ONTOGENETIC MORPHOMETRICS OF CIBICIDOIDES WUELLERSTORFI OBSERVED THROUGH MICROCT SCANNING

Thousands of individual Cibicidoides wuellerstorfi have been collected colonizing the surface of elevated substrates, including biogenic and experimentally deployed materials, ranging from 500 to just over 4,000m water depth in the Pacific Ocean. This unique dataset provides the opportunity to examine the morphology and ontogeny of several specimens of living C. wuellerstorfi. External morphological assessments, such as the test diameter (D), test breadth (B), aperture height (Ah) and width (Aw) have been compared with internal morphologies of planktonic foraminifera resulting in the successful distinction of ontogeny from species specific differences when observing the rate of growth through chamber formation. Based on recent phylogenetic assessments, suggesting morphospecies of C. wuellerstorfi, and the inaccessibility of experimental observations in the deep-sea this study seeks to assess the internal morphologies, visible with MicroCT, to document the ontogenic development, population dynamics, and ecophenotypic variation present within deep-sea C. wuellerstorfi populations. At least four groups (small sinestral, large sinestral, small dextral, and large dextral) of C. wuellerstorfi collected from experimental substrate deployments at Hydrate Ridge will be identified, mounted, and scanned with a Ziess Xradia MicroCT. Digital thin sections will be made to facilitate the measurements of external characteristics, such as: test diameter (D), and breadth (B), aperture height (Ah) and width (Aw), and internal features, including: the diameter of each chamber (Pno. or Uno. for penultimate or ultimate whorl respectively), proloculus diameter (P), diameter of the initial whorl (Iw). These measurements, made using landmark software designed for morphometric applications, will then be used to determine the rate of growth, chamber proportions, umbilicus/test diameter ratio, ultimate/penultimate chamber ratio, penultimate/antepenultimate chamber ratios. It is our hope that this information will reveal the various ontogenetic stages and patterns of C. wuellerstorfi formation which can then be compared to other species.