CancIuding remarks
175
treatment
(Levavi—Zermonsky and Yaron)° In fact, this simple method has been
adopted already by certain hatcheries in Israel (Yaron).
However, the sensitivity of the oocytes to gonadotropin (GTH) may not be
fully reflected by the position of the GV. A more accurate way would be the
in
vitro examination of ovarian response to the addition of GTH (Epler et al.).
The sensitivity of the oocyte was found to fluctuate in a diurnal rhythm, coin—
ciding with that of the circulating GTH. The daily peak of GTH occurs at 2 p.m.
in Poland
(Bieniarz) but it peaks in the "Dor—70" carp in Israel around ]] p.m.
(Levavi Zermonsky and Yaron). There is not enough information to allow a con—
clusion whether this difference should be attributed to the difference in
daylength or temperature between these countries at the time the observations
were
made, to genetic differences between the two carp populations, or other
possible factors. The in vitro determination of ovarian sensitivity to gona—
dotropin still
proper application to the conditions and routine
of the hatchery.
The
technique of artificial fertilization in cyprinids using the milt
extrated from one male
to
the spawn of one female seems,
nowdays, rather unso—
phisticated. Research is now in progress to objective1y assess sperm motility
and viability (Gatty et al.). The amount of sperm produced and the volume of
milt extractable after hypophysation have been determined together with the
optimal amount of sperm required for successful fertilization in the common
carp
(Saad and Billard).
.
The last part of the discussion has dealt with the possible involment
of pheromones in carp reproduction. At high temperature, testicular tissue of
the carp produce in vitro a large proportion of testosterone glucuronide.
These results, tâEë together with the recent findings of Lanbert's group in
the catfish, raise the possibility that this or other steroid glucuronides,
secreted in nature by the males, may act-as pheromones that induce a surge of
GTH in the surrounding females, leading to the final ovarian maturation, ovu—
lation and spawning. If this will prove to be the case also in cyprinids,
future research should be directed toward the discovery of the pheromones re—
ceptors in the olfactory system in the fish. Immunocytochemical studies in the
goldfish have demonstrated the presence of GnRH in cells and tracts leading
from the olfactory bulbs and nerves to the ventral telencephalon and the ven—
trolateral preoptic area of the hypothalamus (Kah). There is still a gap bet—
ween
the findings on carp testicular glucuronides and the putative olfactory
receptors of male pheromones and GnRH containing brain structures in the
females. However, one would wonder whether future research on reproduction may
not lead to a new direction, the use of synthetic fish pheromones for the arti—
fiCial propagation of carp and related species.
In summary,
the well attended session and the Vivid discussion
have clari—
fiEd the fact that the State of the Art in cyprinids reproduction leaves much
ü)be desired as compared with the situation in salmonid fishes.
The Situation
ù1cyprinids other than the goldfish and the common carp
is
even
less
satis—
factory. Problems of special interest are the initiation
of puberty infcultu—
red CYprinids, especially in the temperature climate;
the
ova—
rian sensitivity to induced spawning; calibat10n of agents Utlllze ln
ËPaW l
nh@ induction; gamete management for optimal surv1val, and the SËUdY 0
ear Y
develomental stages.
‘
B.
Breton
Z.
Yaron
175
treatment
(Levavi—Zermonsky and Yaron)° In fact, this simple method has been
adopted already by certain hatcheries in Israel (Yaron).
However, the sensitivity of the oocytes to gonadotropin (GTH) may not be
fully reflected by the position of the GV. A more accurate way would be the
in
vitro examination of ovarian response to the addition of GTH (Epler et al.).
The sensitivity of the oocyte was found to fluctuate in a diurnal rhythm, coin—
ciding with that of the circulating GTH. The daily peak of GTH occurs at 2 p.m.
in Poland
(Bieniarz) but it peaks in the "Dor—70" carp in Israel around ]] p.m.
(Levavi Zermonsky and Yaron). There is not enough information to allow a con—
clusion whether this difference should be attributed to the difference in
daylength or temperature between these countries at the time the observations
were
made, to genetic differences between the two carp populations, or other
possible factors. The in vitro determination of ovarian sensitivity to gona—
dotropin still
proper application to the conditions and routine
of the hatchery.
The
technique of artificial fertilization in cyprinids using the milt
extrated from one male
to
the spawn of one female seems,
nowdays, rather unso—
phisticated. Research is now in progress to objective1y assess sperm motility
and viability (Gatty et al.). The amount of sperm produced and the volume of
milt extractable after hypophysation have been determined together with the
optimal amount of sperm required for successful fertilization in the common
carp
(Saad and Billard).
.
The last part of the discussion has dealt with the possible involment
of pheromones in carp reproduction. At high temperature, testicular tissue of
the carp produce in vitro a large proportion of testosterone glucuronide.
These results, tâEë together with the recent findings of Lanbert's group in
the catfish, raise the possibility that this or other steroid glucuronides,
secreted in nature by the males, may act-as pheromones that induce a surge of
GTH in the surrounding females, leading to the final ovarian maturation, ovu—
lation and spawning. If this will prove to be the case also in cyprinids,
future research should be directed toward the discovery of the pheromones re—
ceptors in the olfactory system in the fish. Immunocytochemical studies in the
goldfish have demonstrated the presence of GnRH in cells and tracts leading
from the olfactory bulbs and nerves to the ventral telencephalon and the ven—
trolateral preoptic area of the hypothalamus (Kah). There is still a gap bet—
ween
the findings on carp testicular glucuronides and the putative olfactory
receptors of male pheromones and GnRH containing brain structures in the
females. However, one would wonder whether future research on reproduction may
not lead to a new direction, the use of synthetic fish pheromones for the arti—
fiCial propagation of carp and related species.
In summary,
the well attended session and the Vivid discussion
have clari—
fiEd the fact that the State of the Art in cyprinids reproduction leaves much
ü)be desired as compared with the situation in salmonid fishes.
The Situation
ù1cyprinids other than the goldfish and the common carp
is
even
less
satis—
factory. Problems of special interest are the initiation
of puberty infcultu—
red CYprinids, especially in the temperature climate;
the
ova—
rian sensitivity to induced spawning; calibat10n of agents Utlllze ln
ËPaW l
nh@ induction; gamete management for optimal surv1val, and the SËUdY 0
ear Y
develomental stages.
‘
B.
Breton
Z.
Yaron