IJERD – International Journal of Environmental and Rural Development (2014) 5-1

Research articleerd

New Records of Rotifer Fauna in the Upper Cambodian
Mekong River Basin
SEANGHUN MEAS*
Centre for Biodiversity Conservation, Department of Biology, Faculty of Science,
Royal University of Phnom Penh, Phnom Penh, Cambodia
Email: meas_seanghun@yahoo.com

RATHA SOR
Centre for Biodiversity Conservation, Faculty of Science, Royal University of Phnom Penh,
Phnom Penh, Cambodia
Received 18 December 2012

Accepted 30 January 2013(*Corresponding author)

Abstract Rotifer samples were seasonally collected in 2010 from ponds, lakes, reservoirsand rivers in the upper part of the Cambodian Mekong River in Kratie, Stung Treng andRatanakiri Provinces. A 30 µm mesh plankton net was used to collect samples. The water
quality parameters: temperature, pH, electrical conductivity, turbidity and dissolved
oxygen were also collected from each of the sampled sites. A total of 175 species of
Monogononta Rotifers were found, 64 of which were new Cambodian species records.
This investigation brings the total number of rotifers identified from Cambodia to 260
species. Of the 4 habitat types, ponds had the highest species richness, followed by lakes,reservoirs and rivers.
Keywords rotifers, species richness, Mekong River basin, Cambodia

INTRODUCTION
Rotifers are microscopic zooplanktons that are mostly found in freshwater, although they have also
been recorded from saline waters and terrestrial environments, including moist tree bark. Rotifer
are very important to aquatic food webs as they provide a food source for other aquatic animals,
including larger zooplankton and fish larvae in both natural and human made habitats andimproving the water quality by the consumption of algae (Beres et al., 2005; Tasevska et al., 2010).
Several studies of rotifers have been conducted in Cambodia and new species records continue
to be found. Bēzins (1973) found several species, Anchitestudinella mekongensis, Brachionus
donneri, Filinia camasecla, and Lecane blachei in the Mekong River near Phnom Penh City. A
biomonitoring program along the Lower Mekong River Basin subsequently recorded at least 65
species in the Cambodian Mekong River basin (Davidson et al., 2006 & Vongsombath et al., 2009).
The number of rotifer species was substantially increased by Meas & Sanoamuang (2008) whofound 143 species, of which 102 species were new country records. Data have also been collected
on seasonal changes of plankton and zoobenthos in Tonle Sap Great Lake but the identity of thesespecies was not presented (Ohtaka et al., 2010). The first description of sessile rotifers was recentlyconducted and 23 species were found, all of them were new country records to (Segers et al., 2010).
Furthermore, at least 79 species of rotifer were found in ponds from the north of Cambodian
Mekong River basin, seventeen of them were new records in Cambodia (Min et al., 2011), one ofwhich Lepadella punctata is considered to be rare in Thailand (Chittapun et al., 2003). The mostrecent study found one hundred and seven species in lakes and reservoirs from the northern part of
the Cambodian Mekong River basin, twenty-five of them were new country records (Sor et al.,2011).
According to rotifer distribution known to Southeast Asia (Segers, 2001, 2007), most of thespecies found in Cambodia are considered common or cosmopolitan species, except a few whichwere endemic to Southeast Asia. These endemic species include Anchitestudinella mekongensis
Bērzinś, 1973, Brachionus murphyi Sudzuki, 1996, Cephalodella songkhlaensis Segers &Ⓒ ISERD

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IJERD – International Journal of Environmental and Rural Development (2014) 5-1

Pholpunthin, 1997, Keratella edmonsoni Ahlstrom, 1943, Lecane blachei Bērzinś, 1973, L.
superaculeata Sanoamuang & Segers, 1997, and L. thailandensis Segers & Sanoamuang, 1994.
OBJECTIVE
This investigation aimed to explore the diversity of rotifers in the Upper of Cambodian MekongRiver Basin from 4 different habitats within 2 different seasons in the year 2010.
METHODOLOGY
A total of 64 rotifer samples were seasonally collected from rivers, lakes, reservoirs, streams andponds (Table 1) in three provinces in northeast Cambodia (Fig. 1), Forty samples were collected in
the late dry season from 25th to 30th April 2010 from 4 habitat types, and twenty four samples werecollected in the late rainy season from 7th to 12th November 2010 from only 3 habitat types(excluding river samples) using a 30 micrometer mesh plankton net (Table 1). A sample wasobtained by dragging the net 15 times through open water in each habitat. All samples werepreserved by adding a small volume of 4% formalin. Environmental parameters measured at eachsampled locality included water temperature, pH, conductivity (pH/EC/TDS/Temperature, modelHI 98129 • HI 98130, HANNA Instruments company), turbidity (ISO Portable Turbidity meter,model HI 98713, HANNA Instruments company), and dissolved oxygen (Dissolved Oxygen Meter,model HI 9146, HANNA Instruments company). The locations of the sampling sites were recorded
using a Global Positioning System (GPS). The sampling sites are part of a detailed study toevaluate rotifer distribution and diversity in the upper part of the Cambodian Mekong River basin,
which in turn may serve as a baseline study for assessing the change of water quality in this region.
Rotifers were identified of species level under a compound microscope using published keys
(Segers, 1995; de Smet & Pourriot, 1997; Nogrady & Segers, 2002). Photographs of rotifers weretaken using an Olympus BX51 attached to the microscope. Species nomenclature follows Segers(2007).
Correlation analysis was carried out to determine whether there was any linear relationshipbetween species counts and the various environmental parameters measured.

Mekong River
Sesan River
LakeFig. 1 Study area
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8Pond

Sekong River
Srepok River
Reservoir

IJERD – International Journal of Environmental and Rural Development (2014) 5-1

Table 1 Number of samples in each habitat types
Habitat types
RiverPond
Reservoir
Lake
Total

Number of Samples
Late dry season
Late rainy season
20010
14555540
24

Total Numberof Samples
2024101064

Total Number ofSampled Localities
20
145544

RESULTS AND DISCUSSION
One hundred and seventy five species of rotifers were recorded from this study, 64 of which werenew Cambodian species records (Table 2). The highest number of species found was in a pond in
Stung Treng Province collected in April 2010 with 44 species (44 of 175 species= 25.14%),
followed by a reservoir sampled in November 2010 (39/175 species= 22.28%) also in Stung Treng
Province. The lowest number of species from a sample was collected from a pond in Ratanakiri
Province with only 3 species (3/175 species= 1.71%). However a sample from the Mekong River in
Kratie Province contained no rotifers.
Overall the highest number of species were found in ponds (e.g. a pond Stung Treng Province,
44 species), followed by lake and reservoir, with the river tending to support few species (0 species
at a Mekong River site in Kratie Province).
Common species were Keratella tropica (found in 42 of 64 samples = 67.18%), followed byAnuraeopsis fissa (41/64 samples = 64.06%), Lecane bulla (38/64 samples = 59.37%), A. coelata(36/64 samples =56.25%), Brachionus angularis and K. cochlearis (34/64 samples = 53.12%).
Fifty species were found in only one sample (1.56%).
Conductivity, turbidity, pH and temperature data obtained from ponds, lakes and reservoirs
were seasonally compared to the number of rotifer species collected from each of the habitats. Forconductivity, the number of species seems to be positively correlated in lakes and reservoirs while
it tends to be negatively correlated in ponds (Fig. 2), that is the lower the conductivity, the lower
the number of rotifer species expected. This finding is in agreement with the study of Jersabek(1995) that found the low numbers of rotifer species at sites with low conductivity. This is more
likely to be true in this study because ponds have a higher conductivity and support more species
than lakes and reservoirs which have a lower conductivity (Fig. 3).
350

Conductivity(µS/cm)
Conductivity(μS/cm)
Conduntivity(μS/cm)

300
PondLakeReservoir

250
200
150
1005000102030
Number of species

4050

Fig. 2 Correlation between number of species and the level of conductivity in ponds, lakes
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Turbidity (NCU)

1000

1000

800729

600

556

400
200
01.15

1.77

1.59

Conductivity (µS/cm)

400300305200100100
1100.01

Temperture (℃)

40

pH

0.01

0.01
36.5

35

34.2

32.9

26.1

26.7

30
25

26.9

20
10987654

8.87

8.9

8.81

6.43
4.94

Ponds

4.91

Lakes

Reservoirs

Fig. 3 Range of each water quality parameter in each habitat type
Water temperature is also considered to be one of the most important factors influencing therotifer community. In this study, the numbers of rotifer species were not significantly correlatedwith water temperature. This could result from the life history and adaptation of each species to aparticular temperature range; for example, Synchaeta sp. Nothola squamula, Polyarthra
dolichoptera, Brachionus angularis, Keratella quadrata and K. hiemalis were found out to be
negatively correlated with the water temperature (Devetter, 1998).
The other parameters were not found to be significantly different among the three habitat types.
The range value of each parameter in each habitat type from site to site. Among the three habitat
types, lakes showed a smallest (conductivity) and widest (turbidity) range values (Fig. 3).
Cosmopolitan: Found in at least five of the eight biogeographic regions of the world (Afrotropical,AFR; Antarctic, ANT; Australian, AUS; Nearctic, NEA; Neotropical, NEO; Oriental, ORI; Paciﬁc,PAC; Palearctic, PAL) according to Segers (2007).
CONCLUSION
This study increased the number of new rotifer species records from Cambodia by 64. Ponds, lakes
and reservoirs were found to contain a greater number of rotifer species than the river sites which
tended to be low. This difference is most likely a result of the high flow in the river providing
unsuitable habitat for these tiny organisms which may reduce both the number of species that canⒸ ISERD

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survive in this habitat and their density. In addition to flow the conductivity of the water body
appeared likely to be important in determining the number of rotifer species found in particular
habitats.
Table 2 New records for Cambodia, their incidence in the present study andoccurrence elsewhere
No1
2
3
4
5
67
8
9
1011
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31Species
Anuraeopsis navicula
Asplanchna tropica
Brachionus amazonicus
B. sessilis
Cephalodella forficula
C. hollowdayi
C. intuta
C. mucronata
C. songkhlaensis
C. tenuior
C. ventripes
C. xenica
Colurella colurusC. hindenburgi
C. obtusa
C. sulcata
Conochilus coenobasis
Dicranophorus corystis
Encentrum felis
Gastropus hyptopus
Itura aurita
Lapadella monodactyla
Lecane arcuata
L. aspasia
L. batillifer
L. braumi
L. calcaria
L. fl exilis
L. inermis
L. inopinata
L. nelson

Records elsewhere
AUS, NEA, NEO, ORI, PAL
AFR, ORI.
NEOCosmopolitan.
AUS, NEA, NEO, ORI, PAC, PALNEO.
Cosmopolitan.
AFR, AUS, NEA, NEO, ORI, PAL
ORI, Thailand.
ANT, AUS, NEA, ORI, PAL
Cosmopolitan; Thailand
NEA, PAL
Cosmopolitan
Cosmopolitan; Thailand
Cosmopolitan, Thailand, Lao PDR.
Cosmopolitan, Thailand, Lao PDR.
NEA, PAL
AUS, NEA, NEO, PAL; Laos
Cosmopolitan, Thailand.
Cosmopolitan; Thailand
Cosmopolitan; Thailand
NEA, NEO, ORI, PAL; Thailand
AUS, ORI; Thailand
AFR, AUS, ORI, Thailand.
NEA, ORI
Cosmopolitan; Thailand
Cosmopolitan, Thailand, Lao PDR.
Cosmopolitan; Thailand
AFR, NEO, ORI, Thailand.
AFR, AUS, NEO, ORI, Thailand, Lao
32 L. nitida
PDR.
33 L. pumila
AFR, AUS, ORI, PAL
34 L. pyriformis
Cosmopolitan, Thailand.
35 L. schraederi
ORI
36 L. simonneae
AFR, ORI
37 L. tenuiseta
Cosmopolitan; Thailand
38 Lepadella ehrenbergi
Cosmopolitan, Thailand.
39 L. punctata
ORI, PAL; Thailand
40 L. triptera
Cosmopolitan, Thailand.
41 Macrochaetus longipes
Cosmopolitan; Thailand
AFR, ANT, AUS, NEA, NEO, ORI,
42 Microcodon clavusPAL
43 Monommata actices
Cosmopolitan, Thailand.
44 M. caudataNEA, PAL
45 M. longiseta
Cosmopolitan*, Thailand, Lao PDR.
46 Notommata collaris
Cosmopolitan*.
*Although considered cosmopolitan, this species was not listed in ORI by Segers (2007).

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Table 3 New records for Cambodia, their incidence in the present study andoccurrence elsewhere (Cont.)
No47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64Species
N. endoxa
N. tripus
Polyarthra dolichopteraResticula melandocus
Scaridium bostjani
Squatinella lamellaris
S. leydigi
Synchaeta oblonga
Taphrocampa selenura
Testudinella truncata
Trichocerca bidens
T. collaris
T. heterodactyly
T. iernis
T. macera
T. scipio
T. tenuior
Trocosphaera aequatorialis

Records elsewhere
NEA
Cosmopolitan.
AFR, AUS, NEA, ORI, PAC, PAL
AFR, AUS, NEA, NEO, ORI, PAL
Cosmopolitan, Thailand, Lao PDR.
Cosmopolitan, Thailand, Lao PDR.
AUS, NEA, NEO, PAL.
Cosmopolitan
AFR, AUS, NEA, NEO, ORI, PAL
AFR, NEA, PAL
Cosmopolitan, Thailand, Lao PDR.
AFR, AUS, NEA, NEO, ORI, PAL
species inquirenda
Cosmopolitan; Laos
AFR, AUS, NEA, PAL
Cosmopolitan; Laos
Cosmopolitan, Thailand, Lao PDR.
AUS, NEA, NEO, ORI, PAL.

ACKNOWLEDGEMENTS
This work was supported by the Centre for Biodiversity Conservation (CBC), Faculty of Science,
Royal University of Phnom Penh and Fauna & Flora International, Cambodia.
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