Trochospiral, with 3 chambers in last whorl, aperture umbilical over penultimate and antepenultimate chambers. On spiral side two smaller secondary apertures visible. Two varieties (phenotypes): white and pink forms (forma alba and forma rosacea), pink form only in the Atlantic. In the Indo-Pacific the pink variety became extinct during Termination II (approximately 127 ky ago). White variety on average approximately 50 µm smaller than pink. Reddish color from pigment mostly on wall of inner whorl. Last chamber always whitish, in contrast to Globoturborotalita rubescens whose entire test is reddish. Both varieties of Globigerinoides ruber have symbionts, indicating a near-surface habitat.
Ref.: Glaçon and Sigal (1969), Vergnaud-Grazzini et al. (1973), Hecht (1974), Kennett (1976), Brummer et al. (1987), Brummer and Kroon (1988), Gastrich and Bartha (1988), Hemleben et al. (1989), Oberhänsli et al. (1992), Kemle-von Mücke (1994), Kroon and Darling (1995), Ortiz et al. (1995), Wang et al. (1995).
Distribution: The most common species in warm to temparate South Atlantic waters. The Temperature range of the white form, however, is broader and extends into temperate water masses. Thus Globigerinoides ruber pink form may be considered a summer species, whereas Globigerinoides ruber white form occurs year-round and dominates during the austral winter. In the eastern South Atlantic it is most abundant in the Angola Gyre, with significant concentrations also in the equatorial upwelling area, but low numbers elswhere. It widespread distribution in the underlying sediment suggests that the planktonic pattern is a result of reproductive habits. Abundance maxima in the Angola Basin coincide with the first quarter (2 days before the moon phase) and at the Equator and northern stations with the last quarter (0-3 days before the moon phase). This may agree well with the results od Bijma et al., 1990a, who document a semilunar reproduction periodicity for Globigerinoides ruber. However, Van Leeuwen, 1989 also found higher percentages of Globigerinoides ruber at 10°S, 10°E in the Angola Basin, and at the Equator on the sea floor, as well as lower frequencies off the south coast of Angola. It is therefore probable that despite the influence of the reproduction cycle, concentrations of Globigerinoides ruber in the water column still do reflect its preference for particular oceanic areas. In the South Atlantic Globigerinoides ruber pink form is generally more than 5 times less abundant than Globigerinoides ruber white form.