Description of two new species of freshwater Gammarus Fabricius, 1775 (Amphipoda: Gammaridae) from the Middle Atlas of Morocco

This study describes, both morphologically and molecularly, two new species, Gammarus latispinus sp. nov. and G. tazekkaensis sp. nov. from the Middle Atlas of Morocco. Both species are similar to Gammarus acalceolatus, but differ by having setae as long as, or longer than, the diameter of the article on the second antenna, lacking calceoli, and by the absence of long setae on merus and carpus of pereopods 5–7. Gammarus latispinus sp. nov. is characterized by the presence of spinules on the outer face of epimeral plates 2 and 3, a pereopod 5 much shorter than pereopods 6 and 7, and telson lobes with dorsal setae but without lateral spines. Gammarus tazekkaensis sp. nov. is also characterized by the presence of a single lateral spine on telson lobes. Full descriptions of the new species are provided in this paper together with molecular data (genes COI and 28S) that corroborate the molecular delimitation. The two new species are phylogenetically close to G. acalceolatus, followed by G. marmouchensis and G. rifatlensis, all of which inhabit the Middle Atlas Mountains in Morocco.