The Phylum Ctenophora

Ktenos = combPhoros = bearing

How do Ctenophores differ from Sponges?

Characteristics of Ctenophora

• 8 rows of combs (cilia)• Radially symmetrical• Body consists of two layers

with a third layer called mesoglea (jelly-like substance)

Characteristics of Ctenophora

• Body contains an internal cavity and a mouth and anal pores

• No respiratory or circulatory system; simple diffusion

• Sexual Reproduction – hermaphrodites• All are carnivorous; capture prey with ten

Benthic (bottom dwelling) Ctenophores

• Order Platyctenida.• Found in warm water• Branched tentacles• Look more like sea slugs

Vallicula multiformis

Coastal Ctenophores

• Order Cydippida– Round or oblong in shape– Usually less than 3 cm (1

inch) in diameter

Sea gooseberryPleurobranchia pileus

Coastal Ctenophores

• Order Lobata– Largest– Pair of lobes that are used to capture prey– Short tentacles that remain inside the lobes.

Common northern comb jellyBolinopsis infundibulum

Coastal Ctenophores

• Order Beroida– Flat and grows up to 15cm– Translucent: light pink or yellowish

Beroe’s comb jelly

Oceanic Ctenophores

• Found far off-shore near the surface• More fragile than coastal species • Wing-like

Venus’ girdleCestum veneris

Tortugas red

Ctenophore life cycle

• Hermaphroditic, both egg and sperm.• Eggs and sperm released and fertilized at sea. • Fertilized eggs develop into a larval stage

which gradually grows into an adult.

Ctenophore life-scattering/bioluminescence:

• beating rows of cilia; light defraction• Most Ctenophores are bioluminescent.

Beroe

How do ctenophores fit into the food web?

• All ctenophores are carnivores. • Sticky tentacles adhere to small zooplankton

prey which is to the ctenophore’s mouth.

Ctenophores as marine invaders wreaking ecosystems:

• Ctenophores are recognized to be planktonic carnivores

• Leidy’s comb jelly (Mnemiopsis leidyi) was introduced into the Black sea and caused a full ecosystem fisheries collapse within less than 10 years– Why? • Outcompeted for plankton

Order Lobate

Ctenophores and Medusae (Jellyfish) are they related?

• No• Both are plank tonic, carnivorous, often

transparent and tentacle bearing• At one time, they were both placed in Phylum

Coelenterata but today they are separated.• No polyp stage in Ctenophores

How are Phyla Porifera and Ctenophora similar? Different?

2 layers: EndodermEctoderm with jelly-like middle called the mesoglea

Hermaphrodite

No digestive or respiratory system

Porifera: Sponges Ctenophora: Comb jellies

Asymmetrical symmetrySessileFilter feederRegenerationNo true tissues or organs

Radial symmetryMobileCarnivorousCiliaTentaclesBioluminescenceMouth/anal pores