Psammogammarus lucayensis, Jaume, Damià, Iliffe, Thomas M. & Van Der Ham, Joris L., 2013

Jaume, Damià, Iliffe, Thomas M. & Van Der Ham, Joris L., 2013, A new Psammogammarus (Amphipoda: Eriopisidae) from anchialine pools on the Exuma Cays, Bahamas, Zootaxa 3700 (1) : -

publication ID	https://doi.org/ 10.11646/zootaxa.3700.1.2
publication LSID	lsid:zoobank.org:pub:B13ECE90-D744-40DD-B754-B42FEF9BAA70
DOI	https://doi.org/10.5281/zenodo.6150188
persistent identifier	https://treatment.plazi.org/id/03D4B774-0177-FFBE-FF03-FA324CB0B713
treatment provided by	Plazi
scientific name	Psammogammarus lucayensis
status	sp. nov.

Treatment

Psammogammarus lucayensis View in CoL sp. nov.

( Figs 2–10 View FIGURE 2 View FIGURE 3 View FIGURE 4 View FIGURE 5 View FIGURE 6 View FIGURE 7 View FIGURE 8 View FIGURE 9 View FIGURE 10 )

Material examined. Anchialine pool on Little Iguana Cay (Exuma Cays, Great Bahama Bank). Holotype: Adult female (oöstegites developed, setose) 3.77 mm, completely dissected and mounted on single slide [RMNH.CRUS.P.10523]. Paratypes: Male 3.10 mm, completely dissected and mounted on single slide [RMNH.CRUS.P.10524]; 75 specimens, all probably females, of which largest 3.73 mm, in single ethanol vial [RMNH.CRUS.A.5041]. Collected by J. L. van der Ham & T. M. Iliffe, January 2003.

Diagnosis. Carpus of G2 longer than broad. Male G2 palm margin non-excavated, evenly convex and devoid of strong mid-palmar robust setae. Basis of P7 with subparallel margins. Armature arrangement of ventral margin of epimeral plates as 0–2–3. Posteroventral angle of epimeral plate 3 strongly produced. Protopod of U2 with distomedial angle armed with comb of 3–4 robust setae. U3 endopod as long as exp1. Telson with robust setae on tip.

Etymology. The specific epithet is derived from the Lucayans, the presumed first inhabitants of the Bahamas.

Description of female. Eyeless. Body ( Fig. 2 View FIGURE 2 A) slender, unpigmented, somites devoid of relevant armature or sculpturing except for robust seta present on posteroventral angle of urosomite 3 ( Fig. 9 View FIGURE 9 E). Head ( Fig. 2 View FIGURE 2 B) lacking rostrum; lateral lobes evenly rounded; antennal sinus hardly indicated. Epimeral plates ( Fig. 9 View FIGURE 9 A) with acute posteroventral angles, that of plate 3 more produced than rest; armature of ventral margin of plates (flagellate robust setae) as 0–2–3.

Antennule short, about half as long as body length ( Fig. 2 View FIGURE 2 A, B). Peduncle segments relative length as 100: 92: 43; proximal segment provided with stout flagellate robust seta subdistally on ventromedial margin. Main flagellum much longer than peduncle, articles each provided with single simple aesthetasc except most proximal and terminal. Accessory flagellum 2-articulate, about as long as two proximal articles of main flagellum combined.

Antenna ( Fig. 2 View FIGURE 2 A, B) attaining about three-quarters length of antennule. Gland cone slender, straight, pointing anteriorly; relative length of three distal segments of peduncle as 45: 100: 89. Flagellum short, about as long as distal segment of peduncle.

Labrum ordinary, globose, not figured. Paragnaths ( Fig. 3 View FIGURE 3 C) with well-developed inner lobes; outer lobes each with four multicuspidate terminal robust setae.

Left mandible ( Fig. 3 View FIGURE 3 A) ordinary, with 5-denticulate incisor, 4-denticulate lacinia and columnar molar; grinding surface of latter provided with pores as figured; molar seta pappose. Spine row comprising seven leaf-like denticulated elements plus seven slender interspersed pappose setae. Mandibular palp distal segment shorter than second, armed with two distal setae plus six setae along anterior margin; second segment with three setae along anterior margin. Right mandible ( Fig. 3 View FIGURE 3 B) different from left counterpart in multidenticulate lacinia and shorter molar seta.

Maxillule ( Fig. 4 View FIGURE 4 A) coxal endite [= inner plate] with 8+2 marginal setae. Basal endite [= outer plate] with nine distal stout robust setae disposed in two rows (5+4), two of which tricuspidate, one 4-cuspidate, rest denticulated. Endopod [= palp] 2-segmented, distal segment slightly expanded distally, with two unequal stout triangular processes on distal margin; distal armature comprising two short, broad and stout denticulated robust setae, plus four more slender denticulated setae placed subdistally on outer surface of segment as figured.

Maxilla ( Fig. 4 View FIGURE 4 B) with oblique (“facial”) row on inner lobe composed of up to eight plumose setae; rest of limb as figured.

Maxilliped ( Fig. 4 View FIGURE 4 C) basal endite subrectangular with truncate distal margin, latter with four broad cuspidate robust setae; remaining armature comprising oblique row of six plumose setae on posterior surface of endite, and three simple setae on anterior surface as figured. Ischial endite ( Fig. 4 View FIGURE 4 D) spoon-shaped with six robust setae on distal margin, of which distomedial shortest and cuspidate, rest denticulated and progressively more slender towards lateral; submarginal cluster of ca. 10 simple setae with blunt tip placed close to medial margin of endite on its anterior surface. Merus-dactylus (= palp) slender, with nail (= dactylus + unguis) as long as broadly expanded propodus ( Fig. 4 View FIGURE 4 E).

Pereiopodal coxae 1–4 ( Figs 5 View FIGURE 5 A, C; 6A, C) subrectangular, broader than long, each slightly overlapping one in front ( Fig. 2 View FIGURE 2 A); coxal plate 5 with broadly expanded anteroventral lobe ( Figs 2 View FIGURE 2 A; 5A); coxal plate 6 anteroventral lobe reduced ( Fig. 7 View FIGURE 7 C), lobe wanting on plate 7 ( Fig. 7 View FIGURE 7 E). Coxal gills on G2 and P3–P6, that on G2 sausage-like ( Fig. 5 View FIGURE 5 C), elongated, longer than corresponding basis; rest of gills ( Figs 6 View FIGURE 6 A, C; 7A, C) ovoid and progressively smaller towards posterior. Oöstegites on G2 and P3–P5 ( Figs 5 View FIGURE 5 C; 6A, C; 7A).

Gnathopod 1 ( Fig. 5 View FIGURE 5 A) medial surface of merus with dense patch of spinules; propodus ( Fig. 5 View FIGURE 5 B) slightly longer than carpus, 1.7 times as long as broad, broadest at palm angle; latter placed at 51 % of maximum [= dorsal] length of segment, with armature comprising large flagellate robust seta and two shorter flagellate bifid robust setae submarginally on medial surface, and two more slender, serrate flagellate robust setae on lateral surface of segment; palm margin evenly rounded, lined with microserrate hyaline frill plus submarginal row of ca. 11 small flagellate robust setae along medial surface of segment.

Gnathopod 2 ( Fig. 5 View FIGURE 5 C) propodus 1.6 times as long as carpus, 1.8 times as long as broad, with parallel anterior and posterior margins and with palm angle placed about midway of maximum [= dorsal] length of segment; palm margin evenly convex. Armature of palm margin and palm angle similar to G1 counterpart except the two shorter robust setae on medial margin are here unicuspid instead of bifid ( Fig. 5 View FIGURE 5 D).

Pereiopods 3–4 ( Fig. 6 View FIGURE 6 A–D) similar, P4 comparatively longer due to more elongated basis; nails similar, both long and slender (seven times as long as broad, and about 44 % length of corresponding propodus), each provided with two short blunt simple setae subdistally.

Pereiopods 5–7 ( Fig. 7 View FIGURE 7 A, C, E) progressively longer towards posterior, with distal segments bearing numerous flagellate robust setae distributed as figured. Basis of pereiopods moderately expanded, progressively broader towards posterior, that of P7 with posterodistal angle strongly overhanging. Pereiopod 5 nail ( Fig. 7 View FIGURE 7 B) shortest, broadly overshoot by one of flagellate robust setae placed on distolateral angle of corresponding propodus. Nail of P6 longer and more slender than P7 counterpart (compare Fig. 7 View FIGURE 7 D and F). All nails with single short blunt simple seta subdistally.

Pleopods ( Fig. 8 View FIGURE 8 A–C) ordinary, with spatial pattern and number of robust and simple setae on protopod, and of simple setae on anterior and posterior surfaces of proximal articles of endopod apparently not fixed and submitted to variability. Relative size of pleopods not corresponding to a progressive pattern of reduction towards posterior, i. e. pleopod 2 shortest whereas pleopods 1 & 3 subequal in length.

Uropod 1 ( Fig. 9 View FIGURE 9 B) protopod distinctly longer than rami, latter unequal in length, with endopod distinctly longest. Protopod provided with strong basofacial robust seta; rest of armature of segment comprising 5–6 robust setae along posterolateral margin and 3–4 robust setae along posteromedial margin; distolateral and distomedial angles of segment provided with one and two stout robust setae, respectively. Exopod with 1–2 robust setae along lateral margin and five terminal robust setae; medial margin of segment unarmed. Endopod with one robust marginal seta on lateral margin and 1–2 on medial margin; five robust setae plus simple seta placed terminally on segment; in addition, simple seta implanted anteromedially on proximal portion of segment as figured.

Uropod 2 ( Fig. 9 View FIGURE 9 C) protopod shorter than endopod; rami unequal in length, endopod distinctly longer than exopod. Protopod with 1–2 flagellate robust setae on outer margin and 0–1 on inner margin; transverse row of 3–4 robust setae on distomedial angle, and single robust seta on distolateral angle. Exopod with two robust setae on outer margin and single robust seta on inner margin; four robust setae, unequal in length, on tip; distolateral angle of segment produced into short pointed process with bicuspidate tip. Endopod with 3–4 robust setae along inner margin, 0–1 robust seta on medial margin, and five robust setae plus simple seta on tip.

Uropod 3 ( Fig. 6 View FIGURE 6 E) elongated, about twice as long as urosome ( Fig. 9 View FIGURE 9 E), strongly armed with robust setae distributed as figured. Protopod short, slightly longer than telson, about 1.6 times as long as broad, expanded distally; tiny simple seta implanted proximo-medially on dorsal surface of segment. Exopod 2-segmented, twice as long as endopod; latter about as long as proximal segment of exopod.

Telson ( Fig. 9 View FIGURE 9 D) cleft almost to base, much longer than broad. Lobes truncate with sinuose distal margin provided with 2–3 robust setae; lateral margin of lobes with two short robust setae plus penicillate seta; two long penicillate setae implanted subdistally on dorsal surface of each lobe as figured.

Description of male. The only male specimen collected, almost complete – only both U3 were missing–, showed a remarkable sexual dimorphism on G2, protopod of U1 and U2, posteroventral robust seta of third urosomite, and armature of telson. Thus the propodus of G2 ( Fig. 3 View FIGURE 3 D) is a bit broader than in the female (twice as long as broad vs. 1.8) and has a shorter posterior margin (palm angle placed at 44 % of maximum length of segment vs. at 50 % length in the female); in addition, whereas in the female this segment attains its maximum width between the anterior and the posterior margin, in the male it is reached between the anterior margin and the proximal portion of the palm margin. Furthermore, the armature of the palm angle is reduced to two unicuspid flagellate robust setae on medial margin (vs. three robust setae present in the female).

The U1 protopod is comparatively shorter than in the female, being as long as the corresponding exopod and much shorter than the endopod, whereas in the female the protopod is longer than both rami (compare Figs 10 View FIGURE 10 D, E and 9B, E). In addition, the robust seta present on the distomedial angle of protopod is hypertrophied in the male.

The U2 protopod is also shorter than in the female, being 1.6 times as long as broad vs. 2.7 times in the female (compare Figs 9 View FIGURE 9 C and 10F).

The robust seta present on the posteroventral angle of the third urosomite is much longer than in the female, being distinctly longer than half the U2 protopod length (compare Figs 10 View FIGURE 10 D and 9E).

The telson is more expanded proximally compared to the female, whereas its flagellate robust setae are much larger (compare Figs 10 View FIGURE 10 G and 9D).

Presumed differences in number of armature elements on U1, U2 and pleopods ( Fig. 10 View FIGURE 10 A–C) compared to the female are pending confirmation once additional material is eventually collected. Nevertheless, the male pleopod 1 displays a bifid seta proximally on the inner margin of the proximal article of the endopod, whereas this seta is unicuspid in the female (compare Figs 10 View FIGURE 10 A and 8A).