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INDIAN JOURNAL OF VETERINARY SCIENCE AND ANIMAL HUSBANDARY [VOL. XXIX, PART I
channel with wire netting. Even if the presence of the larvae of these fishes in this water
is looked upon as having been brought by the infeeding channel from extraneous sources,
the result of the periodical examination of the gonads is sufficient to suggest the breeding of
these fishes in this tank. Hamidkhan [1924] in his studies on the breeding habits of some
major carps states that even when 'brood fishes' are introduced into confined waters they
fail to breed, and the mature eggs degenerate in the ovaries where the environmental con-
ditions are not favourable for breeding. Total degeneration of oocytes is unknown in C. reba.
The gonadial cycle is divided into six stages, based on the classification of Bennett,
as cited by James [1946]. Preference is given to Bennett's classification over that of Jones [1940]
in the case of male since in C. reba the growth stages are not so elaborate as those of Salmo salar
[Jones, 1940].
The yellow pigment masses (remnants of corpora lutea) which are readily visible
through the transparent ovary form the discriminating morphological feature of the depleted
Stage I ('immature') ovary from the immature ovary of a juvenile fish. As in the case of
C. reba, atretia of some growing oocytes has been reported in several fishes [Cunningham, 1897;
Matthews, 1938; and James, 1946]. This has been studied in more detail by Bretschneider
and Duyvene de Wit [1947] in Rhodeus amarus. These authors have given a new interpreta-
tion of this process and named these oocytes as pre-ovulation corpora lutea. In Phoxinus laevis,
Bullough [1940] observed that the primary oocytes belonging to the primary growth phase
occur in the mature ovary form the stock for the fresh crop. Hickling and Rutenberg [1936]
record that in some adult fishes there is a general stock of yolkless and transparent eggs which
give rise to the new generation of oocytes after depletion of the ovary. In C. reba, the nests
of transparent oocytes are so few in Stage IV ovary that it can only form a very small portion
of the new crop. However, in the depleted ovary, new nests of small oocytes are proliferated
from the ovigerous lamellae which seem to replenish the ovary.
Spermatogonia with round and polymorphic nuclei are encountered in C. reba. But unlike
Ichthyophis glutinosa [Seshachar, 1936] their ratio during defferent growth periods of the
testis could not be arranged with regularity to give a difinite interpretation for this pheno-
menon. The solitary spermatogonia which persist in the mature testis (Stage D) divide during
stages E and F, and this strengthens the probability of these forming the resting mother
germ cells for the new crop of spermatogonia, as in the case of Plecoglossus ativetis [Kazuo Suzuki,
1939 and Salamander Hargitt, 1924].
SUMMARY
The morphological and seasonal histological changes occurring in the sexual cycle
of C. reba are studied.
This minor carp breeds during July to September in the Annamalai University re-
servoir. This period coincides with the setting in of the monsoon.
The condition factor computed reaches its maximum in both male and female during
the spawning period. In the female, the fall in the condition factor is abrupt whereas in the
male it is gradual.
The replenishment of ovary after depletion is chiefly through the proliferating nest
of germ cells which are seen in the ovigerous lamellae; however, the few resting nests present
in the mature ovary may also contribute. The resting germ cells of the testis apparently form
the parent cells of the new generation of germ cells in the spent testis.
During certain stages of growth in the testis of C. reba, spermatogonia with round
and polymorphic nuclei are present side by side. Rare occurrence of amitosis in the spermato-
gonia is also noted.