Lecture 10: Cephalopods to Arthropods

• Cephalopods are part of the phylum mollusca
• Cephalopods include the nautilus, cuttlefish, squid, and octopus
• Cephalopods have a highly evolved nervous system, good vision, and are efficient carnivores
• Squid use jet propulsion to move
• The cuttlefish uses the cuttlebone for help with buoyancy

  Once ideal gas volume is reached, alter ion concentration of fluid in cuttlebone such that osmotic pressure = hydrostatic pressure to maintain conditions
• Cephalopods use an inking mechanism in order to serve as a distraction
• Adaptive coloration achieved through Chromatophores, Reflective Cells, and Skin Papillae
• Chromatophores are sacs of pigment with radial muscles that are involved with the lower motor centers of the brain
• Reflecting cells are either Iridophores (reflect greens, blues, golds, silvers) or Leucophores (white spots)
• Skin papillae change the texture of the skin
• Three types of adaptive coloration:

  Uniform

  Mottle

  Disruptive
• Uniform coloration has minimal variation in contrast
• Mottle coloration have small-scale light and dark patches and some repetition of pattern
• Disruptive coloration have light and dark patches of varying shapes and high contrast patterns
• Muscular hydrostats are 3-D arrays of muscles that act as both compressive and tensile elements

  Produce 4 main types of movement: elongation, shortening, bending, torsion
• Muscular Hydrostats:

  Large L/D ratio means greater length/speed changes for a given diameter

  Small L/D ration means greater force to a given diameter
• Cephalopod tentacles have a large L/D ratio, while their arms have a short L/D ratio
• Cephalopoda reproduction includes male transfer of a spermatophore to the female

  Females often incubate their eggs until they hatch
• Arthropods include Chelicerates, Mandibulates
• Chelicerates have movable claws near their mouth and lack "chewing" mouthparts
• Mandibulates have mandibles that are used for chewing food
• Crustaceans are the largest marine arthropod group with the second highest number of marine species
• Crustaceans in the order Decapod include crabs, lobsters, and shrimp
• The order Stomatopoda in Crustacea includes the mantis shrimp