(Brady, 1877)
Trochospiral, with 3.5-4 chambers in last whorl (adults). Aperture bordered by small rim, may be slightly extraumbilical. Height of aperture varies from wide open in warm, saline environments, to slit-like in salinities below 35. Typical for this species is the honeycomb (hexagonal) surface structure, which is lacking in other spinose species (but does occur in a non-spinose genus: Globoquadrina hexagona, from Indo-Pacific). Last chamber sacciform, elongated.
Ref.: Hecht (1974), Bé (1980), Bé et al. (1981), Caron et al. (1981, 1987a), Duplessy et al. (1981), Brummer et al. (1987), Hemleben et al. (1987), Bijma et al. (1990a, 1990b, 1992, 1994), Spero and Lea (1993).
Remark: Following widespread usage, we retain the present name for this species, rather than Globigerinoides quadrilobatus or Globigerinoides trilobus. However, in the distributional data set, authors used the name Globigerinoides trilobus sacculifer for Globigerinoides sacculifer with a sack-like terminal chamber, and Globigerinoides trilobus trilobus for those devoid of this trait.
Distribution: Tropical to subtropical. In the eastern South Atlantic it peaks above the Walvis Ridge, and in the equatorial region. This distribution pattern may also be affected by its reproduction cycle. Maximum abundances occur 1 and 5 days after full moon, which fits the reproductive cycle of a full lunar period observed by Bijma et al. (1990a). Nevertheless, comparison of the abundance of Globigerinoides sacculifer with water temperature, salinity, and dissolved oxygen indicates enhanced numbers with increasing oxygen content and lower salinity (Oberhänsli et al., 1992). This suggests that the distribution pattern is not the result of reproductive behavior alone. In the Walvis Ridge area, oxygen-rich subtropical surface water eddies are mixed with lower salinity water of the Benguela Current. The abundance maximum at the equator corresponds roughly with the oxygen-rich South Atlantic Central Water and the less saline surface water coming from the coast of Equatorial West Africa (Levitus and Boyer, 1994). This suggests that Globigerinoides sacculifer is an indicator of oxygen-rich, low-salinity waters, yet in other regions, like the Caribbean, Globigerinoides sacculifer prefers higher salinities, whereas Globigerinoides ruber occurs in low-salinity water masses.
These contrasting observations suggest that, within certain limits, salinity seems to play a minor role (Bijma et al., 1990b). On the other hand, food availability may explain these contrasting distributional patterns. Field and laboratory observations indicate that Globigerinoides sacculifer occupies more oligotrophic water masses and feeds mostly on copepods, whereas Globigerinoides ruber prefers eutrophic environments. The depth distribution of Globigerinoides sacculifer is typical of spinose, symbiont-bearing foraminiferal species: highest concentrations in the upper 50 m, decreasing sharply further down, with “living” specimens best showing this abrupt decline with depth; only “dead” specimens are recorded in deeper net hauls. Downward flux of “dead” shells blurs the downward decreasing trend somewhat (Kemle-von Mücke, 1994).