MOLECULAR PHYLOGENY OF CARTERINA SPICULOTESTA AND RELATED SPECIES FROM NEW CALEDONIA

Abstract

Carterina spiculotesta is a common tropical benthic foraminifer characterized by fusiform or rod-like calcareous spicules covering the surface of the test. Because of this peculiar wall feature, the genus Carterina was separated from other foraminifera and placed in its own suborder (Caterinina) or order (Carterinida). However, there is no agreement about the origin of Carterina spicules, which are considered either as being secreted by the foraminiferal cell or as agglutinated foreign particles; if the latter case, the genus was placed in the order Trochamminida. Here, we attempted to resolve this controversy by analysis of genetic data from various carterinids collected in New Caledonia. We obtained seven complete and 47 partial small subunit (SSU) rDNA sequences. Our results show that all specimens of spicule-bearing Carterina cluster together in a strongly supported clade. Sister to this clade are undetermined lineages of trochamminid morphospecies. Together with its sister groups, the Carterina clade forms an independent lineage at the base of Globothalamea within the paraphyletic radiation of textulariids and robertinids. Its exact phylogenetic position was difficult to establish because the used SSU rRNA genes lack resolution. As long as experimental data do not contradict the hypothesis of a secreted origin for Carterina spicules, we propose to retain the ordinal status of the Carterina clade, and consider it as one of the orders of the class Globothalamea. In view of our study, the diversity of this order may be much higher than traditionally accepted, including several genera and species, many of them new to science.