Lecture 2: Ctenophores

Ctenophore Synapomorphies

• Combs made of cilia

• biradial/rotational symmetry

• Colloblasts

Cilia

• Protrusion of cell membrane

• move using organized metachronal beating

• the power and recovery of each cilium follows its neighbors

• 9 microtubules made of tubulin bundled around 1 in the middle

Ctenophore life style

• predatory

• pelagic

• suspension feeder

• key role in estuarine and pelagic ecology

Ctenophore cell layers

• epiderms

• cellular mesoglea

• gastrodermis

Ctenophore body plan

Ctenophore body plan part 2

Ctenophore symmetry

• Rotational symmetry

• 2 planes

  • tentacular plane

  • pharyngeal plane

Colloblast

• Ctenophore synapomorphy

• adhesive cell with sticky secretion used to capture prey (contrast nematocyst)

Ctenophore Digestion

• gastrovascular system

  • branched extensions of the gut that circulate nutrients+water

• it is not clear whether they excrete through mouth or anal pore

Ctenophore nervous/muscular system

• subepithelial nerve net

  • bidrectional or unidirectional synapses

• muscles for locomotion

Cydippid

ctenophore body plan

• ball-like body

• tentacles

• cilliary locomotion

Lobate

• no tentacles

• wing-like lobes

• ciliary locomotion and muscular locomotion

Beroe

• no tentacles

• no lobes

• ciliary locomotion

• predatory sock- a tube open at one end

• feed on other ctenophores and jellies

• teeth made of cilia

Cestid

• no tentacles

• no lobes

• ciliar locomotion and muscular locomotion by undualtion of the body

• flattened along pharyngeal plane

Benthic

• tentacles

• no lobes

• creeping locomotion along substrate

Reproduction

• asexual reproduction by fragmentation (benthic species)

• sexual reproduction

• gametes expelled through mouth

• external fertilization

• hermaphroditic

Pigment

chemicals that differential absorb some colors

Refraction

bending of light path, angle of bending depending on wavelength (ctenophore rainbows)

Iridescence

structural coloring (color changes with angle of view)

Fluorescence

light absorbed at one wavelength and re-emitted at a different wavelength (often paired with bioluminescence)

Bioluminscence

light generated by chemical reaction (often symbiotic bacteria)

Purposes of biolumenscence