Cephalopods: Difference between revisions

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== Reproduction and Life Cycle ==
== Reproduction and Life Cycle ==
'''Reproduction'''
'''Reproduction'''
Cephalopods most frequently mate only once, which occurs near the end of their life cycle. <ref name="UMD"></ref> Courtship rituals between cephalopods can include a diverse array of color changes and body movements. Male cephalopods have a specialized arm (called a hectocotylus) which is used to transfer spermataphores, or packets of sperm, into the female's genital pore. Sometimes after mating, the hectocotylus is left behind in the female's mantle cavity. Females possess a single oviduct. <ref name="ADW"></ref> Females may mate with multiple males and have multiple paternity of offspring, ultimately increasing the genetic diversity of a population. <ref name="EOS"></ref>
Cephalopods most frequently mate only once, which occurs near the end of their life cycle. <ref name="UMD"></ref> Courtship rituals between cephalopods can include a diverse array of color changes and body movements. Male cephalopods have a specialized arm (called a hectocotylus) which is used to transfer spermataphores, or packets of sperm, into the female's genital pore. Sometimes after mating, the hectocotylus is left behind in the female's mantle cavity. Females possess a single oviduct. <ref name="ADW"></ref> Females may mate with multiple males and have multiple paternity of offspring, ultimately increasing the genetic diversity of a population. <ref name="EOS"></ref>


Revision as of 21:19, 12 April 2014

Cephalopods

  • All are molluscs [1]
  • Class Cephalopoda [2]
    • Includes octopuses, cuttlefish, squid, etc[2]
    • Present in all the world's oceans [2]

Evolution

  • Probably evolved from gastropods [3]
  • More than 10,000 fossil species named [3]
  • Belemnoids, from the Mesozoic, may be the ancestors of modern squids [3]
  • 800 extant species [4]

Reproduction and Life Cycle

Reproduction

Cephalopods most frequently mate only once, which occurs near the end of their life cycle. [5] Courtship rituals between cephalopods can include a diverse array of color changes and body movements. Male cephalopods have a specialized arm (called a hectocotylus) which is used to transfer spermataphores, or packets of sperm, into the female's genital pore. Sometimes after mating, the hectocotylus is left behind in the female's mantle cavity. Females possess a single oviduct. [3] Females may mate with multiple males and have multiple paternity of offspring, ultimately increasing the genetic diversity of a population. [2]

Life Cycle

    • Eggs are covered in a touch coating that attach to hard surfaces [2]
      • Hatch directly into "paralarvae," which are essentially mini adults, but may occupy different ecological niches than adults [2]
      • Some octopuses stay with eggs and guard them while others spawn in open water [2]
  • No true larval stage [3]
  • Large eggs hatch as paralarvae [2]
  • Adult size reached in about one year [2]
    • Sexual maturation occurs rapidly [2]
    • Most individuals die shortly after mating once [2]
    • Uniseasonal breeding [2]
      • Can cause considerable seasonal fluctuations in population [2]
        • These fluctuations are highly variable and inconsistently patterned

Anatomy

  • Buccal cavity [3]
  • Radula [3]
    • Coarse, rasping tongue [1]
  • Ink gland [3]
  • All but the family Nautilus have cells containing large amounts of pigment and contractile fibers [3]
    • This is what enables the animals to change colors [3]
      • Frequently occurs in response to danger or emotion
  • Can distinguish shapes with highly evolved sensory system
  • Have reduced or absent calcareous shells [2]
  • Squids and octopuses have lost the internal shell and its buoyancy functions [2]
  • Brain
    • Ganglionic masses centered around the esophagus [2]
  • Well developed statocysts (gravity and movement senses) [2]
  • Skin
    • Delicate epithelial tissue over layers of connective tissue [2]
    • Chromatophores [2]

Diet

  • Carnivorous [3]
    • Feed on wide range of crustacea and fish[2]
    • Eat approximately 1.5 and 15% of body weight daily [2]
    • Some exhibit cannibalism on smaller members of their [2]respective species [2]
    • Prey are usually attacked with a forward strike and subsequently pulled toward the mouth with tentacles [2]
    • Squid bite their prey with their beaks [2]
    • Octopuses have a more complicated means of consuming their prey [2]
      • Secretion of toxins/enzymes is injected into the prey [2]
        • Makes the flesh easier to extract from crustaceans [2]

Behavior

  • Rapid color change [4]
    • Most frequently used for crypsis (camouflage), mating displays, and prey/predator response[2]
      • Great evolutionary significance [2]
  • Centralized brain with highly developed sense organs [4]
  • Jet propulsion [3]
    • Using the muscular mantle to force water through the ventral funnel [2]
    • Coastal octopuses are more benthic in nature [2]
      • Use their arms to move around the ocean floor, only occasionally employing jet propulsion [2]
  • Inking [2]

Habitat

Importance

Economic value

  • Many species are eaten by humans[3]
    • This goes back as far as classical times [2]
    • As many as 3 million tonnes are consumed annually by humans [2]
    • Commercial harvest has increased from about 1 million tonnes to 3 million tonnes from the 1970s-1990s

Ecological value

  • Important to food chain [2]
    • Eat a wide variety of fish, crustaceans, and other invertebrates [2]
    • Preyed upon by fish, marine mammals, and oceanic birds [2]
      • Cephalopod remains are often found in the guts of large fish, seals, whales, and birds [2]
        • Sperm whales may consume up to 320 X 10^6t of cephalopods from open ocean areas [2]

Threats

Human Induced Threats [5]

  • Bioaccumulation of toxins [5]
  • Noise pollution [5]
  • Altered seasonal migration patterns related to ocean warming [5]
  • Possible decrease in availability of calcium carbonate, related to declining pH [5]
  • Overfishing [5]

Species

Common Octopus Octopus vulgaris

Lifespan of 12-24 months [6]

  • Geographic Range
    • Found all over the world, including the Eastern Atlantic Ocean [6]
  • Habitat
    • Tropical/subtropical and temperate waters [6]
    • Abundance at continental shelf is nearly zero; found almost exclusively in shallow waters [6]
    • Frequents depths of 100-150m [6]
    • Primarily found in coastal waters and the upper continental shelf [6]
  • Physical Appearance
    • Reaching 1-3ft [6]
    • Smooth skin [6]
  • Reproduction and Development
    • Eggs laid in shallow water [6]
    • Females brood in isolation
  • Behavior and Diet
    • Solitary and territorial [6]
    • Sedentary, leaving dens to hunt at night [6]
    • Nocturnal [6]
    • Feed primarily on gastropods and bivalves [6]
    • Paralarvae consume plankton, but switch to adult diet upon reach a size of approximately 0.2g [6]
  • Conservation Status
    • Potential for overfishing [6]

Caribbean Reef Octopus Octopus briareus [7]

  • Geographic Range
    • Warm, shallow water [7]
  • Habitat
    • Shallow waters of coral reefs [7]
    • Often reside near rocks and seagrass [7]
    • Quite reclusive [7]
  • Physical Appearance
    • 8 arms varying in length/diameter [7]
      • Relatively thin [7]
    • Change colors between browns, reds, and greens/blues [7]
    • Minimal sexual dimorphism [7]
  • Reproduction and Development
    • Males have a hectocotylus [7]
    • Males initiate mating, which usually lasts between 30 and 80 minutes [7]
    • Females can store sperm in oviducts for more than 3 months [7]
    • Females brood multiple egg clusters of about 25, totaling anywhere between 100-500 eggs [7]
      • Takes 50-80 days, but is accelerated in warmer waters [7]
    • Hatch as miniature adults, capable of swimming, eating, inking, and changing color as adults can [7]
    • Males reach sexual maturity around 140 days; females, 150 [7]
  • Behavior and Diet
    • Not social [7]
    • Fighting occurs over living territory [7]
      • Standard distance between living spaces is approximately 60ft [7]
    • Frequently change dens, only remaining in one place while brooding [7]
    • As a predatory defense, these octopuses swell their mantle with water before jet-propelling themselves away behind a cloud of ink [7]
    • Eat mostly crab (preferred) and shrimp [7]
      • May eat fish and lobsters as well [7]
    • Hunt in early morning and evening hours [7]
  • Conservation Status
    • No current threat [7]

Caribbean Two-Spot Octopus [8]

  • Geographic Range
    • Found often in the Bahamas, Caribbean, and Florida[8]
  • Habitat
  • Physical Appearance
    • Mottled appearance
    • Blue rings make ocelli beneath the eyes
  • Reproduction and Development
  • Behavior and Diet
  • Conservation Status

Caribbean Reef Squid Sepioteuthis sepioidea [9]

Important as a food source for humans

  • Geographic Range
    • Found all throughout the Caribbean [9]
  • Habitat
    • Newly hatched organisms live very close to shore [9]
      • Found anywhere between .2-10m deep and frequently near vegetation [9]
    • Older specimens are denizens of turtle grass in the shallows near shore [9]
      • Often stay as many as two meters deep to avoid predation from birds [9]
      • Similarly, they avoid the ocean floor to stay away from other predators [9]
      • At night, they swim to deeper water and hunt [9]
    • Non-breeding adults prefer open water, enjoying ample space in depths of up to 100m at night [9]
    • Breeding adults spend their time in coral reefs, reaching depths of no greater than 8m [9]
  • Physical Appearance
    • Adults resemble cuttlefish [9]
    • Less elongated/arrow-shaped and streamlined than other species of squid [9]
    • Females are slightly larger than males [9]
    • Mottled with browns and whites and tans [9]
    • White line running longitudinally on dorsal side [9]
    • Brow ridges above eyes [9]
  • Reproduction and Development
    • Individuals die after reproducing once [9]
    • Females die immediately after laying eggs [9]
    • Males can mate many times in a small window of time before death [9]
    • Females do not care for young [9]
  • Behavior and Diet
    • Highly social [9]
      • Complex signal communication [9]
    • Can change the color of their brow ridges and central arms to express alarm [9]
    • Can eject ink in open water as a means of evading predation [9]
    • At rest, individuals may adopt a red or brown color [9]
    • Younger squid often display bars that make them more closely resemble vegetation, presumably a defense mechanism [9]
    • Primarily consume sardines and other fish [9]
      • Sometimes shrimp [9]
    • Hunting is dependent on vision[9]
  • Conservation Status
    • No special status [9]

Notes

  1. ↑ 1.0 1.1 Judkins, Heather L. "Cephalopods of the Broad Caribbean: Distrution, Abundance, and Ecological Importance." Diss. University of South Florida, 2009. Scholar Commons. Graduate School at Scholar Commons. Web. 21 Feb. 2014. <http://scholarcommons.usf.edu/cgi/viewcontent.cgi?article=3033&context=etd&sei-redir=1&referer=http%3A%2F%2Fwww.google.com%2Furl%3Fq%3Dhttp%253A%252F%252Fscholarcommons.usf.edu%252Fcgi%252Fviewcontent.cgi%253Farticle%253D3033%2526context%253Detd%26sa%3DD%26sntz%3D1%26usg%3DAFQjCNF6Q0NU3If5jMRKW7UQ1KtCo117qQ#search=%22http%3A%2F%2Fscholarcommons.usf.edu%2Fcgi%2Fviewcontent.cgi%3Farticle%3D3033%26context%3Detd%22>.
  2. ↑ 2.00 2.01 2.02 2.03 2.04 2.05 2.06 2.07 2.08 2.09 2.10 2.11 2.12 2.13 2.14 2.15 2.16 2.17 2.18 2.19 2.20 2.21 2.22 2.23 2.24 2.25 2.26 2.27 2.28 2.29 2.30 2.31 2.32 2.33 2.34 2.35 2.36 2.37 2.38 2.39 2.40 Boyle, P. "Cephalopods." Encyclopedia of Ocean Sciences 1 (2001): 436-42. Science Direct. Elsevier B.V., 11 Apr. 2013. Web. 22 Feb. 2014. <http://ac.els-cdn.com/B9780123744739001958/3-s2.0-B9780123744739001958-main.pdf?_tid=4e6f9af6-9e64-11e3-bd04-00000aacb360&acdnat=1393364120_b8c509396a239367521c18e75d90ee5a>.
  3. ↑ 3.00 3.01 3.02 3.03 3.04 3.05 3.06 3.07 3.08 3.09 3.10 3.11 3.12 Wheeler, Kristen, and Daphne G. Fautin. "ADW: Cephalopoda: INFORMATION." Animal Diversity Web. Regenst of the University of Michigan, 2001. Web. 22 Feb. 2014. <http://animaldiversity.ummz.umich.edu/accounts/Cephalopoda/>.
  4. ↑ 4.0 4.1 4.2 Jann, Vendetti. "The Cephalopoda." University of California Museum of Paleontology. UC Berkeley, n.d. Web. 24 Feb. 2014. <http://www.ucmp.berkeley.edu/taxa/inverts/mollusca/cephalopoda.php>
  5. ↑ 5.0 5.1 5.2 5.3 5.4 5.5 5.6 LaRosa, Ginni A.. "Learning from the Soft Intelligence: Cephalopods as Indicators of Ocean Changes." UMD Library. University of Maryland, 01 Dec 2011. Web. 25 Feb 2014. <http://drum.lib.umd.edu/bitstream/1903/12427/11/LaRosa_ResearchPaper.pdf>.
  6. ↑ 6.00 6.01 6.02 6.03 6.04 6.05 6.06 6.07 6.08 6.09 6.10 6.11 6.12 6.13 6.14 Case, R. 1999. "Octopus vulgaris" (On-line), Animal Diversity Web. Accessed February 25, 2014 at http://animaldiversity.ummz.umich.edu/accounts/Octopus_vulgaris/
  7. ↑ 7.00 7.01 7.02 7.03 7.04 7.05 7.06 7.07 7.08 7.09 7.10 7.11 7.12 7.13 7.14 7.15 7.16 7.17 7.18 7.19 7.20 7.21 7.22 7.23 7.24 Robinson, A. 2000. "Octopus briareus" (On-line), Animal Diversity Web. Accessed February 25, 2014 at http://animaldiversity.ummz.umich.edu/accounts/Octopus_briareus/
  8. ↑ 8.0 8.1 Tokarz, Jessica. " Caribbean Two-Spot Octopus." Field guide to marine inhabitants - Invertebrates. Marine Science Center of Florida. Web. 25 Feb 2014. <http://www.marinesciencecenter.com/Octopodidae.htm>.
  9. ↑ 9.00 9.01 9.02 9.03 9.04 9.05 9.06 9.07 9.08 9.09 9.10 9.11 9.12 9.13 9.14 9.15 9.16 9.17 9.18 9.19 9.20 9.21 9.22 9.23 9.24 9.25 9.26 9.27 9.28 9.29 Ritter, S. 2000. "Sepioteuthis sepioidea" (On-line), Animal Diversity Web. Accessed February 25, 2014 at http://animaldiversity.ummz.umich.edu/accounts/Sepioteuthis_sepioidea/
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