Diaphoretickes

Lore & Background

Before molecular analyses recovered this clade, evolutionary biologist Thomas Cavalier-Smith had already hypothesized an evolutionary proximity between plants and the remaining groups (collectively known as 'chromalveolates' in his classification system). He coined the term photokaryotes for these organisms, as they include almost all of the photosynthetic eukaryotes. He later called them corticates due to the presence of cortical alveoli in many of their members. Although Diaphoretickes contains organisms of very different morphologies, they have a few common traits. Ancestrally they are similar to excavates, with two flagella and a ventral feeding groove. In addition, the presence of cortical alveoli and flagellar hairs are interpreted as ancestral traits unique to the group. Some traits appeared convergently in many groups, such as the acquisition of chloroplasts through primary and secondary endosymbioses and the presence of axopodia and a heliozoan-type cell. In particular, chloroplasts with chlorophyll c and heliozoan cells are exclusive to Diaphoretickes. Within Diaphoretickes, Cryptista and the heliozoan Microheliella maris form the clade Pancryptista, which is the closest relative to Archaeplastida, together forming the CAM clade. Haptista and SAR are closer to each other and to a clade of flagellates known as Telonemia. In addition, three small groups of protists, Provora, Hemimastigophora and Meteora sporadica, form a clade that may belong to Diaphoretickes.

Reader's Guide

Diaphoretickes includes eukaryotes of very different morphologies, cellular structures, life cycles and habitats. They range from photosynthetic algae to highly specialized parasites and even large, multicellular organisms like land plants. As such, they include most of the Earth's biomass, with land plants alone occupying over 81% of the total planet biomass. Its major groups are: Archaeplastida, SAR supergroup, Haptista and Cryptista. Also included is a small group of single-celled flagellates known as Telonemia, which contains 7 species. Archaeplastida includes organisms with chloroplasts derived directly from a primary endosymbiosis event with a cyanobacterium. They amount to an estimated 450,000–500,000 species. Known as plants by some authors, archaeplastids include many protists that do not belong to the multicellular land plants or embryophytes (such as mosses, conifers, ferns, flowering plants), these protists are primarily the red algae, glaucophyte algae, and green algae, from which embryophytes evolved. Archaeplastids also include two small groups of heterotrophic flagellates closely related to red algae: rhodelphids and picozoans. Embryophytes, green algae and red algae all evolved multicellular forms and complex life cycles independently, but embryophytes are distinguished by the retention of the zygote (fertilized egg cell) as an embryo, instead of its dispersal as a single cell. The SAR supergroup is named after its three constituent clades: stramenopiles, alveolates and rhizarians. The stramenopiles gather more than 100,000 species in total and comprise many heterotrophic unicellular or fungus-like organisms (e.g., oomycetes, labyrinthulids, bicosoecids, opalinids), but the described diversity is concentrated in the ochrophytes, the photosynthetic clade (e.g., diatoms, kelp, golden algae). They are distinguished by the presence of straw-like mastigonemes (flagellar hairs) in one of their two flagella, when present. The alveolates are unicellular protists primarily composed of three large, well-studied groups: ciliates (more than 8,000 species, mostly free-living heterotrophs), dinoflagellates (~4,500 species, many photosynthetic) and apicomplexans (more than 6,000 parasitic species), all of which are unicellular. In particular, dinoflagellates, apicomplexans and various smaller groups (e.g., chromerids) evolved from a photosynthetic ancestor

Did You Know?

• The name Diaphoretickes derives from Greek meaning diverse, dissimilar, referring to the wide morphological and cellular diversity among members of this clade.
• In 2012, a publication by the International Society of Protistologists (ISOP) established a taxonomic name for this clade, Diaphoretickes.
• In 2015, Cavalier-Smith and co-authors rejected the name Diaphoretickes, arguing it was 'an entirely unnecessary, and less euphonious third synonym with no intuitive meaning' and suggested converting the pre-existing nam