Post-midterm Flashcards
What are the trematoda? How do they differ from other platyhelminths
Flukes and digeneans. Have diverticulated gut, specialized genital organs
Describe the external features of the trematoda
Have two suckers: oral and ventral - both used to attach to host. Many can absorb nutrients directly into their bodies.
What purpose does the pharynx of digenean trematodes serve? Describe the gut
Muscularized, acts like a pump to suck food material into mouth to gut. highly diverticulated gut, helps to actively ingest host tissues
Trematodes are typically differentiated by _______
Vitellaria or yolk glands
What purpose does the glycocalyx and tegument of trematodes serve? What is their composition?
Purpose is to resist the digestive enzymes of host.
Tegument is outside the body and is a multinucleated mass.
Briefly describe the generalized digenean trematode lifecyle?
Egg (usually expelled in feces) -> miracidium larva (ciliated larval form that enters a snail then loses ciliaand becomes a..) -> Sporocyst (asexually reproducing clusters of cells which become…) -> Redia (with oral sucker, pair of protonephridia, simple branched gut) -> Metacercaria (basically advanced larvae that encyst themselves then become..) -> Cercaria (leave snail through body wall or gills) -> adult
The cestodes are otherwise known as the _____
tape worms
Briefly describe the anatomy of cestodes
Divided into small sections called “proglottids”, usually have a reduced nervous system and no gut. Have small spines called “microtriches” along the tegument. On one end of the organism is an area called the scolex, which is covered in suckers and anchoring hooks to attach to intestine of host
Describe the reproductive structures found in a Cestode proglottid
Have a genital pore with a cirrus (penis) as well as paired reproductive structures. The male system matures sooner than the female system (so self fertilization is rare). Always contained a vitelline gland.
A _____ proglottid is one that is full of eggs
Gravid
How does tapeworm grow in the intermediate host and transfer to humans?
Ingested, grows in intestine and often pass in feces.
In the intermediate host, the juvenile grows in the muscle of the organism. Thats why it transfers to human mouthparts
What do dog tapeworms do to humans?
Usually they infect the liver, but can infect any organ. Sometimes, it can infect the brain, where it produces scolexes that become large cysts and do not die down
What are the cysts caused by dog tapeworms called? Describe them
Hydatid cysts. Can grow extremely large (golf ball size), Usually the pathology depends on cyst size and location. Single liver cyst could prove fatal.
Cysts are organized by having a thick outer layer, several thinner internal layers, and a bunch of protoscolices.
How are the molluscs related to the annelids?
Share common larval form called the “trochophore larva”.
What are the major groups of molluscs
Gastropods, bivalves, cephalopods
What are the characteristics that all molluscs share?
Bilateral symmetry, triploblastic/3 tissue layers, unsegmented, eucoelomate, soft bodied (composed of head, foot, visceral mass), mantle secretes shell, respiration occurs by gills/ctenidia
Why are gastropods called what they are?
Called such because the gastric pouch is above the foot
Gill structures of molluscs are called ____
Ctenidia
Briefly describe the circulatory systems of the mollusc groups
Gastropods and bivalves use low-rate ciliary currents with a counter current exchange systems.
Cephalopods require more quick blood flow, since they move more quickly and have a fluid skeleton
Describe the respiration of the different mollusc groups
Gills or ctenidia are located in the mantle cavity. May have between 0 and two gills. Land forms often used mantle wall as a lung.
Ctenidia are irrigated by ciliary movements in the mantle cavity, use counter current exchange.
Describe the gill structures of molluscs
Lobes sticking out from a central axis with afferent and efferent blood vessels running through it. Skeletal rods support the filaments, and water runs along the gill filaments
Describe the digestive system of molluscs?
May be straight, u-shaped, or coiled. Begins at the mouth and ends at the anus, which empties into the mantle cavity (mantle current helps remove wastes). Mouth is characterized by a radula, and a muscular tongue that pushes it out of the mouth. Stomach is called a protostyle, which is a rotating cone of mucous that sorts large food particles from small food particles. Grooves and folds lead to opening of the digestive glands.
The membrane on top of the radula is made of _____
chitin
Describe the basic diets of molluscs
Many Gastropods are grazers, scraping plant/animal material off the ground. Bivalves typically filter feed (or may be detritovores), and cephalopods use a beak to tear apart prey
Describe the mollusc circulatory system
Have muscular heart composed of muscular ventricle which pumps into aorta then branched aorta then empty into sinuses. Nephridia pick up blood from there and then filtration occurs
Why is the heart of cephalopods unique?
Double chambered heart
Describe the excretory system of molluscs
Consists of 1 or 2 pairs of metanephridia (open at both ends) which open from the floor of pericardium and empty into the mantle cavity
Describe the nervous system of molluscs
Have ring of nervous tissue around esophagus, connected to bundles of nerve fibres, with many many branches. Changes based on lifestyle (ex. cephalopods have highly complex eyes, whereas bivalves have no eyes)
Describe the sense organs that molluscs possess
Statocysts for balance, tangoreceptors for touch/pressure, chemoreceptors for measuring silt levels, eyes.
Describe the reproductive systems of molluscs
Usually dioecious. Some, such as slugs and land snails are hermaphroditic. Gonads release gametes by rupture. Gonads are frequently reduced to a single one. Fertilization usually external.
Describe the larvae of molluscs
First larvae is a trochophore, which is free swimming in all but the cephalopods (then it is a egg). In bivalves and gastropods it metamorphoses into veliger. Veliger has 2 ciliated flaps for swimming and feeding.
Clams have no larvae.
How does the gastropod mantle become so twisted? Describe the external anatomy of it
Mantle on one side is more active than on the other side, resulting in spiral shape. Usually spirally-coiled either dextrally or sinistrally, secreted by edge of the mantle.
Describe the typical gastropod shell?
Composed of outer periostracum, middle prismatic layer (CaCO3), and inner nacreous layer. Formation of shell begins in larval stage as the “protoconch” and it forms the tip of the whorl throughout life. The rest of the shell is uniform in structure and is laid by the edge of the mantle over time, resulting in a spiralled tube through the shell wrapping around columellae.
The _____ forms the point of attachment for the retractor muscles in gastropods. What is the purpose of these muscles?
Columella. Retractor muscles function to pull head-foot complex into the aperture of the last coil of the shell. There may be an operculum to help close the shell
Why is the anus/mantle cavity opening of gastropods over the mouth?
Because if it was behind the mouth and foot, water wouldn’t’ be able to enter the mantle cavity when the shell is closed
How do soft bodied gastropods protect themselves?
They often store nematocysts from coral polyps - incorporating cnidarian tissues into theirs. Toxins are also secreted from the top of the body.
Briefly describe class bivalvia
All aquatic, most marine. Have a bivalved shell hinged at the dorsal surface. Allows protrusion of foot (For locomotion) and siphons (for respiration/feeding). Can be sedentary or motile.
How do clams move?
Protrude foot from body, attach it to substrate, and contract muscles to pull it forward
The _____ muscle stretches the hinge ligament of Bivalves
adductor