The More the Better: Genetic Monitoring of Paracentrotus lividus (Lamarck, 1816) Experimental Restockings in Sardinia (Western Mediterranean Sea)

Paracentrotus lividus is a widely distributed species in the Mediterranean Sea and North-East Atlantic Ocean, where it plays an important ecological and commercial role. The growing demand for its delicious gonads has rapidly led to the overexploitation of the natural populations around Sardinia (western Mediterranean). The present research aimed at understanding the population genetics of the species within the area, and at gathering data on the juveniles produced in an experimental 'conservation hatchery' facility. A multilocus approach was used, combining mitochondrial genes (COI and Cytb) and microsatellite markers. Overall, both the microsatellites and mitochondrial results indicate that the hatchery-produced juveniles were less genetically diverse and significantly divergent from the wild populations, most likely because of a bottleneck effect due to the insufficient number of parental breeders used. As concerns the wild populations, despite the high harvesting pressure, they still have a good quantity of genetic variation. A weak overall differentiation was found, suggesting extensive gene flow among the sites. However, the differentiation in the pairwise comparisons between the wild Sardinian samples was found to be significant with regard to the mitochondrial sequences, to be further investigated with additional studies. These data provide the scientific knowledge necessary to inform future management actions and to improve future aquaculture protocols.

Blue-Green Algae as Stimulating and Attractive Feeding Substrates for a Mediterranean Commercial Sea Urchin Species, Paracentrotus lividus

Sea urchins rely on chemical senses to localize suitable food resources, therefore representing model species for chemosensory studies. In the present study, we investigated the chemical sensitivity of the Mediterranean sea urchin Paracentrotus lividus to the blue-green alga Aphanizomenon flos-aquae, namely "Klamath", and to a few amino acids chosen from the biochemical composition of the same algae. To this end, we used the "urchinogram" method, which estimates the movement rate of the sea urchins in response to chemicals. Our results showed that Klamath represents a strong chemical stimulus for P. lividus as it elicits an overall movement of spines, pedicellariae, and tube feet coupled, in some cases, to a coordinated locomotion of the animals. Sea urchins also displayed a sensitivity, even if to a lesser extent, to leucine, threonine, arginine, and proline, thus implying that the amino acids contained in Klamath may account, at least in part, for the stimulating effects exerted by the whole algae. Additionally, our results show that Klamath, as well as spirulina, another blue-green alga with high nutritional value, is very attractive for this sea urchin species. These findings gain further importance considering the potential profit of echinoderms for commercial consumers and their growing role in aquaculture. Klamath and spirulina combine high nutritional profiles with attractive and stimulating abilities and may be considered potential valuable feed supplements in sea urchin aquaculture.

Population dynamics and fecundity estimates of Long-spined Black Sea Urchin Diadema savignyi (Audouin, 1890) from the Red Sea, Saudi Arabia

Sea Urchin is not only the crucial keystone species for the coral reef restoration but also it has antimicrobial and anti-cancer activities. This study undertaken to focus on length weight relationship, size fecundity distribution and the estimation of fecundity from the long-spined Sea Urchin, Diadema savignyi at the coastal water of the middle Red Sea, Saudi Arabia. A total of 633 specimen of D. savignyi has been collected from the coastal water of Obhur Creak during the sampling time. In each species, total length (TL) measured as a TW = 11.908 × 0.9995 (R² = 0.8975) through the linear regression graph and digital slide callipers and, individual body weight estimated by the digital balance. The natural and fishing mortality 2.02/yr and 0.19/yr respectively has documented from study area. The Asymptotic length value (L∞) (cm) were estimated 7.35 where the growth coefficient (K) was 0.67 from the monthly length-frequency numeric data by using FAO FISAT II software for generating and estimating the population parameters and age. However, the recruitment pattern was observed to be increased gradually with the maximum recruitment peak between the months of September and October 2021. Therefore, the estimation of fecundity varied from 49,226 ova (total length 3.1 cm) to 466,133 ova (total length 6.8). As a result, analysis of the relationship between the absolute fecundity (F) and total length (TL), and between the fecundity and drained body weight (DW), revealed a linear regression model with a positive and significant relationship at p < 0.05. This is the first approach to study the detailed population dynamic of the ecologically and economically important tropical long spine sea urchin (D. savignyi) endemic to the region. However, the result so far obtained from this research would greatly be useful towards the understanding of the detailed population structure and growth patterns that will undoubtedly help us to develop captive breeding, seed production, culture protocols, conservation strategies and isolation bioactive compounds of this high-valued species incommensurate with national and international perspectives.