ChapterProtozoa

1、1. The main characteristics of protozoan 1.1 Protozoa display unicellular organization. All functions must be carried out within the confines of a single plasma membrane. They are more complex than any particular cell in higher organisms. nsizes range from 2-3m to 3mm, and many protozoans (原生動物的原生動物

2、的) are organizationally very complex, as befits organisms in which one cell performs every function of a living creature. n1.2 In some protozoa, individuals group to form colonies, associa-tions of individuals that are not dependent on one another for most functions. 1.3.2 Locomotion: Many protozoa

3、are motile, using pseudopodia, cilia or flagella. Pseudopodia are temporary cell extensions of amoebae (變形蟲變形蟲). The cytoplasm (細胞質(zhì)細胞質(zhì)) is differentiated (分化分化) into two regions. The portion of the cytoplasm just beneath the pellicle is called ectoplasm (外質(zhì)外質(zhì)). It is relatively clear and firm. The i

4、nner cytoplasm, called endoplasm (內(nèi)質(zhì)內(nèi)質(zhì)), is usually granular and more fluid. The conversion of cytoplasm between these two states makes amoeba accomplish two kinds of functions: locomotion and phagocytosis (吞噬作用吞噬作用). n1.3.5 Reproduction: reproduction is usually both asexual and sexual, although som

5、e species are known which do not exhibit sexual reproduction ( e.g. some amoebas).2 protozoan taxonomynProtozoan PhylanPhylum Mastigophora (flagellates) nPhylum Sarcodina (Amoebas)nPhylum Apicomplexa(or Microspora )nPhylum Ciliophora (Ciliates ) Phylum Mastigophora: nMembers of the Mastigophora use

6、flagella (鞭毛鞭毛) for feeding and /or locomotion . Flagella may produce two-dimensional, whiplike movements or helical (螺旋狀的螺旋狀的) movements that push or pull the protozoan through its aquatic medium.Sarcodina (the amoebas ) The phylum Sarcodina (肉足蟲肉足蟲) includes amoebas (變形蟲變形蟲) and their relatives wh

7、ich possess pseudopodia (偽足偽足). They primarily use pseudopodia for locomotion, and many forms have some form of skeleton or “test”. Two of the most ecologically (生態(tài)學的生態(tài)學的) (and geologically地理學的地理學的) important sarcodines are the Foraminifera (有孔蟲目有孔蟲目) and the Radiolaria (放射放射蟲目蟲目) . lForaminifera (有

8、孔蟲目有孔蟲目), Heliozoa (太陽蟲目太陽蟲目) and radiolarian (放射蟲放射蟲) are sarcodine protozoans which possess shells or skeletal structures, often with very elaborate and sophisticated (復雜的復雜的) architectures (結(jié)構(gòu)結(jié)構(gòu)). Long narrow pseudopodia, axopodia (軸偽足軸偽足), are frequently present. The skeletons of these groups ar

9、e important constit-uents (成分成分) of some sedimentary (沉積的沉積的) rocks. Most Foraminiferans (有孔蟲目有孔蟲目) have calcareous (石灰質(zhì)的石灰質(zhì)的)tests, and may be very abundant in the plankton (浮游生物浮游生物)or in the benthos (海洋深處海洋深處). The calcareous tests deposited by foraminiferans over millions of years form a signifi

10、cant part of the ocean floor “ooze (滲出滲出) in many areas. Radiolarians (放射蟲放射蟲)are also an important component of the phytoplankton (浮游植物浮游植物), especially in warmer waters. They have also been abundant in the past, and like the Foraminifera may form a significant part of the sediment ooze on many oce

11、an floors. 太陽蟲太陽蟲nSome amoebas are commensals (共生共生) or parasites, inhabiting the alimentary (消化消化) tracts of higher animals. Entamoeba histo-lytica (痢疾內(nèi)變形蟲痢疾內(nèi)變形蟲) invades (侵入侵入) human intestinal (腸的腸的) tissues and causes amoebic dysentery (痢疾痢疾). 痢疾阿米巴痢疾阿米巴(Entamoeba histolytica) 砂殼蟲砂殼蟲（Difflugia）

12、有孔蟲有孔蟲大變形蟲大變形蟲Apicomplexa(Sporozoans) Most members of the phylum belong to the taxon (分類群分類群) formerly known as the Sporozoa (孢子蟲孢子蟲). Feeding is by micropores (微孔微孔). These protozoa have no locomotory extensions of the body and all species are parasitic. Most sporozoans are intracellular parasites.

13、 The apical complex seems to be structurally designed to assist host cell penetration (穿入穿入). Malaria parasites (Plasmodium 瘧原蟲瘧原蟲 ) and coccidians (球蟲球蟲) are among the most import-ant sporozoan parasites. Reproduction usually includes asexual and sexual phases. The infective sporozoite (子子孢子孢子) inv

14、ades the host and undergo further multiple fission (schizogony裂殖生殖裂殖生殖), eventually forming gametes (配子配子) which fuse to give a zygote (合子合子). Meiosis (減數(shù)分減數(shù)分裂裂) in the zygote results in new sporozoites. Plasmodium spp.瘧原蟲瘧原蟲 are sporozoans. Four species which parasitize erythrocytes (紅細胞紅細胞) in hum

15、ans cause malaria (瘧疾瘧疾) : anopheline (按蚊按蚊) mosquitos (蚊子蚊子) act as intermediate (中間的中間的) hosts. The life cycles of Plasmodium (three phases) Schizogony: Schizogony is multiple fission of an asexual stage in host cells( first in liver cells and later in red blood cells) to form many more individual

16、s, called merozoites裂殖子裂殖子 that leave the host cell and infect many other cells. Gametogony: Some of the merozoites undergo gametogony(in red blood cells), which produce microgametes and macro-gametes, then a microgamete fertilizes a macrogamete to produce a zygote (in the body of mosquito). Sporogo

17、ny: The zygote undergoes meiosis, and the resulting cells divide repeatedly by mito-sis,which produces many rodlike sporozoites子孢子子孢子 in the oocyst (卵囊卵囊). Sporozoites infect the cells of a new host by a mosquito bite. The symptoms (癥狀癥狀) of malaria (痢疾痢疾) recur periodically and are called paroxysms

18、 (陣發(fā)陣發(fā)). Chills and fever (寒熱寒熱) correlate with the maturation of parasites. Plasmodium Feeding is via a mouth and a cytopharynx (胞咽胞咽) , (ingest food in a specialized region analogous (相似的相似的) to a mouth, called the cytopharynx) leading to the fluid, interior cytoplasm (細胞質(zhì)細胞質(zhì)) where the food vacuoles