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A QUANTITATIVE MORPHOLOGICAL AND ECOLOGICAL
STUDY OF PROTOZOA POLLUTING TAP WATER
IN MEXICO ClTY
F. RIVERA,A. ORTEGA, E. LÓPEZ-OCHOTERENA,
and M. E. PAZ
Protozoology Section, Department of Histology, Faculty of Medicine,
National Autonomous University of Mexico, University City,
Mexico 20, D.F. Mexico, and Laboratory of Protozoology,
Faculty of Sciences, National Autonomous University of Mexico,
University City, Mexico 20, D.F. Mexico
RIVERA, F., ORTEGA,
A., LÓPEZ-OCHOTERENA,
E. & PAZ,M. E. 1979. A quantitative
morphological and ecological study of protozoa polluting tap water in Mexico City.
Trans. Amer. Micros. Soc., 98: 465469. The stiidy was performed using samples obtained from the tap water of the most populated area of the Federal District in Mexico
City. The organisms were concentrated through filtration procedures and subsequently
cultured in sterile wheat infusions. The cultures were obsemed for a week and the
taxonomic identification was achieved to the leve1 of genus and species. Most commonly
found were flagellates (84.58%), followed by amoebae (13.38%) and ciliates (1.86%).
The greatest number (17) of species were found in the eastern region of the Federal
District, though 16 were taken from the central region. Richest in numbers of organisms
per m1 were Bodo edux (8636/m1), cysts of flagellates and ciliates (4484/m1), cysts of
amoebae of the Vahlkampfiidae (2083/m1), and trophozoites of the genus Vahlkanapfru
itself (14081ml). Among detected species, only those belonging to the Vahlkampfiidae
and Hartmannellidae might have pathogenic effect on human beings. However, several
species were found red which denotes a high degree of organic pollution in the supposedly potable waters of the Federal District.
The fresh-water free-living protozoa have a cosmopolitan distribution as
has been pointed out by Bovee (1957), Cairns (1962), Corliss (1973), and
others. It is also well known that the diversity, density, and kind of protozoa
present in waters may be used as indicators of their quality and potability
(Cairns & Dickson, 1972). A widely used method to determine pollution is
one employed in Europe named "Saprobic System" (Kolwitz & Marsson,
1908; see also Cairns et al., 1972).
Therefore, since protozoa can pollute the drinkable waters which flow
through the distribution duct system of a city, a study on this matter is well
justified, especially in countries siich as Mexico where the knowledge on
ecology of free-living protozoa is scant and mostly superficial.
MATERIALS
AND METHODS
Some 25 random s a m ~ l e sof one gallon each were obtained directlv from
the faucets of private hiuses receiviGg water from the distribution duit system that supplies the northern-eastern areas of the Federal District in Mexico
City.
Next, 95-liter water samples were filtered through an Ottawa sand column
of 4 cm length and 1.5 cm interna1 diameter. A screen of cotton mesh was
placed over the bottom and held in place with a hose clamp. The concentrated
protozoa were freed from the sand after it had been removed from the column
and thoroughly washed with distilled water. Then the organisms were in-
Sample
Total number of organisms per sample
Percent
Temperature (C)
DH
Bodo edax Klebs
Bodo saltans Ehrenberg
Euglena viridis Ehrenberg
Anisonema truncatum Stein
Anisonema emar~inatumStokes
Ochromonas ~ y g s o t z k i
unidentified species
Trentonia flagellata Stokes
Paranema trichophorum (Ehrenberg)
Acanthamoeba astronyxis Ray & Hayes
Acanthamoeba castellanii Douglas
Amoeba verrucosa Ehrenberg
Flabellula mira Schaeffer
Hartmannella exundans Page
Naegleria gruberi (Schardinger)
trophozoite stage
flagellate stage
Vahlkampfia vahlkampfi Chatton
Colpidium colpoda (Ehrenberg)
Colpoda cucullus O. F. Müller
Colpoda steini Maupas
Sathrophilus agitatus (Stokes)
Stylonychia pustulata Ehrenberg
Tetrahymena pyriformis (Ehrenberg)
Chilodonella cucullulus O. F. Müller
Chilodontopsis vorax (Stokes)
Platyophrya lata Kahl
Organisms
1
2
2
3
4
5
2
546
97
6
5
690
560
7
5
8
547
9
TABLE 1
Incidence per m1 of organisms detected in 25 samples from Federal District
10
12
11
12
13
4,546
14
Sample
Bodo edax Klebs
Bodo saltans Ehrenberg
Euglena ijiridis Ehrenberg
Anisonema truncatum Stein
Anisonema emarginatum Stokes
Ochromonas Wyssotzki
unidentified species
Trentonia flagellata Stokes
Paranema trichophorum (Ehrenberg)
Acanthamoeba astronyxis Ray & Hayes
Acanthamoeba castellanii Douglas
Amoeba verrucosa Ehrenberg
Flabellula mira Schaeffer
Hartmannella exundans Page
Naegleria gruberi (Schardinger)
trophozoite stage
flagellate stage
Vahlkampjia vahlkampji Chatton
Colpidium colpoda (Ehrenberg)
Colpoda cucullus O. F . Müller
Colpoda steini Maupas
Sathrophilus agitatus (Stokes)
Stylonychia pustulata Ehrenberg
Tetrahymena pyriformis (Ehrenberg)
Chilodonella cucullulus O. F . Müller
Chilodontopsis voraz (Stokes)
Platyophrya lata Kahl
Total number of organisms per sample
Percent
Temperature (C)
PH
Organisms
15
16
17
18
19
TABLE 1
Continued
20
21
22
23
24
25
Total
Percent
468
TRANS. AMER. MICROS. SOC., VOL. 98, NO. 3, JULY 1979
oculated into sterile wheat infusions, covered with sterile cotton caps, and
incubated at roorn temperature (15-25 C) for a period of seven days.
Identification and counting of isolates of each culture were performed daily,
using a photornicroscope (phase contrast, 40 x and 100 X ) and a Neubauer
counting chamber.
Identification and incidence of the concentrated speciinens per ml, as well
as such variables as temperature and pH from the 25 tap water samples are
given in Table 1. Only the trophozoite stage and the active form of the organisms observed are considered in this table, although we have also found
the encysted stage of some ciliates, flagellates, and arnoebae as well as some
palmella stages of phytoflagellates. Total numbers of organisms and percentages of species are also included in the table.
The most polluted tap waters were those from the eastern-western sides of
the explored area of the Federal District, followed successively by northern,
central, and southern sides. The most comrnonly found protozoa were flagellates, followed by amoebae and ciliates.
Among the flagellates, the most abundant forms were Bodo edax, B. saltans,
and Ochromonas sp. Within the amoeboid group, most frequently found were
members of the Vahlkampfiidae family (trophozoic as well as cystic stages),
mainly of the genus Vahlkampjia itself. Among ciliates, most abundant were
Colpidium colpoda, Colpoda steini, and Tetrahymena pyriformis.
This is the first research ever carried out in Mexico concerned with protozoa
that may act as pollutants or as indicators of nonpotability of tap water. The
results clearly demonstrate that the theoretically drinkable waters of the Federal District contain protozoa, either in their trophozoic form or cystic stage.
Some of the detected organisms belong to genera that may be potentially
pathogeriic when inoculated into experimental animals, viz., Naegleria and
Acanthamoeba.
We also discovered organisms that are widely considered to be indicators
of pollution in drinkable waters. For example, we found such saprobic organisms as Euglenu viridis, Colpidium colpoda, Sathrophilus agitatus; and
such mesosaprobic forms as Bodo edax, B. saltans, and Colpoda cucullus.
Another interesting finding was that some of the sainples examined did not
show any kind of protozoa at any time during our observations, only bacteria
(see Table 1). Still other samples showed only cystic stages of flagellates,
amoebae. or ciliates.
Some óf the microorganisms found have not been reported before in Mexico
(i.e., they are not listed by López-Ochoterena & Roure-Cane, 1970). These
include: Anisonema truncatum, Chilodontopsis vorax, Flabellula mira,
Hartmannella exundans, Sathrophilus agitatus, and Trentonia jiagellata.
The bacteriophagous protozoa detected in the samples, which may be considered as decontaminating organisms since they capture bacteria, include
Ochromonas sp., Peranema trichophorum, Acanthamoeba astronyxis, A. castellanii, Amoeba verrucosa, Flabellula mira, Hartmannella exundans, Naegleria gruberi, Vahlkampjia vahlkampji, Colpidiutn colpoda, Tetrahymena
pyriformis, Chilodonella cucullulus.
BOVEE,E. C. 1957. A small amoeba of fresh water lakes and ponds, Majorella cultura. Tran-s.
Amer. Micros. Soc., 80: 54-62.
CAIRNS,J., JR. 1962. The environmental requirements of fresh-water protozoa. Zn Biological
Problems in Water Pollution, 3rd Serninar, August 1962, PHS Publ. No. 999-WP-25, pp.
48-52.
CAIRNS,J., JR. & DICKSON,K. L. 1972. An ecosystematic study in the South River, Virginia.
Water Res. Ctr., Virginia Polytechnic Institute, Blacksburg, Virginia, Bull. 54, pp. 1-104.
CAIRNS,J., JR., LANZA,G. R. & PARKER,B. C. 1972. Pollution related structural and functional
changes in aquatic communities with einphasis on freshwater algae and protozoa. Proc.
Acad. Nat. Sci., Philadelphia, 124: 79-124.
CORLISS,J. 0. 1973. Protozoan ecology: a note on its current status. Amer. Zool., 13: 143-148.
KOLWITZ,R. & MARSSON,M. 1908. 0kologie der pflanzlichen Saprobien. Ber. Deutsch. Bot.
Ges., 26: 509-519.
L~PEZ-OCHOTERENA,
E. & ROURE-CANE,M. T. 1970. Lista taxonómica comentada d e protozoario~d e vida libre d e México. Rev. Soc. Mex. Hist. Nat., 31: 23-68.