Open Journal of Genetics, 2013, 3, 224-233 OJGen
http://dx.doi.org/10.4236/ojgen.2013.33025 Published Online September 2013 (http://www.scirp.org/journal/ojgen/)
First steps on technological and genetic improvement of
European abalone (Haliotis tuberculata) based on
investigations in full-sib families
Valérie Roussel1, Julien Charreyron1, Sylvain Labarr e 2, Alain Van Wormhoudt1, Sylvain Huchette2
1MNHN, UMR 7208 BOREA, Station de Biologie Marine, Concarneau, France
2France Haliotis, Plouguerneau, France
Email: vroussel@mnhn.fr
Received 24 July 2013; revised 20 August 2013; accepted 28 August 2013
Copyright © 2013 Valérie Roussel et al. This is an open access article distributed under the Creative Commons Attribution License,
which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
ABSTRACT
The European abalone Haliotis tuberculata is of eco-
nomical importance in Europe, and recently in
France where most of the consumed abalones re-
mained wild animals fished on the coast. Recently, the
creation of hatcheries allowed the production of cul-
tured animals, and aquaculture is in progress. To
optimize selective breeding programs, different stud-
ies were performed on adults and on their progenies.
First, ten adult families, assumed to be bi-parental
and produced in 2007 were analyzed. As these fami-
lies were developed at the beginning of the hatchery
production, the parentage of the individual necessi-
tated to be tested. The progenies parentage assign-
ment was done by using eight microsatellite DNA loci.
In fine, the heritability was estimated from the analy-
sis of variance of seven full-sib families which include
from 23 to 27 progenies. Heritability estimate was the
higher for length, width and weight (0.37, 0.29 and
0.40 respectively). A high correlation was also shown
between these heritable traits which can be useful
during animal breeding. Shell color traits were also
analyzed, using image treatment procedure. Two
traits were selected according to the global color of
the shell: red color and hue. The distributio n of these
traits evidenced a polygenic genetic control of shell
color and measure of heritability evidenced a high to
medium value for red color (Cr) and Hue (H) (0.33
and 0.20 respectively). No correlation was shown be-
tween growth and this parameter. In a second time,
juveniles families produced in 2010 were studied from
parents issued of the first selection. A correlation be-
tween size and density at juvenile stage was estab-
lished but a statistical analysis demonstrated, by us-
ing density as co-variable a significant effect of family
on size. In these conditions, growth is highly heritable
(0.74). This study is a first step toward the use of ge-
netic ma rkers fo r select ion, but a lso a step toward the
breeding improvement of European abalone.
Keywords: European Abalone; Microsatellite;
Heritability; Morphological Traits; Shell Color Traits;
Juvenile
1. INTRODUCTION
Abalones are marine gastropods living worldwide in
temperate or tropical waters [1] and appreciated for its
comestible foot. Because of their great economical im-
portance, the first cultures of Asian abalone began in the
1950’s [2]. Researches on hatchery methods started in
Japan in the 1960’s and later in California and Taiwan in
the 1960’s, Korea, France and Ireland in the 1970’s, New
Zealand and Australia in the 1980’s [3] and South Africa
in the 1990’s [4]. Two ways can be considered for the
improvement of abalone aquaculture, including techno-
logical and genetic approaches [5,6]. The first one com-
prises the hatchery conditions (temperature, food for
larvae or adult, cages size and management) and the
second would be based on Markers Assisted Selection
(MAS). The technical improvement of hatchery condi-
tions started in the 90’s for tropical abalone, with a first
step related to fertilization and larval care, and a second
step related to the survival and growth of post-settlement
larvae [2]. These investigations are occuring for other
genus of abalones [7,8], but no studies were devoted to
European abalones. Concerning the second way of im-
provement, the genetic way, the first studies started in
the 2000’s for indo-pacific abalones [9,10], and the most
advanced investigations are done on the Pacific abalone
(Haliotis discus hannai) and the blacklip abalone (Haliotis
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V. Roussel et al. / Open Journal of Genetics 3 (2013) 224-233 225
rubra) for which genetic linkage maps are already avail-
able [11-14]. In Europe, abalone farming still remains
new. Since the 1980’s, land based recirculation grow-out
techniques were imported and adapted from South Africa
or New Zealand to start an industry in Ire- land [15], but
with little success so far. In the 2000’s, land based and
sea based grow-out systems were developed in Western
France yielding better results.
A study concerning the optimization of MAS pro-
grams evidenced the high interest of such techniques to
improve genetic gain and cost benefits for Australian
abalone [16]. But to date, no programs of MAS were
developed on temperate abalones. The distribution of
European Abalone Haliotis tuberculata spreads in a large
temperate region, from the Morocco Atlantic coast to the
English Channel and the Mediterranean sea [17,18]. The
chromosome number of European abalone is 2n = 28,
whereas the Indo-Pacific and North-Pacific species have
a higher chromosome number with 2n = 32 or 36 [19].
These characteristics corroborate the important differ-
ence between European and tropical abalones and
strengthen the need of specific technical and genetic im-
provement methods targeted to this species. In western
France (Plouguerneau), hatchery techniques for H. tu-
berculata were adapted from [20]. Nowadays, this spe-
cies is at the first levels of domestication with three gen-
erations of mass selection, with a choice of individuals
based on morphological traits, and particularly growth
rate. Genetic improvement can be efficient with mass
selection in early phases of selection [21], but MAS
would be more efficient in later stages, or for other traits,
as it is now clearly established on several cattle or plant
species.
The aim of the present investigation was to study pa-
rameters linked to the early stages of abalone develop-
ment, and to estimate heritability of quantitative traits in
this species, which are the first steps of a MAS pro-
grams.
2. MATERIAL AND METHODS
2.1. Families Production and Growing
Conditions
2.1.1. Adult Families
Adult families were produced in “France Haliotis” hat-
chery premises in Plouguerneau, and obtained from par-
ents collected from wild stocks in North Western French
Brittany (Plouguerneau and Roscoff). Each family was
produced from a parental pair and kept in separated
nursery tanks for the first year. Crossing experiments
were done in individuals baskets to ensure the avoidance
of contamination of sperm and egg, or mixing of larvae
or juveniles among families. Then the juveniles of the 10
selected families of approximately 20 mm of maximum
length were reared in small sea cages (Figure 1(a)) at
about 10 m below chart datum for 2 years prior to sam-
pling. Each family was reared in separate rearing units at
the same density. The sea cages were lifted and the aba-
lone fed every other week with fresh seaweed (mostly
Palmaria palmata).
2.1.2. Juvenile Families
Juvenile families (Table 1) were produced in 2010 in
“France Haliotis” in Plouguerneau, and obtained from
parents belonging to the company stock (Table 2). As
the objective of the work was to have QTL analyses, the
different crosses were done in order to optimize the ge-
netic variability and the phenotypic variability in the
progenies. In most cases, an individual belonging to a
family representative of big individuals was crossed with
an individual belonging to a family representative of
small or medium individuals. Moreover, individuals
were chosen according to the genetic differences evi-
denced with the 8 SSR markers developed by [22] with
the objective of crossing as genetically different indi-
viduals as possible. Twelve full-sib families were thus
obtained in May during the reproduction period, and
were issued from the 10 full-sib families previously as
Figure 1. Cages (a) and juvenile plates (b) used for rearing the
families. The plates are 60 cm × 60 cm.
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V. Roussel et al. / Open Journal of Genetics 3 (2013) 224-233
226
Table 1. Genitors selected for each of the 12 juvenile families,
and size of their shells length. A2 to A8 corresponds to genitors
presents in the company stock, and wild parents correspond to
genitors coming from the Plouguerneau Coast in North Brit-
tany.
Juvenile Family Crossing Size (cm)
J1
J2
J3
J4
J5
J6
J7
J8
J9
J10
J11
J12
Wild × A6
A6 × A8
A3 × A4
A5 × A3
A3 × A8
A3 × Wild
A6 × A2
A1 × A2
A3 × A6
A3 × A2
A3 × A8
A6 × A2
6.2 × 6.7
5.9 × 6.3
6.8 × 5.9
5.8 × 6.7
5.8 × 6.7
6.4 × 6.7
6.4 × 6.6
6.1 × 6.2
6.3 × 6.1
5.6 × 6.6
5.8 × 6.0
6.8 × 6.6
previously described. Each of these juvenile families was
disposed in a separate tank. All tanks comprised six bas-
kets containing 20 plates each (Figure 1(b)), covered
with Ulvella lens [20]. The juveniles were feed with
Palmaria palmata, Ulva lactuca, and Saccharina sac-
charina.
2.2. Sampling, DNA Extraction and Genotyping
of Adult Families
Thirty individuals were randomly chosen from the 10
adult families. An epipodial clip was taken from each
individual and conserved in 70% ethanol for DNA ex-
traction. DNA was extracted with the CTAB method [23],
and was used to characterized COI mtDNA as previously
described [24], and to amplify eight microsatellite loci in
two quadriplex, as described in [22]. These loci are
highly polymorphic and some of them present null al-
leles. Amplified products were diluted in formamide
containing GENESCAN-350(ROX) (Applied Biosystem)
size standard, and size polymorphisms were screened
using an ABI Prism 3130 DNA sequencer (Applied Bio-
system). DNA fragments were analyzed using Gene-
mapper software version 4.0 (Applied biosystem).
2.3. Trait Evaluation for Adult Families
Direct measurements of length, width and weight were
performed on three years old animals.
Condition factor [25] was calculated using:

2.99
weight
CF 5575
length mm
g

To evidence the color characteristics of the shells, and
study the correlation between these characteristics and
genetic parameters, one photograph of the entire outer
shell of each abalone was taken using an Olympus
Camedia C400 in a room of “France Haliotis” hatchery.
Yelow color was chosen as background color after pre-
Table 2. Number of individuals studied for each step of the
work (N: number of individuals by sampled; n: number of indi-
viduals genotyped; np: number of individuals used for pheno-
typic traits, nc: number of individuals used for color traits).
Adult Family N n np n
c
A1
A2
A3
A4
A5
A6
A7
A8
A9
A10
30
30
30
30
30
30
30
30
30
30
0
27
25
23
0
26
25
24
27
0
0
27
25
23
0
26
25
24
27
0
0
26
22
20
0
19
24
19
17
0
liminary test. All the pictures were taken during daytime
from the morning to the evening, inducing a difference
of light intensity. This effect was eliminated by using
appropriate color spaces components which did not take
in account this phenomenon and allow to work on inde-
pendent traits like: Cb (blue) and Cr (red) from YCbCR
color space, and H (Hue) from HSV color space (the
value of red and blue is included between 0 and 255, and
hue value between 0 and 359). These pictures were
treated by using classical methods of image processing
(Figure 2). A binary image was obtained by using Otsu’s
threshold method [26], and then, the background was
separated from the area of interest to exclude the
non-animal part of the picture.
Next step of processing is cleaning of organisms at-
tached to the shell (tags, algae, or small shellfishes), us-
ing mathematical morphology tools, which could biased
the result of color analysis processing. These processes
produced a binary cleaned image of the abalone. In fine,
this image was superposed to red, blue and hue picture
permitting to exclude pixels of background and parasitic
element of shell. The result was the selection and value
of pixels of interest. The three averages of components
were calculated. For the images programming, all the
calculations were conduced with the software Octave
(http://www.gnu.org/software/o ctave/).
2.4. Trait Evaluation for Juvenile Families
During the last stage of biological development, the rela-
tionship between growth and density on the plates was
studied. For that, the density and size of individuals were
determined at 90 days after fecundation for the 12 fami-
lies. For each family, 120 individuals were evaluated on
6 different plates of 3600 cm², to estimate the variability
of the density. For each plate, individual size was meas-
ured on 20 individuals.
2.5. Data Analysis
For parentage assignment, a chi-square test was perfor-
Copyright © 2013 SciRes. OPEN ACCESS
V. Roussel et al. / Open Journal of Genetics 3 (2013) 224-233 227
Figure 2. Image treatment of the abalone pictures: (a) Initial
picture; (b) Threshold picture (with the background to 0); (c)
Red levels of the picture; (d) Final picture.
med to verify if the allelic frequencies observed in a
family were in accordance with those expected in theory.
Analysis of variance were carried out following the
standard procedure of a fixed model with only the family
effect for adult and with family and density effect for
juveniles. Densities were ranked into 8 classes from 20
to 548 animals per plate.
For adults: Yi = µ
+ Fi + ei
For juveniles: Yij = µ + Fi + Dj + Fi·Dj + eij
With µ = Grand mean, Fi = Family effect, Dj = Den-
sity effect, Fi·Dj = Density within Family nested effect,
and e = residual error.
For both groups (adults and juveniles) and trait,
full-sib heritability and its standard deviations was cal-
culated after analysis of variance according to Falconer
(1989) as described in [27]:

1212 2
AD
FS
ICE
p
VVV
V
hV
with
VA, VD, VI, VEC and VP: Additive, Dominant, Epistatic,
Error and total phenotypic variance respectively.
2
F
FS
P
V
hV
2
22
2F
FS
F
w
h
and


 
12
211 ?
211
FS
nt
hnn N






with:
hFS: Full Sub heritability for each trait
σ²F: variance between the progeny of different families
σ²w: variance between the individuals within a family
n: number of offspring per family ( for morpho-
logical traits and
24
19
for color traits)
N: number of families
t: full-sib interclass correlation (12
F
S
h)
For juveniles, an analysis of covariance was per-
formed to test the relationship between individual size
and density on the plate. Correlation study and one way
full-sib analysis of variance with family as the main ef-
fect were performed using the R software package
(http://cran.r-project.o rg/).
3. RESULTS
3.1. Adult Families
3.1.1. F am ily Assi gnment
Two individuals from each family were randomly chosen
and analyzed with COI and sperm lysin gene, evidencing
that all were of H. t. tuberculata subspecies (data not
shown). For each family, all progeny of 30 randomly
chosen individuals was studied with SSR following three
steps. The first one corresponds to the elimination of
families which present more than four alleles with high
frequency. As we want to work on bi-parental families,
each parent can bring a maximum of two alleles, and as
this species is diploid and as the SSR markers used were
known to amplify a non duplicated portion of the ge-
nome [22] the progeny must present a maximum of four
different alleles. Three families (30%) with too many
major alleles were eliminated. The second step corre-
sponds to the elimination of individuals which brings
alien alleles, never (or rarely) presents in other individu-
als. This strategy has allowed the elimination of indi-
viduals without parentage relationship with the others
(10 to 16.6 % of the progeny). And the last step corre-
sponds to the elimination of individuals which possess
the same alleles than the major ones, but which present
an association not compatible with the parental geno-
types found (0% to 6% of the progeny). For the seven
bi-parental families (excluding the pluri-parental fami-
lies), the number of full-sib individuals ranged from 23
to 27 (76.6% to 90%) after the elimination of foreign
individuals evidenced with the SSR markers. None of the
families have common parent.
3.1.2. Heritabi l i ti es
1) Morphological Traits
All three investigated morphological traits and the two
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V. Roussel et al. / Open Journal of Genetics 3 (2013) 224-233
Copyright © 2013 SciRes.
228
color traits showed a high variability (Figure 3) even in
some of cases, the difference between families seemed
less important (length/width, and condition factor). Three
families presented high values for shell length and width
traits: A2, A6 and A4, while four families had lower
values: A9, A8, A7 and A3. For weight trait, the highest
values were observed for A2 and A6 families and lowest
values for A7 and A3 families. Heritability estimates are
shown in Table 3 where the highest values are found for
weight, length and width (0.40, 0.37, and 0.29, respec-
tively). Condition factor and length/width presented low
heritability values (0.12 and 0.02 respectively), probably
linked to a non normality: the ratio between two normal
characters is non normal.
Distribution of the three more heritable traits and cor-
relations between these traits are given in Figure 4. The
normal distribution of these traits was tested with a
Shapiro test, and evidenced normality for all the mor-
Figure 3. Box plots of the different traits for each adult family.
Figure 4. Correlations and distribution of the five traits presenting the
highest heritability values. For each trait, the W value for Shapiro test is
indicated (*significant at 0.001; NSnon significant).
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V. Roussel et al. / Open Journal of Genetics 3 (2013) 224-233 229
phological traits. A high correlation (ranging from 0.84
to 0.88) between them was also evidenced, the most im-
portant one was found between weight and length.
2) Color Traits
As some visual observations in the natural environ-
ment seem to indicate that the red abalones are taller and
heavier than the others, we decided to investigate color
parameters. For that, most of the individuals (Table 2)
were also used to be described with image treatments.
We do not observe different colors, but only one (red-
brown) with different intensities. Two color traits (red
color: Cr, and Hue: H) presented a high variability (Fig-
ure 3).
These traits presented a low heritability with h² value
of 0.33 and 0.2 respectively (Table 3). The correlation
between these two traits was equal to 0.69 (Figure 4).
However, no correlation was shown between morpho-
logical and color traits. The blue color (Cb) presented a
low variability and heritability.
3.2. Juvenile Families
The results on size and density on the plates is repre-
sented on Figure 5 and evidenced a high variability be-
tween families. Five of them presented an important size
(J1, J3, J5, J7 and J9) and the other five presented a
lower size (J4, J6, J8, J11 and J12). For density, the
number of animals per 3600 cm2 presented a lower vari-
ability between families and a higher level of in-
tra-family variability. The correlation and covariance
between these two parameters evidenced a negative link
(r = 0.45, cov = 45.15) between size and density. Size
heritability for juveniles was calculated and presented a
high value of 0.74.
4. DISCUSSION
4.1. Adult Family Assignment
Our results showed that the assignment of individuals
after crossing in hatchery is necessary. Due to the high
number of crossing it is not excluded that fertilization of
eggs with sperm coming from different individuals may
occur. It was the case in three progenies among the 10
selected. In this study, it was important to determine the
genetic relationship between individuals of the progenies.
During the nursery period, small larvae are cultivated on
patches in the same tank. Even is the power of dispersal
is low for the larvae, a mix between families is also pos-
sible at this step.
The adult growth conditions includes an opening of
the cages and in most of the cases, some abalones can be
taken out theses cages during the bringing of fresh sea-
weeds. In such conditions, a mix between some adult
individuals is also possible. The aim of the parental as-
Table 3. Heritability (H²) and its standard deviation (
H²) for
all traits studied. For Adult families: CF: Condition Factor,
L/W: Length/Width, Cr: red color, Cb: blue color; H: Hue. For
Juvenile families: SizeJuv: Size of the shell.
Trait H²
Length
Width
Weight
CF
L/W
Cr
Cb
H
Sizejuv
0.37
0.29
0.40
0.12
0.02
0.33
0.08
0.20
0.51
0.11
0.07
0.13
0.02
0.00
0.09
0.01
0.04
0.18
signment was to select only the real full-sib progeny of
each family. But, as the genitors were not available, we
had to determine their genotypes from those of their
progeny.
Whereas it was shown the presence of Haliotis tuber-
culata coccinea COI signature in high proportion in
French Brittany [24] the analysis of this marker indicated
that all the analyzed individuals were of “tuberculata
sub-species. SSR analysis confirmed the absence of H. t.
coccinea in French Brittany. This was important to high-
light because nobody has tested the growth performances
of the two sub-species and the putative role of mito-
chondrial introgressed genomes in French Brittany.
Microsatellite markers were evidenced to be efficient
for parentage assignment in different species like com-
mon carp [28] for which eight microsatellites were used
to assign parentage in a full factorial cross of 10 dams
and 24 sires, the shrimp Penaeus japonicus [29] for
which eight microsatellites loci were used to discriminate
864 shrimp progeny originated from four ponds, abalone
Haliotis asinina [30] for which five polymorphic loci
were successfully used to assign parentage to young lar-
vae, and for adult individuals [31].
In our case, as the parents genotypes were not known,
the only solution to be sure of the common origin of the
progenies was to choose only full-sib individuals. In fact,
it the case of multi-parental progenies, the segregation of
individuals would be impossible without the parental
genotypes as start point. That is why the first step of the
study was to select only bi-parental families where the
number of alleles was reduced. The next steps corre-
sponding to the elimination of foreign individuals with
the study of allelic frequencies and genotype analysis
permit to select only the effective progeny of the parents
previously genotyped. This method is efficient to define
parentage assignment when the genitors genotypes are
not known but when the study of families without for-
eign individuals is necessary, like in heritability studies.
Copyright © 2013 SciRes. OPEN ACCESS
V. Roussel et al. / Open Journal of Genetics 3 (2013) 224-233
230
Figure 5. Box plots of length and density for each juvenile family. Size was measured after 90 days on 120 individuals. Adult fami-
lies from which they corresponded are indicated in Table 1.
4.2. Heritabilities
All the studied traits present a moderate to high diversity.
For instance, no markers assisted selection (MAS) pro-
grams exist for European abalone. The first step of such
programs, correspond to the identification of the traits
which can be improved by selection, by studying their
heritabilities. This work was done for several morpho-
logical or color traits, which can be of interest in selec-
tion. Our study was done on breeding conditions, by us-
ing families selected in a farm. Higher the heritability is,
and higher and easier the potential of improvement is. In
general, we consider that traits which present an herita-
bility value equal or superior to 0.2 can be useful for
selection, and can be improved during a breeding pro-
gram [32]. These results were obtained in a commercial
environment, so they can be used directly for improve-
ment programs. But according to this mating system, the
calculation of heritability allow to obtain a broad-sense
heritability, taking in account all the genetic parameters,
contrarily to the narrow-sense heritability, taking in ac-
count only the additive effects of the traits and leading to
a finer estimate of the heritability for breeding purposes.
Finer results could be obtained with another mating de-
sign, like the “Full Factorial Design with Few Dams”
which was evidenced to be superior to other ones [33]
and could give access to the narrow-sense heritability.
Heritabilities obtained for weight (0.40) appear to be
comparables to those obtained for Haliotis asinina [31]
which presents a weight heritability equal to 0.36. Shell
length and width presents heritabilities of 0.37 and 0.29
respectively which is comparable to the results obtained
with Haliotis discus hannai (0.36 and 0.32 respectively,
[34]) or Haliotis rufescens for which an heritability of
0.34 was evidenced for shell length [35], but our result
seems to be lower than the one obtained for Haliotis
asinina shell length which was of 0.48 [31]. Concerning
the shell morphology, it has been shown that heritability
varies during animal development and becomes higher at
the adult stage [35-37]. Consequently, for improving
these traits, it would be better to use 24 months values.
As the correlation between the three traits is very high,
the weight can likely be improved by selecting for shell
size.
The ratio length/width and the Condition Factor pre-
sents a low value of heritability, which can be linked to
the high values of intra-family variability, and to the non
normality of the characters. As the heritability calcula-
tion takes into account the variability at the intra and
inter-family level, when the first value is higher, the
value of heritability is lowered (in this case, the in-
tra-family variability is equal to 25% and 65% of the
inter-family variability, for each of the two traits, respec-
tively).
Some previous studies concerning the shell color were
done for Haliotis discus hannai [38,39] evidencing the
monogenic genetic control of the shell color variation in
this species presenting different colors (green, blue or
orange). The Mendelian segregation of the progenies
indicated that the color variant types were controlled by a
single locus presenting a recessive and a dominant allele.
As the shell color for Haliotis discus hannai is a mono-
genic trait, the objective of the color study was to have
information about genetic determinism of shell color in
Haliotis tuberculata for witch some observations at the
farm seemed to suspect the red shelled individuals to be
taller than the others. Contrarily to what was suspected
by observations, red ormers are not taller than the others.
Consequently, this visual marker can not be used for an
easy improvement of European abalones. As the shell
color character presents a non normal distribution, it
Copyright © 2013 SciRes. OPEN ACCESS
V. Roussel et al. / Open Journal of Genetics 3 (2013) 224-233 231
seems to be highly influenced with environmental factors,
so, for European abalone, the genetic control of the shell
color seems to be different than the one previously ob-
served for Haliotis discus hannai. It has been shown that
the abalone diet could modify the shell color [39], that is
why all the studied animals were feed with the same
fresh algal diet, mostly Palmaria palmata, Ulva lactuca
and Laminaria digitata, the ones which are usually con-
sumed by the wild abalones during the study to avoid the
expression of colors linked to the diet and thus, limit the
environmental effect for the studied trait.
Concerning Haliotis tuberculata, contrarily to other
species, shell color present only different variations of
red/brown, that is why we only studied the red color and
the hue. Other colors were not representative, and inten-
sity or saturation could not be representative because of
absence of variability linked to the shell characteristics
of our model. The high value of the correlation between
the two traits indicates that the red color is the majority
represented color in the shell panel.
Contrarily to Haliotis discus hannai [38,39], no men-
delian segregation could be evidenced in our progenies,
but the observed distribution (Figure 4) evidenced a role
of environmental conditions. If such a genetic control
was not evidenced before in abalone species, it is not the
case for another molluscan species like oyster [40,41].
These studies evidenced a polygenic control of the extern
shell pigmentation like in Crassostrea gigas with the
implication of one major gene in this trait.
4.3. Juvenile Im p ro ve ment
For Rodriguez [42], settlement is a process comprising
two phases: 1) a phase of searching for a suitable sub-
stratum, and 2) a phase of attachment and metamorphosis.
These parametres were excluded from our study because
they were controled in the Hatchery. At the fixation stage,
it was not possible to evidence a significant role of water
temperature on fixation rate. In all cases (14 to 22˚C),
this rate is always very variable and no temperature ap-
pears to bring better results than others. At this stage,
numerous environmental variables can be involved in
fixation rate, like algal composition on the plates [43].
At the benthic stage, we observed a negative link be-
tween the size of animals and the density, probably be-
cause of the limited food on the plate. Moreover, due to
the limited number of crossing adressed for this experi-
ment, the asignment of the descendance was not neces-
sary. The high heritability for the size (0.74) is probably
due to 1) the elimination of the density parameter, and 2)
the fact that for juvenile, we have less environmental
parameters to take in account compared with adult ani-
mals. It will be now important to study the correlation
between juvenile size and adult size. If this parameter is
high, it will be possible in the future, to select families at
a juvenile stage without waiting the animals to be adults.
5. CONCLUSION
Concerning shell color, contrarily to the Pacific abalone,
European abalone does not present a monogenic control
of this trait even if we could observe a major color (red).
This trait is not related to growth parameters. This study
brings other useful information about the European aba-
lone selection, particularly for biological traits like
weight and shell size, evidencing the high correlation
between these traits and their high broad-sense heritabil-
ity which indicates that a selection could be effective for
such traits. This high heritability value was also evi-
denced in juvenile families of 90 days and on adults.
6. ACKNOWLEDGEMENTS
This work was supported by EC (SUDEVAB No. 222156 “Sustainable
development of European SMEs engaged in abalone aquaculture”). The
authors would like to thank Yves Barrière for its helpful and construc-
tive comments to improve the manuscript.
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