Algunas observaciones sobre el ciclo biológico del anfípodo de agua dulce Echinogammarus longisetosus Pinkster, 1973 (Amphipoda: Gammaridae) en Cataluña(España, N de la península ibérica)

Aspects of the population structure and reproductive biology of the freshwater amphipod Echinogammarus longisetosus were studied in the northeastern Iberian Peninsula (Catalonia, Spain). Amphipods were sampled at approximately monthly intervals from September 1999 to October 2000. Pairs in precopula and ovigerous females were present all year round. The sex ratio was not significantly different from 1:1. Juveniles were abundant in all samples (> 40%). The number of eggs carried by females (N) was related to the size of the females (LP3) (range: 9–68, mean value: 28.2): N = 0.594 LP3 3.141 (n = 80, r 2 = 0.7136, LP3 were measured from the anterior part of the head to the posterior edge of the third pereional segment; total length was approximately 3.5 times greater than LP3 ). The mean embryo diameter was 0.45 mm (mean of measurements of the long and short axes of recently laid eggs). The egg volume increased during development (2 fold by eggs close to hatching).Se estudian varios aspectos relacionados con la estructura poblacional y la biología reproductiva del anfípodo Echinogammarus longisetosus, basándose en muestras obtenidas en el nordeste de la península ibérica (Cataluña, España). Los anfípodos se muestrearon a intervalos de aproximadamente un mes desde septiembre de 1999 hasta octubre de 2000. Se capturaron parejas en precópula y hembras ovígeras en todas las muestras obtenidas durante el período estudiado. La relación de sexos no fue significativamente diferente de 1:1. Los individuos jóvenes eran abundantes en todas las muestras (> 40%). El número de huevos transportados por las hembras ovígeras (N) estaba relacionado con el tamaño de éstas (LP3) (rango: 9–68, valor medio: 28,2): logN= 3,142LP3 – 0,226 (n = 80, r = 0,845; LP3 = longitud del céfalon más los tres primeros pereionitos; la longitud total era aproximadamente 3,5 veces LP3). El diámetro medio de los huevos era de 0,45 mm (media de la longitud del eje mayor y del eje menor de los huevos al principio del desarrollo embrionario). El volumen de los huevos se incrementaba durante el desarrollo embrionario (2 veces en los huevos a punto de eclosionar)

Effects of Different Salinities on Juvenile Growth of Gammarus aequicauda (Malacostraca: Amphipoda)

Gammarus aequicauda is a euryhaline amphipod that is a common inhabitant of brackish environments of theMediterranean Sea. In the Ebro delta, the population density of G. aequicauda is highly variable throughout the year. The main objective of this study is to investigate the effect of salinity on the growth of G. aequicauda juveniles. G. aequicauda embryos and juveniles can survive and grow in the laboratory between 2 psu and 40 psu salinity, depending on the previous acclimation period for the reproductive individuals. Adults acclimated at 34 psu produced embryos and juveniles that survived and developed at salinities between 9 psu and 40 psu; adults acclimated at 9 psu produced embryos and juveniles that could develop in oligohaline conditions. The lower growth rate values were 10.9 μmd−1 and 13.5 μmd−1 at 40 psu and 2 psu, respectively, with the higher values of 18.0 μmd−1 and 18.5 μmd−1 at 19 and 34 psu, respectively

Development and growth of the early juveniles of the spider crab Maja squinado (Brachyura: Majoidea) in an individual culture system

The spider crab Maja squinado is an endangered Mediterranean species; therefore, culturing it successfully is essential for developing restocking programs. The survival, growth and development of post-larval stages (juvenile crabs, C1-C8) were studied using larvae obtained from adult individuals collected in the Catalan Sea. The juvenile crab stages were cultured individually from a megalopal stage using a semi-open recirculation system to obtain the precise growth data of each juvenile crab stage until C8. Development up to C8 at 20ºC lasted 154±10 days. Survival from C1 to C8 was 5.8 %. Moult increment values in cephothoracic length were similar in all the crab stages (21-35 %). Intermoult duration (9±1 in C1-C2 to 51±8 days in C7-C8) increased sharply from juvenile stage 5. Males and females can be distinguished from C4 based on sexual dimorphism in the pleopods and the presence of gonopores. The allometric growth of the pleon is sex-dependent from C4, with females showing positive allometry and males isometric growth. The juvenile growth rate was lower compared with that of the previously studied Atlantic species Maja brachydactyla

Effects of Different Salinities on Juvenile Growth of Gammarus aequicauda (Malacostraca: Amphipoda)

Gammarus aequicauda is a euryhaline amphipod that is a common inhabitant of brackish environments of theMediterranean Sea. In the Ebro delta, the population density of G. aequicauda is highly variable throughout the year. The main objective of this study is to investigate the effect of salinity on the growth of G. aequicauda juveniles. G. aequicauda embryos and juveniles can survive and grow in the laboratory between 2 psu and 40 psu salinity, depending on the previous acclimation period for the reproductive individuals. Adults acclimated at 34 psu produced embryos and juveniles that survived and developed at salinities between 9 psu and 40 psu; adults acclimated at 9 psu produced embryos and juveniles that could develop in oligohaline conditions. The lower growth rate values were 10.9 μmd−1 and 13.5 μmd−1 at 40 psu and 2 psu, respectively, with the higher values of 18.0 μmd−1 and 18.5 μmd−1 at 19 and 34 psu, respectively