''Txikispora'' is a genus of parasitic

protists A protist ( ) or protoctist is any Eukaryote, eukaryotic organism that is not an animal, Embryophyte, land plant, or fungus. Protists do not form a Clade, natural group, or clade, but are a Paraphyly, paraphyletic grouping of all descendants o ...

made up solely of the species ''Txikispora philomaios''. It is the only genus in the family Txikisporidae, which is a member of the class

Filasterea Filasterea is a proposed basal Filozoan clade of single-celled ameboid eukaryotes that includes '' Ministeria'' and '' Capsaspora''. It is a sister clade to the Choanozoa in which the Choanoflagellatea and Animals appeared, originally proposed b ...

and is closely related to Ministeriidae. The lineage was first described in 2022 based on specimens identified from the United Kingdom. The species represents a previously undiscovered type of life that diverged extremely early from animals and fungi. It parasitizes

amphipods Amphipoda () is an order (biology), order of malacostracan crustaceans with no carapace and generally with laterally compressed bodies. Amphipods () range in size from and are mostly detritivores or scavengers. There are more than 10,700 amphip ...

in the genera '' Echinogammarus'' and '' Orchestia'' and most frequently infects their

hemolymph Hemolymph, or haemolymph, is a fluid, similar to the blood in invertebrates, that circulates in the inside of the arthropod's body, remaining in direct contact with the animal's tissues. It is composed of a fluid plasma in which hemolymph c ...

and

hemocytes A blood cell (also called a hematopoietic cell, hemocyte, or hematocyte) is a cell produced through hematopoiesis and found mainly in the blood. Major types of blood cells include red blood cells (erythrocytes), white blood cells (leukocytes), ...

Description

The species goes through several stages of life. The first is as a single spherical cell, called the monokaryotic stage. It usually has a cell wall, and is characterized by a nucleus with a small

nucleolus The nucleolus (; : nucleoli ) is the largest structure in the cell nucleus, nucleus of eukaryote, eukaryotic cell (biology), cells. It is best known as the site of ribosome biogenesis. The nucleolus also participates in the formation of signa ...

on its periphery and many small

mitochondria A mitochondrion () is an organelle found in the cells of most eukaryotes, such as animals, plants and fungi. Mitochondria have a double membrane structure and use aerobic respiration to generate adenosine triphosphate (ATP), which is us ...

with diverse lipoid structures. The next stage is

multinucleated Multinucleate cells (also known as multinucleated cells or polynuclear cells) are eukaryotic cells that have more than one nucleus, i.e., multiple nuclei share one common cytoplasm. Mitosis in multinucleate cells can occur either in a coordinate ...

, and consists of four cells joined together and is somewhat larger. It appears to have three cells, with the fourth often hidden from view. The unicellular stage is often split off from the multicellular one.

Taxonomy and etymology

The Filozoan species was described in 2022 in the ''

Journal of Eukaryotic Microbiology The ''Journal of Eukaryotic Microbiology'' is a peer-reviewed scientific journal covering all aspects of eukaryotic microbiology. The journal publishes research on protists, including lower algae and fungi. According to the ''Journal Citation Repo ...

'' by Ander Urrutia, Stephen Feist, and David Bass. The new generic and specific combination ''Txikispora philomaios'' means "May-loving spore", in reference to its presence in collections during only a few days during the month of May. ''Txikispora'' is derived from a

Basque Basque may refer to: * Basques, an ethnic group of Spain and France * Basque language, their language Places * Basque Country (greater region), the homeland of the Basque people with parts in both Spain and France * Basque Country (autonomous co ...

word: meaning "small" and a latin one meaning "spore". The specific epithet ''philomaios'' is: ' meaning "love" and meaning "May". A Rel homology region (RHR) was identified in ''Txikispora philomaios''. The characteristics of the RHR of ''Txikispora philomaios'' was most similar to ''

Tunicaraptor unikontum ''Tunicaraptor'' is a genus of marine microbial protists containing the single species ''Tunicaraptor unikontum'', discovered in 2020 from marine waters of Chile. It is a lineage of predatorial flagellates closely related to animals. It has a ...

'', suggesting a

phylogenetic In biology, phylogenetics () is the study of the evolutionary history of life using observable characteristics of organisms (or genes), which is known as phylogenetic inference. It infers the relationship among organisms based on empirical dat ...

relationship between the two species.

Ecology

''Txikispora philomaios'' parasitizes the

amphipod Amphipoda () is an order of malacostracan crustaceans with no carapace and generally with laterally compressed bodies. Amphipods () range in size from and are mostly detritivores or scavengers. There are more than 10,700 amphipod species cur ...

genera '' Echinogammarus'' and '' Orchestia,'' but is not found in the related genera ''

Gammarus ''Gammarus'' is an amphipod crustacean genus in the family Gammaridae. It contains more than 200 described species, making it one of the most species-rich genera of crustaceans. Different species have different optimal conditions, particularly ...

'' and ''Melita''. Individuals infected by the parasite displayed yellowing tegument, a less rigid

carapace A carapace is a dorsal (upper) section of the exoskeleton or shell in a number of animal groups, including arthropods, such as crustaceans and arachnids, as well as vertebrates, such as turtles and tortoises. In turtles and tortoises, the unde ...

, less visible internal organs, and increased lethargy and unresponsiveness. ''Txikispora philomaios'' specifically infects the

and individual

, with up to ten parasites found in a single hemocyte. Other organs that are infected are the hepatopancreas, testes, and ovaries.

References

Bibliography

* * {{Taxonbar, from=Q126597094, from2= Q126597083, from3= Q126597109 Filasterea Taxa described in 2022 Biota of the United Kingdom Protist genera