Pattern of reserve storage of the two mussel species Perna perna and Mytilus galloprovincialis living on Moroccan coasts: annual variation and effect of pollution

2008·7.6 MB·English

by  Abdellatif Moukrim

©SociedadEspañoladeMalacología Iberus, 26 (1): 17-28, 2008
Pattern of reserve storage of the two mussel species Perna
perna and Mytilus galloprovincialis living on Moroccan
coasts: annual variation and effect ofpollution
Patrones de almacenamiento de reservas en dos especies de mejillón
Pernaperna y Mytilusgalloprovincialis de las costas de Marruecos:
variación anual y efecto de la contaminación
Abdellatif MOUKRIM*1 Mohamed ID HALLA*, Abderazak KAAYA*,
,
Abdellah BOUHAIMI*, Soumaya BENOMAR* et Michel MATHIEU**
Recibidoel23-XI-2005.Aceptadoel30-X-2007
ABSTRACT
The pattern of reserve storage and ¡ts ¡mportance ¡n the reproductive cycle of the two mus-
sel species living in Moroccan coasts, Perna perna and Mytilus galloprovincialis, were
studied comparatively, during two annual cycles. Study was conducted at a polluted and
an unpolluted site in Agadir bay. Stereological analysis shows that P. perna presents only
one type of storage cells (vesicular cells) storing glycogen. In M. galloprovincialis, two
types of storage cells are present: vesicular cells and adipogranular cells (containing
glycogen, lipids and proteins). In both species, seasonal variations of reserve tissue vol-
ume are conversely proportional to those of the germinal tissues. Reserve tissue appeared
in spring (May) and increased in summer. It decreased quickly from August onwards, and
disappeared between January and April. In M. galloprovincialis, adipogranular cells dis-
appeared before vesicular cells and reappeared first. In the polluted site, seasonal varia-
tion of reserve and germinal tissues is comparable to that in unpolluted site but the máxi-
mum valué of reserve tissue percentage is less ¡mportant. Moreover, during the year, this
tissue did not disappear. Biochemical analysis shows that mean valúes of glycogen and
proteins quantities are significantly higher in P. perna than in M. galloprovincialis. How-
ever, total lipids quantity mean is higher in M. galloprovincialis. Seasonal variations ofthe
three biochemical parameters present a similar profile in the two species. Compared to
unpolluted site animáis, in polluted one, molluscs possess low glycogen and high lipids lev-
éis. Seasonal variations ofthese parameters show a perturbed profile.
RESUMEN
Se ha estudiado y comparado el patrón de almacenamiento de reservas y su importancia
en el ciclo reproductor en dos especies de mejillón de las costas de Marruecos, Perna
pernay Mytilus galloprovincialis, durante dos ciclos anuales. Este estudio se llevó a cabo
en un sitio contaminado y otro no contaminado de la bahía de Agadir. El análisis estere-
ológico demostró que P. perna presenta un solo tipo de células de reserva (células vesicu-
lares) almacenando glucógeno. En M. galloprovincialis, hay dos tipos de células de
* LaboratoryAquaticEcosystems: Marine and Continental Field, BiologyDepartment, Sciences Faculty, Ibn
ZohrUniversity, BP 8106, 80000,Agadir, Morocco.
**LaboratoryMarineBiologyandBiotechnology, I. B. B.A., CaenUniversity, France.
1Correspondingauthor.
17
Iberus, 26 (1), 2008
reserva: células vesiculares y células adipogranulares (conteniendo glucógeno, lípidos y
proteínas). En ambas especies, las variaciones estacionales del volumen de tejido de
reserva son inversamente proporcionales a las del tejido germinal. El tejido de reservas
apareció en la primavera (mayo) y se incrementó en verano. A partir de agosto, dismin-
uyó rápidamente y desapareció entre enero y abril. En M. galloprovincialis, las células
adipogranulares desaparecieron antes que las células vesiculares y son las primeras en
aparecer en el siguiente ciclo. En el sitio contaminado, la variación estacional de tejidos
de reserva y germinales es similar a la del sitio no contaminado, salvo que el porcentaje
máximo de tejido de reserva es menor. Además, este tejido no desapareció a lo largo del
año. Los análisis bioquímicos muestran que las cantidades promedias de glucógeno y de
proteínas son significativamente más altas en P. perno que en M. galloprovincialis. Sin
embargo, el promedio de lipidos totales fue mayor en M. galloprovincialis. Las varia-
ciones estacionales de los tres parámetros presentan un perfil similar en las dos especies.
Comparados con los del sitio no contaminado, los animales del sitio contaminado poseen
niveles bajos en glucógeno y altos en lípidos. Las variaciones estacionales de estos
parámetros muestran un perfil perturbado.
KEYWORDS:Agadir,Morocco,mussels,Mytilusgalloprovincialis,Pernaperna,pollutioneffects,reproductive
cycle, reservesstrategy.
PALABRAS CLAVE:Agadir, Marruecos,mejillones,Mytilusgalloprovincialis, Pernaperna, efectosdelaconta-
minación, cicloreproductor, estrategiasdereserva.
INTRODUCTION
Two sympatric mussel species are by Id Halla et al. (1997), regard the
found along the Moroccan coast: the duration of the principal spawning
African mussel Perna perna and the period (more importantforP. perna) and
Mediterranean mussel Mytilus gallo- the genital activity rhythm in summer
provincialis. The first species is located in (reducedinthis species).
the north of its geographical distribu- In view of the importance of
tion; the second one in its Southern reserves in the reproductive cycle
limit. InAgadir bay, these local popula- (Bayne, Bubel, Gabbott, Livingstone,
tions of mussels have important com- Lowe and Moore, 1982; Lowe, Moore
mercial valúes (Id Halla, 1997) and and Bayne, 1982; Pipe, 1987) and of the
environmental interest (Najimi, particularities of reserve strategy in
Bouhaimi, Daubéze, Zekhnini, Pel- Mytilidae (strategy essentiallybased on
LERIN, NARBONNE, AND MOUKRIM, 1997; the glycogen, presence of specific
Kaaya, Najimi, Ribera, Narbonne,and storage cells and existence of a direct
Moukrim, 1999; Moukrim, Kaaya, relationship between reserve metabo-
Najimi, Roméo, Gnassia-Barelli, and lism and reproductive cycle), it was
Narbonne,2000) assentinelspecies. interesting to conduct a comparative
The few studies carried out on study ofP. perna and M. galloprovincialis
mussel biology in this area, concern in order to describe the reserves strat-
only some aspects of the reproduction egy for these two species living in the
cycle (Shafee, 1989; Id Halla, same environmental conditions. The
Bouhaimi, Zekhnini, Narbonne, two molluscs present an important dif-
Mathieu, and Moukrim, 1997). They ference regarding the cells involved in
showed that P. perna and M. galloprovin- the reserve storage. As indicated by
cialis present synchronous reproductive Lunetta (1969) P. perna presents only
cycles, and breed throughout the year one type of storage cells (vesicular cells
with a principal spawning period in or glycogencells), storingespeciallythe
spring. The only differences observed glycogen however, in M. galloprovin-
;
18
MoukrimETAL.: Reserves strategyofmussels in Moroccan coasts
cialis (Herlin-Houtteville, 1974; Dan- reproduction cycle in Mytilus gallo-
ton, Kiymoto, Komaru, Wada, Awaji provincialis and Perna perna, an histo-
and Mathieu, 1996), two types of chemical study (stereological analysis)
storage cells are present, vesicular cells was conducted in the mantle. Thirty
(storing glycogen) and adipogranular adult mussels were collected and
cells (containing glycogen, lipids and directly fixed in Gendre liquid for 3
proteins). days. Animáis were then removed from
Furthermore, beyond the determina- shells and a central portion of mantle
tion ofpattern ofreserve storage and its tissuewascorrectlyexcised andembed-
importance in the reproductive cycle of ded in paraffin. Sections of 6 pm were
the two mussels living in Moroccan cut and stained by the periodic acid of
coasts, this work studies the impact of Schiff (PAS). Stereological analysis was
pollution on this pattern. Therefore, a applied according the method of
comparative study of two sites (unpol- Weibel, Kistler, and Scherle (1966)
lutedandpolluted)wasconducted. which quantified the volume occupied
by the reserve and germinal tissues.
The cell types were determined accord-
MATERIALAND METHODS ing the definition of Lubet (1959): i)
adipogranular cells (20-25 pm for
Sampling length, 4.5-5 pm for length of nucleus,
This study was conducted during green coloration, contain lipids, pro-
two annual reproductive cycles teins and glycogen), and ii) vesicular
(October 1994 to August 1996). Two cells (50-80 pm for length, 3-5 pm for
types of sites, representative of the length of nucleus, pink coloration,
Agadirmarinebaywere considered: i) a containonly glycogen)
reference site (unpolluted). Cap Ghir,
located 50 km north ofAgadir City and Biochemicalanalysis
far from any human activity, and ii) a Biochemical analysis (glycogen,
polluted site (Anza) located 5 km north lipids and proteins) was carried out on
of Agadir and receiving the industrial mussel mantle which in Mytilidae, con-
and domestic untreated waste waters of stitutes animportantorgan in storage of
Anza zone. Many studies, conducted reserves. Monthly,sixtyadultswereran-
during the same period of the present domly sampled, quickly transferred to
study, showed that this site is contami- the laboratory in isotherm conditions
nated by heavy metáis and PAHs either and frozen at -30°C. Glycogen, total
accumulated by mussels or in sediment lipids and proteins were respectively
(Id Halla, 1997; Najimi, 1997; measured according the methods of
Moukrim, Kaaya, Najimi, Roméo, Duchateau and Florkin (1959),
Gnassia-Barelli and Narbonne 2000; Folch, Lees and Sloane-Stanley
Kaaya, 2002), with some perturbations (1957) and Lowry (1951). Rates of these
in the physical and Chemical parameters compounds were expressed as mg/g
ofseawater (IdHalla, 1997). freshweight(mg/gFW).
During this study, for each month,
mm
ninety individuáis of 35 for each Statistical analysis
species are collected at random in each Stereological analysis was expressed
of the two sites. 30 individuáis/ as a percentage of the total volume of
species/sites were subject to stereologi- mantle tissue biochemical results as
;
cal analysis and 60 individuáis/ means ± standard deviations. The statis-
species/sites were dedicated to the bio- tical significance of difference between
chemicalanalysis. samples was evaluated by the "t" test
using the Statistica software (Release
Stereological analysis 4.5AStatSoft Inc. Ed. 1993). A "P" valué
In order to follow the seasonal vari- of less than 0.05 was considered as sta-
ation of the glycogen according the tisticallysignificant.
19
Iberus, 26 (1), 2008
Figure 1. Cells implicated in the reserve storage in Pernaperna (A) (only one type ofcells: ve:
vesicular cells) and Mytilusgalloprovincialis (B) (two types ofcells, ve: vesicular cells; adge: adi-
pogranularcells). Scalebars 10 pm.
Figura 1. Célulasimplicadasen laacumulacióndereservasen Pernaperna (A) (solo un tipodecélulas:
ve: células vesiculares)yMytilus galloprovincialis (B) (dostiposdecélulas, ve: células vesiculares;adge:
célulasadipogranulares). Escalas 10pm.
RESULTS centage is lower (57% and 62% respec-
tively in the first and second year).
Stereological analysis Moreover, during the year, this tissue
Figure 1A shows that the mantle of did not disappear. The minimum valué
Perna perna presents only one type of recordedwas7-10%inFebruary.
storage cells: vesicular cells (VC). In For Mytilusgalloprovincialis (Fig. 2B),
Mytilus galloprovincialis (Fig. IB), two the volume of germinal tissue increases
types of storage cells are presentí adi- in autumn and in the beginning of
pogranular cells (ADGC) and vesicular winter to reach a máximum in February
cells (VC). (75%). Thereafter, we observe a reduc-
For P. perna, the respective volumes tion of the surface occupied by this
of germinal and reserve tissues are con- tissue until October where the
versely proportional (Fig. 2A). The sea- minimum (12%) is reached. During the
sonal profile is similar during the two second eyele a similar evolution is
studied annual eyeles. The volume of recorded. Otherwise, as with P. perna,
germinal tissue increases from October the volume of germinal tissue is
to February, when the máximum is inversely proportional to reserve tissue.
reached (respectively 72% and 77% in Nevertheless, in this case, the máximum
the first and second year). From March isreachedinOctober (64%),whereasthe
onwards, the germinal tissue volume disappearance takes place from January
decreases to reach the minimum in to March for the two studied yearly
August (respectively 8% and 6% in the eyeles. In the polluted site (Fig. 3B), the
first and second year). The reserve reserve tissue presents a seasonal evolu-
tissues appeared in spring (May) and tionsimilartothereferencesite. Besides,
increased until reaching maximalvalúes this tissue never disappears as in P.
in summer (August). They decreased perna. The occupied minimal volume is
quickly and disappeared between 5%reachedinFebruary.
January and April. In the polluted site Moreover, for M. galloprovincialis, in
(Fig. 3A), the seasonal variation of thereferencesite,theadipogranularcells
reserve and germinal tissues is similar disappeared before the vesicular cells
to that in the reference site but the andthenreappearedfirst. Inthepolluted
máximum valué of reserve tissues per- site the two cellular categories persist
20
MoukrimETAL. Reserves strategyofmussels in Moroccan coasts
:
A
^ O
Reservetissue Germinaltissue Others
100%
90%
OND JFMAM JASOND JFMAM JA
J J
B
ADGC VC Germinaltissue Others
I |
Figure 2. Seasonal variation ofgerminal and reserve tissues in Pernaperna (A) and Mytilusgallo-
provincialis(B) in the unpollutedsite. (VC: vesicularcells storingglycogen;ADGC: adipogranular
cells, containingglycogen, lipidsandproteins).
Figura2. Variación estacionaldelostejidosgerminalydereservasen Pernaperna (A)yMytilus gallo-
provincialis (B) en elsitio no contaminado. (VC: células vesicularesalmacenandoglucógeno;ADGC:
célulasadipogranulares, conteniendoglucógeno, lípidosyproteínas).
during all the year. However, anoscilla- Perna perna and F= 2.65 P= 4.7xl0'6 for
;
tion can be observed in the volumes Mytilus galloprovincialis) and exhibit a
occupiedbythetwocategoriesofcells. similar profile (Fig. 4A). The glycogen
increases in spring (from April), reaches
Biochemical analysis a maximal valué in August (219.4 and
Glycogen: The mean amount of 191.9 mg/g FW in Perna perna and
glycogen is significantly (F= 11.19 and Mytilus galloprovincialis respectively),
P= 0.027) higher in Perna perna than in then decreases during autumn and
Mytilus galloprovincialis (respectively winter. The minimal valúes are noted in
59.6 ± 7.36 and 48.7 ± 4.78 mg/g FW). February (0.39 and 0.34 mg/g FW in
For the two species, the seasonal varia- Perna perna and Mytilus galloprovincialis
tions are significant (F= 4.95 P= 10"6 for respectively).
;
21
''''
Iberus, 26 (1), 2008
ioo%-
90%-
80%- L
70% H * i»
60%- 11 "1
50%- ¡i li p i . i 1
40% i I I i ¡ iI ili,1
%
30 i i
%
20 l II I
10%' lli
Wm
o%- OND JFMAM JA SOND JFMAM JA
J J
^ Q
Reservetissue Germinaltissue Others
100%
90%
80%
70%
60%
50%
40%
30%
20%
10%
0% ONDJFMAMJ JASONDJFMAMJ JA
B H ^ Q
¡H ADGC VC Germinaltissue Others
Figure 3. Seasonal variation ofgerminal and reserve tissues in Pernaperna (A) andMytilusgallo-
provincialis (B) in the polluted site. (VC: vesicular cells storing glycogen; ADGC: adipogranular
cells, containingglycogen, lipidsandproteins).
Figura3. Variación estacionaldelostejidosgerminalydereservasen Pernaperna (A)yMytilus gallo-
provincialis (B)en elsitio contaminado. (VC:células vesicularesalmacenandoglucógeno;ADG: células
adipogranulares, conteniendoglucógeno, lípidosyproteínas).
In the polluted site (Fig. 4B), the dif- peaks, thefirstinJune (96.05mg/gFW),
ference between the mean amount of the second in November (118.87 mg/g
glycogen in the two species (39.75 and FW) andthethird inMayofsecondyear
23.44 mg/g FW in P. perna and Mytilus (159.02 mg/g FW). For M. galloprovin-
gnailfliocparnotvi(nFc=ia6li.s25r7esapnedctPiv=el0y.)130is).noOtthseirg-- c6i5a.l0is3,aonndly153t.w6o4 mpge/agksFaWrerersepeccotvievreeldy
wise, their seasonal variation are signifi- inMayandNovemberofthefirstyear.
cantly different (F= 4.03 and P= 10'6in The comparison of valúes for refer-
P. perna and F= 9.78 and P= 10~7 in M. ence and polluted site animáis shows a
galloprovincialis). The seasonal profile is significant difference. The valúes in the
completely different for the two mol- polluted site are less important (39.8 ±
luscs: For P. perna, it presents three 13.36 instead of59.6 ± 7.36 mg/g FW in
22
:
MoukrimETAL Reserves strategyofmussels in Moroccan coasts
Pperna M.galloprovincialis
Month
Figure 4. Seasonal variation ofglycogen in the mantle ofPernaperna andMytilusgalloprovincialis
inthereferencesite (A) andthepollutedsite (B)
Figura4. Variación estacionaldelglucógeno elelmantodePernapernayMytilus galloprovincialis en
elsitiodereferencia (A)yenelsitiocontaminado (B)
thereferencesite,forPernaperna). More- In the polluted site, the two species
over, the seasonal profile of glycogen present a significant difference between
contení (Fig. 4B) presents some pertur- total lipids mean valúes (respectively
bationscomparedtothereferencesite. 231.4 ± 21.47 and 135.5 ± 16.93 mg/g
Lipids A significant difference was FW in Perna perna and Mytilus gallo-
:
notedbetweenthemeanamountsoftotal provincialis). Besides, the difference in
lipids in the two mussels species (92.86 their seasonal variation (Fig. 5B) is sig-
and 125.04 mg/g FW in P. perna and nificant with F= 2.59 and P= 0.002 in P.
Mytilus galloprovincialis respectively). perna and F= 3.60 and P= 4.5xl0"4 in M.
However,thedifferenceoftheirseasonal galloprovincialis.
variationaresignificantwithF=4.42and Ótherwise, the valúes are generally
P= 10'6 in P. perna and F= 3.6 and P= higher for the polluted site than the ref-
4.5xl0'5inM.galloprovincialis. Inthefirst erence site for the two species. More-
year,theseasonalprofile(Fig.5A)issimilar over, compared to the unpolluted site,
for the two molluscs. The lipid contení the seasonal variation (Fig. 5B) shows a
increasedinautumn,withamaximalvalué perturbed profile with several peaks
inDecember(respectively354.3and316.9 duringtheannualcycleandamáximum
mg/gFWinPernapernaandMytilusgal- valúes is reached rather in August
loprovincialis),anddecreasedinwinterand (777.03 mg/g FW in P. perna and 659.95
spring. However, in the second year, a mg/gFWinM.galloprovincialis).
slightincreasewasnotedinsummer(June Proteins Themeanconteníofprotein
-July) onlyinP. perna. issignificantlyhigherinPernaperna (28.9
23
Iberus, 26 (1), 2008
P.perna a M. galloprovincialis
Month
Figure 5. Seasonal variation oflipids in the mantle ofPernaperna and Mytilusgalloprovincialis in
thereferencesite (A) andthepollutedsite (B).
Figura5. Variación estacionaldeloslípidosen elmantodePernapernayMytilus galloprovincialis en
elsitiodereferencia (A)yenelsitiocontaminado (B).
± 3.51 mg/g FW) compared to Mytilus DISCUSSION
galloprovincialis (20.2 ± 3.17 mg/g FW).
However,theseasonalprofile(Fig.6A)is The comparative study of the
similarforthe two species. Themaximal reserve pattern of the two mussels
valúes were generally recorded in species living in the Moroccan coasts,
summer and autumn in the first year Perna perna and Mytilus galloprovincialis,
and in winter and beginning spring in sampled in the same site (Cap Ghir,
the second year, whereas the minimal Agadir bay), shows that, in spite of the
valúes were reached at the end of difference in their reserve tissues (only
autumnandthebeginningofwinter. one cell type, vesicular cells, in Perna
In the polluted site (Fig. 6B), the perna two cell types, adipogranular
;
mean amount of protein is higher in P. cells and vesicular cells, inMytilusgallo-
perna (30.11 ± 7.742 mg/g FW) than in provincialis), the two molluscs have a
M. galloprovincialis (19.74 mg/g FW). similarfluctuation.
However, the mean valúes and the sea- This strategy presents cycles (of re-
sonal profile do not show any signifi- serve compounds and cells involved in
cant difference compared with those the storage) which, compared to the cy-
observed fromthe referencesite (F= 1.08 cle ofreproduction (determined in these
and P= 0.30 for Perna perna F= 0.31 and same animáis by Id Halla etal., 1997)
;
P= 0.57 for Mytilus galloprovincialis). For are inversely proportional to it. The ac-
the two species, the máximum valúes cumulation of reserves in these cells is
wererecordedinsummerand autumn. related to the period of reduced sexual
24
Moukrim ETAL.: Reserves strategyofmussels in Moroccan coasts
P.perna a M. galloprovincialis
Figure 6. Seasonal variation ofproteins in the mantle ofPernaperna and Mytilusgalloprovincialis
inthereferencesite (A) andthepollutedsite (B).
Figura 6. Variación estacionaldelasproteínaselmanto dePernapernayMytilus galloprovincialis en
elsitiodereferencia(A)yenelsitiocontaminado (B).
activity (in summer). The low levels of used in gonad restoration following
reserve are obtained inautumn and par- spawning during spring and summer
ticularly in winter (gametogenesis and probably derived directly from feeding
spawning periods). Similar results have since ADG cells disappeared from the
been reported in Perna perna from mantleinearlyspring (Villalba, 1995).
Brazilian coasts (Lunetta, 1969) and in Furthermore, the reserve accumula-
Mytilus galloprovincialis from the French tionin thetwomollusc speciesis related
coasts (Herlin-Houtteville, 1974; to the proliferation of the phytoplanc-
Danton, Kiymoto, Komaru, Wada, tonic biomass linked to upwelling cur-
Awaji and Mathieu, 1996). Also, in the rents which take place, between Febru-
Ria de Vigo (Spain), the profile of the ary and August, in the Agadir bay and
variations of the gonadic Índex and so- more precisely in Cap Ghir (Belveze,
matic Índex in cultured mussels show 1984 Agoumi and Orbi, 1992).
;
clearly their inverse and gradual fluctu- Cáceres-Martínez and Figueras
ations (Cáceres-Martínez and (1998) reported thatthis increaseinfood
Figueras, 1998). This association be- availability for mussels in the area
tween gonad and storage tissue cycles favours the accumulation of reserves
inmussels is well known. Decline ofthe during this period. These results also
ADG
cells occurs during gametogenesis confirmtheciósedependence, described
by a lysosomal autophagic mechanism by Mathieu (1987), between the reserve
(Bayne etal., 1982; Lowe, Moore and storageandenvironmentalconditionsin
Bayne; 1982; Pipe, 1987). The energy marine ecosystems. As suggested by
25
Iberus, 26 (1), 2008
this author, the disappearanceofreserve upwelling currents which provide food
tissue in mussels seems to be under availability, ensuring an abundant
endocrine control via cerebroid ganglia planktonic food supply for mussels.
which provoke disappearance of adi- According to Cáceres-Martínez and
pogranular cells and vesicular cells in Figueras (1998), massive spawns occur
the mantle after liberation of their in spring coinciding with an increase in
reserves which are indispensable for temperature and chlorophyll-a concen-
gametogenesis and spawning process. traron in the area providing favorable
The synchronic character of this disap- conditions for larval growth. In winter,
pearance, inPerna yerna andMytilusgal- the second peak of lipids coincides with
loyrovincialis, could be explained by the the maturity period of gametes. This
existence ofthe same mechanism for the peak takes place just after the disap-
controlofreservesinbothspecies. pearance of the glycogen peak. It is
The comparison of the reserve com- probably a result of the glycogen trans-
pounds in the two molluscs shows that formaron. The metabolic conversión of
the glycogen, total lipids and proteins glycogen to lipids has been reported by
contents are higher in Perna yerna (in Zaba and Davies (1980), using 14C-
spite of the presence ofonly one type of glucose. According to Gosling (1992),
reserve storage cells, vesicular cells) the mantle is considered as the organ of
compared to Mytilus galloyrovincialis. many and extensive metabolic transfor-
These results could explain the differ- mations during the sexual cycle. The
ences observed by Id Halla et al. reserves, particularly the glycogen,
(1997) between the reproductive cycles accumulated during summer, are used
of these bivalves. According to these inautumnand winter for the gametoge-
authors, in Perna yerna, compared to nesis. Similar results were reported by
Mytilus galloyrovincialis, the main- Shafee (1989) in Perna yicta of Temara
spawningperiod in spring is longer and (NorthofMorocco).
the sexual activity in summer is In the polluted site (Anza), many
reduced. Otherwise, the important perturbations in the metabolism of
reserve levels in this species could be reserves were noted comparatively to
attributed to the spatial distribution of the reference site (Cap Ghir). The
each species: Perna yerna lives essen- reserve tissues, which disappeared in
tially at the infra-littoral level and is winterandatthebeginningofspring, in
more immersed thanMytilusgalloyrovin- mussels ofCap Ghir, persist throughout
cialis (Id Hallaetal., 1997) and, conse- the sexual cycle in Anza mussels. This
quently, has access to more nutrients, could probably be a result of the pollu-
thus allowing the synthesis and storage tion effect on the cerebroid ganglions
of more reserves. Seed (1976) showed neurosecretions which are, according to
that the gonadal development was Lubet, Herlin, Mathieu, and Collin
faster in mussels from the low intertidal (1976) and Mathieu (1987) involved in
zone, than in those from the upper zone thecontrolofreservecells.
and related these results to food avail- The analysis of the seasonal profile
ability. Other studies associated local ofthe reserve levels in mussels sampled
variations in gonadal cycle with envi- in the polluted site shows some pertur-
ronmental conditions (Ferrán, 1991; bations as compared to the reference
Villalba, 1995). According to Cáceres- site. For example, the glycogen content
Martínezand Figueras (1998), there is is low in summer (August), in spite of
no influence oflocality and depth in the the availability of phytoplanctonic
gonadal development of cultured biomass in this period. This is probably
mussels. linked to the stress caused by pollution
The seasonalprofile ofthebiochemi- of industrial and domestic waste waters
cal reserves studied shows that the first discharged directly in this site, without
peak ofglycogen and lipids, recorded in any treatment. This fact was indicated
summer, is related to the occurrence of by Deslous-Paoli, Wolowicz, and
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