Meeting Abstract

66.2  Monday, Jan. 6 08:15  Lower thermal tolerance of larvae and adults of the introduced barnacle Megabalanus coccopoma: implications for range limits CRICKENBERGER, S*; WALTHER, K; MORAN, A; Clemson University; Clemson University; University of Hawaii at Manoa scricke@gmail.com

As tropical species make their way into historically temperate climates, cold temperatures will likely set their range limits and determine the extent they can expand out of the tropics. The barnacle Megabalanus coccopoma is native to shorelines from Baja California to Peru and has been introduced to a number of places worldwide including the Atlantic US SE coast, where it was first recorded in 2006. Its current range extends from Ft. Pierce, FL north to Cape Hatteras, NC with seasonal populations found as far north as Kitty Hawk, NC. Larval tolerances to temperature may be a primary factor setting range limits of marine species, but this hypothesis has rarely been tested. To address this question in M. coccopoma, we reared larvae at 22, 19, 16, 13, and 10°C and measured size, protein accumulation, and accumulation of different lipid classes throughout development, as well as testing whether larvae could metamorphose to the cyprid and juvenile stages. We also determined the lower functional temperature (FT₅₀) and lower lethal temperature (LT₅₀) of adult M. coccopoma. Larvae were able to develop through to metamorphosis at temperatures as low as 16°C and larvae reared at 22°C were able to metamorphose into juveniles at temperatures as low as 13°C, suggesting that larvae could successfully develop and metamorphose at temperatures far colder than seen in their current adult range. FT₅₀ estimated the potential northern range limit of M. coccopoma to occur slightly north of their current adult range and our lethal estimate, LT₅₀, predicted the northern range limit much further north. Our results suggest that adult thermal tolerances, in particular thermal sensitivity of function (rather than mortality), contribute most strongly to setting the northern range limit of the barnacle M. coccopoma.