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

123 European Journal of Taxonomy 1026: 123–146 https://doi.org/10.5852/ejt.2025.1026.3109 europeanjournaloftaxonomy.eu ISSN 2118-9773 2025 · Piscart C. et al. This work is licensed under a Creative Commons Attribution License (CC BY 4.0) Received: 9 June 2025 • Accepted: 17 September 2025 • Published: 14 November 2025 Topic editor: Magalie Castelin • Section editor: Fabio Stoch • Desk editor: Eva-Maria Levermann Research article urn:lsid:zoobank.org:pub:F68720AB-CDEA-4CBD-A270-29CBC267D90A Description of two new species of freshwater Gammarus Fabricius, 1775 (Amphipoda: Gammaridae) from the Middle Atlas of Morocco Christophe PISCART 1,*  , Youness MABROUKI 2  & Fouzi A. TAYBI 3  1 University of Rennes, CNRS, ECOBIO – UMR 6553, F-35000, Rennes, France. 2 Sidi Mohamed Ben Abdellah University, Faculty of Sciences, Dhar El Mehraz, Laboratory of Biotechnology, Conservation and Valorization of Bioresources, Fes Morocco. 3 Mohammed First University, Multidisciplinary Faculty of Nador, Applied Biology and Biotechnology Research Team, Morocco. * Corresponding author: [email protected] 2 Email: [email protected] 3 Email: [email protected] Abstract. 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. Keywords. Amphipoda, integrative taxonomy, Gammarus latispinus sp. nov., Gammarus tazekkaensis sp. nov., North Africa. Piscart C., Mabrouki Y. & Taybi F.A. 2025. Description of two new species of freshwater Gammarus Fabricius, 1775 (Amphipoda: Gammaridae) from the Middle Atlas of Morocco. European Journal of Taxonomy 1026: 123– 146. https://doi.org/10.5852/ejt.2025.1026.3109 Introduction The Mediterranean Basin harbours 35% of the Palearctic freshwater fauna and more than 6% of the world freshwater biodiversity with a very high rate of endemic species (Tierno de Figueroa et al. 2013; European Journal of Taxonomy 1026: 123–146 (2025) 124 Maasri & Bonada 2024). This is particularly true for freshwater Malacostraca Latreille, 1802 for which the Mediterranean species represent 18% of the world freshwater species known and up to one-third of the world known species of almost all orders (Piscart et al. 2024). AmongMediterraneanMalacostraca,AmphipodaLatreille,1816isthemostdiversifiedorderwith 581species,mostofthembeingknownfromthenorthernpartoftheMediterraneanSea.Afirstevident explanation to consider in studying the diversity of aquatic fauna in Northern Africa is the limitation of the water resources during the last 6000 years (Schneider et al. 2017). Indeed, unlike insects, which have aflyingadultstagethatallowsthemtoescapedroughtevents,crustaceanshaveanentirelyaquaticlife cycle, and they are also particularly threatened by climate change (Dehedin et al. 2013a, 2013b; Aspin et al. 2019). Another important factor contributing to the lower species richness in North Africa may be the lack of knowledge on amphipods (Tuekam Kayo et al. 2012; Ayati et al. 2019). Africa remains largely unexplored with respect to the aquatic fauna, especially crustaceans, and Amphipoda is one of the least knowntaxonomicgroups,with20%ofthecurrentlyknownspeciesdescribedinthelast15years(Arfianti et al. 2018). As a consequence, knowledge on freshwater amphipods is rather limited in Northern Africa, with only 23 epigean freshwater species currently known (Ayati et al. 2019; Hadjab et al. 2021). Half of the species are known from Morocco, which harbours the seven species of the genus Gammarus Fabricius, 1775, all of them, except G. gauthieri (Karaman, 1935), being endemic (Ayati et al. 2019). Samplings in the northern part of Morocco yielded gammarid populations morphologically close to G. acalceolatus Pinkster, 1970, a species already known from the Northern part of Morocco (Karaman & Pinkster 1977). However, several morphological traits did not fully match, and molecular analyses confirmedtheirevolutionarydivergence.Bothofthesespeciesaredescribedinthispaper. Material and methods Field surveys and animal collection Several locations were sampled in the northern part of Morocco, including the Atlas Massif. Invertebrate fauna, including Gammaridae Latreille, 1802, was collected at 31 sites using a handnet and a Surber sampler (20 ×25cmsurfacearea,400μmmesh)duringseveralseasonsbetween2019and2023(Fig.1). Sampleswerepreservedin96%ethanoluntilidentification.Inaddition,somesampleswerecollectedat type localities / area of several species of Gammarus in Morocco for molecular analyses. DNA extracts from specimens collected at each sampling site were stored in the private collection of Christophe Piscart, University of Rennes (France). Conductivity, pH, dissolved oxygen, and temperature were measured in situ with a multiparametric measuring device (WTW, MultiLine P4). Biological oxygen demand after 5 days (BOD5) and ammonium (N-NH4) were measured in the laboratory. Institutional abbreviations MNHN = Muséum national d'Histoire naturelle, Paris, France Molecular analyses Total genomic DNA was extracted from individuals using NucleoSpin Tissue Kits (Macherey-Nagel™) followingthemanufacturer’sinstructions(Düren,Germany).DNAwasamplifiedwithprimerstargeting the mitochondrial cytochrome oxidase subunit I (COI) and nuclear 28S genes. We used the primer set LCO1490 and HCO2198 (Folmer et al. 1994) to amplify the COI gene; NIPH15 / NIPH16 (Verovnik et al. 2005) and 28F / 28R (Hou et al. 2007) to amplify a fragment of the 28S gene. PCR were performed Quotation marks “Verbatim quotation” (e.g., for label citations) ʻEmphasisʼ(e.g.,intheEtymologysection) somebody’s 5°4′16″S,38°24′16″E PISCART C. et al., On two new species of Gammarus (Amphipoda: Gammaridae) from Morocco 125 inafinalvolumeof27μlcontaining12μlofPCRwater,10μlofType-itPCRMasterMix(©Qiagen, Germany),and1.5μlofeachprimer(5μM)and2μL of DNA extracts. The success of the PCR reactions was checked by gel electrophoresis. The PCR products were then purifiedandsequencedinbothdirectionsbytheEurofinssequencingfacilityorwithanApplied Biosystem 3130 XL sequencer in the DNA sequencing facility of the Institute of Genetics and Development of the University of Rennes (https://igdr.univ-rennes.fr/en). Sequences of the new species were submitted to GenBank with Additional DNA sequences of closely related species of Morocco (accession number in Table 1). Then, all sequences were aligned with MUSCLE (Edgar 2004) as implemented in Seaview ver. 5.05 (Gouy et al. 2010). Alignments were then checked by eye and minor editing was done manually. To assess divergence from other previously described and sequenced species of Gammarus, we calculated corrected genetic distances using the Kimura two-parameter (K2P) model and used the Assemble Species by Automatic Partitioning (ASAP) method to check species delimitation (Puillandre et al. 2021) implemented in iTAXOTOOLS ver. 0.1 (Vences et al. 2024), for COI with a transition / transversion ratio (R) of 0.592 calculated in SeaView software. ASAP was run using p-distances as well as both the JukesCantor (JC69) and the Kimura 2-parameter (K2P) substitution models to compute the distances, allowing us to investigate the possible impact of different distance models on the partitioning. In addition, we used the Bayesian Poisson Tree Processes (Zhang et al. 2013). Current approaches either rely on simple sequence similarity thresholds (OTU-picking as a tree-based method to identify the Molecular Operational Taxonomic Units (MOTUs) based on the COI dataset for each species. The appropriate nucleotide substitution models were selected on the www.phylogeny.fr webserver under a HKY85 model of evolution. A neighbour-joining (NJ) tree was then constructed with HKY85 node Fig. 1. Location of the species of Gammarus Fabricius, 1775 sampled in the study area in Morocco. European Journal of Taxonomy 1026: 123–146 (2025) 126 support, which was calculated (Hasegawa et al. 1985) using 1000 bootstrap pseudo-replicates. The resulting tree was analysed using the iTAXOTOOLS executable. A Neighbour-Joining (NJ) tree of all sequences was built in Seaview ver. 5.05 based on the K2P-distance matrix with both transitions and transversions included and all positions with gaps or missing data removed (Saitou & Nei 1987). The node support was inferred with a bootstrap analysis using 1000 bootstrap pseudo-replicates (Felsenstein 1985). The molecular sequences of another G. maroccanus Fadil & Dakki, 2001, also present in Morocco but member of a sister clade of other species used in the tree, were used as outgroup. Species Locality Assession numbers References COI 28S G. gauthieri (S. Karaman, 1935) Fès (Mo) JF965899.1 JF965710.1 Hou et al. 2011 G. cf ibericus Margalef, 1951 Lascaux (Fr) JF965901.1 JF965713.1 Hou et al. 2011 G. acalceolatus Pinkster, 1970 Timahdite (Mo)JF965831.1 JF965636.1 Hou et al. 2011 G. acalceolatus Debdou (Mo) PV657838 PV658258 this study G. marmouchensis* Fadil & Dakki, 2006 Imouzzer (Mo) PV657834 PV658255 this study G. marmouchensis*Imouzzer (Mo) PV657835 PV658256 this study G. maroccanus* Fadil & Dakki, 2006 Ain Chkef (Mo) PV657841 PV658261 this study G. maroccanus*Ain Chkef (Mo) PV657842 PV658262 this study G. latispinus* sp. nov. Sidi El Makhfi (Mo) PV657836 PV658257 this study G. latispinus* sp. nov. Sidi El Makhfi (Mo) PV657837 – this study G. rifatlensis* Fadil & Dakki, 2006 Bouadel (Mo) PV657832 PV658253 this study G. rifatlensis*Bouadel (Mo) PV657833 PV658254 this study G. tazekkaensis sp. nov.* Bab Boudir (Mo) PV657839 PV658259 this study G. tazekkaensis sp. nov.* Bab Boudir (Mo) PV657840 PV658260 this study Table 1. Information about data on the species of Gammarus Fabricius, 1775 used in molecular analyses. Abbreviations: Fr = France; Mo = Morocco; * = type locality. PISCART C. et al., On two new species of Gammarus (Amphipoda: Gammaridae) from Morocco 127 Morphological description The habitus of the amphipods was studied in glycerine under a stereo microscope and slides were prepared using Reyne’s permanent mounting medium (Stock & Von Vaupel Klein 1996) after maceration of the material in lactic acid (4 h) and a digestion in KOH (10%) overnight before staining with pink lignin (4 h). Body parts were carefully dissected and were drawn using a Wacom tablet and the Illustrator software package (AdobeTM). Results Molecular analysis Whether ASAP or bPTP, both approaches delineated 8 MOTUs that correspond to singletons in the NJ tree (Fig. 2A). ASAP analyses consistently suggested the same partitioning into 8 different MOTUs (p-values > 0.1), regardless of the distance estimation method (p-distances, JC69, K2P). K2P distances between MOTUs ranged from 12.9% (between MOTUs associated to the two species Gammarus acalceolatus and G. tazekkaensis sp. nov.) to 26.5% (between Gammarus cf. ibericus Margalef, 1951 and G. maroccanus). The new MOTUs are close to the MOTU associated with G. acalceolatus, with a distance of 12.9% for G. tazekkaensis sp. nov. and 14.9% with G. latispinus sp. nov. This partition was also strongly supported by the bPTP delimitation method applied to the COI phylogeny. Fig. 2. Phylogenetic relationships of some species of Gammarus Fabricius, 1775. A. Reconstructed with the NJ method based on COI. B. Reconstructed with the NJ method based on 28S genes. Numbers between brackets indicate the bootstrap result and other numbers indicate the K2P distances. Green and blueboxeshighlighttheoptimalspeciespartitionsidentifiedwithASAPandbPTPdelimitationmethods applied to the COI gene. European Journal of Taxonomy 1026: 123–146 (2025) 128 Inaddition,resultsobtainedwiththeCOIgenewereconfirmedusingthe28Sgene,forwhichtheK2P distances between Gammarus acalceolatus and Gammarus tazekkaensis sp. nov. was 1.3%, and between G. acalceolatus and G. latispinus sp. nov. was 2.4% (Fig 2B). Taxonomy Order Amphipoda Latreille, 1816 Family Gammaridae Latreille, 1802 Genus Gammarus Fabricius, 1775 Gammarus latispinus sp. nov. urn:lsid:zoobank.org:act:56EBA8F0-07F7-49CE-99B7-E724D9CF8F01 Figs 1–8, Tables 1–2 Diagnosis A relatively large-sized species of the Gammarus with epimeral plate 2 with 1–3 spinules on the outer face in addition to spinules on the ventral margin. Pereopods 5–7 have no long setae on the anterior margin of the merus and carpus, a relatively short endopodite of uropod 3 that never exceeds 60% of the exopodite. Antenna 2 with setae as long as or longer than the diameter of the article, without calceoli Etymology Thespecificepithet‘latispinus’ refers to the presence of spinules on the lateral surface of epimeral plate 2, which is unique in North African freshwater Gammarus. Type material Holotype MOROCCO•♂(19.8mm);Bakritwaterfall;33°02′59.7″N, 5°16′21.2″W; alt. 1645 m; 16 May 2021; pond at the foot of the waterfall, collected by handnet; MNHN-IU-2025-2611. Paratypes MOROCCO•3♂♂;samedataasforholotype;MNHN-IU-2025-2612•1♀;samedataasforholotype; MNHN-IU-2025-2613. Other material examined (used for molecular analysis) MOROCCO•5incompletespecs(♂♂,♂♂orjuvs);samedataasforholotype;DNAextractsstoredin the personal collection of Christophe Piscart, University of Rennes (France); CP564 to CP566, CP609 to CP610. Description Male Habitus robust, up to 19.8 mm length (Fig. 3A). Head with truncated lateral cephalic lobe, eyes relatively small, always less than 2 × as long as wide and widely separated from mid-dorsal line, inferior antennal sinus deep (Fig. 4C). First antenna longer than half body length, with few setae (Fig. 4A). First article of peduncle longer than second, itself longer than third. Flagellum more than 2 × as long as peduncle, with35relativelylongarticles.Accessoryflagellumwith3articles.Secondantennalongerthan½of firstantenna(Fig.4B).Glandcone0.752× as long as third article of peduncle. Peduncle article 4 armed with 4 groups of setae on all sides, as long as diameter of article. Peduncle article 5 as long as, but thinner than, peduncle article 4 and armed with 5 groups of setae as long as or slightly longer than diameter PISCART C. et al., On two new species of Gammarus (Amphipoda: Gammaridae) from Morocco 129 Fig. 3. A. Habitus of Gammarus latispinussp.nov.,paratype,♂(MNHN-IU-2025-2612),19.8mm. B. Habitus of G. tazekkaensissp.nov.,paratype,♂(MNHN-IU-2025-2614),17mm. European Journal of Taxonomy 1026: 123–146 (2025) 130 of article. Flagellum with 12 articles and armed with transverse rows of setae longer than articles and decreasing in length distally. Calceoli absent. Mouthparts similar to those of other species of Gammarus (Fig. 5). Mandible incisor 4-toothed, lacinia mobilis 4-toothed, followed by row of plumose setae. Molar robust, triturative, with one plumose seta (Fig. 5A). Three articles of mandibular palp well developed (Fig. 5B). First article unarmed, second armed with 12–15 long ventral setae. Third article with two rows of A-setae and B-setae, row of more Fig. 4. Gammarus latispinus sp.nov.,holotype,♂(MNHN-IU-2025-2611), 19.8 mm. A. Antenna 1. B. Antenna 2. C. Head. PISCART C. et al., On two new species of Gammarus (Amphipoda: Gammaridae) from Morocco 131 than 30 regular D-setae, and 5 long apical E-setae. Right maxilla 1 asymmetric relative to left (Fig. 5C). Inner plate triangular, longer than wide, with plumose apical setae. Outer lobe bears 11 pectinate setae. Palplongerthanouterlobe,withrelativelylongapicalsetae.Palpstwo-articulate,fine,andcurved,with 8 thin terminal spines for right maxilla 1 and enlarged with 5 stout terminal spines for left maxilla 1. Maxilla 2, inner and outer lobes with one row of apical and subapical simple setae; outer lobe slightly larger than inner lobe (Fig. 5D). Lateral row of setae ends with simple setae on external face of inner Fig. 5. Gammarus latispinussp.nov.,holotype,♂(MNHN-IU-2025-2611), 19.8 mm. A. Right mandible. B. Mandibular palp. C. Left maxilla 1 and palp of the right maxilla 1. D. Maxilla 2. E. Lower lip. F. Upper lip. G. Maxilliped. European Journal of Taxonomy 1026: 123–146 (2025) 138 marginwith3stoutteethandlongsubapicalspine;distalpartoflobecoveredwithfewfinesetulesand bearing lateral simple setae on outer margin. Outer lobe with lateral margin evenly rounded, distomedial margin fringed with ~20 knife-like teeth; teeth progressively thinner towards distal part, apex with 7–8 plumose setae. First segment of palp short, trapezoidal and bearing few distal robust setae on distomedial angle; segment 2 long, bearing numerous setae (> 20) on inner margin and 2–3 groups of simple setae on outer margin. Segment 3 slightly expanded distally, with many groups of facial and marginal setae. Dactylus with few setae; unguis shorter than dactylus. Gnathopod 1 more slender and slightly shorter than gnathopod 2, subchelate (Fig. 11A); basis longer than depth of coxa 1; carpus shorter than propodus, with hind margin furnished with setae and several rows of Fig. 10. Gammarus tazekkaensis sp.nov.,holotype,♂(MNHN-IU-2025-2613),17mm. A. Right mandible. B. Mandibular palp. C. Left maxilla 1 and palp of the right maxilla 1. D. Maxilla 2. E. Lower lip. F. Upper lip. G. Maxilliped. PISCART C. et al., On two new species of Gammarus (Amphipoda: Gammaridae) from Morocco 139 setae on outer face. Propodus pyriform, with 2–3 groups of simple dorsal setae and many ventral setae. Palm armed with medial palmar spine, variable number of palmar angle spines and few smaller spines along posterior margin; dactylus shorter than palm width. Gnathopod2carpusshorterthanpropodus(Fig.11B).Palmmoretransverseandstrongerthaninfirst gnathopod, with more groups of longer dorsal and ventral setae and only 2–3 rows of lateral setae on outer face. Palm also with thin medial palmar spine and several strong and small spines toward palmar angle; dactylus as long as or slightly longer than palm width. Pereopod 3 slightly longer than pereopod 4 (Fig. 11C). All segments armed with many groups of long setae on posterior margin and few spines on anterior margin. Propodus with 4–5 spines on posterior Fig. 11. Gammarus tazekkaensissp.nov.,holotype,♂(MNHN-IU-2025-2613),17mm. A. Gnathopod 1. B. Gnathopod 2. C. Pereopod 3. D. Pereopod 4. European Journal of Taxonomy 1026: 123–146 (2025) 140 margin. Dactylus relatively short with one distal seta. Pereopod 4 similar to pereopod 3, but setation reduced in both density and size (Fig. 11D). Coxal plates 1–4 with rounded ventral corners, set with short ventral and lateral setules (Fig. 11). Coxal plate 4 wide and deep reaching ~0.75 × the length of basis. Pereopods 5–7 similar in shape, but pereopod 5 15% shorter than pereopods 6 and 7 (Fig. 12); meri, carpi and propodi with very few setae, sometimes longer than spines along anterior margin, especially on pereopod 5. Pereopod 5 with short subrectangular basis less than 1.7 × as long as wide (Fig. 12A). Pereopods 6 and 7 bases 2 × as long as wide (Fig. 12B–C). Pereopod 7 similar to pereopod 6, but basis different and constricted near distal end. Fig. 12. Gammarus tazekkaensis sp.nov.,holotype,♂(MNHN-IU-2025-2613),17mm. A. Pereopod 5. B. Pereopod 6. C. Pereopod 7. PISCART C. et al., On two new species of Gammarus (Amphipoda: Gammaridae) from Morocco 141 Uropod 1 longer than uropod 2; basis with 3 lateral spines on each side and few terminal spines (Fig. 13A). Endopodite as long as exopodite, armed with 1–3 lateral spines and 3 terminal spines. Uropod 2 similar to uropod 1 but much shorter (Fig. 13B), endopodite and exopodite with one lateral spine on each side. Uropod 3 basis with long distal spines (Fig. 13C); endopodite length 0.5–0.6 × that of exopodite, both bearing mainly plumose setae on inner and outer margins and few spines on outer margins. Dorsal surface of metasome unarmed, except for few setules on distal margin of last segment. Urosome segments with rare dorsal setae, as long as spines; each urosomite armed with 2 pairs of spines on each side. Epimeral plates postero-inferior corner rounded on plate 1 and subrectangular on plates 2 and 3 (Fig. 13D). Epimeral plate 1 with relatively long setae along anterior part. Epimeral plates 2 and 3 armed Fig. 13. Gammarus tazekkaensis sp.nov.,holotype,♂(MNHN-IU-2025-2613),17mm. A. Uropod 1. B. Uropod 2. C. Uropod 3. D. Epimeral plates 1–3. E. Pleopod 1. F. Pleopod 2. G. Pleopod 3. H. Telson. European Journal of Taxonomy 1026: 123–146 (2025) 142 with 2–3 spinules on ventral margin; epimeral plate 2 with diagonal ridge. Pleopods 1–3 similar in shape with2couplinghooksonbasisandverylongplumosesetaeonflagellum(Fig.13E–G). Telson lobes elongate, each lobe about 2 × as long as wide (Fig. 13H). Armature of lobes consisting of two apical spines, one lateral spine and several long dorsal and lateral simple setae. Female Females shorter than males, maximal observed size 12 mm. Antenna 2 with more and sometimes longer setae than in males. Telson lobes similar to those of males, with lateral spines and several lateral and dorsal setae. Exopodite of uropod 3 shorter but similar in structure to that of males. Ecology and distribution Despite additional sampling in the study area, the species has never been found outside the type locality in the Ras El Oued River, located in Tazekka National Park. Gammarus tazekkaensis sp. nov. seems to require habitats with good water quality and relatively high ionic concentration (Table 2). Differential diagnosis Gammarus tazekkaensis sp. nov. is characterized by the presence of long setae and by the lack of calceoli on antenna 2, the lack of long setae on pereopod 7 and a telson with a lateral spine on each lobe. Among members of the North African Gammarus, few species share these characteristics. Gammarus tazekkaensis resembles G. acalceolatus, G. latispinus sp. nov. and G. marmouchensis in lacking calceoli, but it differs from these species in several characters. It differs from G. acalceolatus by having long setation on antenna 2 and short setation on pereopods 5–7. It differs from G. latispinus in the absence of lateral spinules on epimeral plate 2, a pereopod 5 that is slightly shorter than pereopods 6 and 7, the presence of a lateral spine on the telson, and the number of Aand B-setae rows on the mandibular palp. Finally, it differs from G. marmouchensis inhavingaflaturosome,subrectangularepimeralplates2and 3, and telson armature bearing a lateral spine on each lobe. It resembles G. gauthieri, G. rifatlensis and G. marmouchensis in lacking long setae on pereopods 5–7, but differs from these species by the presence of long setae on antenna 2. Discussion The consensus of the morphological and molecular results showed that the two investigated Gammarus populations from Morocco are distinct from their congeners and should be recognized as two new species. Both species belong to the G. pulex-group because of the characteristic setation of pereopods 3 and 4, the lack of long setae on pereopods 5–7, and the relative size of the uropod 3 endopodite, not overreaching 0.6 ×theexopodite(Karaman&Pinkster1977).Atfirstglance,thenewlyidentifiedspecies are morphologically close to G. acalceolatus and G. marmouchensis due to the absence of calceoli on antenna 2, already recorded in Morocco (Karaman & Pinkster 1977; Fadil & Dakki 2006). However, Table 2. Mean values of the physical and chemical water parameters measured at the type localities of Gammarus latispinussp.nov.(SidiElMakhfi)and G. tazekkaensis sp. nov. (Bab Boudir). Added are the Moroccan surface water guidelines of good quality (MSWG). Sampling sites Temperature (°C) pH Electrical conductivity (mg∙l-1) Dissolved oxygen (mg∙l-1) Ammonium (mg N∙l-1) BOD5 (mg∙l-1) SidiElMakhfi 19°C 7.5 282 10.6 0.01 2.5 Bab Boudir 17°C 7.2 485 9.4 0.01 3.4 MSWG – 6.5–8.5 < 1300 > 5 < 0.5 < 5 PISCART C. et al., On two new species of Gammarus (Amphipoda: Gammaridae) from Morocco 143 they are clearly distinguished from these species morphologically by the setation of pereopods 5–7, the armature of epimeral plates 2–3, and the telson. The two new species also differ from each other in several stable morphological characteristics and are geographically separated. Finally, molecular data on the COI and 28S genes (genetic distance, delimitation methods and phylogeny) strongly support the distinction between the two species and the other species found in this region. The distribution of both species is limited to their type localities: near Taza for G. tazekkaensis sp. nov. and south of Azrou (Bakrit Waterfalls) for G. latispinus sp. nov. In these localities, the two species do not co-occur with other amphipod species. The two new species can easily be confused with species related to G. gauthieri, which underlines the need to continue the taxonomic revision of G. gauthieri across its vast distribution area between Spain and Algeria (Ayati et al. 2019), where other species probably remain to be described. This region is characterised by a remarkable diversity of wetland habitats, supporting rich and original biodiversity, with numerous endemic taxa described recently. These taxa belong to different classes of benthic invertebrate communities such as Mollusca Cuvier, 1797 (Glöer et al. 2020; Taybi et al. 2022; Bespalaya et al. 2024), Trichoptera Kirby, 1813 (Ibrahimi et al. 2021), and Diptera Linnaeus, 1758 (Mabrouki et al. 2023). The high level of endemicity in the Middle Atlas makes aquatic communities vulnerable to biological invasions, which represent a major threat to aquatic biodiversity in Morocco. In fact, the Middle Atlas is one of the main hotspots for biological invasions in the country’s freshwater systems (Taybi et al. 2023) Ramsar Site and SIBE. Numerous invasive vertebrate and invertebrate species have been documented as established in the area, and their populations are increasing (Taybi et al. 2024; Mabrouki et al. 2025; El Caidi et al. 2025). Conservationproblemsarefurtherexacerbatedbythesignificantrainfalldeficitlinked to climate change, which is causing severe droughts with substantial consequences for water resources. As a result, many freshwater ecosystems in the Middle Atlas massif are drying out more frequently (el Morabet et al. 2021). In addition to stepping up hydrobiological and taxonomic studies, drastic measures are needed to protect the freshwater wetlands of the Middle Atlas and North Africa in general. Acknowledgement We greatly thank Dominique Valet for his valuable help in molecular analyses. 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The other members of the consortium are: Meise Botanic Garden, Meise, Belgium; Natural History Museum of Denmark, Copenhagen, Denmark; Naturalis Biodiversity Center, Leiden, the Netherlands; Museo Nacional de Ciencias Naturales-CSIC, Madrid, Spain; Leibniz Institute for the Analysis of Biodiversity Change, Bonn – Hamburg, Germany; National Museum of the Czech Republic, Prague, Czech Republic; The Steinhardt Museum of Natural History, Tel Aviv, Israël.