Fascinating Facts about Octopuses - Adorable, Dumbo and a Genome
Octopuses are fascinating invertebrates. At least some species have the intelligence that we normally associate with vertebrates. Octopuses have a different body structure from vertebrates, yet they can sense and manipulate objects very effectively. Researchers continue to discover new facts about these impressive and unusual animals.
Three especially interesting octopuses live off the coast of California. One lacks an official name but is sometimes described as adorable due to its cute appearance. The dumbo octopus reminds observers of the Disney cartoon character known as Dumbo the Elephant. Scientists have recently sequenced the genome of the California two-spot octopus and have found that it contains some very unusual features.
Octopuses or Octopi?
The word "octopus" comes from Ancient Greek and means "eight legs". Some people have assumed that the word octopus is derived from Latin, which would make its plural form "octopi". Since this assumption is incorrect, octopi is technically the wrong plural form of octopus.
Features of an Octopus
Most octopuses have some features in common. Since not all octopuses are well known and new species are still being discovered, there may be some that break the following "rules".
- All octopuses live in the ocean.
- They have a soft body (to a greater or lesser extent) with eight arms. In most species the arms have suckers.
- The arms of an octopus surround its mouth. The mouth contains a tough, parrot-like beak that is used to kill prey and tear it apart. Inside the beak is a tongue-like radula covered with rasping teeth.
- All octopuses have a venomous bite, which is some cases produces painful results. Only the blue-ringed octopus is dangerous to humans, however. Its bite is deadly and its venom kills rapidly.
- The sac-like body covering behind the head of an octopus is known as the mantle. The vital organs are located under the mantle.
- Many octopuses release ink from an ink sac when they are threatened. Octopus ink contains concentrated melanin, the same pigment that colours our skin and hair. The release of a cloud of ink confuses predators, allowing the octopus to escape.
More Octopus Features
- Most octopuses have a well developed eye which has an iris, a lens and a retina, like our eyes. Octopus eyes are believed to have evolved independently from those of humans.
- Octopuses breathe by means of gills. Water enters the body through an opening at the bottom of the mantle, flows over the gills and then leaves the body through a tube called the siphon. The siphon can be seen on the side of an octopus's body. The gills extract oxygen from the water and give up carbon dioxide.
- An octopus has three hearts.
- The blood of an octopus is blue. The pigment in the blood is called hemocyanin and contains copper. The pigment in our blood is called hemoglobin. It's red in colour and contains iron.
- Octopuses move by crawling over the ground or by swimming. Some swim by a type of jet propulsion. They absorb water through the opening in their mantle and then expel it forcefully through their siphon.
- At least two thirds of an octopus's neurons, or nerve cells, enter its arms. The arms can even perform jobs when separated from an octopus (for a limited time).
- At least some octopus species can solve problems and puzzles, learn new things and use tools.
- During mating, the male inserts a packet of sperm into the female's body with a specialized arm called a hectocotylus. Sometimes he detaches the arm with its sperm and gives it to the female to store until later.
- Fertlization takes place inside the female's body.
- Once the eggs are laid, the female cares for them until they hatch. She then leaves the youngsters to their fate.
- Sadly, octopuses don't live for very long. Some of the larger ones may live as long as five years, but that seems to be the maximum lifespan and isn't often attained. Some octopuses live for only six months. Females die soon after the eggs have hatched. Males die soon after reproduction as well.
Suborders in the Order Octopoda
Octopuses belong to the order Octopoda, which contains two suborders. Members of the suborder Cirrata have fins on their mantle and an internal shell. Members of the suborder Incirrata lack fins and an internal shell.
An Octopus That is Adorable
The Adorable Octopus - Possibly Opisthoteuthis adorabilis
The "adorable" octopus lives in the deep water of Monterey Bay in California. It doesn't have an official scientific or common name yet, even though the animal has been known since 1990. The name Opisthoteuthis adorabilis has been suggested. After studying the features of the octopus, scientists are certain that it should be classified in the genus Opisthoteuthis. They haven't decided on its species, however.
The octopus is small and delicate. It could definitely be classified as cute. It's pale to dark orange in colour and has a gelatinous and fragile body. The octopus also has large eyes, a feature that probably helps it to see in the dark water of its natural habitat. Its arms are short and webbed. There is a small fin located high up on each side of its mantle. The octopus spreads the web between its arms like a parachute and uses its fins to help it steer as it swims. The "parachute" is a feature of the family Opisthoteuthidae. Members of the family are known as umbrella octopuses.
Stephanie Bush is a scientist at the Monterey Bay Aquarium Research Institute. She is the researcher that has been most involved in the study of the octopus and came up with the idea of the "adorabilis" name. The final decision about the species name of the octopus will be hers.
The eggs of the adorable octopus take two and a half to three years to hatch. This long time period is common for the eggs of deep sea animals. The eggs have to develop in a cold environment under high pressure.
The Dumbo Octopus - Grimpoteuthis
Dumbo octopuses belong to the genus Grimpoteuthis. There are seventeen or eighteen specIes. They live in many places around the world in addition to California. Dumbo octopuses belong to the same family as the adorable octopus and have certain features in common with them, including the webbed arms and the fins. The fins of a dumbo octopus are long and substantial, however, and often look quite peculiar to people who are not familiar with the animal.
Like the adorable octopus, dumbo octopuses are small animals that live in deep water and have large eyes. They generally don't have the delicate appearance of the adorable octopus, however.
The dumbo octopus has a U-shaped shell inside its mantle. This means that its body is not completely soft and that it can't squeeze through small spaces, unlike the finless octopuses. The shell often gives the mantle a smooth and slightly bulbous appearance.
Dumbo the Elephant
Dumbo is a cartoon character in a 1941 Walt Disney movie of the same name. Dumbo has huge ears. He discovers that he can use his ears like wings and can fly.
A Dumbo Octopus Swimming in Deep and Cold Water
The Life of a Dumbo Octopus
Dumbo octopuses are predators, like other octopuses. They feed on worms, crustaceans, shellfish and copepods. They have a beak but may or may not have a radula. They usually swallow their prey whole.
Dumbo octopuses move by crawling over the ocean bottom and by swimming. They flap their fins and sometimes fold and unfold their "umbrella" as they swim. Their movements are often slow and graceful. They can use their siphon and the jet propulsion method favoured by finless octopuses if necessary, however.
The female dumbo octopus receives sperm from a male. Fertlization is internal. There is some evidence that the female contains eggs at different stages of development and can lay eggs at any time of the year.
Dumbo Octopus in Action
The adorable octopus, dumbo octopuses and other members of the finned suborder don't produce ink. There may be other major differences between them and the octopuses without fins. Finned octopuses are poorly understood at the moment.
The California Two-Spot Octopus - Octopus bimaculoides
The California two-spot octopus is a finless octopus. It's found in many locations, including California. Adults are variable in colour. They commonly have a mottled yellow, brown or grey appearance.
The name of the octopus comes from a large eye spot or ocellus below and slightly behind each eye. The ocellus consists of a black background containing a blue ring. It's more visible at some times than at others. For example, in the video below the ocellus can be seen at the start of the video and then disappears.
Like the other members of its suborder, the California two-spot octopus hides in a den when it's not hunting. It's a predator and eats crustaceans such as crabs and lobsters, mollusks and small fish. The octopus is also known as the bimac octopus and is sometimes kept as a pet.
California Two-Spot Octopus off Catalina Island
What is a Genome?
A genome is the complete set of genes in an organism. A gene is a section of a DNA molecule with a specific function. A single DNA molecule contains many genes and there are multiple DNA molecules in a cell. All the cells in an organism - with the exception of the eggs and sperm - contain identical DNA molecules. Not all of the genes in the DNA are active in a particular cell, however.
The Genome of the California Two-Spot Octopus
Scientists have jokingly said that the unusual genome of the California two-spot octopus comes from "something like an alien" in order to emphasize its intriguing nature. Octopuses aren't aliens from space, despite the claims of some publications, but their genome does have some unexpected features.
- The genome of the California two-spot octopus is nearly as large as a human's. In addition, it contains 33,000 genes that code for proteins. The human genome contains fewer than 25,000 protein-coding genes.
- The octopus genome contains 168 protocadherin genes, which is more than twice as many as humans. These genes are very important in the development of the nervous system and in the interaction of neurons.
- A gene family with the interesting name of zinc-finger transcription factors is greatly expanded in the octopus genome. The family contains about 1,800 genes in octopuses. These genes are thought to be important in octopus development.
- Researchers have found six genes that code for proteins called reflectins. These proteins control how light is reflected from the skin, thereby altering the appearance of the octopus.
A Section of a DNA or Deoxyribonucleic Acid Molecule
More Octopus Genome Discoveries
- The octopus genome shows that some of the animal's tissues have the ability to edit RNA (ribonucleic acid). DNA can't leave the nucleus of a cell. The ribosomes that make protein are located outside the nucleus, however. Normally, the DNA code in the nucleus is sent via RNA to the ribosomes, which make protein by reading the RNA code. If octopus proteins need to be changed, this can done by quickly changing the code in the RNA. The DNA doesn't have to be altered.
- Octopuses have a large number of transposons, or jumping genes, that move around in the genome.
- Genes that are active in the suckers of an octopus control the production of a protein that resembles the acetylcholine receptor in humans. Acetylcholine is a vital chemical in humans that controls the transmission of a nerve impulse from one neuron to another. Acetylcholine must bind to receptors on the surface of neurons in order to do its job. Researchers think that in the octopus the receptors are involved in the ability of the suckers to taste.
California Two-Spot Octopus Eggs Hatching
The Importance of Learning More about Octopuses
Octopuses are fascinating animals to observe and study. They are very unusual invertebrates and are an important part of their ecosystem. It's interesting and educational to learn about their lives and behaviour.
One of the amazing things about life on Earth is that all living things contain DNA and that genes work in the same way throughout the living world. The only entities that don't have DNA are some viruses. They do contain a genome, but it's made of RNA instead of DNA. This similarity between life forms means that by exploring DNA in other organisms - especially the more complex animals like octopuses - we may learn something that applies to our own genome. That's an intriguing thought.
- An analysis of the genome of the California two-spot octopus
© 2015 Linda Crampton
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