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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), 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.
-  Talasay Batangas, Taal Lake.
   Diaphanosoma tropicum, KOROVCHINSKY, 1998

                   [1991, 1998a (type species), 2000a, 2002a, 2011b+c]

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.
          [1938c, 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).
- Illaguen River, Ixabila, North-Eastern Luzon
   Diaphanosoma dubia, MANUILOVA, 1964
   (syn. Diaphanosoma dubium, MANUILOVA, 1964)
                      [1998a, 2000b]

   To 90a