Elena Baeza-Rojano

Is the north side of the Strait of Gibraltar more diverse than the south side? A case study using the intertidal peracarids (Crustacea: Malacostraca) associated to the seaweed Corallina elongata

The objectives of this study were to describe the peracaridean fauna associated to the algae Corallina elongata from the Strait of Gibraltar, and explore possible biodiversity and biogeographical patterns of variation along the north–south and Atlantic–Mediterranean axes across the Strait of Gibraltar. Twenty-five stations were selected along the north and south coasts of the Strait to cover the broadest possible range of human pressure and environmental conditions, including both natural rocky shores and artificial breakwaters. The alga Corallina elongata was selected as substrate, and the peracaridean crustaceans were identified to species level and classified in geographical distribution groups. Univariate and multivariate analyses were conducted to explore and confirm patterns of variation. Forty peracarid species were collected, most of them with an Atlantic–Mediterranean distribution (67%) with only the gammarid Parhyale eburnea , being an endemic Mediterranean species. The most common species collected during the present study were the gammarids Hyale stebbingi, Jassa marmorata, Stenothoe monoculoides and Ampithoe spp., the caprellids Caprella grandimana and C. penantis , the isopod Ischyromene lacazei and the tanaid Tanais dulongi . The number of species per station and the diversity index were significantly higher in the stations located along the north side of the Strait of Gibraltar. However, the two-way ANOVA discarded differences between north and south due to the type of substrate (natural versus artificial) and degree of human pressure. Based on peracaridean assemblages, the Strait of Gibraltar behaves as a whole and homogeneous region, with a very similar faunal composition in all stations and there is not a clear gradient of species substitution from the Mediterranean to the Atlantic stations. Provided that we selected the same substrate in all stations, and that statistical analyses revealed that differences between north and south stations were not due to environmental factors such as anthropogenic stress or type of substrate, we should look to historical biogeographical reasons to explain the higher diversity in the north side of the Strait of Gibraltar.

Life history of Caprella grandimana (Crustacea: Amphipoda) reared under laboratory conditions

Abstract Growth, maturity, and reproduction of 112 juveniles of Caprella grandimana obtained from 26 ovigerous females were studied under laboratory conditions at 17°C, and with a 12-h photoperiod. The newly hatched juveniles were transferred to small glass containers and fed with a mixture of diatoms Phaeodactylum tricornutum and Tetraselmis chuii (1:1). After emerging from the brood pouch, caprellids were considered as Instar I (1 mm length). Sexes were not able to be identified until Instar III. In males the moulting interval gradually increased up to Instar X, producing a final instar which lived significantly longer than the previous one. Female intermoult period remained constant until they died. The body length and flagellar articles increased faster in males than females at each instar. Females reached the mature stage at Instar V and VI with a mean of 38.4 days, producing their first brood 10 days later at 49.1 days. The mean of eggs produced by each female was 7.6 and the number of offspring emerged was 5. There was a significant correlation between the average length of the female in each instar and the number of eggs and offspring per brood. This is the first time that a Mediterranean species has been successfully reared under laboratory conditions. These studies are basic for future ecotoxicological research and management of the caprellid species.

The non-native seaweed Asparagopsis armata supports a diverse crustacean assemblage

This is the first study describing the crustacean fauna associated to Asparagopsis armata, a non-native, red seaweed widely distributed along western Mediterranean coasts. First found in Australia and New Zealand, it was introduced naturally through the Strait of Gibraltar and rapidly spread out. A one-year spatio-temporal study (Feb 08-Feb 09) was carried out in the Strait of Gibraltar to characterize the spatio-temporal patterns of the associated crustacean fauna. Maximum biomass of A. armata was measured during April-June, whereas the maximum crustacean abundances were registered from June-October. In total 41 crustacean species were identified. The caprellid Caprella penantis, traditionally associated to non-polluted areas, was more abundant on Tarifa Island (higher values of dissolved oxygen and pH) than in Algeciras (lower oxygen and pH). The gammarid Podocerus variegatus was dominant in Algeciras Bay while Hyale schmidti and Apherusa mediterranea were the most abundant on Tarifa Island. Among isopods, Synisoma nadejda was only found on Tarifa Island. When compared with literature of native algae of the intertidal and shallow sublittoral, the species richness of associated crustaceans was similar in A. armata and the natives. Very little is known about the influence of this algae on altering marine communities, so complete faunistic studies dealing with other groups such as polychaetes or molluscs are necessary to properly address biogeographical, ecological and management programmes dealing with this non-native species.

Spatial patterns and seasonal fluctuations of intertidal macroalgal assemblages from Tarifa Island, southern Spain: relationship with associated Crustacea

The dominant intertidal algal species from Tarifa Island, Strait of Gibraltar, together with the associated peracarid crustacean community, were studied over a two-year period (December 2005-December 2007). Gelidium corneum and Gymnogongrus patens were dominant at the lower levels, close to the subtidal. Valonia utricularis, Osmundea pinnatifida, a turf of Caulacanthus ustulatus and Gelidium spp., Corallina elongata and Jania rubens were distributed in intermediate levels, while Ulva rigida, Chaetomorpha aerea and Fucus spiralis were collected from upper levels. The main intertidal seaweeds of Tarifa Island showed a perennial behaviour, but maximum values of biomass were registered during late spring and beginning of summer for most of species while the highest seawater temperatures were measured in late summer and beginning of autumn. Corallina elongata and Jania rubens, the dominant species which shared a niche at platforms of intermediate levels, showed an opposite behaviour, probably to avoid competence: C. elongata showed higher biomass in April-June and lower values in August-October-December, while biomass of J. rubens was higher in December-February and lower in April-August. Associated crustaceans, including mainly amphipods (gammarids and caprellids) were also present through-out the whole year with similar seasonality to seaweeds. However, crustacean density in the intertidal was not only influenced by distribution of algae as substrate, but also by external factors, such as hydrodynamism, oxygen, weather conditions, competition or predation. The present study constitutes the first baseline study dealing with seasonal fluctuations of algae and associated crustaceans in a protected area of the Strait of Gibraltar, an important biogeographical zone between Europe and Africa and the Mediterranean and Atlantic.

Exploring molecular variation in the cosmopolitan Caprella penantis (Crustacea: Amphipoda): results from RAPD analysis

Eight populations of Caprella penantis , three of Caprella dilatata and two of Caprella andreae , collected from different sites all over the world, were selected for genetic study. Thirteen primers were tested, and the phenogram, based on the similarity coefficient of Nei & Li and the UPGMA method, separated clearly C. dilatata and C. andreae from the populations of C. penantis , supporting the validity of these three species, traditionally considered altogether under the old ‘acutifrons’ complex. Populations of C. penantis (including, at least, forms simulatrix, testudo and lusitanica ) from Spain, Portugal, Morocco, Japan and Brazil were clustered together in the RAPD analysis, indicating that, probably, all the specimens of C. penantis could belong to the same species, in spite of morphological variations in the pleura, gills, robustness and presence/absence of proximal projection in adult male gnathopod 2 propodus. The only population which showed genetic differentiation within the C. penantis complex was the form gibbosa from Coquimbo, Chile. Future analysis based on different molecular approaches (mtDNA, 18S rRNA, ISSR) and additional material from other world areas, should be conducted to confirm these results.

Seasonal fluctuations and dietary analysis of fouling caprellids (Crustacea: Amphipoda) from marinas of southern Spain

Abstract In marinas, native caprellids usually share their habitat with exotic species, and can eventually be replaced by them. The invasive Caprella scaura is spreading quickly and has successfully settled in many marinas of southern Spain, potentially threatening the native taxa. We selected two marinas (El Rompido, Huelva and La Línea, Cádiz) in which C. scaura has not yet been found, in order to explore the seasonal dynamic patterns of the resident species before the arrival of the non-native species. Sampling was carried out bimonthly from July 2010 to July 2011. Two caprellid species were recorded, Caprella dilatata and C. equilibra. In El Rompido, both caprellids were found on two substrates (the bryozoan Bugula neritina and the hydroid Ectopleura crocea), whereas in La Línea, B. neritina hosted only C. equilibra, and C. dilatata was absent. Caprella dilatata showed maximum densities in July, with a second peak of abundance in November, and was absent during the winter (January–March). Caprella equilibra showed differences in abundance patterns, body length and fecundity between the two marinas, probably due to differences in environmental measures between the marinas. The dominant component of the diet of the two species was detritus, followed by copepods, which were more abundant in specimens collected from E. crocea, suggesting the possibility of cleptocommensalist behaviour.

Taxonomy and ecology of some gammaridean species (Crustacea: Amphipoda) from Tarifa Island, southern Spain

On Tarifa Island (Strait of Gibraltar) several amphipod species were studied from intertidal algae: Ampithoe ferox , Apherusa mediterranea , Hyale spinidactyla , Hyale cf. youngi and Jassa cadetta . The allometric growth of gnathopod 2 in male is demonstrated for A. ferox. Jassa cadetta had been recorded previously only from the northern Adriatic Sea, while Hyale spinidactyla and Hyale cf. youngi had been only known from the Atlantic Ocean. Along the intertidal area, A. mediterranea and J. cadetta were dominant in the low levels located near the infralittoral area, while A. ferox , Hyale spinidactyla and Hyale cf. youngi were distributed in intermediate and upper levels, closer to the supralittoral zone. All the species showed the maximum peaks of abundance from April to October, coinciding with the maximum seawater temperatures.