Sepia lycidas

Dorsal surface of Sepia lycidas cuttlebone

Studies have shown a morphological asymmetry present in the cuttlebone curvature within the kisslip cuttlefish.[8] The cuttlebone may be more convex, or more developed, on one side than it is the other, which causes the cuttlefish to exhibit preferences towards its right or left side when hunting prey.[8] For example, the cuttlefish will typically turn towards its right side when hunting, if the cuttlebone is more convex on the right side than the left.[8]

Specimen of Sepia lycidas in the National Museum of Natural Science in Taiwan

Cephalopods in general are usually gonochoristic, meaning that an individual organism has only one of at least two distinct sexes.[11] This species in particular has been used in many studies on various aspects of reproductive behaviors in cephalopods because they are easily bred and cultivated in captivity.[11] When mating, males will perform displays to attract females to mate with.[5] Then, during copulation, males will grasp the female and insert the hectocotylus into the female's mantle cavity. Within the mantle cavity is where fertilization typically occurs.[5] Sepia lycidas lay amber colored eggs shortly after fertilization takes place, that are similar in shape to hen eggs.[4] Finally, this cuttlefish species has been observed displaying many complex reproductive behaviors, such as courtship, mating, males competing for mates, spawning during the breeding period, and male escorts.[7]

Sepia lycidas has a life cycle that is similar to other cuttlefish species, beginning with embryos hatching into a planktonic stage after about 25 days of incubation.[6] Hatching times are vulnerable to changes in environmental conditions and can vary depending on light, temperature, and salinity.[2] They continue to grow and develop through this planktonic stage until they are fully grown, benthic adults; however, juveniles will still show similar behaviors to benthic adults like burying themselves in the sand soon after hatching.[4][5] Males reach sexual maturity at approximately 150 days after hatching, while females take longer to fully mature.[11] Both males and females will usually die shortly after their spawning and brooding behaviors have ceased.[5]

Gonadal sex differentiation is when an undifferentiated gonad transforms into either an ovary or a testes, typically occurring during embryonic development. This process was studied on a histological level within Sepia lycidas and the results are applicable to similar cephalopod species, as well.[11] The observations showing an undifferentiated gonad forming within cuttlefish embryos anywhere from 14–21 days after fertilization.[11] A few days later, around 28 days into embryonic development (before hatching), is when sexual dimorphism begins and ovarian differentiation occurs. It isn't until about 20 days after hatching that organisms will experience testicular differentiation.[11] In another study, the Gonadotropin-releasing hormone-like peptide (GnRH-like) levels of kisslip cuttlefish were observed, since this peptide has been proven to play a significant role in some cephalopod reproductive behaviors.[13] The results of this study showed that GnRH-like was present within the organism's brains even in an undifferentiated state, and that the levels did increase significantly once gonadal sex differentiation began to take place.[13]

The kisslip cuttlefish feeds primarily on fish and crustaceans, especially shrimp, which they engulf by "jumping" on their selected prey.[8] Additionally, studies have found that they exhibit a turning behavior when hunting, and will turn their bodies either clockwise or counterclockwise before engulfing their prey, which is an example of behavioral dimorphism within the species.[8] The direction that the cuttlefish shows preference towards when turning and hunting is dependent on which side of their cuttlebone is further developed - a more developed right side leads to a clockwise preference and vice versa.[8]