Shell morphology and relative growth variability of the invasive pearl oyster Pinctada radiata in coastal Tunisia

Abstract

The variability of shell morphology and relative growth of the invasive pearl oyster Pinctada radiata was studied within and among ten populations from coastal Tunisia using discriminant tests. Therefore, 12 morphological characters were examined and 34 metric and weight ratios were defined. In addition to the classic morphological characters, populations were compared by the thickness of the nacreous layer. Results of Duncan's multiple comparison test showed that the most discriminative ratios were the width of nacreous layer of right valve to the inflation of shell, the hinge line length to the maximum width of shell and the nacre thickness to the maximum width of shell. The analysis of variance revealed an important inter-population morphological variability. Both multidimensional scaling analysis and the squared Mahalanobis distances (D2) of metric ratios divided Tunisian P. radiata populations into four biogeographical groupings: the north coast (La Marsa); harbours (Hammamet, Monastir and Zarzis); the Gulf of Gabès (Sfax, Kerkennah Island, Maharès, Skhira and Djerba) and the intertidal area (Ajim). However, the Kerkennah Island population was discriminated by the squared Mahalanobis distances (D2) of weight ratios in an isolated group suggesting particular trophic conditions in this area. The allometric study revealed high linear correlation between shell morphological characters and differences in allometric growth among P. radiata populations. Unlike the morphological discrimination, allometric differentiation shows no clear geographical distinction. This study revealed that the pearl oyster P. radiata exhibited considerable phenotypic plasticity related to differences of environmental and/or ecological conditions along Tunisian coasts and highlighted the discriminative character of the nacreous layer thickness parameter.

Comparison of the Dynamics between Coastal and Midshore Populations of Pinctada radiata (Leach, 1814) (Mollusca: Bivalvia) in the Gulf of Gabes, Tunisia

“…These variations in the morphometric relationships between localities can be related to environmental factors such as depth and sediment type. For example, Bellaaj-Zouari, Dkhili, Gharsalli, Derbali, and Aloui-Bejaoui (2012) showed that low tides marks might affect the morphology of P. radiata individuals.…”

Nacre, a natural, multi‐use, and timely biomaterial for bone graft substitution

“…The largest P. margaritifera shells can reach 30 cm in diameter, versus 20–25 cm for P. maxima . The thickness of the P. maxima nacre layer can be up to 2 cm . These parameters endow nacre with great potential to design bone graft substitutes.…”

“…The thickness of the P. maxima nacre layer can be up to 2 cm. 10 These parameters endow nacre with great potential to design bone graft substitutes. At the microscopic scale, nacre is composed of aragonite crystal tablets covered by and embedded in an organic matrix.…”

Morphometric aspects and growth modeling of exotic bivalve blood cockle Scapharca inaequivalvis from the Black Sea, Turkey

“…However, environmental and ecological factors can lead to morphological variations in individuals of the same species that live in different ecosystems (Bellaaj-Zouari et al 2012). This situation is particularly important for species that have a high ecologic tolerance like invasive species.…”