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89 a. Head relatively small, its dorsal part not protruding,
with even top, forming less than one-fourth of total
length. Compound eye in frontal, vaulted part, close
to top. With well developed dorsal pert. 2^nd antennae
short, reaching to 2/3-3/4 of shell (carapace) length.
Postero-ventral margin of shell (carapace) with 8-32
(often 10-18 in ssp. orghidani and 22-29 in
ssp. transamurensis) mostly large and widely spaced
spines and thin setules between them. Small ventral
inflection of the shell, which is shifted much anteried,
carrying up to 8 long, feathered setae. With short acute
spine on the outer side on the end of upper antennal
branch (Korovchinsky, 1991). Size 660-1200 μm, head/body
length 0,38-0,43, 2^nd antenna/body length 0,68-0,84
(Weiler, 1997, ssp. orghidani) (Figures 89a¹, 89a²).
Polymorphic species. Production of Diaphanosoma "modigliani"
(D. o. transamurensis) in Lake Lanao is associated with
small to medium size algae (e.g. Cryptomonads) of round
or oblong shape (Lewis 1979). Predated by fish and
Chaoborus.
  Diaphanosoma orghidani, NEGREA, 1982.

Key to subspecies:

Postero-ventral edge of shell (carapace/valve) with not
more than 18-20 denticles.
- Not recorded from the Philippines.
  Distributed in Western Eurasia
   Diaphanosoma orghidani orghidani, NEGREA, 1982.

Postero-ventral edge of shell (carapace/valve) with more
than 20 denticles. Showed a high degree of ephemeral
patchiness in Lake Lanao (Lewis, 1978d). It co—occurs
with D. sarsi (Lake Lanao) and D. excisum (Laguna de Bay).
– Lake Lanao, Mindanao,
- Illaguen River, Ixabila, North-Eastern Luzon
- Laguna de Bay (female).
   Diaphanosoma orghidani transamurensis, KOROVCHINSKY, 1986
             [1969, 1979b, 1980, 1984a, (D. modigliani)
               1991, 1992, 1998a, 2000a+b, b (D. orghidani)]

Note 1: Diaphanosoma species belonging to the D. brachyurum – group
has been found e.g. in Sumatra. The dorsal part of the head
is - like D. orghidani - relatively weakly developed, not or
only weakly protruding. However the spines (denticles) of
postero-ventral shell (valve) margin differ strongly in form
and size; small intermediate spines are situated between large
ones. The name "D. brachyurum" has been incorrectly used
designation of other species of the genus e.g. D. orghidani,
which probably is case with the following record for the
Philippines. Found Indonesia, Africa and America with similar
forms to Diaphanosoma brachyurum s. str. (LIEVEIN, 1848))
which is found in Europe and Asia. The systematic status of
those forms is still unclear. (Negrea, 1982, Korovchinsky, 1992)
- Laguna de Bay (?).
   Diaphanosoma brachyurum – group
   (syn. Diaphanosoma perarmatum (BREHM, 1933))
           [1954 non D. brachyurum (?)]

89 b. Head large, but forming less than one half of the shell (carapace)
- one third of the body size, with dorsal part strongly protruding.
Marginal spines large, not very numerous (22-58), apical spine on
the outer side on the end of upper antennal branch strongly curved.
Dorsal side of postabdomen strongly convex, prominent. Ventral
valve inflexion Comparatively long and not shifted proximal.
Lives in large and small reservoirs, mostly in limnetic but also
in littoral zone, in ponds, fishponds, mining pools and stream
backwaters. Rare.
Figures 89b¹, 89b²
-  Paoay Lake, Talasay Batangas, Taal Lake, Laguna de Bay.
   Diaphanosoma tropicum, KOROVCHINSKY, 1998

                   [1991, 1998a (type species), 2000a, 2002a, 

                    2011b+c, 2012b, 2014]

Note 2: Head large, with dorsal part strongly protruding. Marginal spines
small, very numerous (55-86), apical spine on the outer side of the
end of upper antennal branch slightly curved or straight. Dorsal side
of postabdomen flatly convex, not prominent. Ventral valve inflexion
comparatively short and shifted proximal. D. modigliani inhabits Lake
Tempe and Lake Toba in (Sumatra, Indonesia). Rare.
Probably synonymous with D. tropicum or D. orghidani
(Lake Lanao, Korovchinsky, 2000a) and maybe D. dubium,
in the Philippines, since D. modigliani is only found
in Indonesia. (Korovchinsky, 1991+1998).
- non-Laguna de Bay (?), non-Lake Lanao (syn.?).
   Diaphanosoma modigliani, RICHARD, 1894.
          [1939c, 1941a, 1978a+b+d (non D. modigliana), 1979b
           1980, 1984a (D. orghidani), 1986a]

89 c. Head very large, robust, cone shaped, with dorsal part protruding,
length almost one half of shell (carapace). Without ventral fold
on shell with only narrow inflection merging gradually with
postero-ventral margin. Row of small spines along postero-ventral
margin of shell are not numerous, mostly 12-29 (8-40).
Representatives from tropical regions rather small: Body size:
760-940 μm, comparatively small head, large eye in specimens
from Philippines and Thailand (Korovchinsky, 2000b). Planktonic
in lakes, reservoirs, fishponds and rivers (Philippines).
- Sampaloc Lake, Laguna de Bay, Lake Baao, Illaguen River, Ixabila,
North-Eastern Luzon.
Figures 89c¹, 89c²
   Diaphanosoma dubia, MANUILOVA, 1964
   (syn. Diaphanosoma dubium, MANUILOVA, 1964)
                      [1998a, 2000b, 2014]

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