One of my favorite photographic subjects is the Caribbean Reef Squid, a creature with amazing brainpower, keen vision, and a unique ability to communicate. They are very curious and friendly to people. Squid remind me of something out of Star Wars hovering in close and “flying” backward again and again.
“Sepioteuthis sepiodea” have torpedo-shaped bodies and are 10-20cm long, including the ten tentacles that are fixed in a circle around the mouth. Two of the arms are stronger/longer than the others. Along the mantle (body) are undulating fins and under the head is a funnel that can be turned in various directions and used for ‘jet’ propulsion. Internally, the Reef Squid has three hearts and blue blood (since it uses a blue, copper-containing protein called hemocyanin for binding oxygen).
Found throughout the Caribbean Sea, Bahamas and south Florida, adult Caribbean reef squid during the day often gather in schools – called ‘shoals’ – of four to 30 individuals; at night they disperse to hunt individually.
Voracious eaters, they consume 30-60% of their body weight daily, eating small fish, crabs and shrimp. They catch prey using their two larger tentacles and then use the other eight to move the food to the mouth, where a strong and sharp beak is used to cut the prey into pieces that can be further processed by a raspy tongue called a radula.
For camouflage and for surprisingly complex communication Reef Squid can rapidly change skin color and pattern by sending nerve pulses to receptors called chromatophores. In addition to a basic brown they display a zebra, a striped and a saddle pattern. In complex situations, such as the need to signal one thing to a female on the left and another to a rival male on the right, they can even use one pattern on one side and another pattern on the other.
Courtship occurs within a shoal several times during the day and year-round.
The reproduction of a Caribbean reef squid can be very complex. After a female lays her eggs she will then die. The male can reproduce with several females. After a male competes with several other males, the winning male gets the female. The male comes up to the female and slowly starts stroking her with his tentacles. The female will be alarmed and start flashing patterns. The male will then calm her by blowing water and swimming away. He will continue that process until the female accepts him. This process can continue for up to an hour. Once the female has accepted the male, he will put a sperm packet on her and while he is doing this he will display a pattern. The female will take the packet and will place it in her seminal receptacle. She will then find an appropriate place for her eggs, lays them, and then dies.
On average, squid have seven confrontations an hour with predators and employ a number of different strategies to protect themselves. Perhaps the most important is that of shoaling, during which the school has the advantage of many eyes. Typically, the shoal arranges itself in a column with the larger individuals positioned as sentinels at each end. When a sentinel signals alarm, the squid have a number of options. If the threat is mild, the response may be intimidation by extending the body fully and orienting perpendicular to the threat so as to emphasize size or by displaying special patterns, including flashing two or four ‘eye’ spots. Threats a bit more serious may result in attempting to blend into the background by using camouflage patterns. If flight is desirable, the direction of retreat may be hidden by the ejection of black ink. Rapid retreat is accomplished by jetting away. First, the squid expands its mantle, which fills the pallial cavity with water. Body muscles are then contracted to expel the water through the special funnel. If it has propelled itself above the surface, it can employ its fins as wings to ‘fly’ an ability that has only recently been certified by scientists, even though it will come as no surprise to cruisers who have found ink spots on the side of a hull or a cadaver on the deck.
Resources: Caribbean Reef Squid (Sepioteuthis sepioidea) By Kelly M. McKay, Dr. James B. Wood National Resource Center for Cephalopods