Therefore, the observed hydrographic conditions allow us to hypothesize that the second megalopa found in the Mallorca slope could have been transported in the stream of the NC. On the other hand, the cyclonic circulation at the Balearic Sea was observed to be more intense in October 2011, when the BC was strengthened by the NC due to the presence of a strong anticyclonic gyre in the south part of the Mallorca channel that avoided neither the normal circulation southwards of the NC nor the clear northward progress of recent Atlantic Waters (Fig. In this case, human-mediated vectors such as maritime transport seem a reasonable explanation. Zoeal development in open waters requires between 3 and 4 weeks before metamorphosis to the megalopal stage (Epifanio 2019), thus even though natural dispersion could be plausible, it seems less likely due to the long distance that the dispersion entails in the NC stream. The low hydrographic dynamics found in the Menorca slope suggest that the first megalopa could have been transported to the area by alternative vectors. In July 2005, the most intense hydrographic feature was the circulation of recent Atlantic Water that progressed northwards through the Ibiza Channel and recirculated around Ibiza through the Mallorca channel whilst at the north of the archipelago, the dynamics, not so clearly defined, corresponded to the cyclonic circulation characteristic of the Balearic Sea (Fig. The temperature in the study area was between 23 and 24 ✬ in both periods (Fig. SST and SSH with derived surface currents observed in the sampling days are shown in Fig. Both specimens were clearly identified by their pointed rostrum with the horizontal placement of the rostral spine, the abdominal pleopods, the appearance of chelae and the cornua project from the posterior edge of cephalothorax (Costlow and Bookhout 1959). The second larva, captured in October 2011, was also identified as a megalopa, although neither biological nor biometric information was obtained (Carbonell et al. Morphological features of the first megalopa were registered, including a carapace length of 3 mm and developed pleopods (Fig. sapidus following the description by Costlow and Bookhout ( 1959), in which the dorsal carapace and the ventral posterior sternum aspects, with a pair of prominent cornua on the posterior margin of the 5th sterna segment, distinguish the species from other Portunus spp. sapidus adult records in the NW Mediterranean Sea, a through full revision of the decapod larvae stored at the COB (IEO-CSIC) was performed. However, due to the increasing number of C. The first specimen, captured in July 2005, was initially published as Portunus spp. Moreover, the analyzed environmental conditions and the identified larval stages give the opportunity to explore potential introduction pathways and the life history in new invaded areas. sapidus prior to the first citation of the species in the Balearic sub-basin. Here, we report the collection of larvae of C. However, the species was not found in the Balearic Archipelago until 2017 (Garcia et al. Increasing abundances and established populations have been documented along the subregion in the last decade (Karachle et al. sapidus have been sporadically recorded since 2004 (Giménez Casalduero et al. In the Mediterranean coast of the Iberian Peninsula, adults of C. It is considered one of the most invasive species in the Mediterranean Sea (Streftaris and Zenetos 2006), where it was cited for the first time in 1947 in Hellenic waters (Serbetis 1959), although fishermen observations date back to 1935 in the Gulf of Thessaloniki (Nehring 2011). The blue crab Callinectes sapidus Rathbun, 1896 is native to the West Atlantic, from Canada to Argentina (Squires 1990), and typically found in brackish waters.
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