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Unformatted text preview: Phylum Echinodermata Phylum Echinodermata
sea stars, urchins, sand dollars, cucumbers, etc. All classes share many traits (why they are in a single Phylum!!!) Some classes will be used to illustrate these general traits - because they are general because best illustrated with that group best 5 Classes Asteroidea - sea stars Ophiuroidea - brittle stars Echinoidea - urchins and sand dollars Holothuroidea - sea cucumbers Crinoidea - sea lilies, feather stars Other traits are specific to particular classes If you are confused about general vs If specific traits, ASK!! specific All marine
~6,000 Living Species Internal skeleton Calcarious ossicles Loose or fused - Test Major body cavity Coelom Enterocoely No excretory organs diffusion Water - Valscular System Water derived from the coelom Dioecious External Fertilization Development - can be direct or indirect Indirect each class with characteristic larva Larvae - bilateral Asteroid Ophiuroid Deuterostomes Enterocoely Radial Cleavage
Echinoid Holothuroid 1 Bilateral Larva Radical Metamorphosis Adults 2º Radial Symmetry Radial Adult – 5 part symmetry Oral surface - mouth Aboral surface - opposite mouth Multi part coelom - larvae 3 part: AXOCOEL – in Adult forms watervascular system stone canal, ring canal, etc. HYDROCOEL – in Adult forms watervascular system – stone canal, ring canal, etc. SOMATOCOAL - in Adult Perivisceral coelom Class Asteroidea – Adults Adults may have more ceolomic may spaces spaces See your text - the author See is an expert on echinoderm coeloms and excretion coeloms and
sea stars Pentamerous (5 part symmetry) Oral surface against substrata Arms = Rays
Aboral surface Oral surface Grow with food de-grow without food Excellent powers of regeneration 2 Body Epidermis covers entire outside
Ossicles – calcium carbonate
fused or loose Form INTERNAL skeleton Asteriodea Internal skeleton Calcarious ossicles Can be fused, many loose give structure Bound by connective tissue and muscles Dermal branchia Dermal branchia Cilia Spine Pedicellariae Ossicles form structures on surface Ossicles form e.g., paxillae, pedicellaria e.g., paxillae pedicellaria mounted on stalks consist of several ossicles consist ossicles Keep small organisms from settling on surface Water - Valscular System and Tube Feet Water derived from the coelom External features: Ambulacral groove Ambulacral down each ray from mount Anus - aboral Anus Madreporite Sieve like opening to watervascular system 3 Water Vascular System
from 2 parts of coelom - axocoel & hydrocoel ciliated epithelium canal system into each ray Madreporite => STONE CANAL => RING CANAL TIEDMANN’S BODIES - Polian Vesicles Radial Canals Lateral Canals – valved AMPULLA, TUBE FOOT - 2-4 rows/ARM - Hydrostatic extension - Sucker, adhesives - bending – muscles - nervous system control – radial nerves Ambulacral groove groove down each ray from mount Tube Foot 2-4 rows / arm Tube Foot 2-4 rows / arm each tipped with a sucker controlled by muscles 4 Hydrostatic extension
sucker - muscles mucus acts as attachment Bends - muscles nervous system control (radial nerves) Tube foot with Tube ampulla (compensation ampulla (compensation bulb) attach to lateral canal which then attaches to radial canal in each arm radial nerve down each arm controls system at any one time ~10 - 20% of feet in contact at Lateral canals all join the join Ring Canal Ring Ring canal connected by Stone Canal to to Polian Vesicle Polian compensation sac located on ring canal Tiedemann’s bodies Tiedemann’s thought to produce cells that circulate thought in the W-V systems (?immune function?) Madreporite Madreporite sieve-like opens outside of body just off center of aboral size of size Digestive System Mouth to short espohagus Digestive System Mouth, short esophagus Two-part Stomach
Cardiac Stomach - oral side Pyloric Stomach Intestine, anus (only in some) Intestinal caeca mucus bound feces Stomach large Cardiac Stomach - oral side
Pyloric Stomach - with digestive diverticulae into each ray - Pyloric Caeca Short intest. Short intest to anus to 5 Evert cardiac stomach - digest, ciliary mucus cardiac digest, Carnivores Scavengers Herbivores very rare Ciliary mucus feeding Whole ingestion or evert cardiac stomach Internal or external digestion, or some of both Tube feet can be important prying open or immobilizing prey Main body cavity Main Perivisceral Coelom extends into each arm, houses pyloric caecae, extends caecae gonads, etc. gonads, Body Epidermis covers entire outside
Papillae cover surface important for diffusion Hemal System Hemal System channels of connective tissue function not clear Nervous System Circumoral nerve ring Radial Nerves Sensory and motor function Eye spot (modified tube foot) at end of each ray No brain Nerve ring - around mouth Nerve Radial nerves down each arm Eyespot - on modified tube foot Eyespot at tip of each arm photosensitive Generally sensitive to light/dark Chemical cues sensory receptors on dermis 6 Radial Cleavage
Reproduction: Dioeceous Ext. Fertilization gonopores at top of each Ray larva develops coelomic larva pouches pouches Bipinnaria Brachiolaria Brachiolaria Complex metamorphosis Complex Adult rudiment develops on side of larva Develops new mouth, anus, all internal spaces and organs Much of larval body resorbed, rest jettisoned Recently discovered - wide spread cloning of Recently wide echinoderm larvae - found in stars, urchins, sand dollars sand thus far thus Likely in all groups cloning rate increases with eau d’ predator 7 Grow with food de-grow without food Excellent powers of regeneration
Can reproduce by dropping arms Class Ophiuroidea
Brittle Stars, Basket Stars ~2000 spp Few large ossicles - articulate 5 equal rays brittle stars - simple basket stars - branched Few large ossicles – articulate Arms distinct from central disk No ambulacral groove ~ 5 equal rays (some 1 larger) - brittle stars – simple, all similar - basket stars – branched all ossicles covered all with epidermis with - internal skeleton Lack Pedicellariae & Papulae Because covered with ossicles ! tube feet, gut, bursae used for respiration Bursae - ciliated pockets (2 / arm) - open – oral side - pump water - contain gonopores ! brood chambers 8 Respiration - tube feet , gut, bursae Bursae ciliated pockets pump water can be used as brood chamber Locomotion - move arms 2 rays move in rowing fashion some bury in sand need to keep arms up in need water for respiration water Digestive System: blind gut, no anus, lining ciliated - mouth - 5 jaws, teeth - modified tube feet Feeding: collect particles w/ tube feet mucus ! mouth browse w/ jaws arm loop capture mucus string webs Water-vascular system Madreporite: absent or present ! oral shield less prominent in brittle stars, more in baskets some species may end blindly Rest similar to sea stars Except Tube feet do not have suckers or ampullae 9 Perivisceral coelom reduced Nervous System: similar to sea-stars - light sensitive skin Reproduction: separate sexes gonads in disk – 10 ! open into bursae Indirect dev ! free swimming - Larva Ophiopluteus Direct dev ! brood in bursae Larvae have internal Larvae skeletal ossicles ossicles 10 10 ...
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This note was uploaded on 01/27/2010 for the course BIO 37282 taught by Professor Padilla during the Fall '10 term at SUNY Stony Brook.
- Fall '10