Non-arthropods

• Porifera

  • Sedentary animals that lack tissues or organs
  • Their "bodies" consist of 4 primary cell types arranged in loose aggregates around a system of pores and canals through which sponges pass water
• Water flow in sponges

  1. Water enters through pores on the body surface called ostia

  2. Water passes through a complex series of chambers and canals and is stripped of most food particles and oxygen

  3. Specialized cells called choanocytes lining the interior surface of the radial canals trap small food particles

  4. The flagella of the choanocytes cause water to move through the sponge's body

  5. Water is pushed out of the large osculum usually located at the top of the sponge
• Cnidaria


  • Phylum composed of four major classes of mostly marine carnivores: Hydrozoa, Scyphozoa, Cubozoa and Anthozoa
  • All cnidarians are radially symmetrical
  • Unique characteristic is the presence of tentacles armed with stinging cells called cnidocytes used for defense and capturing food
• Cnidarian alternation of generations

  • Alternation between polyp and medusa body forms, both of which are diploid
  • The only haploid stage is the gametes
• Cnidarian classes


  • Hydrozoans (polyp form predominates, medusa is short-lived)
  • Scyphozoans (medusa form predominates, polyp is short-lived)
  • Cubozoans (medusa dominates, have two types of eyes)
  • Anthozoans (only polyp form, medusa completely lost)
• Cnidarian body structure


  • Arranged into two discrete tissue layers, an outer epidermis and an inner gastrodermis
  • Sandwiched between these two layers is an inert, gelatinous substance called mesoglea
• Hydrozoan anatomy


  • Polyp is the predominant body form, often assembled into colonies
  • Hydra exist as single, mobile polyps that reproduce sexually or asexually
• Solitary hydrozoans


  • Hydra
• Colonial hydrozoans


  • Obelia
• Obelia colony


  • Numerous interdependent polyps that form from repeated asexual budding of a single individual, so they are genetically identical
  • Includes feeding polyps (hydranths) and reproductive polyps (gonangia)
• Obelia medusa


  • Short-lived stage devoted primarily to reproduction
  • Releases haploid sperm and eggs which fuse to form a diploid zygote that develops into a swimming planula larva
• Scyphozoa


  • Medusa stage dominates the life cycle, polyp stage is an inconspicuous, short-lived larval form
• Anthozoa


  • Polyp stage is emphasized, medusa stage has been completely lost
  • Polyps perform both sexual and asexual reproduction
• Anthozoan anatomy


  • Diverse forms achieved with the simple polyp body plan
  • Many form mutualistic interactions with single-celled algae called zooxanthellae
• Coral reefs


  • Formed by the tiny deposits of Calcium Carbonate that individual coral polyps use to cement themselves to the substrate
  • Provide habitat for a huge diversity of marine life
  • Among the most productive and diverse marine habitats
• Cubozoa


  • Generally follow the anatomy of the scyphozoan but have a cuboidal rather than spherical shape
  • Have more developed eyes, including image forming camera-lens eyes
  • Are generally strong swimmers and better at directing their movement than scyphozoans
  • Polyp stage is extremely reduced
• Zooxanthellae


  Microscopic algae that live symbiotically within the tissues of some marine invertebrates, including corals
• Corals


  • They form large coral reefs that provide habitat for a huge diversity of marine life
  • Coral reefs are formed by the tiny deposits of Calcium Carbonate that individual coral polyps use to cement themselves to the substrate
  • These deposits build up over thousands of years to form coral reefs
  • With the combination of structure and energy provided by corals with their zooxanthellae, Coral reefs are among the most productive and diverse marine habitats
• Cubozoa


  A class of Cnidarians that generally follow the anatomy of the scyphozoan but have a cuboidal rather than spherical shape, more developed eyes including image forming camera-lens eyes, and are generally strong swimmers and better at directing their movement than scyphozoans
• The polyp stage in Cubozoans is extremely reduced, and is unknown in many forms, possibly it has been lost entirely, just as the medusa stage has been in the Anthozoa
• Box jellies (Cubozoans)


  They are notorious for the strength of the venom in their Cnidocytes, with the Australian box jelly, Chironex fleckeri, being the most venomous marine animal
• By the end of your examination of Cnidarians you should be able to

  • Identify a specimen of the Cnidaria in either the polyp or medusa form
  • Distinguish between a polyp and medusa and explain the difference between them
  • Explain the life cycle of cnidarians
  • Identify the structures in the text in slides or diagrams
  • Explain zooxanthellae and the formation of coral reefs
• Triploblastic animals


  Animals containing three layers of tissue
• Body plans of triploblastic animals

  • Acoelomate - animals whose central space is filled with tissue (mesoderm), no true body cavity
  • Pseudocoelomate - animals with a central body cavity that lies between the endoderm and mesoderm
  • Coelomate - animals with a central body cavity that lies within mesoderm
• The gut (or digestive cavity) does not count as a body cavity when determining the type of coelom that an animal possesses. All triploblastic animals possess a digestive cavity.
• Platyhelminthes


  The flatworms, an estimated 15,000 species ranging in size from a few millimeters to over 20 meters long, but never more than a few millimeters thick
• Flatworms


  • Possess a third tissue layer called mesoderm sandwiched between the ectoderm and endoderm, making them one of the first highly motile groups of animals
  • Have bilateral symmetry and free-living species typically possess a concentration of nervous tissue and sensory structures at the cranial end of the body (cephalization)
  • Possess extensive organ development and display several organ systems
• Turbellaria


  The free-living flatworms that typically inhabit freshwater streams and ponds, oceans, and moist terrestrial environments
• Planaria (Turbellaria)


  • Have a conglomeration of sensory structures including eyespots and auricles at the cranial end
  • Have a highly branched gastrovascular cavity (intestine) that spreads throughout the entire body to minimize the distance for nutrients to diffuse
  • Have a muscularized pharynx that is extended from its sheath in the body for feeding
  • Have a simple excretory system consisting of flame cells and a branching network of tubules
• Trematoda


  The parasitic flatworms commonly referred to as flukes, with complex lifecycles involving several host species
• Flukes (Trematoda)


  • Possess suckers for attachment to the host's inner body wall or organs
  • Are surrounded by a thin, protective cuticle that prevents the digestive enzymes of the host from digesting them
  • Produce thousands of eggs a day for many years to complete their lifecycle
• Cestoda


  The tapeworms, the most specialized group of parasitic flatworms
• Tapeworms (Cestoda)


  • Completely lack a mouth and gastrovascular cavity, absorbing nutrients directly via diffusion through the cuticle of each proglottid
  • Have a scolex (head) modified for attachment to the host with hooks and suckers
  • Grow by producing new proglottids behind the scolex, with mature proglottids containing fertilized eggs dropping off the tapeworm to be passed out of the host
• When you finish examining the Platyhelminthes, you should be able to

  • Identify a given specimen, slide, or diagram as a platyhelminth
  • Distinguish between Turbellaria, Trematoda, and Cestoda
  • Identify the traits listed in bold throughout the lab, including their functions
  • Explain the difference between free-living and parasitic lifestyles
  • Be able to read a life cycle diagram for a parasite with a complex life cycle such as Fasciola hepatica
• Nematoda


  The phylum of roundworms, a mixture of free-living and parasitic members, with nearly 20,000 described species and an estimated 4-50 times that number in existence
• Nematodes


  • Possess a pseudocoelom, a body cavity that lies between a layer of mesoderm and a layer of gastrodermis
  • Have a complete digestive tract containing both a mouth and an anus
  • Have unsegmented, tapered, tubular bodies devoid of appendages and covered by a thin cuticle
  • Have a finite number of cells in their body that is species-specific
• Nematodes are so numerous that if you were to remove everything else from the environment, the remaining nematodes would form a ghostly skeleton outlining the entire terrestrial biosphere
• Nematodes


  • Possess a pseudocoelom, a body cavity that lies between a layer of mesoderm and a layer of gastrodermis
  • Have a complete digestive tract containing both a mouth and an anus
• Nematodes tend to display more similarities than differences among the numerous species
• Nematode body


  • Unsegmented, tapered, tubular, devoid of appendages, covered by a thin cuticle secreted by the epidermis