I’m in Boston for a couple of days to attend an optics meeting, and I snuck out for an hour this afternoon to visit the lovely New England Aquarium!

Entrance to the New England Aquarium.

Even though I’m a physicist, I love visiting such places, because I always learn something new about the natural world. This trip was no exception — below, I share a few photos of things I learned and creatures I encountered while at the aquarium.

Right inside the door, visitors are immediately greeted with the sight of many, many penguins. I imagine it’s a nice “warm up” to the exotic marine life that one finds deeper in the building.

Penguins are rather awkward on land, but are spectacular swimmers! I caught a “school” of penguins swimming together on video.

The next thing that caught my attention were the seadragons.  The most spectacular one is the leafy seadragon, whose name is quite appropriate.  As one can tell from their appearance, seadragons are related to seahorses.  The odd appearance of the leafy seadragon makes it look like a floating piece of seaweed, a disguise that camouflages it from predators.

Less flamboyant, but more dragon-like, in my opinion, was its tank-mate, the weedy seadragon.

It kind of reminds me of the “dragons” from the classic Atari 2600 game, Adventure:

Dragons from 1979 video game Adventure.

The leafy seadragon, the weedy seadragon, and seahorses all share the trait that the males are the ones that carry and care for the eggs after they have been laid by the female.

The next fish caught my eye because of its eyes above the surface of the water, but it turns out that this isn’t its strangest quirk!

This fish is the largescale foureyes.  It doesn’t actually have four eyes, but it floats with part of its eyes above and below the water, and has separate pupils for viewing each area simultaneously, with appropriate optics!  This way, it can constantly look out for predators and food above and below the surface.

The next creatures look like some sort of alien eggs…

… but they are a type of jelly, the flower hat jelly, native to the waters around Japan.  They catch small fish with their stinging tentacles — fortunately, this sting isn’t dangerous to humans, though it can hurt!

The next fish, the blackbelly rosefish, doesn’t have any particularly surprising characteristics, but it is a lovely creature.

The dim lighting of the photograph doesn’t do the coloration of the rosefish enough justice!

The next fish, however, looks a little like something out of a horror movie.

This is a goosefish, a type of anglerfish that lures prey to its mouth with a “fishing rod” of sorts, attached to its head. In this photo, you can clearly see the spine, connected right around the mouth, that goes right up between the eyes to the leafy object on the top of its head. The goosefish can move this down to lure fish towards its mouth for an each meal.

Circling to the other side of the aquarium, I came across some rockhopper penguins, with their distinctive “hairstyle!”

One of my last stops was to visit the common cuttlefish, and admire their beautiful patterning and graceful motion.

If you look closely at the cuttlefish eyes, you’ll notice something very strange: they have “W”-shaped pupils!  You can see this more clearly below:

This is a very strange adaptation: the shape of the eye’s pupil dictates the shape of the spot of light that appears on the retina of the eye, and in general one wants this to be a circular pupil to get a good image.  So why does the cuttlefish have a “W” pupil?

Curiously, there seem to be several hypotheses, and more than one may be correct. A 2013 paper suggested that this shape helps the cuttlefish compensate for the uneven vertical distribution of light in the ocean (i.e. different intensities of light from above and below). In fact, in low light, the cuttlefish pupil expands to a circular shape. Work reported this year, however, suggests an even more spectacular idea: the “W”-shape actually helps the officially colorblind cuttlefish see color!  Different colors would be distorted differently by the odd shape of the pupil, and the cuttlefish may use these differences in distortions to distinguish colors, even though their retinas only have a single type of light receptor and thus only measure brightness, not color variations.

Speaking of light, my final stop in the aquarium was a visit to the sea lions, and I found that sea lions are not much different from cats when it comes to catching a few rays of the sun.

There was much more to see at the aquarium, but I had to get back to the optics meeting to give my talk! I hope you enjoyed this very brief look at aquatic life — and learned a little about the optics of marine creatures in the process!