Alburnus arborella, , Bonaparte, 1841

Alexander, Timothy & Seehausen, Ole, 2021, Diversity, distribution and community composition of fish in perialpine lakes – “ Projet Lac ” synthesis report, Eawag: Swiss Federal Institute of Aquatic Science and Technology : 126

Alburnus arborella

has unfortunately become very rare in Lake Lugano. Only two individuals were caught in Projet Lac ( Figure 38 ). One was a large (115 mm TL) individual of typical appearance with the high count of lateral line scales that Buj et al. [146] describe for A. maxima . The second was of very different appearance, and could not be assigned to A. arborella , A. maxima or A. alburnus . The COI gene (barcode) was sequenced for both fish. They were separated by several mutations, falling into two distinct subclades within samples currently considered A. arborella . The identity and diversity of Alburnus from Lake Lugano should urgently be investigated. Our unquantified impression is that the phenotype that corresponds to A. maxima is shared with Lake Maggiore whereas the other kind seems to resemble Alburnus from Lake Garda.

A second unusual observation in Alburnus requires reporting here: we noticed a previously undocumented phenotypic and ecological polymorphism of Alburnus alburnus in Lake Brienz. In this lake, we observed considerable variation in shape: on one hand fish with very long snouts, and on the other hand, blunt-snouted fish that resemble Alburnus alburnus from other lakes ( Figure 39 ). The long-snouted type was commonly caught near the surface whereas the blunt-snouted type could be caught near the surface or in considerable depths down to 20 m.

Figures

Figure 38: Examples of Scardinius spp caught in Projet Lac. Upper panel are northern S. erythrophthalmus caught in their native lakes. Upper middle panel are southern S. hesperidicus from their native southern perialpine lakes. Lower middle panel are S. hesperidicus from northern perialpine lakes. Bottom panel are a phenotypic hybrid from Chalain and a backcross hybrid from Zurich, i.e. a phenotypic S. erythrophthalmus that carried S. hesperidicus mitochondrial DNA. * indicates that the identity was confirmed by DNA barcoding.

Figure 39: Alburnus from lakes Brienz and Lugano.The two individuals top left and middle left were caught in Lake Brienz and represent the form of Alburnus alburnus with elongated head and long snout, the fish top right and middle right are also from Brienz and are representative of the blunt-snouted form resembling Alburnus alburnus from other lakes. Bottom left: Alburnus arborella from Lake Lugano.This fish corresponds meristically to A. maxima. Bottom right: unidentified Alburnus from Lake Lugano.This fish does not correspond meristically to A. maxima, nor to A. arborella.