Deuterostomes Flashcards
Define Deuterostomes?
Triploblastic, true coelomate animals with internal skeletons.
What are the 3 main clades of Deuterostomes?
Echinoderms (Sea stars, sea urchins), Hemichordates (Acorn worms and pterobranchs), Chordates (Sea squirts, lancelets and vertebrates)
What developmental patterns do Deuterostomes show?
Blastopore becomes the anus and mouth forms on opposite side, coelom develops from mesodermal pockets that bud off from gastrula cavity, radial cleavage, indeterminate cleavage.
What is radial cleavage?
Cells cleave parallel or perpendicular to animal – vegetal axis.
Cells lie beside and on top of each other.
What is Indeterminate development?
Cells separated after first divisions still develop into complete embryos
Identical twins
What are traits common of Echinodermata?
Radial symmetry as adults, bilateral symmetry as larvae, pentardial symmetry, calcified internal plates, loss of pharyngeal silts. Ciliated larvae.
What is the typical Echinodermata body plan?
No head, move equally well in many directions, oral side containing the mouth and aboral side containing the anus.
List some characteristics of echinodermata?
Pelago-benthic life cycle, reproduce mostly sexually, generally dioecious, external fertilisation, splitting (transverse fission) parthenogenesis, autotomy and regeneration of parts, no specialised excretory organs in adults.
What two evolutionary innovations do Echinodermata posses?
Endoskeleton, internal and calcified skeleton.
Water Vascular System.
Describe the Sea Urchin Endoskeleton?
Endoskeleton beneath epidermis, composed of small calcareous plates “ossicles”.
Skeletal plates connected by collagen which can be stiff or flexible “catch collagen”.
Unique mechanical support which controls body without muscles and holds posture.
What is the water vascular system?
Network of water filled canals leading to extensions (tube feet)
What is the function of the WVS?
forms hydraulic system for locomotion, gas exchange and feeding.
How does the WVS work?
Due to water pressure, water enters through the madreporite, which is connected to the ring canal around the esophagus, then into the rays through radial canals, and finally into the tube feet.
How do tube feet work?
Lack circular muscles, fluid pumped into foot by contraction of ampulla, one-way valve at junction of ampulla/radial canal, tube foot retracts when longitudinal muscles in each tube foot contract.
What belongs to Asteroidea?
Sea Stars (regenerative powers, predators, gonads and digestive organs located in arms, Everts stomach)
What is Macrophagous feeding?
When the stomach is everting externally.
What is the function of Pedicellariae in Sea Stars?
Keep body surface clear of algae in conjunction with the ciliated epidermis present present in all echinoderms.
What are Pedicellariae?
a defensive organ like a minute pincer
How do Pedicellariae work?
Possess movable vesicles and opening and closing muscles.
What mechanisms of defence do Echinodermata possess?
Thorns, sometimes with neurotoxins.
What belongs to Echinoidea?
Sea Urchins and Sand Dollars.
What are common characteristics of Echinoidea?
Spherical, free living, lack arms & appendages, posses spines (movable for locomotion & contain toxins for defence), pedicellaria, Catch plankton with their tube feet or scrape algae from rocks with a rasping structure
What is unique of Aristotle’s Lantern?
Composed of 50 skeletal elements; worked by 60 muscles, 2 powerful blocks of muscle between pyramids close jaws and provide strong biting action.
What belongs to Crinoidea?
Sea lilies, feather stars
What are common characteristic of Crinoidea?
Sea lilies attach to substrate by a stalk
Feather stars grasp substratum with flexible appendages allowing limited movement
Tube feet ONLY for food collection, gas exchange & excretion
What belongs to Ophiuroidea?
Brittle stars, Basket Stars
What belongs to Holothuroidea?
Sea Cucumber
What features are common of Sea Cucumbers?
Scavengers, soft-bodied, lack arms, bilateral symmetry, anterior tube feet, unique defence.
What unique defence do sea cucumbers possess?
Some expel cuverian tubules (sticky/toxic) or evisceration (entire digestive system expelled)
How are the tube feet of sea cucumbers specialised?
Modified into feathery, sticky tentacles that protrude from the mouth.
Recap the evolutionary innovations of Echinodermata?
WVS for locomotion, feeding, excretion & respiration
Endoskeleton – internal calcified skeleton, with catch collagen for unique mechanical support, • Regeneration, defence (spines, pedicellaria, eviseration), grazing apparatus, macrophagous feeding
