biology lecture Phylum echinodermata

Phylum Echinodermata Introductions • Echinoderms are marine forms and include sea stars (also called starfishes), brittle stars, sea urchins, sea cucumbers, and sea lilies • Echinoderms are an ancient group of animals extending back to the Cambrian period • They occur in all oceans of the world and at all depths, from intertidal to abyssal regions • The approximately 6000 living species and 13 000 extinct species of Echinoderms Characteristics of Phylum Echinodermata Body unsegmented (nonmetameric) with radial symmetry → called pentamerous symmetry, because the body can be divided into five similar parts arranged around a centre axis - body rounded, cylindrical, or star shaped, with five or more radiating areas, or ambulacra, alternating with interambulacral areas Characteristics of Phylum Echinodermata A unique water-vascular system of coelomic origin that extends from the body surface as a series of tentacle-like projections Water-vascular system Podia penetrate between ossicles Characteristics of Phylum Echinodermata • A dermal endoskeleton composed of calcareous ossicles, with spines or of calcareous spicules in dermis - Commonly, the name Echinodermata, meaning “spiny skin” Characteristics of Phylum Echinodermata Locomotion by tube feet, by movement of spines, or by movement of arms Digestive system usually complete; axial or coiled; anus absent in ophiuroids Coelom extensive, forming the peri visceral cavity and the cavity of the water-vascular system; coelom of enterocoelous type; coelomic fluid with amebocytes Characteristics of Phylum Echinodermata Blood-vascular system (hemal system) much reduced, playing little if any role in circulation Respiration by dermal branchiae, tube feet, respiratory tree (holothuroids), and bursae (ophiuroids) Excretory organs absent 10 Sexes separate 11 Development through freeswimming, bilateral, larval stages Classification of Phylum Echinodermata Five Classes Asteroidea (Sao biển) Ophuiroidea (Đuôi rắn) Echinoidea (Cầu gai) Holothuroidea (Hải sâm) Crinoidea (Huệ biển) Class Asteroidea (Sao biển) • Sea stars, often called starfishes • Sea stars are composed of a central disc that merges gradually with the tapering arms (rays) • The body is somewhat flattened, flexible, and covered with a ciliated, pigmented epidermis • Typically, sea stars have aims, but some others (sun stars) have to 40 or more Class Asteroidea (Sao biển) External anatomy of asteroid A, Aboral view B, Oral view 1 Class Asteroidea (Sao biển) Pacific sea star Echinaster luzonicus Crossaster papposus, rose star, feeds on other sea stars 1 Class Asteroidea (Sao biển) Crown-of-thorns star Acanthaster planci , its spines are painful; the spines are equipped with poison glands This sea star has 20 to 24 arms and can range up to m in diameter (arm tip to arm tip) 2 Class Ophuiroidea (Đuôi rắn) • Apart from the typical possession of five arms, • The arms of brittle stars are slender and sharply set off from the central disc Oral view of spiny brittle star Ophiothrix 2 Class Ophuiroidea (Đuôi rắn) Brittle star Ophiura lutkeni (class Ophiuroidea) Basket star Astrophyton muricatum (class Ophiuroidea) Basket stars extend their manybranched arms to filter feed, usually at night 3 Class Echinoidea (Cầu gai) • The echinoid test is a compact skeleton of 10 double rows of plates that bear movable, stiff spines Internal structure of a sea urchin; water-vascular system in tan Class Echinoidea (Cầu gai) Diversity among regular sea urchins (class Echinoidea) 4 Class Holothuroidea (Hải sâm) • These animals have a remarkable resemblance to the vegetable after which they are named • The body wall is usually leathery, with tiny ossicles embedded in it • a few species have large ossicles forming a dermal armor Class Holothuroidea (Hải sâm) Sea cucumbers (class Holothuroidea) 4 Class Holothuroidea (Hải sâm) Anatomy of the sea cucumber Sclerodactyla A, Internal B, External Red, hemal system Class Crinoidea (Huệ biển) • Crinoids include sea lilies and feather stars • Sea lilies have a flower-shaped body that is placed at the tip of an attached stalk Class Crinoidea (Huệ biển) • Feather stars have long, many-branched arms • adults are free moving, though they may remain in the same spot for long periods ... ossicles Characteristics of Phylum Echinodermata • A dermal endoskeleton composed of calcareous ossicles, with spines or of calcareous spicules in dermis - Commonly, the name Echinodermata, meaning... more radiating areas, or ambulacra, alternating with interambulacral areas Characteristics of Phylum Echinodermata A unique water-vascular system of coelomic origin that extends from the body surface... approximately 6000 living species and 13 000 extinct species of Echinoderms Characteristics of Phylum Echinodermata Body unsegmented (nonmetameric) with radial symmetry → called pentamerous symmetry,