Myers, Paul Zachary (29 October 2006). "Definitely not safe for work". Pharyngula . Retrieved 18 March 2017. The digestive system of the octopus begins with the buccal mass which consists of the mouth with its chitinous beak, the pharynx, radula and salivary glands. [46] The radula is a spiked, muscular tongue-like organ with multiple rows of tiny teeth. [30] Food is broken down and is forced into the oesophagus by two lateral extensions of the esophageal side walls in addition to the radula. From there it is transferred to the gastrointestinal tract, which is mostly suspended from the roof of the mantle cavity by numerous membranes. The tract consists of a crop, where the food is stored; a stomach, where food is ground down; a caecum where the now sludgy food is sorted into fluids and particles and which plays an important role in absorption; the digestive gland, where liver cells break down and absorb the fluid and become "brown bodies"; and the intestine, where the accumulated waste is turned into faecal ropes by secretions and blown out of the funnel via the rectum. [46] Wells, M. J. (1978). Octopus, Physiology and Behaviour of an Advanced Invertebrate. Springer Science+Business Media. ISBN 978-94-017-2470-8.

Some species differ in form from the typical octopus body shape. Basal species, the Cirrina, have stout gelatinous bodies with webbing that reaches near the tip of their arms, and two large fins above the eyes, supported by an internal shell. Fleshy papillae or cirri are found along the bottom of the arms, and the eyes are more developed. [37] [38] Circulatory systemLenz, Tiago M., et al. " First Description of the Eggs and Paralarvae of the Tropical Octopus, Octopus Insularis, under Culture Conditions." BioOne 33.1 (2015): 101-09. Print. Whether immortalised as giant monsters, fetishised in tentacle pornography or celebrated as psychic football pundits, octopuses have long fascinated humans. Fukuda, Y. 1987. Histology of the long digital tentacles. In: W.B. Saunders & N.H. Landman (eds.) Nautilus: The Biology and Paleobiology of a Living Fossil. Springer Netherlands. pp. 249–256. doi: 10.1007/978-90-481-3299-7_17 The eggs have large yolks; cleavage (division) is superficial and a germinal disc develops at the pole. During gastrulation, the margins of this grow down and surround the yolk, forming a yolk sac, which eventually forms part of the gut. The dorsal side of the disc grows upward and forms the embryo, with a shell gland on its dorsal surface, gills, mantle and eyes. The arms and funnel develop as part of the foot on the ventral side of the disc. The arms later migrate upward, coming to form a ring around the funnel and mouth. The yolk is gradually absorbed as the embryo develops. [26] Octopus paralarva, a planktonic hatchling

Bradbury H.E., Aldrich F.A. (1971). "The occurrence of morphological abnormalities in the oegopsid squid Illex illecebrosus (Lesueur, 1821)". Canadian Journal of Zoology. 49 (3): 377–379. doi: 10.1139/z71-055. PMID 5103494. a b c d "Finned Deep-sea Octopuses, Grimpoteuthis spp". MarineBio. 18 May 2017 . Retrieved 14 May 2021.

a b Carefoot, Thomas. "Octopuses and Relatives: Reproduction". A Snail's Odyssey. Archived from the original on 22 April 2017 . Retrieved 11 April 2017. The octopus is classified as a cephalopod, along with other animals like squid and cuttlefish. Cephalopod refers to animals who have limbs attached to their head. In this sense, the octopus is said to have eight tentacles. The eight limbs are commonly referred to as tentacles. Although now there are arguments on the fact whether all the limbs should be called tentacles or not. Zelman, I.; Titon, M.; Yekutieli, Y.; Hanassy, S.; Hochner, B.; Flash, T. (2013). "Kinematic decomposition and classification of octopus arm movements". Frontiers in Computational Neuroscience. 7: 60. doi: 10.3389/fncom.2013.00060. PMC 3662989. PMID 23745113.

In classical Greece, Aristotle (384–322 BC) commented on the colour-changing abilities of the octopus, both for camouflage and for signalling, in his Historia animalium: "The octopus... seeks its prey by so changing its colour as to render it like the colour of the stones adjacent to it; it does so also when alarmed." [165] Aristotle noted that the octopus had a hectocotyl arm and suggested it might be used in sexual reproduction. This claim was widely disbelieved until the 19th century. It was described in 1829 by the French zoologist Georges Cuvier, who supposed it to be a parasitic worm, naming it as a new species, Hectocotylus octopodis. [166] [167] Other zoologists thought it a spermatophore; the German zoologist Heinrich Müller believed it was "designed" to detach during copulation. In 1856 the Danish zoologist Japetus Steenstrup demonstrated that it is used to transfer sperm, and only rarely detaches. [168] Flexible biomimetic 'Octopus' robotics arm. The BioRobotics Institute, Scuola Superiore Sant'Anna, Pisa, 2011 [169] Chung, Wen-Sung; Kurniawan, Nyoman D.; Marshall, N. Justin (2021-11-18). "Comparative brain structure and visual processing in octopus from different habitats". Current Biology. 32 (1): 97–110.e4. doi: 10.1016/j.cub.2021.10.070. ISSN 0960-9822. PMID 34798049. S2CID 244398601. Wodinsky, Jerome (1969). "Penetration of the Shell and Feeding on Gastropods by Octopus" (PDF). American Zoologist. 9 (3): 997–1010. doi: 10.1093/icb/9.3.997.

Kawamura, G.; etal. (2001). "Color Discrimination Conditioning in Two Octopus Octopus aegina and O. vulgaris". Nippon Suisan Gakkaishi. 67 (1): 35–39. doi: 10.2331/suisan.67.35. If you can buy boiled tender octopus tentacles, you can skip the instructions for boiling octopus. I bought a fresh whole octopus that weighed about 1kg. Katz, Itamar; Shomrat, Tal; Nesher, Nir (1 January 2021). "Feel the light – sight independent negative phototactic response in octopus' arms". Journal of Experimental Biology. 224 (5). doi: 10.1242/jeb.237529. ISSN 0022-0949. PMID 33536305. Kidadl provides inspiration to entertain and educate your children. We recognise that not all activities and ideas are appropriate and suitable for all children and families or in all circumstances. Our recommended activities are based on age but these are a guide. We recommend that these ideas are used as inspiration, that ideas are undertaken with appropriate adult supervision, and that each adult uses their own discretion and knowledge of their children to consider the safety and suitability. Kennedy, E. B. Lane; Buresch, Kendra C.; Boinapally, Preethi; Hanlon, Roger T. (2020). "Octopus arms exhibit exceptional flexibility". Scientific Reports. 10 (1): 20872. doi: 10.1038/s41598-020-77873-7. PMC 7704652. PMID 33257824.