BIOL 3454 1nd Edition Lecture 26Lecture 11/19I. Chaetognaths, Echinoderms, HermichordatesII. Mixed characteristics a. Not all taxa are protostome or deuterostome features b. Chateognaths mixed III. Chinoderms have a strange body plan a. Bilateral ancestor and radial as adults b. Coelom modified into a water vascular system for movement c. Free moving but radialIV. Phylum Chaetognathaa. Arrow wormsb. Roots Greek: chaite = long flowing hair/gnathos = jawc. All marine d. Swim to surface at night and descend during the daye. Predatoryf. Form and function i. Unsegmented ii. Body plan: head, trunk and postanal tail iii. Vestibule – depression beneath the headiv. Dorsally located eyesv. Only invertebrates with a many layer epidermisvi. Highly mobile and nearly transparent can have significant ecological impactvii. Complete digestive system and well developed coelom viii. U-shaped ciliary loop over neck and from back of head (mechanoreceptive or chemosensory) ix. No respiratory or excretory systems x. Hermaphroditic (self or reciprocal cross fertilization)xi. Deuterostomes but share characteristics with both groups of phylaV. Phylum Xenoturbellidaa. Hard to place taxonomy b. Deuterostomesc. Single genus with 2 species d. Live in N sea mud e. Feed on bivalves and bivalve eggsf. Sexual reproduction with no structured gonadsVI. Phylum Echinodermataa. Water vascular system of coelomic origin that doubles as part of respiratory system b. Unsegemented with pentraradial symmetry c. Triploblastic and coelom extensive d. Endoskeleton of dermal calcareous ossicles These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.e. Digestive system usually complete axial or coiled f. Bo brain but extensive nerve ring g. Regeneration prominent h. Asexual reproduction by fragmentation i. Separate sexes, free swimming, bilateral larval stages j. Excretory organs absent k. Blood vascular system very reduced l. Circulation by peritoneal ciliam. Fossil record to Cambriann. Bilateral ancestor but evolved radiality (slow and sessile)o. Most have no ability to osmoregulate p. Virtually all bottom dwellers a few pelagicq. Important to knowledge of evolution and development r. Class Asteroidea i. Starfish ii. ~1500 species iii. Predatory iv. Central discs with tapering armsv. Covered with ciliatd pigemented epidermisvi. Mouth that is surrounded by a soft membrane with a canal running from the mouth to the end of each arm vii. Form and function 1. Aboral surface usually rough and spiny 2. Bases around spines have pincer like pedicellariae3. Papulae – soft delicate gill structures 4. Madreporite – tiny pore on the aboral side leading to the water cascular system 5. Endoskeleton made of small calcareous plates called ossicles bound together with connective tissue 6. Collagen is called catch collagen and under neural control and can change from a liquid to solid state 7. Ossicles have a meshwork between them called stereom unique to echinoderms viii. Water vascular system 1. Primary functions – locomotion and food gathering 2. Operates hydraulically 3. Madreporite to stone canal to ring canal to several radial canals to manylateral canals to tube feet with end in an external sucker ix. Digestive system 1. Mouth on oral side leads to a short esophagus to a large stomach in central disc lower part of stomach can be everted during feeding 2. Upper pyloric part of stomach is smaller and connects to pyloric ceca in each arm 3. Short intestine leads to small intestinal ceca anus inconspicuous may be absent 4. Like to eat other echinoderms and molluscs and bivalves5. Few feed on plankton x. Nervous system made of 3 units 1. Oral or ectoneural – nerve ring around mouth and a redaila nerve in each arm 2. Deep or hyponeural – lies aboral to ectoneural system ring around anus and radial nerves along roof of each ray 3. Epidermal nerve plexus or nerve net – connects the two systems along with bodywall 4. Sense organs are not well developed 5. Ocellus at end of each arm xi. Reproductive system 1. Separate sexes2. Fertilization external (eggs and sperm shed into water)3. Can regenerate lost parts 4. Many require lest part of central discs to regenerate 5. Larvae = bipinarria6. Then brachiolaria as they start to mature xii. Sea daisies 1. Highly modified asteroids 2. Pentaradial but no arms3. One species with no digestive tract just a membranous velum that absorbs nutrients s. Class Ophiuroideai. Brittle stars ii. 2,000 species very abundant iii. Arms slender and don’t really taper iv. No peicellariae or papulaev. No suckers on tube feet vi. Madreporite on oral surface vii. Ampullae absent from podia force for motion exerted by muscles viii. Form and function 1. Each arm a column of articulated ossicles connected by muscles and covered by plates2. 5 movable plates surrounding mouth act as jaws 3. No anus stomach saclike no intestine 4. Organs mostly confined to disc5. 5 bursea or inpocketings serves as site for gas exchange also contain gonads that discharge mature gametes into bursae6. Separate sexes but a few hermaphroditic some brood young bursae7. Most have a free swimming larvae called a ophiopluteus 8. Water vascular system similar to Asteroids ix. Natural history 1. Secretive nocturanal (usually live in rock cracks)2. Strongly light sensitive bc of special nerve structure son aboral side3. Many filter feeders some highly predatory 4. Very good at regeneration will release arms to placate an attackert. Class Echinoideai. ~950 species ii. Sea urchinsiii. Distributed everywhere marine iv. Almost all have a complete body with an endoskeleton called a test v. Most hermispherical radially symmetrical medium to long spines move by tube feet vi. Some sand dollars are secondarily bilateral small spines that are used for locomotion vii. Form and function 1. Test is generally 10 double rows pf plates 2. 5 plates of ambulacral rows that are homologous to those in asteroids have pores where tube feet extend 3. Spines move by small muscles at base 4. Several kinds of pedicellariae usually 3 jawed forms on long stalks keep body clean some bear venom glands 5. Inside test is a specialized digestive structure 6. Aristotles lantern is where teeth are attached for rasping 7. Ciliated siphon connectes espphagus directly to intestine to concerntrate food 8. Hemal and NS similar to Asteroids 9. Have small gills but most gas