THE HEMOFLAGELLATES 



41 



Meyer and Queiroga (1960) called it an 

 apparently lamellar mass located in a 

 vacuole-Iike space; Hans Ris (unpublished) 

 said that the lamellae represent sections 

 of a continuous spiral; Clark and Wallace 

 (1960) considered the kinetoplast to be a 

 mitochondrion containing antero-posteriorly 

 oriented anastomosing fibers. Under the 

 ordinary light microscope, the kinetoplast 

 and blepharoplast may appear to be fused. 

 Mitochondria and volutin granules have also 

 been seen in electron micrographs. 



Members of this family were originally 

 parasites of the intestinal tract of insects, 

 and many are still found only in insects. 

 Others are heteroxenous, spending part of 

 their life cycle in a vertebrate and part in 

 an invertebrate host. 



In the course of their life cycles, mem- 

 bers of one genus may pass thru forms 

 morphologically similar to those of other 

 genera. These stages are named for the 

 genera which they resemble. In the tryp- 

 anosome form, which is perhaps the most 

 advanced, the kinetoplast and basal granule 

 are near the posterior end and the undulat- 

 ing membrane runs the length of the body. 

 In the crithidial form, the kinetoplast and 

 basal granule are just anterior to the nu- 

 cleus and the undulating membrane runs 

 forward from there. In the leptomonad 

 form, the kinetoplast and basal granule are 

 still further forward in the body and there 

 is no undulating membrane. In the leish- 

 manial form, the body is rounded and the 

 flagellum has degenerated into a tiny fibril 

 which remains inside the body (Fig. 1). 

 Further information on life cycles and 

 morphology is given by Noble (1955). 



There are several genera in the fam- 

 ily Trypanosomatidae. Members of the 

 genus Trypanosoma are heteroxenous and 

 pass thru leishmanial, leptomonad, cri- 

 thidial and trypanosome stages in their 

 life cycle. In some species, only trypan- 

 osome forms are found in the vertebrate 

 host, while in other, more primitive ones, 

 both leishmanial and trypanosome forms 

 are present. 



Members of the genus Blastocrithidia 

 are monoxenous in arthropods and other 



B 



D 



Fig. 1. Forms of the Trypanosomatidae. 

 A. Leishmanial form. B. Lep- 

 tomonad form. C. Crithidial 

 form. D. Trypanosome form. 

 (Original) 



invertebrates. They pass thru crithidial, 

 leptomonad and leishmanial stages in 

 their life cycle. This generic name was 

 introduced by Laird (1959) for the crithi- 

 dial species commonly and erroneously 

 assigned to the genus Crithidia. As both 

 Laird (1959), Wallace (1943) and Clark 

 (1959) have shown, the type species of 

 Crithidia. from mosquitoes, C. fascicu- 

 lata, is a short, truncate form with a 

 stiff flagellum emerging from a funnelled 

 anterior depression, and never has an 

 undulating membrane. However, the term 

 crithidial is so deeply Embedded in our 

 terminology as referring to forms with an 

 undulating membrane that it is best to re- 

 tain it. 



Members of the genus Crithidia are 

 monoxenous in arthropods. Despite their 

 name, they have only a leptomonad stage. 



Members of the genus Leptonionas 

 are monoxenous in invertebrates. They 

 pass thru leptomonad and leishmanial 

 stages in their life cycle. 



Members of the genus Leishmania 

 are heteroxenous, passing thru the leish- 

 manial stage in their vertebrate host and 

 the leptomonad stage in their invertebrate 

 host or in culture. 



Members of the genus Herpetomonas 

 are monoxenous in invertebrates. They 

 pass thru trypanosome, crithidial, lepto- 

 monad and leishmanial stages in their life 

 cycle. The trypanosome form in this 

 genus differs from that of Trypanosoma 



