Gammarus latispinus, Piscart & Mabrouki & Taybi, 2025

Piscart, Christophe, Mabrouki, Youness & Taybi, Fouzi 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, pp. 123-146 : 128-135

Gammarus latispinus sp. nov.

urn:lsid:zoobank.org:act:

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 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 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 lobe. Lower and upper lips similar to those of Gammarus , with setose inner surface and without inner lobe ( Fig. 5E–F).

Maxilliped inner lobe ~3 × as long as wide, distal margin with 3 stout teeth and long sub-apical spine ( Fig. 5G); distal part of lobe covered with 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 5–6 plumose setae. Rows of teeth on inner and outer lobes continue with plumose setae proximally and distally. First segment of palp short, trapezoidal and bearing few distal simple setae on distomedial angle; segment 2 long, bearing numerous setae (> 20) on inner margin and 3–4 groups of simple setae on outer margin. Segment 3 slightly expanded distally, with numerous facial and marginal setae. Dactylus with few setae; unguis shorter than dactylus.

Gnathopod 1 more slender and slightly shorter than gnathopod 2, subchelate ( Fig 6A); basis longer than depth of coxa 1; carpus shorter than propodus, with hind margin furnished with setae and several rows of setae on outer face. Propodus pyriform, with few groups of simple dorsal setae and many ventral setae. Palm armed with strong 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. 6B). Palm more transverse and stronger than for first gnathopod, with more groups of longer dorsal and ventral setae and 5–6 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 palm width.

Pereopod 3 longer than pereopod 4 ( Fig. 6C). All segments armed with many groups of setae longer than segment diameter on posterior margin and few spines on anterior margin. Propodus with 5–7 spines on posterior margin and one long distal spine anteriorly. Dactylus relatively short with one single seta. Pereopod 4 similar to pereopod 3, but setation, especially of propodus, reduced in both density and size ( Fig. 6D).

Coxal plates 1–4 with rounded ventral corners, set with short ventral and lateral setules ( Fig 6). Coxal plate 4 wide and deep, reaching almost length of basis.

Pereopods 5–7 similar in shape but pereopod 5 25% as short as pereopods 6 and 7 ( Fig 7); basis with 2 proximal rows of 4–5 setae on external margins, meri, carpi and propodi with very few setae as long as or shorter than spines along anterior margin, especially on pereopod 5. Pereopod 5 with short subrectangular basis less than 1.5 × as long as wide ( Fig. 7A). Pereopods 6 and 7 bases are 2 × as long as wide ( Fig. 7B–C). Pereopod 7 similar to pereopod 6 but basis different and constricted near distal end.

Uropod 1 almost as long as uropod 3; basis with 1 or 2 short marginal and 4–5 terminal spines ( Fig. 8A). Endopodite and exopodite subequal in length and armed with 2–3 lateral spines. Uropod 2 similar to uropod 1 but shorter ( Fig. 8B). Uropod 3 relatively long; basis with long distal spines ( Fig. 8C); endopodite length 0.5–0.6 × that of exopodite; exopodite with mainly simple and plumose setae on inner and outer margins and few spines on outer margin; endopodite only with plumose setae.

Dorsal surface of metasome unarmed, except for few setules on distal margin of last segment. Urosome segments with rare dorsal setae, always shorter than spines. Urosomites 1 and 2 armed with 2 pairs of spines on each side, and urosomite 3 with only one spine on each side, longer than spines on urosomites 1 and 2. Epimeral plates with postero-inferior corner rounded on plate 1 and subrectangular on plates 2 and 3 ( Fig. 8D). Epimeral plate 1 with relatively long setae along ventral margin. Epimeral plates 2 and 3 exhibit main discriminating morphological trait, with 1–3 spinules on outer face and 2–3 spinules on ventral margin; epimeral plate 2 with diagonal ridge. Pleopods 1–3 similar in shape, with 2 coupling hooks and several groups of setae on basis, and very long plumose setae on the flagellum ( Fig. 8E–G).

Telson lobes elongate, each lobe about 2 × as long as wide ( Fig. 8H). Armature of lobes consisting of one apical spine and several long dorsal, distal, and lateral simple setae longer than apical spine.

Female

Females slightly shorter than males, maximum size observed 14 mm. Characteristic lateral spinules on outer face of epimeral plates 2 and 3 not present in females.

Ecology and distribution

Despite additional samplings in the study area, the species was never been found outside the type locality in Oued Fellat. The analysis of the physicochemical parameters of the water (ammonium and BOD 5) showed a good environmental quality of the water, according to the Moroccan surface water guidelines of good quality ( Table 2 ).

Differential diagnosis

Gammarus latispinus sp. nov. is characterized by the presence of spinules on the outer margin of epimeral plates 2 and 3. Among North African members of Gammarus , no species has spinules on the outer face of the epimeral plates. Gammarus latispinus resembles G. gauthieri , G. rifatlensis Fadil & Dakki, 2006 , and G. marmouchensis Fadil & Dakki, 2006 , in the absence of long setae on pereopods 5–7, but differs from these species in the presence of long setae on antenna 2. Due to the lack of calceoli, the new species is morphologically close to G. acalceolatus and G. marmouchensis but differs from G. acalceolatus by the setation of antenna 2 and pereopods 5–7, and from G. marmouchensis by a flat urosome, the presence of two rows of B-setae on the mandibular palp, the subrectangular epimeral plates 2 and 3, and the armature of the telson (long dorsal setae and only one terminal spine for G. latispinus ).