back to 49 a.

 

QUADRATA GROUP
Insertion of posterior spines at the posterior corners.

 

50 a. Dorsal plate of lorica with 2 closed median
        fields and one open. Left lateral posterior
        spine always present. Size 150-300 μm.
        Very polymorphic. Feeds mainly on unicellular
        algae less than 10 μm. In large lakes with
        long spines (form frenzeli), or in ponds

        with thick lorica covered with spines.
        - Laguna de Bay (?), Calibato Lake.

           Keratella quadrata, (MULLER, 1786)

(syn. Anureae aculeata)

           [1941, 1974]

50 b. Dorsal plate of lorica with 3 closed median fields.

      Left lateral posterior spine more or less reduced...........51

 

51 a. Third median field hexagonal, closed by a
trans­verse ridge. Size 250 μm. Left lateral
posterior spine reduced (form typica),
strongly reduced (form assymmetrica)
or absent (form monstrosa).
Planktonic in tropical lakes, warm-stenotherm.
- Laguna de Bay, Paoay Lake, Bunot Lake, Calibato Lake,
  Tadlac Lake, Taal Lake, Lake Mainit, Lake Lanao,
  IRRI rice field, Lake Danao.

Keratella tropica (APSTEIN, 1907)
(syn. Keratella valga tropica).
           [1941 (valga + tropica), 1973, 1974 (valga),
           1980, 1984, 1999]

51 b. Third median field pentagonal, terminating in
a median ridge. Posterior spines divergent of
unequal length.
Shows affinity for the bluegreenalgae (cyanobacteria)
and dinoflagellates in Lake Lanao (Lewis 1979).
- Lake Lanao, Laguna Lake, IRRI rice field, Taal Lake.
    Keratella procurva (THORPE, 1891)
              [1977, 1978a,b, 1979b, 1986, 1999, 2001]

to 52 a.