No abstract

An Octopus briareus specimen was recorded off Port Sisal, Yucatán, Mexico. This finding represents the first record of O. briareus in the southern Gulf of Mexico, expanding the currently known westernmost distribution area for this species on the American continent. The specimen was captured by scientific divers performing routine maintenance at underwater facilities in the area of the discovery. The collected specimen was an adult female weighing 25.3 g. The presence of O. briareus could be related to changes in the environmental conditions in the Caribbean Sea and the Gulf of Mexico.

The e¡ect of bio¢lms of the benthic diatom Navicula incerta and of the dissolved organic carbon (DOC) they produce was evaluated on the growth and survival of Lytechinus pictus postlarvae during metamorphosis. In each container, 300 postlarvae were exposed to bio¢lms beginning on days 1, 3 and 6 of metamorphosis, using three replicates and a blank containing only ¢ltered water. The experiments were run for 15 and 18 days in 500-mL containers with daily water changes. We measured 30 postlarvae from each container and counted all organisms on days 1, 3, 9 and 15; DOC was quanti¢ed on days 3, 6 and 9. A second experiment was conducted to evaluate whether the presence of diatoms or the DOC they produced improved postlarval development. Five assays were performed in triplicate: a positive control with bio¢lms, a negative control with ¢ltered water and three treatments with DOC-enriched water from a N. incerta culture supplied on days 1, 4 and 8. In both experiments, postlarvae attained the largest size and highest survival in the treatments with the bio-¢lm. The results indicate that the increase in postlarval size and survival was due to the DOC produced by the diatoms and not by their presence alone.