Microworld

world of amoeboid organisms

Menu

Heliozoa Haeckel 1866, stat. n. Margulis 1974, emend. Cavalier-Smith 2012

Diagnosis: Phagotrophic and non-photosynthetic protists with one large spherical or near spherical centrosome at the centre of the cell and numerous radiating axopodia. Axopodia always with extrusomes that are either kinetocysts or tiny dense ellipsoids.

Description: Centrohelids, also called true Heliozoa, are ubiquitous, unicellular amoeboid organisms with slender uniformly radiating axopodia by which they feed. These axopodia are straight, not branching, and possess numerous granules, called kinetocysts, which are used for trapping prey. Each axopodium has a central axoneme with numerous microtubules arrayed in hexagons or triangles. These arrangements can be very different, suggesting that centrohelids are a polyphyletic group. All centrohelids have flat mitochondrial cristae. Most centrohelids are surrounded by a coat or layer of silica scales, which are well characterized by electron microscopy. The morphology and structure of these scales are used to identify most taxa.

Different type of scales

Morphology and ultra-structure of a centrohelid: AX = Axoneme; CV = Contractile Vacuole;  ER = Endoplasmic Reticulum; FV = Food Vacuole; G = Golgi Apparatus; KI = Kinetocyst; M = Mitochondria; MC = MTOC: Microtubule-organizing center; N = Nucleus; PS = Plate-scale; SS = Spine-scale.
Acanthocystis sp., SEM; the colors are artificial – courtesy of © eye of science (www.eyeofscience.com)
Recent posts

Euglypha bryophila

Euglypha bryophila, after Brown, 1911 (L), from Ecuador (R) Euglypha bryophila  Brown, 1911 Diagnosis: (Original description) The test is very regular in form and subject

Read More »

Vernalophrys

(A) A Scenedesmus cell (arrow) is engulfed by a trophozoite. (B) Several Scenedesmus cells adhere to the surface of a plasmodium that has numerous vacuoles

Read More »

Actinosphaeridium spec.

Actinosphaeridium spec. Diagnosis: Cell surrounded by a membranous shell, with an outer mucous layer. Filopodia with granules, sometimes branching. Cell stalked. Ecology: I found this

Read More »

Euglyphidion

Euglyphidion enigmaticum – after Bonnet, 1960 Genus Euglyphidion Bonnet, 196 Diagnosis: Shell hyaline, ovoid, pseudostome circular or slightly elliptical. Shell loosely covered with two types of

Read More »

Leptomyxa spec.

Leptomyxa sp., slowly retracting in response to the light of the microscope Leptomyxa sp. Diagnose: This is a very large amoeba which I found in

Read More »

Zivkovicia spec.

Zivkovicia spec., 200 µm long; the right image is viewed through the aperture Zivkovicia spec.  Diagnosis: Shell pyriform, circular in oral view, with a clear

Read More »