The dwarf cuttlefish, Sepia bandensis, a small cephalopod that exhibits dynamic camouflage, is an emerging model organism in neuroscience. Coleoid cephalopods (cuttlefish, octopus, and squid) evolved large, complex brains capable of learning, problem-solving, and memory. We used high resolution magnetic resonance imaging (MRI), deep learning, and fluorescent histology to generate a dwarf cuttlefish brain atlas and built an interactive web tool (cuttlebase.org) to host the data. Guided by observations in other cephalopods, we identified 38 brain lobes. The dwarf cuttlefish brain is partially encased in cartilage and includes two large optic lobes (74% the total volume of the brain), chromatophore lobes whose motor neurons directly innervate the skin, and a vertical lobe that has been implicated in learning and memory. Motor neurons emerging from the chromatophore lobe modulate the color, pattern, and texture of the skin to elicit camouflage. This brain atlas provides a valuable tool for exploring the neural basis of cuttlefish behavior.

A modified Dimensional Change Card Sort (DCCS) task was used to test cognitive flexibility in adult cotton-top tamarins and children aged 19 months to 60 months. Subjects had to infer a rule from the experience of selecting between two cards to earn a reward, and the pairs of stimuli defined the rule (e.g., pick blue ones, not red ones, or pick trucks, not boats). Two different tests measured subjects’ ability to shift to a reversal of the rule (intradimensional shift) and to shift to a new rule defined by a dimension previously irrelevant (interdimensional shift). Both adult tamarins and children aged 49–60 months were able to learn the initial rule and switch to a reversal and to a rule based on a different dimension. In contrast, the two younger groups of children, aged 19–36 months and aged 37–48 months, could switch when a reversal was imposed but took significantly longer to learn a new rule on a former irrelevant dimension. Experiment 2 presented a wider set of novel stimuli which shared some features with the original set to further explore the basis of rule learning. The result was that tamarins and 52- to 60-month-old children both chose novel stimuli that fit the rule and had no a priori associative strength, suggesting a rule application not solely based on associative strength. Importantly, novel items introduced some risk for choice, and children showed themselves to be risk-averse, whereas tamarins were risk-prone within a novel context.

Background: The dwarf cuttlefish Sepia bandensis, a camouflaging cephalopod from the Indo-Pacific, is a promising new model organism for neuroscience, developmental biology, and evolutionary studies. Cuttlefish dynamically camouflage to their surroundings by altering the color, pattern, and texture of their skin. The skin's "pixels" (chromatophores) are controlled by motor neurons projecting from the brain. Thus, camouflage is a visible representation of neural activity. In addition to camouflage, the dwarf cuttlefish uses dynamic skin patterns for social communication. Despite more than 500 million years of evolutionary separation, cuttlefish and vertebrates converged to form limbs, camera-type eyes and a closed circulatory system. Moreover, cuttlefish have a striking ability to regenerate their limbs. Interrogation of these unique biological features will benefit from the development of a new set of tools. Dwarf cuttlefish reach sexual maturity in 4 months, they lay dozens of eggs over their 9-month lifespan, and the embryos develop to hatching in 1 month. Results: Here, we describe methods to culture dwarf cuttlefish embryos in vitro and define 25 stages of cuttlefish development. Conclusion: This staging series serves as a foundation for future technologies that can be used to address a myriad of developmental, neurobiological, and evolutionary questions.

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