FACTORS IN MORPHOGENESIS OF
REGENERATING FRESH-WATER PLANARIAf
T H . L E N D E R
Universite de Paris, Faculte des Sciences, Centre d^Orsay,
Laboratoire de Biologie Animale, S.P.C.N.,
France
I. Introduction
305
I I . The Neoblasts of Fresh-Water Planaria
306
A. Cytological Study of the Neoblasts
306
B. Neoblasts of the Regeneration Blastema
308
C. Planarian Neoblasts with Limited Regeneration Capacity
311
I I I . Differentiation Factors
312
A. Determination of the Blastema
312
B. Organ Differentiation in Regeneration
313
VI. Conclusion
326
References
329
I. Introduction
Most fresh-water planarians have a very remarkable capacity for
regeneration. Their bodies can be cut into fragments of several tenths of
a millimetre and each segment isolated in this way reconstitutes a
complete individual. Three principal phases may be distinguished during
regeneration: the occlusion of the wound, the formation of the regeneration blastema, and the differentiation of the organs.
The wound closes by the drawing together of its edges. The damaged
tissues are eliminated and several hours later a thin structureless membrane covers the wound.
Below this membrane the regeneration cells or neoblasts accumulate
and build up an unpigmented blastema.
When the blastema attains a certain size, the histological differentiation of the tissues takes place. The blastema becomes pigmented and
continues to enlarge until it reaches the size of the excised segment.
The morphogenesis of the fresh-water planarians during regeneration
is thus connected with the presence of neoblasts which form a blastema
in which the tissues differentiate. In recent years, numerous investigations have been devoted to these problems. This review will attempt to
set forth our current knowledge on the neoblasts and on the causation of
organ differentiation.
f Translated by Dr. Erich Hirschberg, Columbia University, New York.
305
REGENERATING FRESH-WATER PLANARIAf
T H . L E N D E R
Universite de Paris, Faculte des Sciences, Centre d^Orsay,
Laboratoire de Biologie Animale, S.P.C.N.,
France
I. Introduction
305
I I . The Neoblasts of Fresh-Water Planaria
306
A. Cytological Study of the Neoblasts
306
B. Neoblasts of the Regeneration Blastema
308
C. Planarian Neoblasts with Limited Regeneration Capacity
311
I I I . Differentiation Factors
312
A. Determination of the Blastema
312
B. Organ Differentiation in Regeneration
313
VI. Conclusion
326
References
329
I. Introduction
Most fresh-water planarians have a very remarkable capacity for
regeneration. Their bodies can be cut into fragments of several tenths of
a millimetre and each segment isolated in this way reconstitutes a
complete individual. Three principal phases may be distinguished during
regeneration: the occlusion of the wound, the formation of the regeneration blastema, and the differentiation of the organs.
The wound closes by the drawing together of its edges. The damaged
tissues are eliminated and several hours later a thin structureless membrane covers the wound.
Below this membrane the regeneration cells or neoblasts accumulate
and build up an unpigmented blastema.
When the blastema attains a certain size, the histological differentiation of the tissues takes place. The blastema becomes pigmented and
continues to enlarge until it reaches the size of the excised segment.
The morphogenesis of the fresh-water planarians during regeneration
is thus connected with the presence of neoblasts which form a blastema
in which the tissues differentiate. In recent years, numerous investigations have been devoted to these problems. This review will attempt to
set forth our current knowledge on the neoblasts and on the causation of
organ differentiation.
f Translated by Dr. Erich Hirschberg, Columbia University, New York.
305