Trigonostigma truncata Tan, 2020

Family:  Danionidae (Danios), subfamily: Rasborinae
Max. size:  2.51 cm SL (male/unsexed)
Environment:  benthopelagic; freshwater
Distribution:  Asia: from the east coast of the Malay Peninsula, from south of the Isthmus of Kra in Narathiwat province of southern Thailand to the Malaysian State of Terengganu.
Diagnosis:  Dorsal spines (total): 1-1; Dorsal soft rays (total): 7-7; Anal spines: 1-1; Anal soft rays: 6-6. This species differs from T. heteromorpha in the following characters: a gently sloping lateral head profile to pre-dorsal region (vs. steep convex); sub-superior mouth (vs. terminal); caudal apex of axine not reaching caudal-fin base (vs. reaching and extending to hypural plate); dorsal and ventral apices of axine originate posterior to both dorsal-fin and pelvic-fin origins by up to three scale-widths (vs. dorsal apex starting one scale-width posterior to dorsal-fin origin and ventral apex starting at pelvic-fin origin); faint or indistinct brown humeral streak just posterior to opercular opening (vs. a distinct black humeral streak); base of dorsal fin hyaline and its middle reddish-orange in life (vs. anterior two-thirds orange-red); a distinct orange-red colour on anal fin in life (vs. faint or absence); body in life with a bluish-lilac sheen (vs. reddish or purplish sheen); a shallower body (depth at dorsal-fin origin 28.3-34.6% SL [mean 32.4], vs. 32.6-38.2% [mean 35.8]) (Ref. 122370).
Biology:  This species occurs in lowland freshwater acid swamp-forest stream habitats, usually flowing into riverine habitats. Associated species include the following: Notopterus notopterus (Notopteridae); Barbodes cf. binotatus, Desmopuntius hexazona, Osteochilus vittatus, O. waandersii (Cyprinidae); Boraras maculatus, B. urophthalmoides, Rasbora bankanensis, R. cephalotaenia, R. usonensis, R. einthovenii, R. paucisqualis, Trigonopoma gracile, T. pauciperforatum (Danionidae); Acanthopsoides sp., Lepidocephalichthys furcatus, Pangio cuneovirgata, P. piperata, P. semicincta, P. muraeniformis (Cobitidae); Homalopteroides nebulosus (Balitoridae); Nemacheilus selangoricus (Nemacheilidae); Barbucca diabolica (Barbuccidae); Hemibagrus capitulum, Nanobagrus fuscus, Pseudomystus stenomus (Bagridae); Kryptopterus minor, Silurichthys hasseltii (Siluridae); Parakysis verrucosus (Akysidae); Clarias leiacanthus, C. meladerma (Clariidae); Monopterus javanensis (Synbranchidae); Neostethus smithi (Phallostethidae); Bihunichthys sp., Chaudhuria sp. (Chaudhuriidae); Oryzias minutulatus (Adrianichthyidae); Indostomus crocodilus (Indostomidae); Hemirhamphodon pogonognathus (Zenarchopteridae); Xenentodon canciloides (Belonidae); Doryichthys martensii (Syngnathidae); Brachygobius xanthomelas (Gobiidae); Pristolepis grooti (Pristolepididae); Nandus nebulosus (Nandidae); Betta imbellis, B. pi, stigmosa, Luciocephalus pulcher, Parosphomenus paludicola, Trichopodus trichopterus, Trichopsis vittata (Osphronemidae); Channa limbata, and C. lucius (Channidae) (Ref. 122370).
IUCN Red List Status: Not Evaluated (N.E.) Ref. (130435)
Threat to humans:  harmless


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