BI256 Lecture Notes - Lecture 22: Water Vascular System, Symmetry In Biology, Pedicellaria
Document Summary
Characteristics: echinodermata free-living larval stages exhibit bilateral symmetry. Calcareous endoskelton (either as plates or scattered ossicles) Most with no ability to osmoregulate (so avoid brackish water) Characteristics:phylum echinodermata most adults exhibit 5-point (pentamerous) radial symmetry. Pedicellariae i. e. minute pincer-like structures on the outer surface of many members of this phylum. Dermal branchiae (papulae) i. e. projections of the coelomic cavity with respiratory & excretory function. A mesodermal spiny endoskeleton of plates or ossicles (sometimes spiny) Body surfaces designated oral (bearing mouth) or aboral. Consist of 2 3 calcium carbonate ossicles (valves) Ends can be moved apart and together by small muscles. Capture of live prey fluid-filled canals leading to tube feet together with dermal ossicles form a hydraulic system. Dermal branchiae are projections of the coelomic cavity covered with epidermis and lined with peritoneum. Ciliary action moves fluids in opposite direction (countercurrent) Have a central disc with tapering arms extending outward.