Lecture 7 DA Flashcards
How does cleavage differ between protostomes and deuterostomes?
Protostome - cleavage is spiral and determinate.
Deuterostome - cleavage is radial, and indeterminate.
If a cell was taken from a 4-cell zygote of a protostome and deuterostome, what would each form?
Protostome - could form a quarter of a non-viable organism.
Deuterostome - could form a complete embryo, as in homozygotic twins.
What is the plane of cell division in protostomes and deuterostomes?
Protostomes - diagonal to the vertical axis of the cell.
Deuterostomes - perpendicular or parallel to the vertical axis of the cell.
What is the difference between schizocoely and enterocoely development of the coelom?
Schizocoely - solid mass of mesoderm splits, and the cavity forms the coelom.
Enterocoely - coelom buds off the main cavity, to form the coelom.
What is the major group of deuterostomes?
Phylum echinodermata.
Where do phylum echinodermata live?
Exclusively marine.
What are the classes of phylum echinodermata (6)?
Asteroid Ophiuroidea Echinoidea Crinoidea Holothuroidea Concentricycloidea
Are premetamorphic echinoderms generally bilateral or radially symmetrical? What about postmetamorphic? What does this suggest?
Premetamorphic are generally bilateral, while postmetamorphic are pentamerous with radial symmetry.
Suggests radial symmetry is secondary.
What kind of skeleton do echinoderms have, and what does it develop from? Where is it located? Is it unique?
Have an endoskeleton of hard calcareous plates, and develops from the mesoderm. Located within the body wall. Unique to invertebrates.
What is mutable connective tissue?
Allows them to break off their arms.
What are the skeletons of echinoderms covered by?
Epidermis and cuticle.
What is the water vascular system of echinoderms formed by?
A canal close to the body wall, lined with ciliated epithelium, filled with fluid, similar to sea water, but with coelomocytes, proteins and a high K+ concentration.
What is the water within an echinoderm’s water vascular system like (4)?
Similar to sea water, but with coelomocytes, proteins and a high K+ concentration.
In the water vascular system, what surrounds the oesophagus/mouth?
Ring canal.
What two organs may be attached to the ring canal, and what do they do?
Tiedmann’s bodies, used for defence.
Polian vesicles, used as fluid storage organs.
What do canals within the water vascular system connect to?
Ampullas.
What is found on the aboral side of echinoderms?
A button shaped ossicle, called a padreoporite.
What is the vertical canal in echinoderms?
Canal connecting the madreporite to the ring canal. Also called stone canal.
From where is the echinoderm’s water vascular system connected with sea water?
Through the madreporite.
What are radial canals?
Canals that extend from the ring canal into each arm tip of the echinoderm.
What are lateral canals?
Canals that extend laterally off radial canals in the arm tips, and connect to ampullas.
What is the purpose of an ampulla in echinoderms?
Squeeze to move water around.
What can be found on each lateral canal (2)?
A valve, as well as a podium under the ampulla.
Is the ampulla outside the coelum?
No, within it.
How do amulla contract, and what effect does this have?
Muscle fibres lie within the podia and ampulla walls, and are antagonists.
To extend podia, ampulla contracts, and podia relaxes.
Vice versa to retract podia.
Where are the gonads and gut tract of echinoderms found?
Either side of the lateral canal.
Guts can be found above the gonads.
What are the functions of podia (5)?
Feeding Burrowing Locomotion Sensory perception Respiration
How do mutable connective tissue work?
Can change stiffness according to the situation, from rigid to flexible.
Does mutable connective tissue become rigid or flexible when being lost to a predator?
Softens, and depolymerisation occurs.
Are echinoderms mono- or dioecious?
Most are dioecious, but some are hermaphrodites.
Where does fertilisation occur for echinoderms?
External.
What is the egg of an echinoderm called, and what is it like?
Homolecithal egg, with the yolk uniformly distributed.
Is the blastula of a homolecithal egg of echinoderms ciliated? What is the blastocoele like?
Blastula is ciliated, contains a large blastocoele.
What happens before invagination into a blastocoele in echinoderm eggs?
Cells from a vegetal pole divide before invagination.
What are the modes of development for an echinoderm (3)?
-Planktonic Feed on plankton -Lecitotrophic Do not feed, utilise yolk -Brooded Premetamorphic develop in an invagination in mother's abdominal wall.
What is the most common echinoderm developmental mode?
50% are lecitotrophic.
How long do the modes of development last typically?
Brooding and planktonic last several months while lecitotropihc is several days.
What kind of symmetry do echinoderm larva have?
Bilateral.
Are echinoderm larva ciliated?
Yes, ciliated band surrounds the mouth.
What feature do each of the echinoderm class larva have?
- Echinoid and ophiuroid - long slender projections with a skeletal rod.
- Asteroid and holothuroid - short arms.
- Crinoid - no projections, lecitoprophic.
What do larva metamorphose into? Where does this form develop structures?
Radial juvenile.They develop structures mainly from the left side.
How do radial juveniles anchor to substrata?
Primary podia of juveniles protrude from the left side, test the substratum with cehmoreceptors, dettach from a stalk, and begin a seperate life.
What is the most ancient and primitive echinoderm class?
Crinoidia.
Are crinoidia sedentary?
They can be stalked or free living.
What is the main structure of crinoidia like?
Cuplike, with 5 arms, and up to 200. On the side of the arms are pinnules, rows of jointed appendages.
What is the aboral side of crinoids? How do they stand?
Calyx. Stands on a stalk, connected to a calyx, and on cirri in comatulids.
Can crinoids move?
No, but can flex and extend., Some can crawl of cirri.
How do crinoids feed?
Suspension feeding, filtration fan formed by pinnules. Podia and pinnules bear mucus secreting papillae.
Where is the mouth and anus of crinoids?
Mouth is upward, as is the anus.
What are ambulacral grooves?
5 grooves found in crinoids that extend peripherally from mouth to arms.
Where are crinoid podia located?
Either side of pinnules.
What mode of development do crinoids have?
Either brooders or lecitophores.
Where are gametes made in crinoids?
In the arms.
What is the structure of class asteroidea?
Star shaped, and composed of arms projecting from a central disc, 5-40.
Where is the mouth of an asteroidea located?
Centre of the central disc.
Do asteroidea have ambulacral grooves?
Yes.
What can be found on the ambulacral grooves of asteroidea?
2-4 rows of podia.
What is the sensory podia?
Found in asteroidea, is the podia found at the tip of the arm.
Do asteroidea have pigment spots?
Yes.
What is a pedicellariae in asteroidea, and what is its purpose??
Jaw-like appendages, a stalk surmounted by ossicles arranged to form a forceps/scissors, used to catch prey/defence.
What are papulae of asteroidea?
Evaginations of epithelia and mesothelia, increasing respiratory surface area.
Is the water vascular system of asteroidea involved in locomotion?
Yes, walks on podia, attaches to substrata.
How do asteroidea podia attach to substrata?
Mostly chemical, some use physical.
Do all asteroidea have podia with suckers?
No, some species lack them.
The asteroidea stomach is divided in two, pyloric and cardiac. What does the pyloric chamber lead to?
2 pyloric caeca, digestive glands in each arm.
What does the short intestine of asteroidea lead to?
Opens to 2 intestinal/rectal caeca.
How do asteroidea digest food?
Move food through gut by beating cilia, not peristalsis.
How do asteroidea eat?
Swallow prey whole, expell indigestibles.
Some evert their stomach, and digest extracellularly.
How do some asteroidea evert their stomach?
Contract body ball, pressurising the coelomic fluid, forcing stomach out.
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