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What are the defining characteristics of the super phylum gnathifera?
All members possess pharyngeal jaws with similar and complex ultrastructure
What is eutely?
A phenomenon where growth is achieved by increasing cell size rather than increasing in the number of cells
What are the defining characteristics of the phylum rotifera?
- 1. Pharynx is highly muscluar and contains jaws for grasping, crushing, or grinding prey, or attaching to a host
- 2. Have toes with adhesive glands
What are the advantages of having a pseudocoelem?
- Allows for Distribution of nutrients
- Removal of Waste
- Space for storing gametes during maturation
What does a hydrostatic skeleton allow for?
Locomotion and moving food through the digestive tract
What does the gnathifera body wall consist of?
- Syncytial epidermis muscles around the pseudocoel
- Digestive tract, excretory organs, and gonads in pseudocel
Where do most rotifers live?
What animals are most parasitic forms of rotifers found?
Arthropods and Annelids
What is the corona?
Ciliated anterior lobes present in many species of rotifers
Interstitially means _______?
Living between grains of sand
How long do most species of rotifers live?
How big can rotifers get?
100 - 500 micrometers
What is a mastax?
A mastax is the muscular modification of a rotifer's pharynx
What is a trophi used for?
Used for grinding following ingestion in rotifers
What is a the corona for?
Allows water and plankton to be drawn into the mouth
What is the trophi made of?
Mucopolysaccharide infused with calcium
What methods of locomotion do rotifers use?
Rotifers use via looping and/or swimming
How does looping locomotion work?
- Circular muscles contract causing the body to elongate.
- The elongated body bends toward the substrate by using the differential contraction of longitudnal muscles.
- Once the anterior end of the animal grips the substrate the foot releases its attachment and the posterior end is pulled forward.
True or False:
During looping the corona is extended to allow for better attachment to the substrate.
False, during looping the corona is withdrawn
How do sessile rotifers attach themselves to the substrate
Rotifers can attach themselves to the substrate using pedal gland secretions that are permanent
How do sessile rotifers protect themselves after attaching to the substrate?
They create protective tubes incorporating debris, sand, or fecal pellets
Describe the rotifers' digestive system
- Consists of a tube with an anterior mouth and a posterior anus
- Digestion is extracellular taking place in the stomach using gastric enzymes
- Waste is accepted by the cloaca to be passed out by the anus
A state of extremely low metabolism
Describe a rotifer's nervous system
Consists of a bi-lobed brain, sensory bristles, 3 antennae, and photo-receptors that lie on the brain
Why are monogonot rotifers unique?
They reproduce by means of parthenogenesis
A term that referrs to the production of eggs without the "mixing in" of genes from any other individual
When do females produce diploid eggs by mitosis? Why?
During good environmental conditions because if the adult female's genotype is currently successful than it should be passed on without change.
Reproduction by meiosis producing all haploid eggs
When do females produce haploid eggs by meiosis? Why?
During poor environmental conditions because it allows for males to be produced allowing for fertilization and "mixing in" of other genes
What happens to a mictic egg if it remains unfertilized?
The unfertilized mictic egg will become a male
A multinucleated mass of cytoplasm that is not separated into individual cells
What is the major role of protonephridia in rotifers?
To maintain water balance and body volume
What organs are needed for excretion take place in rotifers?
Protonephridia with flagella force fluid to the bladder which leads ot the cloaca
How does excretion in rotifers work?
Water continually diffuses into the animal across the permeable body surface
What are the defining characteristics of the phylum acanthocephala?
- 1) 1-2 large, acellular, collagenous sacs in the pseudocoel, supporting the gonads
- 2) Adults with proboscis containting intracellular hooks
Are acanthocephalans free-living or parasitic?
Acanthocephalans are all parasites
Species with seperate male and female sexes
What is a proboscis?
A hardended fluid-filled structure bearing hooks and spines used to attach to the acanthocephalans host
What is the specialized pouch that houses the probosicis?
The proboscis receptacle
Why don't acanthocephalans have digestive tracts?
They do not need them because their host digests their nutrients for them
Decribe the acanthocephalans reproductive structures found in both sexes
The gonads are contained within 1 or 2 thin-walled ligament sacs that extend from the posterior end of the proboscis receptacle to near the genetal pore, essentially subdividing the pseudocoel.
Decribe the acanthocephalans reproductive structures found in males
Males bear conspicuous cement glants, whose cement hardens after copulation, securely plugging the female's vagina
Decribe the acanthocephalans reproductive structures found in females
Mature females have no well-defined ovary. Instead the ovary fragments as it matures, forming numerous ovarian balls that float freely in the ligament sac fluid. Mature eggs enter the uterus by way of a posterior uterine bell that prevents immature eggs from leaving the ligament sac.
Describe the acanthocephalan reproductive cycle
- Internal fertilization takes place
- The eggs develop in the female's pseudocoel to the acanthor stage
- Ancanthor exits the host via host fecal matter encased in protective shells
- Ancanthor's are eaten by an invertebrate host and develops to an infective stage within that host
- The host is eaten by another invertebrate host called the transport host and no further development occurs
- The transport host carries the infective ancanthor until the host is eaten by a suitable vertebrate host where the ancanthor reaches adulthood
What are the defining characteristics of the phylum nemerta
Have a muscular eversible proboscis housed in a fluid-filled, schizocoelous cavity called the rhynchocoel
What is a nemertean?
An unsegmented, soft-bodied worm
What environments do nemerteans live in?
Many species live in marine, one genus lives in freshwater, a few species live in tropical, moist terresterial environments
How are nemerteans similar to turbellarians?
- 1. acoelomates
- 2. flattened dorsoventally
- 3. move via external cilia embeded in mucus layer and pedal waves
- 4. circular, longitudinal, and dorsoventral muscles are present
- 5. have a ladder like arrangement of longitudinal nerves
- 6. pigmented photoreceptors
- 7. Statocysts
- 8. Intracelluar digestion
- 9. Protonephridia
How are nemerteans different from turbellarians?
- 1. molecular evidence suggests no recent common ancestor
- 2. Nemertea have true circulatory systems, complete digestive tracts, muscular eversible proboscis housed in a fluid-filled cavity called a rhynococoel
What are statocysts?
An organ used for balancing
Loosely-packed tissue filling the spaces between the organs in lower animals such as flatworms
How is the rhynchocoel formed?
During development a split in the mesodermal tissue forms the rhynchocoel
How does a nemertean's circulatory system work?
There are well-defined contractile vesicles but no true heart and no one-way valves. Blood circulates multi-directionally and a few species have hemoglobin.
How does the nemertean digestive system work?
Their digestive system moves in one direction with a mouth and an anus. Food is moved by cilia and enzymes breakdown food in the intestinal wall between the mouth and the anus. The nutrients are then distributed by the circulatory system.
What happens when the muscles contract around the rhyncocoel
Fluid is displaced causing the proboscis to turne inside out
How do nemerteans reproduce?
Most are gonochoristic, but a few are hermaprhodites. External fertilization is used but asexual reproduction by fission or fragmentation is uncommon.
What does it mean to be protandric?
Males progress to female as they age
What are the defining characteristics of the phylum mollusca?
- 1) Dorsal epithelium forming a mantle which secretes calcareous spicules or one or more shells
- 2) Cuticular band of teeth (radula) in the esophagus, used for feeding
- 3) Ventral body wall muscles develop into a locomotory or clinging foot
How are do molluscs affect the economy?
They are used for food and their shells. They are also cause of vessel, dock and garden damage.
What type of mollusc has a one piece shell?
What type of mollusc has 2 equally sized shells?
What type of mollusc has 8 transverse shells?
What types of molluscs have reduced or absent shells?
Cephalapods and some gastropods
What are the three layers of the molluscan shell?
(Outside -> Inside) Periostracum, Prismatic, and Nacreous Layers
Describe the Periostracum
The outermost layer of the shell that consists of a thin, horny layer made of conchiolin and grows only at the shell margin
Describe the Prismatic Layer
The middle layer of the shell that consists of calcit prisms surrounded by conchiolin that only grows at the margin of the shell
Describe the Nacreous Layer
The innermost layer made up of calcium carbonate surrounded by a protein that is deposited as sheets parallel to the surface. This layer is deposited continuously
What are the 5 main classes of the phylum mollusca?
Describe the body plan of the members in the phylum mollusca
- mantle cavity
- visceral mass
Describe a molluscs foot
consists of a highly muscular foot that is ventral in position
Describe the molluscs head
contains the mouth, specialized sensory organs, and a radula
What is a radula?
A rasping, potrusible feeding organ unique to mollusks
What is the radula made of?
a firm ribbon of chitin and protein
What is the odontophore?
A supportive underlain cartilage-like structure found under the radular sac
What does the radula consist of?
2 rows of sharp chitinous teeth produced from the radular sac
What is the function of the mantle cavity?
Houses the comb-like molluscan gills and serves as the exit site for the excretory, digestive, and reproductive system.
Gills used in respiration and/or feeding
A chemoreceptor/tactile receptor generally located adjecent to the ctenidium
What is countercurrent exchange?
It is a system that greatly increases the efficiency of gas exchange between blood flowing within the ctenidial filaments and the water flowing over them
How does countercurrent exchange work?
Blood and water flow in opposite directions
What is unique about the class polyplacophora?
Shell forms as a series of 7-8 separate plates
Describe a polyplacophorans sensory system
They have no statocysts, tentacles, or eyes
Describe the polyplacophoran's nervous system
It is simple and ladder-like with poorly developed ganglia
What do members of the class polyplacophora use to digest their food and what do they typically eat?
Most are herbivores possessing sugar glands that release amylase into the stomach
Describe a polyplacophorans shell
It has 8 overlapping, articulating plates that are either partially or wholly covered by the mantle
What is the largest and most diverse molluscan class?
What is an example of a member of the class polyplacophora?
What are examples of the members of the class gastropoda?
Snails and Slugs
True or false: Gastropods only live on land and eat a limited varity of food because they have very specialized feeding modes
False: Gastropods live in a wide range of habitats and exhibit a wide range of feeding modes
What is the purpose of the columellar muscle?
It attaches the animal to the shell
What is an operculum?
A hard flap on the foot that serves as a cover for the opening of the shell when the gastropod's body is retracted
What are the defining characteristics of the class gastropoda?
- 1) Visceral mass and nervous sysstem become twisted during embryonic development
- 2) Have a proteinaceous shield on the foot
Describe the position of a gastropod's shell
It leans to the left side of the body, balancing the center of mass over the foot
How can a dextral shell appear sinistral?
by coiling up the central axis rather than down the central axis
What happens to the right side of the body in a dextrally coiled shell?
Ctenidium, csphradium, nephridium and heart auricle may be reduced or absent
a counterclockwise 180 degree twisting of the head and foot relative to the shell, mantle and rest of the body during early development
When does torsion occur?
occurs in developing gastropod embryo or larva
What is the adaptive significance of torsion
- The center of gravity is forward so animal is more stable
- Ctenidia headed into current
- Osphradia positioned in direction of locomotion