4. An Illustrated Key 
to the Philippine 
Freshwater Zooplankton.

Click the numbers to see the figures.

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  1 a. Unicellular animal:

PROTOZOA, Protozoan (phylum);
Occur often in zooplankton, but are usually unrecorded, except from species with shells and other robust outer cover, which remain recognizable in preserved material. In Lake Mainit  protozoans comprised 15-50 % of the total zooplankton biomass (
Lewis, 1973). In Lake Lanao Lewis (1985) recorded an average of 1900 individuals of protozoan per cm3, corresponding to a volume of 260,000 μ3/cm3. Very small flagellates, dominating the larger flagellates, ciliates and amoeboid forms, accounted for over 75% of individuals and of biomass. The protozoans mainly feed on bacteria in Lake Lanao, and thus constitute a link between the bacteria and the macro zooplankton. Their role in phytoplankton mortality was only small and the total consumption of phytoplankton by all protozoans did probably not exceed 15 % of the daily standing stock. 


 SARCOMASTIGOTA (subkingdom)

 SARCOMASTIGOTA (subkingdom)

AMOEBOZOA (phylum)

RHIZOPODA (class);


TESTACEA, testacean rhizopods (subclass).
Characterized by having a shell:

ARCELLIDAE (e.g. Arcella), CENTROPYXIDAE (e.g. Centropix), DIFFLUGIIDAE (e.g. Difflugia)
(families). (Fig. 1a is test shells as seen in the counting chamber - FP80)


Arcella, dorsal view. From Laguna de Bay

Difflugia from Laguna de Bay

Centropix, dorsal view. From Laguna de Bay


See Smirnov, A.V. (1999 and
http://amoeba.ifmo.ru/guide.htm (Visited April 2007)) for morphotyping naked amoebae. Can be found up to 100.000 individuals/L, in freshwater and seawater. Some species are infectious on fish (e.g. gills.). Lewis (1985) found direct evidence on predation on diatoms by amoeboid protozoans in Lake Lanao.


Amoeboid protozoans feeding on diatoms
Lewis (1985)


    BICILIATA (subkingdom)

HELIOZOA, Sun animalcules. (Phylum)
Roughly spherical amoeboid with many stiff, microtubule-supported projections called axopods radiating outward from the cell surface.
(Cited after Wikipedia). Actinophrys sol EHRENBERG is a common species among water plants and in zooplankton in South-East Asia.


                      ALVEOLATA (subkingdom)

CILIATA, CILIOPHORA, Ciliates (phylum):
Size 20-500 μm.
 PENICULIDA (order).
          e.g. Paramecium O.F. Müller, 1773.
 SESSILIDA (order)
          e.g. Vorticella, "Bell-animal". Often
          attached to freshwater crustacean.
Tintinnida etc.
   From less than 1 to 300 individuals/mL in
   plankton. Food: mainly bacteria.
   Ciliates tend to be benthic or epiphytic,
   although some can be found in large numbers
   in the plankton. (Richter, H. 2001)
   - Laguna de Bay

Tintinnidae from Laguna de Bay


                       EXCAVATA (subkingdom), True flagellates, 
            Loukozoa  (phylum), Percolozoa  (phylum), Euglenozoa (phylum)
          Other hetero- and mixotroph nanoflagellate orders
Hansen et al., 1992):
                             Choanoflagellida, “collar-animals” (order),
                                       e.g. Acanthoecidae
                             Bicoecida (order),
                             Kinetoplastida (order),
                   “Phytomastigophora” – forms without chloroplast:
                             Euglenida (order),
                                       e.g. Euglenophyceae
                                       e.g. Chrysophyceae
                             Cryptomonadida (order),
                                       e.g. Chryptophyceae
                             Prymnesiida (order).
Lewis divided flagellates into small (< 10 μm)
             and large flagellates (>/= 10 μm).
Lewis, 1973, 1985]


 1 b. Multicellular animals, METAZOA, Metazoans.........................2


To 2a