Cephalopods are always a highlight on any day of snorkeling, and one of the groups of cephalopods we come across frequently on our trips is the cuttlefish. Closely-related to squids and nautiluses, cuttlefish share the incredible intelligence and color-changing abilities of their evolutionary cousins. They can be distinguished from squid and octopus by a number of features. Squid are thinner, shaped liked a torpedo for speed, while cuttlefish are stockier and usually move more slowly. Octopus have only eight tentacles, rather than the ten of squid and cuttlefish, but it can be difficult to count them underwater! The best way to tell cuttlefish apart from octopus is the body shape: octopus are all arms with a round body, and are usually found on the bottom, whereas cuttlefish are generally hovering above the reef.
Cuttlefish capturing prey
Unlike many reef-dwelling invertebrates we see on our trips that are beautiful but relatively boring behavior-wise (i.e. nudibranchs), cuttlefish have a range of interesting behaviors to witness while snorkeling. The first one that you notice when you spy a cuttlefish is its ability to change color and texture in seconds. Specially evolved tissues in cephalopod’s skin called chromatophores and papillae use tiny muscle fibers to control color patterns and skin texture for a range of reasons. The most obvious benefit is camouflage, blending the animal in to its environment to protect from predators and sneak up on prey. But there are other reasons for changing color, including communication with each other and confusing prey with pulses of color.
Another behavior we occasionally notice while snorkeling is hunting. The cuttlefish will slowly approach its target, often changing color and contorting its tentacles to disguise its shape, then shoot two longer “feeding arms” forward at its intended victim.
Reproductive behavior is always incredible to witness, and on our most recent trip we were fortunate to get a glimpse of these more intimate moments of cuttlefish’s lives. The broadclub cuttlefish, which is the large, reef-dwelling species we most often encounter, has an interesting mating system that involves a large male with a small harem of females that he will mate with. He will protect these females from other males, keeping a watchful eye on them until their eggs are laid. However, some smaller male cuttlefish have figured out that they can alter their color and behavior to appear like a female, which lets them sneak past the dominant male and get close to a female. Then, these “sneaker males” will quickly mate and depart, leaving the guarding male none the wiser.
Newly hatched cuttlefish
The act of mating is face-to-face, with both individuals spreading their tentacles out, the male wrapping his tentacles around her head while he passes her a packet of sperm, which she then stores in her mantle to later fertilize her eggs. Cuttlefish only breed once in their lives, so they make sure their future generation is protected. Eggs are laid in crevices on the reef, often hidden below a stinging coral or under a piece of rubble. There the young develop in white, grape-sized eggs for a month or two, before hatching as tiny, fully-formed cuttlefish! These babies are able to change color and forage for prey from the moment they emerge.