MONOCELLULAR ANIMALS-THE PROTOZOA 



123 



Noctiluca Oyrodinium 



Goniodomo Gymnodiniurn 



Fig. 7-15. Various types of marine flagellates. 



ing with free-living flagellates. The dino- 

 flagellates, for example, live in the ocean 

 for the most part and constitute a large por- 

 tion of the diet for small Crustacea and 

 other animals. Some members, such as Noc- 

 tiluca ( Fig. 7-15 ) , possess luminescent prop- 

 erties which cause them to glisten in the 

 dark when the surface of the water is dis- 

 turbed. This is a particularly attractive 

 sight in the wake of a boat. Another inter- 

 esting dinoflagellate, Gijmnodinium brevis 

 (Fig. 7-15), has appeared several times dur- 

 ing the past hundred years along the Flor- 

 ida coast in extremely large numbers (50,- 

 000,000 per liter — a normal count is about 

 100,000 for all kinds of protozoans). Fur- 

 thermore, this protozoan apparently se- 

 cretes a by-product which is lethal to all 

 other kinds of animal life in the vicinity. In 

 1947 half a billion fish were destroyed along 

 the Florida coast, presumably by this toxin. 



Fresh water, particularly that containing 

 a considerable amount of organic decompo- 

 sition, supports a large variety of flagellates 

 (Fig. 7-16). Many of them play a very im- 

 portant function in providing food for 

 aquatic animals, especially during their 

 early life when their mouths are so small 

 that no other food but a protozoan could be 

 ingested. Without these tiny animals there 

 would be no fish in many of our lakes and 

 streams. Some, like Haematococcus pliivia- 

 Jis ( Fig. 7-16), are bright green in color and 

 can reach unbelievable numbers in small 

 pools. Like euglena, they produce haemato- 

 chrome at certain times of the year, impart- 

 ino; a reddish color to the water. In some 

 Alpine passes they have been responsible 

 for the so-called "bloody snow," a familiar 

 sight to mountain climbers. 



Colorless flagellates. Some colorless 

 forms, such as Peranetna and Chilo^nonas 



