Lecture 8 Sponges 2 & Radiata 1 Flashcards
cnidocytes
contain specialized stinging organelles
Who are the Cnidaria ?
jellyfish , corals, sea anemones and hydras.
polyp type
sessile
medusa
aka jellyfish, floating or free swimming
recall about sponges (tissue type and symmetry)
No true tissues
asymmetrical
Who are the basal members of the clade eumetazoa ?
Phylum Cnidaria & phylum Ctenophora
main traits of phylum Cnidaria & phylum Ctenophora .
- radial symmetry
- diploblastic
- only have tissue-lvl organization (no organs)
mesoglea
gelatinous/ jelly-like
can contain fibres , ameboid & epitheliomuscular cells
gastrodermis
epithelial cells covering the gastrovascular cavity.
can contain gonads, cnidocytes, gland cells, interstitial and nutritive-muscular.
very weak layer of muscle so water in cavity serves as a hydrostatic skeleton.
epitheliomuscular
covering & contraction
interstitial
undifferentiated stem cells
gland
secrete mucus /adhesive
cnidocytes
contain cnidae, abundant on tentacles
sensory
flagellum as receptors , join with nerve cells
nerve
multi or bipolar
Cnidae
- tiny capsules within cnidocytes
- capsule covered with operculum (lid)
- contain coiled thread/filament
- has tiny barbs/spines in most common form (nematocyst)
lid
operculum
what are the 3 different functional type of cindae ?
penetrants - penetrate prey & inject venom
2) volvents - recoil & entangle prey
3) glutinants - secrete adhesive
How do cnidae work ?
- most equipped with modified cilium acting as a “trigger” ( cnidocil )
- others sensitive to vibrations
- discharge under enormous hydrostatic pressure
Nerve net .
- no central nervous system
- diffuse nervous network comprised of 2 connected nerve nets
- can be considered a neuromuscular system in conjunction with sensory & epitheliomuscular cells
Feeding and digestion of cnidarian
- mouth opens into gastrovascular cavity
- gland cells secrete enzymes & initiate extracellular digestion
- nutritive cells phagocytize particles (intracellular digestion)
- undigested particles carried by amoeboid cells back to gastrovascular cavity for expulsion
Locomotion of cnidarian
- colonial polyps are permanently attached
- hydras & sea anemones can glide via mucous secretions using pedal disc
- medusae swim by contracting the bell.
Diecious
male or female individuals ( separate)
Reproduction of cnidarians
- polyps & medusae play different roles
- polyps can make other polyps via asexual reproduction
- clones via budding or fission
- clones can be dispersed or can stay attached to form a colony that may exhibit division of labour.
