04 June 2015Echinodermata.ppt1 Deuterostome Phyla

04 June 2015Echinodermata.ppt2 Deuterostome Phyla Kingdom Animalia [subkingdom] Deuterostomes Phylum Echinodermata Phylum Chordata Phylum Hemichordata [subkingdom] Protostomes

04 June 2015Echinodermata.ppt3 Deuterostomes Two major phyla share three embryonic characters Radial, indeterminate cleavage Anus develops at site of blastopore (2 nd mouth) Mesoderm develops from lateral pouches of endoderm “gut-pouch” coelom

04 June 2015Echinodermata.ppt4 Deuterostomes Mesoderm develops from lateral pouches of endoderm Pouches of endoderm bulge, pinch off to form Mesoderm “gut pouch” coelom. Cavity enclosed in mesoderm = coelom Coelom: body cavity completely enclosed by mesoderm & not opening to outside.

Development of Gut and Mesoderm 04 June Echinodermata.ppt Deuterostomes Radial cleavage; Anus develops at site of blastopore “second mouth” Pouches of mesoderm arise from endoderm; close to form coelom.

04 June 2015Echinodermata.ppt6 Phylum Echinodermata Phylum Echinodermata (Gr. “spiny skin”) Actually, skeleton is spiny. Body plan Tube-in-tube, Deuterostomous Bilateral symmetry as larvae Coelomate, “gut pouch” coelom

04 June 2015Echinodermata.ppt7 Phylum Echinodermata Marine only, largest phylum with no aquatic or terrestrial members. Organs & Organ systems Digestive, nervous, reproductive, etc. Distinguishing characters  Pentaradial symmetry (NOT “radial”)  Endoskeleton of ossicles  Water vascular system

04 June 2015Echinodermata.ppt8 Phylum Echinodermata Pentaradial symmetry (NOT “radial”) 5-sided or 5-part symmetry around an axis Adaptation to sessile or slow-moving life Arrays sense organs & defenses all around body Larvae are bilaterally symmetrical

04 June 2015Echinodermata.ppt9 Phylum Echinodermata Why pentaradial? Lots of hypotheses, few with much support. Extinct, fossil echinoderms known with 3-, 4-, and 6-radial symmetries.

04 June 2015Echinodermata.ppt10 Phylum Echinodermata Endoskeleton of ossicles CaCO 3, calcium carbonate Echinoderms have left abundant fossils.

04 June 2015Echinodermata.ppt11 Phylum Echinodermata Water vascular system For circulation, respiration, locomotion feeding

04 June 2015Echinodermata.ppt12 Phylum Echinodermata How tube feet work Transfer water between ampulla & podium Muscles bend, attach, pull “Suction cup” at end Nervous system coordinates hundreds of tube feet.

Phylum Echinodermata Ways needs of cells are met: Food: Herbivores, detritus/deposit feeders, predators Circulation through coelomic fluid O 2 and CO 2 exchange Diffusion through epidermal “gills” and tube feet Respiratory tree (Sea cucumbers) Waste removal by diffusion and coelomocytes that accumulate waste and carry it to body surface. 04 June 2015Echinodermata.ppt13

Phylum Echinodermata Concerns of multicellular animal: Circulation in coelomic fluid Ciliated peritoneum. Coordination by circumoral ring and radial nerves 04 June 2015Echinodermata.ppt14

Phylum Echinodermata Concerns of multicellular animal: Support and movement Endoskeleton Tube feet Water balance Usually isotonic with seawater, little ability to osmoregulate All marine, few live in brackish water. 04 June 2015Echinodermata.ppt15

Phylum Echinodermata Reproduction Asexual by regeneration Asterias vulgaris: 1/5 central disc with arm can regenerate whole sea star Natural division of central disc Sexual, external fertilization Sexes usually separate Few hermaphrodites 04 June 2015Echinodermata.ppt16

04 June 2015Echinodermata.ppt17 Phylum Echinodermata Class Crinoidea Crinoids, basket stars, sea lilies Class Asteroidea Sea stars Class Ophiuroidea Brittle stars, snake stars Class Echinoidea Sea urchins, heart urchins, sand dollars Class Holothuroidea Sea cucumbers

04 June 2015Echinodermata.ppt18 Class Crinoidea Most similar to ancestral echinoderms Small body with many branched “arms” Mouth (oral side) & tube feet up Feed on organic detritus falling on “arms,” push food to mouth.

04 June 2015Echinodermata.ppt19 Class Asteroidea Five body extensions (not “arms”); Digestive glands, gonads in extensions; Eversible stomach Predators on clams, barnacles, etc. Oral side down, walk on tube feet.

04 June 2015Echinodermata.ppt20 Class Ophiuroidea Body disc Thin, flexible “arms” Deposit feeders, scavengers, filter feeders

04 June 2015Echinodermata.ppt21 Class Echinoidea Spherical body (flattened in sand dollars) Prominent spines Herbivores, Scavengers deposit feeders (sand dollars)

04 June 2015Echinodermata.ppt22 Class Holothuroidea Ossicles small, reduced Soft-bodied Worm-like with 5 rows of tube feet Some rows vestigial Oral tentacles Feed on organic detritus