Biology of Finfish and Shellfish

Thunidae

• In small larvae, black pigment cells on the lower jaw tip were first observed in larvae of about 4.5 to 6.0 mm SL, and often as small as 3.8 mm SL; those on the upper jaw tip were first observed in larvae about 7.0 mm SL.
• All larvae between 4.5 and 7.0 mm SL have black pigment cells only on the lower jaw tip, and larvae between 7.0 and 9.0 mm SL having black pigment cells on the tips of both jaws.
• The pigment cells were located on the inner, and sometimes outer, margins of lower jaw tip in larvae up to 10.8 mm SL.
• The black pigment cells on the inner margin of the jaw migrate to the outer margin with further growth of the larvae.
• The distinctive patterns were located along the dorsal margin of the trunk from about the midpoint of the second dorsal fin base to the caudal peduncle.
  There was usually none or one red pigment cell at the caudal peduncle.
• These pigment cells were well spaced, extending forward to the middle of the second dorsal fin base.
• In larger larvae (10-13 mm SL) the two successive single pterygiophores between two adjoining neural spines occurred at the posterior end.