Lecture 21 Porifera and Cnidaria Flashcards
what are invertebrates?
animals lacking a backbone
- account for 95-97% of known animals species
what are the basal animals?
porifera “Parazoa”
what are characters of Parazoans (4)
- lack true tissues
- almost all belong to phylum Porifera
- much like colonial protists
- retain a deal of autonomy (single cells can reassemble)
what theory did sponges help develop?
- cell-cell recognition theory
what are characteristics of the Phylum Porifera?
- lack true tissues
- except for larval stage, are sessile
- model organisms: have earliest hints of features that are present in higher taxa
what is the sponge morphology? (4)
- no obvious tissues or organs - partially differentiated
- structural support comes from spicules
- some havetough collagen-protein network for support - spongin
- made of four simple and independent cells
what are spicules?
- tiny hard needles or rods made of CaCO3 or Silica
what are the four simple and independent cells of sponges?
- collar cells which line the interior of the sponge
- epidermal cells which form the skin on the outside of the sponge
- choanocytes which generate H2O current through sponge and ingest suspended food; bring O2 and nutrients to sponge while also removing waste and CO2
- Amoebocytes found in mesohyl and play roles in digestion (nutrient transport) and structure (form spicules)
what is the mesohyl?
gelatinous matrix between epidermis and choanocyte layer
- contains amebocytes and skeletal elements
- acellular
- resembles type of connective tissue but it is NOT tissue bc acellular
how do sponges eat
suspension feeding
how does suspension feeding work?
- water is drawn through pores called OSITA into a cavity called a spongoceol and out through an opening called an osculum
- food particles are trapped in a mucus covered microvilli
- engulfed by phagocytosis and digested or transferred to amoebocytes
- amoebocytes carry food and nutrients to other cells or use it for energy to make spicules or other structural materials
what kind of reproduction do sponges have?
hermaphroditic – simultaneous or sequential
since sponges don’t have testes or ovaries, where do eggs and sperm arise from?
- eggs arise from modified amoebocytes
- sperm arises from modified choanocytes
what kind of fertilization do sponges exhibit?
- external - some
- internal - most, eggs are retained in mesohyl, the zygote is retained until it develops into ciliated larva
if a sponge loses parts what can it do?
regenerate
- dissociated cells settle, migrate and form active aggregates – form larger aggregates
what is the importance and ecology of sponges?
- suspension feeding cleans water
- symbiotic mutualisms with single celled algae (limited to photic zone)
- many live inside sponges
what are the two phyla in radiata?
what are characteristics of these two phyla?
- cnidaria and ctenophora
- simple body plan
- eumetazoa: true differentiated tissues
- diploblastic
- organs
- most are radially symmetrical
what is the cnidarian body plan?
- diploblastic, radial
- sac with a central digestive compartment called the gastrovascular cavity
- e
what is the cnidarian body plan?
- diploblastic, radial
- sac with a central digestive compartment called the gastrovascular cavity
- epidermis
- mesoglea: middle jelly acellular matrix in between
- gastrodermis: endoderm lines gastrovascular cavity
- two forms – polyp sessile form; medusa motile form
how does the medusa move?
hydrostatic skeleton
how do cnidarians obtain energy?
they are carnivorous so they use tentacles to catch prey
ALL ARE PREDATORY
what are cnidarian tentacles armed with?
cnidocytes
- unique cells that function in defense and capture prey
- contain complex endocellular structure, most common is the NEMATOCYST
what are nematocysts?
specialized organelles with cnidocytes which eject stinging thread, touch sensitive
what are the four classes of cnidaria? which three do we focus on?
- hydrozoa
- scyphozoa
- cubozoa
- anthozoa
HSA
what is the class hydrozoa?
- alternates between polyp and medusa form
- ex: hydra: exists only in polyp form and reproduces asexually by budding
- polyp is sessile and often colonial – reproduces via budding
- medusa bud off asexually but reproduces sexually – larvae settles to form polyp
what is class scyphozoa?
- jellies (medusae) are the prevalent form of the life cycle
- use hydrostatic skeleton to navigate through contraction-pulsations of the bell-like body
- mostly water
- many bioluminescent
what is class anthozoa?
- corals and sea anenomies, occur only as polyps
- corals often form symbioses with algae and secrete a hard external skeleton, limited to photic zone
- anenomies can live as single individuals, corals are often colonial
