P3.157 Friday, Jan. 6 Impact of UV-B radiation on the osmoregulatory function of ichthyoplankton larvae of the sea bass Dicentrarchus labrax SUCRÉ, E.; VIDUSSI, F.; MOSTAJIR, B.; CHARMANTIER, G.*; GROUSSET, E.; GROS, R.; LORIN-NEBEL, C.; Univ. Montpellier 2, France; Univ. Montpellier 2, CNRS, France; Univ. Montpellier 2, Medimeer, CNRS, France; Univ. Montpellier 2, France; Univ. Montpellier 2, France; Univ. Montpellier 2, France; Univ. Montpellier 2, France email@example.com
Coastal marine ecosystems are submitted to variations of several parameters, some affected by global change. Among them, ultraviolet-B radiation (UVBR, 280-320 nm) may strongly impact planktonic fish larvae, in which osmoregulation depends on tegumentary ionocytes, mainly located in the trunk and yolk sac skin. As early D. labrax larvae passively drift in the top water column, their ionocytes are exposed to solar radiation. The effects of increased UVBR were investigated on the osmoregulatory function of sea bass larvae in seawater, through nanoosmometric measurements of blood osmolality and through cellular investigations, after exposure to different artificial UVBR treatments. A loss of hypo-osmoregulatory capability occurred in larvae after 2 days of exposure to low (50µW/cm2: 4h L/20h D) and medium (80µW/cm2: 4h L/20h D) UVBR. Compared to control larvae kept in darkness, an increased blood osmolality, an abnormal behavior and high mortalities were detected in larvae exposed to UVBR. At the cellular level, an important decrease in abundance of tegumentary ionocytes and of skin mucous cells was observed after 2 days of exposure to UVBR. In the ionocytes, Na/K-ATPase and the Na/K/2Cl cotransporter were immunolocalized. Compared to controls, fluorescent staining was lower in UVBR-exposed larvae. We hypothesize that the impaired osmoregulation in UVBR-exposed larvae originates from the lower number of ionocytes and mucous cells in their skin.