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Cephalopod intelligence

From Wikipedia, in a visual modern way
Two-thirds of an octopus's neurons are in the nerve cords of its tentacles, These are capable of complex reflex actions without input from the brain.[1]
Two-thirds of an octopus's neurons are in the nerve cords of its tentacles, These are capable of complex reflex actions without input from the brain.[1]

Cephalopod intelligence is a measure of the cognitive ability of the cephalopod class of molluscs.

Intelligence is generally defined as the process of acquiring, storing, retrieving, combining, comparing, and recontextualizing information and conceptual skills.[2] Though these criteria are difficult to measure in nonhuman animals, cephalopods seem to be exceptionally intelligent invertebrates. The study of cephalopod intelligence also has an important comparative aspect in the broader understanding of animal cognition because it relies on a nervous system fundamentally different from that of vertebrates.[3] In particular, the Coleoidea subclass (cuttlefish, squid, and octopuses) is thought to be the most intelligent invertebrates and an important example of advanced cognitive evolution in animals, though nautilus intelligence is also a subject of growing interest among zoologists.[4]

The scope of cephalopod intelligence and learning capability is controversial within the biological community, complicated by the inherent complexity of quantifying non-vertebrate intelligence. In spite of this, the existence of impressive spatial learning capacity, navigational abilities, and predatory techniques in cephalopods is widely acknowledged.[5][6]

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Cephalopod

Cephalopod

A cephalopod is any member of the molluscan class Cephalopoda such as a squid, octopus, cuttlefish, or nautilus. These exclusively marine animals are characterized by bilateral body symmetry, a prominent head, and a set of arms or tentacles modified from the primitive molluscan foot. Fishers sometimes call cephalopods "inkfish", referring to their common ability to squirt ink. The study of cephalopods is a branch of malacology known as teuthology.

Class (biology)

Class (biology)

In biological classification, class is a taxonomic rank, as well as a taxonomic unit, a taxon, in that rank. It is a group of related taxonomic orders. Other well-known ranks in descending order of size are life, domain, kingdom, phylum, order, family, genus, and species, with class fitting between phylum and order.

Animal cognition

Animal cognition

Animal cognition encompasses the mental capacities of non-human animals including insect cognition. The study of animal conditioning and learning used in this field was developed from comparative psychology. It has also been strongly influenced by research in ethology, behavioral ecology, and evolutionary psychology; the alternative name cognitive ethology is sometimes used. Many behaviors associated with the term animal intelligence are also subsumed within animal cognition.

Vertebrate

Vertebrate

Vertebrates comprise all animal taxa within the subphylum Vertebrata, including all mammals, birds, reptiles, amphibians and fish. Vertebrates represent the overwhelming majority of the phylum Chordata, with currently about 69,963 species described. Vertebrates comprise such groups as the following:jawless fish, which include hagfish and lampreys jawed vertebrates, which include: cartilaginous fish bony vertebrates, which include: ray-fins lobe-fins, which include: coelacanths and lungfish tetrapods

Coleoidea

Coleoidea

Subclass Coleoidea, or Dibranchiata, is the grouping of cephalopods containing all the various taxa popularly thought of as "soft-bodied" or "shell-less". Unlike its extant sister group, Nautiloidea, whose members have a rigid outer shell for protection, the coleoids have at most an internal cuttlebone, gladius, or shell that is used for buoyancy or support. Some species have lost their cuttlebone altogether, while in some it has been replaced by a chitinous support structure. A unique trait of the group is the ability to edit their own RNA.

Cuttlefish

Cuttlefish

Cuttlefish or cuttles are marine molluscs of the order Sepiida. They belong to the class Cephalopoda which also includes squid, octopuses, and nautiluses. Cuttlefish have a unique internal shell, the cuttlebone, which is used for control of buoyancy.

Squid

Squid

True squid are molluscs with an elongated soft body, large eyes, eight arms, and two tentacles in the superorder Decapodiformes, though many other molluscs within the broader Neocoleoidea are also called squid despite not strictly fitting these criteria. Like all other cephalopods, squid have a distinct head, bilateral symmetry, and a mantle. They are mainly soft-bodied, like octopuses, but have a small internal skeleton in the form of a rod-like gladius or pen, made of chitin.

Invertebrate

Invertebrate

Invertebrates are a paraphyletic group of animals that neither possess nor develop a vertebral column, derived from the notochord. This is a grouping including all animals apart from the chordate subphylum Vertebrata. Familiar examples of invertebrates include arthropods, mollusks, annelids, echinoderms and cnidarians.

Spatial memory

Spatial memory

In cognitive psychology and neuroscience, spatial memory is a form of memory responsible for the recording and recovery of information needed to plan a course to a location and to recall the location of an object or the occurrence of an event. Spatial memory is necessary for orientation in space. Spatial memory can also be divided into egocentric and allocentric spatial memory. A person's spatial memory is required to navigate around a familiar city. A rat's spatial memory is needed to learn the location of food at the end of a maze. In both humans and animals, spatial memories are summarized as a cognitive map.

Navigation

Navigation

Navigation is a field of study that focuses on the process of monitoring and controlling the movement of a craft or vehicle from one place to another. The field of navigation includes four general categories: land navigation, marine navigation, aeronautic navigation, and space navigation.

Predation

Predation

Predation is a biological interaction where one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation and parasitoidism. It is distinct from scavenging on dead prey, though many predators also scavenge; it overlaps with herbivory, as seed predators and destructive frugivores are predators.

Brain size and structure

Cephalopods have large, well-developed brains,[7][8][9] and their brain-to-body mass ratio is the largest among the invertebrates, falling between that of endothermic and ectothermic vertebrates.[10]

The nervous system of cephalopods is the most complex of all invertebrates.[9][11] The giant nerve fibers of the cephalopod mantle have been widely used for many years as experimental material in neurophysiology; their large diameter (due to lack of myelination) makes them relatively easy to study compared with other animals.[12]

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Brain

Brain

A brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. It is located in the head, usually close to the sensory organs for senses such as vision. It is the most complex organ in a vertebrate's body. In a human, the cerebral cortex contains approximately 14–16 billion neurons, and the estimated number of neurons in the cerebellum is 55–70 billion. Each neuron is connected by synapses to several thousand other neurons. These neurons typically communicate with one another by means of long fibers called axons, which carry trains of signal pulses called action potentials to distant parts of the brain or body targeting specific recipient cells.

Endotherm

Endotherm

An endotherm is an organism that maintains its body at a metabolically favorable temperature, largely by the use of heat released by its internal bodily functions instead of relying almost purely on ambient heat. Such internally generated heat is mainly an incidental product of the animal's routine metabolism, but under conditions of excessive cold or low activity an endotherm might apply special mechanisms adapted specifically to heat production. Examples include special-function muscular exertion such as shivering, and uncoupled oxidative metabolism, such as within brown adipose tissue.

Ectotherm

Ectotherm

An ectotherm is an organism in which internal physiological sources of heat are of relatively small or of quite negligible importance in controlling body temperature. Such organisms rely on environmental heat sources, which permit them to operate at very economical metabolic rates.

Nervous system

Nervous system

In biology, the nervous system is the highly complex part of an animal that coordinates its actions and sensory information by transmitting signals to and from different parts of its body. The nervous system detects environmental changes that impact the body, then works in tandem with the endocrine system to respond to such events. Nervous tissue first arose in wormlike organisms about 550 to 600 million years ago. In vertebrates it consists of two main parts, the central nervous system (CNS) and the peripheral nervous system (PNS). The CNS consists of the brain and spinal cord. The PNS consists mainly of nerves, which are enclosed bundles of the long fibers or axons, that connect the CNS to every other part of the body. Nerves that transmit signals from the brain are called motor nerves or efferent nerves, while those nerves that transmit information from the body to the CNS are called sensory nerves or afferent. Spinal nerves are mixed nerves that serve both functions. The PNS is divided into three separate subsystems, the somatic, autonomic, and enteric nervous systems. Somatic nerves mediate voluntary movement. The autonomic nervous system is further subdivided into the sympathetic and the parasympathetic nervous systems. The sympathetic nervous system is activated in cases of emergencies to mobilize energy, while the parasympathetic nervous system is activated when organisms are in a relaxed state. The enteric nervous system functions to control the gastrointestinal system. Both autonomic and enteric nervous systems function involuntarily. Nerves that exit from the cranium are called cranial nerves while those exiting from the spinal cord are called spinal nerves.

Nerve

Nerve

A nerve is an enclosed, cable-like bundle of nerve fibers in the peripheral nervous system.

Mantle (mollusc)

Mantle (mollusc)

The mantle is a significant part of the anatomy of molluscs: it is the dorsal body wall which covers the visceral mass and usually protrudes in the form of flaps well beyond the visceral mass itself.

Neurophysiology

Neurophysiology

Neurophysiology is a branch of physiology and neuroscience that studies nervous system function rather than nervous system architecture. This area aids in the diagnosis and monitoring of neurological diseases. Historically, it has been dominated by electrophysiology—the electrical recording of neural activity ranging from the molar to the cellular, such as patch clamp, voltage clamp, extracellular single-unit recording and recording of local field potentials. However, since the neurone is an electrochemical machine, it is difficult to isolate electrical events from the metabolic and molecular processes that cause them. Thus, neurophysiologists currently utilise tools from chemistry, physics, and molecular biology to examine brain activity.

Behavior

Predation

A veined octopus eating a crab.
A veined octopus eating a crab.

Unlike most other molluscs, all cephalopods are active predators (with the possible exceptions of the bigfin squid and vampire squid). Their need to locate and capture their prey has likely been the driving evolutionary force behind the development of their intelligence.[13]

Crabs, the staple food source of most octopus species, present significant challenges with their powerful pincers and their potential to exhaust the cephalopod's respiration system from a prolonged pursuit. In the face of these challenges, octopuses will instead seek out lobster traps and steal the bait inside. They are also known to climb aboard fishing boats and hide in the containers that hold dead or dying crabs.[14][15]

Captive cephalopods have also been known to climb out of their tanks, maneuver a distance of the lab floor, enter another aquarium to feed on the crabs, and return to their own aquariums.[16][17][18]

Communication

Although believed to not be the most social of animals, many cephalopods are in fact highly social creatures; when isolated from their own kind, some species have been observed shoaling with fish.[19]

Cephalopods are able to communicate visually using a diverse range of signals. To produce these signals, cephalopods can vary four types of communication elements: chromatic (skin coloration), skin texture (e.g. rough or smooth), posture, and locomotion. Changes in body appearance such as these are sometimes called polyphenism.[20] Some cephalopods are capable of rapid changes in skin colour and pattern through nervous control of chromatophores.[21] This ability almost certainly evolved primarily for camouflage, but squid use color, patterns, and flashing to communicate with each other in various courtship rituals.[20] Caribbean reef squid can even discriminate between recipients, sending one message using color patterns to a squid on their right, while they send another message to a squid on their left.[22][23]

The Humboldt squid shows extraordinary cooperation and communication in its hunting techniques. This is the first observation of cooperative hunting in invertebrates.[24]

It is believed that squids are slightly less intelligent than octopuses and cuttlefish; however, various species of squid are much more social and display greater social communications, etc., leading to some researchers concluding that squids are on par with dogs in terms of intelligence.[25]

Learning

A cuttlefish employing camouflage in its natural habitat.
A cuttlefish employing camouflage in its natural habitat.

In laboratory experiments, octopuses can be readily trained to distinguish between different shapes and patterns, and one study concluded that octopuses are capable of using observational learning;[26][27] however, this is disputed.[28][29]

Octopuses have also been observed in what has been described as play: repeatedly releasing bottles or toys into a circular current in their aquariums and then catching them.[30]

Cephalopods can demonstrably benefit from environmental enrichment[31] indicating behavioral and neuronal plasticity not exhibited by many other invertebrates.

In a study on social learning, common octopuses (observers) were allowed to watch other octopuses (demonstrators) select one of two objects that differed only in color. Subsequently, the observers consistently selected the same object as did the demonstrators.[32]

Both octopuses and nautiluses are capable of vertebrate-like spatial learning.[33]

Tool use

A small coconut octopus (4–5 cm in diameter) using a nut shell and clam shell as shelter.
A small coconut octopus (4–5 cm in diameter) using a nut shell and clam shell as shelter.

The octopus has repeatedly been shown to exhibit flexibility in the use of tools.

At least four individuals of the veined octopus (Amphioctopus marginatus) have been observed retrieving discarded coconut shells, manipulating them, transporting them some distance, and then reassembling them for use as shelter.[34] It is surmised that the octopuses used bivalves for the same purpose before humans made coconut shells widely available on the sea floor.[35][36] Other sea creatures construct homes in a similar manner; most hermit crabs use the discarded shells of other species for habitation, and some crabs place sea anemones on their carapaces to serve as camouflage. However, this behavior lacks the complexity of the octopus's fortress behavior, which involves picking up and carrying a tool for later use. (This argument remains contested by a number of biologists, who claim that the shells actually provide protection from bottom-dwelling predators in transport.[37]) Octopuses have also been known to deliberately place stones, shells, and even bits of broken bottles to form walls that constrict their den openings.[38]

In laboratory studies, Octopus mercatoris, a small pygmy species of octopus, has been observed to block its lair using plastic Lego bricks.[39]

Smaller individuals of the common blanket octopus (Tremoctopus violaceus) hold the tentacles of the Portuguese man o' war (whose venom they are immune to), both as means of protection and as a method of capturing prey.[40]

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Amphioctopus marginatus

Amphioctopus marginatus

Amphioctopus marginatus, also known as the coconut octopus and veined octopus, is a medium-sized cephalopod belonging to the genus Amphioctopus. It is found in tropical waters of the western Pacific Ocean. It commonly preys upon shrimp, crabs, and clams, and displays unusual behavior including bipedal walking and tool use.

Bigfin squid

Bigfin squid

Bigfin squids are a group of rarely seen cephalopods with a distinctive morphology. They are placed in the genus Magnapinna and family Magnapinnidae. Although the family is known only from larval, paralarval, and juvenile specimens, some authorities believe adult specimens have also been seen. Several videos have been taken of animals nicknamed the "long-arm squid", which appear to have a similar morphology. Since none of the seemingly adult specimens has ever been captured or sampled, it remains uncertain if they are of the same genus or only relatives.

Polyphenism

Polyphenism

A polyphenic trait is a trait for which multiple, discrete phenotypes can arise from a single genotype as a result of differing environmental conditions. It is therefore a special case of phenotypic plasticity.

Chromatophore

Chromatophore

Chromatophores are cells that produce color, of which many types are pigment-containing cells, or groups of cells, found in a wide range of animals including amphibians, fish, reptiles, crustaceans and cephalopods. Mammals and birds, in contrast, have a class of cells called melanocytes for coloration.

Camouflage

Camouflage

Camouflage is the use of any combination of materials, coloration, or illumination for concealment, either by making animals or objects hard to see, or by disguising them as something else. Examples include the leopard's spotted coat, the battledress of a modern soldier, and the leaf-mimic katydid's wings. A third approach, motion dazzle, confuses the observer with a conspicuous pattern, making the object visible but momentarily harder to locate, as well as making general aiming easier. The majority of camouflage methods aim for crypsis, often through a general resemblance to the background, high contrast disruptive coloration, eliminating shadow, and countershading. In the open ocean, where there is no background, the principal methods of camouflage are transparency, silvering, and countershading, while the ability to produce light is among other things used for counter-illumination on the undersides of cephalopods such as squid. Some animals, such as chameleons and octopuses, are capable of actively changing their skin pattern and colours, whether for camouflage or for signalling. It is possible that some plants use camouflage to evade being eaten by herbivores.

Caribbean reef squid

Caribbean reef squid

The Caribbean reef squid, commonly called the reef squid, is a species of small, torpedo-shaped squid with undulating fins that extend nearly the entire length of the body, approximately 20 cm (8 in) in length. In 2001, marine biologist Silvia Maciá discovered that squid were able to propel themselves up out of the water about 2 m (6.6 ft) and fly approximately 10 m (33 ft) before re-entry; a discovery which led to the identification of six species of flying squid.

Humboldt squid

Humboldt squid

The Humboldt squid, also known as jumbo squid or jumbo flying squid (EN), and Pota in Peru or Jibia in Chile (ES) is a large, predatory squid living in the eastern Pacific Ocean. It is the only known species of the genus Dosidicus of the subfamily Ommastrephinae, family Ommastrephidae.

Cuttlefish

Cuttlefish

Cuttlefish or cuttles are marine molluscs of the order Sepiida. They belong to the class Cephalopoda which also includes squid, octopuses, and nautiluses. Cuttlefish have a unique internal shell, the cuttlebone, which is used for control of buoyancy.

Octopus

Octopus

An octopus is a soft-bodied, eight-limbed mollusc of the order Octopoda. The order consists of some 300 species and is grouped within the class Cephalopoda with squids, cuttlefish, and nautiloids. Like other cephalopods, an octopus is bilaterally symmetric with two eyes and a beaked mouth at the center point of the eight limbs. The soft body can radically alter its shape, enabling octopuses to squeeze through small gaps. They trail their eight appendages behind them as they swim. The siphon is used both for respiration and for locomotion, by expelling a jet of water. Octopuses have a complex nervous system and excellent sight, and are among the most intelligent and behaviourally diverse of all invertebrates.

Observational learning

Observational learning

Observational learning is learning that occurs through observing the behavior of others. It is a form of social learning which takes various forms, based on various processes. In humans, this form of learning seems to not need reinforcement to occur, but instead, requires a social model such as a parent, sibling, friend, or teacher with surroundings. Particularly in childhood, a model is someone of authority or higher status in an environment. In animals, observational learning is often based on classical conditioning, in which an instinctive behavior is elicited by observing the behavior of another, but other processes may be involved as well.

Behavioral enrichment

Behavioral enrichment

Behavioral enrichment is an animal husbandry principle that seeks to enhance the quality of captive animal care by identifying and providing the environmental stimuli necessary for optimal psychological and physiological well-being. Enrichment can either be active or passive, depending on whether it requires direct contact between the animal and the enrichment. A variety of enrichment techniques are used to create desired outcomes similar to an animal's individual and species' history. Each of the techniques used is intended to stimulate the animal's senses similarly to how they would be activated in the wild. Provided enrichment may be seen in the form of auditory, olfactory, habitat factors, food, research projects, training, and objects.

Coconut

Coconut

The coconut tree is a member of the palm tree family (Arecaceae) and the only living species of the genus Cocos. The term "coconut" can refer to the whole coconut palm, the seed, or the fruit, which botanically is a drupe, not a nut. The name comes from the old Portuguese word coco, meaning "head" or "skull", after the three indentations on the coconut shell that resemble facial features. They are ubiquitous in coastal tropical regions and are a cultural icon of the tropics.

Problem-solving ability

The highly sensitive suction cups and prehensile arms of octopuses, squid, and cuttlefish allow them to hold and manipulate objects. However, unlike vertebrates, the motor skills of octopuses do not seem to depend upon mapping their body within their brains, as the ability to organize complex movements is not thought to be linked to particular arms.[41]

Cephalopods can solve complex puzzles requiring pushing or pulling actions, and can also unscrew the lids of containers and open the latches on acrylic boxes in order to obtain the food inside. They can also remember solutions to puzzles and learn to solve the same puzzle presented in different configurations.[42]

  • Octopus opening a container with a screw cap
  • Oktopus opening a container with screw cap 01.jpg
  • Oktopus opening a container with screw cap 02.jpg
  • Oktopus opening a container with screw cap 03.jpg
  • Oktopus opening a container with screw cap 04.jpg

Captive octopuses require stimulation or they will become lethargic; this typically takes the form of a variety of toys and puzzles.[43] At an aquarium in Coburg, Germany, an octopus named Otto was known to juggle his fellow tank-mates around, as well as throw rocks to smash the aquarium glass. On more than one occasion, Otto even caused short circuits by crawling out of his tank and shooting a jet of water at the overhead lamp.[44]

Additionally, cephalopods have been shown to have the capacity for future planning and reward processing after being tested with the Stanford marshmallow experiment.[45]

Protective legislation

An octopus in a zoo.
An octopus in a zoo.

Due to their intelligence, cephalopods are commonly protected by animal testing regulations that do not usually apply to invertebrates.

In the UK from 1993 to 2012, the common octopus (Octopus vulgaris) was the only invertebrate protected under the Animals (Scientific Procedures) Act 1986.[46]

Cephalopods are the only invertebrates protected under the 2010 European Union directive "on the protection of animals used for scientific purposes".[47]

In 2019, some scholars have argued for increased protections for cephalopods in the United States as well.[48]

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Animal testing regulations

Animal testing regulations

Animal testing regulations are guidelines that permit and control the use of non-human animals for scientific experimentation. They vary greatly around the world, but most governments aim to control the number of times individual animals may be used; the overall numbers used; and the degree of pain that may be inflicted without anesthetic.

Animals (Scientific Procedures) Act 1986

Animals (Scientific Procedures) Act 1986

The Animals Act 1986, sometimes referred to as ASPA, is an Act of the Parliament of the United Kingdom passed in 1986, which regulates the use of animals used for research in the UK. The Act permits studies to be conducted using animals for procedures such as breeding genetically modified animals, medical and veterinary advances, education, environmental toxicology and includes procedures requiring vivisection, if certain criteria are met. Revised legislation came into force on 1 January 2013. The original act related to the 1986 EU Directive 86/609/EEC which was updated and replaced by EU Directive 2010/63/EU

European Union

European Union

The European Union (EU) is a supranational political and economic union of 27 member states that are located primarily in Europe. The union has a total area of 4,233,255.3 km2 (1,634,469.0 sq mi) and an estimated total population of nearly 447 million. The EU has often been described as a sui generis political entity combining the characteristics of both a federation and a confederation.

Source: "Cephalopod intelligence", Wikipedia, Wikimedia Foundation, (2023, February 9th), https://en.wikipedia.org/wiki/Cephalopod_intelligence.

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Further Reading

Brain

Octopus

Squid

Cephalopod

Chromatophore

Vampire squid

Cephalization

Giant Pacific octopus

San-nakji

Cephalopod limb

Marine invertebrates

Mollusca

Cuttlefish

Cephalopod eye

Pain in animals

Pain in crustaceans

Underwater camouflage

Pain in invertebrates
See also
References
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