Chameleons of sea under threat

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They are referred to as the ‘Chameleons of the Sea’ due to their colour-changing abilities. They are an amazing spectacle of colour, shining and blinking in the ocean. At night they glow in the dark to hypnotise prey and flash messages to communicate in colourful spots, splotches and background colour.

It is a remarkable sight to see them during courtship, when the males dance in front of the females with their bodies taking on a shining blue amidst the clear blue waters of the ocean.  

It is no doubt a wonderful sight to see the ocean come alive when the Pharaoh Cuttlefish (Sepia pharaonis) also known as the Maha della or Pol della changes colour. They are like Vesak lanterns – not hanging from trees but floating in the ocean. They use their bioluminescence to light up the underside of their body with a dim glow, to disguise themselves from predators below which is a strategy called counter illumination.

This is one of the few species that can change colour. Researchers have revealed that the Pharaoh Cuttlefish despite being colour blind can even successfully change its skin colour, pattern and texture to match its surroundings in complete darkness. The fact that common cuttlefish can camouflage themselves successfully during night may reflect highly developed night-time visual abilities.

According to research a cuttlefish has maybe ten million little colour cells in its skin, and each one of them is controlled by a neuron (nerve cell). It is believed that cuttlefish, squid and octopuses are all cephalopods, a group that evolved over 400 million years ago from a mollusk ancestor.

Amazing and unique creature

It is not everybody who gets the chance to see the Pharaoh Cuttlefish in all its glory. But for those of you who have seen this amazing and unique creature of the ocean, it is an experience you will never forget. However the beauty and excitement of witnessing this remarkable species in action may soon be a thing of the past if proper measures are not taken to protect it from human predation.

Ocean Resources Conservation Association (ORCA) Marine Naturalist Prasanna Weerakkody told Ceylon Today the Pharaoh Cuttlefish have a heavy predation from human beings. “They are big animals and have the weight to be used as a food source. But the Pharaoh Cuttlefish is not tasty to eat. They are sold in supermarkets. When we start harvesting heavily the species completely disappears. This has been happening on the reef for the past two to three years. When I went diving recently I saw only one or two on the reef. But on earlier occasions I saw bigger numbers. If not managed now the Pharaoh Cuttlefish will go extinct,” Weerakkody explained.

He said the octopus and cuttlefish are mollusks and that the Pharaoh Cuttlefish lives on coral reefs, sandstone reefs and relatively shallow water of 30 feet to 40 feet.“The males are usually larger than the females. The female Pharaoh Cuttlefish eats the male after mating. They breed only once in their lifetime. The female cuttlefish and octopus lay 200 to 300 eggs. The normal squid lays 1,000 to 2,000 eggs. She farms the eggs and increases the oxygen level till the eggs hatch. If you catch a juvenile Pharaoh Cuttlefish it has not had a chance to breed,” Weerakkody said.

He added that any species of cuttlefish that is caught is sold in the market and this denies the Pharaoh Cuttlefish the chance to breed and produce young. “When they are caught regularly their population decreases. From a group of 200 to 500 cuttlefish only one to five survive. If left to produce on the reef they can contribute to tourism immensely, as they have the capacity to change colour from light to dark brown to black. They usually use this for camouflage in their normal life. During courtship time they go into display and flash colours like the male peacocks do when they want to attract a female,” Weerakkody explains.

Flashing colours of shining blue

Their flashing marking colours of white become a shining blue during courtship, he said and four to five males would surround one female with their flashing colours during courtship time. “This is beautiful to watch. The Pharaoh Cuttlefish is presently under threat as coral reefs where they live are dying out and if they are heavily harvested together with habitat loss they are not likely to survive.The species is not protected in Sri Lanka. But management measures need to be brought in now to save the remaining species in Sri Lankan waters,” Weerakkody said.

Commenting on the protection status of the Pharaoh Cuttlefish, Environment Lawyer Dr. Jagath Gunawardana said the International Union for Conservation of Nature (IUCN) said it is Data Deficient which means it is a poorly studied species. “Since it is a Data Deficient species we have no problem in trying to protect it. So we can protect it under the Fauna and Flora Protection Ordinance (FFPO) or under the Fisheries and Aquatic Resources Act. We can in fact protect it under both. If somebody has some information on this species they can write to the authorities and explain the situation. Then measures can be taken to protect this species. We can request immediately,” Dr. Gunawardana said.   

Cuttlefish diets vary depending on where in the ocean they live, but they commonly feed on small shrimps, shellfish, fish, octopus, worms, crabs that are smaller than themselves and even other cuttlefish. However, they are known to be cannibalistic if they can’t find any other food.Their natural predators include dolphins, sharks, large fish, seals, seabirds, and other cuttlefish. Researchers have found the largest recorded male being 80 cm long and weighing about 5 kg, and the maximum record for a female is 50 cm long, weighing 2 kg from the Persian Gulf.

The Pharaoh Cuttlefish lives in warm waters (30°C) in the Western Indian Ocean. Cuttlefish are the most commonly caught cuttlefish species in the Persian Gulf, either for aquarium use or for human consumption.

No care from parents

“Soon after mating, the female lays her eggs. She attaches them individually to objects near the sea floor. The eggs take about one to two months to hatch, depending on the water temperature. Juvenile cuttlefish are only 0.5 cm when they hatch! Right from the moment of hatching, sight is a crucial part of a cuttlefish’s life, for they receive no care from their parents and have to find their food.Once spawning is complete, the shoal of cuttlefish disappear back into the open sea. The hatchlings, called ‘cuttlets,’ are tiny replicas of their parents. Each individual is small enough to fit inside a quarter teaspoon. Once they emerge from the egg sac, they begin hunting,” Researchers say.

According to research it has been found that cuttlefish are known to use their beaks to defend themselves against predators. “In addition to their ability to use camouflage to sneak up on prey, they flash several colours and waves of light toward their prey, apparently to hypnotise them. They then strike with their feeding tentacles and pull the prey toward their beaked mouths. Cuttlefish are exclusively marine species and can be found in most marine habitats from shallow seas to deep depths and in cold to tropical seas,” Researchers explain.

The typical life expectancy of a cuttlefish, researchers say, is about one to two years and studies are said to indicate cuttlefish to be among the most intelligent invertebrates. “They lack external armour, so they use their impressive intelligence and camouflage abilities to outsmart predators. Cuttlefish have large brains relative to their body size and three hearts. While it uses two of its hearts to pump blood into the gills (the lung of fish) where it absorbs oxygen, the third heart pumps blood into the other organs. With their flattened bodies, cuttlefish are well suited to life on the sea bed,” Researchers explain.

Cuttlefish are venomous

Cuttlefish can’t see in colour as the eyes of cuttlefish, octopuses, and their relatives contain just one kind of colour-sensitive protein, researchers say, that apparently restricts them to a black and white view of the world. According to a recent study, all octopuses, cuttlefish, and some squid were found to be venomous and capable of delivering a toxic bite.

“Squids and cuttlefish are fast moving shell-less snails. They have two methods of swimming. They can jet propel themselves backwards by sucking water into their body cavity and then expelling it through a funnel. This produces a very rapid backward movement, which is usually used for escaping predators as it needs a great deal of energy.

According to historical records the Pharaoh Cuttlefish is native to at least the Western Indian Ocean, including the Red Sea and Persian Gulf. The species is thought to have reached the Mediterranean Sea as a migrant via the Suez Canal after many of its cuttlebones were found washed up on beaches in Israel in the early 2000s.

Studies done on cuttlefish have revealed that they use a three step process of attention, positioning, and seizure when hunting for prey. Adult Pharaoh Cuttlefish and most juveniles begin their attention stance with throwing their arms and tentacles into a triangle shape turning to the prey, followed by a positioning stage where the tentacles are moved slowly from the centre of the triangle as they move towards their prey. They finish this with their seizure phase where they move forward until lunging their tentacles rapidly to grasp their prey before retracting the prey back towards them.

“The Pharoah Cuttlefish have adapted to using this ambush style of tentacle lunging due to their small squat body size and lack of speedy propulsion.  Additionally in the past cuttlefish ink was known as an important dye called sepia. Today, artificial dyes have mostly replaced this natural sepia,’ researchers say.

By Risidra Mendis