Effect of light intensity on embryonic development of the cuttlefish Sepia lycidas

The effects of light intensity on embryonic development of fertilized eggs of Sepia lycidas were investigated to determine the best light conditions for the embryos’ development. A single-factor experiment was performed to examine the effects of different light intensities (dark or 4.3, 10.2, 29.6, or 50.7 μmol/(m2·s)) on the embryonic development. The hatching rate, incubation period, hatching period and weight, and survival of hatchling cuttlefish were significantly affected by the light intensities (P < 0.05). When light intensity exceeds 10.2 μmol/(m2·s), the weight of hatchling cuttlefish and incubation period gradually decreased with the increase of light intensity, while the hatching rate first increased and later decreased. The sensitivity to light clearly varies among stages of embryonic development; the impact of light intensity on embryonic development appeared from the red-bead stage to hatching. High light intensities can interfere with the development of embryos and lead to abnormal development and premature hatching, reduced hatchability, decreased vitality of cuttlefish hatchlings, and asynchronous hatching, especially at light intensities exceeding 10.2 μmol/(m2·s). Low light intensities are better for embryonic development of S. lycidas than high light, and the light intensity as 10.2 μmol/(m2·s) was thus recommended. During incubation of paralarvae, fertilized eggs should be kept out of direct sunlight, and shading measures should be taken to keep the eggs in low light intensities.