Marine Biology PDF

Class Cubozoa: Box Jellyfish  Class Cubozoa  Includes box jellies and sea wasps.  The medusa is box- shaped and has complex eyes.  Polyps are tiny and develop directly into medusae. the Box jelly fish Chironex fleckeri Class Anthozoa  Includes the corals and sea anemones which occur o...

Class Cubozoa: Box Jellyfish  Class Cubozoa  Includes box jellies and sea wasps.  The medusa is box- shaped and has complex eyes.  Polyps are tiny and develop directly into medusae. the Box jelly fish Chironex fleckeri Class Anthozoa  Includes the corals and sea anemones which occur only as polyps.  No medusa stage.  All marine  Solitary or colonial  Order Actinaria–Sea Anemones  Found in coastal waters all around the world.  Attach to rocks using their pedal disc.  Feed on fish or any other food of suitable size.  Sea anemones usually move by gliding slowly along on their pedal discs.  When a predator approaches, most withdraw.  Stomphia detaches its disc and “swims” away.  Tentacles arranged around the central mouth.  The gastrovascular cavity is divided into six radia chambers.  Increases the surface area of the gastrodermis. Mutualisms  Sea anemones sometimes harbor zooxanthellae (photosynthetic protists) like hard corals do.  Some crabs will decorate their shells with anemones. Mutualisms  Some damselfish (anemone fishes) form associations with large anemones.  Fish gains protection from living in the anemone.  The fish may help ventilate the anemone, or keep it free of sediment. Sea Anemones (with sea urchins) Sea Anemones Clown fish with sea anemone Giant Sea Anemone Clown fish & eggs with sea anemone Rosy Sea Anemone Order Scleractinia-Hexacorallian Corals  Hexacorallian corals are the true or stony corals.  Like tiny anemones living in calcareous cups. Hexacorallian Corals  Gastrovascular cavity subdivided by septa in multiples of six.  The calcium carbonate skeleton is secreted below living tissue. Hexacorallian Corals  Polyps may be retracted into the skeleton.  Often retracted during the day.  The polyps expand for feeding.  Order Ceriantipatharia Tube Anemones and Thorny Corals  Have coupled but unpaired septa.  Tube anemones  Solitary and live in soft sediments. Tube Anemones and Thorny Corals  Thorny or black corals  Colonial and attach to firm substrata.  Both groups have few species and live in warmer seas. Order Octocorallia-Octocorallian Corals  Have eight pinnate tentacles and eight septa. Octocorallian Corals  Sea fans, sea pens & sea pansies belong to this group.  Often beautifully colored.  Feeding A. Carnivores (predators) B. Process of feeding 1. Tentacles sting prey with nematocysts 2. Tentacles grab prey 3. Prey pulled into mouth Lion’s mane eats another jelly Process of feeding 4. Prey stuffed into gastro-vascular cavity (GVC)* 5. GVC makes enzymes, extra-cellular digestion 6. Undigested food back out mouth *incomplete digestive tract (no anus)  Feeding  Cnidarians are carnivores that use tentacles to capture prey.  The tentacles are armed with cnidocytes – unique cells that function in defense and the capture of prey.  Nematocysts contain toxins used for prey capture and defense.  Feeding  Nematocysts are used to inject a toxin.  Variable in form.  May be used for prey capture or defense. Discharged nematocyst  Feeding  Extracellular digestion begins in the gastrovascular cavity, but is completed within the cells of the gastrodermis.  Some cnidarians supplement their diet with nutrients collected from algal symbionts (zooxanthellae). Respiration and Excretion  Via diffusion  Body is two cell layers thick Response A. No cephalization or nervous system B. Nerve net around mouth C. Sensory cells 1. Chemoreceptors (chemicals) 2. Thigmoreceptors (touch) 3. Photoreceptors (light) Ocelli (eyespots) 4. Statocysts (balance) Nerve Net  Cnidarians have a diffuse nervous system.  Nerve cells forming two interconnected nerve nets in the epidermis and gastrodermis.  No concentrated grouping of nerve cells forming a central nervous system.  CNS does not provide advantage for radially symmetrical animals where stimuli approach from all sides. Locomotion A. Medusa motile, free-swimming B. Polyps sessile Exceptions: 1. Hydra tumbles on tentacles 2. Sea anemones glide on pedal disc Reproduction 1. Asexual budding from polyps or medusae Polyps can reproduce asexually by budding, fission. 2. Sexual a. Medusae release sperm & eggs b. Some monoecious, some dioecious c. Larvae free-swimming  Reproduction  Cnidarians, typically medusae, can also reproduce sexually.  A zygote usually develops into a motile planula larva.  Some species only exist as polyps, others only as medusae, others alternate between the two.  Class Scyphozoa – Typical Life Cycle  Planula larvae develop into a polyp-like form.  Saucer-like buds called ephyrae are produced by strobilation. Ecological Role A. Predators and prey B. Neurotoxins in medical research C. Coral – jewelry, building, reefs (surfing!) D. Coral reefs - habitat for many -great biodiversity - protect coastline E. Symbiosis with other organisms