J. Moll Stud. (1998), 64,173-181
© The Malacological Society of London 1998
BIOCHEMICAL COMPOSITION OF HELIX SNAILS:
INFLUENCE OF GENETIC AND PHYSIOLOGICAL FACTORS
ANNETTE GOMOT
Laboratoire de Biologie des Organismes et Ecosystimes, U.F.R. des Sciences et Techniques, place Marichal
Leclerc, 25030 Besancon Cedex, France
(Received 16 September 1996; accepted 24 May 1997)
to the species, there is no information on their
comparative chemical composition. Only the
This paper describes the biochemical composition of
nutritive value of farmed Helix aspersa of
different species (Helix lucorum. Helix pomatia) and
relatively low bodyweight has been evaluated
sub-species of snails (Helix aspersa aspersa, Helix (Clayes & Demeyer, 1986).
aspersa maxima) reared in the same conditions with a
Many snail farms are being established at the
feed ('Helixal') specially designed for edible snails.
present time, in part to compensate for the
In addition, the composition of wild H. pomatia and
decrease in natural populations in certain
H. lucorum is presented to allow comparison
countries and in part in order to produce goodbetween snails of different origins. Analyses determined the percentages of proteins, lipids and
quality snails for consumption. Thus it seemed
minerals. They reveal both similarities and differuseful to make a comparative study of differences in composition according to the species and the
ences in biochemical composition between the
part analysed (whole body, pedal mass, and visceral
most commonly eaten species. With that end in
mass). H. pomatia contains the highest percentage of view, analyses of snails of clearly identified orimineral matter and the lowest percentage of lipids.
gin were made. In addition, these snails were
Surprisingly, protein contents are slightly different
subject to genetic studies in our laboratory
between artificially reared H. aspersa maxima of
3 months old and wild H. pomatia. The results make (Borgo, Souty-Grosset & Gomot, 1995; Borgo,
Souty-Grosset, Bouchon & Gomot, 1996)
it possible to evaluate nutritional quality of snails
with the composition of the body of four edible snail
which allowed an up-to-date and accurate
species.
identification. Some were collected from wild
populations (which are still the main source of
supply for human consumption), while others
were reared in a controlled environment that
INTRODUCTION
allowed us to study the effect of different
factors
(species, age and environmental paramWhile detailed analyses are available for many
foods (Alais & Linden, 1991), there are few eters) on the biochemical composition of their
data on the composition and nutritional value tissues.
of edible snails. The essential amino-acid
composition of the molluscan pest Achatina
fulica Bowdich was determined by Mead &
MATERIALS AND METHODS
Kemmerer (1953) to determine the possibility
of using snail meat as a source of animal
The animals
protein in feed for poultry and livestock.
The study was conducted on four species or subFor Helix pomatia L. and Helix aspersa species of the genus Helix: Helix aspersa aspersa,
Muller, the information available up to 1975 on Helix aspersa maxima Taylor, Helix pomatia and
their composition of proteins, lipids, carbo- Helix lucorum L. The majority of the analyses were
hydrates and minerals was summarized by of animals reared in off-the-ground cages specially
Cadart (1975), who remarked on their richness designed for snail rearing and in optimal environin mineral salts. Since that date some informa- mental conditions for growth (photoperiod 18L : 6D;
20°C; relative humidity 90%) (Gomot &
tion has appeared on species that are not temperature
Deray, 1987). The H. a. aspersa came from a strain
always well defined, following various treat- from the Cavaillon region of France. The H. aspersa
ments of the flesh (Table 1). Thus, in spite of maxima, originally imported from Algeria, had been
the fact that there is a significant international raised in France for 30 generations. The H. pomatia
trade in snails and prices vary greatly according parent snails were collected in the Choye forest (70ABSTRACT
174
A. GOMOT
Table 1. Data available in the literature on the biochemical composition of snails for the same or
related species.
Species
Water
(%)
gper 100 g fresh matter
Proteins Lipids Carbohydrates
Whole Raw Snail
Helix pomatia
Authors
Ash
0.79
Oudejans & Van
der Host, 1974
Raw Snail
species not defined
79.2
16.1
1.4
2
1.3
Watt & Merril,
1975
Raw Giant African Snail
Achatina
89.2
9.9
1.4
4.4
2.1
Watt & Merril,
1975
H. pomatia
Raw Foot
72.8 to
80.7
H. pomatia
Edible Part
79
16
1
H. pomatia
Whole Snail
84.9
12.3
0.7
83.3
87.6
12
9.9
0.7
0.5
H. pomatia
84.9
12.6
H. aspersa
Reared Snail
81.6
Raw Snail
Oreohelix- strigosa
Whole Snail
H. aspersa
Whole Raw Snail
—small snails (2.5 g)
—large snails (3.5 g)
Wieser & Schuster,
1975
1
Souci etal., 1981
1.9
Avagnina, 1983
2.7
1.2
Claeys & Demeyer,
1986
0.5
1.8
Fontanillas, 1989
16.3
0.8
1.3
Bonnet etal., 1990
79
16
1
2
1
Feinberg etal., 1991
78 to
81
10.4
1.5
4.6
France) and the H. lucorum came from a population
established at Caluire in the Lyon area (69-France).
The rearing method was as follows: Following mating
of the parents, the eggs laid were collected and the
young that hatched were reared in cages above
ground on a meal (E3-2) prepared specially for snails
(Trademark Helixal: Ets Lupine Alivor - 39 Clairvaux les Lacs - France). The analyses of the snail
food was: proteins 13.4%, crude fat 4.3%, cellulose
2.5%, ash 31.4%, calcium 10.8%, vitamins A, D3, E
respectively 15 000, 2 000 IU.kg"1 and 20 mg.kg"1.
Sample preparation
This was performed on a series of artificially reared
animals from 3 to 5 months of age and also on adults
of the species H. pomatia and H. lucorum collected
from wild populations in order to determine whether
there are differences in these species that are a
function of their origin and age.
The snails for analysis were starved for 24 hours,
then decapitated and separated from their shell. The
whole body or its different parts were put into plastic
beakers kept in ice. Analyses were performed both
on the whole body and on the two principal parts: the
pedal mass, with the head and mantle edge; and the
visceral mass, containing the digestive gland, gonad,
2
0.5
0.4
Rees & Hand, 1993
albumen gland, genital ducts, kidney and heart. The
mucus and hemolymph leaking during separation of
the two parts was combined with the foot. The
number of animals sampled per lot was chosen to
give 130-200 g of organs before dehydration, the
quantity necessary to perform the various analyses
on the same pool of snails.
The soft tissues were rapidly frozen at -70°C and
stored at that temperature. They were then freezedried to constant weight to determine the moisture
content. The freeze-dried tissues were then ground in
a knife mill (Janke & Kundel A10) and reduced to
powder by passing through a sieve with holes 0.25
mm in diameter. The shells were dried at 60°C to
constant weight and the percentage shell to total
liveweight of the animal was calculated. The crude
ash content of the samples was determined by calcination of 2 g of powder in a muffle furnace (Pyrecton
KY type KY 2C4 Prolabo) at 550 ± 5°C for 6-7
hours.
Analysis of the organic matter
Protein content was determined by the colorimetric
method of Lowry, Rosebrough, Farr & Randall
(1951). Total lipids were determined by extraction
with a 2:1 V/V chloroform:methanol mixture and
BIOCHEMICAL COMPOSITION OF HELIX
titrated according to Folch, Lees & Stanley (1957).
Total monosaccharides were determined at Biological Chemistry Laboratory of Lille University (Dr
Michalsky and F. Delplace) by gas chromatography
after methanolysis and trimethylsilylation following
Kemerling, Gerwig, Vligenthart & Clamp (1975).
175
stituents of the tissue, the latter are expressed
as percentage dry matter. They are also given
as a ratio to fresh weight to provide a comparison with the flesh of other animals.
The ash content was highest in the wild H.
pomatia and H. lucorum. Among the artificially
reared snails, H. pomatia had the highest ash
Determination of minerals (Ca, Mg, P) and trace
content (11.7% at 3 months and 12.6% at 5
elements (Cu, Fe, Zn)
months). The other three species are similar in
Following ashing of the samples, Ca, Mg, Fe, Cu
their ash content (8.7 to 9.4%). With H. pomaand Zn were determined by atomic absorption
tia the influence of age can be seen on the ash
spectrometer (Perkin-Elmer 1100). Phosphorus was
content, dry matter and proportion of the shell
determined using a Technicon autoanalyser with
to liveweight as the animal goes from 3 to 5
nitro-vanado-molybdic reagent.
months of age with the same feed (Table 2).
Initially, determinations were made on 5 snails
The percentage of protein, like that of moisanalysed individually to calculate the standard deviature, differs little between artificially reared H.
tion and on pools of from 5 to 10 snails. The results
aspersa maxima and wild H. pomatia; these are
being very close, the figures in the tables are the
values obtained from analyses of pools of animals,
the lowest percentages (55 to 59.3%). Artifiwhich are mean values.
cially reared H. pomatia has a higher percentage protein, close to that of artificially reared
H. a. aspersa and H. lucorum (65.2 to 68.2% at
3 months and 72.5% for H. pomatia at 5
RESULTS
months). For H. lucorum one notes a difference between the two lots collected from wild
Composition of the body offour species of
populations, the cause of which might be a
Helix snails
difference in the development of the reproducThe composition of the whole body was tive apparatus—larger or smaller albumen
studied on artificially reared snails of the same gland according to whether the snails were
age (3 months) of each of the 4 species (Table collected before or after egg-laying.
2). Determinations were also made on H.
The percentage of lipids is lowest in wild H.
pomatia at 4 months and 5 months, since this lucorum and H. pomatia, with differences of
species, like H. lucorum, grows more slowly 1.9% and 3.1% between the two lots analysed
than H. a. aspersa or H. aspersa maxima. This for these species. The percentage lipids in the
permitted identification of changes in composi- artificially reared snails of all the species is
tion with age.
higher than in the wild ones, in spite of the fact
The weight of the shell as a percentage of the that the latter are older. Of the 4 species, H.
total liveweight was between 10.3% and 11.5% pomatia contains the least lipids and one also
notes a decrease between the ages of 3 and 5
for snails of the same age of the 4 species fed
on the same feed E3-2 (Table 2). The shell as a months.
percentage of liveweight is much higher in the
The percentage of total sugars is commonly
snails (H. pomatia and H. lucorum) collected obtained as a difference between 100% and
from wild populations (17.5% and 22%), the sum of protein + lipids + ash. With this
largely due to the animals being older (over 2 calculation one obtains 23.7% of total sugars
years of age) but also to other factors like the for H. aspersa maxima. In contrast, an accurate
nature of the soil and vegetation, as well as the determination of sugars by gas chromatoginfluence of the seasons (interrupted growth, raphy gives 13.8% for this species (Table 2),
hibernation, etc.).
which shows that the calculation by difference
is unsatisfactory.
The moisture content of snails varies with
the temperature and humidity of their environment. However, in the identical conditions in
which sampling was performed, artificially Comparison of the biochemical composition of
reared H. aspersa maxima has a moisture the foot and viscera in the four species
content very close to that of wild H. pomatia, Snails are prepared for human consumption in
whereas H. a. aspersa has a slightly lower different ways, depending on the species and
moisture content, close to that of H. lucorum. the region. Petits Gris (//. a. aspersa) are
To prevent differences in moisture content generally eaten whole. With the larger species
affecting the percentages of the different con- (H. pomatia, H. lucorum and H. aspersa
E3-2
[Natural
mid July]
E3-2
3
?
3
5
?
H. lucorum
#
5.6
8.9
24.2
26.9
24
17
6
6
10.3
12.7
22.2
18.1
10.8
17.5
19
11.2
16
Mean
4.8
15.9
19.6
11.5
10.9
36
8
6
11.2
9.1
Shell
16.3
15.7
Mean
weight
<g>
8
10
16
Number
of
animals
15.8
17.7
14.6
13.1
16
17.5
17.8
84.2
82.3
85.3
86.8
14.1
84
82.4
82.1
15.6
12.5
16.2
1.8
2.2
1.8
1.4
2.3
1.2
1.3
1.1
1.5
10.8
11.9
10.7
10.7
12.8
8.6
7.3
11.7
12.6
12.6
8.1
9.1
7.2
10.5
68.1
72.5
59.3
55
67.8
68.2
60
58
58.5
57.6
65.2
Proteins
(Lowry)
/FM
/DM
1.1
0.9
0.7
0.4
1.5
1.1
0.6
1.5
1.8
1.2
1.6
/FM
7
5.5
5
3.1
9.7
6.5
3.4
10.8
12
9.7
10
/DM
Lipids
Results : g per 100 g
9.2
13.4
8.8
8.7
9
9.4
#•
Ash
Dry
matter /FM
/DM
85.8
84.3
87.4
83.7
**
Water
*: % in weight of healthy snails; **: % in weight of deshelled snails.; FM: Fresh matter.; DM: Dry matter.
[Natural
end June]
E3-2
3
H. pomatia
E3-2
Snail
feeds
H.aspersa
maxima
Age
(months)
H.a.aspersa 3
Species
Table 2. Analyses of the whole body of four snail species.
1.7
13.8
Carbohydrates
/FM /DM
o
g
>
^
CO
in
o
i~
cb "^
r~
CO
co CM
o
a> en
O CM
o
CO
CM CO
CM x t
in
in
CO CO
en in
cn CO
CM
r^ m
in CM
CO in
r-
00 P^
CM
in
«-
CM
CO 00
«- • -
CO
CO
*~
00
« - CM
in
in
« - CM
13.
24.
13.
in
CM
CO
CM
-I
i
a?
>S CM
CD
CM
CM
CD
•
—
•
^
A
Age
J5
—
CO
XI
CD
a
XI \j
c rg>
a?
CD
c
x.
CD
CD
CD
^
X
CD
CO
c
CO
CO
r^
CD
CO
tr
?
in
r-
E
r-
weigl
10.
15.
CO
healtl
«
in
co c
»*-
c
CO
CM
'
•
•
a? xT
CO GJ
CO
'cfl
-C
CD
0
~3
CD
CD
C
CD
c
a>
ails;
i n CM
in
SIS
86.
75.
a?
00
Fool
Vise
en
E
Z "o 'c
0)
i—
CD
E
3
o
o
—•
CM
3
c
o
E
£
a
CO
m
8
(/)
CO
1
CO CO
E
• —
omatia
X o
jcorum
lysi
CO
CD
a? c
(ima
o
0
rsus
en
CO
CD
s
o oo
.C
«^
o
al we
•<»•
co
13
a
o
T3
in
in
Is; ND: r t deti
and
CD
aspera
In the foot (the edible part) the most abundant
element is Ca. The percentage of dry matter
is: Ca (1.4-^.6) > P (0.4-1) > Mg (0.3-0.5).
Comparing the species with each other, for Ca,
CD
cies
Macro-elements: Ca, Mg, P
CD
CD
a
Ie3 Comparati'
H. pomatia has the highest concentration of ash
(Table 2) and in general the ash concentration
is higher in the foot than in the viscera, with the
exception of H. aspersa maxima for which the
two tissues are similar in concentration. Analysis of minerals reveals which elements are
responsible for the differences (Table 4).
c
in
t—
'I
o
CD
z
cb CO
CD
i-
Analysis of the mineral matter of the foot and
viscera of snails fed with the same feed (E3-2)
o
ell-
CM
Fool
Vise
Fool
Vise
Part
four
eli spec ies resired o
•<t
i n xt
"~ * ~
86.
73.
Ash
9 die
eins
LL^
CM CM
B.4%
•rn
177
Fool
Vise
BIOCHEMICAL COMPOSITION OF HELIX
maxima) the visceral hump is removed, since it
has a bitter taste, and only the fleshy part—
6
.o
foot, head and mantle edge—is eaten. To take
CD
Q
account of these differences in culinary
u (A<D
Z
It
practice, the foot and viscera of snails fed with
(0
the same food were always analysed separately.
^^
m in
CO CM
Table 3 reveals common features but also some
Q
CO
specific differences.
XI
The common features include: a relatively
00 CO
'a
LJ
o co
constant foot/viscera fresh-weight ratio of 72.8
± 1.2% for the foot, 27.1 ± 1.2% for the
co r^
viscera; the dry matter of the viscera exceeds
in co
CO CO
that of the foot, with different ratios according
1
to the species (x 1.9 on average): 1.64:1 (H.
CO
« - CO
lucorum); 1.82:1 (//. pomatia); 1.96:1 (H. aspersa
0 0 OO
o
o |
maxima); 2.36:1 (H. a. aspersa); the lipids are
CL
o>
always at a higher concentration in the viscera
than in the foot (x 1.8 on average), but as for
oo «CM
d en
the dry matter the ratio varies with the species:
CO
"~
LU
1.2:1 (H. pomatia); 1.8-1.9:1 (H. lucorum, H. a.
aspersa); 2.5:1 (H. aspersa maxima).
CO CO
t - CM
tt
The differences include: the protein propor£
tion, which varies with the species and part of
CD
the body. The percentage of proteins is similar
CO
CD
e
CD
.
C
CM en
in the foot and viscera of H. a. aspersa and H.
Q
« - CM
lucorum, the latter being richer in proteins than
c
H. a. aspersa in both parts. In H. pomatia the
a>
in co
visceral mass contains a higher protein level
03
*
that the foot, while for H. aspersa maxima the
*
reverse is true. In addition, the percentage ash
is similar in the viscera and foot of H. aspersa
maxima, while in the other 3 species, mineral
r- CM
matter is more abundant in the foot than in the
co ~T
viscera.
„ o
x>
Overall, for both parts of the body, one notes
O -O
that the dry matter of artificially reared H.
»*pomatia and H. lucorum is richer in proteins
o
cq
than that of H. a. aspersa and H. aspersa
maxima, while the opposite is true for lipids.
*
V)
a
3
CO
CD
CC
Q.
X.
CD
LL
178
A. GOMOT
00
f)
T -
CO
oro
LU
r - US
I
CD
E
8
c
o
•o
^ * f"s
CO CO
CO
O
t -
fry
/In
oo «-
mm
•- o
ro
co
CO
*f
I -
« - If)
CM
«-
CNQ
* * CO
co ^
00 CO
CM co
o •
CM
I-
CM
CO
m co
//. pomatia > H lucorum > H. a. aspersa > H.
aspersa maxima. The concentration of Ca in H.
pomatia is respectively 2.4, 2.8 and 3.2 times
that in H. lucorum, H. a. aspersa and H. aspersa
maxima.
In the case of Mg, the situation is almost the
reverse of that of Ca: H. aspersa maxima has
the highest concentration and H. pomatia the
lowest (H. aspersa maxima > H. lucorum > H.
a. aspersa > H. pomatia).
tf
Q
O
«- r-
•- CM t i ~ Q O
C0«-
CM>-
C0>- ^ i -
•*O
0OCM
CMCM
<-O>
co
Q O 'tCM
COCM • * < r
co
For P, the differences are less marked than
for Ca, since the concentration in H. pomatia is
respectively 1.6, 1.7 and 2.3 times that in H.
aspersa maxima., H. a. aspersa and H. lucorum
(H. pomatia > H. aspersa maxima 3= H. a.
aspersa > H. lucorum).
In the viscera, concentrations of Ca and P
(% dry matter) are relatively close: P (1.3-1.9)
-» Ca (1.1-1.3) > Mg (0.3-0.7). The differences
between the species in Ca and P concentrations
of the viscera are much less marked than for
the foot.
Measurement of the three minerals (Ca, Mg,
P) in the foot and viscera shows that the higher
concentration of ash in H. pomatia (Table 2) is
due to higher concentration of Ca and P in the
foot of this species.
ID
I
o
.5
'o
CM
o t
>t CM a>o a i o
•- <o r- o
co «- r-~
CO
<D
Q.
LD 1O
CMCM
.8
to
L/)
i^-
n
LD
1AO
co
coin
O^t
c
CO
CD
8
CMCO
COCM
QCO
inoo
i—oo
coo) inco
Trace elements: Cu, Fe, Zn
T3
C
CO
o
1
2
o o o o oi
in oo S co 3 i
o8
o
o
s
CD
E
c
8
o o
CM CM
.5
<p
o
"5
-a
c
o o go
o> r> ^ ^
co «-
co co
§ 0CM0
co in
. • _3
CM CO
i -
CO
CM CM
^^
_
Q)
CO CO
oo o
Q
8°
in co
co oo
« - CM
CO CO
CO
CD
c
E
CD
(D s - O
0- O .Q
CD
§|
j _ ,
IS
H
CD
§ 8 8.8 §1
c
s
C
CD O
In the foot (to which the haemolymph was
added), Cu is the most important of these metals: Cu (0.1-0.3%o) > Fe (0.06-0.17oo) - Zn
(0.06-0.08%o). If one compares the concentrations in the 4 species:
For Cu: H. pomatia > H. a. aspersa <« H.
lucorum > H. aspersa maxima
For Fe: H. pomatia > H. aspersa maxima >
H. lucorum ~ H. a. aspersa
For Zn: the interspecific variation is much
less marked.
In the viscera, Zn is the major metal:
Zn (1.4-2.4%o) > Fe (0.2-0.7%o) > Cu (0.040.06%o). The order of the species by concentration in the viscera is different for each metal:
For Zn: H. pomatia > H. a. aspersa ~ H.
lucorum ~ H. aspersa maxima
For Fe: H. lucorum > H. pomatia -> H.
aspersa maxima > H. a. aspersa
For Cu: H. a. aspersa •*• H. lucorum > H.
aspersa maxima «• H. pomatia
Q.
E
o
DISCUSSION
u
a
CD
O
CD
Q.
w
i It
Q
CO
<n "c
E i
CO
!
II
The comparative analysis of the biochemical
composition of raw snails presented here is the
first complete study on these animals. It reveals
BIOCHEMICAL COMPOSITION OF HELIX
both similarities and differences between
species.
Until now only fragmentary data have been
available, sometimes without clear identification of the species (Table 1). In addition,
heterogeneous sampling methods and analysis
of animals of differing origins have led to major
differences in reported protein content for the
same species (from 9.9% to 16.3% for H.
aspersa). All this provides justification for the
present analysis of different species reared in
the same conditions.
The results are much more homogeneous for
each species (Tables 2, 3, 4) and clearly show
the role of genetic and physiological factors on
the composition of the snail. Account must be
taken of these factors in interpretation of
biochemical analyses and in the development
of a snail food that promotes the nutritional
qualities of their meat. The principal genetic
and physiological characteristics of the four
species of snail studied are summarized and
discussed below.
The genetic factor that should be most
emphasised is growth rate. This allows us to
distinguish two groups of species: H. a. aspersa
and H. aspersa maxima with a rapid growth
rate and adult weight attained at the age of 3
months in favourable environmental conditions; and H. pomatia and H. lucorum with a
slower growth rate and more than 5 months
required to attain adult weight.
Among the most significant differences, we
can underline that when fed on the same feed
(E3-2) H. pomatia and H. lucorum were the
richest in protein (•» 68% of dry matter)
followed by H. a. aspersa (65%) and H. aspersa
maxima (58%) (Table 2) whereas for lipids, H.
pomatia contains the least. Lastly, H. pomatia
has the highest content of Ca, P, Cu and Fe
(Table 4). In fact, this species often presents
the clearest differences.
Among the physiological factors, age and
environmental factors are those that appear
most clearly. This can be seen in the relative
weight of the shell in H. pomatia, which rises
from 10.3% of liveweight at 3 months to 12.7%
at 5 months and 24.2% in the adults collected
from wild populations at an age of from 3 to 5
or 6 years.
On the other hand, the lipid content of H.
pomatia decreases with age and the same
phenomenon has been observed with H. a.
aspersa and H. aspersa maxima. This finding is
new and specific to snails, since in other farmed
animals ageing is accompanied by an increase
in percentage of lipids (Beitz, 1985).
179
The influence of environmental factors
requires further study, especially of snails
collected from wild populations in different
biotopes, to analyse the influence of the vegetation consumed and the nature of the soil, since
we have previously shown that this last plays a
very important role on the growth of H. a.
aspersa (Gomot, Gomot, Boukraa & Bruckert,
1989). In previous studies we have also determined the optimum conditions of photoperiod,
temperature and stocking which induce the
endocrine factors necessary for fast and balanced development of edible snails (Gomot &
Deray, 1987; Gomot & Gomot, 1995). The
results presented in this paper illustrate the
way in which genetic differences—revealed by
electrophoresis of the muscle proteins of the
foot, to distinguish between the meat of H.
pomatia and Achatina fulica (Bracchi, 1988) or
by study of mitochondrial DNA (Borgo et al.,
1995)—translate into differences in the proportions of the essential biochemical constituents
of the tissues of these species.
In order to position the snail relative to other
foodstuffs, we report (Table 5) the average
composition of various, types of meat and fish
(from Kayser, 1963) compared with our analyses of the flesh of H. aspersa maxima ready for
consumption (the majority of the digestive
gland being removed and the remaining flesh
boiled in a court-bouillon). The snail is an
advantageous foodstuff from a dietary point of
view in that it is a source of proteins while
remaining low in calories, its energy value
(calculated from the conversion coefficients
proposed by Dupin, Cuq, Malewiak, LeynaudRouaud & Berthier, 1992) being lower than
that of the leanest meat or fish.
In conclusion, the value of the complete snail
rearing system developed in our laboratory for
rational study of the influence of factors affecting development and biochemical composition
must be emphasised. Control of the various
parameters makes it possible on the one hand
to influence the quality of the animals reared
for human consumption without the possible
effects of pollutants which may occur in the
field such as bioaccumulation of heavy metals
(Martin & Coughtrey, 1982; Dallinger &
Wieser, 1984; Campani, Bracchi, Guizzardi,
Madarena & Del Bono, 1992).
ACKNOWLEDGEMENTS
This work has been performed in the framework of a
CIFRE convention (n° 607-90) of the Association
A. GOMOT
180
CO CO
CN CM CO
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o
Nationale de la Recherche Technique between the
Zoology-Embryology Laboratory of the University
of Franche-Comte' and the Institut de Recherches
et d'Innovation Scientifiques of Paris. We have
benefited from the collaboration of specialists, whom
we warmly thank, for analysis of sugars (Dr J.C.
Michalsky and F. Delplace: Biological Chemistry
Laboratory, Lille University), for the analysis of
proteins and minerals (M. Regnier, UCAAB,
Chateau-Thierry) and metals (Prof. J.C. Pihan,
Ecotoxicology Laboratory of the University of
Metz).
We thank Pr L. Gomot and Pr C.R. Marchand for
many fruitful discussions during the course of these
studies. We are also very grateful to Brigitte Jolibois
for the preparation of the manuscript and very
much indebted to Dr LJ. Elmslie for his help with its
translation.
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