DID YOU SEE THE CUTTLEFISH ON THAT DIVE?

Photo by Betty Wills

No I didn’t!!! This is a conversation had frequently by experienced and inexperienced divers on our boat. In fact it happened again yesterday. The common Caribbean Reef Squid is large enough to be mistaken for a cuttlefish. However, cuttlefish don’t exist in the Caribbean.

Peculiar traits

Squid are members of the class cephalopoda. Cepha means head and poda means foot so you could call them head feet. Other cephalopods are octopus and… you guessed it cuttlefish. They really have no torso hense, their name. Only possessing a head and tentacles they have no bones and are therefore invertebrates.

Cephalopods are carnivores. They use their tentacles to eat fish, mollusks ie. clams, scallops, and conch, and crustaceans like shrimp, crab, and lobster. The tentacles pull the food to a small parrot like beak which tears the food into bite size morsels.

Humans have one heart with 4 chambers. 2 are ventricles. They build the pressure for the 2 atria to distribute to the body. One ventricle and one atria supply the oxygenated blood to the body for consumption. The other pair sends the blood now higher in carbon dioxide to the lungs to be reoxygenated.

In contrast, some squid have 2 hearts each with one atria and one ventricle. One heart sends the blood to the gills for oxygen while the other heart sends it to the body. Other squid have 1 heart with 1 ventricle and 2 atria. In this case the ventricle supplies the pressure while each atria boosts the blood to the respective organs. One to power the body and one for respiration.

While we are on the circulatory system, Sam reminded me that Cephalopods have a green blue blood. You have heard the term hemoglobin. Our blood has iron based proteins that carry oxygen making it red. Squid, octopus, and cuttlefish all have hemocyanic blood which is copper based proteins giving their blood a blue green tint.

Cephalopods skin is composed of many special cells called chromatophores. This allows them to change color and patterns rapidly. You might think this serves well for camouflage. You would be right. However, cephalopods have extremely large brains compared to their body mass and are therefore very intelligent. They use their color changes to communicate with each other rapidly. Divers often enjoy watching a chorus line of squid moving in synchronization as if they were all attached by wires. This is because the subtle changes in color pass the seemingly choreographed moves from one squid to the next almost instantaneously.

Reproduction

Sometimes you might notice a squid split down the middle with 2 different colors, generally red and blue. Then, in a split second it will reverse. When squid mate, anywhere from 2 to 5 males will compete for a females attention. The healthier the female the healthier males she will attract insuring survival of the fittest. Females are generally larger than males. But, the largest or healthiest of the males will insert himself between the other males and the female. He turns red on the side closest to her telling her “Hey baby I’m hot for you”. The other half turns blue telling approaching males to take a cold shower. If the advances come from the opposite side of the female he will switch his location and reverse his colors sending the same messages. Knowing this, if you pay attention you can stop and watch the act in process. I was fortunate enough to witness it, know what was happening, and stop some inexperienced divers to watch a National Geographic moment of a lifetime.

Once a male and female have separated to mate she may not accept him. He performs a dance blowing water on her until she finally gives in and says “I really don’t have a headache get it over with.”  This usually occurs in a very short time but can take as much as an hour. She has to be selective as she can only reproduce once. Males can fertilize more than one female. Squid reach maturity for reproduction within 1 to 2 years. At this point, the males have the largest male sex organ for their body size in the animal kingdom. It is short lived though as they die shortly after breeding season. After he inserts a packet of sperm onto the female he tries to find another partner until breeding season is over. The now “impregnated” female fertilizes her eggs by using her tentacles to relocate the sperm to her egg sack much like lobsters but that is another blog (stay tuned). When the eggs are fertilized she attaches them to the bottom usually in shallow water but I have seen them as much as 40 ft or 33 m deep. The clumps of eggs look like groups of white night light bulbs. If you look closely you can actually see the embryonic squid inside. When the female is done depositing her eggs her work on earth is through and she passes on.

The next time you see cuttlefish… excuse me SQUID, freeze. Watch them closely. Don’t forget to look behind you. My wife Laura always does. A school of squid usually sends out 2 sentry squid to detract you from the main body. Then she turns around and sees the entire school.

Until next time always make your total number od ascents equal your total number of descents.

Your really cool blogger

Duane.