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2 a. Body with radial symmetry: 


HYDROZOA (class) 

Craspedacusta, Freshwater medusae
        With small solitary polyps and free-swimming medusae.
In freshwater. Size 20000 μm (20 mm). 
        Food of polyp and medusae: Asplanchna, copepods.
        Although no recent records are known, it might still 
        be found (Terry L. Peard, Ph.D. personal communication).
Se lifecycle from (

       Craspedacusta sowerbyi, (LANKESTER) 

       (syn. C. sowerbii) 

         [Roxas 1936, in Reisinger, 1972] 


2 b. Body with bilateral symmetry.......................................3   

3 a. Small animals with ciliated crown or corona (wheel organ).
        Body without segments. No legs present, 
        with or without tail like foot. Suspension feeding via coronal cilia
        Food: Bacteria, algae, detritus. Planktonic or bentic: 

ROTIFERA, Rotifers or Wheel animacules (phylum)..................7  


3 b. Body segmented (with metamery): 

ARTHROPODA, Arthropods (phylum)..................................4


4 a. Without jointed legs, (larvae) transparent, except for the black
        air-sacs, of which one pair lies in thorax and one pair lies
        near the end of abdomen.
As fig. 4a. 

   (INSECTA, Insects (Class)

            DIPTERA, True flies (order)    


     Chaoborus (syn. Corethra), Phantom midge-larvae.
            Third and fourth larval instars

            during night, bentic during day. With vertical 
            Food: zooplankton and midge-larvae (Chironomids). 
            In Lake Lanao Chaoborus is responsible for the major
            mortality of its pry (Thermocyclops, Tropodiaptomus, 
            Diaphanosoma, Moina, Bosmina and Keratella). In lakes.
            - Lake Lanao (C.sp = Ekstein 1)
               Chaoborus manilensis, (SHINER)
                  [1969, Lewis 1977, 1979b]    


4 b. With legs. 

          CRUSTACEA, Crustaceans (class)................................5   


5 a. Without a shell-like covering of the body, with up to five pairs
          of 2-branched swimming legs (might have a 6th rudimentary 
          pair of leg). Abdomen without appendages. 
          Size 100-2000
μm. Filtratory and/or raptorial.
          Food: Algae, detritus and zooplankton.
          COPEPODA, Copepods (subclass)...............................100 



5 b. With a shell-like covering, which may or 
          may not entirely cover the 


6 a. Bivalve shell enclosing the entire body. Body not distinctly
            segmented. Legs not leaf-like. Size 100-1000
μm. Planktonic
            species, omnivorous, feeding on algae and detritus. (Fig. 6a:
            anatomy of ostracod and sample from Laguna de Bay). 

OSTRACODA, Mussel shrimps (class)
Only few records. Victor (2002) gives a key to 17 genera likely to occur in Western tropical freshwaters.
Following has now intention to be complete overview of the Philippine mussel shrimps:

            CYPRIDIDAE, BAIRD 1845 (family)
            STRANDESIA, VAVRA, 1895.


  - Lake Lanao, rice fields.
  Strandesia wolterecki, TRESSLER 1937.
  (syn. Strandesia chondropherusa Rome, 1965)
(syn. Strandesia regularis Rome, 1962)
         [1937d, 1981a,b, 2005b(key)]

  - Ponds in Bocolod Chico, Mindanao.  
Strandesia wierzejskii (Grochmalicki, 1915)

  Other species of Strandesia found in the Philippines:

  Strandesia. calapanensis Tressler, 1937

  Strandesia. complexa Victor and Fernando, 1982

  Strandesia. sexpunctata Klie, 1932

  Strandesia. purpurascens (Brady, 1886),
  (see 1981a, 2005b(key))


Endemic species in
  - Laguna de Bay

Stenocypris derupta

         [1981e, 2002a]


  Adapted for benthic life, but frequently appearing in
  plankton collections
      - Mindanao
  Cypria (Cypris) spinifera, TRESSLER, 1937
         [1981a, 2002]

EUCYPRIS Planktonic genus.
  Endemic species.
  - Laguna de Bay [type locality]. 

  Eucypris bayensis, TRESSLER, 1937
          [1941, 1981a,b]
- R
oadside ditch on Camaguin Island, 1932.
Eucypris orca, TRESSLER, 1937
          [1941, 1981a,b]


Dominating the invertebrate fauna together with Eucyclops serrulatus in IRRI (International Rice Research Institute, Los Baños, Luzon. In wetland rice fields it has a limiting effect of grazing on Inoculation of non-indigenous Blue Green Algae strains was establishment, but other factors were involved.     
- Ricefield floodwater, IRRI.
Heterocypris lozonensis Neale,  
          [1981d, 1998b]

Ostracod  from Laguna de Bay


6 b. Bivalved shell (Carapace) covers the body but leaves the head free. 
         Legs leaf-like. Size 200-1500
μm. Filtrators, with filter setae
         on the legs. Food: Algae, bacteria and detritus.
          BRANCHIOPODA, Branchiopods (subclass). 
             CLADOCERA, Water fleas (order)
             (Tagalog: Kutung tubig)...............................78




Table: Characteristics of the main groups of freshwater zooplankton. Excerpt after Brandl (2002)






Reproduction mode 

Parthenogenetic (mostly)



Typical adult length μm

200 - 600

200 - 1500

100 - 2000

Food size μm

1 -20

1 - 50

5 - 100

Mode of feeding


Suspension feeding via coronal cilia

Filtratory feeding via thoracic appendages

Filtratory and/or raptorial

Susceptibility to fish predators

Very low



Susceptibility to invertebrate predators 



Moderate to high


6 c. Other groups of animal that can be found as cosmopolitans in tropical freshwater zooplankton samples are only mentioned briefly, See Fernando (2002a) for further details. The most important are:


 Bryozoans or Ectoprocts: (e.g. Plumatella philippinensis KRAEPELIN, 1887, Freshwater Philippines, as floato-blasts). (visited May 2007)

Gastrotricha, Freshwater aschelminths: (e.g. Chaetonotus, in shallow ponds).


Neorhapdocoela: Turbellaria flatworms or Platyhelminthes: (e.g. Mesostomum).


Hydrocarina, Water mites, (Arthropoda): (e.g. Limnesia).


Mollusca: Bivalve Molluscs: gill lice (mussel glochidia – larvae able to attach to skin or gills of fish) (Cristaria plicata (LEACH, 1814). Very rare, in zooplankton samples in post-parasitic stage. Invasive in the Philippines. - Luzon, fishponds. Cagauan (2006)).

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