Identification of the endostyle
as a stem cell niche in a colonial chordate.
lucayanum [Male] Tail Pigment From Neurula Anterior Pigment Spot From Early Larva Larval Mouth Opposite Endostyle
Preoral Ciliated Pit (4) 8 [+ or -] 0.5 [micro]m Gill Slit 1 Deflection (5) Right24 [+ or -] 7.7[degrees] Right Gill Slit 2 Deflection (5) 7 [+ or -] 5.4[degrees] Right Anus Deflection (5) 14 [+ or -] 7.5[degrees] Right A.
In Phase 4, when early signs of stigmata can be seen but the endostyle has not yet reached its typical adult form, proliferation is concentrated in the floor of the dorsal tube, leaving an unlabeled dorsal area (Fig.
For further examination and staging of development of the thoracic bud, including the neural complex, we also analyzed timing of the appearance of ciliation in the endostyle and ciliated funnel by the presence of acetylated tubulin (Fig.
From studies based primarily on the unitary stolidobranch Styela clava, Ermak (1982) reported renewing cell populations in various epithelia including those of the ciliated funnel, endostyle, stigmata, esophagus, and stomach; these are areas in which proliferation was also noted in D.
To investigate the growth rate of the endostyle at varying food concentrations, animals were cultured under standard and limited food regimes at 15 [degrees]C.
BrdU pulse-chase feeding experiments were carried out to follow DNA replication in the endostyle. BrdU (Sigma) was dissolved at 100 [micro]mol [l.sup.-1] in 1-liter sterile-filtered (0.2 [micro]m) seawater.
After fixation, endostyle and accompanying oral glands from adult animals were manually microdissected, chromatin was stained with propidium iodide, and tissue was mounted on microscope slides.
The enteropneust pharynx should not be considered less specialized than that of the chordate pharynx on the basis that it lacks an endostyle
organ that produces a mucous net.
In addition, lysosomal activity was inferred to be an important component in cell death in some instances, as autophagosomes were frequently observed within cells of the endostyle
near the ventral sinus, independently of the necrotic changes described above (Fig.
It is commonly considered that the endostyle of lower chordates may be a homolog and primitive antecedent of the vertebrate thyroid gland, mainly because the organ incorporates iodine (Barrington, 1957, 1958; Salvatore, 1969).
In addition, lower chordates (including tunicates, amphioxus, and lampreys) share an endostyle. We have emphasized that these hallmarks of the chordate body plan apparently evolved with the emergence of creatures resembling tadpole larvae (Satoh, 1995; Satoh and Jeffery, 1995).