protoctist


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Related to protoctist: Protoctista, fungi

protoctist

(prə-tōk′tĭst)
n.
Any of various eukaryotic organisms belonging to the kingdom Protoctista in some classification systems. Protoctists include unicellular and multicellular organisms that are not fungi, plants, or animals. They are usually now referred to as protists.
References in periodicals archive ?
The axoneme, beneath the plasma membrane as usual in protoctist (including algae) and animal cells (including sperm), is emergent.
Protoctist mitotic (and other cell) motility patterns gave rise to the less variant mitotic patterns of liberated nuclei typical of the earliest animals, plants, fungi, and their later descendants.
Another phylum of protoctists living in conditions similar to the euglenophytes is the small group of raphidophytes ***, represented mainly by the genus Chattonella, which probably includes some species first described by the generic names of Olisthodis-cus and Hornellia.
This difficulty is extremely obvious in highly integrated symbiotic systems such as corals or some non-photosynthetic planktonic protoctists that show negligible net production to external observation, given that they recycle their chemical elements internally, using energy provided by light.
Zooplankton organisms that ingest these protoctists manage to increase the yield of the planktonic trophic chains by more than 50%.
Finally, we should mention an aspect of this accelerated dynamic that is relevant to the "greenhouse effect:" The capacity of planktonic coccolithophorids (and foraminifera with symbiotic algae, other protoctists, and some animals) to fix the excess of atmospheric carbon dioxide resulting from the combustion of hydrocarbons, and to speed up its downwards transport in the sea, or at least down to the level of the lisocline.
They graze on plant material which they digest with the assistance of a group of recently discovered protoctists living in their digestive system.
When salinity levels rise above 120 g salt per liter, the only animals that appear are the larvae of some dipterans (salt flies of the genus Ephydra), microturbellarians, nematodes, and mobile protoctists, such as the ciliate Fabrea salina.
A single litre of Alpine soil contains between 500 and 2,500 soil insects, from 500-3,000 acarid mites, up to 1,800 rotifers, 3,000 tardigrades, 18,000 nematodes and between 500,000 and 1,200,000 heterotrophic protoctists.
Further north, woody plants start to become scarce, and this loss of biodiversity is not compensated for by the enormous variety of bryophytes or the rich groupings of invertebrates and protoctists that live in the mosses carpeting the soil.
The organisms responsible for decomposing dead organic materials are larger organisms, such as wood fungi, soil mites (oribatids), and even thecamoebas and other soil protoctists.
Thecamoebas are now considered to be protoctists and not animals, although traditionally included in the invertebrates as protozoans.