''Acanthamoeba pyriformis'' is a

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

of the genus ''

Acanthamoeba ''Acanthamoeba'' is a genus of amoeboid, amoebae that are commonly recovered from soil, fresh water, and other habitat (ecology), habitats. The genus ''Acanthamoeba'' has two stages in its life cycle, the metabolically active trophozoite stage a ...

'' with a unique fruiting system with a sporocarp stage and pyriform spores. It is primarily found in

leaf A leaf (: leaves) is a principal appendage of the plant stem, stem of a vascular plant, usually borne laterally above ground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", while the leav ...

litter in multiple different climates.

Taxonomy

''Acanthamoeba pyriformis'' is classified in the

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

''. ''A. pyriformis'' was originally placed in genus ''

Protostelium ''Protostelium'' is a genus of protosteloid amoebozoans, i.e., amoebae capable of forming simple fruiting bodies composed of a stalk and a ball of spores. It contains numerous species, including '' P. aurantium'', which was initially classified i ...

'' when it was described by Olive and Stoianovitch in 1969 based on

morphology Morphology, from the Greek and meaning "study of shape", may refer to: Disciplines *Morphology (archaeology), study of the shapes or forms of artifacts *Morphology (astronomy), study of the shape of astronomical objects such as nebulae, galaxies, ...

. The species showed similarities such as fruiting body development and

and more to other ''

Protostelia ''Protostelium'' is a genus of protosteloid amoebozoans, i.e., amoebae capable of forming simple fruiting bodies composed of a stalk and a ball of spores. It contains numerous species, including '' P. aurantium'', which was initially classified i ...

'' so the researchers classified it as such, naming the species '' pyriformis'' due to its pyriform, pear-shaped,

spores In biology, a spore is a unit of sexual (in fungi) or asexual reproduction that may be adapted for dispersal and for survival, often for extended periods of time, in unfavourable conditions. Spores form part of the life cycles of many plant ...

. Using a combination of

, behavior, and

DNA sequencing DNA sequencing is the process of determining the nucleic acid sequence – the order of nucleotides in DNA. It includes any method or technology that is used to determine the order of the four bases: adenine, thymine, cytosine, and guanine. The ...

, it was reclassified into ''Acanthamoeba''.

Ecology

''Acanthamoeba'' species are generally described as opportunistic, meaning that it can survive in many different environments such as sea water, natural water, tap water, soil, and even humans. However, ''A. pyriformis'' is found primarily in

leaf litter Plant litter (also leaf litter, tree litter, soil litter, litterfall, or duff) is dead plant material (such as leaves, bark, needles, twigs, and cladodes) that has fallen to the ground. This detritus or dead organic material and its constituen ...

and can also be found on other types of decaying organic matter. In one study, this

organism An organism is any life, living thing that functions as an individual. Such a definition raises more problems than it solves, not least because the concept of an individual is also difficult. Many criteria, few of them widely accepted, have be ...

was found in

Costa Rica Costa Rica, officially the Republic of Costa Rica, is a country in Central America. It borders Nicaragua to the north, the Caribbean Sea to the northeast, Panama to the southeast, and the Pacific Ocean to the southwest, as well as Maritime bo ...

, but it is found in other parts of the world as well.

Morphology and Behavior

The organism ''Acanthamoeba pyriformis'' was originally deemed ''

'' due to its ability to build sporocarps. However, with new developments in

and comparison,

scientists A scientist is a person who researches to advance knowledge in an area of the natural sciences. In classical antiquity, there was no real ancient analog of a modern scientist. Instead, philosophers engaged in the philosophical study of nature ...

began to question this organism's original classification. It was then reclassified into the ''Acanthamoeba'' genus, which made it the first species of ''Acanthamoeba'' to include facultative sporocarpic fruiting in its life cycle. During the locomotion stage of their life, the

amoebae An amoeba (; less commonly spelled ameba or amœba; : amoebas (less commonly, amebas) or amoebae (amebae) ), often called an amoeboid, is a type of cell or unicellular organism with the ability to alter its shape, primarily by extending and r ...

are flat and can vary in shape. They are typically longer than their

width Length is a measure of distance. In the International System of Quantities, length is a quantity with dimension distance. In most systems of measurement a base unit for length is chosen, from which all other units are derived. In the Intern ...

, with an average cell length of 26.9

micrometers The micrometre (Commonwealth English as used by the International Bureau of Weights and Measures; SI symbol: μm) or micrometer (American English), also commonly known by the non-SI term micron, is a unit of length in the International System ...

. The

amoeba An amoeba (; less commonly spelled ameba or amœba; : amoebas (less commonly, amebas) or amoebae (amebae) ), often called an amoeboid, is a type of Cell (biology), cell or unicellular organism with the ability to alter its shape, primarily by ...

is led by a lobose, hyaloplasmic pseudopodium that usually contains acanthopodia, a specialized form of

pseudopodia A pseudopod or pseudopodium (: pseudopods or pseudopodia) is a temporary arm-like projection of a eukaryotic cell membrane that is emerged in the direction of movement. Filled with cytoplasm, pseudopodia primarily consist of actin filaments and ...

. The cell's granular cytoplasm contains a single, spherical or sub-spherical nucleus. When forming cysts, the

cysts A cyst is a closed Wikt:sac, sac, having a distinct Cell envelope, envelope and cell division, division compared with the nearby Biological tissue, tissue. Hence, it is a cluster of Cell (biology), cells that have grouped together to form a sac ...

are isodiametric with stellate knobs, having an average diameter of 13.1

. Sporocarps develop as the amoeba becomes refractile. A stalk is formed and deposited in the lower portion of the sporogen. At maturity, the sporogen lays down a

spore In biology, a spore is a unit of sexual reproduction, sexual (in fungi) or asexual reproduction that may be adapted for biological dispersal, dispersal and for survival, often for extended periods of time, in unfavourable conditions. Spores fo ...

wall and becomes an obpyriform spore, following which air can shed and disperse the spore. The

''Acanthamoeba'' typically has a life cycle that has a

trophozoite A trophozoite (G. ''trope'', nourishment + ''zoon'', animal) is the activated, feeding stage in the life cycle of certain protozoa such as malaria-causing ''Plasmodium falciparum'' and those of the ''Giardia'' group. The complementary form of the t ...

stage, the feeding stage where the

is most active, and a cyst stage, a dormant stage that allows the organism to survive unfavorable conditions. ''A. pyriformis'' is unique because it also includes the sporocarp stage, a structure that contains

. Being a facultative stage, it doesn't occur in all

individuals An individual is one that exists as a distinct entity. Individuality (or self-hood) is the state or quality of living as an individual; particularly (in the case of humans) as a person unique from other people and possessing one's own needs or g ...

References

Discosea Protists described in 1969 {{improve categories, date=May 2025