Page 357
Radioresistance of Fish
SUMMARY
DISCUSSION
tance o
ve catterns of embryonic radioresis
&
amphibia
ep ahes and
a be
under consideration may
be
correspondence
veayen tathematically with fair
7
Table 6 shows the available repecies.
. aac
either at
Pe at vethal dose-50 determined
ntage developSota OF somewhat later upon perce
Vo vatehing for fish, or to metamorphosis for
when
i
irradiated.
Disregarding the data for Misgurnus which
ing
sj statistical significance, and consider
and the four pairs of values for salmon
\
Trout based on both calculated and estimated
show a
ethal dose-50's, the data of Table 6
one
ean and standard error lethal dose-50 for the
recent (logarithmic Y-intercept) level of incu-
Ration. of 223 + 34 roentgens. The nine correspondWing coefficients of regression averaged 0.431 and
anged from 0.331 to 0,611, with probability values
t or beyond the 0.08 level when tested with "t”
e preneuruilation and postneurulation regressions
or amphibia are of comparable statistical
Bignificance.
:
For salmon and trout a comparison was made beween calculated and estimated values of the lethal
Fdose-50 given by the regressions.
[i$
Experimental data and analysis of published
results indicate that the radioresistance of the
embryos of fishes and amphibia increases with advancing development in a way that may be expressed
mathematically.
Eggs of silver salmon were xirradiated in 23 stages of development randomly
selected from one-cell to late-eyed stage, at each
stage using seven dosages incremented by a factor
of about two.
and estimated from graphs.
The regression of log
lethal dose-50 in roentgens upon log percentage
of incubation attained at time of irradiation was
computed at both hatching (Y = 240 x9.42) and at
150 days (Y = 125 x0.33).
idose-50.
determined by t .055b = 0.194 and 0.188, with 18 and
19 degrees of freedom respectively.
The regressions
represent general trends rather than the most sensitive
stage.
Estimates from the literature give similar relationships for rainbow trout, Fundulus and Misgurnus,
although the regression for Misgurnus was non-signifi-
cant.
Amphibian radioresistance increased very slowly
from fertilization to neurulation, and then sharply
from neurulatiom almost to metamorphosis.
Figures 2 and
REFERENCES
lethal
The slopes of the lines do not differ
isignificantly,
however, when regression coeffi-
fclents are compared by the method of Fisher (1946,
ip. 140).
i
Since time is required for radiation to take
effect,
the apparent increase in radioresistance
Relyaeva, V.N.. and G.L. Pokrovskaya.
1957.
Arrest of
mitosis by X-rays at early developmental stages in
loach spawn.
Doklady Akad. Nauk SSSR 119: 149-153.
Belyaeva, V.N.
and G.L. Pokrovskaya.
1958.
Changes
in the radiation sensitivity of loach spawn during
the first embryonic mitoses.
Doklady (Biol. Sci,
Section) Acad. Sci. SSSR 125:
iwith advancing stage of development of an organ-
ism, is in part a function of the decreasing time
interval between irradiation and the stipulated
etime of determination of the lethal dose-50. The
fghortening of this interval loses importance, howf@ver, when the lethal dose-50 is determined at an
fappreciably later stage for doses administered begfore hatching.
Because of the decreased mortality
grate between hatching and either yolk sac absorp-
:tion (trout) or 150 days post-fertilization (salmon),
68-74,
Fisher,
the increased resistance in the
later stages is real rather than apparent.
:
Although variability in early radioresistance
fis apparently only Slightly species dependent ,
variation in radioresistance is nevetheless believed to occur as a result of difference due to stage
of development, especially in the early embryonic
pHtanes. Fitting of straight lines to our observaeons represent ing random sampling of stages is not
5
preclude the existence of great deviations
senece by developmental processes within this
gerneral trend.
Henshaw (1940, p. 919) showed for
; nea urchin Arbacia that the resistance
fluctua-
@ from ye Feilization,
actors or twothrough
to three in a cyclic manner
the
ll:
during ene nt oF the egg of
Misgurnus fossilis
St 81x
pthe eariy
-:
ptried (5 dincern an
pow values
of
cetha]
hours after fertilizatio
n,
dose -50
Pperioda of SUR
E eDTIDIity
Pphane of aitusi
s
Although
y With
pha
peentai
ilver salmon we have
Irwin,
Dy
cur
data.
Effect
16-38.
J.0.,
and E,A,
Cheeseman,
1939.
On an approxi-
mate method of determining the medial effective
dose and its error,
sponse.
Karber, G.
in the case of a quantal re-
J. Hygiene 39(5): 574-580.
1931.
Beitrag zur kollektiven Behandlung
Pharmakologischer Reihenversuche,
Path. Pharmak.
162: 480-483.
Neifakh, A.A,, and N.N. Rott.
1959.
Arch.
exptl.
Synchronization
of cell division in early embryos of the loach
Misgurnus fossilis by the action of a lower temp-
erature,
Doklady (Biol. Sci. Section) ‘Acad,
Sci., SSSR (1-6): 256-258.
Neifakh, A.A., and N.N, Rott.
1958.
The ways in which
radiation damage appears in early development in
In
fish.
Rugh,
Doklady Akad. Nauk SSSR 119(2): 261-264.
R.
1954.
The effect of ionizing radiations on
amphibian development.
J. Cell. Comp. Physiol.
43(suppl. 1): 39-67.
of mitosis or other
stayes undoub
ibte
t dly exists, it
is not
4ore Study
of the early cleavp Bee period is nee
ded.
: Bhoesr
1958.
Henshaw, P.8.
and I. Cohen.
1940.
Further studies on
the action of roentgen rays on the gametes of
Arbacia punctulata.
IV.
Changes in radiosensitivity during the first cleavage cycle.
Am. J.
Roentgenol.
Radium Therapy 43(6): 917-920.
are
accompOBled hy
.involving abouc
five-fold
fluctuation in the radioresistenee
to
1946.
Statistical Methods for Research
Oliver and Boyd, Edinburgh.
xv, 354 pp.
of ionizing radiation on the development and reProduction of fishes,
Voprosy Ikthiologil
p Ret fakh
and Rott (1958, Figure 3,curve1)ingicat;
af the synchronous early cleavages
c
iH
R.A.
Golovinskata, K.A., and D.D. Romashov.
‘Slightly lower than at hatching (Figure 1, experiThus,
192-195.
Finney, D.J.
1944.
The application of the probit
method to toxicity test data adjusted for mortality in the controls.
Ann. Appi. Biol. 31(1):
ithe lethal dose-50's at the later stages were only
ment 23).
These regression coef-
ficients (the exponents of X) had confidence limits
and Table 6 show the value of the estimated,
tending to exceed that of the calculated,
:
Lethai dose-50's at hatching and at
150 days post-fertilization were both calculated
Rugh,
R., and H. Clugston.
1955.
Effects of various
levels cf x-irradiation on the gametes and early
embroys of Fundulus heteroclitus.
Biol. Bull.
108(3)}: 318-325.
hs
Ts on tiv
Nor A