I. Phylum Porifera (sponges; pore bearer ) A. General characteristics 1. simplest animals 2. asymmetric 3. aquatic habitats a. typically marine 4. live alone or in colonies a. often members of reef habitats Ph. Porifera and Ph. Cnidaria Biology Two DOL 31-33 6/29/2016 B. Anatomy 1. 3 cell layers, but lack true tissues a. outer = epidermis 1) covered in ostia a) pores for entry of H2O, O2 & nutrients b. middle = gel layer w/ specialized cells 1) amebocytes (a.k.a. archaeocytes) = transport nutrients, complete digestion 2) spicules = provide shape & support c. inner = choanocytes (a.k.a. collar cells) 1) have flagella that extend inward to help circulate water through sponge
2. Inside of body is hollow a. central cavity = spongocoel b. large opening = osculum 1) wastes, excess water exit through it 2) aids release of sperm for sexual repro C. Physiology 1. Feeding, digestion a. filter feeders b. intracellular digestion 2. Respiration, excretion by diffusion 3. Lack nervous system 4. Adults are sessile a. juveniles swim or drift freely 5. reproduce sexually & asexually a. sexual uses internal fertilization 1) hermaphrodites form both sperm & eggs a) release sperm, drawn in by ostia b. asexual uses budding, gemmules 1) can also regenerate from broken pieces D. Sponge classes 1. Class Calcarea a. calcium carbonate spicules b. shallow tropical marine habitats c. small & irregularly shaped d. ex: yellow calcareous sponge, white cryptic sponge
2. Class Demospongiae a. 90% of all sponges b. silicon dioxide or spongin spicules c. ex: bath sponge, orange elephant ear sponge 3. Class Hexactinellida a. silica spicules arranged in lattices b. deep water habitats 1) abundant in Antarctica c. cup, vase or urn shape d. ex: Venus flower basket II. Ph. Cnidaria ( stinging nettle ) A. General characteristics 1. 4 main types a. corals, anemones, jellyfish, hydra 2. aquatic habitats a. most are marine (except hydra) b. often part of reef habitats 3. radial symmetry 4. carnivores 5. sessile as adults a. except jellyfish
B. Anatomy 1. 2 main body forms a. Polyp 1) cylindrical body w/ mouth & tentacles upward 2) sessile 3) corals, anemone, hydra b. Medusa 1) body = upside-down bowl w/ mouth & tentacles facing down 2) motile 3) jellyfish & some hydrozoans 2. Two specialized tissue layers a. outer = ectoderm 1) aids movement b. gel layer in between = mesoglea c. inner = endoderm 3. Tentacles contain cnidoblasts a. stinging cells w/ nematocysts 1) poisonous - paralyzes 2) for defense, feeding 4. Center of body = gastrovascular cavity a. 1 opening serves as mouth & anus b. receives food, allows wastes to exit 5. Lack respiratory & excretory systems a. simple nerve net between tissue layers 1) lack brain
C. Physiology 1. Feeding a. sting prey w/ nematocysts 1) tentacles push food to mouth b. extracellular digestion begins in gastrovascular cavity c. intracellular digestion completes it 2. Circulation, respiration, excretion by diffusion a. digestive wastes exit mouth opening 4. Reproduction alternates during life cycle a. asexual by budding or fission b. sexual 1) corals - internal or external fert. 2) anemones both eggs & sperm leave body & fertilize externally 3) jellyfish males spawn, females carry fertilized eggs in brooding pouches in tentacles or stomach 3. Some specialized sense cells a. nerve net coordinates tentacle movement b. statocysts aid vertical movement, balance c. eyespots (ocelli) detect light
D. Cnidarian classification 1. Class Anthozoa ( flower animal ) a. corals, anemones b. sessile c. found in reef habitats d. ex: brain coral, rose bulb anemone 2. Class Scyphozoa ( cup animal ) a. true jellyfish b. motile c. ex: Moon jellies (Aurelia), Lion s mane jelly 3. Class Cubozoa ( box animals ) a. box jellies b. motile c. highly toxic d. ex: Gulf sea wasps, Irukandji jellyfish 4. Class Hydrozoa ( sea serpent animal ) a. sessile or motile 1) may float rather than be attached b. freshwater or marine c. many are colonial d. ex: Portuguese man o war, Hydra