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Deutrostomia

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

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Deutrostomia

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  1. Deutrostomia

  2. Deutrostomia • Deutrostome means mouth second and encompasses a number of animal groups including our own. • The phylogenetic relationships between all of these animals are continually changing as more is discovered about them and so here is an account of the phylogeny taken from one source (the tree of life) even though it is disputed in other places

  3. PHYLUM: ECHINODERMATA • Sea urchins, Sand dollars and Sea stars. • 6000 living species in 5 classes • All examples are marine and there are no parasitic forms.

  4. PHYLUM: ECHINODERMATA • General characteristics • Spiny-skinned animals possessing calcareous ossicles embedded in the dermis and spines protruding from the surface: this creates an internal skeleton.

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

  6. PHYLUM: ECHINODERMATA • General characteristics • Body walls are composed of three layers of cells. Most tissues are ciliated. There is no head region, brain nor segmentation

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

  8. PHYLUM: ECHINODERMATA • General characteristics • The digestive tract is simple usually complete (but may lack an anus and therefore be incomplete).

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

  10. PHYLUM: ECHINODERMATA • General characteristics • The nervous system consists of a circum oral ring and radial nerves into each arm.

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

  12. PHYLUM: ECHINODERMATA • Classes of living echinoderms • Asteroidea (sea stars and star fish) • Crinoidea (sea lilies and feather stars) • Holothuroidea (sea cucumbers) • Echinoidea (sea urchins and sand dollars) • Ophiuroidea (brittle stars)

  13. PHYLUM: ECHINODERMATA • Classes of living echinoderms:Asteroidea (sea stars and star fish) General structure of a star fish: External • The Lower surface with the mouth is called the oral surface. The upper surface with the anus is called the aboral surface. Both the mouth and anus are centrally situated.

  14. PHYLUM: ECHINODERMATA Classes of living echinoderms: Asteroidea (sea stars and star fish) General structure of a star fish: Oral Surface • Has five ambulacral grooves, one in each ray from which extends two or four rows of tube-feet. The ray may be flexed slowly by a few retractor muscles in the body wall. • Aboral Surface - Many spines of various sizes, pedicellariae and dermal papulae at the base of the spines, a madreporite which is the entrance to the water vascular system and an anal opening.

  15. PHYLUM: ECHINODERMATA Classes of living echinoderms: Asteroidea (sea stars and star fish) General structure of a star fish: Internal System • An endoskeleton of calcareous plates or ossicles is bound together by muscles and connective tissue with an epidermis. • Around their base are many modified spines, the pedicellaria, which resemble tiny jaws or scissor blades mounted on a stalk. • When stimulated mechanically or chemically, the pedicellaria may be opened by muscles. • 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 walled extensions of the coelom and facilitate gaseous exchange.

  16. PHYLUM: ECHINODERMATA Classes of living echinoderms: Asteroidea (sea stars and star fish) • General structure of a star fish: Water Vascular System • The water vascular system is a division of the coelom • a system of hollow interconnected tubes filled with water. • Water enters the system via the madreporite on the aboral disc. The water vascular system terminates in a tube-feet (Podia) in the grooves on the oral surface. • The sequence of canals in the water vascular system is as follows: • Madreporite (sieves the water) • Stone Canal (runs downwards) • Ring Canal (encircles the mouth) • 5 Radial Canals (one per ray arm) • Numerous Transverse Canals (perpendicular to radial canal) • Ampullae: The head of the tube feet.

  17. PHYLUM: ECHINODERMATA Classes of living echinoderms: Asteroidea (sea stars and star fish) General structure of a star fish: Water Vascular System • The water vascular system is a hydraulic pressure system. • The star fish moves by means of its tube feet. • A tube feet elongates as the muscles surrounding the ampullae contract forcing fluid in to the foot. • On the bottom of the foot is a sucker which adheres to the substratum • Longitudinal muscles then contract, shortening the ray arm and help pull the star fish forward. • Tube feet are also used for capturing and handling food, and for respiration and excretion.

  18. PHYLUM: ECHINODERMATA Classes of living echinoderms: Asteroidea (sea stars and star fish) • General Structure of a Starfish: Digestive System • This is a short but complete system • Mouth • Short oesophagus • Thin wall stomach - large Cardiac stomach • - small aboral Pyloric stomach • From the Pyloric a tube passes into each ray arm. • In each ray arm it divides into two branches called hepatic cecae from here many lateral pouches exist. • Above the stomach is a slender intestine splits in to two branched pouches, the rectal and intestinal cecae • Anus

  19. PHYLUM: ECHINODERMATA Classes of living echinoderms: Asteroidea (sea stars and star fish) • Food • Starfish eat almost any animal matter, and are also carnivorous on oysters, mussels, barnacles, clams etc. • Small food: passes directly to the mouth via the pedicellaria or tube feet. • Bivalves: the starfish opens the shell halves slightly using its ray arms and tube feet. The cardiac stomach is everted between the gap in the shell halves. Digestive enzymes are released and the prey tissue is broken down into a fluid which is swept in to the hepatic cecae by the action of cilia. Nutrients are stored in the hepatic ceca.

  20. PHYLUM: ECHINODERMATA • Classes of living echinoderms: Asteroidea (sea stars and star fish) • Respiration • Gaseous exchange between dermal papulae and tube feet. • Dermal papulae are outpockets of the coelom that pass through minute openings in the skeleton. • They are covered with cilia on the internal and external surfaces. • The external cilia keep a current of oxygenated water passing over the outside, and the internal cilia circulate the coelomic fluid into the papulae.

  21. PHYLUM: ECHINODERMATA Classes of living echinoderms:Asteroidea (sea stars and star fish) • Excretion • Ammonia is the principal soluble nitrogenous waste • it diffuses through thin areas of the body surface, especially tube feet and dermal papulae. • Particulate waste are picked up by the amoebocytes within the coelom; these amoebocytes are subsequently eliminated through the walls of the dermal papulae.

  22. PHYLUM: ECHINODERMATA Classes of living echinoderms: Asteroidea (sea stars and star fish) • Nervous System and Sense Organs • This consists of a nerve ring around the mouth plus five large radial nerves that run parallel to the radial canals of the water vascular system • Most echinoderms respond to touch, gravity, light and chemical stimuli. • Sense organs are poorly developed. • At the end of each ray is a small tactile tentacle and a light sensitive eyespot composed of 80 to 200 ocelli. • Most echinoderms are negatively phototaxic and generally seek shade.

  23. PHYLUM: ECHINODERMATA Classes of living echinoderms: Asteroidea (sea stars and star fish) • Reproduction and Regeneration • Sexes are separate. • A pair of branched gonads in the perivisceral coelom - base of each arm • Female starfish release up to 2.5 million eggs at once • Males produce even more sperm. • External Fertilization and development • Echinoderm development: fertilized cell  cleavage two-egg stage  blastula  gastrula  bipinnaria branchiolaria  undergoes metamorphosis pentasymnetrical starfish.

  24. PHYLUM: ECHINODERMATA Classes of living echinoderms: Holothuroidea (Sea Cucumbers) • They feed on detritus, which they take into the mouth by large modified tube feet surrounding it. • The remaining tube feet resemble those of the starfish and are used for locomotion. Although there are five

  25. PHYLUM: ECHINODERMATA Classes of living echinoderms: Crinoidea (Sea Lilies) • Occur as free living forms (feather star) or sessile forms (sea Lilies) • These animals are highly calcified, and generally occur in deep waters. • Collect food by ciliary currents set up on their complex arms. • Tube feet are present only as small papillae on the sides of the ambulacral grooves.

  26. PHYLUM: ECHINODERMATA Classes of living echinoderms: Ophiuroidea (Brittle Stars) • Possess five arms radiating from a central disc • Tube feet lack suckers • movement brought about by muscles which connect successive ambulacral ossicles • They are detritus feeders, having a capacious stomach but lack any extension of the gut into the arms and lack an anus • Collect food by ciliary currents set up on their complex arms • Tube feet are present only as small papillae on the sides of the ambulacral grooves.

  27. PHYLUM: ECHINODERMATA Classes of living echinoderms: Echinoidea (Sea Urchins) • Have a rigid body wall or test composed of closely fitting calcareous plates embedded in the dermis. • Oral surface large compared to the aboral surface. • The mouth is surrounded by powerful jaws which can scrape off encrusting organisms from the rocks. • The spines borne on the test are long and movable and are interspersed with pedicellaria. • The numerous tube feet are very extensible and project beyond the spines`

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