Memory Behaviors in Cephalopods - Literature review Example

Memory behaviors in Cephalopods Cephalopods fall within the Mollusca group and are quite ancient and specialized. They are very highly evolved such that in several of their behavioral features, they have so many similarities with fishes as compared to invertebrates. The Cephalopod intelligence has a very crucial comparative aspect in comprehending intelligence since it mostly relies on a fundamentally different nervous system from that of other vertebrates. The Mollusca class of cephalopod, especially the subclass of Coleoidea (squid, cuttlefish and octopuses) are deemed to be the most intelligent and advanced of invertebrates and a very important example of a complex cognitive evolution amongst animals (Hanlon, Messenger, 1996) There is controversy regarding the scope of intelligence in Cephalopods and further complicated due to challenges encountered while studying these fundamentally different and elusive creatures. Cephalopods have got amazing spatial learning capabilities, navigational abilities and their predatory techniques are beyond question (Hanlon, Messenger, 1996) Our understanding of the various neural processes that are involved in the mediation of complex behaviors may be better understood by carrying out comparative analysis of various brain mechanisms of invertebrates with such sophisticated behavior such as that of cephalopods(Hanlon and Messenger,1996).The most ideal cephalopod for such comparative study is the octopus which together with other modern cephalopods have evolved from slowly, shell-protected scavengers into highly agile, mobile predators that share their way of life and environment with fish and are successfully competing with them. This particular paper is going to focus on memory patterns and neurological development of the octopus and Nautilus. Memory patterns in octopus Before we can examine the memory patterns in octopuses, it’s important to give a brief description of their morphology, scientific classification, bodies and general behavior. The octopus belongs to the kingdom Animalia,Phylum Mollusca, class Cephalopoda,superorder Octopodiformes and Order Octopoda.the octopus has got two eyes, four pairs of arms and like all other cephalopods, they naturally are bilaterally symmetrical. An octopus has got a beak that is hard, and its mouth is at the center point of its arms. Octopuses usually have got no skeleton at all, whether internal or external (though there are some species that have got vestigial remnant that looks like a shell inside of their mantles) which allows them to squeeze through places that are tight. Octopuses are some of the most behaviorally flexible and intelligent of all the invertebrates. Octopuses are inhabitants of several diverse regions in the ocean, which include pelagic waters, coral reefs and the floor of the ocean. Octopuses have got several strategies of defense against their predators, which include using camouflage, expulsion of ink and other deimitic displays Octopuses are known to be very intelligent, possibly more than any other invertebrates order. Biologists all over the world have debated on the octopus learning capability and their extent of intelligence. However problem-solving and maze experiments have indicated evidence of memory systems that are able to store memories that are both short and long-term. Octopuses do not have brains however researchers who have studied octopuses and put them through tests and mazes claim that octopuses are some of the most canny sea creatures. Octopuses can be taught almost any trick with a little imagination. A certain agricultural expert of German origin in Samoa became interested by the octopus flexibility. He wondered how an octopus could slither through a small hole. He built an aquarium and divided it by use of a clear plastic sheet. He connected the two halves of the aquarium with a glass tube. He then placed an octopus in one tank and a crab on the other. Immediately the octopus saw the crab, it ran its tentacles over the Plexiglas barrier, found out the glass tube and quickly slid via the tube to catch the crab. The researcher again got a smaller tube and for the second time, the octopus never wasted its time fiddling around and immediately slithered via the glass tube. The researcher later on put a third plastic barrier with a smaller tube and for the third time, the octopus slid through. Then another smaller hole till the time the hole was as tiny as the octopus’ eye diameter. So where does the octopus store its memory? Some of its memories are genetic and are recorded in big advanced DNA molecules that are found in each octopus cell. These communicate to the cells how to travel from each egg cell fertilized to the billions of other cells that form and thus are an octopus. They thus store crucial memories about the way a young octopus should swim, crawl, communicate with numerous rainbows on its skin ,disguise itself, lay eggs, reproduce and protection. Octopus behavior is therefore mediated by a brain that is highly centralized and developed, whereby the vertical lobe (VL) is highly involved in the process of memory band learning. If the VL is removed, the capability to learn new roles and tasks and recall of long-term memory is severely impaired. Removal of the VL leads to the impairment of the unique ability of the octopus to be able to learn a new task by previously watching a trained octopus that demonstrates how to perform a task (Hochner, Brown, Langella, 2003) Neurological development The vertical lobe is composed of two types of neurons that are morphologically identified, which approximate to 25 million small amacrine interneurons that usually synapse onto approximately 65,000 big efferent cells (Hochner, Brown, Langella, 2003).Young made a suggestion claiming that the connections of these neurons and the over 1.8 million afferents of the medial superior frontal lobe forms an association matrix which is analogous to the vertebrate hippocampus. The octopus’ neural processes thus have got amazing learning abilities.Octopuses have got highly advanced nervous system, of which only a part is contained inside its brain. Almost two-thirds of the neurons of an octopus are contained in the nerve cords located in its arms, which is very limited in terms of functional autonomy. The arms of the octopus exhibit various complicated reflex actions that remain persistence even if they have no input at all from the brain. It’s not exactly known what precise contribution learning has to the behavior of adult octopuses. Young octopuses do not learn any behavior patterns at all from their parents, since they have very little contact with them. Memory patterns and neurological development in Nautilus Nautilus just like the octopus belongs to the class of Cephalopoda and subclass Nautiloidea.Nautilidae; both extinct and extant have got involute shells which are generally smooth, with depressed or compressed whorl sections. Nautiluses are closely related to the very first cephalopods that appeared around 500 million years ago, earlier than modern cephalopods that came into existence around 100 million years afterwards. Nautiluses have got a simple brain, unlike the large complicated brains of cuttlefish, squid and octopus, and for a very long time had been assumed to have no intelligence. Nautiluses have got some of the simplest brains of extant cephalopods and the lack of dedicated memory and learning regions may point an existing ancestral condition. The absence of these two regions is assumed to limit memory recall and storage in nautilus. However there has never been any testing on this. Researchers Robyn and Jennifer, using a Pavlovian conditioning paradigm demonstrated that chambered nautilus can exhibit separated long and short-term memory storage, which produces a biphasic memory curve that is similar to cuttlefishes’. These researchers observed that there was persistence of short-term memory for just less than an hour after training, whereas long-term memory was exhibited between the sixth and twenty-fourth hour after training. They found out recovery of long-term at the sixth hour post-extinction. Inspite of lacking dedicated neurological regions that aid memory and learning in all extant cephalopods, the expression of memory in nautilus was the same to coleoids’.It seems therefore that the lack of these dedicated parts in the nautilus brain doesn’t appear to limit in any way the expression of memory as hypothesized (Saunders, Landman, 2010) The Nautilus’ Central nervous system (CNS) is very similar in its overall structure to that CNS of coleoid, however its considerably simpler and normally reflects the much reliance on olfactory instead of visual processing. The main thirteen lobes are not distinctively differentiated from the tissue that is surrounding and there seems to be small specialization. The sub-frontal and vertical lobes, parts of the brain which have been concerned in visual and tactile memory and learning in coleoids are completely missing from the CNS of nautilus. Some evidence exists that claims that the simple structure of the nautilus brain could be a representation of ancestral condition. Identification of structures in the brain of the nautilus that are analogously functional to the subfrontal and the vertical parts of the coleoid’s brain would be able to understand the evolution of specific memory structures together with their function in the development of the coleoid cephalopods. Collection of behavioral evidence of memory and learning is a crucial foremost step towards a more focused neurobiological manipulation in identification of the various memory storage sites in nautilus (Saunders, Landman, 2010). Memory and learning are well established in coleoids-octopuses and cuttlefish have resulted in a wealth of useful information regarding physiological bases of the memory of invertebrates and have illustrated amazing learning abilities. By contrast, however, there has been an overlooking of nautilus in behavioral studies. There has been no established procedure for testing or training nautilus. The nautilus does not have any stereotypic sequence of attack like several coleoids and does not have a strong exploratory force in captivity, thus making established methods that make use of these tendencies in experiments involving other cephalopods to be unsuitable (Saunders, Landman, 2010) A study done in 2008 about nautiluses (N.pompilius) were provided with food and a bright light which was blue in colour, until they started associating food with the light, and extending their tentacles each time the light was flashed. The light was flashed again without food 3 minutes, half an hour, one hour, six hours, twelve hours and twenty four hours afterwards. The nautiluses responded excitedly to the light for 30 minutes post-experiment and did not react any more after one hour. The researchers made a conclusion that nautiluses also had capabilities in memory just like the long and short-term memories of more developed cephalopods, inspite of having various brain structures. However the long term memory abilities of nautiluses are much shorter and limited compared to other cephalopods. The nautiluses forgot completely their earlier training after twenty four hours later as compared to octopuses, which can recall conditioning several weeks later. However the nervous system of the cephalopod is very different from that other invertebrates and animals. Experiments carried out recently have discovered it’s not only memory but also a response that is changing to similar event over time (Hochner, Brown, Langella, 2003) Work cited David, Sweatt. Mechanisms of Memory. London: Academic Press, 2010. Hanlon T. Roger, Messenger B.John. Cephalopod Behaviour. London: Cambridge University Press, 1996. Hochner Binyamin, Brown R. Euan,Langella Marina. "A Learning and Memory Area in the Octopus Brain Manifests a Vertebrate-Like Long-Term Potentiation." American Physiological Society (2003): Vol 90 no 3547-3554. Saunders Bruce, Landman H. Neil. Nautilus:The Biology and Paleobiology of a Living Fossil. New York: Springer, 2010. http://www.this-magic-sea.com/MEMORY2.HTM Read More