Handling, reproducing and cryopreserving five European sea Urchins (Echinodermata, Klein, 1778) for biodiversity conservation purposes

Financiaciado para publicación en acceso aberto: Universidade de Vigo/CISUGIn this work, five local sea urchin species found in European waters were studied. Four were regular species: Sphaerechinus granularis, Psammechinus miliaris, Echinus esculentus (Linnaeus, 1758) and the edible sea urchin Paracentrotus lividus; and one was an irregular species, Echinocardium cordatum. These five species of sea urchins have been studied regarding their fertility, toxicity of cryoprotecting agents, cryopreservation of different cell types and chilling injury. The baseline fertility is similar in P. lividus, P. miliaris and S. granularis. Nonetheless, the sperm:egg ratio, contact time and development of the fertilization envelope would need to be studied further on a case-by-case basis. Sperm can be maintained inactively in the gonad (4 °C), and oocytes also maintain quality in sea water (4 °C), even after 72 h. Sperm was cryopreserved for four species with some post-thaw intra specific variability, and embryo cryopreservation was only possible for S. granularis. Overall, this study provided a wider vision of the biology and reproduction of these species that will help us develop tools for their biodiversity conservation through cryopreservation.Fundacion Biodiversida

Determining Obelia spp. diversity and population dynamics in Thau lagoon (Northwestern Mediterranean Sea, France).

The jellyfish Obelia belongs to the family Campanulariidae (Hydrozoa, Leptomedusae), an important and widely distributed family of hydrozoans. Obelia is a very popular and widespread medusa, however first report on its complete life cycle was only published in the late nineties in Northern Japan. This is probably due to its size, as the medusa umbrella diameter is lower than 1mm. This Hydrozoa presents a bentho-pelagic life cycle with both polyp and medusa stages. In Thau lagoon, Northwestern Mediterranean Sea, populations of Obelia occur each year. Some polyps colonies were identified and sampled in the lagoon on Zostera noltii leaves, indicating that the populations realise their full development cycle within the lagoon. Morphological and genetical (COI) approaches, on both polyps and medusae, have revealed that main populations are composed by O. dichotoma individuals (side branches typically irregular in length; hydroteca bell-shaped, usually not very deep, thin walled, often thrown into fine longitudinal folds; hydrotecal rim with smooth or with shallow cusps \u2013crenate, slightly flared; diaphragm transverse to oblique) but that O. bidentata (lateral branches roughly in right angles pairs are given on both sides; slightly oblique diaphragm; hydrotecal rim with bimucronate cusps) is also present in lower abundances. An in situ pelagic monitoring every two weeks since 2008 have allowed understanding the populations dynamics of the genus and the environmental factors that seemed to be particularly appropriated for promoting optimum growth conditions. Baseline information regarding seasonal cycles and historical abundances were provided from a 8 years monitoring, which has allowed detecting blooms. Indeed, the medusae were found at very low densities during the study period with main abundances under 5 ind.m-3, in accordance to previous reports for Obelia spp. medusae around the world. Nevertheless, 2 exceptional events took place in June 2008 and May 2013 were blooms reached 1232 and 660 ind.m-3 respectively. Such data raise questions regarding the potential importance of this small and understudied hydrozoa in the pelagic community of Thau lagoon. Consequently, it is necessary to improve the available databases documenting medusae blooms, as this will provide baseline information about these little-studied events