Morphometric Differentiation between Two Closely Related Achatinid Snails (Gastropoda: Achatinidae) of West Africa and Implications for the Conservation of <i>Achatina togoensis</i>(Bequaert &Clench, 1934)

Achatina togoensis is a giant land snail taxa endemic to the northern sectors of the Monts Togo, which has been regarded as full species or subspecies of the highly variable, widespread A. achatina (L.). To address this issue, samples of snails were taken throughout the distribution range of the two taxa in the Dahomey Gap (West Africa) and separated into 112 A. achatina and 141 A. togoensis according to color of the columella and parietal wall. Radulae were compared and shell characters of these 2 species were evaluated through the traditional morphometric method. The results indicate that the species cannot be distinguished by overall shell size and radular morphology, but they exhibit significant differences in shell shape and meristic traits. The typical A. achatina with vinaceous-red columella has a low-spired shell and an expanded aperture (globose shape) whereas A. togoensis has a higher-spired and smaller aperture (a fusiform shape). We suggest that local environmental effects are probably the causes of morphological divergence between the two taxa. It is likely that peripheral populations of the typical form of A. achatina would have isolated and developed in the drier facies of the humid forest that individualized in the northern sector of the mountains after the arid or interpluvial period of Holocene. In addition, we find that A. togoensis meets the criteria B2ab (ii, iii) to categorize as “Endangered”. However, whether this latter should be considered as separate species cannot be decided at the current state of knowledge.

Planaxidae(Mollusca, Gastropoda) from the South China Sea

Abstract Planaxidae is a family of tropical and subtropical marine gastropods that are adapted to an intertidal, rocky environment. The present study deals with three species in the family Planaxidae from the South China Sea： Planaxis sulcatus （von Born, 1778）, Angiola longispira （Smith, 1872）, and Supplanaxis niger （Quoy and Gaimard, 1833）, based on specimens deposited in the Marine Biodiversity Collections of the South China Sea, Chinese Academy of Sciences. The taxonomic status, main morphological characteristics of the shell and radula, distribution, and habitat of these three planaxid species are presented. We also briefly discuss their morphological differences and the biogeographic distribution.

Age,growth and length-weight relationship of the rough skate,Raja radula(Linnaeus,1758)(Chondrichthyans:Rajidae),from the Gulf of Gabes(Tunisia,Central Mediterranean)

Objective:To investigate the length distribution,sex ratio,length-weight relationship,age and growth of Raja radula in the Gulf of Gabes.Methods:The age and growth characteristic of the rough skate(Raja radula)inhabiting in the Gulf of Gabes(Central Mediterranean Sea)was determined.A total of 1250 specimens were sampled.According to the marginal increment band its growth was annual.Results:The growth parameters were derived by using the von-Bertalanffy method and were separately evaluated as follows:TL∞=97.2 cm,K=0.15 y^(-1),t_(o)=0.35,and W_(∞)=5.28 kg,and TL∞=76.4 cm,K=0.22 y^(-1),to=0.16,and W∞=3.77 kg,for females and males respetively.The maximum age was 12 years for females and 10 years for males.Conclusions:Results from this research will provide a starting point to develop a management plan for the rough skate in the Gulf of Gabes.Further investigations are necessary to quantify the impact of the existing regulations on the population dynamics and recruitment patterns of this species in the region.