IUCN threat status:

Data Deficient (DD)

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General characteristics of Danionella priapus:
  • Head and eye large, mouth supraterminal
  • Body laterally compressed, elongate
  • Dorsal fin short, situated opposite posterior half of long anal fin
  • Caudal fin furcate, with remnants of larval fin fold in front of its dorsal and ventral margins
  • Remnant of pre-anal larval fin fold present in females only
  • Anus and genital papilla of adult males located between pelvic fins, in females at normal position in front of anal fin
  • Genital opening of adult males located at tip of short, conical projection at proximal end of funnel-like structure formed by pelvic fins being fused along their midline
  • Pseudotypanum present in body musculature at lateral side of anterior gas-bladder chamber, rendering its pigmented surface visible
  • Body muscles greatly thinned out at lateral side of posterior gas bladder chamber
  • Scales absent
  • Lateral-line canals and pores on head and body absent

Vertebrae and ray characteristics:
  • Total vertebrae: 37 or 38
  • Abdominal vertebrae: 15 or 16
  • Caudal vertebrae: 22 or 23
  • Ribs present on vertebrae 5 to 14
  • Dorsal-fin rays: ii,6,i or ii,7,i
  • First dorsal-fin ray pterygiophore inserted behind neural spine of vertebra 21 or 22
  • Last dorsal-fin ray pterygiophore inserted in front of neural spine of vertebra 25 or 26
  • Anal-fin rays: ii,17,i or ii,18,i
  • Number of anal-fin pterygiophores in front of first hemal spine: 0, 1 or 2
  • Last anal-fin pterygiphore inserted in front of neural spine of vertebra 27 or 28
  • Principal caudal-fin rays: 9+9
  • Dorsal procurrent rays: 7 or 8
  • Ventral procurrent rays: 6, 7 or 8
  • Pectoral-fin rays: 8
  • Pelvic-fin rays: 5

Pigmentation-related characteristics:
Pigmentation in alcohol specimens restricted to several rows of melanophores:
  • mid-lateral row along horizontal septum from shoulder girdle to hypural plate
  • ventral row from in front of and slightly above anal-fin base along ventral larval fin fold to end of hypural plate
  • row along anal-fin base
  • mid-dorsal row starting behind head with several enlarged melanophores forming small blotch and extending usually halfway between head and anterior base of dorsal fin, rarely to anterior dorsal-fin base
  • paired dorsal paramedian rows from head to base of caudal fin
  • dorsal-fin base row
  • abdominal mid-ventral row from ventral tip of cleithrum to anus
  • several melanophores on otic capsule
  • melanophores capping dorsal and dorso-lateral face of gasbladder chambers and their connecting duct and lining peritoneum covering gonads
  • streaks of melanophores lining anterior edge of lower cleithrum, ventral edge of opercle and preopercle, branchiostegal rays and fin rays in dorsal, anal and caudal fins and anterior 2 or 3 rays of pectoral fin
  • several larger melanophores near symphysis of lower jaw
Head with:
  • supraoccipital blotch formed by several large contiguous melanophores
  • numerous large scattered melanophores between supraoccipital blotch and epiphyseal bar
  • a preepiphyseal blotch
  • a few prenasal melanophores
In life, body colourless and largely translucent, except for:
  • melanophore patterns described above
  • a thin yellowish-greenish line running along body at level of neural tube
  • golden chromatophores forming ring around pupil, capping swimbladder chambers and connecting duct


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