抄録
The spermatozoa obtained from the mature Kuruma prawn Penaeus japonicus BATE wereobserved with the scanning electron microscope. Seminal fluid was taken out, respectively, of the spermatophore in the male and of the spermatophore inside the seminal receptacle in the female.
The spermatozoa from male and female are identical in shape and size. The external mor-phology of the spermatozoa of P. japonicus consists of a hemispherical head (main body)of about 4.2 to 5.2μm in maximal diameter and an extremely slender tail (or spike) of about 5.5 to 6.6μm long, which projects from the convex side of the head. The basal side of the head is intensively hollowed at the central region. The whole surface of the head is rough whereas that of the tailis smooth.
The spermatozoa of Decapoda are so far separated into the unistellate sperm of natantians and the multistellate sperm of reptantians. This separation is applicable to the present species since the spermatozoa of P. japonicus, which belongs to natantia, are typically unistellated.
