The invasive ctenophore, Mnemiopsis leidyi, which had its first mass occurrence in Limfjorden (Denmark) . During that period, copepods and other mesozooplankton organisms were virtually absent while ciliates were a substantial part of the zooplankton biomass. In "pre-Mnemiopsis years", there seems to have been large variability in the grazing impact on zooplankton depending on the seasonal abundance of A. aurita. With the addition of the second carnivore M. leidyi, however, additional predation pressure caused the zooplankton stocks to be severely depressed throughout 2008 and 2009 when copepods and cladocerans no longer showed the high seasonal peaks in abundance typical of previous years.
Variación genética deRESUMEN. Dentro de la familia Cambaridae el género Procambarus es especialmente importante debido al número de especies que contiene y a su amplia distribución en el continente americano. Procambarus (Austrocambarus) llamasi es una especie endémica de la península de Yucatán, distribuyéndose en cuerpos de agua epicontinentales, incluyendo lagos, pantanos y planicies de inundación, que pueden estar relativamente aislados. Debido a la naturaleza fragmentada de su hábitat se esperaría encontrar poblaciones muy estructuradas con haplotipos únicos. Para describir la variación genética de las diferentes poblaciones de P. llamasi y su patrón de distribución se realizó un análisis filogeográfico usando el gen mitocondrial COI. Se secuenció un fragmento de 643 pares de bases de 53 organismos en diez poblaciones. Se identificaron los diferentes haplotipos y se construyó una red usando parsimonia estadística para realizar un análisis de clados anidados. Se encontró un total de 14 sitios variables, de los cuales 12 fueron informativos; todos los cambios nucleotídicos fueron transiciones y la diversidad nucleotídica fue de π = 0,0045. Se encontraron 10 haplotipos con una diversidad haplotípica de HD = 0,532, con uno de ellos ampliamente distribuido. El análisis de clados anidados muestra que los haplotipos actuales son el resultado de una expansión contigua del intervalo de distribución, sugiriendo que el origen de la expansión se ubicó en el sector sur de la península. Esto puede ocurrir debido a las inundaciones estacionales en la región, que pueden crear conexiones temporales entre poblaciones. Palabras clave: Procambarus llamasi, variación poblacional, COI, dispersión, península de Yucatán, México. Genetic variation inProcambarus llamasi (Crustacea: Decapoda: Cambaridae) from the Yucatan Peninsula: evidence of connectivity in a fragmented landscape ABSTRACT. Within the family Cambaridae, the genus Procambarus is especially important due to the number of species it contains and its wide distribution in the American Continent. Procambarus (Austrocambarus) llamasi is endemic to the Yucatan Peninsula, distributed in epicontinental water bodies, including lakes, marshes and flood plains, which may be relatively isolated. Due to the fragmented nature of its habitat, it might be expected to find highly structured populations with unique haplotypes. To describe the genetic variation of the different populations of P. llamasi and their distribution pattern, a phylogeographic analysis was performed using the mitochondrial COI gene. A 643 base pair fragment was sequenced from 53 individuals of ten populations. Different haplotypes were identified and a haplotype network was built using statistical parsimony for nested clade analysis. A total of 14 variable sites were found, 12 of which were informative; all nucleotide changes were transitions and nucleotide diversity was π = 0.0045. Ten haplotypes were found with a diversity of HD = 0.532, with one of them widely distributed. The nested clade analysis shows tha...
RESUMEN. Se comunica el hallazgo de una nueva especie de origen sur Pacífico, Pinnixa valdiviensis Rathbun, 1907 (Decapoda, Pinnotheridae) en bahía de San Julián (49°17'48"S, 67°43'30"W), provincia de Santa Cruz, Argentina. Se registra la relación de comensalismo existente con el equiúrido Pinuca chilensis (Max Müller, 1852). Se amplía su área de distribución geográfica hacia el océano Atlántico sudoccidental y se incorpora como una nueva especie para el mar argentino. Se proporcionan datos morfométricos.
Forest soils respond dramatically to management changes compared to other soils influenced by different land-use forms. This work aimed to compare the soil conditions in four different zones in a temperate forest in a biosphere reserve in Mexico, using a minimum data set (MDS) based on volcanic soils properties to develop a soil quality index (SQI). For this purpose, two different MDSs were used, one obtained from an expert opinion and the other through a multivariate principal component analysis (PCA). The soil quality assessment was conducted in a biosphere reserve in Mexico, where volcanic soils predominate. Four different areas were studied. Overall, six different types of SQI were calculated for each area, for which linear and nonlinear functions were used and the additive and weighted method. The six SQI showed a significant difference between the four areas of study. The zone with the highest SQI values was the zone with a preserved pine forest, followed by the zone with a pine forest managed by the population, and the zones with a pine forest and grassland in recovery showed the lowest SQI. The linear score indices obtained by the PCA indicated the better ability to differentiate the calculated SQI values, which would provide information to contribute to the stakeholder management and decision making in the protection, conservation and management of the ecosystems present in the biosphere reserve.
A new species of crayfish is described from the Cave of Sótano de La Lucha, in the border between the Mexican states of Chiapas and Oaxaca. The new species is completely adapted to the cave environment with reduced eyes lacking cornea and visual pigments, an almost unpigmented body and elongated appendages. We also report on crayfish populations from the "Lagunas de Montebello" area, which fit well the description of Procambarus pilosimanus (Ortmann, 1906), a heretofore problematic species in southern Mexico.
Eurytemora americana and Acartia tonsa are two of the most important copepods from the Bahía Blanca estuary plankton. In this study 30 females from each species were sorted from seasonal and recently preserved zooplankton samples. Prosome length (PL), width (PW) and height (PH) and urosome length (UL) and width (UW) were measured and subsequently the following ratios determined: PL:PW, PL:PH, PW:PH and PL:UL. Individual volumes for E. americana and A. tonsa females were estimated following the morphometric method in order to obtain individual biomass values for rapid application in the future. The formula for individual volume was: V (mm 3 )= π (PL PW PH)/6 + π (UL UW 2 )/4. Regression tests were conducted for both species utilizing individual volume vs prosome length or width as independent variables and fitting data to a power model. Covariance analysis and single comparison between regression lines were used in order to evaluate the temporal behavior of these relationships. PL:UL was the best ratio for separating one species from the other, being 1.46 for E. americana and 3.53 for A. tonsa. Average individual volume and std. error estimated for E. americana and A. tonsa were 0.0749 (± 0.0097) mm 3 and 0.0399 (± 0.0049) mm 3 , respectively. Despite their similar size, strong differences between
Diversity and distribution of stomatopod and decapod crustaceans in the estuary of Gallegos river (Santa Cruz-Argentina). We studied the diversity and distribution of stomatopod and decapod crustaceans from the estuary of Gallegos River, Argentina. Decapods were found at all stations, while stomatopods and anomurans were found only at the exterior station. There was a marked difference in diversity, the exterior station being more diverse. A total of six species were found (five decapods and one stomatopod), a low value when compared with the surrounding sea. Abundance was variable at stations, depending on the type of bottom. Rev. Biol. Trop. 55 (Suppl.
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