CH 14: Flatworms, Mesozoans, and Ribbon Worms

UTA Zoology, Exam specific question info

Triploblastic

Organisms possessing three germ “tissue” layers: ectoderm, mesoderm, and endoderm, which contribute to their body structure and development.

Includes Flatworm, Mesozoans, and Ribbon Worms.

Flatworm, Mesozoans, and Ribbon Worms have __________ symmetry.

bilateral

Protostomia (mollusks, annelids, arthropods)

embryonic blastopore forms the mouth first, then the anus later

Deuterostomia (echinoderms, chordates)

embryonic blastopore forms the anus first, then the mouth later

Phylum Acoelomorpha are small, flat worms that live in _______ sediments, a few _____

marine, pelagic

Acoelomorpha characteristics

• Rootlets of epidermal cilia form interconnecting network

• Most free living, some commensal, some parasitic

• Bilateral symmetry, body flattened dorsoventrally, anterior concentration of nerve cells

• Epidermis cellular

• Gut absent or incomplete and saclike

• Mesodermal muscle cells: longitudinal, circular, diagonal

• Radially arranged nerve cords

• Asexual reproduction by fragmentation

• Monoecious sexual reproduction via internal fertilization

• No excretory or respiratory system

Syncytial tegument

Specialized, multinucleated external covering characteristic of parasitic flatworms (phylum Platyhelminthes) that is resistant to the hos t immune system.

Particularly classes Trematoda (flukes) and Cestoda (tapeworms)

Parasitic worms have no digestive systems. Instead, they rely on the _____ to break down food. may have _____ intestine.

Host, Bind-ended

Protonephridia

the simple waste excretion and osmoregulation organ (nitrogenous wastes)

Flame cell

Unique cell in the protonephridia that is shaped like a cup with a tuft of flagella

Flagella in flame cells draw fluid through the ____, which acts as a collecting net for particles

weir

Flatworm, Mesozoans, and Ribbon Worms have ______________ nerve cords

longitudinal

Nerves are organized into 3 distinct types:

Sensory, motor, association

Ocelli

photosensitive eyespots

Statocysts

senses equilibrium

Rheoreceptors

sense water currents

Asexual reproduction is through ___________ and ________

Fission, Fragmentation

Sexual reproduction is _________ with ______ ______ larve

Monoecious, free-swimming

Class Turbellaria are

free living worms that use muscles and cilia to move

Class Trematoda, subclass Digenea are all ______ ______

parasitic flukes

Digenean reproduction - Clonorchis sinensis (human liver fluke)

Shelled embryos/larvae are excreted in water and penetrate a mollusk. Leave snail and embed in a fish. Juveniles eaten by a human host mature and repeat cycle.

WE EAT FISH AND GET INFECTED

Rediae Stage (liver fluke)

a larval stage of digenetic trematode parasites (flukes) that develops within an intermediate snail host, acting as a site for asexual reproduction to exponentially increase the number of parasites

Digenean reproduction - Schistosoma (blood fluke) What is the GYNECOPHORAL CANAL?

The VENTRAL GROOVE ON SCHISTOSOME = GYNECOPHORAL CANAL!!!

(No rediae stage)

Paragonimus (lung fluke) Cercariae shed into _____ or ingested by ____ eating snails

water, crabs

Where do the Metacercaria in Paragonimus (lung fluke) develop?

Inside of crabs

Paragonimus (lung fluke) can be contracted by consuming ________ ____

undercooked crab

Class Cestoda (Tapeworms) have a ______ on their front end with hook for attachment

scolex

Class Cestoda (Tapeworms) have reproductive segments called _____, a chain of these is called a _____

proglottids, strobila

Turbellaria is _________ in current form.

paraphyletic

Platyhelminths may not be __________ but are generally considered to be so.

monophyletic

Phylum Mesozoa is the _______ between protozoa and metazoa and are all _____ or _____

missing link, parasitic, symbionts

Phylum Mesozoa mainly consist of ______ cells in _____ layers

20-30, two

Phylum Nemertea (ribbon worms): the Greek Nemertes means

one of the Nereids, unerring one

Nemertes refers to the sharp aim of the ________

proboscis

Nemertean characteristics

• Eversible proboscis, unique to Nemerteans, PREDATORY

• Mostly free living, a few parasitic

• Bilateral symmetry, cylindrical anteriorly and flattened posteriorly

• True coelomic cavity called a rhyncocoel

• Complete digestive system

• Four lobed brain

• Sensory ciliated head slits

• Asexual reproduction by fragmentation

• Sexes separate, pilidium larvae

• Flame cells

• Blood vascular system

• No respiratory system