Cercozoans

Clathrulina, one of the desmothoracid protists. Traditionally classified as the heliozoa because of the star-shaped appearance of the cell, but the heliozoa have always been a rag-bag of unrelated organisms. Desmothoracids may adopt one of several forms. A ‘mature’ trophont (feeding form) is an amoeboid organism with stiffened arms. It lives in an spherical (ish) organic lorica which has large openings. The stiffened pseudopodia extend out of the openings to capture food. The central nucleus is also evident. Differential interference contrast.

Clathrulina, one of the desmothoracid protists. Traditionally classified as the heliozoa because of the star-shaped appearance of the cell, but the heliozoa have always been a rag-bag of unrelated organisms. Desmothoracids may adopt one of several forms. A ‘mature’ trophont (feeding form) is an amoeboid organism with stiffened arms. It lives in an spherical (ish) organic lorica which has large openings. The chamber is borned on a hollow stalk, and several stalked loricae may be joined end to end or in a branching arrangement. The stiffened pseudopodia extend out of the openings to capture food. Division leads to the formation of flagellated cells one or all progeny vacate the lorica, swim around and then settle as an amoeba. The amoeba secrete a stalk and mucus, and the mucus is shaped and accretes to form a lorica. The lorica strengthens and thickens with age. This image is of a young cell that is part way through the process of creating a lorica. Differential interference contrast.Phase contrast micrograph.

Clathrulina, one of the desmothoracid protists. Traditionally classified as the heliozoa because of the star-shaped appearance of the cell, but the heliozoa have always been a rag-bag of unrelated organisms. Desmothoracids may adopt one of several forms. A ‘mature’ trophont (feeding form) is an amoeboid organism with stiffened arms. It lives in an spherical (ish) organic lorica which has large openings. The chamber is borned on a hollow stalk, and several stalked loricae may be joined end to end or in a branching arrangement. The stiffened pseudopodia extend out of the openings to capture food. Division leads to the formation of flagellated cells one or all progeny vacate the lorica, swim around and then settle as an amoeba. The amoeba secrete a stalk and mucus, and the mucus is shaped and accretes to form a lorica. The lorica strengthens and thickens with age. This image shows several cells at different stages of development. Differential interference contrast.

Clathrulina (cla-through-line-a), showing head region and included amoeboid cell. Differential interference contrast.

Hedriocystis undergoing division within faceted stalked capsule. Axopodia protrude from pores in capsule. Daughter cells become flagellated, escape the lorica then secrete their own stalk and lorica. Two of the five species in the genus have a spherical non-faceted lorica. Recently, a new genus, Penardiophrys has been erected for the faceted desmothoracid species such as this one. From freshwater pond near Boise, Idaho. Phase contrast. See Mikrjukov,K. Taxonomy and Phylogeny of Heliozoa I. Acta Protozool 39:81-97, 2000.

Hedriocystis - portrait of a species with smooth non-faceted spherical lorica. Phase contrast. From a freshwater pond near Boise, Idaho.

Hedriocystis species within faceted stalked siliceous capsule. Axopodia protrude from pores in capsule. Two of the five species in the genus have a spherical non-faceted lorica. Recently a new genus, Penardiophrys has been erected for the faceted desmothoracid species such as this one. From freshwater pond near Boise, Idaho. Phase contrast. See Mikrjukov,K. Taxonomy and Phylogeny of Heliozoa I. Acta Protozool 39:81-97, 2000.

Hedriocystis, a small desmothoracid protist. The cell lives as an amoeba with stiffened arms (axopodia) within a loose lorica that has large holes or perforations. The lorica is stalked. When the cell divides, it may produce flagellated cells which leave the lorica and set up home elsewhere. From Lake Donghu, China. Phase contrast micrograph.

Hedriocystis has a cell body enclosed within an extracellular capsule which is either homogeneous or composed of regular polygonal facets; axopodia emerge from small perforations. Three species with long hollow stalk, one species without.

Dimorpha (die-morph-a), the genus contains helioflagellates in which there are two flagella and in which the axonemes terminate on a microtubule organizing centre located near the front of the cell. This is the motile form. Phase contrast.

Dimorpha (die-morph-a), the genus contains helioflagellates in which there are two flagella and in which the axonemes terminate on a microtubule organizing centre located near the front of the cell. Normally the arms do not branch and nor do they have strongly developed extrusomes, so this organism is identified only tentatively to this genus. This taxon may produce arm-less swimming cells, illustrated in another image. Phase contrast.

Tetradimorpha, a dimorphid helioflagellate. Four weakly oscillating flagella are seen emerging from the cell at the one o clock position. Axopodia with extrusomes radiate around the circumference of the cell. The axopodia may be completely withdrawn into the cell when it is disturbed. Although the size of these individuals is smaller than that described for T. pterbica (65-95 microns) the circumferential distribution of axopodia and the complete withdrawal of axopods and the shorter flagella are consistent with descriptions of T. pterbica. What appears to be the spherical dense axoplast (the termination of axopodial axonemes) is seen in the anterior of the cell between the flagellar insertions and the nucleus. From temporary rainwater pool near Boise, Idaho. Oblique illumination.

Tetradimorpha, a dimorphid helioflagellate. Four weakly oscillating flagella are seen emerging from the cell at the top of the cell. Axopodia with extrusomes radiate around the circumference of the cell. The axopodia may be completely withdrawn into the cell when it is disturbed. Although the size of these individuals is smaller than that described for T. pterbica (65-95 microns) the circumferential distribution of axopodia and the complete withdrawal of axopods and the shorter flagella are consistent with descriptions of T. pterbica. From temporary rainwater pool near Boise, Idaho. Phase contrast illumination

Tetradimorpha diagram based on light microscopy and transmission electron microscopy showing the four anterior flagella linked to the axosplast and the posterior axopods originating from microtubules arising from the axosplast, microtubules of the axopods are not regularly arranged like in Dimorpha (from G. Brugerolle and J.-P. Mignot).

Tetradimorpha marina Fenchel et al., 1995. This heliozoan-like organism is almost spherical and most cells measured between 15 and 20 microns in diameter. The spherical nucleus is situated towards one side adjacent to a depression in the cell surface, from the bottom of which either two or four flagella arise. Cells with four flagella might represent early division stages, but there was no correlation between the number of flagella and cell diameter. About twenty axopodia with extrusomes radiate from the cell. The cell are packed with spherical food vacuoles containing bacteria and the surrounding cytoplasm is filled with rod-shaped (~ 1 microns) organelles or endosymbiotic bacteria. The cells are capable of absorbing the axopodia and of transforming into a slug-like flagellated form.

Hermesinum adriaticum Zacharias, 1906. The skeleton of this species is asymmetrical and difficult to describe. The skeleton is 48-50 microns long, 20 microns wide at its widest point and 12 microns high.

Ebria (ee-bree-a) A small group of marine flagellates, although may be abundant, and large numbers have been assoicated with fish kills. They deposit complex siliceous endoskeletons within the cells. As you can see. Differential interference contrast.

Ebria (ee-bree-a) A small group of marine flagellates, although may be abundant, and large numbers have been assoicated with fish kills. They deposit complex siliceous endoskeletons within the cells and (as in this case) the skeleton may be found on its own. The ebriids have been implicated in fish kills. Phase contrast.

Ebria tripartita (Shumann, 1867) Lemmermann, 1899. Specimens of this species are almost spherical in shape and average 24 microns in diameter.