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and soils of coastal dunes (Verhoeven, 2002). 
 Finally, there have been a few reports of colpodeans
as symbionts, probably commensals, within other 
organisms. A report by Powers (1933) of a Colpoda
from the sea urchin intestines has never been con-
firmed. Reynolds (1936) reported Colpoda as a 
facultative parasite of land slugs . Colpoda species 
have also been collected from the feces of deer 
(Bradbury & Outka, 1967) and amphibians and 
 reptiles (Fernández-Galiano, Fernández-Galiano, 
& Madrigal-Sesma, 1986). Fernández-Galiano 
et al. (1986) concluded that this is likely due to 
ingestion by these animals of resting cysts attached 
to vegetation or in soil ; the colpodids probably do 
not excyst in the intestinal environment. 
 The extreme body size range of colpodeans 
from 10 µm to over 500 µm is correlated with a 
similar breadth in the prey that can be consumed 
by different members of this class. Bacteria and 
 picocyanobacteria , like Synechococcus , are the 
typical prey of the smaller species of Colpoda
and Cyrtolophosis (Griffiths, 1986; Iriberri, Ayo, 
Santamaria, Barcina, & Egea, 1995; Šimek, 
Macek, Pernthaler, Straškrabová, & Psenner, 1996; 
Taylor & Berger, 1976). Colpoda may consume 
almost 1,000 bacteria per ciliate per hour (Hadas, 
Malinsky-Rushansky, Pinkas, & Cappenberg, 
1998). Moderate-sized species can consume chlo-
rophyte and cryptophyte algal cells (Skogstad 
et al., 1987; Wenzel & Winkler, 1984). Although 
some Colpoda species can ingest whole the cells 
of the yeast Saccharomyces (Wenzel & Winkler, 
1984), the grossglockneriid colpodids apparently 
specialize on fungi with chitinous cells walls, 
which these ciliates penetrate with their tube-like 
cytopharynx (Petz, Foissner, & Adam, 1993). 
Finally, the larger colpodeans can ingest flagel-
lates and other ciliates , including other colpodeans 
(Bradbury & Olive, 1980; Claff, Dewey, & Kidder, 
1941; Foissner, 1990). Woodruffia metabolica
appears to have a preference only for Paramecium
species (Johnson & Larson, 1938; Salt, 1967). 
 The growth rates of colpodeans can be predicted 
by the amount of macronuclear DNA, and are 
generally related to cell size : the larger the cell 
size , the more macronuclear DNA, and the slower 
the growth rate (Wickham & Lynn, 1990). The 
smaller species of bacterivorous colpodeans have 
been characterized as r -strategists with doubling 
times often less than 6 h (Drake & Tsuchiya, 1977; 
Lüftenegger, Foissner, & Adam, 1985). These col-
podids commonly divide twice in a division cyst 
and may compose the majority of the species in 
extreme habitats (Foissner, 1994c). At the same 
time, they are not good competitors against more 
K -selected species , like Paramecium , which appar-
ently can exclude Colpoda species from favorable 
habitats (Maguire, 1963a). The larger colpodeans, 
such as Bursaria and Woodruffia , have much 
longer doubling times, in the order of 12 h (Salt, 
1967), and might be typified as K -selected forms . 
 Colpodeans do not typically harbor symbionts. 
Endosymbiotic Chlorella have been described as 
mutuals in Paracondylostoma , Platyophrya , and 
Thylakidium species (Foissner, 1993a; Foissner & 
Kreutz, 1998; Kawakami, 1991). Parasites of colpo-
deans include the flagellate Spiromonas (Foissner & 
Foissner, 1984), Ciliatosporidium , a presumed micro-
sporidian (Foissner & Foissner, 1995), and the pro-
teomyxid -like Endemosarca (Erdos & Olive, 1971). 
 Suctorians can also be parasites/predators of larger 
 colpodeans , like Bursaria (Jankowski, 1973d) while 
 insect larvae and cladocerans are among the metazoan 
predators of these ciliates (Addicott, 1974; Cochran-
Stafira & von Ende, 1998; Jack & Gilbert, 1993). 
 A discussion of the life history of the Class 
 COLPODEA must include some aspects of the 
 resting or resistant cysts of these ciliates. The 
literature on this aspect of their biology, crypto-
biosis , is significant and has been reviewed most 
recently by Gutiérrez, Izguierdo, Martín-González, 
& Callejas, (1998b). Colpoda species have sur-
vived from 5 years (Dawson & Hewitt, 1931) to 
38 years (Goodey, 1915) in laboratory settings so 
it is likely that their survivability under natural 
conditions might be even more extensive. As with 
other ciliates, encystment may also be stimulated 
by reduced abundances of prey (Barker & Taylor, 
1931; Johnson & Evans, 1941; Salt, 1967) and 
also increasing concentrations of ions, such as 
Ca+2 , Na + , and K + , possible signals for impend-
ing desiccation (Yamaoka, Watoh, & Matsuoka, 
2004). Excystment is stimulated by the presence 
of prey and excystment rate and “efficiency” can 
be dependent, for example, upon the quality of 
the food preceding encystment (Wenzel & Meier-
Tackmann, 1975). Earlier physiological research 
(e.g., Barker & Taylor, 1931; Beers, 1945, 1948; 
Johnson & Evans, 1939; Taylor & Strickland, 
1939) was followed by research on the “cell biol-
ogy” of encystment in the early days of electron 
microscopy. Kawakami and Yagiu (1964) com-
pleted their sixth paper on the changes in the fine 
structure of Colpoda cucullus during its life cycle, 
having described the formation of the cyst wall 
and the excystment of the ciliate. The cyst wall is 
composed of two layers, an outer ectocyst and an 
inner endocyst, probably created by exocystosis of 
the cortical mucocysts (Martín-González, Benitez, 
Palacios, & Gutiérrez, 1992b; Ruthmann & Kuck, 
1985; Tibbs, 1968). Freeze-etching suggests a third 
outer mucous layer in Colpoda (Janisch, 1980). 
The resting cyst of Bursaria has a conspicuous 
emergence pore (Foissner, 1993a) and may have 
a fibrous middle or mesocyst layer connecting the 
ectocyst and endocyst (Sergejeva et al., 1995). The 
 cyst wall components of Colpoda species are rich 
in glutamic acid while its glycoproteins have high 
mannose content (Izquierdo, Martín-González, 
Diaz, & Gutiérrez, 1999; Tibbs & Marshall, 1970). 
The profiles and distributions of glycoproteins may 
change in the cyst wall as the cysts age (Chessa 
et al., 2002). Since ciliature and infraciliature 
are partially, but not completely, resorbed during 
 encystment , colpodean cysts are typed as par-
tial kinetosome-resorbing cysts (Martín-González, 
Benitez, & Gutiérrez, 1992a). 
 Gutiérrez, Izguierdo, Martín-González, & Callejas, 
(1998b) have argued that colpodid cystment serves 
as an interesting model for exploration of the cell 
and molecular biology of cryptobiosis , a life history 
feature common to both prokaryotes and eukaryo-
tes. Encystment requires RNA and protein synthesis 
(Ruthmann & Kuck, 1985). In the cryptobiotic state, 
there is protein turnover and evidence for encystment -
specific mRNA (Benitez & Gutiérrez, 1997; Gutiérrez 
& Martín-González, 1990). In addition to cytoplasmic 
changes, the macronucleus in particular undergoes sub-
stantial changes during this process (Gutiérrez, Martín-
González, & Callejas, 1998a). The macronuclear 
chromatin condenses into large bodies several times 
the size of those in interphase cells (Frenkel, 1992; 
Popenko, Cherny, Ivanova, & Yakovleva, 1998a). This 
process is accompanied by extrusion of macronuclear 
fragments, a process that appears to regulate the DNA 
amount in proportion to cell size (Morat, Chessa, & 
Crippa-Francheschi, 1981). Extrusion of condensed 
chromatin may also occur at excystment (Chessa, 
Gallus, Tiano, Trielli, & Corrado, 2001). 
12.2 Life History and Ecology 247
248 12. Subphylum 2. INTRAMACRONUCLEATA: Class 6. COLPODEA
 It would be remiss not to add to the discussion 
of cryptobiosis in colpodeans a description of the 
structure and development of the aerial sorocarps 
produced on a stalk by Sorogena stoianovitchae , 
which was originally found in tropical habitats 
(Olive, 1978), but has now been found in the 
canopy of European deciduous