First record of invasive caprellid Caprella scaura Templeton , 1836 sensu lato ( Crustacea : Amphipoda : Caprellidae ) from the Iberian Peninsula

The invasive Indian caprellid crustacean Caprella scaura sensu lato has been recorded for the first time in the Iberian Peninsula in July 2005 in the brackish waters of the Roses Bay (Girona, Spain). Its most probable introduction vector was shipping. Some ecological and distributional features are succinctly included.

The specimens were collected in Roses Bay, most of which were found among Bugula neritina (Bryozoa), Mytilus galloprovincialis (Lamarck, 1819) (Bivalvia), and Ficopomatus enigmaticus (Fauvel, 1923) (Polychaeta) from the local fouling communities, in shallow water areas with fluctuating salinity conditions.This record from the Catalan coast reveals that the species has expanded westwards in the Mediterranean Sea.

Material and methods
Samples were taken the 17th of July 2005 at different sites in Roses Bay (42º16'00'' N -3º10'59'' E, Figure 2) from artificial hard substrates at 0.2 m depth.Sampling was collected scraping with a manual scraper a surface of 400 cm 2 .Immediately after the collection samples were fixed in a 5 % formalin solution, preserved in 70 % ethanol, and subsequently processed in the laboratory, including determination of the species composition.Previously, the collected material was washed through a 0.25 mm mesh sieve.All organisms were identified to species or genus, except for Nematoda, Nemertea and Platyhelminthes, which were identified to phylum.
In addition, water temperature and salinity were measured in the water column with a HANNA portable multiparameter.
Observations and measurements were made using a microscope with interfererence contrast optics (Nomarsky) and an Olympus stereomicroscope.Adults, juvenil stages and different appendages were photographed on another Olympus stereomicroscope with a Nikon D50 digital camera.

Results
During a survey at Roses Bay (Girona, Spain) the presence of a dense population of C. scaura has been confirmed for one of sampling stations, which is the first record of this species in the Iberian Peninsula (Figure 1).Specimens of C. scaura were obtained from a sample of the Bugula neritina community, from a unique station (42º15'59.98''N-3º09'20.03''E), in a semi-enclosed area connected to the sea by a narrow channel.More than 2600 organisms were identified from in this sample, belonging to 43 species or higher taxa (Annex 2).The water temperature at that time was 24.5 ºC, and salinity 29.8 PSU.
Diagnosis: Cephalon of both sexes with anteriorly directed spine.In males, pereonites 1 and 2, as well as basis of gnathopod 2 elongated (Figure 1, a).
Female description: Body with anteriorly cephalic spine, with variously developed knobs on some pereonites (Figure 1, b).Length of largest specimen 13,1 mm, smallest ovigerous female 6,2 mm.Antenna 1 slightly smaller than one-half body length.Flagellum with up to 4 fused articles.Length of antenna 2 variable, similar pereonites 1+2.As the male, head convex, lacking rostrum.Occipital spine acute, very well-developed (Figure 1, d).Not swollen at back end.Mouthparts typical of the genus.In adult specimens dorsal processes in pereonites, without ventral spine.Gnathopods 2 basis much shorter than pereon segment 2; propodus of gnathopod 2 not elongated, palm with proximal spine, and small distal tooth (Figure 1, f).Propodus of gnathopod 1 very similar to the males one.Pereopods similar to the males.Gills elliptical, but less elongated than in male and shorter, about half as long as segment 4 or 5 (Figure 1, h).
The collected smaller specimens (< 2.5 mm) differ from adults in some features.Thus, the antena 1 and 2 are of similar length; the cephalosoma is roundish and occipital spine absent; gnathopods 1 of the same length as gnathopods 2; pereon segments roundish and the same length; gills smaller than in adults, and rounded.

Discussion
C. scaura is a caprellid of complicated taxonomy which shows a wide morphological variety.After Templeton´s original description, Mayer (1890, 1903in McCain 1968)  Later, a seventh subspecies was described by Utinomi (1947) from Japan and designated as C. scaura f. hamata.Some years later, Dougherty and Steinberg (1953) examining samples taken from California, revived Stimpson´s (1857) Caprella californica as a valid species.However, Laubitz (1970) synonymized the two forms with ventral spines: C. scaura spinirostris and C. scaura scauroides with C. californica Stimpson, 1857.According to current rules, the specimens collected by Templeton in 1836 from Mauritius are to be named as Caprella scaura scaura (in Krapp et al. 2006).
The specimens collected in Roses Bay are lacking ventral spines, and the morphology agrees with that of Caprella scaura scaura, described by Templeton (1836) from Mauritius, later by McCain (1968) from the northern Atlantic, and more recently by Guerra-García (2003a) from Australia or Krapp et al. (2006) from the Mediterranean.
The presence of this species in European ecosystems is quite new (Annex 1).C. scaura was recorded for the first time in 1994 in the Lagoon of Venice (Mizzan 1999), and was recently reported as very abundant also in the harbour of Ravenna (Sconfietti et al. 2005), and Livorno (Occhipinti-Ambrogi, in Galil et al. 2008).C. scaura is an active filter feeder, which especially benefits from high concentrations of plankton and organic matter in the water column.The specimens from Roses Bay were collected in a semi-enclosed area connected to the sea by a narrow channel.The biotope where the sample was collected belongs to the Bugula neritina community, which agrees with the observations from other authors in other geographical regions (Lin andAlexander 1986, Guerra-García andThiel 2001).Thirty-eight ovigerous females were identified in the sample, indicating that C. scaura might be established in the area, with a reproducing population.
In the last few decades, Caprella scaura sensu lato has widely extended its geographic distribution.The introduction of the species in Mediterranean waters seems to be due to the continuous circulation of yachts; although aquaculture (movement of fish cages) in certain specific zones represent another possible introduction vector (Krapp et al. 2006).Transportation via shipping and aquaculture are the major vectors of global dispersion of alien species (Streftaris et al. 2005).In our case, its presence inside the yachting harbour, suggests that its expansion is at least facilitated by shipping activity.Colonized areas are usually characterized by high population densities (Sconfietti et al. 2005, Costa in Krapp et al. 2006, and Occhipinti-Ambrogi, in Galil et al. 2008).According to these surveys, C. scaura appears to be a strong invader, able to colonise a wide geographical range.Its presence in large numbers in the Roses Bay (max.12925 ind./m 2 ) suggests a probable future invasion along the Iberian Mediterranean coasts and adjacent areas.

Figure 1 .
Figure 1.Caprella scaura (from Roses Bay, Spain) (a) adult male, entire animal; (b) adult female, entire animal; (c) head of adult male; (d) head of adult female; (e) gnathopod 2 of adult male; (f) gnathopod 2 of adult female; (g) gills of adult male; (h) oostegites and gills of adult female.Arrows indicate most prominent characters that can be used to distinguish this species.(Photo by Julián Martínez).

Figure 2 .
Figure 2. Occurrence of Caprella scaura in European coasts and map of the study area (see Annex 1 for details).

Table 1 .
The main differentiating characters of Caprella scaura subspecies.
Annex 2. Species composition and abundance of biota found in the Bugula neritina community sampled in Roses Bay.