Trace metal levels in the edible tissues of sea cucumbers (Holothuria tubulosa and Holothuria polii) from Sardinia (Western Mediterranean)

Sea cucumbers represent an important part of the diet in Asian and Pacific regions and are also used in traditional medicine. These habits have led to the overexploitation of local sea cucumber populations in these areas, driving the pursuit of new stock regions, such as Mediterranean areas. In Italy, contrarily to that observed for other Mediterranean countries, the exploitation of sea cucumber stocks is not extensive, which opens a new market opportunity. Thus, from a food safety perspective, this work aims at reporting the first assessment of trace metal concentrations (As, Cd, Cr, Cu, Hg, Ni, Pb) in the edible tissues of Holothuria polii and Holoturia tubulosa collected in Sardinia, the second-largest island in the Mediterranean Sea. Metal concentrations found in H. polii were generally higher than in H. tubulosa. However, in both species, they were lower than those reported for other areas of the Western Mediterranean. Cd, Hg, and Pb were below the limits established for seafood in Europe. As concentrations were in the range of those measured in other commercial seafood species in the Mediterranean. Thus, these species may be harvested and traded to fulfil the demands of local and international markets.

Gonadal development of the holothurian Holothuria polii (Delle Chiaje, 1823) in spawning period at the Aegean Sea (Mediterranean Sea)

The Mediterranean sea cucumbers including Holothuria polii has become commercially important in international trade due to the high demand of consumers from Far East countries. Sea cucumbers fisheries is a valuable income for the regional fishermen but natural stocks endangered by overfishing in recent years. Fisheries regulations and aquaculture studies are important precautions for preserving natural stocks. All these efforts are based on reproduction biology of this species which slightly differed among regions. In this study, the reproduction biology including morphological characteristics, gonadosomatic index and gonadal development stages of H.polii at the eastern coast of Aegean Sea (Izmir, Turkey) were investigated during the reproduction (spawning) period from July to October 2018. Gonads and gonad sections of 60 sea cucumbers (120.60 ± 19.56 g) have been observed by macroscopic and microscopic inspections. Three gonadal development stages have been identified by histologic observations as mature (III), spawning (IV) and post-spawning stage (V) in gonadal tubules. Results indicate that both female and male gonads are at mature and spawning stage in July and all gonads are at post-spawning stage in October. The mean gonad weight was 12.53 ± 1.33 g at the beginning of the spawning period (July) and 1.87 ± 0.58 g at the end of the spawning period (October). Gonadosomatic index decreased from 17.53 ± 0.02% (July) to 3.37 ± 0.01% (October) after spawning. The gonadosomatic index, gonad weight, and spawning were related to the seawater temperature. According to this study, the spawning period of H.polii at the eastern coasts of the Aegean Sea starts in July and completely ends in October. As a result, the data related to the reproduction biology in spawning period of H.polii would guide stock management and artificial breeding of this species under controlled conditions.