Cuttlefish

Most people associate cuttlefish with domesticated budgies (the bird, not the male swimsuit). This is because budgies are given cuttlebone, a long ovulated white structure, to sharpen their beaks. This beautiful cuttlebone is an important feature of the cuttlefish; it controls their buoyancy while swimming in the ocean at various depths.

Cuttlefish can be found across the globe. They belong to a group of animals termed cephalopods, which also includes the octopus, squid, chambered nautilus and argonauts. Scientifically, cuttlefish belong to the Class Cephalopoda in the Phylum Mollusca. This means cuttlefish are invertebrates and have no backbone.

Cephalopods are considered amongst scientists to be the most intelligent out of all invertebrates; they learn quickly, are able to solve problems, communicate via complex visual communication and can quickly adapt to their local environment. Like chameleons on land, cuttlefish are experts at adapting to the colour and patterns of the environment around them.

Cuttlefish, as well as the octopus, contain special organs in their skin termed chromatophores which are little elastic bags filled with colour pigment. By expanding and contracting, chromatophores display a particular colour. They can be turned on and off which allows the cuttlefish to create a particular set of colours and patterns with its skin. Additionally, skin flaps, termed papillae, can be pushed or shaped to mimic their surroundings, for example, seaweed or coral. These colour and pattern changes are used for: mating and courting rituals, mate-guarding and camouflage to hide from predators.

Here are some more fascinating facts about cuttlefish:

Fact 1: Cuttlefish have very well developed eyes and acute vision. They are colour blind but respond to differences in light intensity rather than differences in wave length (which vertebrates, like humans, use to determine colour).

Fact 2: Cuttlefish are carnivores, that is, they eat meat. They are active nighttime predators feeding on fish, crustaceans, shellfish and worms.

Fact 3:  During mating, the male passes packets of sperm to the female using its modified arm termed the hectocotylus. The females can immediately fertilise their eggs or are able to store the sperm in special receptacles inside their body for periods of time until they want to fertilise their eggs.

Fact 4:  Females attach the fertilised eggs to the seafloor either on or under hard surfaces such as rocks. Young cuttlefish develop with no parental assistance and many hatchings are carried around in surface ocean currents over long distances.

Fact 5:  Cuttlefish have 8 arms and 2 feeding tentacles. All arms have suckers along the length of the arm except for the feeding tentacles which have suckers only on the tip, termed clubs. The feeding tentacles can be pulled back into the mouth.

The Giant cuttle, Sepia apama, is found in southern temperate Australia extending from Western Australia to New South Wales. This species of cuttlefish can be identified by the three flat skin folds behind the eye and adults are often very curious.
The Giant cuttle, Sepia apama, is found in southern temperate Australia extending from Western Australia to New South Wales. This species of cuttlefish can be identified by the three flat skin folds behind the eye and adults are often very curious.

Fact 6: A cuttlefish’s mouth contains a hard beak, similar to a parrot’s beak. The beak is used to kill and paralyse the prey by injecting a poisonous saliva. The beak also breaks the prey into pieces and then it is further broken down with a row of very small sharp teeth.

Fact 7: When scared or irritated, cuttlefish squirt ink into the water column which can be shaped to be the same size as its body. This ink sac sits inside the body near the anus. Cuttlefish are also able to bury themselves under sand, with only the eyes remaining visible, when they want to hide.

Fact 8: Cuttlefish use their funnel and fins to swim. The fins extend out from its mantle (the back part of its body) enabling rapid or slow propulsion.

Many larger marine animals such as seals, whales and large fish eat cuttlefish, however, they are rarely caught in fisher nets. Perhaps this is indicative of their intelligence and being able to problem solve in difficult situations?

SEA SPIDERS

At Dalton Koss HQ we can already hear the arachnophobes fearfully exclaiming, “Sea Spiders! Will they bite me if I go for a swim? Are they poisonous?”

The answer to both questions is no. Sea Spiders are not interested in devouring humans.

Sea Spiders are scientifically known as pycnogonids. You can see in the image below, that sea spiders are not as chunky looking as their land dwelling cousins and are quite small in size (the Sea Spider in this image was no bigger than a $1 Australian coin).

This sea spider's scientific name is Pseudopallene ambigua and was found moving around a subtidal rocky reef inside Port Phillip Heads Marine National Parks, Victoria, Australia.
This sea spider’s scientific name is Pseudopallene ambigua and was found moving around a subtidal rocky reef inside Port Phillip Heads Marine National Parks, Victoria, Australia. The arrows point to several interesting body features.

This is because Sea Spiders have developed a number of really interesting body features over a long period of time. Here are just a few interesting feature facts:

Fact 1: The abdomen of the sea spider is very small and located towards the back of the body, while some of the gut is located in its legs. Their waste products are released directly into the seawater via a diffusion process across their cell walls.

Fact 2: Sea spiders use the same cell wall diffusion process to obtain oxygen, i.e. they have no lungs or respiratory system to breathe oxygen like many other animals.

Fact 3: Due to their very small body size, the sea spider’s reproductive system is found in their legs.

Fact 4: Female sea spiders deposit their fertilised eggs, which are then picked up and looked after by the male sea spider.

Fact 5: Most sea spider legs end in very small claws.

Fact 6: At each growth stage, starting from the larval phase, the sea spider develops a new set of legs until it reaches adulthood.

Fact 7. Sea spiders have a proboscis (think of it as their mouth and tongue rolled into one) so that they can suck out the fluids of animals they eat, for example, anemones, hydroids and bryozoans, but NOT humans.

Fact 8: Sea Spiders live in cool and warm water oceans at all depths.

How can I spot a Sea Spider?

Dalton Koss HQ’s tip for spotting a sea spider is to use a snorkel and mask and slowly drift over rocky reefs at high tide (for safety, always snorkel with a buddy). Sea Spiders are quite small so you need to look closely between seaweed tufts, anemones and other hydroids that grow on the rock.

Sea Anemones of the Southern Ocean

At DKHQ we are constantly asked whether some of the facts portrayed on Finding Nemo are true, specifically the much difficult to pronounce Sea Anemone. Pixar did a wonderful job raising the profile of tropical reefs, although to the detriment of Clown Fish who, if the facts are correct, were being flushed down toilets by young children wanting to release ‘Nemo’ back into the ocean.

This aside, the often asked sea anemone questions at DKHQ are: a. can sea anemones sting, and b. can their poison kill humans? The answer to a. is yes and to b. is no. This public fascination with sea anemones inspired today’s DKHQ Marine Fact, with a focus on southern sea anemones.

Unlike the large sea anemones of our tropical reefs systems found across the globe’s equator line, the sea anemones of the southern ocean are comparatively smaller but just as beautiful and colourful. Here are some interesting facts:

1. Southern sea anemones always occur as solitary individuals usually in intertidal and subtidal areas.

2. All sea anemones have one opening, function both as its mouth and anus (this fact usually elicits some funny facial and noise reactions). Sea anemones are carnivores, on other animals.

3. The sea anemone body is supported by water pressure, which means when not in water their body and tentacles become floppy.

4. The tentacles of all sea anemones radiate from the mouth in one or many rows and are hollow. These tentacles contain stinging cells known in marine science as nematocysts. Each nematocyst contains a pressurised coil that can be pushed out to capture prey or used as self defence. The sea anemone use the nematocysts to stun, and in some cases, kill the prey.

5. Nearly all southern ocean sea anemones grow attached to a rock or some other type of hard structure. The exception to this rule (and when it comes to Mother Nature, there is usually one exception to the rule) is the Swimming anemone known by its scientific name as Phlyctenactis tubercles. (See image below). The Swimming anemone can move through the current or crawl along hard structures.

The Swimming anemone, Phlyctenactis tuberculosa.
The Swimming anemone, Phlyctenactis tuberculosa.

So why can’t sea anemones sting us? Our skin is too thick to be penetrated by its stinging cells, unlike many sea creatures with very thin skin. In the case of Clown fish, they have adapted over a long time for their skin to not be affected by the stinging cells and use the sea anemone as a place of protection from enemies.

DKHQ hopes you enjoyed these sea anemone facts and will leave you to enjoy the beautiful colours of some of the southern ocean’s sea anemones.

This beautiful sea anemone is known as Phlyctenanthus australis and can be found along Australia's intertidal shoreline that is exposed to ocean waves.
This beautiful sea anemone is known as Phlyctenanthus australis and can be found along Australia’s intertidal shoreline that is exposed to ocean waves.
This gorgeous red sea anemone is known as the Waratah Anemone and it's scientific name Actinia tenebrosa. This lovely Waratah Anemone can be found along the intertidal shoreline, often looking like a red blob at low tide.
This gorgeous red sea anemone is known as the Waratah Anemone and it’s scientific name Actinia tenebrosa. This lovely Waratah Anemone can be found along the intertidal shoreline, often looking like a red blob at low tide.
This fun orange and white stripped sea anemone is known as Anthothoe alboctinia and can be found under rocks or underhangs along Australia's intertidal shoreline that is exposed to ocean waves.
This fun orange and white stripped sea anemone is known as Anthothoe alboctinia and can be found under rocks or underhangs along Australia’s southern intertidal shoreline that is exposed to ocean waves. There are two variations to this sea anemone, white and orange stripes and brown and green stripes.

What creates those circular holes on seashells?

At Dalton Koss HQ we are often asked wonderful questions about the coastal and marine environment that we are only too happy to answer.

One question beach lovers often ask us is how are those incredibly circular holes made on the shells? The holes are so perfect, that the shells can be used as a necklace pendant (see image above).

If you recall last week’s Marine Fact, Dalton Koss HQ discussed the difference between carnivore and herbivore marine snails. Leading on from this discussion, the holes you see on these shells are made by carnivore marine snails, or more specifically by their radula.

A radula is similar to our tongue in that it assists the snail to eat. However, unlike a human’s tongue a radula looks and functions like a chainsaw (see image below). The radula is comprised of teeth like structures that have the ability to cut through hard surfaces, such as a calcareous shell. The snail will stay in one place while the radula chainsaws through the shell, hence creating a beautiful concentric circle.

Once the snail breaks through the shell, it will kill and eat the animal inside. Unfortunately, a sad ending for the prey but enabling the carnivore marine snail to survive another day.

Radula
The radula is located inside the snails mouth and acts like a chainsaw drilling through tough surfaces. Image sourced from: noaa.gov/ocean