Deutrostomia

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DeutrostomiaDeutrostomia

Deutrostome means mouth second and encompasses a number of Deutrostome means mouth second and encompasses a number of animal groups including our own. animal groups including our own.

The phylogenetic relationships between all of these animals are The phylogenetic relationships between all of these animals are continually changing as more is discovered about them and so continually changing as more is discovered about them and so here is an account of the phylogeny taken from one source (the here is an account of the phylogeny taken from one source (the tree of life) even though it is disputed in other placestree of life) even though it is disputed in other places

DeutrostomiaDeutrostomia

Sea urchins, Sand dollars and Sea stars.Sea urchins, Sand dollars and Sea stars. 6000 living species in 5 classes6000 living species in 5 classes All examples are marine and there are no All examples are marine and there are no

parasitic forms.parasitic forms.

PHYLUM: ECHINODERMATAPHYLUM: ECHINODERMATA

General General characteristicscharacteristics

Spiny-skinned animals Spiny-skinned animals possessing calcareous possessing calcareous ossicles embedded in ossicles embedded in the dermis and spines the dermis and spines protruding from the protruding from the surface: this creates surface: this creates an internal skeletonan internal skeleton..


General characteristicsGeneral characteristics

They are radially symmetrical in the adult phase and are They are radially symmetrical in the adult phase and are characterized by having five rays, or multiples of five characterized by having five rays, or multiples of five (pentamerous). This penta-symmetry is most apparent in star fish (pentamerous). This penta-symmetry is most apparent in star fish and least apparent in sea cucumbers. Echinoderms have not and least apparent in sea cucumbers. Echinoderms have not always been radially symmetrical: fossil forms are bilaterally always been radially symmetrical: fossil forms are bilaterally symmetrical (with a left and right side and a front and back). symmetrical (with a left and right side and a front and back). Echinoderm Larval stages (bipinnaria) are also bilaterally Echinoderm Larval stages (bipinnaria) are also bilaterally symmetrical. symmetrical.

PHYLUM: PHYLUM: ECHINODERMATAECHINODERMATA


Body walls are composed of three layers of cells. Most tissues are Body walls are composed of three layers of cells. Most tissues are ciliated. There is no head region, brain nor segmentation ciliated. There is no head region, brain nor segmentation



All have tube feet which extend by hydraulic pressure from the All have tube feet which extend by hydraulic pressure from the animal's water vascular system, which are used variously for animal's water vascular system, which are used variously for locomotion, burrowing, exchange of gases (respiration) and locomotion, burrowing, exchange of gases (respiration) and feeding feeding



The digestive tract is The digestive tract is simple usually simple usually complete (but may complete (but may lack an anus and lack an anus and therefore be therefore be incomplete).incomplete).



Respiration is achieved by minute gills (dermal papulae) which Respiration is achieved by minute gills (dermal papulae) which protrude from the coelom, by tube feet and in the case of sea protrude from the coelom, by tube feet and in the case of sea cucumbers by a cloaca1 respiratory trees. A circulatory system cucumbers by a cloaca1 respiratory trees. A circulatory system radiates from the central coelom, the coelom is lined with ciliated radiates from the central coelom, the coelom is lined with ciliated peritoneum and is usually large and its fluid contains free peritoneum and is usually large and its fluid contains free amoebocytes. Part of the larval coelom becomes a water vascular amoebocytes. Part of the larval coelom becomes a water vascular system usually having many tube feet, serving for locomotion, food system usually having many tube feet, serving for locomotion, food handling, or respiration. handling, or respiration.



The nervous system The nervous system consists of a circum consists of a circum oral ring and radial oral ring and radial nerves into each nerves into each arm.arm.



The sexes are separate (rare exceptions), and alike externally; The sexes are separate (rare exceptions), and alike externally; gonads are large with simple ducts; ova are abundant. The larva is gonads are large with simple ducts; ova are abundant. The larva is free-swimming, and is characterized by a conspicuous free-swimming, and is characterized by a conspicuous metamorphosis to become adults. A few species are viviparous, a metamorphosis to become adults. A few species are viviparous, a few reproduce asexually by self-division, and many regenerate lost few reproduce asexually by self-division, and many regenerate lost parts readily. For example star fish are generally capable of parts readily. For example star fish are generally capable of replacing one or more lost arms; sometimes, even a single arm replacing one or more lost arms; sometimes, even a single arm can regenerate into an entire animal.can regenerate into an entire animal.


Classes of living Classes of living echinodermsechinoderms

Asteroidea (sea stars and Asteroidea (sea stars and star fish)star fish)

Crinoidea (sea lilies and Crinoidea (sea lilies and feather stars)feather stars)

Holothuroidea (sea Holothuroidea (sea cucumbers)cucumbers)

Echinoidea (sea urchins Echinoidea (sea urchins and sand dollars)and sand dollars)

Ophiuroidea (brittle stars)Ophiuroidea (brittle stars)


Classes of living Classes of living echinoderms:echinoderms: Asteroidea (sea Asteroidea (sea stars and star fish)stars and star fish)

General structure of a star fish: General structure of a star fish: ExternalExternal

The Lower surface with the The Lower surface with the mouth is called the oral surface. mouth is called the oral surface. The upper surface with the anus The upper surface with the anus is called the aboral surface. Both is called the aboral surface. Both the mouth and anus are centrally the mouth and anus are centrally situated.situated.


Classes of living echinoderms: Classes of living echinoderms: Asteroidea (sea stars and star Asteroidea (sea stars and star fish)fish)

General structure of a star fish: General structure of a star fish: Oral SurfaceOral Surface

Has five ambulacral grooves, one Has five ambulacral grooves, one in each ray from which extends two in each ray from which extends two or four rows of tube-feet. The ray or four rows of tube-feet. The ray may be flexed slowly by a few may be flexed slowly by a few retractor muscles in the body wall.retractor muscles in the body wall.

Aboral Surface - Many spines of Aboral Surface - Many spines of various sizes, pedicellariae and various sizes, pedicellariae and dermal papulae at the base of the dermal papulae at the base of the spines, a madreporite which is the spines, a madreporite which is the entrance to the water vascular entrance to the water vascular system and an anal opening.system and an anal opening.


Classes of living echinoderms:Classes of living echinoderms: Asteroidea (sea stars and star fish)Asteroidea (sea stars and star fish)

General structure of a star fish: Internal SystemGeneral structure of a star fish: Internal System An endoskeleton of calcareous plates or ossicles is bound together by An endoskeleton of calcareous plates or ossicles is bound together by

muscles and connective tissue with an epidermis. muscles and connective tissue with an epidermis. Around their base are many modified spines, the pedicellaria, which Around their base are many modified spines, the pedicellaria, which

resemble tiny jaws or scissor blades mounted on a stalk. resemble tiny jaws or scissor blades mounted on a stalk. When stimulated mechanically or chemically, the pedicellaria may be When stimulated mechanically or chemically, the pedicellaria may be

opened by muscles. opened by muscles. Their function is to keep the aboral surface clean, to aid in the capture Their function is to keep the aboral surface clean, to aid in the capture

of small food particles and protect the dermal papulae which are thin of small food particles and protect the dermal papulae which are thin walled extensions of the coelom and facilitate gaseous exchange.walled extensions of the coelom and facilitate gaseous exchange.


Classes of living echinoderms: Classes of living echinoderms: Asteroidea (sea stars and star fish)Asteroidea (sea stars and star fish)

General structure of a star fish: General structure of a star fish: Water Vascular System Water Vascular System

The water vascular system is a division of the The water vascular system is a division of the coelom coelom

a system of hollow interconnected tubes filled a system of hollow interconnected tubes filled with water. with water.

Water enters the system via the madreporite Water enters the system via the madreporite on the aboral disc. The water vascular system terminates in a tube-feet on the aboral disc. The water vascular system terminates in a tube-feet (Podia) in the grooves on the oral surface. (Podia) in the grooves on the oral surface.

The sequence of canals in the water vascular system is as follows:The sequence of canals in the water vascular system is as follows:Madreporite (sieves the water)Madreporite (sieves the water)Stone Canal (runs downwards)Stone Canal (runs downwards)Ring Canal (encircles the mouth)Ring Canal (encircles the mouth)5 Radial Canals (one per ray arm)5 Radial Canals (one per ray arm)Numerous Transverse Canals (perpendicular to radial canal)Numerous Transverse Canals (perpendicular to radial canal)Ampullae: The head of the tube feet.Ampullae: The head of the tube feet.


Classes of living echinoderms: Classes of living echinoderms: Asteroidea (sea stars and Asteroidea (sea stars and star fish)star fish)

General structure of a star fish: Water Vascular SystemGeneral structure of a star fish: Water Vascular System The water vascular system is a hydraulic pressure The water vascular system is a hydraulic pressure

system. system. The star fish moves by means of its tube feet. The star fish moves by means of its tube feet. A tube feet elongates as the muscles surrounding the A tube feet elongates as the muscles surrounding the

ampullae contract forcing fluid in to the foot. ampullae contract forcing fluid in to the foot. On the bottom of the foot is a sucker which adheres to On the bottom of the foot is a sucker which adheres to

the substratumthe substratum Longitudinal muscles then contract, shortening the ray Longitudinal muscles then contract, shortening the ray

arm and help pull the star fish forward. arm and help pull the star fish forward. Tube feet are also used for capturing and handling food, Tube feet are also used for capturing and handling food,

and for respiration and excretion. and for respiration and excretion.


Classes of living echinoderms: Classes of living echinoderms: AAsteroidea (sea stars and star fish)steroidea (sea stars and star fish)

General Structure of a Starfish: Digestive SystemGeneral Structure of a Starfish: Digestive System This is a short but complete systemThis is a short but complete system MouthMouth Short oesophagusShort oesophagus Thin wall stomach - large Cardiac stomachThin wall stomach - large Cardiac stomach - small aboral Pyloric stomach- small aboral Pyloric stomach From the Pyloric a tube passes into each ray arm.From the Pyloric a tube passes into each ray arm. In each ray arm it divides into two branches called hepatic cecae In each ray arm it divides into two branches called hepatic cecae

from here many lateral pouches exist.from here many lateral pouches exist. Above the stomach is a slender intestine splits in to two branched Above the stomach is a slender intestine splits in to two branched

pouches, the rectal and intestinal cecae pouches, the rectal and intestinal cecae AnusAnus


Classes of living echinoderms:Classes of living echinoderms:Asteroidea (sea stars and star fish)Asteroidea (sea stars and star fish)

FoodFood Starfish eat almost any animal matter, and are also Starfish eat almost any animal matter, and are also

carnivorous on oysters, mussels, barnacles, clams carnivorous on oysters, mussels, barnacles, clams etc. etc.

Small food: passes directly to the mouth via the Small food: passes directly to the mouth via the pedicellaria or tube feet. pedicellaria or tube feet.

Bivalves: the starfish opens the shell halves slightly Bivalves: the starfish opens the shell halves slightly using its ray arms and tube feet. The cardiac using its ray arms and tube feet. The cardiac stomach is everted between the gap in the shell stomach is everted between the gap in the shell halves. Digestive enzymes are released and the prey halves. Digestive enzymes are released and the prey tissue is broken down into a fluid which is swept in to tissue is broken down into a fluid which is swept in to the hepatic cecae by the action of cilia. Nutrients are the hepatic cecae by the action of cilia. Nutrients are stored in the hepatic ceca.stored in the hepatic ceca.


Classes of living echinoderms: Classes of living echinoderms: Asteroidea (sea stars and star Asteroidea (sea stars and star fish)fish)

RespirationRespiration Gaseous exchange between dermal papulae and tube feet.Gaseous exchange between dermal papulae and tube feet. Dermal papulae are outpockets of the coelom that pass through minute Dermal papulae are outpockets of the coelom that pass through minute

openings in the skeleton. openings in the skeleton. They are covered with cilia on the They are covered with cilia on the

internal and external surfaces. internal and external surfaces. The external cilia keep a current The external cilia keep a current

of oxygenated water passing over of oxygenated water passing over the outside, and the internal cilia the outside, and the internal cilia circulate the coelomic fluid into the circulate the coelomic fluid into the papulae.papulae.


Classes of living echinoderms:Classes of living echinoderms:Asteroidea (sea stars and star fish)Asteroidea (sea stars and star fish)

ExcretionExcretion Ammonia is the principal soluble nitrogenous wasteAmmonia is the principal soluble nitrogenous waste it diffuses through thin areas of the body surface, especially tube feet it diffuses through thin areas of the body surface, especially tube feet

and dermal papulae. and dermal papulae. Particulate waste are picked up by the amoebocytes within the coelom; Particulate waste are picked up by the amoebocytes within the coelom;

these amoebocytes are subsequently eliminated through the walls of these amoebocytes are subsequently eliminated through the walls of the dermal papulaethe dermal papulae..


Classes of living echinoderms: Classes of living echinoderms: Asteroidea (sea Asteroidea (sea stars and star fish)stars and star fish)

Nervous System and Sense Organs Nervous System and Sense Organs This consists of a nerve ring around the mouth This consists of a nerve ring around the mouth

plus five large radial nerves that run parallel to plus five large radial nerves that run parallel to the radial canals of the water vascular systemthe radial canals of the water vascular system

Most echinoderms respond to touch, gravity, Most echinoderms respond to touch, gravity, light and chemical stimuli.light and chemical stimuli.

Sense organs are poorly developed. Sense organs are poorly developed. At the end of each ray is a small tactile tentacle At the end of each ray is a small tactile tentacle

and a light sensitive eyespot composed of 80 to and a light sensitive eyespot composed of 80 to 200 ocelli. 200 ocelli.

Most echinoderms are negatively phototaxic and Most echinoderms are negatively phototaxic and generally seek shade. generally seek shade.


Classes of living echinoderms: Classes of living echinoderms: Asteroidea (sea stars and star fish)Asteroidea (sea stars and star fish)

Reproduction and RegenerationReproduction and Regeneration Sexes are separate. Sexes are separate. A pair of branched gonads in the A pair of branched gonads in the

perivisceral coelom - base of each armperivisceral coelom - base of each arm Female starfish release up to 2.5 Female starfish release up to 2.5

million eggs at oncemillion eggs at once Males produce even more sperm. Males produce even more sperm. External Fertilization and developmentExternal Fertilization and development Echinoderm development: fertilized Echinoderm development: fertilized

cell cell cleavage cleavage two-egg stage two-egg stage blastula blastula gastrula gastrula bipinnaria bipinnaria branchiolaria branchiolaria undergoes undergoes metamorphosis metamorphosis pentasymnetrical pentasymnetrical starfish.starfish.


Classes of living echinoderms: Classes of living echinoderms: Holothuroidea (Sea Holothuroidea (Sea Cucumbers)Cucumbers)

They feed on detritus, which they They feed on detritus, which they take into the mouth by large take into the mouth by large modified tube feet surrounding it. modified tube feet surrounding it.

The remaining tube feet The remaining tube feet resemble those of the starfish resemble those of the starfish and are used for locomotion. and are used for locomotion. Although there are fiveAlthough there are five


Classes of living echinoderms: Classes of living echinoderms: Crinoidea (Sea Lilies)Crinoidea (Sea Lilies)

Occur as free living forms Occur as free living forms (feather star) or sessile forms (feather star) or sessile forms (sea Lilies)(sea Lilies)

These animals are highly These animals are highly calcified, and generally occur in calcified, and generally occur in deep waters.deep waters.

Collect food by ciliary currents Collect food by ciliary currents set up on their complex arms. set up on their complex arms.

Tube feet are present only as Tube feet are present only as small papillae on the sides of small papillae on the sides of the ambulacral grooves.the ambulacral grooves.


Classes of living echinoderms: Classes of living echinoderms: Ophiuroidea (Brittle Stars)Ophiuroidea (Brittle Stars)

Possess five arms radiating from a Possess five arms radiating from a central disccentral disc

Tube feet lack suckersTube feet lack suckers movement brought about by muscles movement brought about by muscles

which connect successive ambulacral which connect successive ambulacral ossicles ossicles

They are detritus feeders, having a They are detritus feeders, having a capacious stomach but lack any capacious stomach but lack any extension of the gut into the arms and extension of the gut into the arms and lack an anuslack an anus

Collect food by ciliary currents set up on Collect food by ciliary currents set up on their complex arms their complex arms

Tube feet are present only as small Tube feet are present only as small papillae on the sides of the ambulacral papillae on the sides of the ambulacral grooves.grooves.


Classes of living echinoderms: Classes of living echinoderms: Echinoidea (Sea Urchins)Echinoidea (Sea Urchins)

Have a rigid body wall or test composed of closely fitting calcareous Have a rigid body wall or test composed of closely fitting calcareous plates embedded in the dermis. plates embedded in the dermis.

Oral surface large compared to the aboral surface. Oral surface large compared to the aboral surface. The mouth is surrounded by powerful jaws which can scrape off The mouth is surrounded by powerful jaws which can scrape off

encrusting organisms from the rocks. encrusting organisms from the rocks. The spines borne on the test are long and movable and are The spines borne on the test are long and movable and are

interspersed with pedicellaria. interspersed with pedicellaria. The numerous tube feet are very extensible and project beyond the The numerous tube feet are very extensible and project beyond the

spines`spines`


Deutrostomia

Documents

segmentation phylum

case of sea cucumbers

star fish crinoidea

example star fish

star fish general structure

tube feet

larval coelom

animals water vascular