Table 1 Developmental stages of the cuttlefish. Main developmental events at each stage are based on [29]

24–25

Head with eye vesicles protrude laterally. Fins are evident on the mantle. Mantle is beginning to grow downward. Shell is discernible with some difficulty. Fourth arm (tentacle) elongates prominently.

26–27

Eye vesicles are nearly spherical. Lens primordia may be seen with care. Tentacle curves upward to backward. Funnel folds begin to form the siphon. Sucker primordia are present on the arms.

28–29

Pigmentation has begun in the retina (very pale yellow to light orange). Lens primordium is prominent as a refractive rod. Iris fold is forming pupil. Median margins of the funnel folds are fusing. Tentacle is coiled once. Heart beat may be discernible with some difficulty. Organ of Hoyle (T-shaped thickening on the dorsal surface of the mantle) is visible faintly. Heart beat is evident.

30–32

Retina is orange to reddish brown. Pigmentation of iris has occurred. Reflective dots appear in the shell. Tentacle coiled twice. Chromatophores present in the mantle. Organ of Hoyle evident.

33–36

Retina is brownish red to reddish black. Eye ball gradually becomes iridescent and opaque. Two to four striations appear on the dorsal surface of the shell. Pigmentation of ink sac occurs. Secondary cornea covers the eye. Tentacle is uncoiled and peduncle of tentacle is retracted into the tentacular sac by degrees.

37–38

Eye is black and strongly iridescent. Lid occurs at the margin of the pupil and covers the pupil. Five to six striations are on the shell. Iridescent layer is evident on the ink sac. Whole tentacle is retracted into the tentacular sac. Slight pigmentation is discernible in the jaws. Iridescence is evident on the surface of the mantle.

39

Seven striations are on the shell. Yolk sac prominently decreases in size.