waders and their estuarine food supplies - Vlaams Instituut voor de ...

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time (d)
Fig. 2. The weight ol the siphon (mean ± St) ol animals 137-38
mini which were removed Irom ihe substratum I to 5 days after being
buried: number of bivalves indicated: dark area, weigh! ol the remaining
siphon: grey area, weight ol the removed siphon; time has
no effect on the weight of Ihe remaining siphon (R J = 3.2%; p =
0.73; n = 66) nor on the weight of the total siphon i remaining + retnoved
amount) (R- = 8.7%; p = 0.23; n = 66); basic procedure elucidated
in the accompanying sketches
Fig. 3. The depth of 13 animal- as
measured with a thread in the course
of 5 days after burial on Day 0: leti
panel shows the depth of three bivalves
whose siphon was left intact;
the siphon weight I in mg) on Ihe last
day is indicated: the two other panel-
-how the depth of 6 animals liom
which I to 6 mg was removed and
lour animals which lost 9 to 14 mg:
for each individual figures indicate
amputated mg + remaining mg in
that order.
DEPTH AND SIPHON CROPPING IN SCROBICULARIA
ing waler. The llesh was dried at 70 "C and burned al
550 B C.
SPSS (Nie et al. 1975) was used for all statistical
analyses.
Results
Amputation of the siphon
The siphon weight, as determined I to 5 days after the
amputation, decreased more when a greater amount
had been removed, but not as much as expected assuming
an equal siphon weight for all categories before
the amputation (Table I). Two explanations are
conceivable: there was regeneration of the siphon, or
the initial siphon weights were in fact different.
Regeneration as rapid as this seems an unlikely explanation.
Hodgson (1982a) found that Scrobicularia
are able to regenerate their siphon at a rate of 3% per
day and that regrowth starts after a lag of 24 h during
which the wound heals. Assuming equal siphon
weight before amputation, animals losing > 10 mg
would have regenerated c. 6 mg during a grow ing period
of 4 days, i.e. a daily average of 21%. That would
be extremely high compared with the rate of 3' i measured
in several bivalves (Trevallion 1971. Hodgson
1982a). In fact there was no increase in mean siphon
weight during the experiment (Fig. 2).
li is much more likely that the experimental cropping
was in fact not random. The siphon weight was
CONTROL amputation= 1-6mg amputation= 9-14mg
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time (d)