ULTRASTRUCTURE OF DEVELOPING AMPHIBIAN EGG 151
B. Cytoplasmic Organelles
The classification of the cytoplasmic constituents as organelles and inclusion bodies is to some extent an arbitrary one. Although the latter elements refer to structures elaborated by the cell, it is probable that they have
a significance beyond that of storage of inert material. Thus, Gross and
Gilbert (1956) suggested that the yolk platelet should be considered an
organelle since its structural and chemical complexity suggests a concomitant functional complexity
The amphibian oocyte contains (Fig. 12) the usual cellular organelles
such as mitochondria and the Golgi complexes. In addition, the oocyte
contains specialized organelles such as the annulate lamellae and vesicles.
1.
Mitochondria
In Triturus viridescens clusters of mitochondria are present in the cytoplasm (Fig. 13). These organelles, when examined at higher magnification
(Fig. 14), exhibit the typical mitochondrial characteristics of possessing an
outer and inner membrane, as well as cristae, which extend in part or in
whole across the width of the organelle.
In 1848, Cramer described a complex structure in the cytoplasm that
later became known as the yolk nucleus or Balbiani body. This organelle
composite is most frequently found to be present in young oocytes. With
the onset of vitellogenesis, it usually disappears. The yolk nucleus was
studied extensively with light-microscope techniques. These studies have
been summarized by Brächet (1950, 1960) and by Raven (1961).
In eggs from nonamphibian forms, both invertebrates and vertebrates,
studies with the electron microscope have described the yolk nucleus as
consisting of different organelle composites in different forms. In this connection, rough-surfaced membranes, clusters of Golgi cisternae, arrays of
annulate lamellae, and Golgi-mitochondrial clusters have been described
as the structural elements of the yolk nucleus (see reference in Wartenberg,
1962). Kemp (1953) examined oocytes from the frog Rana pipiens and
described clusters of lipochondria and mitochondria as making up the yolk
nucleus. Its existence in this species is, however, denied by Ward (1962).
Wartenberg (1962) investigated the eggs of the frog Rana esculenta as well
as the toad Xenopus laevis. He described the yolk nucleus as consisting of
large masses of mitochondria associated with optically empty vesicles. In
FIG. 12. A low-power electron micrograph of a representative region from the
cytoplasm containing the usual organelles (and inclusion bodies). These include
mitochondria (m), a cluster of cisternae representing the Golgi complex (gc), an
isolated annulate lamella (a), and vesicles (v). Among the inclusions evident are
yolk platelets (y) and a lipochondrion (1). χ 42000.
B. Cytoplasmic Organelles
The classification of the cytoplasmic constituents as organelles and inclusion bodies is to some extent an arbitrary one. Although the latter elements refer to structures elaborated by the cell, it is probable that they have
a significance beyond that of storage of inert material. Thus, Gross and
Gilbert (1956) suggested that the yolk platelet should be considered an
organelle since its structural and chemical complexity suggests a concomitant functional complexity
The amphibian oocyte contains (Fig. 12) the usual cellular organelles
such as mitochondria and the Golgi complexes. In addition, the oocyte
contains specialized organelles such as the annulate lamellae and vesicles.
1.
Mitochondria
In Triturus viridescens clusters of mitochondria are present in the cytoplasm (Fig. 13). These organelles, when examined at higher magnification
(Fig. 14), exhibit the typical mitochondrial characteristics of possessing an
outer and inner membrane, as well as cristae, which extend in part or in
whole across the width of the organelle.
In 1848, Cramer described a complex structure in the cytoplasm that
later became known as the yolk nucleus or Balbiani body. This organelle
composite is most frequently found to be present in young oocytes. With
the onset of vitellogenesis, it usually disappears. The yolk nucleus was
studied extensively with light-microscope techniques. These studies have
been summarized by Brächet (1950, 1960) and by Raven (1961).
In eggs from nonamphibian forms, both invertebrates and vertebrates,
studies with the electron microscope have described the yolk nucleus as
consisting of different organelle composites in different forms. In this connection, rough-surfaced membranes, clusters of Golgi cisternae, arrays of
annulate lamellae, and Golgi-mitochondrial clusters have been described
as the structural elements of the yolk nucleus (see reference in Wartenberg,
1962). Kemp (1953) examined oocytes from the frog Rana pipiens and
described clusters of lipochondria and mitochondria as making up the yolk
nucleus. Its existence in this species is, however, denied by Ward (1962).
Wartenberg (1962) investigated the eggs of the frog Rana esculenta as well
as the toad Xenopus laevis. He described the yolk nucleus as consisting of
large masses of mitochondria associated with optically empty vesicles. In
FIG. 12. A low-power electron micrograph of a representative region from the
cytoplasm containing the usual organelles (and inclusion bodies). These include
mitochondria (m), a cluster of cisternae representing the Golgi complex (gc), an
isolated annulate lamella (a), and vesicles (v). Among the inclusions evident are
yolk platelets (y) and a lipochondrion (1). χ 42000.