The BBC version
The original article, for those with access.
Darmaillacq, A.-S., et al., Embryonic visual learning in the cuttlefish, Sepia officinalis, Anim. Behav. (2008), doi:10.1016/j.anbehav.2008.02.006
This is an example of a really elegant preliminary experiment. It is simply designed and clearly tests an interesting question- can vertebrate embryos (specifically cuttlefish) learn via visual stimulation?
The researchers tested this question by exposing embryonic cuttlefish to a normal, but not favorite food source-crab. The embryos could see the crabs, but not interact with them in any other way. This was accomplished by using a special tank setup in which the cuttlefish embryos were kept in a compartment that totally separated them physically from the crabs while allowing them to see the crabs. (paper figure 1). The tanks were designed so that once the cuttlefish hatched, they would fall down to a part of the tank where they could no longer see the crabs.
Paper Figure 1:
After hatching, the cuttlefish were kept away from all food for 7 days. During this time the cuttlefish lived on their remaining embryonic reserves. The researchers then compared the feeding preferences of cuttlefish who had been visually exposed to crabs vs. those that had not. The cuttlefish were offered both crabs and shrimp and the researchers tracked which food the cuttlefish chose first. The differences were quite striking, despite the small sample size used. (paper figure 2). Cuttlefish exposed to crabs had a strong preference for crabs, cuttlefish not exposed to any particular food had a strong preference for shrimp. Neat! This research could lead to a lot of interesting follow-up questions- comparing different food preferences, determining how long they need to see the prey to imprint, is there a particular time where they imprint-i.e. do they imprint right before hatching, or does an earlier exposure influence them as well? I think it is really fascinating that the embryos retained the imprinting for seven days... that is better memory retention then some of my students demonstrate. No wonder cuttlefish write such good poetry. They are smart!
Paper Figure 2: