Spermatogenesis of Encyclometra japonica is of rosette type, wherein the dividing cells remain attached to each other by a short cytoplasmic stalk. Successive mitotic divisions of primordial germ cells give rise to primary spermatogonia, which again by three mitotic and two meiotic divisions give rise to the 32-celled spermatids stage. Six bivalents are clearly visible during metaphase-I. A few peculiarities like pyknosis, primary spermatocytes and vacuoles in the elongating nucleus of the spermatids have been observed. A centriole appeared between the pointed end of the nucleus and the cytoplasmic boundary. The cytoplasm of the spermatid grows out from the region of the centriole in the form of a filament, the sperm tail. Each sperm consists of a nuclear head and an elongated cytoplasmic tail.
Spermatogenesis
in the hermaphroditic digenea has attracted the attention
of several workers. Dingler [1]and John [2] found some clusters
of globules, scattered at the periphery of the testis. Markell
[3] and John [2] observed some ball like structures, mostly
at the periphery, but occasionally in the lumen of the testis.
Markell [3] considered them to be the vacuolated cells while
John [2] considered them to be pyknotic primordial spermatogonia.
Chen [4] noticed some vacuolated cells with clear nuclei and
considered them to be the degenerating spermatogonia. Anderson
[5] noticed few clusters having six cells, which he regarded
as pyknotic primary spermatocytes. Yosufzai [6], Guraya and
Gupta [7] and Saxena [8] reported a central cytoplasmic disc,
the blastophore. Keeping all these peculiarities in mind,
the author studied the spermatogenesis in Encyclometra
japonica.
Living
specimens of E. japonica were collected from
the stomach of water snake, Tropidonotus piscator. The
parasites were dissected under a stereoscopic binocular microscope
and the testes were smeared, to obtain the entire rosettes
of different stages of spermatogenesis. Many fixatives like
Bouin's acetic sublimate, Carnoy's 6:3:1 and Carnoy's 1:3
were used. However, the smears fixed in Carnoy's 1:3 and acetic
sublimate stained with Iron Hematoxylin, Feulgen and Methyl
Green Pyronine gave good results. A few specimens were fixed
and stained with aceto-orecin. For microtomical preparations,
E. japonica were fixed in acetic sublimate and Carnoy's,
and processed for embedding in paraffin; and sections of 5mm
or 6mm were cut and stained with Heidenhain's Iron Alum Haematoxylin,
and lightly counter stained with eosin. The smears and specimens
fixed for microtomy in acetic sublimate were treated with
iodine in 70% alcohol to remove mercury. The drawings have
been drawn to the same scale with the aid of camera lucida
to elucidate the micro photographs. |
