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Protochordates

Branchiostoma lanceolatum: Amphioxus, the ‘’, Cephalochordata And the origins of the : Hemichordata & Urochordata Parazoa No tissues Porifera

Eumatazoa Radiata / Diploblastic

Bilateria Acoelomates Platyhelminthes/Nemertea Triploblastic

Pseudocoelomates Nematoda/Rotifera

Coelomates Lophophorates//Annelida/Athropoda

Deuterostomes /Echinodermata/Chordata Determinate-Spiral as in Protostomes

Blastopore becomes anus, not mouth Starfish embryos: – zygote – – blastula – gastrula – bipinnaria. mouth

anus

Echinoderm bipinnaria links them to protochordates & us!

Eumetazoa: : Eucoelomata- cont’d

Phylum Hemichordata Chordata: Subphylum Urochordata Subphylum Cephalochordata Subphylum Vertebrata Craniata Jaw Lower & vertebrae & Head No sessile adult sessile No Vertebrates No Lo.Jaw No Cord, Cord,

Agnatha Nerve Hollow Dorsal Chordata Deuterostomes Branchial slits, Branchial Cephalochordata Indeterminate, Radial Radial Indeterminate, Cleavage

Urochordata Protochordates ‘Hemichordata’

Echinodermata Deuterostomes closer to Vertebrates Vertebrates to closer

Protostomes of simple Phylogeny A than than 2008: DNA sequences showed sequencesDNA 2008: Urochordates Subphylum Hemichordata: Balanoglossus Hemichordata: Balanoglossus: -LS of “Head” DHNC

Pharyngeal gill slits proboscis

glomerulus

? ‘Notochord’/stomochord

collar Halocynthia pyriformis

Subphylum Urochordata In Larvaceae : gonads & no sessile stage

Molgula occidentalis Esophagus

Tentacular Filters Cut Edge of Mantle,tunic around Incurrent removed Siphon

Ant

ENDOSTYLE 6 4 6 pairs of Branchial Pleats Molgula occidentalis: sandy tunic removed, organs show through ‘mantle’

Hemal vessels

L Food Filled Intestine

L. Gonads R R. Testes Hermaphrodite=a pair of ovaries & testes R. Ovary Renal Sac Finger print-like pattern of stigmata in Molgula’s Pharyngeal Gill Slits

Filtering Around incurrent siphon 5 mm spicules

Didemnum candidum: A colonial Ascidian; an encruster Ectinascidea sp. w/ Gill Slits Ganglion or ‘brain’

tunic Gut (intestine)

stomach

esophagus atrium Gonads & ducts Blood vessel in ‘pedicle’ Anus & sperm duct pore Clavelina picta

Distaplia sp. larva (Tunicate) Larvaceae: ‘Oikopleura’? Tunicate larva Tunicate larva Urochordata: Thaliacea: Salpa or Doliolum sp., ~1 mm gonad

Atrial siphon tunic

gut

Buccal Muscular siphon Endostyle rings

‘Salp’- Doliolum sp. in tow net ~1mm – Thaliacea(Urochordata) Illustrations of burrowing lifestyle of adults in sediment, filter feeding for plankton, from internet gracilens was the oldest known ancestor from the 520 Ma middle Cambrian - of B.C. Canada

Artist’s rendition

fossil mbl

Amphioxus

Branchiostoma floridae.: Larva in marine plankton tow off Sarasota, FL

‘eye’ spot notochord

Cilia in pharyngeal slits Hatschek’s groove & pit

Pigment (‘eye’) Fin-ray box spot DHNC notochord pharynx Pharyngeal, Visceral or Myosepta between ocelli Branchial Bar Myomeres (‘Myotomes’) intestine

Oral Hood Velum & velar pore Atrial pore or Anus Digestive atriopore Oral cirri Wheel Branchial Endostyle Ceacum or’’ organ (Visceral, Pharyngeal) Slit – exits to surrounding Atrium

Male w/ Testes

Female w/ Ovaries Cilia in

notochord

Larval amphioxus in Sarasota, FL plankton net tow~1mm Ileocolic ring, a concentration of intestinal cilia, because there is no smooth muscle Dorsal fin DHNC Notochord gut Post anal tail & caudal fin

Anus intestine Path of water through mouth, pharynx, slits Atrial pore (water exiting slits, & atrium to pore leaves atrium here)

‘Caecum’, ‘Liver’ or midgut cecum

R L Wheel organs - ciliated Metapleural folds Myomeres Ocelli Hatschek’s pit & groove (ant. Dorsal hollow nerve Pituitary?) cord Fin-ray boxes Pigment spot

Fin

No cephalization

Velar tentacles Notochord

Wheel organ w/ cilia Ciliated oral cirri Aperture in velar Oral hood muscle wall Myosepta between Myomeres

Fin-ray boxes

notochord

velum

Branchial SLIT Branchial BAR Light sensitive receptors above notochord & in center of to DHNC: OCELLI Side view, optical section Horizontal muscle fibers in notochord maintain hydrostatic pressure and thus firmness of notochord

notochord

OCELLI

Dorsal, hollow nerve cord

Cross section notochord Cilia on Bars

Pharynx

Blood vessels ovary

Skeletal rod Dorsal fin Epibranchial groove

Caecum

Endostyle

Food particles brought in through the oral hood and ‘mouth’ adhere to the endostylar and the mucus-food bolus is passed by the cilia upwards to the epibranchial groove by the cilia of the branchial bars; hence backward to the ciliated gut. Meanwhile the oxygenated water passes through the slits the atria and out the atrial pore (atriopore). The caecum is believed to produce enzymes for digestion. Epibranchial groove

DHNC

® Sections of male (testes) N Left & female Atrium (ovaries) Right, section is posterior digestive digestive part of caecum”liver” caecum”liver” branchial slits and anterior digestive Pharynx caecum”liver”

testes ovary

endostyle SOENOCYTES (Podocytes) the ‘flame cells’ or nephridia of the Amphioxus

Doral Aorta branch to ‘glomerulus’ ®

Nuclei of Solenocyte = Podocyte

Atria

PHARYNX

Bar Willey, 1894 Area of next slide caecum Cephalic Caudal

intestine

Iliocolic band of concentrated cilia to atria move digestive bolus to anus, because the ‘intestine‘ has no muscle for peristalsis; note bolus in center.

Fin-ray Epidermis box Dermis

DHNC Myomeres Myosepta Notoch- ord

Hatschek’s groove Buccal Cirri

Oral hood blastula

invagination notochord

mesoderm Neural fold & tube blastopore

coelom

See next archenteron page

After Cerfontaine & Hatschek, from Kellicott, 1913