Korpuskulids

Korpuskulids are a provisional grouping used in some protozoological and paleobiogeographic literature to describe a set of small, often microscopic eukaryotes encountered in aquatic sediments and waters. The term is not consistently applied and does not correspond to a single, formal taxon in modern classifications; as a result, korpuskulids are considered an informal, paraphyletic assemblage or a catchall for several unrelated lineages described in the past.

Organisms described as korpuskulids show substantial morphological diversity; some are flexible, amoeboid forms; others are more rigid or test-bearing; cell size ranges from a few micrometers to tens of micrometers.

They occupy freshwater, brackish and marine environments; often associated with sediments, detrital films, or phytoplankton; they may feed on bacteria or small algae.

Most korpuskulids are presumed to reproduce asexually by fission; cyst or resting stages have been reported in some examples.

The concept emerged in the late 19th to mid-20th century; later analyses using molecular data have not produced a stable monophyletic group, and some authors have reclassified several korpuskulid genera into other protist lineages.

Further study, particularly with modern molecular methods and careful morphometrics, is needed to clarify their diversity and evolutionary relationships.