BIO 469 Lecture Notes - Lecture 2: Sensu, Deuterostome, Entoprocta
13 Jun 2018
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Bilateria and Lophotrochozoa
● Chiton (Mollusca)
● Sally lightfoot crab
Bilateria
● Deuterostomia (Echinoderms, chordates)
Lophotrochozoa
● Protostomia (Mollusks, annelids, arthropods)
Not all protostomes under protostomia
● Eight cell stage, spiral and determinate
● Mouth develops from blastopore
Not all deuterostomes undergo deuterostomia
● Eight cell stage, radial and indeterminate
● Anus develops from blastopore
Bilateria are now divided into 3 major clades
1. Deuterostomia
2. Lophotrochozoa
a. Lophomore
b. Trochophora larvae
c. SPIRALIA (Spiral Cleavage- still under discussion)
3. Ecdysozoa
Lophophore (Ectoprocta/Bryozoa, Brachiopoda/Phoronida)
● Feeding organ made of a ring of ciliated tentacles surrounding the mouth
● Hollow tentacles, extension of the coelom
● Suspension feeders
●
Trochophora larvae (Nemertea, mollusca, annelida (sensu lato), entoprocta, cycliophora)
● Two bands of cilia around the body (prototroch)
● Often apical tuft related to an apical sense organ (eye and cerebral ganglia)
● Sometimes, perianal ciliary gland
● Sometimes, oceli, statocyst, larval protonephridia
● Quite complex
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Document Summary
Bilateria are now divided into 3 major clades: deuterostomia, lophotrochozoa, lophomore, trochophora larvae, spiralia (spiral cleavage- still under discussion, ecdysozoa. Feeding organ made of a ring of ciliated tentacles surrounding the mouth. Trochophora larvae (nemertea, mollusca, annelida (sensu lato), entoprocta, cycliophora) Two bands of cilia around the body (prototroch) Often apical tuft related to an apical sense organ (eye and cerebral ganglia) Darwin; remarkable for the obscurity of their affinities . Nervous system has an anterior dorsal fused ganglia. No circular muscles in the body wall. Many of the deuterostome-like features of the chaetognaths are likely bilaterian symplesiomorphies rather than derived features. Plesiomorphy; the original state of the character. Symplesiomorphy; an ancestral trait that is shared by 2 or more taxa that have an earliest common ancestor in common. Remarkably plastic genome with high mutation rates. But, strong morphological conservation of the phylum. Same structure for the last 500 million years. Strictly marine; mostly planktonic but 20% benthic.
