Milionella subrotunda (Montague 1803), a miliolid foraminifer building large agglutinated tubes for a temporary epibenthic livestyle.

Live observations, cytological characteristics and biometrical measurements on Miliolinella subrotunda (Montagu, 1803) sampled from the northern and southern Atlantic Ocean are presented.M. subrotunda facultatively constructs a long, detritic tube lifting the test several millimeters above the sediment surface. A thickened conical base anchors the construction on the sediment surface and a long, flexible tube protrudes into the velocity profile of the bottom currents. The miliolid test is placed on top, surrounded by the uppermost part of the tube. This construction allows the organisms to feed in the particle stream above the sediment surface. In comparison to species living in and on the surface sediments,M. subrotunda apparently shows higher nutritional values in food ingested and larger amounts of reserve substances. Characteristics of the shape and structure that reduce drag on the tubes include a broadened conical base, a flexible tube, and a rounded top. From biometrical measurements it is concluded, that the tubes are constructed over a short period of their ontogeny

Genetic and morphometric evidence for parallel evolution of the Globigerinella calida morphotype

Molecular genetic investigations of the highly abundant extant planktonic foraminifera plexus Globigerinella siphonifera/Globigerinella calida have recently shown this group to be the genetically most diverse one within planktonic foraminifera, separating it into 12 distinct genetic types belonging to three main genetic lineages. Independently, several morphological or physiological variants have been described within the group, but the correlation between the high genetic diversity and the phenotypic variability remains unclear. In this study, we combine genetic data with morphometric analyses of shell shape and porosity of genotyped individuals of the different genetic lineages. Our morphometric measurements suggest a differentiation of three morphotypes within the plexus, two of which possess the elongated chambers described as a typical trait of G. calida. These two morphotypes with elongated chambers are associated with two distinct genetic lineages. The G. calida morphology therefore appears to have evolved twice in parallel. Unexpectedly, we show that the two morphotypes with elongated chambers can be separated from each other by characters seen in the lateral view of their shells. This implies that the taxonomy of the extant members of the genus Globigerinella should be revised. A comparison with the original descriptions and type specimens of members of the genus shows that two genetic types of one major lineage correspond to G. calida. The second group with elongated chambers is associated with a recently diverged genetic type and we propose to reinstate the name Globigerinella radians for this distinct form. The remaining nine of the 12 genetic types correspond to the G. siphonifera morphology, and in the absence of evidence for morphological differentiation, they form a paraphyletic morpho-taxon. Our results highlight the prevalence of parallelism in the evolution of shell morphology in planktonic foraminifera even at the lowest level of relatedness represented by genetic types