Spatial variation in age structure among colonies of a marine snake: the influence of ectothermy.

Several tetrapod lineages that have evolved to exploit marine environments (e.g. seals, seabirds, sea kraits) continue to rely upon land for reproduction and, thus, form dense colonies on suitable islands. In birds and mammals (endotherms), the offspring cannot survive without their parents. Terrestrial colonies contain all age classes. In reptiles (ectotherms), this constraint is relaxed, because offspring are independent from birth. Hence, each age class has the potential to select sites with characteristics that favour them. Our studies of sea snakes (sea kraits) in the lagoon of New Caledonia reveal marked spatial heterogeneity in age structure among colonies. Sea krait colonies exhibit the endothermic 'seal-seabird' pattern (mixed-age classes within populations) only where the lagoon is narrow. Where the lagoon is wide, most snake colonies are comprised primarily of a single age cohort. Nurseries are located near the coast, adult colonies offshore and mixed colonies in-between. We suggest that ectothermy allows individuals to utilize habitats that are best suited to their own ecological requirements, a flexibility not available to endothermic marine taxa with obligate parental care.

Coastal nurseries and their importance for conservation of sea kraits.

Destruction and pollution of coral reefs threaten these marine biodiversity hot stops which shelter more than two thirds of sea snake species. Notably, in many coral reef ecosystems of the Western Pacific Ocean, large populations of sea kraits (amphibious sea snakes) have drastically declined during the past three decades. Protecting remaining healthy populations is thus essential. In New Caledonia, coral reefs shelter numerous sea krait colonies spread throughout an immense lagoon (24,000 km2). Sea kraits feed on coral fish but lay their eggs on land. However, ecological information on reproduction and juveniles is extremely fragmentary, precluding protection of key habitats for reproduction. Our 10 years mark recapture study on Yellow sea kraits (L. saintgironsi >8,700 individuals marked) revealed that most neonates aggregate in highly localized coastal sites, where they feed and grow during several months before dispersal. Hundreds of females emigrate seasonally from remote populations (>50 km away) to lay their eggs in these coastal nurseries, and then return home. Protecting these nurseries is a priority to maintain recruitment rate, and to retain sea krait populations in the future.

Anguilliform fish reveal large scale contamination by mine trace elements in the coral reefs of New Caledonia.

Due to intensive mining activity, increasing urbanization and industrialization, vast amounts of contaminants are discharged into the lagoon of New Caledonia, one of the largest continuous coral reef systems and a major biodiversity hotspot. The levels of 11 trace element concentrations were examined in the muscles of predator fish in the south-western lagoon (moray eels and congers). These species are sedentary, widespread, abundant, and they are easily collected using a sea snake sampling technique. We found the highest mean and maximal concentrations of different trace elements ever found in coral fish, notably regarding trace elements typical from mining activity (e.g., mean values for Cr and Ni, respectively: 5.53 ± 6.99 µg g(-1) [max, 35.7 µg g(-1)] and 2.84 ± 3.38 µg g(-1) [max, 18.0 µg g(-1)]). Results show that important trace element contamination extends throughout the lagoon to the barrier reef, following a concentration gradient from the oldest nickel factory (Nouméa).

Evidence for a role of GABA- and glutamate-gated chloride channels in olfactory memory.

In the honeybee, we investigated the role of transmissions mediated by GABA-gated chloride channels and glutamate-gated chloride channels (GluCls) of the mushroom bodies (MBs) on olfactory learning using a single-trial olfactory conditioning paradigm. The GABAergic antagonist picrotoxin (PTX) or the GluCl antagonist L-trans-pyrrolidine-2,4-dicarboxylic acid (L-trans-PDC) was injected alone or in combination into the α-lobes of MBs. PTX impaired early long-term olfactory memory when injected before conditioning or before testing. L-trans-PDC alone induced no significant effect on learning and memory but induced a less specific response to the conditioned odor. When injected before PTX, L-trans-PDC was able to modulate PTX effects. These results emphasize the role of MB GABA-gated chloride channels in consolidation processes and strongly support that GluCls are involved in the perception of the conditioned stimulus.