Reproduction of Donax trunculus in the littoral of Huelva (southern Atlantic Spain): is there any difference with the Mediterranean population from the Andalusian coast?

2011·7.2 MB·English

by  Cristina Tirado

1
©SociedadEspañoladeMalacologta Iberus, 29 (1): 47-57, 201
Reproduction ofDonax trunculus in the littoral of Huelva
(southern Atlantic Spain): is there any difference with the
Mediterranean population from the Andalusian coast?
Reproducción de Donax trunculus en el litoral de Huelva (suroeste
Adántico de España): ¿haydiferencias con la población mediterránea
de la costa andaluza?
CristinaTIRADO,José Luis RUEDA and Carmen SALAS*
Recibidoel13-IV-2011.Aceptadoelll-V-2011
ABSTRACT
The reproductive cycle of D. trunculus L., 1758 was studied using histology and changes
¡n flesh dry weight, ¡n the littoral of Huelva (southern Atlantic Spain) from June 1990 to
May 1991. The spawning period is essentially synchronic, and extends from February to
August, with different individual intensity. Three peaks of spawning have been recorded,
April, June and July. The resting period ranges from September to December, with the
whole population in cytolized stage in October. The favourable environmental variables,
such as high levels of chlorophyll a and relatively mild seawater temperatures allow this
extensive reproductive period. This cycle shows a diphase ofthe spawning period with the
Mediterranean population from Málaga, which should imply a different cióse season for
each population.
RESUMEN
Se estudia el ciclo reproductor de D. trunculus L., 1758 mediante histología y cambios en
la biomasa, en el litoral de Huelva (sur de España Atlántico) entre junio de 1990 y mayo
de 1991. El periodo de puesta es básicamente sincrónico y se extiende desde febrero
hasta agosto, con intensidad variable según los individuos. Se han registrado tres picos
de puesta: abril, junio y julio. El periodo de reposo ocurre entre septiembre y diciembre,
con toda la población en la fase citolítica en octubre. Las variables ambientales favora-
bles, tales como los altos niveles de clorofila ay las temperaturas relativamente templadas
del agua permiten un periodo reproductor largo. Este ciclo muestra un desfase del perí-
odo de puesta con relación a la población mediterránea de Málaga, por lo que se reco-
mienda un periodo de veda diferente para cada población.
INTRODUCTION
The overexploitation, for many the fisheries. Until 2003, the law in
years, of some marketable shellfish Andalusia (autonomous región inclu-
species in southern Spain has mainly ding eight southern provinces of Spain)
beendue to anincorrectmanagementof ruled anextensive cióse season (oversix
* DepartamentodeBiologíaAnimal, FacultaddeCiencias,UniversidaddeMálaga,E-29071 Málaga,España.
47
Iberus, 29 (1), 2011
months) for most of the marketable mercial species, D. trunculus has been
bivalves of this area. Because of the intensively studied for fisheries mana-
incompatibility of these extensive gement (Baldaccini and Bianucci,
periods with a profitable economic acti- 1984, Fischer, Bauchot and Schenei-
vity, it was not enforced. The study of der, 1987), parasitism and predation
the reproduction of the populations of (Ramón, Gracenea and González-
Donacidae in the Mediterranean littoral Moreno, 1999, Salas, Tirado and
of Málaga (Tirado and Salas, 1998, Manjón-Cabeza, 2001), population
)
1999) pointed out the possibility ofesta- dynamics (Mouézaand Chessel, 1976;
blishing aneffective rule with a reduced Guillou and Le Moal, 1980; Bayed
cióse seasonthatwould stillbe compati- and Guillou 1985; MazéandLaborda
ble with profitable fishery activities. 1988; Neuberger-Cywiak, Achituv
These results led regional fishery autho- and Mizrahi, 1990; Zeichen, Agnesi,
rities to promote a research project for Mariani, Maccaroni and Ardizzone,
the study of reproductive cycles of the 2002) and growth and reproduction at
most important shellfish, aimed at different places of the distribution area
adjusting the cióse season to thebiology (Lucas, 1965; Badino and Marchioni
of each species and consequently to 1972; Mouezaand Frenkiel-Renault,
improve the managementofthese fishe- 1973; Bayed 1990; Neuberger-Cywiak
ries (TiradoandRodríguezdelaRúa, et al. 1990; Tirado and Salas 1998;
2000 Gaspar, Ferreiraand Monteiro, 1999;
.
One of the studied species was Deval2009). All this researchhas revea-
Donax trunculus L. 1785 ("coquina") led a biological and physiological varia-
with a very important consumer bility of the populations in relation to
market, mostly in the province of environmental factors. Therefore, the
Huelva (Southwest coast). The repro- aim of this paper is to study the repro-
duction of this species was studied in ductive cycle of D. trunculus from
the Mediterranean littoral ofAndalusia Huelva, and to point out the differences
(Tirado and Salas, 1998), but it is well between theAtlantic and the Mediterra-
known that reproduction in bivalves is nean populations in order to request the
strongly related to environmental varia- authorities to take into account the
bles, such as temperature, availability of biology of the species in a particular
food or type of beach, among others area for a better management of the
(Bayne 1976; Brown and McLahlan, resources.
2006). The environmental characteristics
of the Atlantic shallow littoral are very
different from those of the Mediterra- MATERIALAND METHODS
nean. The fishingmethodsarealso diffe-
rent, in the Mediterranean littoral the The sampling area is located in the
fishery is made by authorized boats, littoral of Doñana (Southwest Spain)
whereas in the Atlantic littoral the fis- (36° 52'N - 6o26'W) (Fig. 1), in an exten-
hermen use individual dredges drawn sive beach, more than 20 km long and
m
backwards in shallow water. For these 100-200 wide, with a tidal range
m
reasons, the study of the Donax truncu- which can reach 3.6 in spring tides.
lus population from the Atlantic littoral The beach is of fine grain and gentle
ofHuelvawasundertaken. slope that can be considered as a dissi-
Donax trunculus is a littoral species pative beach (Schlacher, Schoeman,
widely distributed from Brittany Dugan, Lastraand Jones, 2008). The
(French coast) (Lucas, 1965; Ansell samples were collected, on a sandy
AND LAGARDERE, 1980; GUILLOU AND LE bottom at 0.4 m depth, from June 1999
Moal, 1980) to Southern Morocco to May 2000, with monthly frequency
(Pasteur Humbert, 1962) and in the from October to February and twice a
Mediterranean (Sabelli, Gianuzzi- month during the spring and summer
Savelli and Bedulli, 1990). As a com- months. The specimens were captured
48
TiradoETAL.: Reproduction ofDonaxtrunculusin the littoral ofHuelva
37°N
36°50’
36°40’
W 36°30*
06°50‘ 06°40' 06°30' 06°20‘ O^IO1
Figure 1. Samplingarea. Figure2. GearusedforcommercialcollectingofDonaxtrunculus.
Figura 1.Areademuestreo. Figura2. RastrousadoparalapescadeDonaxtrunculus.
witha dredgeof45 cmwidth, with9 cm and by the variation of the size of the
long teeth. The meshwas 1.75 cm, usual specimens between successive samples,
amongthefishermenofthearea (Fig2). the variation of flesh dry weight was
Atotal of4333 specimens of D. trun- estimated for an individual of 29 mm
mm
culus, between 13 and 44 in length, length (mean size of the population
were examined; ofthese 3798 were used studied). For that we took into account
for the analysis of the flesh dry weight theregressionlinesforeverysample.
variation(about200individuáis/sample) For histological processing, speci-
and 535 specimens forhistological study mens were anaesthetized with MgCk,
(usually30permonth). fixed in 10% formaldehyde, embedded
The length (L) of every specimen in paraffin, sectioned at 10 jum and
was measured to the nearest millimetre, stained with haematoxylin of Carazzi
and the softparts were dried in an oven and eosin, and a trichromic staining
at 100 °C for 24 h, and weighed to the (VOF according to Gutiérrez (1967)) of
nearest milligram (flesh dry weight, haematoxylin of Carazzi, light green,
FDW). Two different indices of condi- orange G and acid fuchsine. The stages
tion were applied, FDW/L3 variation, of development of the gonad were
and that proposed by Crosby and Gale scored according to the scale proposed
(1990) as FDW*1000/volunte of the by De Villiers (1975) for D. serra
internal cavity of the shell (considering Róding, 1798 in South Africa, who pro-
the millilitres of water as milligrams) posedfivestages:
which is referred to as CI. The regres- Cytolized. The alveoli are very small
sion of flesh dry weight on the length and wide apart. Some clams can be
was calculated for each sample to estí- sexedwhenafewgametesarepresent.
mate the variation in biomass of a stan- Preactive. The alveoli have clearly
dard individual, based on the logarith- defined alveolar walls. They are inter-
mic transformation of Ricker's function sected by broad, continuous transverse
W= aLb (Ricker, 1975), where Wis the fascicles. Mostclamscanbesexed.
weight, L is the length, a is the ordinate Active. The alveoli are large and
atorigin, and b istheslope. Tominimize usually adjacent. The alveolar walls are
the bias introduced by the somatic always complete. Germ cells in various
growth of individuáis during the cycle stages of development fill the alveoli
49
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Iberus, 29 (1), 201
and are both actively increasing and half of September (23 °C) and the
enlarging. mínimum (12.5 °C) in December. The
Spawning. The alveolar pattern is most important decrease was recorded
disturbed and the alveolar walls are from October to November (9.5 °C), and
oftenbroken. The alveoliareoftenflatte- conversely, the highest increase (4.5 °C)
ned and show an orientation towards was observed from February to the first
thecentreofthegonad. halfofMarch.
Postactive. The amount of germ cells The chlorophyll a levels were higher
varíes, depending on the intensity of than 2 jug/l throughout the cycle,
spawning and the time that has elapsed showing an irregular pattern, with two
since spawning took place. Phagocitic important peaks, in September (24.3
cellsarecommon. jug/l)andMarch(16.1 jug/l).
Thespeciesshowedasexualdifferen-
tiation during the time ofsexual activity. Sexratio
During the active period, the ovaries of The sex ratio was determined on
D. trunculus are dark blue whereas the specimens with shell length ranging
testes have a viscous aspects and a from 13 to 44 mm. In the samples from
whitish-orangecolour,whichmakespos- December to the end ofJuly it is possi-
sible to identify the sex macroscopically ble to identify the sex of the whole
ofmostofthespecimens. population according to the colour and
To evalúate the possible influence of external aspect of the gonad. A total of
environmental factors on the cycle, the 2564 specimens were examined for sex-
temperature of sea water at the surface ratio study (all the specimens from his-
was measured simultaneously with the tology and those ofbiomass study from
collection of the individuáis. Samples of December to July), of which 1268 were
water (11) were taken for determination males (49.45%) and 1296 females
of chlorophyll a. Pigment analyses were (50.55%) (Fig. 4). The sex ratio for all
carried out by filtering the water them can be considered as 1:1 (x2= 0.7,
through Whatman GF/C glass filters. P>0.95). The smallest specimen exami-
The pigments of the retained cells were ned with gonad differentiated was a
then extracted with acetone for 12 h in femaleof13.8mm.
cool, dark conditions, following the
recommendations of Lorenzen and Sexual cycle
Jeffrey (1980). Concentrations of chlo- Flesh dry weight The variation of
:
rophyll a were calculated using the fleshdryweight-lengthratio (FDW/L3
)
trichromatic equations of Jeffrey and during the annual cycle is shown in
Humphrey (1975). Figure 5. The mean monthly valúes of
ThetestofKolmogorov-Smirnovand both variables, flesh dry weight (FDW)
Kendal and Pearson's rank correlations and size (L3 were considered in 3798
)
included in the program SPSS 8.0, were specimens. The standard deviations
usedtocheckthedistributionofthedata. range between 10 and 21%, being larger
Crosscorrelationbetweenbothcondition than the standard deviations observed
indexes and percentage of spawning in the monthly mean size (between 6
with temperature and chlorophyll a and 15%) (Fig. 6) There is also a broad
levels were calculated to asses their weight range in most of the samples
influenceonthereproductivecycle. (Fig. 7), with standard deviation
between23 and45%.
According to flesh dry
RESULTS weight-length ratio (FDW/L3 the
),
population showed low valúes during
Environmentalfactors summer and autumn, with an increase
The monthly temperature data from December to February. From
showed important fluctuations (Fig. 3), February, the flesh dry weight- length
with the máximum valué in the second ratio decreases until summer, with a
50
TIRADOETAL.: Reproduction ofDonaxtrunculusin thelittoral ofHuelva
ela -ñ- Ta
Figure 3. Sea water temperature and concentration ofchlorophyll a in seawater at the sampling
sitethroughtheyear.
Figura3. Temperatura delaguade maryconcentración declorofila a en elaguadelmaren elsitio de
muestreodurantetodoelaño.
Figure4. Relativefrequeney(%) ofsexesduringtheyearofstudy. F: females. M: males.
Figura4. Frecuenciarelativa (%)delossexosduranteelañodeestudio. F:hembras. M: machos.
Figure 5. Flesh dryweight (FDW)/ Length (L3) ratio duringtheyearofstudy. Bars showstandard
deviation.
Figure5. Relacióndepesosecodebiomasa (FDW)/Longitud(L3)duranteelañodeestudio. Lasbarras
muestranladesviaciónestándar.
51
,
Iberus 29 (1), 2011
Figure 6. Monthly mean length ofshells (L) during the year ofstudy. Bars show standard devia-
tion.
Figura 6. Media mensualdela longituddelasconchas (L) duranteelañodeestudio. Las barrasmues-
tranladesviaciónestándar.
Figure 7. Monthly mean flesh dry weight (DW) during the year ofstudy. Bars show standard
deviation.
Figura7. Mediamensualdelpesosecodebiomasa (DW)duranteelañodeestudio. Lasbarrasmuestran
ladesviaciónestándar.
Figure 8. Index ofcondition ofCrosby and Gale (CI): flesh dryweight x 1,000 / volume ofthe
internalcavityoftheshell, duringtheyearofstudy.
Figura 8. Lndicede condición de Crosbyy Gale (CL): Peso seco de la biomasa x 1000/volumen de la
cavidadinternadelaconcha, duranteelañodeestudio.
52
TIRADOETAL.: Reproduction ofDonaxtrunculusin thelittoral ofHuelva
Table I. Linearregressioncalculatedforeachsample. Lm: mean length; fleshdryweightforastan-
dardindividual; R2: coefficientofdetermination; R: coefficientofcorrelation; N: numberofspeci-
mens;W: monthlyfleshdryweightforastandardindividualof29 mm.
Tabla I. Regression linearcalculadapara cada muestra. Lm: longitudmedia; R2: coeficientededeter-
minación;L:coeficientedecorrelación;N:númerodeindividuos; W:pesosecodebiomasamensualpara
unindividuoestándarde29mm.
lm Regressionlines R2 R N W(L=29mm)
Jnl 31.22 y=2.3423x-1.1468 0.7171 0.8468 200 66.78
Jn2 31 y=2.2581x-1.0283 0.8105 0.9003 199 64.46
Jll 28.15 y=2.3057x-1.201 0.8062 0.8979 198 67.15
JI2 27.37 y=2.0405x-0.8224 0.7073 0.8410 200 58.35
Al 26.27 y=2.3454x-1.2257 0.8452 0.9193 199 66.79
A2 31.19 y=2.2428x-1.0357 0.7991 0.8939 197 64.00
SI 34.57 y=2.5491 -1.5168 0.4281 0.6543 202 72.41
S2 27.51 y=2.3769x-1.2753 0.9006 0.9490 201 67.65
0 27.81 y=2.6152x-1.6298 0.8392 0.9161 199 74.21
N 25.1 y=2.7123x-1.6903 0.8741 0.9349 200 76.97
D 25.40 y=2.701 x-1.7035 0.8329 0.9126 200 76.62
J 27.58 y=2.8042-1.7363 0.9229 0.9607 200 79.58
F 28.69 y=2.8714x-1.7802 0.9071 0.9524 200 81.49
Mrl 29.49 y=2.605x-1.3919 0.8814 0.9388 199 74.15
Mr2 28.62 y=2.8325x-1.7953 0.8816 0.9389 200 80.35
Api 27.52 y=2.785x-1.7727 0.862 0.9284 199 78.99
Ap2 29.43 y=2.3754x-1.2251 0.7727 0.8790 200 67.66
Myl 31.09 y=2.4862x-1.3195 0.7618 0.8728 202 70.78
My2 29.54 y=2.4818x-1.3567 0.8038 0.8965 199 70.62
small peak in May. The CI Índex FDW/L3 (r=0.541p<0.05) and with the
showed a similar pattern (Fig. 8). The FDW of the standard individual
most important decrease was recorded (tau=0.438, p<0.01). No other correla-
fromMarchtoApril. tionsweresignificant.
The monthly regression lines for
weight-length relationship are shown in Gametogenic cycle
Table I, and the monthly variation of The data from the histological study
flesh dry weight for a standard indivi- are presented in Figure 10. Activation of
dual (W) is represented in Figure 9. gonads started in January while the
According to these data the population regression began in the second half of
from Huelva had a relatively synchro- August with more than 66% of the
nous reproductive pattern, with 18 population in postactive and cytolized
samples (from a total of 19) explaining stages. InOctober, the whole population
70% of the variations of weight by the wasincytolizedstage.
length. The patternofthe standard indi- Duringthe activeperiod, thehistolo-
vidualwassimilartothatofCIÍndex. gical data showed continuous spaw-
According to the test ofKolmogorov ning, with percentages higher than 55%
Smirnov, only the temperature and from February to July with three peaks:
FDW/L3data showed a normal distri- first half ofApril (96.67%), June (100%)
bution. The coefficients of correlation of and second half ofJuly (96.67%), while
Pearson and Kendall have been calcula- only 13% oftheindividuáisattheendof
ted. According to these data, the tempe- August were spawning. Different stages
rature is inversely correlated with in the same gonad and new activation
53
Iberus, 29 (1), 2011
Figure9.VariationJnilnJfnl2eshJlldrJy12weAilghtA2inSaIstSa2ndaOrdNDonDaxtJruncFulMurslaMnri2maAlpi2A9p2mMmyllMoyn2g.
Figura 9. Variación delpeso seco biomasa en un animalestándarde Donax trunculus de29 mm de
C Pr HA A S Ps
Figure 10. Monthly cumulative frequency ofdifferent stages ofdevelopment ofthe gonads in D.
trunculus. C: cycolized; Pr: preactive; EA: earlyactive;A: active; S: spawning; Ps: postactive.
Figura 10. Frecuencia mensualacumulada de los diferentes estados dedesarrollo de lasgónadas en D.
trunculus. C:cicolizado;Pr:preactivo;EA:activotemprano;A:activo;S:enpuesta;Ps:postactivo.
without a total regression of the gonad Mouezaand Frenkiel-Renault 1973,
have been observed in many indivi- Tirado and Salas, 1998, Deval, 2009,
duáis. LaValle, 2006), but disagrees with the
TherestingperiodstartedinSeptem- results obtained in the neighbour popu-
berandfinishedinDecember.Atthebegin- lation of Southern Portugal, where
ning of this period, it was impossible to Gasparetal. (1999)foundahigherpro-
identifythesexof36%oftheindividuáis, portionofmalesinallsizeclasses.
andinOctoberalltheindividuáiswerein Accordingto the macroscopicidenti-
cytolized stage and it was impossible to ficationofthegonads,theactiveperiodis
identifythe sexof50% ofthesample. moreextensiveintheAtlanticpopulation,
inwhichitis possible to identify the sex
ofthewholepopulationfromFebruaryto
DISCUSSION theendofJuly(Fig3),whileintheMedi-
terranean population, the gonads are
Sexratio colouredinthewholesampleonlyinMay
The sex-ratio of the population of andJune. Percentagesofspecimenswith
Donax trunculus from Huelva agrees non coloured gonads higher than 70%
with observations of other authors wereobservedfromOctobertoFebruary
regarding this species (Lucas, 1965; (TiradoandSalas, 1998)
54
:
TIRADOETAL.: Reproduction ofDonaxtrunculusin thelittoral ofHuelva
Sexual cycle and Salas 1998 for D. trunculus in
Condition índex The wide range of Málaga;Gasparetal. 1999inD. truncu-
the standard deviation was partially lus in Faro (Portugal) Tirado and Salas,
related to the presence of different 1999 forD. venustus and Donaxsemistria-
stages of development of the gonads. tus orotherspecies, suchas Tapes rhom-
),
The data for the different condition boides (see Morvan and Ansell, 1988),
indexes of this Atlantic population Callista chione (see Tirado, Salas and
showed a long reproductive period, López, 2002) and Venus verrucosa (see
from December to September, very Tirado, Salas and Márquez, 2003).
similar to those found by Bayed (1990) This renewed activation of the gonad
in the Atlantic coast of Morocco and by seems to be at the origin of the fluctua-
Gaspar etal. 1999 in the South of Por- tions of the indexes of condition during
tugal, although in the latter there was a this period. After the most important
continuous decrease ofthe Índex ofcon- release of gametes at the beginning of
ditionfromFebruarytoAugust. spring, there was new but less intense
However, there are differences with spawning by the same individuáis in
the Mediterranean population of the same cycle. The occurrence of suc-
Málaga, in which the most important cessive individual spawnings has also
and continuous decrease of the Índex of been described in the population of the
condition was observed from April to AdriaticSea (Zeichenetal. 2002).
June, with an important increase inJuly. The most important drop of the
In the population from Huelva, the indexes of condition occurred between
major decrease was recorded from March and April, with 100% of the
March to April, with a slight increase in population in spawning, and after an
May, but with continuous decrease important increase of chlorophyll a in
duringthesummer. March. The strong regression of the
InTurkey, the population studied by gonad from September to October
Deval (2000)had a shorter reproductive (100% ofthe population in postactive or
period; the spawning occurred from cytolized stage) could be related to the
April to July with a peak between May strong decrease of the temperature
and June. This reproductive cycle is (9.5°C). An inverse correlation has been
coincidentwiththatofthepopulationof obtainedbetweentemperature and flesh
W
Málaga. The duration of the reproduc- dryweight (FDW/Land FD ofa stan-
tive period of the Turkish and Málaga dard individual). The availability of
populations was similar to thatfound in food in September at the same time as a
other Mediterranean populations máximum of clorophyll a could be
(Anselland Bodoy 1979 in Camargue, advantageous for the storage of reser-
French Mediterranean coast; Móueza ves, after an extensive spawning period.
and Frenkiel-Renault 1973 in This result is also described in theAlge-
Algeria), althoughthesewerenotcoinci- rian population (Moueza and Fren-
dent in time, due to differences in the kiel-Renault, 1973). On the otherhand,
environmentalvariables. the increase of chlorophyll a in March
Gametogenic cycle: The data obtained could be advantageous for the larva
point to continuous spawning for after the highest peak of spawning of
almost the whole population fromApril thepopulationfromMarchtoApril.
to August, coincident with the decrease According to the histological data,
of the índex of condition during this the MoroccanpopulationofD. trunculus
period. The coexistence of different have three months of resting period
stages in the same gonad, together with (Bayed, 1990), whereas in the popula-
a direct transformation from a postac- tion of Huelva there is only one month
tive stage to an active one without the (October). Moreover, the percentages of
intermedíate step of a cytolized stage, spawning in the population of Huelva
have been reported for other donacids are around 100%, whereas in the popu-
(De Villiers, 1975, for D. serva Tirado lation of Morocco the percentages never
;
55
Iberus, 29 (1), 2011
reach 50%. The data of the population showed a similar extensión ofthe repro-
from Faro (Portugal) are more similar to ductive cycleto thatofthepopulationof
those found in the population of Huelva, which lives in a dissipative
Huelva, although the whole population beach, but with an offset of three
is never in spawning (máximum 80% in months between the beginning of the
August, Gasparetal., 1999). spawning period in each population.
According to Schlacher et al. These results justify the necessity of
(2008) and Brown and McLachlan taking into account the biology of the
(2006) the populations from dissipative species in a particular area for a better
beaches have a more extensive repro- management of the resources by ruling
ductive cycle than those from reflective different cióse seasons for the Atlantic
ones. However, our data on the repro- and the Mediterranean populations,
duction of D. trunculus from the littoral from March to April in the Atlantic
of Málaga, collected in reflective populations and from May to June in
beaches (Tirado and Salas, 1998) theMediterraneanones.
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