Are elemental and strontium isotopic microchemistry of otolith and histomorphometrical characteristics of vertebral bone useful to resolve the eel angilla obscura status in Lalolalo lake in Wallis Island?
Abstract
Otolith Sr/Ca, Ba/Ca and 87 Sr/ 86 Sr ratios and vertebral bone histomorphometry were used to investigate the life-history of Anguilla obscura eels from an enclosed lake, Lalolalo (Wallis Island in the Pacific), with no apparent connection with the sea. 87 Sr/ 86 Sr isotopic ratio from the core region gives evidence of indisputable marine origin of eels caught in the lake suggesting that underground connections between the lake and the sea exist. Sr/Ca and Ba/Ca ratios recorded after the elver mark are undifferentiated from seawater ones, thus limiting their used as marker of entrance in the lake and movement. However, 87 Sr/ 86 Sr isotopic ratio demonstrated that: 1) eels enter in the lake just after their metamorphosis and spend their entire adult life in the lake and 2) the lake chemistry is consistent with 1 % seawater-like contribution and 99 % basalt weathering and/or geothermal spring contribution. The vertebrae do not show a particular demineralization of bone matrix (45-52 %). Reversely, the study of bone compactness shows an important loss of bone that favors the hypothesis of a genital maturation that arises in the ecological state of the lake.