The distribution of the sea urchin Arbacia lixula, a warm affinity species, has been expanding in the Mediterranean Sea. To address questions on potential for future success of this species in the region, the thermotolerance of larval development was investigated in context of regional warming. The larvae were reared in present day spawning period (20 °C) and warming conditions (+4 = 24 and +6 = 26 °C). As the calcifying larvae of sea urchins are vulnerable to stunted growth caused by ocean acidification, the impact of lower pH (−0.3 pH units) on larval development was also investigated in combination with warming. Morphological traits of the larvae, post-oral length arms, overall length of larvae and body length, were affected by increased temperature across pH treatments, indicating that for the larvae of southern Mediterranean population here, 24 °C appears to approximate the optimal temperature for development. A slightly negative effect of pH was evident. Increased temperature ameliorated the stunting effect of acidification on growth. The thermal tolerance of A. lixula development overlaps with projections for warming in the region by 2100 and also indicates that this species has acclimatized or adapted its reproductive biology to the broad environmental conditions of the Mediterranean Sea. Due to the broad thermal range (∼10 °C) of development of A. lixula across its distribution, this species is likely to be a winner in the climate change stakes. The broad thermal tolerance of the larvae is likely to assure population connectivity between Mediterranean sub-basins populations. The continued success of A. lixula can have a strong consequences for the ecological structure of Mediterranean rocky habitat.

This study provides for the first time an evaluation\ud of the natural availability of scallop seeds along\ud the coastal area of Taranto (Mediterranean Sea,\ud Southern Italy). To select the best artificial collectors\ud to harvest scallop seeds in this area, cylindrical\ud collectors (Cyl) were compared to traditional\ud ‘Japanese-style onion bags’ (Bag) across three sites.\ud Scallops represented 26.6% of total bivalve recruitment\ud among all collectors (782 ± 331 ind. m-2, \ud The most recruited scallops were Flexopecten glaber\ud and Mimachlamys varia. The white (F. glaber) and\ud black scallops (M. varia) were abundant at all\ud three sites, while the queen scallop, Aequipecten\ud opercularis, was only found at one site. Beyond the\ud recruitment of scallops, numerous other potential\ud commercial bivalve species were collected, including\ud Limaria tuberculata, which was the most abundant\ud bivalve species (33.3% of total recruitment).\ud At all sites, Bag collectors had higher recruitment\ud than Cyl collectors. Scallops recruited in artificial\ud collectors exhibited a multicohort size distribution\ud at most sites, suggesting potentially continuous\ud reproductive activity in the scallop populations.\ud F. glaber, M. varia and L. tuberculata could be good\ud candidates to diversify the aquaculture production\ud because of the availability of seed and their growth\ud rate. Moreover, the farming of these bivalves integrates\ud well with other forms of aquaculture (e.g.\ud mussels), thus potentially offering farmers an additional\ud source of income