Metacrangonyx boutini, Elassad & Messouli & Boulal & Boudellah & Ghamizi, 2025

Elassad, Nabila, Messouli, Mohamed, Boulal, Mokhtar, Boudellah, Abderrazzaq & Ghamizi, Mohamed, 2025, A new species of the genus Metacrangonyx (Crustacea: Amphipoda) from the ground waters of Morocco, with comparisons to all other species in the genus, Zootaxa 5683 (4), pp. 513-529 : 514-522

Metacrangonyx boutini sp. nov., El-Assad, Messouli & Boulal, 2024

Etymology: Species dedicated to Mr. Claude Boutin, who set up and directed the work of the team at the Underground Hydrobiology Laboratory at the Marrakech Faculty of Science.

Material examined: 51 individuals collected in the Tiznit area (44 during 1988 and 7 during 2023 survey) ( Fig. 1); Locations, codes of wells prospected and date of prospection are shown in table 1.

Type locality: Well at 4 km north of Tiznit, 29°41'31.38N, 09°45'53.84W; altitude 181m; water temperature 23.45°C; conductivity 7093 μs/cm ( 24/01/2023). Well protected by a small edge and covered on top ( Fig. 1); equipped with electric pump driven by solar panels; circular opening 40 cm in diameter; depth 60 m; water column height around 40 m ( 12/03/2024) .

Material examined: One female holotype ( Fig. 2 ) and 4 paratypes ( two males and two females), deposited in the Museum of Natural History of Marrakesh .

Description

Diagnosis: Antennula 64% as long as body length. Uropod 3 peduncle lacking robust seta and with one parietal seta; exopodite elongated with two apical and 1–2 parietal robust setae.

Habitus ( Fig. 2 ): Body elongated, laterally flattened, habitus often arched. Lateral cephalic lobes angular; eyes absent. Males ( 3–5.65 mm) smaller than females ( 4–7.8 mm).

A ntennula ( Fig. 3A ) 64% as long as total body length. Peduncular segment 2 (Pa2) barely 4/5 of Pa1; Pa3 more than 4/5 of Pa2; Pa1 with a sternodistal robust seta ( Fig. 3A ). Main flagellum with 22–35 articles, each with one aesthetasc except the 5–6 proximal articles. Accessory flagellum with 4–5 articles, slightly outreaching the middle of the third article of the main flagellum. An adult male displayed only three articles on one branch and four on the other.

Antenna ( Fig. 3B ) short, about 36% as long as antennula and never reaching its half; peduncle barely shorter than that of antennula, with five segments. First three segments incompletely separated. Pa1with two or three setae and a fairly short conical gland at its base barely exceeding Pa3; reduced antennal scale on Pa3 with two subapical setae ( Fig. 3B ). Pa4 with 1–4 robust setae. Pa5 slightly shorter than Pa4; Pa5/Pa4 = 0.9. Flagellum with 9–14 articles (up to 15 in some large individuals).

Upper lip entire; posterior edge sub-rounded; covered with many thin setae ( Fig. 3C ).

Mandibles ( Fig. 3D, E ) robust; incisor process with 5–6 teeth, second and third teeth more developed, the others identical in size. Left mandible ( Fig. 3E ) with 4 teeth on lacinia mobilis, rarely bearing a rudimentary fifth one, arranged in the same plane. First tooth largest, three others smaller and identical in size; incisivus accesorius process comprising 6–8 strong saw-shaped robust setae and 4–6 thin plumose setae. Further down is a tuft of 5 pinnate setae. Molar process of complex structure, very stout, carrying short molar seta ( Fig. 3E ). Right mandible ( Fig. 3D ) incisivus accesorius with up to 9 strong saw-shaped robust setae; lacinia mobilis composed of two large teeth arranged in a first plane, and several smaller teeth of unequal size differentiated in a second plane. Molar process bearing a long seta; Mandibular palp with two segments, rarely three; Second segment approximately of same length as first; proximal segment without setae; distal segment with two distal setae slightly longer than segment itself.

Lower lip ( Fig. 3F ) without inner lobes, outer lobes rounded with many setae at inner margin; lateral processes relatively short and with rounded tip.

Maxilla I ( Fig. 4A ) Inner lobe with 14 –20 plumose setae; outer lobe with two rows of strong serrate robust setae, sometimes close together apically and sometimes spread apart, giving rise to an apical row and an inner one. No relationship of this arrangement with sex or size has been found; surface of both lobes bearing many fine setae. Palp bisegmented; left branch narrower than right one, with four stout setae and one slender long seta apically on distal segment.

Maxilla II ( Fig 4b ): inner lobe bearing two rows of plumose setae, lateral row with 15–22 plumose setae; inner row with 17 setae and 9 –10 smooth setae; outer lobe longest; margin with 14 long setae.

Maxilliped ( Fig. 4C ): inner lobe extending well beyond half of outer lobe, bearing four long setae three of which plumose on inner margin, and 3–4 bifid teeth and 12 setae on distal margin. Left outer lobe barely exceeding half of second palp segment, bearing 15 strong setae on inner margin, nine subdistal lanceolate teeth followed by a strong serrulate seta and three simple setae. Right outer lobe more armed with 10 lanceolate teeth distally and four strong setae, two of them serratulate. Palp 4 segmented, distal segment bearing a strong claw; setae and setules arranged as in Fig. 4C .

Gnathopod I ( Fig. 4D ) with rectangular coxal plate longer than wide, with eight marginal setae: two long posteriorly, three short anteriorly and three ventrally. Carpus length attaining 73% of basis length and 138% of propodus length. Propodus length 72% of carpus length. Basis expanded distally and bearing few short setae on anterior margin and five long ones, including four on posterior margin and one more inward, and a small distal seta on posterior side of posterodistal margin. Ischium with group of four setae on posterodistal edge, including one long, one strong, and two reduced ones. Merus short with eight setae, one of which being stronger and longer than rest; integument of distal region of segment caespitose. Propodus quadrangular; posterior margin forming an obtuse angle with palmar margin, latter armed with a row of micro-spinulate and four large bifid teeth. Dactylus slightly longer than palmar margin ( Fig. 4F ).

Gnathopod II ( Fig. 4E ) Female propodus twice as long as wide, with oblique palmar margin with 13–19 bifid teeth. Dactylus with apical sensory organ ( Fig. 4H ).

Female Gnathopod II and pereopods 3–5 (Pe3–5) each showing an elongate ovigerous oostegite furnished with long and short smooth marginal seta (Fig. 5F).

Gills inserted at base of coxal plates of gnathopod II and Pe3 to Pe6 (Fig. 5G, H);

Pereopods (Fig. 5A–E): Pe3 and Pe4 differing only in coxal plates; coxa 4 wider, with distinctly concave posterior margin and broad ventral margin; third plate much longer than broad. Pe5, Pe6 and Pe7 similar, Pe5 shortest and Pe6 only slightly longer than Pe7. Pe5 and Pe6 basis with slightly produced posterodistal lobes. Pe7 basis with very convex posterior edge and a well-defined, strongly overhanging posterodistal lobe in both male and female.

Pleon ( Fig. 6A–C ): Epimeral plates, each with one short posterolateral simple seta implanted very close to posteroventral angle.

Pleopods well developed. Each peduncle bearing a linguiform process distally; posterodistal side of peduncles adorned with 2 hooked retinacles. In 13 individuals, 2–2; 2–2 and 2–2 retinacula were observed on Pl1 to Pl3. In two individuals dissected, we observed retinacula distributed as follows: 2-2; 3–2; 2–2. Peduncles often glabrous, exceptionally with a long pinnate seta in medio-posterior position. Endopodite and exopodite formed by respectively 8–14 articles. Exopodite often has one or two articles more than the corresponding endopodite. In the individuals examined, the number of articles varies between 10 and 14 for the exopodite and between 8 and 12 for the endopodite; each article carrying a very long plumose seta on both sides, easily exceeding five times the height of the article.

Uropod 1 peduncle ( Fig. 6D, E ) much longer than wide, with a basofacial robust seta and eight strong robust setae arranged in two rows. Rami shorter than peduncle; outer ramus only slightly shorter than inner one, bearing four equidistant lateral robust setae and three apical setae, one of which reduced; inner ramus with three lateral and four distal robust setae, one of which reduced.

Uropod 2 ( Fig. 6E ) similar to U1; peduncle wider and shorter than U1, with four robust setae scattered over distal half of dorsal surface. Rami longer than peduncle; outer ramus, only slightly shorter than inner ramus and armed with three equidistant lateral robust setae and three distal ones, one of which reduced; inner ramus with four equidistant lateral robust setae and three distal ones, one of which reduced.

FIGURE 5. A. Pereiopod 3; B. Pereiopod 4; C. Pereiopod 5; D. Pereiopod 6; E. Pereiopod 7; F. Oostegite; G. female gills; H. male gills.

Uropod 3 ( Fig. 6F ) peduncle wide and short, with a parietal seta on inner surface; distal margin with two small depressions bearing two simple setae, exceptionally 3 or 4. Exopodite slightly elongated, truncated, with two strong robust apical setae and one or two parietal ones. Endopodite reduced, globular and with a very short subapical robust seta.

Telson ( Fig. 6F, G ) showing a characteristic trapezoid shape, wider than high; distal margin straight, delimiting a wide glabrous zone between the two strong distal setae, close to which two distal multifid setae are inserted; lateral margin protruding at level of implantation of two multifid setae.

Sexual dimorphism observed in propodus and carpus of gnathopod2: male propodus longer than in female, with 17 to 22 slightly bifid teeth on palm margin; carpus shorter, and dactylus longer, with a more developed sensory organ ( Fig. 4G ); female gill stalks (Fig. 5G) slightly longer than in males (Fig. 5H).

Figures

FIGURE 2. Habitus of an adult female from Tiznit well. (Length 5.5 mm).

FIGURE 3. A. Antennula; B. Antenna; C. Upper lip; D. Right mandible; E. Left mandible; F. Lower lip.

FIGURE 4.A. Maxilla 1; B. Maxilla 2; C. Maxilliped; D. Gnathopod1; E. Femal Gnathopod2; F. detail of Gnathopod 1; G. Dactyl of Gnathopode 2 male; H. Dactyl of Gnathopode 2 female.

FIGURE 6. A. Pleopod 1; B. Pleopod 2; C. Pleopod 3; D. Uropod 1; E. Uropod 2; F. Uropod 3 and Telson; G. Telson.