Ctenophores & Platyhelminthes

Comb plates

• 8

• Beat & enable propulsion

• Most have tentacles

Ctenophores are

• Holoplankton

• radially symmetrical

Statocyst

Small transparent, bubble-like structure with hairs connected to CaCO3. Used for balance/orientation

Digestion/nutrition

• carnivorous

• larval fish, zooplankton, ctenophores & jellies

Colloblasts

Specialized adhesive cells on tentacles

Echlora rubra

Only ctenophore with nematocysts

Reproduction

• Mostly hermaphroditic

• Shed eggs/sperm into water column

• Few brood

Cydippid

Free swimming larva

Ecological

Beroe ovata controls the population of mnemiopsis leidyi

Cephalization

Concentration of sense organs in head region

Platyhelminthes have

• flattened bodies

• cephalization

• bilateral symmetry

Class Trematoda

• parasitic

• complex life cycle

• sexual and asexual reproduction

• multiple hosts

Class Cestoda

• parasitic

• digestive tract

• gain nutrients from host

Nutrition

• Most are carnivores

• use chemoreceptors

Hunting prey

• Entangle prey & suffocate it

• Stab it

Reproduction

• Regenerate missing body parts

• Hermaphrodites

• Penis fencing & hyperdermic insemination

Trematode ecology

• Go through multiple hosts to get to final

• modify host behavior

Nemertea

• infaunal

• Carnivores (annelids & crustaceans)

Nemertea hunting

• coil around prey with toxic mucus-covered proboscis

• Swallow prey whole & track mucus

Nemertea reproduction

• Asexually/fragmentation

• Most sexually reprod. external fertilization

Nemertea ecology

• Commensalism w/ molluscs

• Scavengers

• Prey for higher consumers

• Eat crab eggs