| Cutosea | |
|---|---|
Scientific classification | |
| Domain: | Eukaryota |
| Phylum: | Amoebozoa |
| Clade: | Evosea |
| Superclass: | Cutosa Cavalier-Smith, 2016[1] |
| Class: | Cutosea Cavalier-Smith, 2016[1] |
| Order: | Squamocutida Cavalier-Smith, 2016[1] |
| Families[1] | |
| Diversity | |
| 4 species | |
Cutosea (from Latin cutis 'skin') is a small group ofmarineamoeboidprotists proposed in 2016. It is a monotypic class ofAmoebozoa containing the orderSquamocutida (from Latin squama 'scale' and cutis 'skin'). Cutosean organisms are characterized by a cell coat of microscales separated from thecell membrane. Fourgenera,Armaparvus,Idionectes,Sapocribrum andSquamamoeba, belong to this group, distributed in threefamilies.
Thecells of cutoseanamoebae are surrounded by a continuous thin, somewhat flexible envelope, unique in structure because it is not attached to thecytoplasmic membrane. Below this envelope, they present oval microscales surrounded by a dense matrix. The small scales are not visible under alight microscope.[2] The envelope is penetrated by one or many small pores, which allow subpseudopodia to occasionally protrude from the cell membrane,[3] for a very slow locomotion. Locomoting cells are flattened, oval or round in shape. All of their cells lackcilia orcentrosomes,[1] except for the uniciliateswarm cells of the amoeboflagellateIdionectes.[4]
Cutosea is aclade discovered through a 2016phylogenetic study byThomas Cavalier-Smith and his coauthors, published in the journalMolecular Phylogenetics and Evolution. It is described as aclass-levelrank,monotypic as it contains only one orderSquamamoebida. Additionally, it is grouped under the monotypic superclassCutosa. In traditional rank-based classifications, it is grouped within theparaphyleticLobosa, a subphylum of Amoebozoa that also containsTubulinea andDiscosea. Cutosean amoebae present a structurally unique cellular envelope, theirdistinguishing feature. Their names derive from theLatincutis, meaning 'skin', andsquama, meaning 'scale', referencing this envelope.[1]
The Cutosea clade is supported by posteriormolecular andmorphological studies, and has been accepted as of 2019 by the International Society of Protistologists, which revises the moderncladistic classification ofeukaryotes.[3] The firstgenera to be grouped within Cutosea wereSapocribrum andSquamamoeba, discovered in 2015 and 2013 respectively, and placed in separate families Sapocribridae and Squamamoebidae. A third genus was discovered later in 2018,Armaparvus, which was added to Squamamoebidae.[2] The fourth genus,Idionectes was discovered by Sebastian Hess and Alastair G. B. Simpson in 2019.[5][6]
Cutosea contains a total of fourspecies, distributed in four monotypic genera:
Cutosea is afully supportedclade withinAmoebozoa. It is thesister group toConosa, which contains all the non-lobose amoebozoans:Variosea,Archamoebea andEumycetozoa. Together, Cutosea and Conosa are the two members of the larger cladeEvosea.[9] The followingcladogram is based on a 2022phylogenetic analysis:[10]
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