Protist Gallery

This is a ciliate protist in the genus Euplotes (20-30 micrometers). These protists are common on surfaces in marine systems. They belong to a larger group of ciliates known as hypotrichs; the name being derived from the bundles of cilia (cirri) they use for walking/crawling appendages. On the left is a typical ventral view, with the caudal cirri extending out from the bottom, and the oral ciliature on the (organism's) left side. The right micrograph shows this same organism in its typical habit, perched on a macroalga and feeding in the surface microlayer. For more on the feeding behavior of this ciliate see Lawrence and Snyder (1998).

 

 

This is a small amoeba in the genus Vanella (10-15 micrometers). It expresses a single pseudopod (it's monopodial) unlike its more famous relative Amoeba proteus. The micrograph on the left shows the cell in a field of bacteria (the small objects) on which it preys. The left micrograph shows what happens at the interface between water and jet fuel (which doesn't seem to bother the amoeba). Bubbles of water trapped under the oil contain bacteria that have grown in number by using the oil for food. A dense line of bacteria is found at the interface where both oil and water are available to support bacterial growth. The amoeba finds a concentrated food source (bacteria) at this ecotone.

 

 

This is an unidentified ciliate (at least a new species) recovered from the surface of massive corals at a depth of 80 feet in the outer Bahaman Islands. It contains autotrophic symbionts that may be the same as the species in the coral on which it was found (Zooxanthellae; Dionflagellata). On the left is a silver protein stain in which the large macronucleus of the ciliate and the smaller nuclei of the symbionts are visible. On the right is a micrograph of the autofluorescence of the chlorophyll in the symbionts when exposed to UV light.

  

 

Many protists form resistant cysts as shown in this micrograph. The stimulus for encystment is usually a lack of food, desiccation, or other adverse situation the organism wishes to avoid, betting on a change for the better in the future.

Some forms are relatively delicate, and when we try to preserve them with chemical fixatives, they disintegrate. This micrograph shows the anterior oral ciliature of a planktonic oligotrich Strombidinopsis acuminatum, all that remained of the cell after fixation (see Dale & Lynn, 1998 J. Euk. Microb. 45:166-170).

 

 

These micrographs are silver stains of a cultured planktonic oligotrich ciliate, Strombidium (probably sulcatum). On the left is a starved cell showing the anterior oral ciliature used for both locomotion and feeding. On the right is a comparison of starved and well-fed cells to illustrate the plasticity of morphology in response to food. . For more on the growth responses of this ciliate see Ohman & Snyder (1991).

 

 

These protists are a pair of ciliates without cilia: loricate suctorians attached to a copepod from a tundra lake in Alaska.

This protist is the scutico ciliate Pseudocohnilembus marinus (about 20 micrometers long), a marine and estuarine bacterivorous protist that forms resting cysts when food is depleted. Chemoattraction responses of this ciliate to bacterial surface material can be found in Snyder (1991)

 

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