The Mysterious Cuttlefish at Similan Islands Thailand

Cuttlefish

Introduction
Comic book writers have often looked to the animal world for inspiration when creating their superheroes. From flying to the ability to crawl up walls and throw out a web from their wrist, tiny little animals have been the source of inspiration. However, it seems no writers have looked at the mysterious cuttlefish for inspiration, because if they had, the resulting super hero would be a hero to end all other superheroes, since this small invertebrate has some truly astounding and unique features. Read along, and the next time you see a cuttlefish while diving, you will see it in a completely different light.

Biology of Cuttlefish

The first thing to be noted about cuttlefish is that they are actually mollusks that belong to the order Sepiida, of the class Cephalopoda, and are therefore cousins to the Octopuses and the squids. Like the squids, they have eight arms and two tentacles that are used not only to secure prey but also to taste with. Unlike the squid which has two lateral fins at the top of its mantle, the cuttlefish has a long ribbon-like fin that surrounds the mantle completely.
All cuttlefish are venomous like some squids and some octopuses, and like the rest of the cephalopod family they all have the ability to spray out a jet of defensive ink to cover their escape as well as confuse a predator’s sense of smell.
Find more about Cuttlefish at: www.thecephalopodpage.org or at marinebio.org

Sexual Subterfuge

Since cuttlefish reproduction is based around large males guarding a den with a female, smaller males have to get creative if they are to succeed in mating that year. It is not uncommon for the smaller males to pretend to be females by changing their colour and hiding their extra arms in order to slip past the guard. They have even been known to pretend to be carrying an egg sac so that they can bypass the male and mate with the guarded female.

Distribution and Habitat

Cuttlefish have quite an interesting geographical distribution; although they are warm water dwellers, they are found in tropical and subtropical locations around the world except from the Americas, where they are conspicuously absent. This old world creature is thought to have been a late developer in evolutionary terms, and as such by the time they had evolved, the Atlantic had become too deep and too cold for them to cross and reach the Americas.
Cuttlefish have a very broad and diverse depth range depending on each individual species, with some cuttlefish choosing to spend most of their time in a few meters of water, while some others can be found lurking around as deep as 600 meters.

Jet propulsion

Cuttlefish have two direct methods of swimming. While they normally use the fin that surrounds the mantel for everyday life and propulsion, when the necessity arises it goes to after burners. When it needs to escape with a big burst of speed, the cuttlefish turns on its jet propulsion systems. When in need, the creature can suck in water and use its powerful muscles to expel the water forcefully, creating its own unique form of jet propulsion.

Its own unique BCD

If you ever visit someone who has a bird as a pet, you will very likely see a small white oval shaped object at the bottom of the bird’s cage. This is a cuttlebone, given to the birds as a calcium supplement; however, it serves a very different purpose for the cuttlefish, since it acts like a Buoyancy control device. This very porous structure made of calcium carbonate is what the cuttlefish uses to control its buoyancy. It does this by controlling the gas to liquid ratio in the cuttlebone, just like a diver controls the amount of air in his BCD.

Cuttlefish: The mastermind of the Sea

For invertebrates, cuttlefish are smart. In fact, cuttlefish and their cephalopod cousins (octopi and squids) are considered the Einstein’s of the invertebrate world. With the largest brain to body mass ratio of all invertebrates, this class of mollusks have shown some amazing intelligence. They have great spatial learning and can navigate mazes, as well as developed very interesting communication techniques. Some cuttlefish can use one half of their body to send a colour-coded signal to its neighbor, while at the same time using the other half of its body to send a completely different colour-coded message to the cuttlefish on its other side. They have also evolved predation and hunting techniques to enable them to deal with their main prey, crabs, since they could pose a significant problem with their pincers and hard shells.
They are considered so intelligent that they are the only invertebrates that are protected under European union directives regarding animals used for scientific purposes.

Is it true a cuttlefish has more than one heart?

Which dive sites can I see cuttlefish at the Similan islands?

Wait a minute, did you say green blood?

Can cuttlefish see behind them?

What have we learned from cuttlefish?