ISSN:
1432-0878
Keywords:
Fertilization
;
Gametes
;
Echinoid
;
Echinarachnius
;
Ultrastructure
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Medicine
Notes:
Summary The morphology of gametes of a representative echinoid, Echinarachnius parma were investigated ultrastructurally with particular emphasis on gamete interaction during fertilization. The acrosomal region of the spermatozoon is characterized by the presence of two components: an acrosomal vesicle and periacrosomal materials. The acrosomal vesicle, which is completely bounded by a limiting membrane, is surrounded by periacrosomal materials. Nuclear and mitochondrial regions of the spermatozoon are also described briefly. The ovum is surrounded by two extraneous coats: an outer jelly layer and an inner vitelline envelope. Pigment cells are present within the outer jelly layer. Ooplasmic organelles and inclusions including cortical granules and the female pronucleus are described. Spermatozoa undergo the acrosomal reaction in the vicinity of mature ova. Events of acrosomal reaction, including dehiscence of the acrosomal vesicle and acrosomal tubule formation, are described and summarized schematically. Acrosomal vesicle contents remain adherent to the outer surface of the tubule membrane. Primary binding of the spermatozoon to the surface of the ovum is accomplished by the establishment of morphological continuity between this extracellular coat and the vitelline envelope of the ovum. It is suggested that the species specificity of fertilization resides in this primary binding of gametes. Membrane fusion, between the tip of the acrosomal tubule and the colemma, follows primary binding and cytoplasmic continuity of the gametes is thereby established. It is concluded that the early events of fertilization in Echinarachnius parma generally conform to the Hydroides-Saccoglossus pattern of the Colwins (1967).
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00220142
Permalink
