“Lower” Invertebrates I: Sponges & Radiata Chapter 8 “Lower” Invertebrates I: Sponges & Radiata

Key Concepts Sponges are asymmetric, sessile animals that filter food from the water circulating through their bodies. Sponges provide habitats for other animals. Cnidarians and ctenophores exhibit radial symmetry. Cnidarians possess a highly specialized stinging cell used to capture prey and for protection.

What Are Animals? Animals: multicellular eukaryotic cells without cell walls cannot produce their own food Invertebrates or vertebrates (most animals are invertebrates)

Sponges Phylum Porifera Basic characteristics: no tissues or organs asymmetric sessile Anon. Wiki Commons

Sponge Structure and Function

Sponge Structure and Function 3 basic body forms: leuconoid from most efficient, most common

Sponge Structure and Function Nutrition and digestion suspension/filter feeders collar cells (choanocytes) filter out tiny food particles pinacocytes and archaeocytes (a.k.a. amoebocytes) ingest larger food particles by phagocytosis Most food digested and distributed to other cells by archaeocytes

Sponge Structure and Function Reproduction in sponges asexual reproduction budding fragmentation sexual reproduction most hermaphrodites eggs from archaeocytes and sperm from modified collar cells

Fertilization Sperm cell engulfed by a choanocyte Egg cell Sperm cell (modified choanocyte) Embryo Asexual reproduction Sexual reproduction Planktonic amphiblastula larva Bud Figure 8-4 SPONGE REPRODUCTION. Sponges can reproduce asexually (by budding) or sexually. New sponge New sponge Larva settles and attaches to bottom or other surface Figure 8-4 p193

Ecological Roles of Sponges Competition corals and bryozoans Predator-prey relationships few species eat sponges spicules chemical deterrents

Ecological Roles of Sponges Symbiotic relationships mutualistic or commensalistic hosts organisms live within the canals

Ecological Roles of Sponges Sponges and nutrient cycling boring sponges

Cnidarians: Animals with Stinging Cells Include jellyfish, hydroids, corals and sea anemones cnidocytes ErgoSum88

Organization of the Cnidarian Body

Stinging Cells Cnida nematocysts

Stinging Cells Dangerous species Portuguese man-of-war box jellyfish

Types of Cnidarians Hydrozoans or Hydroids mostly colonial colonial forms contain 2 types of polyp: Feeding polyp Reproductive polyp hydrocorals secrete a calcareous skeleton some produce floating colonies (e.g. P. man-o-war)

Types of Cnidarians Jellyfish scyphozoans—true jellyfish (class Scyphozoa) plankton medusa is predominant photoreceptors

Types of Cnidarians Box jellyfish box jellyfish (class Cubozoa) box-shaped bells relatively strong swimmers tropical complex eyes (image-forming?) voracious predators, primarily of fish

Types of Cnidarians Anthozoans (class Anthozoa) include sea anemones, corals and gorgonians sea anemones benthic gastrovascular cavity divided though sessile, many can change locations

Types of Cnidarians Anthozoans (class Anthozoa) coral animals polyps secrete a calcium carbonate skeleton stony corals form reefs Nick Hobgood

Types of Cnidarians Anthozoans (class Anthozoa) soft corals polyps that form plant-like colonies

Nutrition and Digestion Gastrovascular cavity digestion and transport 1 opening: mouth/anus Many suspension feeders Jellyfish and box jellyfish are carnivorous Sea anemones generally feed on invertebrates, some large species feed on fish, shallow water species have symbiotic algae

Reproduction asexual polyp stage sexual medusa stage fission, budding common in corals strobilation common in hydroids and jellyfish sexual medusa stage

Reproduction Anthozoans asexual reproduction IS COMMON pedal laceration fission budding sexual reproduction male and female forms, gametes are released planula larva

Ecological Relationships of Cnidarians Predator-prey relationships cnidarians are predators stinging cells discourage predation sea turtles, some fish and molluscs prey on hydrozoans and jellyfish

Ecological Relationships of Cnidarians Habitat formation coral polyps form complex 3-dimensional structures inhabited by thousands of other organisms coral reefs provide a solid surface for attachment, places for pelagic animals to rest and hide and buffer waves and storms Terry Hughes

Ecological Relationships of Cnidarians Symbiotic relationships Portuguese man-of-war and man-of-war fish reef-forming corals and zooxanthellae sea anemones: clownfish hermit crab

Ctenophores Planktonic, nearly transparent Ctenophore structure 8 rows of comb plates radial symmetry lack stinging cells bioluminescent

Ctenophores Digestion and nutrition Gastro-vascular cavity feeds on plankton, larval fish and fish eggs branched tentacles, adhesive cells, jellyfish stingers to capture prey