80 



Reproduction and Life-Cycles 



Protozoa undergo such activity at irregular intervals, the life-cycles of 

 certain species cannot be completed without syngamy. For example, the 

 mosquito phase of the life-cycle in Plasmodium must be initiated by 

 gametogenesis and syngamy. The same thing is true for the formation of 

 spores (protective cysts) in Eimeria and related genera. 



Various kinds of sexual phenomena have been described in Protozoa. 

 Syngamy, in which two gametes fuse completely to form a zygote, may 

 involve gametes which are similar in appearance (isogamy), or are of two 

 types (anisogamy). Pedogamy appears to be an unusual type of syngamy 

 in which the two gametes are not more than one or two cell-generations 

 removed from a single gametocyte. Autogamy involves the formation of 

 two gametic nuclei, and their subsequent fusion to form a synkaryon 

 (zygotic nucleus) within a single organism. Parthenogejiesis, or the de- 

 velopment of a gamete without syngamy, has been reported but its status 

 in Protozoa is uncertain. Typical conjugation involves the exchange of 

 haploid pronuclei (gametic nuclei) between two paired organisms, the 

 formation of a synkaryon in each, and then nuclear reorganization. 



Meiosis in relation to the life-cycle 



A reduction of the chromosomes to the haploid number may occur 

 in gametogenesis {gametic meiosis), in an early division of the zygote 



TABLE 2. 1. TYPES OF MEIOSIS IN PROTOZOA 



Gametic 



Zygotic 



Mastigophora 



Notila proteus (65a) 

 Paradinium poucheti (40) 



Sarcodina 



Actinophrys sol (18) 



Foraminiferida (185, 186, 187, 188) 



Gregarinida 



Monocystis spp. (36, 184, 190) 

 Urospora lagidis (189) 



Haemosporidia 



Plasmodium falciparum, P. vivax, 

 probably gametic (168) 



Cnidosporidia 



Ceratomyxa blennius (198) 

 Guyenotia sphaerulosa (194) 

 Myxidium gasterostei (199) 

 M. incurvatum (193) 

 Myxobolus guyenoti (192) 

 Sphaeromyxa sabrazesi (193) 

 Triactinomyxon ignotum, T. legeri (169) 

 Tetractinomyxon intermedium (118) 

 ^schokkella rovignensis (92) 



Mastigophora 



Euconympha imla (65b) 

 Glenodinium bibiniensijorme (74) 

 Oxymonas doroaxostylus (64) 

 Phytomonadida (202, 213, 213a, 257) 

 Saccinobaculus ambloaxostylus (65) 

 Trichonympha (62) 



Gregarinida 



Actinocephalus parvus (237) 

 Apolocystis elongata (204) 

 Diplocystis schneideri (121) 

 Gregarina blattarum (225) 

 Stylocephalus longicollis (103) 

 ^gosoma globosum (197) 



Coccidia 



Adelea ovata (102) 

 Adelina cryptoceri (254) 

 A. deronis (112) 

 Aggregata eberihi ild, 11) 

 Karyolysus zuluetei (209) 

 Klossia helicina (191) 

 Ovivora thalassemae (170) 



