zoology ch 22 Echinoderms

Characteristics of Phylum Echinodermata

Possess a calcareous spiny exoskeleton of plates and ossicles, a water vascular system for movement and foraging, pedicellariae(in some, miniature jaw like pinchers on body surface) dermal brachiae(skin gills), and basic penta-radial symmetry

Secondarily radial, Free swimming bilateral larvae, deuterostones, include sea stars, brittle stars, see cucumbers, etc

Ecology of Phylum Echinodermata

All marine, distributed throughout the world’s oceans, mainly predators on sessile invertebrate pray, also particle, filter, algae, suspension, and detritus feeders

Characteristics of Class Asteroiea

Sea Stars

Five tapered arms that merge at central disc, an oral surface and aboral surface

Oral surface of Class Asteroiea

A mouth and ambulacral groove that runs from mouth to tip of each arm. Tube feet on order, radial nerve runs down center, spines on either side

Aboral surface of Class Asteroiea

Has an anus, pedicellarie(my new pincher like jaws at base of spines, Clean body surface, protect skin, Aids in food capture), dermal branchiae (papulae, project out of coelomic cavity respiration), and Madroporite(opening to water vascular system)

Water-vascular system of Class Asteroiea

Set of canals and specialized tube feet for locomotion and food gathering. Consist of madreporite(Connected to ring, canals, and radial canals), Lateral canals(Have one way valves to prevent backflow), and tube feet(hollow muscular tubes with sucker at tip, with an ampulla(fluid reservoir))

Feeding and digestion of Class Asteroiea

Two parts stomach in central disc: A cardiac stomach can be everted through mouth and pyloric stomach attached to pyloric ceca(digestive glands) in each arm. External digestion, intestines attaches stomach to anus, feeds heavily on mollusks

Reproduction in Class Asteroiea

Most are dioecious, Use external fertilization, Direct development or free swimming, bilateral larva, undergo metamorphosis

Regeneration in Class Asteroiea

This class can regenerate loss parts as long as the break includes at least 1/5 of the central disc. That broken piece can develop into a brand new star. Stars can also cast off damaged arms and regrow them

Characteristics of Class Ophiuroidea

Brittle Stars:

Slender arms; lack pedicellariae and papulae; Closed ambulacral grooves; Tube feed lacks suckers; madreporite on Oral surface; Locomotion by arm Movement; All organs are in central disc; no anus or intestines, waste cast out of mouth; 5 pairs of bursae open toward oral surface to circulate water in and out for gas exchange

Characteristics of Class Echinoidea

Sea urchins and Sand dollars:

Have a test(Exoskeleton of closely fitting plates made from dermal ossicles); pentaramous plan, no arms, 5 ambulacral rows, tube feet extend through pores along rows); oral surface expands around aboral side to periproct; pedicellariae, have three jaws on the stock and some have venom glands for subduing praying

Regular Sea Urchins

Hemispherical shape; radial symmetry; Medium to large spines; Move with tube feet; Found on hard substrates; Five converging team; anus, genital pore, and madreporite occur aborally

Irregular sea urchins

Sand dollars and heart urchins; Secondarily bilateral; short spines; move with cilia; found in substrates

Test of class Echinoidea

Inside the test there is a coiled digestive track, and Aristotle’s lantern which (chews food); they mostly Feed on algae and detritus

Petaloids

Respiratory podia arranged in fields on aboral service of irregular urchins

Class Holothuroidea

A long day on their oral aboral axis(side); ossicles are tiny and embedded in leather body wall; used 2 feet for locomotion; large fluid filled coelomic cavity that serves as hydrostatic skeleton; respiratory tree for respiration and excretion(only occurs in the group); free floating madreporite in the coleom

Feeding of Class Holothuroidea

Sedentary species will feed on suspended food particles by trapping them in the mucus on oral tentacles and stuffing it into their mouth

Deposit feeders, collect food with tentacles

Defense of Class Holothuroidea

Discharge their cuvierian tubules from posterior part of respiratory tree to entangle would be predators. Some contain toxins and some discharge part of their viscera