Abstract A new behavior related to shell care was recently reported for the intertidal hermit crab Clibanarius erythropus (Latreille, 1818) in the Gulf of Cádiz (southwestern Europe). It also has been observed in other species of the diogenid genera Clibanarius Dana, 1952, and Calcinus Dana, 1951, however, it has not been described as an active behavior. In the present study, intertidal hermit crabs from different species and localities were sampled to assess if air-exposure is a shell cleaning behavior restricted to some species of intertidal hermit crabs or if it is a more generalized behavior among species inhabiting intertidal habitats. The results revealed that air-exposure is an active behavior in species of Clibanarius and Calcinus, since we observed it also in Clibanarius albidigitus Nobili, 1901, and Calcinus obscurus Stimpson, 1859, from the Pacific coast of Costa Rica, although not in other intertidal species studied by us. We found interspecific differences in tolerance to physical stress of emerged hermit crabs. This air-exposure tolerance can be interpreted as a physiological adaptation to desiccation stress and is also related to the shell type they inhabit. Also, we provide additional features and details of the air-exposure behavior, combining observations of the first description in 2015 with our new field observations.

Abstract Predatory behavior of the crab Eriphia verrucosa (Forskål, 1775) on the oyster Magallana angulata (Lamarck, 1819), the mussel Mytilus galloprovincialis Lamarck, 1819, the limpet Patella depressa Pennant, 1777, the hermit crab Clibanarius erythropus (Latreille, 1818), the gastropod Phorcus lineatus (da Costa, 1778) and the sea urchin Paracentrotus lividus (Lamarck, 1816) was experimentally studied. Taken into account that the sampled population of E. verrucosa was infected with the parasitic barnacle Sacculina eriphiae Smith, 1906, four predator categories were established regarding crab sex and parasite presence: uninfected and infected males and females, respectively. These four crab categories were fed on the six preys offered, but prey remains suggest that the crab obtains the flesh of each prey using different methods of attack. Irrespective of the prey species, uninfected females consistently presented lower percentages of crab feeding and total consumption. On average, it was found that a significantly higher percentage of crabs feed on M. galloprovincialis, P. depressa and Ph. lineatus than on the other three prey species (chi-squared test, p < 0.05). In terms of mean eaten biomass, the preys most eaten were P. lividus and P. depressa and the least eaten was C. erythropus (ANOVA test, p < 0.05). For crabs feeding on M. galloprovincialis and Ph. lineatus there was a significant positive correlation (p < 0.05) between the predator size and prey size, as well as between the predator size and total prey consumption. According to these results, potential effects of this top predator on intertidal communities are also discussed.

From June 1998 to May 1999, the water temperature, salinity and turbidity, together with the macrofaunal (nekton and hyperbenthos) abundance, biomass and number of species, were estimated in the Guadalquivir estauary at five sampling stations (8, 20, 30, 40 and 50 km from the river mouth). Samples were taken from an anchored boat by using nets with a 1-mm mesh. There was a horizontal salinity gradient along the estuary: monthly mean salinities ranged from 17 to 27 at the outermost sampling station, whilst salinity was rarely higher than 4 in the inner estuary. Water temperature was homogenous throughout the estuary, with maximum values in summer (28°C) and minimum values in winter (10°C). Turbidity was also relatively homogenous throughout the estuary, with a maximum in winter (362 NTU) and a minimum in summer (10 NTU). Maximum turbidity occurred in the zone where seawater and freshwater merge. Results of stepwise multiple regression analysis indicated that both the distance to the river mouth and the freshwater input (in the previous month) from the Alcalá del Río dam in water temperature and turbidity. Salinity explained 50% of the variance in the number of species, whereas salinity and temperature were the environmental variables that controlled the macrofaunal abundance and biomass. Salinity and temperature together explained 75% and 71% of the variance for nekton abundance and biomass, respectively, and 54% and 48% of the variance for the abundance and biomass of hyperbenthos, respectively. Salinity was, in all cases, the individual variable that explained the highest portion of variance.

La temperatura, salinidad y turbidez del agua en el estuario del Guadalquivir, así como la abundancia, biomasa y número de especies de su macrofauna acuática (necton e hiperbentos), se estimaron mensualmente, entre junio de 1997 y mayo de 1999, en cinco estaciones de muestreo a 8, 20, 30, 40 y 50 km de la desembocadura utilizando para la toma de muestras un barco angulero provisto de un arte de pesca con malla de 1 mm de luz. En el estuario existió horizontalmente un marcado gradiente salino: la salinidad media mensual osciló habitualmente entre 17 y 27 en la estación más externa, mientras que en la zona más interna raramente sobrepasó 4. La temperatura fue homogénea en todo el estuario, con máximos estivales (28°C) y mínimos invernales (10°C). La turbidez también fue relativamente homogénea en todo el estuario, con valores máximos invernales (362 UNT) y mínimos principalmente estivales (10 UNT). Los máximos de turbidez coincidieron con la zona de confluencia del agua marina y dulce. Los resultados de los análisis de regresión múltiple por pasos indican que la distancia a la desembocadura y el caudal medio de agua desembalsada (el mes previo) desde la presa de Alcalá del Río (a 110 km de la desembocadura) explican 70% de la varianza de la salinidad, mientras que el caudal desembalsado apenas explica 17% de la varianza observada en la temperatura y la turbidez del agua. La salinidad explica 50% de la varianza del número de especies, mientras que la salinidad y la temperatura son las variables ambientales que controlan la variación de la abundancia y biomasa de la macrofauna estuárica, llegando a explicar 75% y 71% de la varianza de la abundancia y biomasa de la comunidad nectónica, respectivamente, y 54% y 48% de la varianza de la abundancia y biomasa hiperbentónica, respectivamente. La salinidad fue, en todos los casos, la variable que explicó un mayor porcentaje de la varianza.