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Echinoderms, Hemichordates, Deuterostomes, Phylum Chaetognatha, Clade Ambulacraria, Water Vascular System, Endoskeleton, Calcareous Ossicles, Free Swimming Larvae. Above mentioned terms and points represent this lecture of general zoology course. A full series of lectures can be found in my documents.
Typology: Slides
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Deuterostomes
Deuterostome characteristics: Radial, indeterminate cleavage Formation of the mouth from a second opening Enterocoelous coelom development Chaetognaths are placed outside both protostome & deuterostome groups.
Clade Ambulacraria
Echinodermata and Hemichordata
Phylum Echinodermata
Echinoderms include sea stars, brittle stars, sea urchins, crinoids, sea cucumbers. Entirely marine Lack ability to osmoregulate. Almost entirely benthic. Nonsegmented.
Phylum Echinodermata –
Characteristics
Spiny endoskeleton of plates Water vascular system Pedicellariae Dermal branchiae (skin gills) Pentaradial symmetry in adults
Phylum Echinodermata - Symmetry
Echinoderms are bilaterally symmetrical as larvae. This means their ancestors were bilaterally symmetrical.
Phylum Echinodermata - Symmetry
Many are still radial. Some have again become superficially bilateral (skeletal & organ systems still pentaradial). Sea cucumbers. A few sea urchins.
Phylum Echinodermata -
Deuterostomes
Radial, indeterminate cleavage. Enterocoelous – the mesoderm lined coelom develops from outpocketing of the primitive gut. Formation of the mouth at the end of the embryo opposite the blastopore.
Water Vascular System
The water vascular system opens to the outside through small pores in the madreporite.
Water Vascular System
Canals of the water vascular system lead to the tube feet. Tube feet may have suckers, allowing the echinoderm to move while remaining firmly attached to the substrate – important in areas with lots of wave action.
Development
Eggs (which may be brooded or laid as benthic egg masses) hatch into bilateral , free-swimming larvae. The type of larva is specific to each echinoderm class. Class Asteroidea Bipinnaria Brachiolaria Class Ophiuroidea Ophiopluteus Class Echinoidea Echinopluteus Class Holothuroidea Auricularia Class Crinoidea Doliolaria
Development
Metamorphosis involves a reorganization into a radial juvenile. Left/right becomes oral/aboral.