Taxonomy

General characteristics of Danionella dracula:

  • Body elongate
  • Body depth contained 6-7.5 times in standard length
  • Abdominal region almost circular in cross section, body behind anal fin laterally compressed
  • Caudal peduncle long, narrow, 1.7-2 times in body depth and laterally compressed
  • Head and eye large, mouth supraterminal
  • Upper and lower jaws massive in large males, resulting in longer preorbital distance 
  • Nostrils well developed
  • Lateral line canals and pores on head and body absent
  • Dorsal fin short-based, situated opposite posterior half of long-based 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 males located distinctly anterior to anal fin between pelvic fins, in females at typical position in front of anal fin
  • Window (pseudotypanum) present in body musculature rendering pigmented surface of lateral side of anterior gas bladder chamber visible
  • Body muscles greatly thinned out at lateral side of posterior gas bladder chamber
  • Scales absent

Pigmentation-related characteristics:

Pigmentation in alcohol specimens is restricted to:

  • 5 rows of melanophores
    • a broad, mid-dorsal row from head to caudal-fin base
    • a mid-lateral row along horizontal septum from shoulder girdle to hypural plate
    • a ventral row from in front of and slightly above anal-fin base along ventral larval-fin-fold to the end of hypural plate
    • a row along anal-fin base
    • an abdominal, mid-ventral row from ventral tip of cleithrum to anus
  • melanophores capping dorsal and dorsolateral surface of gas bladder chambers and their connecting duct

In life, body is colourless and largely translucent, except for:

  • melanophore patterns described above
  • a thin yellow line running along body at level of neural tube
  • Stains of male and female Danionella dracula specimens
    Lookalikes

    Live individuals of D. dracula may be easily confused with the other species of the genus due to their miniature size and lack of easily visible external characters. Find out the diagnostic characters that enable an accurate identification to be made.

  • Scanning electron micrograph image of a male Danionella dracula specimen
    Evolution

    Danionella dracula is one of the most developmentally truncated vertebrates. Learn about the potential cause of this developmental truncation and about the species' unique hyperossifications that resemble teeth.