Lophotrochozoa

Phylum Platyhelminthes

flatworms named for broad and flattened shape of bodies

Phylum Platyhelminthes symmetry

bilateral

Phylum Platyhelminthes (flat worms) ceolem

acelomate

acoelomates

like a true coelom

flatworms are blankblasitc

tripoblastic

Flatworms do not have which systems?

circulatory or regulatory

Phylum Platyhelminthes: deuterostomes or protostomes

protosomes

protostomes

mouth first

deuterosomes

anus forms first

Phylum Platyhelminthes head

cephalization

cephalization

definite head at the anterior end

how does gas move in Platyhelminthes

via passive diffusion

what does the flattened” body form of platyhelminths provide?

a large surface area for gas exchange

Phylum Platyhelminthes locomotion

outer circular and inner longitudinal body wall muscles act antagonistically against a hydrostatic skeleton

how do free living flatworms glide

via ciliated epithelial cells on ventral surface

nervous system of Platyhelminthes

simple “ladder-like” nervous system with an anterior and paired cerebral ganglia and nerve cords

Platyhelminthes ocelli

light-sensitive eye spots

Platyhelminthes auricles

chemosensory cell

Platyhelminthes osmoregualtion

control balance of water + salts and excretion of N-waste

Platyhelminthes protonephridia (flame + tube cells)

collect excess fluid and carry it to excretory pores in the outer epidermis

Platyhelminthes flame-cell

beating of cilia draws interstitial fluid into the flame cell, then is filtered by a tubule, water + waste passed through an excretory pore

feeding in Platyhelminthes

incomplete gut (single opening is the mouth and anus)

reproduction in Platyhelminthes

both sexual and asexual

Platyhelminthes sexual reproduction

most flatworms are monoecious with internal fertilization by exchange of sperm

monecious

hermaphrodite

asexual reproduction in Platyhelminthes

fragmentation followed by regeneration

flatworm Class Turbellaria

free-living in water

Turbellaria anus

no anus

Turbellaria mouth

near middle of body’s ventral near pharynx

flatworm Class Trematoda

flukes

flukes are

endoparasitic

endoparasites

parasitize intestinal tracts

what is at the anterior of flukes

oral and ventral suckers

flatworm Class Cestoda

endoparasitic tapeworms

Class Cestoda body

body divided into an anterior scolex region

Class Cestoda bears

suckers and hooks to attach to an intestinal wall of host. no mouth

Class Cestoda scolex

followed by a long chain of units called proglottids

proglottids

containing both ovaries and testes

cestoda proglottids closest to the neck are

immature= no sex organs

cestoda gravid proglottids

only eggs

class cestoda gut

no gut

annelids symmetry

bilateral

annelids coelom

eucoelem

annelids are blankblastic

triploblastic

Phylum Annelida

the segmented worm

Phylum Annelida outer cuticle

collagen secreted by epidermis

where are annelids important

marine ecosystems

annelids body

metameric

metameric

the body is a series of repeating segments or metameres

evolutionary significance of metamerism

permits greater flexibility, compartmentalization, complexity and larger size

annelids coelom

divided by septa

annelids circulatory system

closed

closed circulatory system

blood stays in vessels

annelid movement

circular muscles, longitudinal muscles, septa allow segments to move somewhat independently

annelid locomotion

using alternating waves of muscle contraction using circular contraction

annelid nervous system

pair of cephalic ganglia (“brain) attaches to a double or fused ventral nerve cord that runs the length of the animal with ganglia and nerve branches repeated in each metamere

annelid excretory system

pair of metanephridia in almost all segments is composed of a ciliated funnel that sweeps coelomic fluid into a coiled tubule that filters out toxic N-waste from fluid and capillary blood

annelid feeding

filter feeders, carnivores, herbivores, scavengers, deposit feeders, blood-sucking parasites

annelid digestion

complete gut that is compartmentalized

complete gut

digestive tract with a mouth and anus

annelid reproduction

embryo becomes a swimming trochophore larva that grows into an adult

polychaetes

have externally fertilized eggs that develop into trochophore larva

earthworm reproduction

hermaphrodites exchange sperm

earthworms specialized gut regions

digestion and absorption

polychaetas

externally fertilized eggs that develop into trochophore larva

earthworm eggs

hatch as worms

earthworm food

deposit feeders / detritivores

deposit feeders / detritivores

ingest soil with organic matter

Phylum Mollusca eucoelomate

coelom is reduced and limited to the region around the heart

Phylum Mollusca symmetry

bilateral

Phylum Mollusca blankblastic

triploblastic

Phylum Mollusca classes

Bivalvia (clams, mussels)
• Gastropoda (snails, slugs)
• Cephalopoda

mollusca reproduction

both monoecious and dioecious species
• usually internal fertilization

gastropods and bivalves larva

veliger

veliger

larva with shell (and ciliated for swimming)

mollusca head and feet

contain sensory organs and muscles

mollusca visceral mass

contains digestive, reproductive, and circulatory organs

Mollusca mantle

secretes the shell, forms a mantle cavity or space that contains gills (“ctenidia”) or is vascularized like a “lung”

HAM

hypothetical ancestral mollusk

mollusca radula

a tongue-like organ bearing rows of sharp “teeth” used in feeding

mollusca gut

complete

Mollusca Class Gastropoda torsion

moves mantle cavity and anus from the rear to an anterior position over the head

Mollusca Class Gastropoda shell types

shell is straight or often coiled

Mollusca Class Gastropoda operculum

trap-door” structure on the dorsal side of the foot that closes the aperture (opening) of the shell when the animal retracts (defense; prevent desiccation)

which animals Mollusca Class Gastropoda have stolen weapons

some sea slugs (nudibranchs)

how do sea slugs get stolen weapons

feed on cnidarians and store functional nematocysts in cnidosacs at the tips of outgrowths of their gut called cerrata

Mollusca Class Bivalvia gills

called ctenidia, used for respiration and filter feeding

Mollusca Class Bivalvia siphons

permit water to enter and exit mantle cavity while buried

Mollusca Class Cephalopoda

squids, octopuses, nautilus, and cuttlefish

the two phyla with the highest species richness

mollusca and annelida