A FINE STRUCTURAL COMPARISON OF SELECTED CLADE E ALLOGROMIID FORAMINIFERA: COULD ULTRASTRUCTURE HOLD PHYLOGENETIC CLUES?

The allogromiid (sensu lato) Foraminifera represent a seemingly inconspicuous taxonomic group because of their limited presence in the fossil record, apparent absence in sediments, and morphological simplicity. At the fine structural level, allgromiids possess diverse, intricate shell architectures that may in fact hold phylogenetic clues. Recent molecular work (SSU rDNA) by others has delineated thirteen genetic clades of allogromiids, most of which unite taxa that do not share a common general morphology. The SSU rDNA analyses suggest members of ‘Clade E’are related but poorly resolved and to date, there are no know gross morphological characters that unite them. Here, we present a comparison of fine structural morphology of three undescribed Clade E allogromiid taxa (Psammophaga sp., the, ‘Fusiform’ and ‘Fruitcake’). We examined features of the test (composition of agglutinated materials, inner organic lining), cell body and nucleus using both transmission and scanning electron microscopy. The gross morphology and the fine structure of the test, wall and cell body show that certain features are consistent throughout the group whereas others differ. Ultimately it is hoped that test architecture, features of the cell body and mode of reproduction (if observed) at the fine structural level can be used in conjunction with molecular data to enhance the phylogenetic resolution of Clade E.