Bio1151 Chapter 33 Invertebrates
  1. Invertebrates do not have a           , and account for 95% of known animal species.

    A Christmas tree worm is a marine invertebrate, Phylum Annelida.

    Except for sponges (phyla Calcarea and Silicea), all animals belong in Eumetazoa and have tissues. Most Eumetazoa exhibit bilateral symmetry and are classified in Bilateria. Invertebrates are a paraphyletic group that includes all animals except a clade of deuterostomes called chordates.
  2. Phyla           and          are the multicellular sponges (formerly Porifera) that lack true tissues.

    Sponges contain spicules made of either calcium carbonate (Calcarea) or silica (Silicea) that provide support.

    They lack tissues; there are a few specialized cell types.

  3. Epidermal cells form a outer layer called the epidermis.
  4. Porocytes allow water to enter a cavity (spongocoel) and out via the Osculum.
  5. Choanocytes use flagella to move water and engulf food by phagocytosis.
  6. Amoebocytes transport nutrients to other cells and also secrete the spicules.

    Fertilization is external:

  7. Phylum           belongs in the clade with true tissues called            .

    Phylum Cnidaria.

    Cnidarians are diploblastic and may exist in polyp and medusa stages in their life cycle.

    Tentacles are armed with cnidocytes to capture prey.

  8. class Hydrozoa
  9. class Scyphozoa
  10. class Cubozoa
  11. class Anthozoa

      Cnidaria exhibit a radial symmetry that can take the form of a sessile polyp or a swimming medusa.

      The gastrodermis lines a gastrovascular cavity for digestion; a single opening to this cavity functions as both mouth and anus. A gelatinous mesoglea is sandwiched between the epidermis and gastrodermis.

      The life cycle of the Cnidarian Obelia alternates between a sessile polyp stage and a swimming medusa stage. Do not confuse this with the alternation of generations in plants in which the haploid and diploid generations are both multicellular. In animals, only the unicellular gametes are haploid.

      A cnidocyte is a specialized cell containing a stinging capsule called nematocyst. When the "trigger" in the nematocyst is stimulated by touch or by chemicals, a coiled thread shoots out, puncturing and injecting poison into prey.

      Phylum Cnidaria, Class Hydrozoa.

      Both medusa and polyp stages present; the polyps are often colonial.

      Hydra eating (polyp):

      Portuguese man-of-war (medusa):

      Phylum Cnidaria, Class Scyphozoa.

      Jellies,\ and sea nettles have free-swimming medusae.

      The polyp stage is often absent or reduced.

      Moon jelly:

      Thimble jellies:

      Phylum Cnidaria, Class Cubozoa.

      Box jellies and sea wasps have box-shaped medusae and complex eyes.

      Their tentacles are highly toxic; some are more potent than cobra venom.

      Sea wasp:

      Phylum Cnidaria, Class Anthozoa.

      Sea anemones, sea fans and most corals have only the polyp stage and are often colonial and sessile.

      Sea anemone:

  12. Most Eumetazoa belong to the clade            and exhibit            symmetry and triploblastic embryonic development.
  13. Phylum                  are flatworms with a gastrovascular cavity.

    Phylum Platyhelminthes (flatworms).

  14. class Turbellaria
  15. class Trematoda
  16. class Cestoidea

      Phylum Platyhelminthes, Class Turbellaria.

      Planarians have a mouth at the tip of a pharynx to take food into the gastrovascular cavity (intestines).

      Waste is excreted through the mouth.

      The nervous system is organized into two nerve cords and clustered in anterior ganglia.

      Eyespots (ocelli) can detect light.


      Phylum Platyhelminthes, Class Trematoda.

      Trematodes (flukes) are parasites that use two suckers to attach to primary host (human).

      Sexual reproduction takes place in the primary host: a female fits into a groove on the male's body.

      Juveniles mature in intermediate hosts such as snails.

      The motile larvae that escape from the intermediate host are called "cercaria".

      Phylum Platyhelminthes, Class Cestoidea.

      Tapeworms are parasites that use a scolex to attach to host intestines with hooks and suckers.

      Many segments of proglottids produce eggs and break off after fertilization.

  17. Phylum           are roundworms with a               .

    Phylum Nematoda (roundworms) belongs in the clade Ecdysozoa.

    They are covered with a tough exoskeleton (cuticle) which must be shed or molted through a process called ecdysis as the animal grows.

  18. class Trichinella
  19. class Ascaris.

      Phylum Nematoda, Class Trichinella.

      Trichinella can cause trichinosis when they are ingested by eating undercooked pork or other meat.

      Adults mate in the intestine, producing juveniles, which encyst in muscles.

      Phylum Nematoda, Class Ascaris. Giant intestinal roundworms are a serious pig and human parasite in tropical areas with poor sanitation.
  20. Phylum           are soft-bodied animals.

    Phylum Mollusca.

    Molluscs include snails, clams, and octopuses.

  21. class Gastropoda: embryonic torsion.
  22. class Bivalvia
  23. class Cephalopoda

      Molluscs have a body plan with three main parts:

    • Muscular foot for movement.
    • Visceral mass that contains the organs.
    • Mantle that secretes a shell, if present.

      Phylum Mollusca, Class Gastropoda.

      Snails and slugs secrete slime on which they crawl.

      Slugs have lost their outer shell.

      Nudibranchs are sea slugs that use gills for gas exchange.

      Nudibranch predator:

      Embryonic torsion in a gastropod. Because of torsion (twisting of the visceral mass) during embryonic development, the digestive tract of a mature gastropod is coiled and the anus is near the anterior end of the animal.

      Phylum Mollusca, Class Bivalvia.

      Clams, mussels, scallops, oysters have a shell with two valves and paired gills.

      They feed by passing water through siphons, and often anchor themselves in the substrate with their muscular foot.

      Clam locomotion:

      Phylum Mollusca, Class Cephalopoda.

      Squids, octopuses, cuttlefish, chambered nautiluses are the only molluscs that exhibit cephalization: development of a head.

      They have a closed circulatory system that enables them to move quickly by jet propulsion using siphons.

      Tentacles are used to capture prey.

  24. Phylum           are segmented worms with a true         .

    Phylum Annelida.

    Annelids are coelomates that exhibit segmentation in their body plan.

  25. class Oligochaeta
  26. class Polychaeta
  27. class Hirudinea

      Phylum Annelida, Class Oligochaeta.

      Earthworms have "few chaetae" (setae), which are bristles made of chitin that aid in anchoring the body to burrow.

      The body is segmented with separate mouth and anus.

      Circular and longitudinal muscles enable it to move by peristaltic locomotion.

      Earthworm locomotion:

      Phylum Annelida, Class Polychaeta.

      These marine segmented worms have a well-developed head.

      Each segment has a pair of parapodia ("almost feet") with "many chaetae".

      Phylum Annelida, Class Hirudinea.

      Leeches have flattened segments with no chaetae.

      Suckers at the anterior and posterior ends attach to food.

      Some species such as Hirudo medicinalis secrete hirudin to prevent blood from coagulating, and are used as medicinal leeches to drain blood from an injury.

  28. Phylum             have            bodies.

    Phylum Arthropoda.

    Arthropods belong in the clade Ecdysozoa.

  29. Cheliceriformes
  30. Myriapoda
  31. Hexapoda
  32. Crustacea

      External anatomy of an arthropod.

    • The body of a lobster is segmented.
    • The appendages (antennae, pincers, legs, etc), are jointed.
    • The body is covered by an exoskeleton made of chitin.

      The exoskeleton requires them to molt as they grow, in a process called ecdysis.

      Phylum Arthropoda: Cheliceriformes.

      Horseshoe crabs, scorpions, spiders, ticks, mites have chelicerae and pedipalps in their mouth parts that may be modified as pincers.

      They possess four pairs of legs.

      Ticks and mites:

      Phylum Arthropoda: Myriapoda.

      Millipedes (class Diplopoda) have two pairs of legs on each trunk segment. Centipedes (class Chilopoda) have one pair of legs per trunk segment.

      Phylum Arthropoda: Hexapoda. Insects have three pairs of legs and usually two pairs of wings. The body is divided into head, thorax, abdomen.

      Phylum Arthropoda: Crustacea.

      Crabs, shrimp, and barnacles have two pairs of antennae and three or more pairs of legs.

      Many are decapods and have ten legs.



  33. Phylum                are                .

    Phylum Echinodermata.

    Echinoderms are spiny-skinned animals.

  34. class Asteroidea
  35. class Ophiuroidea
  36. class Echinoidea
  37. class Crinoidea
  38. class Holothuroidea
  39. class Concentricycloidea

    These deuterostomes reproduce by external fertilization.

    Sea urchin spawning:

      Echinodermata possess a spiny skin that covers an endoskeleton. The madreporite is used to filter water into a sea star's water vascular system for gas exchange. The water vascular system consists of a ring canal and five radial canals and terminates in branches called tube feet. Echinoderms:

      Phylum Echinodermata, Class Asteroidea.

      Sea stars have star-shaped body with multiple arms; suckers on tube feet.

      Phylum Echinodermata, Class Ophiuroidea.

      Brittle stars have a distinct central disk; long, flexible arms; tube feet lack suckers.

      Phylum Echinodermata, Class Echinoidea.

      Sea urchins are roughly spherical or disk-shaped; five rows of tube feet on the spines enable movement.

      Sea urchin locomotion:

      Phylum Echinodermata, Class Crinoidea.

      Sea lilies have feathered arms surrounding upward-pointing mouth.

      Phylum Echinodermata, Class Holothuroidea.

      Sea cucumbers have five rows of tube feet and additional tube feet modified as feeding tentacles.

      Sea cucumbers:

      Phylum Echinodermata, Class Concentricycloidea.

      Sea daisies have a disk-shaped body ringed with small spines.