SHAKING UP PHYLOGENETIC TREES: UTILIZING MOLECULAR ANALYSIS AND MICROCT TO ASSESS FORAMINIFERAL MORPHOLOGY

Benthic foraminifera are among the most numerous organisms of the deep sea, are globally distributed, and have an impressive geologic record. Although studies of foraminifera have a long history, many questions remain about the biology and ecology of taxa that live in deep-ocean habitats, including mobility, ecophenotypic variation, and reproductive mechanisms. Given the infeasibility of long term first-hand observations or in-situ experimentation in the deep sea, detailed analysis of morphology and genetics can provide critical information about the lives of deep-sea foraminifera. Through the use of a combined MicroCT imaging and destructive analysis, such as SSU rDNA, a new approach to morphology-based taxonomy in benthic foraminifera is being established. Results are yielding information about taxonomic relationships and morphologic plasticity relevant to studies of diversity, paleoecology, and biostratigraphy. Cibicidoides wuellerstorfi, an epibenthic species of foraminifera, is commonly used in geochemical and paleoceanographic reconstructions. Recent investigations examining SSU rDNA of C. wuellerstorfi have shown a wider range of morphologic characteristics than traditionally recognized, suggesting greater morphological plasticity than previously acknowledged.

Early morphologic development of C. wuellerstorfi is hidden within its test and very little is known about the lifespan, mobility, and even reproductive mechanisms of this foraminifera. MicroCT scanning is the only non-destructive approach currently available that facilitates clear identification of an initial chamber (indicating mode of reproduction). MicroCT imaging Cibicidoides wuellerstorfi (epifaunal) and Uvigerina peregrina (infaunal) and sequencing their DNA will allow for a comparison between foraminifera microhabitats, morphology, and genetic variation of two benthic foraminiferal species most widely used in paleoceanography. Morphologic description coupled with SSU rDNA analysis provides a powerful combination that will inform ecological assessments and taxonomic classifications. MicroCT scans and SSU rDNA documentation shake up phylogenetic trees and allow for exploration into population and genetic variability of these deep-sea organisms and their fossil assemblages.