Related species
Diagnostic description of Pangio longimanus
P. longimanus differs from other species of Pangio by its:
- extremely elongated pectoral fins in males - they reach more than head length and 16% standard length (vs. under 12% SL)
- miniature size (less than 23mm SL)
Its long, pointed narial flap (nasal barbel) further distinguishes it from all Pangio species except:
- P. bitaimac
- P. cuneovirgata
- P. doriae
- P. filinaris
- P. fusca
- P. lidi
However it differs from these species in other characteristics. It can be distinguished from:
- P. bitaimac and P. doriae by:
- fewer total vertebrae (46-47)
- P. fusca and P. lidi by:
- fewer total vertebrae (46-47)
- the presence of the pelvic girdle and fins (vs. absence)
- P. cuneovirgata by:
- fewer total vertebrae (46-47)
- the absence of the series of saddle-like blotches (vs. presence)
- P. filinaris by:
- a more slender body (depth 9.6-12.6 vs. 8-9.6 times in SL)
- its mottled colour pattern
The smallest Pangio species
Pangio longimanus is the smallest Pangio species described so far. The fully formed and sexually dimorphically modified pectoral fins of the male demonstrate that it has reached adulthood at 20mm SL.
P. filinaris and P. incognito are also small, but reach adult sizes of over 30mm.
P. longimanus is therefore the only member of its genus to qualify for inclusion among miniature fish species, as defined by Weitzman and Vari (1988). It is the 2nd miniature cobitid after Kottelatlimia katik.
Unique pectoral fins
Although the expanded second pectoral-fin rays are characteristic for male Pangio (Burridge, 1992), the extremely elongated pectoral fins of male P. longimanus (reaching more than 16% of its standard length) are still unique in the genus.
The longest pectoral fins relative to standard length among the other Pangio species seem to be developed in P. atactos, with up to 11.2% SL (Tan and Kottelat, 2009), and P. piperata, with up to 11.5% SL (Kottelat and Lim, 2009).
The unusual elongation of the pectoral fin of P. longimanus appears to be linked to the miniaturisation of its body.