| Very slender body; gut elongate, thin and nearly straight; head flattened; narrow, elliptical eyes on short stalks; conical ventral choroid tissue; isthmus pigment typical of genus; lower jaw melanophore present (absent in H. reinhardtii larvae in California Current region); fewer (up to 3) postanal myosepta dashes compared with H. reinhardtii (up to 10); Br1, PO1, PO5, VO4 photophores the first to appear at transformation; lower total vertebral count (35-37) and fewer anal fin rays (18-21) compared with H. reinhardtii (38-40 and 21-25).
Pigmentation:
Preflexion: by 3.0 mm, ventrolateral pair just posterior to cleithrum, dorsolateral pair on terminus of gut, 2 lateral gut pairs, 2 in tandem on isthmus, 2 widely-spaced on postanal ventral margin, and 1 at dorsal margin; by 5.0 mm, 1 at lower jaw tip; 1 at hypural anlagen; some on ventral finfold; by end of stage, posterior dash on isthmus divided into pair, 1-3 more on lateral gut, and a postanal pair extending upward in myosepta on each side from ventral margin.
Flexion: 1 or 2 more median dashes on isthmus; 1 on opercle; up to 8 laterally on gut; beginning of series on anal fin base.
Postflexion: up to 3 postanal myoseptum dashes; up to 8 laterally on gut; up to 15 on anal fin base.
Sequence of fin development: caudal, pectorals, anal, dorsal, pelvics. |