Lecture 16 + 17 Flashcards
Echinodermata
Q: What clade does Deuterostomia belong to?
Bilateria groups.
What embryonic development process is associated with Deuterostomia?
A: Deuterostome embryogenesis.
What are the synapomorphies of Deuterostomia?
Radial cleavage, regulative (indeterminate) development, the fate of blastopore (anus first, mouth second), gill slits on pharynx , and coelom formation (enterocoelous)
Which phylum within Deuterostomia is known as Ambulacraria?
Echinodermata.
What key feature is absent in living echinoderms?
Gill slits.
What are the living groups within Phylum Echinodermata?
Crinoidea, Asteroidea, Ophiuroidea, Echinoidea, and Holothuroidea.
What features define the stem groups of echinoderms?
Stem group A: motile, bilateral with gill slits. Stem group B: asymmetric, stalked with gill slits.Stem group C: stalked, beginnings of radial symmetry, and probable loss of gill slits.Stem group D: attached suspension feeders with ambulacral grooves.
What are the five autapomorphies of echinoderms?
Pentaradial symmetry, calcareous endoskeleton, water vascular system, pedicellariae, and dermal branchiae.
What is the water vascular system in echinoderms used for?
Respiration, excretion, locomotion, and feeding.
What structure in echinoderms allows water into the water vascular system?
Madreporite.
What are tube feet used for in echinoderms?
Movement and feeding.
What are pedicellariae and their functions?
Small spines with jaws used for cleaning, food capture, and defense.
What are dermal branchiae (papulae) used for?
Respiration through thin-walled projections of the coelom.
What is unique about echinoderm nervous systems?
They lack a brain or ganglia but have nerve rings, radial nerves, and an epidermal nerve net.
How do echinoderms reproduce?
Typically through external fertilization, where sperm and eggs are released into the open water.
How does regeneration work in echinoderms?
Echinoderms can regenerate from as little as 1/5 of the central disk and one arm.
What is autotomy in echinoderms?
The deliberate shedding of body parts as an escape response or to replace infected or damaged appendages.
What is an example of fragmentation in echinoderms?
Linckia “comets” can cast off an arm that will grow into a complete starfish.
What is the common name for species in Class Asteroidea?
Sea stars, starfish (“star form”)
What structure characterizes the body of a typical Asteroidea?
A central disc with 5 arms (can have 7 arms or almost 50
What is unique about the Asteroidea stomach?
They have a two-part stomach and can evert the cardiac stomach to feed.
How do sea stars feed?
They are scavengers and carnivores but can also suspension feed.
What are two examples of keystone species in Class Asteroidea?
Pisaster ochraceus (purple intertidal sea star) and Stichaster australis (reef sea star).
What is sea star wasting disease associated with?
Warmer temperatures and densovirus, causing white lesions, limp bodies, fragmentation, and death.
How do Ophiuroidea move?
With flexible articulated arms and closed ambulacral grooves.
What is absent in Ophiuroidea that is present in other echinoderms?
Pedicellariae, papulae, and suckers on tube feet.
Where is the madreporite located in Ophiuroidea?
On the oral side.
What is the “hedgehog form” in echinoderms?
Echinoidea, including sea urchins, sand dollars, and heart urchins.
What is notable about their regeneration and habitat?
They are fragile with remarkable regeneration and are cryptic, staying away from light in dark places.
What structure do sea urchins have for movement?
Tube feet assisted by spines in socket joints (unique)
What is Aristotle’s lantern and its function?
A structure with 5 teeth used for chewing, especially in sea urchins.
How do Echinoidea impact kelp forests?
They can create “urchin barrens” by consuming kelp forests entirely.
What is the “obscure form” in echinoderms?
Holothuroidea (sea cucumbers).
What is the function of the oral tentacles in Holothuroidea?
Suspension or deposit feeding, located at one end of the body.
How are Holothuroidea elongated?
Along the oral-aboral axis (like a stretched-out sea urchin).
What unique respiratory structure do sea cucumbers have?
The respiratory tree, which is connected to the cloaca.
How do sea cucumbers defend themselves?
By eviscerating their Cuvierian tubules, respiratory tree, or guts.(puking their guts out)
What is the form of Class Crinoidea?
“Lily” form, including sea lilies and feather stars.
How do Crinoidea move?
Sea lilies are attached to the substrate, while feather stars can crawl, sweep, or swim via cirri or feathery arms.
Where is the mouth located in Crinoidea?
On the oral side, alongside the anus.
What environments are Crinoidea commonly found in?
Many live in deep waters, though there is high diversity in shallow Indo-Pacific and West Indies waters.
What do Hemichordata have in common with other deuterostomes?
Gill slits and a 3-part coelom.
What is the stomochord in Hemichordata?
An evagination of the mouth cavity, not homologous with the chordate notochord.
What do acorn worms use for feeding?
Mucus on their proboscis to collect food as deposit or suspension feeders
What are Pterobranchia characterized by?
Small, tube-dwelling, mostly colonial, and exclusively marine species.
How do Pterobranchia feed?
They are suspension feeders, using a crown of tentacles with coelomic extensions.
what are the Classe in Phylum Hemichordata?
Class Enteropneusta and Class Pterobranchia
what are the class in Phylum Echinodermata?
Class Asteroidea, Class Ophiuroidea, Class Echinoidea, Class Holothuroidea, and Class Crinoidea
