Chapter 30- Protostomes

Protostomes

_______ are triploblastic and bilaterally
symmetrical; the embryonic blastopore becomes
the mouth

lophotrochozoans and ecdysozoans

Based on DNA sequencing, protostomes are
divided into two major clades:

sessile

Nearly all animals with a lophophore are _____
as adults.

trochophore

Some lophotrochozoans have a _______
larval form that moves by beating a band of cilia

spiral

Some lophotrochozoans have ____ cleavage

cuticle

ecdysozoans Have an external ____, secreted by the epidermis

exoskeleton, chitin

In arthropods(jointed foot), the cuticle is an
_____, thickened by proteins and ____, a
waterproof polysaccharide

arrow worms

• Evolutionary relationships were long
debated.
• Early development is similar to
deuterostomes but gene sequences
identify them as protostomes
• They are transparent and small- gas
exchange and waste excretion occur by
diffusion through body wall

arrow worms

______________ have No circulatory system: wastes and nutrients are
moved by cilia that line the coelom.
• Hermaphroditic
• No larval stage: miniature adults hatch from eggs
that are fertilized internally
• Predators of planktonic organisms

filter feeders

Bryozoans and Entoprocts are _______ ________

entoprocts

• Anus in center of the ring of tentacles.
• Food particles move from base to tip of tentacles; no
coelom.

bryozoans

Anus is located outside the ring of tentacles;
three-part coelom.
• Food particles move from tip to base of
tentacles.
• Colonies form by asexual reproduction of a
founding member; may have up to 2 million
individuals.

flat worms

__________(lophotrochozoan)
• Dorsoventrally flattened; no gas
transport system, so every cell
must be near the surface.
• Acoelomate
• Digestive tract: mouth opens into a
blind gut, often highly branched,
which increases surface area for
absorption of nutrients.
• Most species are endoparasites.
They absorb digested food from
the digestive tract of the host

rotifers

: mostly in fresh water.
• Tiny (50–500 m), but have specialized
internal organs and a complete gut.
• Body cavity is a pseudocoel that functions as a
hydrostatic skeleton, but most propel
themselves by cilia.
• The corona is a ciliated organ on the head.
Beating cilia sweep food particles into the
mouth and into the mastax, an organ that
grinds the food.
• Some can protrude the mastax through the
mouth and capture prey with it.

hermaphroditic

when an animal has a sperm and egg

proboscis

The ______ is the ribbon worm’s
feeding organ located in the
rhynchocoel (Coelom+)

brachiopods

• Solitary marine animals with two-part shells
connected by a ligament.
• Resemble bivalve mollusks, but the shell
evolved independently.
• The two halves of the shell are dorsal and
ventral.
• Feed using lophophores
• Coelom+

phoronids

• Small, sessile, marine worms; secrete a tube of
chitin in which they live.
• Have a U-shaped gut; feed using a lophophore.
• In most species, eggs are released into the water
and fertilized there; in a few species, eggs are
fertilized and brooded internally.
• Coelom+

annelids

(earthworms, leeches, and marine worms)
Clearly segmented; the coelom in each segment is
isolated from the coelom in other segments.
• A separate nerve ganglion controls each segment.
• Most have a thin, permeable body wall that serves for
gas exchange; restricted to aquatic or moist habitats

foot

—large, muscular structure, originally for locomotion and
support of internal organs

visceral mass

—heart, digestive, excretory, and reproductive
organs

mantle

—fold of tissue that covers organs in the visceral mass;
secretes the calcareous shell

open

Mollusks, except cephalopods, have an ______
circulatory system

hemocoel

Blood and fluids empty into the _____, where
oxygen is delivered to internal organs. (Reduced
coelom)

gastropods

: snails, slugs
Most move by gliding on the foot, but in a few
species

bivalves

: clams, oysters, scallops, mussels;
Have hinged, two-part shells. Many use the foot to
burrow into mud or sand.

cephalopods

____: squids, octopuses

thin

Priapulids, kinorhynchs, and loriciferans have a ______ cuticle

nematode, ecdysozoans

roundworms are ______ which are _______, they are unsegmented; thick,
multilayered cuticle

horsehair worms

_______________: very thin; most are
freshwater; 350 species.
• Larvae are endoparasites of insects
and crayfish.

endo

larvae are ____parasites

tardigrades (water bears)

• Fleshy, unjointed legs
• Fluid-filled body cavity acts as a hydrostatic skeleton.
• Extremely small
• No circulatory or gas exchange systems.

velvet worms

Live in leaf litter in the humid tropics.
• Thin, flexible cuticle contains chitin.
• Fluid-filled body cavity acts as a hydrostatic
skeleton

chelicerates

sea spiders, horseshoe crabs, and arachnids are all

crustaceans

Dominant marine arthropods today; also
terrestrial and freshwater
Shrimps, lobsters, crayfishes, and crabs
• 3 body regions: head, thorax, abdomen

incomplete

________metamorphosis: changes are
gradual

complete

________ metamorphosis: changes are
dramatic

neopterans

________: all the other pterygote insects that
can fold their wings.
Some have incomplete metamorphosis

holometabolous

insects (subgroup of
neopterans) have complete metamorphosis:
Flight is one of the reasons for the remarkable
evolutionary success of the insects.