate. The infections grouped by species of the cercariae are as follows: C, 22 (1.9%), C, 29 (2.5%), C2 1 (0.1%), C6 1 (0.1%), C4 6 (0.5%) and C5 3 (0.3%). The freshwater snail samples consist of four species. From a total of 1163 samples, there are 687 Melanoides jugicostis, 91 Tarebia granifera, 296 Thiara scabra and 89 Melanoides tuberculata. Infections were found in 45 (6.5%), 6 (6.6%), 1 (0.3%) and 10 (11.2%), respectively.

Freshwater mollusks at designated areas in eleven provinces of Thailand according to the water resource development projects.

The study was conducted at 75 collecting loci in 15 districts of 11 provinces in Thailand during 1999-2004. A total of 12,079 live mollusks were collected, 11,874 were snails and 205 were clams. The snails were comprised of 39 species and classified into 9 families: Ampullariidae, Bithyniidae, Buccinidae, Potamiopsidae, Stenothyridae, Thiaridae, Viviparidae, Planorbidae and Lymnaeidae. The clams were comprised of 14 species classified into 2 families: Amblemidae and Corbiculidae. Fifteen species were medically important snails: Pomacea canaliculata, Pila ampullacea, P. pesmei, P. polita, Bithynia (Digoniostoma) funiculata, B. (D.) siamensis goniomphalos, B. (D.) s. siamensis, Filopaludina (Siamopaludina) martensi martensi, F. (Filopaludina) sumatrensis polygramma, Melanoides tuberculata, Tarebia granifera, Helicorbis umbilicalis, Gyraulus convexiusculus, Indoplanorbis exustus and Radix rubiginosa. Of these 3 snail species harbored trematode cercariae. I. exustus harbored Echinostoma malayanum, Xiphidio and Schistosoma spindale, and R. rubiginosa and B. (D.) siamensis goniomphalos harbored Xiphidio and intestinal flukes, respectively.

Freshwater mollusks of medical importance in Kalasin Province, northeast Thailand.

A snail survey was performed in six districts around irrigation areas of Lampao Dam, in Kalasin Province. The survey caught a total of 5,479 live snails and classed them into five families, 12 genera and 15 species, of which 7 species are suspected of transmitting human parasitic diseases. The seven species were Pila polita, Pomacea canaliculata, Filopaludina (S.) m. martensi, Bithynia (Digoniostoma) siamensis goniomphalos, Melanoides tuberculata, Radix rubiginosa, and Indoplanorbis exustus. Of these, B. (D.) s. goniomphalos and I. exustus were found to harbor emergent cercariae. Only B. (D.) s. goniomphalos hosted several types of cercariae--Opisthorchis viverrini, unidentified species of intestinal flukes, echinostomes, xyphidio and furcocercous cercariae. Indoplanorbis exustus shed only echinostome cercariae. B. (D.) s. goniomphalos showed a rather high natural infection rate with O. viverrini, 1.3% in Yang Talat district, and 0.61% in Kamalasai district, in Kalasin Province.

Recuperación e identificación de vibrio choloerae en mariscos provenientes de diferentes mercados de Lima Metropolitana y Callao / Identification and recuperation of vibrio cholerae en sellfish from Lima and Callao market

A fines de 1991, se inició en el Perú una epidemia de cólera de gran inagnitud, en cuanto a morbi-mortalidad y extensión geográfica, que invadió a 19 países produciendo 600,000 casos y más de 6000 muertes. Esta enfermedad ha sido relacionada con el consumo de numerosos productos de pesca, entre ellos los mariscos como vehículos de transmisión del vibrio cholerae. El método utilizado fue el reconocimiento por el ICMSF modificado. Se analizó 104 muestras de mariscos, obteniéndose 0.96 por ciento de positividad correspondiente a la muestra de marisco tipo almeja, comprobándose mediantes pruebas serológicas, pertenecia al serotipo inaba. Asimismo, se comprobó la localización del microorganismo en las valvas del marisco y no en el músculo. También se puso de manifiesto la efectividad del método mediante un segundo enriquecimiento en APA pH=8,6 que proporcionó una mayor selectividad.