Freeliving Protozoan Diversity in Indian Wetlands
Bindu. L
Zoological Survey of India, M-Block, New Alipore, Kolkata, India
E-mail : [email protected]
Abstract
Despite the important role in the food chain of wetland ecosystems, studies on the freeliving protozoan
fauna from various wetlands in India is meager. Importance of protozoa as bioindicators for pollution and
environmental biomonitoring has been recognized since long particularly in water purification plants and
activated sludge processes (Kelkwitz and Marson, 1908). Several scattered reports are available in the
literature including the ciliates reported recently by the present author from wetlands of Kolkata megacity.
But the occurrence and distribution of free-living protozoa in different wetlands of India have not so far
been analysed and evaluated and hence the present communication. Several investigators recorded the
freeliving protozoa from ponds and lakes in India since 1840s when Cantor (1842) referred about the
occurrence of six species of freshwater protozoa from Calcutta while Chilton (1921), Mahajan and Nair
(1965), Mahajan et al. (1981), Das et al. (1993), Das (1995), Mukherjee and Das (2000) and Bindu (2008,
in press) reported an appreciable number of specises from freshwater and brackishwater wetland
ecosystems across India.
According to the present estimate 1247 species of freeliving protozoa have been recorded from India
including the estuarine and marine species. In the present paper an inventory analysis of freeliving
protozoans from wetlands of India has been made highlighting one freshwater and one brackishwater
wetland of International importance of India viz., Bharatpur wetland, Rajasthan and Chilka lake, Orissa
representing 117 species and 61 species respectively. Also an indepth case study emphasis is given to the
freeliving protozoa of Kolkata wetlands in West Bengal representing altogether 102 species comprising of
flagellates (4 species), rhizopods (15 species), and ciliates (83 species) that occur in the bottom ooze and
amongst vegetation of ponds, tanks, and lakes including Rabindra Sarovar, a national lake located in the
heart of Kolkata metropolis.
Key words : Bioindicators, Pollution, Protozoa, Wetlands,
1. Introduction
Importance of protozoa as bioindicators for
conveniently
used
for
environmental
pollution and environmental biomonitoring has
biomonitoring , particularly for ecological
been recognized since long particularly in water
monitoring of water quality(Liebmann, 1962;
purification plants and in activated sludge
Bick, 1973; Curds, 1973; Small, 1973; Madoni
processes
and Ghetti, 1981; Salanki, 1986; Ricci, 1995).
(Kolkwitz
and
Marsson,
1908).
Several field and experimental studies have been
As early as 1972 the World Health
carried out in this regard and results obtained
Organisation brought out a book entitled
therefrom
‘Ciliated Protozoa : An illustrated guide to the
support
that
protozoa may be
1
in
representative ciliates, degree of pollution of a
freshwater biology’ written by Hartmut Bick.
particular water body may be determined It
This pioneering contribution reveals that each
needs mentioning here that ecological resistence
species of ciliate is characterized by its own
and preference of some species may vary
physical and chemical valencies and therefore its
considerably from one population to the other
presence in
(Ricci, 1995). Accordingly, saprobic valency and
species
used
as
biological
indicators
abundance may indicate
the
indicator value of a species may also vary.
qualitative state of any waterbody. Based on
saprobic valancies and indicator values of the
1.1. Role of protozoa in water purification systems
Several major taxonomic groups of protozoa,
mucous substances to facilitate flake formation
viz., flagellates, naked and testate amoebae,
and successive sedimentation(Curds, 1963). It
actinopods and ciliates occur in biological
has been established further that the quality of
sewage treatment plants. Amongst these , ciliated
the entire population structure rather than
protozoa are the most significant component. It
presence or absence of any single species can be
has been shown experimentally that ciliates
used as precise indicator of water quality (Ricci,
actively contribute to the regulation of the entire
1995). Thus occurrence of dominating protozoan
complex of purification plants by regulating
groups in a water purification plant may be good
bacterial population and controlling BOD level
indicators of the condition of the plant as shown
(Curds, 1973), controlling pathogenic and faecal
in Table-1.
bacteria (Curds and Fey, 1969) and releasing
Tab. 1 Protozoan groups as indicators of water purification system
Sl. No
Name of dominant protozoan groups
1.
Small flagellates
2.
Large flagellates
3.
Small swimming ciliates(<50µm)
4.
5.
6.
7.
Large swimming ciliates
Crawling and sessile ciliates
Suctoria
Small amoebae (usually coupled with
flagellates)
Condition of water purification plant
Too much organic matter, insufficient oxygen and
effluent with fermented products.
Less organic matter in the effluent
Sludge immature, too rapid water influx and too
little oxygen
Immature flakes in too rich organic medium
Well formed flakes and low BOD value
Slow water influx and less organic matter
Substances very less mineralised, bad depuration
and high BOD value
Occurrence of the ciliate, Metopus sp. in any
Sprodinium
in
putrefying
sludge are
the
water body indicates the presence of hydrogen
indicators of the self purification process which
sulphide (Bick, 1972). Presence of this species
has been stopped due to lack of oxygen and
and its associated ciliates belonging to the genera
presence
Caenomorpha,
Epalxella,
Pelodinium
and
2
of
high
concentration
of
H2S.
Inspite of the above mentioned importance
been made including an indepth case study of
of these free-living protozoa, the occurrence and
freeliving protozoa of wetlands of Kolkata, West
distribution of these organisms in different
Bengal by the present author. According to the
wetlands of India have not so far been seriously
present estimate 1247 species of freeliving
analyzed and evaluated and in the present
protozoa have been
communication
including the estuarine, marine and moss
an
inventory
analysis
of
recorded
from
India
dwelling forms.
freeliving protozoans from wetlands of India has
2. Methodology
For the collection of freshwater protozoa
Schaudinn’s fixative and Carnoy’s fluid
water samples along with some algae, water
were used for making permanent slides of
weeds, bottom ooze and flocculent matter arising
freeliving ciliates. The first one is effective for
out of washing of water weeds and aquatic plants
keeping the exact natural shape of the specimen
were collected and kept in wide mouthed
while the second one is good for studying
sampling jars made up of glass. These jars were
nuclear
then brought to the laboratory and kept for few
haematoxylin and Delafield’s haematoxylin were
days, keeping their lids open for considerable
used for staining the ciliates. In some cases dry
increase in protozoa population occurring in
silver impregnation method was employed to
those
study their infra structures. These slides were
samples.
The
samples
were
then
thoroughly examined under the light microscope
ciliates
For
were
isolated
Heidenhain’s
iron
mounted in DPX.
from time to time.
Freeliving
structure.
preparing
permanent
slides
of
by
freshwater testacid rhizopods empty tests were
micropipette and examined in living condition by
isolated from the bottom ooze of the samples.
keeping them in a natural medium. Sometimes
Testacids were also collected by squeezing
methocyl solution was used for slowing down
different parts of the aquatic vegetation including
the movement of fast moving ciliates for the
their roots and submerged portion of leaves. The
study of their internal structures in situ under
testacids were placed in microslides, air dried
light microscope. Sometimes Lugol’s solution
after two or three washings in absolute alcohol
was added as killing agent and for detecting
and then mounted in DPX.
peripheral organellae.
3. Results
In the present communication an inventory
occurrence of six species of freshwater protozoa
analysis of freeliving protozoans from wetlands
from West Bengal. Subsequently Wallich (1864)
of India has been made including the work of the
recorded four species of Difflugia from Gangetic
present author in Kolkata wetlands. The first
Sundarbans of Lower Bengal. Ghosh(1918-
report of freeliving protozoa from India dates
1929) published a series of papers reporting 29
back to 1842 when Cantor referred about the
species of freeliving ciliates and one species of
3
testacid rhizopod from Kolkata and its nearby
31 families and 12 orders were reported. Of these
localities. Mahajan and Nair (1965) published
prostomatid ciliates represent the highest number
the occurrence of 19 species of freeliving ciliates
(13 spp.) followed by heterotrichids
from Kolkata and its vicinity. Mukherjee and
hypotrichids (9 spp. each). Study has also made
Das (2000) recorded 5 species of ciliates from
by Mahajan et al. (1981) on free-living protozoa
Renuka wetland which is a Ramsar site in
in another Ramsar site , Bharatpur Bird
Himachal Pradesh. As part of the Chilka lake
Sanctuary situated in eastern Rajasthan between
expedition, which is also a Ramsar site in Orissa,
27º 07'-27º 12' N latitudes and 77º 29'-77º 33' E
a detailed study has been made on the freeliving
longitudes . Protozoan species belonging to 78
protozoa by Das (1995), located along the east-
genera and 117 species were recorded from
coast of India between latitudes 19º28' and 19º
Bharatpur wetland ecosystem. Following severe
54' N and longitudes 85º 06' and 85º 35' E. Water
drought during 1979, most of the protozoans
samples were collected from 35 stations and 61
were adversely affected but populations of
species of ciliates under 37 genera belonging to
Actinobotina and Euplotes increased.
and
Tab. 2 Orderwise distribution of freeliving protozoa from Chilka Lake
Orders
Number of species
Prostomatida
13
Pleurostomatida
5
Karyorelictida
2
Trichostomatida
2
Nassulida
2
Cryptophorida
3
Hymenostomatida
4
Scuticociliatida
8
Peritrichida
2
Heterotrichida
9
Oligotrichida
2
Hypotrichida
9
A detailed study of the freeliving protozoa of
perusal of this distribution list reveals that out of
wetlands of West Bengal was made by Das et al.
248 species only two species, both ciliates, viz.,
(1993) and of Kolkata wetlands by Bindu (2008,
Coleps hirtus and Paramecium caudatum have
in press). A total of 248 species of freeliving
been reported from all the 17 districts of West
protozoans under 124 genera belonging to 2
Bengal and seven other species have been found
phyla, 2 subphyla, 7classes, 29 orders and 76
from 10 or more districts of the state. From the
families were recorded from West Bengal. A
distribution list it is evident that number of
4
freeliving protozoan species collected from
the intensive surveys in Kolkata when compared
Kolkata is considerably large compared to any
to the other districts.
other district of West Bengal. This may be due to
Tab. 3 District wise distribution of Protozoa in wetlands of West Bengal
Number of species of
Names of districts
Flagellates
Rhizopods
Ciliates
Total
Bankura
_
20
13
33
Barddhaman
1
8
10
19
Birbhum
_
8
9
17
Kolkata
4
15
83
102
Darjiling
_
3
8
11
Howrah
1
9
15
25
Hugli
9
24
26
59
Jalpaiguri
_
7
7
14
Koch Bihar
_
15
9
24
Maldah
_
8
15
23
Medinipur
1
18
3
22
Murshidabad
_
8
12
20
Nadia
8
21
7
36
North24Parganas
9
23
18
50
Puruliya
_
10
10
20
South24Parganas
13
37
27
77
West Dinajpur
_
16
12
28
4. Conclusion
Although workers have recorded the above
for pollution and environmental biomonitoring
mentioned freeliving protozoa from different
of waterbodies. It is, therefore, quite probable
Indian wetlands,
thorough
that number of species occurring in Indian
surveys were not so far done inspite of the
wetlands are many more than what is dealt
importance of these organisms as bioindicators
within this paper.
purposeful
and
5
Acknowledgment
The author is grateful to the Director, Zoological
Survey of India for providing necessary facilities
in connection with the present work.
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7