Orchestia mauritanica Momtazi & Myers, 2025

Momtazi, Farzaneh, Myers, Alan A., Knorrn, Alexander Hans, Moctar, Sidi Mohamed M., Freiwald, André & Sonnewald, Moritz, 2025, Orchestia mauritanica sp. nov. (Amphipoda: Talitridae), a new sand hopper from Mauritania with a Comprehensive Key to the World Species of Orchestia, Zootaxa 5701 (5), pp. 563-572 : 565-570

Orchestia mauritanica Momtazi & Myers , sp. nov.

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( Figs 2–5 )

Diagnosis. Male gnathopod 2 propodus posterior margin distally straight with distinct proximal shelf; pereopod 7 with basis posterior margin lacking concavity, carpus expanded, irregular.

Material examined

Holotype: male (preserved in alcohol); 20.42 mm; Mauritania, Cap Sainte Anne ; 20°40′46″ N, 16°40′32″ W; 3 March 2024; M. Sonnewald, A. Knorrn, S. Moctar & A. Freiwald leg; hand collection at intertidal sandstones during low tide; Station BdL-61; Crustacea— SMF 62512 .

Paratype: male (preserved in alcohol); 22.27 mm; Mauritania, Cap Sainte Anne ; 20°40′46″ N, 16°40′32″ W; 3 March 2024; M. Sonnewald, A. Knorrn, S. Moctar & A. Freiwald leg; hand collection at intertidal sandstones during low tide; Station BdL-61; Crustacea— IMROP 60 .

Type locality. Mauritania, Cap Sainte Anne.

Etymology. The species name “mauritanica ” is derived from the Latin name of the Islamic Republic of Mauritania, known for its species-rich marine ecosystems, such as the intertidal sandstones, which are inhabited by Orchestia mauritanica sp. nov. within the Banc d’Arguin National Park.

Description of male holotype ( 20.42 mm).

Head. Eyes round, moderate size (1/5 head length). Antenna 1 short, reaching beyond peduncular article 4 of antenna 2; the first peduncular article as long as the second and third ones, bearing three plumose and several robust setae; the second article has one plumose seta and several robust setae; accessory flagellum absent; primary flagellum of the left antenna with 6 articles, and the primary flagellum of the right antenna with 7 articles. Antenna 2 reaching the third pereonite; peduncular article 5 as long as the combined length of third and second peduncular articles; primary flagellum with 17 articles, final article cone-shaped, with imbricated setae virgula divina ( Lowry & Springthorpe, 2015). Labrum without epistome. Lower lip, distolateral setal tuft absent, with vestigial inner plates. Left mandible, lacinia mobilis with 5 cusps; molar triturative; incisor with 6 dentate; bearing 6 accessory blades and without palp. Right mandible, lacinia mobilis 5–cuspidate; incisor with 5 dentate; bearing 4 accessory blades and without palp. Maxilla 1 without palp; inner plate with two plumose setae; outer plate with 9 dentate setae; inner margin has several fine setae. Maxillae 2 outer plate equal to inner plate, covered apically with simple setae, outer margin with 6 simple setae; inner plate with apical robust setae and proximal blade setae. Maxilliped palp article 2 with distomedial lobe, article 4 small, button-shaped; inner plate reaches to the base of the second palp article, bearing 3 apical dentate setae and several plumose setae on apical and inner margins; outer plate subequal to inner plate and covered with simple setae.

Pereon. Gnathopod 1 subchelate, coxa smaller than that of coxa 2, with a small anterior ventral lobe, bearing stout marginal setae; the basis 0.82× as long as coxa; ischium quadrate; merus trapezoidal, carpus with round posterior-proximal lobe covered with palmate setae; propodus subquadrate with several robust setae on anterior margin and facial, posterior margin with palmate setae; palm sinusoidal, distinct a proximal protuberance covered with facial and marginal robust setae; dactylus shorter than palm. Gnathopod 2 subchelate; basis 2.67 × as long as broad; ischium with triangle lobe on antero-distal margin; merus with two robust setae on posterior margin; carpus triangular; propodus with four facial robust setae, weakly triangular, distal width 1.9 × proximal width, presence a distinct shelf in the middle length of posterior margin; palm distinct with prominent shelf at the beginning, straight with two rows of robust setae; dactylus overlapping palm.

Pereopods 3–7 bicuspidactylate. Pereopod 3 longer than pereopod 4, coxa with robust setae on ventral margin. Pereopod 4 coxa with robust setae on ventral margin. Pereopod 5 basis subovid, propodus 1.3 × long as carpus with marginal robust setae on the posterior lobe, basis subovoid. Pereopod 6 shorter than pereopod 7; coxa rounded, without marginal seta. Pereopod 7 basis posterior margin weakly serrate; merus elongate, weakly triangular, becoming 2 × as wide distally as proximally; carpus irregular, anterior margin strongly convex, posterior margin straight; carpus and merus subequal in length; propodus 1.2 × length of the carpus.

Pleon. Epimeron 1 subquadrate with straight posterior margin. Epimeron 2, posterior margin subconcave, postero–distal angle round. Epimeron 3 posterior margin straight, postero–distal angle round. Uropod 1 peduncle longer than rami, without distolateral robust seta; rami subequal, inner ramus with 3 marginal and 4 apical robust setae, outer ramus with 3 marginal and 3 apical robust setae. Uropod 2 peduncle subequal in length with subequal rami; outer ramus with 3 marginal robust setae and 3 apical robust setae; inner ramus with 6 marginal robust setae in two rows and 3 apical robust setae. Uropod 3 peduncle 1.2 times as long as broad, 1.3 times as long as ramus; ramus unarticulate, 2 times as long as broad, outer margin with 7 robust setae. Telson notched, with about 8 apical robust setae on each side.

Female not found.

Remarks. Orchestia mauritanica sp. nov. is a new North Atlantic Orchestia species group member. It belongs to a species group defined by Myers & Lowry (2020b), including Q. aestuarensis Wildish, 1987 , O. magnifica, Vecchi, 1931 , and O. mediterranea Costa, 1853 , which are characterized by irregular carpus in the seventh pereopod and extremely acute palm in the second male gnathopod. The straight distal posterior propodus margin and a distinct proximal shelf on the second male gnathopod and the lack of concavity on the posterior margin of the carpus in the seventh pereopod characterize the new species.

Figures

FIGURE 2. Orchestia mauritanica sp. nov. Holotype. male (CRUSTACEA-SMF 62512); habitus and gnathopods. Scales a = 5 mm and b = 2.5 mm.

FIGURE 3. Orchestia mauritanica sp. nov. Holotype, male (CRUSTACEA-SMF 62512); pereopods and epimerons. Scales a = 1 mm.

FIGURE 4. Orchestia mauritanica sp. nov. Holotype. male (CRUSTACEA-SMF 62512); antenna, uropods, telson, and mouthparts. Scales a = 0.5 mm and b = 1 mm.

FIGURE 5. Micro CT images of Orchestia mauritanica sp. nov. male (Crustacea—IMROP 60), 61°24’32.76” E), 22.27 mm, paratype. Scale = 5 mm. A: Lateral view. B: Ventral view.