Ctenophores notes

Similarities to Cnidarians

• Radial symmetry

• Diploblastic (two tissue layers)

• Oral-aboral axis (mouth to opposite end)

• Gelatinous mesenchyme (like mesoglea in jellyfish)

• Nerve net instead of a central brain

• use the gastrovascular cavity

Differences from Cnidarians

• More complex digestive system

• Mesenchymal musculature (muscles in mesenchyme, not just tissue layers)

• No sessile stage

• Not colonial

• No nematocysts (stinging cells)

Movement

8 rows of ciliary plates

Colloblasts

sticky cells on tentacles for capturing prey

statolith

controls movement of comb rows

Hermaphroditic

both male & female reproductive organs

Cydippid

larval stage

Bathocyroe fosteri

attracting prey/mates, avoiding predators, communication, camouflage

Biradial symmetry

due to paired tentacles

Tentacle

long and retractable

Body structure

Spherical or ovoid shape

Mesenchyme

structural support

Ctenes (comb rows)

move in waves to help them swim

Neutral buoyancy

neither sink nor float too much

Predators

catch prey with colloblasts

muscular contractions

Tentacles wipe prey into the mouth

Asexual reproduction

Can regenerate lost body parts

Sexual reproduction

Hermaphroditic

Gametes

released from the mouth