3-Protocordados

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Characteristics and Adaptations

Plan Estructural Nombre Cordados viene de notocorda

En forma de barra, tejido semirigido encerrrado en una funda En la mayora de los casos, se extiende a lo largo del tubo

digestivo y el sistema nervioso Sirve principalmente para armar o tensar el cuerpo (rigidez) y

provee el andamiaje esqueletico para el acoplamiento de los msculos para la natacin.

5 caracteristicas de los cordados Medula nerviosa dorsal tubular Notocorda Hendiduras Faringeas Endostilo Cola Postanal

Five Chordate Hallmarks

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Notochord Always found at some embryonic stage First part of the endoskeleton to appear in the

embryo Serves as an axis for muscle attachment Can bend without shortening and permits undulation In protochordates and jawless vertebrates,

Persists throughout life

Funda Elstica

Funda Fibrosa

Notocorda


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In vertebrates Series of cartilaginous or bony vertebrae form from

mesenchymal cells derived from blocks of mesodermal cells lateral to notochord

In most vertebrates Notochord displaced by vertebrae Remnants may persist between or within vertebrae


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Dorsal Tubular Nerve Cord

In most invertebrate phyla

Nerve cord is solid and ventral to alimentary canal

In chordates

Single, tubular cord is dorsal to alimentary canal

Anterior end enlarges to form the brain

Cord is produced in embryo by infolding of ectodermal cells on the dorsal side of body


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Pharyngeal Pouches and Slits Pharyngeal slits lead from pharyngeal cavity to the

outside Form by the inpocketing of the ectoderm and the

evagination of endoderm of pharynx In aquatic chordates

2 pockets break through to form pharyngeal slit

In amniotes Pockets may not break through and only grooves are formed


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In tetrapods Pharyngeal pouches give rise to a variety of structures,

including the Eustachian tube, middle ear cavity, tonsils and parathyroid glands

Perforated pharynx functions as filter-feeding apparatus in protochordates

Fishes added a capillary network with thin gas-permeable walls Led to evolution of gills


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Endostyle or Thyroid Gland

Recently, the endostyle was recognized as a shared chordate character

Endostyle or its derivative, the thyroid gland, found in all chordates

Some cells in endostyle secrete iodinated proteins homologous with the iodinated-hormone-secreting thyroid gland of adult lampreys and the remainder of vertebrates


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Postanal Tail

Postanal tail, plus musculature, provided motility for larval tunicates and Amphioxus to swim.

Efficiency increased in fishes but became smaller or vestigial in later lineages

Subphylum Urochordata: Tunicata

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Cilia on gill bars of pharynx pull mucus into a sheet Particles trapped in sheet are worked into a rope and carried

back to the esophagus and stomach

Heart drives blood first in one direction, then in reverse Organisms also concentrate very rare elements, such as

vanadium, in dramatically high concentrations Nervous system has one nerve ganglion and a plexus of

nerves on dorsal side of pharynx


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Subneural gland samples incoming water and may have an endocrine function

Hermaphroditic with a single ovary and a single testes Fertilization is external Adult sea squirts

Retain 2 of the 5 chordate features: pharyngeal slits and endostyle

Tadpole larvae Have all 5 chordate characteristics

Larva does not feed, but swims awhile before attaching and developing into a sessile adult

Taxonomy

Subphylum: Urochordata (urocordado, tunicates, sea squirts, salps, ascidies)

Class: Appendicularia pelagic tunicates, apendiculria, oicopleura, oikopleura

Class: Ascidiacea ascidians, sessile tunicates, ascdia, ascidies, tuniqus sessiles

Class: Thaliacea pelagic tunicates, doliolum, salpa, taliceo

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Plan Estructural (Ascidiacea)

Cordados 1-19

Cordados 1-20


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Form and Function of Appendicularian (Larvacea) Resemble the larval stages of other tunicates

Each builds a delicate hollow sphere of mucus interlaced with passages for water entry

Phytoplankton and bacteria trapped on a feeding filter inside sphere are drawn into mouth through a tube

When filters become clogged with wastes, they are left behind and a new sphere is built

Paedomorphic Sexually mature individuals that retain the larval body form

of ancestors

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Appendicularians create a feeding current to filter food particles from the

surrounding water. The dotted arrows indicate the direction of the current

through the house.

Source: http://www.microscopy-

uk.org.uk/mag/indexmag.html?http://www.microscopy-

uk.org.uk/mag/artjan01/oiko.html

Cordados 1-25


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Form and Function of Thalacians Salps are pelagic with a lemon-shaped, transparent body

Pump water through body by muscular contraction rather than ciliary action

Alternate sexual and asexual generations

Increase in number rapidly with abundant food supply

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Cyclosalpa affinis (Chamisso, 1819).

A, B, Solitary zooid, dorsal view; C, D,

Aggregate zooid; C, Right side view;

D, Left side view. A.S., atrial siphon;

Br, branchial septum;

B.S., buccal siphon;

Dt, dorsal turbercle;

End, endostyle;

G, ganglion;

i.m., intermediate muscle;

Int, Intestine;

I-VI, body muscles;

Pd., peduncle;

St, stolon.

Scale bars: A, B=6 mm, C, D=3mm.

Taxonomic Study of Genus Cyclosalpa

(Thaliacea: Salpida: Salpidae) from Korea

Sunwoo Kim , Jung-Hye Won , Chang-Bae Kim

Animal Systematics, Evolution and Diversity.

2012. Oct, 28(4): 261-268

DOI

: http://dx.doi.org/10.5635/ASED.2012.28.4.261

ESPECIES EN COLOMBIA ASCIDIAS

Phallusia nigra

Microcosmus spp.

Pyura

Cnemidocharpa

Polyclinum

Symplegma

Distaplia

Cordados 1-32

Taxonomy

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Phylum: Chordata

Subphylum: Cephalochordata

Orden: Anfioxiformes

Familia: Branchiostomidae

Genero: Branchiostoma (21 spp) Epigonichthys (7 spp)

Trabajo para el ltimo 30% en una cartulina:

FICHA TAXONMICA DE LOS TAXONES ESTUDIADOS

Phylum: Cordados

Subphylum:

Superclase: ETC

Construirla grupo a grupo usando ITIS, de manera individual.

Cordados 1-34

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Subphylum Cephalochordata

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Diversity Lancelets

Slender, laterally flattened, translucent animals about 57 cm long

Live in sandy bottoms of coastal waters around the world

Originally bore the generic name Amphioxus, but by priority are now in the genus Branchiostoma Still referred to by general name, amphioxous

About 25 species of amphioxus are described 5 occur in North American coastal waters


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Food particles separated from mucus are passed into hepatic cecum where they are phagocytized

Filtered water leaves body by an atriopore Closed circulatory system is complex but lacks a heart

Blood is pumped by peristaltic contractions in ventral aorta, passes upward through branchial arteries in pharyngeal bars to paired dorsal aortas

Blood moves by microcirculation through tissues and returns to ventral aorta

Subfilo: Cefalocordado

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Cordados 1-39


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Blood lacks erythrocytes and hemoglobin and mainly transports nutrients

Hollow nerve cord lies above the notochord Pairs of spinal nerve roots emerge at each trunk segment Sense organs are simple, including an unpaired ocellus

that functions as a photoreceptor Anterior nerve cord is not enlarged, yet is homologous to

vertebrate brain


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Reproduction Sexes are separate

Gametes are set free in the atrium and pass out through atriopore

Fertilization is external

Cleavage is holoblastic and a gastrula forms by invagination

Larvae soon hatch and gradually assume the shape of adults


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Basic Plan Amphioxus possesses features that suggest the

vertebrate plan Cecum is a diverticulum resembling the vertebrate

pancreas in secreting digestive enzymes Trunk muscles resemble vertebrate patterns Possess basic circulatory plan of more advanced

chordates Many zoologists consider amphioxus a living

descendant of ancestors that gave rise to both cephalochordates and vertebrates Would make them the living sister group of the vertebrates

ORIGIN OF THE PHYLUM CHORDATA Hypothesis and evidences

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Origin

Hemichordata Echinodermata

LARVAE

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Origin

Neoteny

the growth rate of body form is slowed so that the animal does not attain the ancestral

adult form

Progenesis

Precocious maturation of gonads in a larval (or

juvenile) body that then stops growing

Post -displacement

developmental process is delayed

relative to reproductive maturation

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Origin

Origin

Cordados 1-52

Subfilo: Cefalocordado

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Cordados 1-54

Corte transversal de un cefalocordado a nivel farngeo

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Verde: Sistema nervioso, Rojo: Msculos, Violeta: Faringe, Fucsia: Gnadas, Puntos rojos: arteria subendostilar y aortas

dorsales

Observe la notocorda y la organizacin alternada de las barras farngeas con y sin celoma.

3-Protocordados

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