9th International Conference on Shellfish Restoration November 15–19, 2006 - Charleston, South Carolina, USA MORPHOLOGICAL COMPARISON BETWEEN GEOGRAPHICALLY DISTANT POPULATIONS OF THE PEARL OYSTER PINCTADA RADIATA INVADING THE EASTERN MEDITERRANEAN SEA Aloui-Bejaoui, N. (1), E. Soufi (1), Zenetos A (2), A. Dosi (2), I. Ammar (3), and A. Ibrahim (3), (1(1) ) Institut National Agronomique de Tunisie- 43, Avenue Charles Nicolle, 1082 Tunis, TUNISIA (2(2) ) Hellenic Centre for Marine Research, Institute Oceanography, P.O. Box 712, Anavissos 19013, GREECE, (3(3) ) High Institute of Marine Research, Tishreen University, P.O. Box 2242, Lattakia, SYRIA INTRODUCTION RESULTS Comparison of morphological parameters with the use of statistical tests and Box and Whisker Plot : Pinctada radiata is a bivalve mollusc originating from the Indo-Pacific and the Red Sea (Oliverio and al., 1992). Following the opening of the Suez Canal, P. radiata has entered the far eastern Mediterranean. In addition, the species, being of commercial value (pearl oyster), has been imported for mariculture in other areas such as Greece and Italy. Up to date it has been recorded as common in the eastern Mediterranean with sporadic Box-and-Whisker Plot Box-and-Whisker Plot Box-and-Whis ker Plot Box-and-Whisker Plot Box-and-Whisker Plot 100 100 40 80 60 occurrences in the western basin (Zenetos & al., 2003). 80 50 80 30 60 40 60 60 20 40 30 40 40 The species’ mode of introduction in the areas beyond those of the Levantine basin, where Pinctada has progressively penetrated (Lessepsian 20 10 20 HeightHeight (mm) (mm) 20 WidthWidth (mm) (mm) 20 ThicknessThickness (mm) (mm) 10 Total Wet Wt WtTotalTotal Wet Wet (g) (g) migration), remains unknown. For example, the recent records in Greek waters correspond to areas where the species was intentionally introduced for DorsalDorsal Side Side (mm) (mm) 0 0 0 0 0 marine farming (Serbetis, 1963). In addition, its presence in areas with major harbours indicates that shipping may be a alternative mode of introduction SA1 KER LAT ROD SA2 SA1 KER LAT ROD SA2 SA1 KER LAT ROD SA2 SA1 KER LAT ROD SA2 KER LAT ROD SA2 Station Station Station Station Station (www.ciesm.org/atlas/). This study is a first approach towards investigation of the mode of introduction in the Mediterranean populations along an east-west transect. The aim The Kruskal-Wallis Test of the Medians results in significant difference amongst the populations for the Height (Test of the study is to know : statistic=162,78, P-value <0,001), the width (Test statistic=164,14, P-value <0,001 ), the thickness (Test statistic=203,98, P-value •Are there differences between the populations in the different areas in these countries? <0,001), the dorsal side (Test statistic=132,77, P-value <0,001) and the total weight (Test statistic=138,35, P-value <0,001) at the 95% confidence interval . •Are there population differences between the three countries? The Student T-test as well as the Box and Whisker Plot indicates that animals from Saronikos Gulf (SA1) present the: - higher values for height followed by the ROD , SA2 and LAT populations. KER present the lowest values. - greater values for width, as it was observed for height, and animals from Tunisia (KER) the lowest. - higher values for thickness followed by the LAT, ROD and SA2 populations which seem not to differ significantly and MATERIAL AND STUDY AREAS at the end again the KER population presents the lowest values. P. radiata from Tunisia (KER) present significant differences (p<0,001) from all the other sites and have the lowest values for Lat Individuals were collected from 5 different sites. Three prominent total weight. At the other end, animals from Saronikos Gulf (SA2) (weight measurements from SA1 were not available) have the established populations of Pinctada radiata have been selected from Greece: greater values. SA2 population is significantly different from all other sites except Rodos (ROD). the populations of Rodos (ROD) and Saronikos Bay (SA1, SA2), one population from Tunisia Kerkennah islands (KER) and one from Syria, C= convexity = thickness / Height Lattakia area (LAT). Sampling was carried out by diving. 0,5 0,366 - Convexity in SA1, SA2 and LAT present the higher values. Pinctada radiata in ROD and 0,350 0,367 0,303 0,4 0,295 0,3 KER is the less convex. Rho 0,2 0,1 -The variations of Dorsal Side are not statistically linked to the other morphologic 0 For this study 100 specimens per population were collected and LAT KER SA2 SA1 ROD parameters. DS is a parameter highly influenced by the ecological conditions. The examined morphologically using standard biometric techniques. variations of this parameter are significant for only a couple of sites: SA1 and KER. The Measurements were carried out using precise instruments : electronic R = He ig ht / DS first site presents the more important value of R whereas KER, as for the other parameters, digital calliper at 0.01mm precision and electronic scale at 0.01g precision. 2 1,463 presents the lowest one. This indicates an almost equal increase for the two parameters in Ker 1,267 1,286 1,313 Five morphological parameters were considered with the object to 1,5 1,167 1 the Tunisian population while at the other sites height has a faster growth rate than DS. compare the five sites : 0,5 0 - Height H LAT KER SA2 SA1 ROD The more important total weight of a 50 mm height standard animal is observed in SA2 and - Width W LAT and the lowest one in KER. All the results confirm a better relative growth of the Total w eight (g) standard animal 50 mm Height - Thickness T populations of Saronikos Gulf (height and width). The total weight in SA2 is more important 25 - Total weight (except for site SA1) 20,218 20,166 than in the other populations. The population of KER presents the lowest values. The T H The Kruskal-Wallis test tests the null hypothesis that the medians 20 17,545 14,132 population of LAT presents a good development in total weight, comparatively to its metric - Dorsal side (DS) of one parameter within each of the 5 levels of Station are the 15 10 growth. Among the three populations of Greece, ROD is the one that presents the less good DS same. The data from all the levels is first combined and ranked from smallest to largest. The average rank is then computed for 5 growth in terms of height and total weight. This population shows a shape which develops W 0 more in width. the data at each level. Since the P-value is less than 0,05, there is SA2 LAT KER ROD The analysis concerns: a statistically significant difference amongst the medians at the Bubble Chart for DS Bubble Chart for DS 1- Comparison of morphological parameters with the use of 95,0% confidence level. The Box-and-Whisker Plot determine 100 Station 100 Station SA1 SA1 statistical tests (Kruskal-Wallis test ). which medians are significantly different from which others. 80 KER 80 KER LAT LAT 60 ROD 60 ROD SA2 SA2 2- Comparison of C and R coefficients according to Hynd (1955) 40 40 These differences are also obvious on the following graphs: WiWi dt dt h h ( ( mm) mm) The equations of the regression lines have permitted to calculate HeightHeight (mm) (mm) 20 20 3- Study of the relative growth parameters (Dagnélie, 1982; Box 0 0 the theoric values of weight after having fixed the value of the 0 10203040 010203040 and Cox,1982) in each population using allometric tests Thickness (mm) Thickness (mm) metric parameters of the individuals belonging to the different (regression lines) populations (standard animal). This value has been fixed in a way it 4- Analysis of morphological parameters’ variation based on the could be the nearest possible of the means calculated refering to Dendrogram To summarize the results and visualize better the differences between sites Furthest Neighbor Method,Euclidean use of a standard animal (Aloui-Bejaoui &. al., 2003). the different populations : H=50 mm 6 we performed a Euclidean clustering method for all measured parameters 5 except Total Wet Weight. The produced dendrogram suggests that the SA1 4 population is completely different from all the others which form two 3 subgroups, the Greek sites together (SA2 and ROD) and the Syrian and DistanceDistance 2 1 Tunisian (LAT and KER) on the other subgroup. 0 SA1 SA1 SA2 SA2 RODROD LATLAT KER KER CONCLUSION There is no differences observed according to an east-west transect. Pinctada radiata is adapting to its new environmental conditions in spite of the geographic distance from its native area. Saronikos Gulf (Greece) population have the greater values and animals from Kerkennah Islands (Tunisia) present significant differences from all the other sites and have the lowest values in all parameters measured. It is assumed that environmental parameters are responsible for the observed morphometrical differences and shell morphology of Pinctada radiata has been shown to vary especially with salinity (Al Sayed & al., 1997). In Tunisia, the thermic conditions are very favorable and enable high fecundities of Pinctada radiata (Zouari and Zaouali,1994 ), just like for the other bivalves. This situation leads to different modalities of growth. References • Aloui - Bejaoui N., M. Le Pennec, S. Rezgui & F. Maamouri, 2003 –Influence du cycle de reproduction et des conditions du milieu sur la croissance pondérale de Mytilus galloprovincialis basée sur l’utilisation d’un animal standard. Marine life, 12 (1-2): 47-57 • Hynd J.S., 1955 – A revision of Australian pearl –shells, genus Pinctada (Lamellibranchia) – Australian journal of marine and freshwater research, vol 6 n°1 : 98-132.