SIMPLE LIFE 



135 



Perhaps the most important amoeba is Entamoeba 

 histolytica, the protozoan that produces amoebic 

 dysentery in man. Other sarcodines, especially the 

 radiolarians and foraminiferans, secrete shell-like 

 structures. The foraminiferans are used by pe- 

 troleum geologists to identify oil-bearing layers of 

 rocks, and some fossil species occur in rocks more 

 than one-half billion years old. 



SPOROZOA 



Diagnosis: fixed and motionless or possessing 

 amoeboid movement; some display worm-like or less 

 marked gliding body movements; individuals 

 rounded or oval to elongate or worm-like; all are 

 parasites (mostly internal) that move as "spores" (re- 

 sistant encasements of zygotes or young) from host 

 to host (Figure 8.5). 



Figure 8.5 Sporozoan types, all microscopic. 



Structure: individuals regularly distinct with a cell 

 membrane, no cell wall, but rarely with adhesive or- 

 ganelles; nucleus complete and complex, generally 

 one per individual except during multiple fission; 

 organelles normally absent. 



Nutrition: strictly parasitic by body surface ab- 

 sorption. 



Reproduction: both asexual and haplobiontic, adult 

 haploid, life cycles; both cycles regularly involve mul- 

 tiple fission and complex stages. 



Occurrence: parasitic, most species within the cells 

 of their host; many cause disease. 



The "spore animals" all are parasites of other 

 creatures, mostly animals. Sporozoans have a com- 



plex life cycle with sexual and asexual stages. They 

 get their name from the asexual cells, or spores, they 

 produce during part of their life cycle. Like the 

 spores of most protozoans those of sporozoans serve 

 to protect the organism during an unfavorable period, 

 in the present instance that involving the movement 

 from one host to another. Among the more important 

 creatures in this class are those causing malaria; 

 mosquitoes transport these protozoans from infected 

 to other humans. 



CILIOPHORA 



Diagnosis: protozoans bearing hair-like organelles 

 (cilia) during some to all stages of the life cycle; 

 cilia typically are numerous and in rows over the 

 body; never amoeboid like Sarcodina and certain 

 other protozoans; normally with one nucleus larger 

 than the others. 



CLASS CILIATA (Ciliates) 



Diagnosis: individual's shape fixed, spherical to 

 elongate; shape usually fixed by a firm external 

 pellicle that normally is diagonally or longitudinally 

 grooved; often each groove is a site for attachment of 

 a row of cilia, but when pellicle sculpturing bounds 

 squares or other geometric forms, one or two cilia are 

 within the confines of the sculpturing; characterized 

 by cilia being present throughout the life cycle; cilia 

 are agents of movement and other functions; ciliates 

 are mostly solitary and motile but some species occur 

 as sessile, branching colonies; many are parasites 

 (Figure 8.6). 



Structure: individuals regularly distinct, often with 

 a clearly differentiated external pellicle; nuclei com- 

 plete and complex, at least one larger than the others; 

 no chlorophyll or eye spot (stigma), but ciliates con- 

 stitute the most complexly organized protozoans; 

 trichocysts present (see Flagellata) and very com- 

 plex; cilia occur singly or united into complex struc- 

 tures that help capture prey by propelling food to a 

 gullet, or that aid in swimming or crawling; some 

 cilia probably are sensory; possess a complex body- 

 coordinating structure; many have organelles pro- 

 viding movements much as do muscles; contractile 

 vacuoles with contributing canals and/or vacuoles; 

 food gathering often involves structures such as 

 mouth and gullet. 



