Corrosella

Boulaassafer, Khadija, Ghamizi, Mohamed, Machordom, Annie, Albrecht, Christian & Delicado, Diana, 2021, Hidden species diversity of Corrosella Boeters, 1970 (Caenogastropoda: Truncatelloidea) in the Moroccan Atlas reveals the ancient biogeographic link between North Africa and Iberia, Organisms Diversity & Evolution (New York, N. Y.) 21 (2), pp. 393-420 : 414-416

Diversity of Corrosella in Morocco

Our morphological and genetic findings confirm the presence of the hydrobiid genus Corrosella in western Maghreb and extend its geographic range from the Iberian Peninsula and south of France ( Boeters, 1970, 1984, 1988, 1999; Boeters microsculpture of protoconch, g inner and h outer sides of operculum; i–k radulae: i portion of radular ribbon, j central tooth of radula, k outer marginal teeth et al. 2015; Delicado et al. 2012, 2013; Delicado and Ramos 2012; Talaván Serna and Talaván Gómez 2019) to the central and northern regions of Morocco. This study also reveals the occurrence of six monophyletic groups of diagnosable Moroccan populations proposed here as distinct species. The species Hydrobia marocana and Pseudamnicola pallaryi , collected from their respective type localities, are here recognized as Corrosella along with four other unknown new species. The six Moroccan congeners feature the following diagnostic characters for Corrosella : an ovate-conic and often eroded shell; a pair of basal cusps on the central radular tooth; a pigmented renal oviduct; an elongate or pyriform bursa copulatrix with a long duct; one seminal receptacle; a simple and gradually tapering penis showing different pigment patches on different areas and folds on its inner side; and a pigmented nervous system. These findings raise the known biodiversity of this genus to 24 species and the number of genera of Hydrobiidae sensu stricto in Morocco to 13 (i.e. Corrosella , Mercuria ( Boulaassafer et al. 2018; Glöer et al. 2015), Pseudamnicola ( Boulaassafer et al. 2020; Ghamizi et al. 1997), Islamia Radoman, 1973 and Aghbalia Glöer et al., 2020a ( Glöer et al. 2020a), Ifrania Glöer et al., 2020b and Fessia Glöer et al., 2020b ( Glöer et al. 2020b), Heideella Backhuys and Boeters, 1974 ( Bodon et al. 1999), Atebbania Ghamizi et al., 1999 ( Ghamizi et al. 1999), Ecrobia Stimpson, 1865 —as Hydrobia ( Van Damme 1984) —( Ghamizi et al. 2020), Peringia Stimpson, 1865 (Wilke and Pfenninger 2002) and Rifia (Ghamizi 2020)) . Hence, Corrosella now enters the list of mollusc genera with representatives in both the and seminal receptacle; f–g male genitalia: f head with penis, g prostate gland

Iberian Peninsula and North Africa. Further examples are the hydrobiid genera Mercuria ( Boulaassafer et al. 2018; Glöer et al. 2015) and Pseudamnicola ( Boulaassafer et al. 2020) and other freshwater genera such as Theodoxus ( Sands et al. 2019) , Ancylus Müller, 1773 ( Albrecht et al. 2006), Melanopsis ( Neubauer et al. 2016) , Unio Philipsson, 1788 ( Araujo et al. 2017; Froufe et al. 2016a), Potomida Swainson, 1840 ( Froufe et al. 2016b) and Pseudunio Haas, 1910 ( Lopes-Lima et al. 2018; Sousa et al. 2019). However, most of these taxa show broader geographic ranges than Corrosella , and their species are found in a wider range of habitat types. In both Morocco and the Iberian Peninsula, Corrosella species typically live in upland headwater habitats except for the species C. marocana , which has been found in a lowland spring. Our field surveys indicate the first cooccurrence of Corrosella with its closely related genus Pseudamnicola (e.g. C. mahouchii sp. nov. and P. leprevieri in Tizerdiouin Spring, Timdghasse and C. nechadae sp. nov. and P. ramosae in Tadoute Spring).

Like their Iberian congeners (Delicado et al. 2012, 2013; Delicado and Ramos 2012), the Moroccan Corrosella species show low intraspecific variation in morphology and genetic divergence and are locally endemic. However, morphological differences in shell and reproductive organs are more pronounced between Moroccan sister species than between the Iberian ones (note the constant trend in morphological disparity observed through time between Iberian species in Delicado et al. 2018). In contrast, mean uncorrected sequence divergences between the Moroccan species (i.e. 4.3–9% for COI, 1–3.2% for 16S and 0.1–1.2% for 28S) were slightly lower than those estimated in Delicado et al. (2013) for the Iberian representatives (i.e. 5.3–12% COI, 1.7–8.6% 16S and 0–0.9 % 28S). However, the genetic divergence found between the Moroccan Corrosella species is higher than that estimated for other hydrobiid species from the same region, which often feature different ecological patterns (e.g. the lowland and more geographically extended species of Mercuria and Pseudamnicola ; Boulaassafer et al. 2018, 2020). This strong divergence between Corrosella species in combination with their narrow geographical ranges suggest that the Atlas Mountains probably acted as a refugium for these snails during the Pleistocene glaciations, thus confirming the importance of this region as a reservoir of biodiversity ( Husemann et al. 2014).