Meeting Abstract

68.2  Jan. 7  Does larval biology limit the vertical distribution of the deep-sea mussel Bathymodiolus childressi? ARELLANO, S.M..; University of Oregon, Charleston arellano@uoregon.edu

Bathymodiolus childressi is a mixotrophic mussel harboring methanotrophic endosymbionts in its gills and is known from hydrocarbon seeps in the Gulf of Mexico, ranging in depth from 546 to 2222 m. Population genetics reveal no differentiation throughout the Gulf of Mexico (GoM), suggesting widespread larval dispersal in this region. However, the larval biology that makes such widespread dispersal possible has not been investigated. Here we begin to answer: 1) Which embryological and physiological factors limit the vertical distribution of B. childressi larvae? and 2) Do energetics limit vertical migration by B. childressi larvae to the productive surface waters? To do so, we induced spawning via serotonin injection to adult B. childressi maintained in the lab. Induction of spawning was successful as early as September and continued through March. Laboratory cultures maintained at 7-8 oC developed at an average rate of one division per 4-9 hours through the 32-cell stage. Larvae hatched by 36 to 48 hours and developed a D-shell by day 8; however, development could be delayed so that the larval shell did not begin formation until day 12. Cultures were maintained for up to two weeks, but never metamorphosed in the lab. We used a MOCNESS plankton tow throughout the water column above the GoM seeps to collect plankton at various times of the year. B. childressi larvae are present as shallow as 200 m in winter months. Although survival of trocophore larvae decreases with increasing temperatures, thermal tolerances are within the range of temperatures found in the Gulf of Mexico during the spawning season, indicating that temperature does not limit vertical migration. Empirical estimates of metabolic rate and swimming speed of B. childressi larvae were also conducted to test an energetic model that estimates vertical migration potential in deep-sea larvae.