foraminifera

Foraminifera, commonly referred to as forams, are a large and diverse group of single-celled protists within the Rhizaria. They are characterized by their reticulating pseudopods and often by tests, or shells, which enclose the cell. The tests are typically made of calcium carbonate, though some species use agglutinated particles or organic material. The walls exhibit a variety of shapes and chamber arrangements, and many species extend feeding networks of reticulopodia through apertures in the shell.

Most forams are marine, occupying both planktonic and benthic habitats. They range from shallow coastal waters to the deep ocean, and a smaller number live in freshwater or brackish environments. They feed on bacteria, detritus, and small algae, using their pseudopods to capture prey. Some larger foram species host symbiotic algae within their cytoplasm, providing additional photosynthetic nutrition.

Reproduction occurs through both sexual and asexual means, and many species show complex life cycles that can include alternation of generations. The tests grow as the organism prospers, and new generations often produce new tests with different shapes and chamber patterns.

Foraminifera have an extensive fossil record dating back to the early Paleozoic, with abundant calcareous shells preserved in marine sediments. Their tests accumulate to form calcareous ooze and contribute to limestone deposits. Foraminifera are vital to biostratigraphy and paleoenvironmental reconstructions, as their species distributions and stable isotope compositions record past ocean temperatures, chemistry, and productivity. They remain important in marine ecology and petroleum geology for interpreting past and present ocean conditions.