(a species of owlet moth (Noctuid)) Some caterpillars, after they emerge from their egg, can increase their weight by 25,000 times.

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Diagnostic description

Live individuals of Danionella priapus may be easily confused with the other species of the genus due to their miniature size and lack of easily visible external characters. However, the diagnostic characters listed below guarantee a problem-free identification upon closer inspection with a magnifying glass or microscope.

D. priapus is distinguished from its congeners, D. dracula, D. translucida and D. mirifica, by:

  • the presence in adult males of a conical projection of the genital papilla situated between the pelvic fins, which form a funnel-like structure (vs. genital papilla not developed as a conical projection and pelvic fins not funnel-shaped)
  • possessing 8 pectoral-fin rays (vs. 6-7) and 20-21 anal-fin rays (vs. 12-14 in D. dracula, 12-16 in D. translucida, and 17-19, rarely 20, in D. mirifica)
  • having the last anal-fin pterygiophore inserted in front of haemal spine of vertebra 27 or 28 (vs. 21 or 22 in D. translucida, 23-25 in D. mirifica, and 22-24 in D. dracula)

It differs further from D. translucida and D. mirifica in:

  • the presence of a median and 2 paramedian rows of pigment cells on the dorsal side of the body (vs. pigment rows absent). 

It is further distinguished from D. dracula and D. mirifica by having:

  • 7-8 dorsal caudal procurrent rays (vs. 5-6)
  • 6-8 ventral procurrent rays (vs. 4-5)

In addition, it differs from D. dracula in having:

  • 2 upper jaw bones (vs. 1)
  • edges of jaw bones entire, without processes (vs. dorsal face of dentary and ventral face of upper jaw in males each with a single row of 6-13 odontoid processes, anterior most large and canine-like)
  • 9+9 principal caudal fin rays (vs. 7-8 + 7-8)

and by:

  • the presence of maxillary-mandibular cartilage (vs. absence)
  • the absence of membrane bone flanges on basipterygium (vs. presence)

It differs also from D. translucida in having:

  • 15-16 abdominal (vs. 13-14) vertebrae
  • 22-23 caudal (vs. 19–20) vertebrae
  • a well-developed lateral stripe extending from ear capsule to caudal peduncle (vs. a row of few melanophores midlaterally, restricted to posterior part of body)
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