abstract: 'Multicellularity evolved multiple times in the history of life, with most
  reviewers agreeing that it appeared at least 20 times in eukaryotes. However, a
  specific list of multicellular eukaryotes with clear criteria for inclusion has
  not yet been published. Herein, an updated critical review of eukaryotic multicellularity
  is presented, based on current understanding of eukaryotic phylogeny and new discoveries
  in microbiology, phycology and mycology. As a result, 45 independent multicellular
  lineages are identified that fall into six distinct types. Functional criteria,
  as distinct from a purely topological definition of a cell, are introduced to bring
  uniformity and clarity to the existing definitions of terms such as colony, multicellularity,
  thallus or plasmodium. The category of clonal multicellularity is expanded to include:
  (i) septated multinucleated thalli found in Pseudofungi and early-branching Fungi
  such as Chytridiomycota and Blastocladiomycota; and (ii) multicellular reproductive
  structures formed by plasmotomy in intracellular parasites such as Phytomyxea. Furthermore,
  (iii) endogeneous budding, as found in Paramyxida, is described as a form of multicellularity.
  The best-known case of clonal multicellularity, i.e. (iv) non-separation of cells
  after cell division, as known from Metazoa and Ochrophyta, is also discussed. The
  category of aggregative multicellularity is expanded to include not only (v) pseudoplasmodial
  forms, such a sorocarp-forming Acrasida, but also (vi) meroplasmodial organisms,
  such as members of Variosea or Filoreta. A common set of topological, geometric,
  genetic and life-cycle criteria are presented that form a coherent, philosophically
  sound framework for discussing multicellularity. A possibility of a seventh type
  of multicellularity is discussed, that of multi-species superorganisms formed by
  protists with obligatory bacterial symbionts, such as some members of Oxymonada
  or Parabasalia. Its inclusion is dependent on the philosophical stance taken towards
  the concepts of individuality and organism in biology. Taxa that merit special attention
  are identified, such as colonial Centrohelea, and a new speculative form of multicellularity,
  possibly present in some reticulopodial amoebae, is briefly described. Because of
  insufficient phylogenetic and morphological data, not all lineages could be unequivocally
  identified, and the true total number of all multicellular eukaryotic lineages is
  therefore higher, likely close to a hundred.'
authors:
- Lamża, Łukasz
doi: 10.1111/brv.13001
issn: 1469-185X,0006-3231
issue: '6'
journal: Biol. Rev. Camb. Philos. Soc.
language: en
lastmod: '2023-12-01'
pages: 2188-2209
path: /library/lamza-2023.html
pmid: '37475165'
published: '2023-12-01'
publisher: Wiley
reference: Lamża 2023
title: 'Diversity of ''simple'' multicellular eukaryotes: 45 independent cases and
  six types of multicellularity'
type: article
volume: '98'
year: 2023