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indicated above, then compared. There were four to seven measurements per experi- ment depending on the measurement periodicity. One-factor ANOVA P , 0.05 with
the LSD test was applied to compare the data, i.e. mean sizes and weights, various indices and the percentages of organic matter per components, once homogeneity of
variances had been tested. All analyses were performed with the statistical software
STATGRAPHICS
.
3. Results
3.1. Growth The comparison of sea urchin growth between the two reproductive periods showed
that sea urchin response to variation in food supply depended on their sexual state. As no significant differences in the initial starting weight and diameter were found between
Fig. 3. Changes in mean test diameter and wet weight 6S.D. for starved x and fed ♦ urchins during the maturity period.
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replicates of the same treatments and because the growth pattern of these replicates was similar, Figs. 3 and 4 illustrates pooled replicates.
3.1.1. Maturity period The test diameter and wet weight of Sphaerechinus granularis Fig. 3 did not change
significantly P . 0.05 in fed and starved urchins during the three years, except between February and April 1992 when a low but significant increase P , 0.05 in the test
diameter of fed urchins was observed but without any significant variation in wet weight.
3.1.2. Recovery period The response of fed urchins Fig. 4 differed greatly from that observed with the
starved ones. The test diameter and wet weight of starved individuals did not vary significantly P . 0.05 while in the fed urchins the final values for both test diameters
and wet weights were always significantly higher than the initial ones. The test diameter of fed urchins gradually increased by 4–6 mm and the wet weight by 24–43 g.
3.2. Indices Because there were no significant differences among replicates within treatments, the
data were presented as pooled replicates in Fig. 5. 3.2.1. Gonad indices GI
At the end of the two annual experiments, the mean gonad indices of fed urchins were significantly higher than those of starved ones over both the recovery and the maturity
Fig. 4. Changes in mean 6S.D. test diameter and wet weight for starved x and fed ♦ urchins during the recovery period.
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Fig. 5. Comparison of mean 6S.D. gonad GI, gut GtI and lantern indices LI at the end of the recovery 1991; 1992 and maturity periods 1992; 1993 in laboratory experiment starved, st, and fed urchins, fd and
in the natural environment before pr and after post the laboratory experiment 92 for the 1992 recovery period; 93 for the 1993 maturity period.
phases Fig. 5. The 1992 experiment showed that at the end of the recovery period i the starved urchins presented a GI significantly lower P , 0.05 than the preexperimen-
tal value termed ‘pr 92’ on Fig. 5, ii the GI of fed urchins were significantly higher than the value measured concomitantly in the population in the natural environment
termed ‘post 92’ on Fig. 5. At the end of the maturity period i the GI of starved urchins did not significantly differ from the preexperimental value, ii the GI of fed
urchins did not significantly differ from the value measured at the same time in the reference population in the natural environment post 92. At the end of the maturity
period, over the two gonadal cycles studied the GI of starved urchins were significantly higher P , 0.05 than at the end of the recovery period e.g.: st-mat92 . st-rec91 and
st-mat93 . st-rec92 where st represents the starved urchins, mat the maturity period and rec the recovery period. This increase could be interpreted as evidence of gameto-
genesis despite starvation.
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3.2.2. Gut indices GtI The analysis of gut index results did not display any obvious pattern. At the end of the
1991-recovery period and 1992-maturity period the gut index of fed urchins was significantly higher than that of the starved ones P , 0.05; these differences were not
significant in the two other experiments 1992-recovery period and 1993-maturity period. The 1992 and 1993 experiments did not reveal differences P . 0.05 between
the preexperimental value and GtI the of starved and fed urchins except for the starved urchins of the 1993-maturity period that had significantly higher GtI. At the end of the
1992-recovery period, the GtI of the population in the natural environment was significantly higher P , 0.05 than that of the laboratory starved and fed urchins.
3.2.3. Lantern indices LI No difference in the lantern indices was observed between the treatments P . 0.05
except at the end of the 1992-recovery period when the lantern indices of fed urchins were significantly lower than those of the starved ones and than the preexperimental
value. At this time the LI of the population in the natural environment was significantly the lowest.
3.3. Level in organic matter As there were no significant differences between replicates within treatments, Fig. 6
illustrates pooled fed f and starved st groups. 3.3.1. Test
At the end of the two annual experiments, the levels of organic matter OM in the test of fed urchins were significantly higher P , 0.05 than those of starved ones over
both the recovery and the maturity phases. At the end of the 1992-recovery period, the pre-experimental pr92 OM level was significantly higher than OM level in the starved
urchins, but did not differ from that of the fed urchins. At the end of the 1993-maturity period no significant difference P . 0.05 was observed between the fed and starved
urchins. However the OM level of fed urchins was significant higher than the pre- experimental value pr93.
3.3.2. Gonads and gut At the end of the recovery period the OM pattern in these two organs was the same as
in the test with OM levels significantly lower P , 0.05 in the starved urchins than in the fed ones and than the 1992-pre-experimental value. Contrary to the test, OM levels
did not significantly differ in fed and starved urchins at the end of the maturity period P . 0.05. The only difference between gonads and gut was that OM levels in the gut of
starved and fed urchins were higher P , 0.05 than the preexperimental value while they did not significantly differ in the gonads P . 0.05.
3.3.3. Lantern and peristomial membranes At the end of the 1992-recovery period, the OM level in fed urchins was significantly
higher than the one in starved urchins although this was not the case in 1991. The 1992
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Fig. 6. Comparison of mean 6S.D. organic matter level in the different organs test, gonads, gut, lantern and peristomial membranes at the start of the laboratory experiment pr 92 for the 1992 recovery period; 93
data for the 1993 maturity period and at the end of the laboratory experiment starved, st, and fed urchins, f.
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OM levels in fed and starved urchins were significantly lower than the pre-experimental value P , 0.05. At the end of the 1993-maturity period, no significant difference
P . 0.05 was observed between the OM levels preexperimental, fed and starved urchins.
To summarise i at the end of the recovery period, the OM levels in test, gonads and gut of fed urchins were always significantly higher than those of the starved groups, as
were the OM values in lantern and in peristomial membranes over 1992 treatments. The pre-experimental value was significantly higher than all the OM levels recorded in 1992
starved urchins. It did not differ from the OM levels of fed urchins except in lantern and peristomial membranes where the OM was significantly reduced ii at the end of the
maturity period, no significant differences were observed in the gonads, guts and peristomial membranes between starved and fed urchins. The OM levels in the test,
gonads and lantern of starved urchins did not differ from the pre-experimental values, whereas they were increased in the test and gut of fed urchins. Consequently, throughout
the recovery period the starved urchins were obviously losing organic matter from the test body wall and gonads. On the other hand, the fed urchins stored organic matter in
their body wall over the maturity period.
4. Discussion
