Hyalella cajasi, Alonso, Miguel & Jaume, Damia, 2017

Alonso, Miguel & Jaume, Damia, 2017, A new species of Hyalella from the High Andes of Ecuador (Crustacea, Amphipoda, Hyalellidae), ZooKeys 686, pp. 1-13 : 1-2

Hyalella cajasi sp. n. Figs 1, 2, 3, 4, 5

Material examined.

All collected by Henrietta Hampel at Cajas National Park (Azuay Province; southern Ecuador), 5th May 2015. Laguna Togliacocha (S2°47'55.90"; W79°15'02.13"); 3,859 m a.s.l. HOLOTYPE: male 9.0 mm, preserved in formaldehyde vial. PARATYPES: Five males and 5 females in formaldehyde vial. Holotype and paratypes registered under same registration number [MECN-SI-Cal-0003]. Laguna Cardenillo (S2°46'54.32"; W79°14'50.48"); 4,103 m a.s.l. Four males and 6 females. Small laguna between Laguna Cardenillo and La Negra (S2°47'04.21"; W79°14'50.90"); 4,076 m a.s.l. Nine males and 8 females. Laguna Azul (S2°47'17.81"; W79°14'46.19"); 4,043 m a.s.l. Five males and 5 females. Small laguna close to La Larga (S2°47'35.70"; W79°14'44.08"); 3,954 m a.s.l. Ten males and 9 females. Pool close to Laguna Luspa (S2°47'54.04"; W79°15'46.94"); 3,868 m a.s.l. Ten males and 10 females. Laguna Illincocha (S2°46'46.59"; W79°13'51.33"); 3,986 m a.s.l. One male and 4 females.

Diagnosis.

Body smooth, non-processiferous. Eyes normal. Antenna 1 much shorter than antenna 2. Incisor of mandibles multi-denticulate. Palp of maxilla 1 short, reaching to less than half distance between its insertion and distal margin of outer lobe, crowned with short robust seta. Inner lobe of maxilla 2 with two pappose setae proximally on medial margin. Coxal plate IV deeply excavated posteriorly. Six pairs of sternal gills, on pereionites II to VII. Uropod 1 sexually dimorphic, with male exhibiting a modified robust seta ("copulatory spine" sensu Bousfield 1996) on endopod; modified robust seta hardly curved and only just surpassing tip of endopod. Ramus of uropod 3 shorter than protopod. Telson broader than long, with distal margin evenly rounded; distal armature arranged as a single row of robust setae.

Etymology.

Species name refers to Cajas National Park (Azuay Province; southern Ecuador), the type locality.

Description of male.

Body (not figured) up to 9.0 mm long, strongly pigmented, virtually black, smooth. Head (Fig. 1A) shorter than pereionites I and II combined; rostrum wanting; lateral lobes truncate; postantennal sinus shallow and broad. Eyes small, round, located behind insertion of antenna 1. Epimeral plates (Fig. 1C) each with unarmed distal margin; plates II–III posterodistally acuminate with posterodistal angle strongly produced, subacute; posterior margin of plates with several tiny tooth-like projections each provided with short setule.

Antenna 1 (Fig. 1A) much shorter than antenna 2 although longer than peduncle of latter; peduncle longer than head, segments 1-3 relative length as: 1: 1: 0.8; main flagellum longer than peduncle; accessory flagellum absent. Pair of aesthetascs present on distomedial angle of posterior margin of middle articles of flagellum (Fig. 1B).

Antenna 2 (Fig. 1A) peduncle segments 4-5 relative length as: 0.7: 1.

Labrum (not figured) ordinary. Paragnaths (= lower lip; not figured) inner lobes absent.

Mandibles each with well-developed, triturative columnar molar; molar seta equally developed in both mandibles; palp lacking. Left mandible (Fig. 2A) incisor 7-denticulate; lacinia 5-denticulate. Right mandible (Fig. 2B) incisor 6-denticulate; lacinia complex, with 5 main cusps and multiple denticles, and with patch of short setules proximally on medial surface.

Maxilla 1 (Fig. 2C) inner lobe finger-like, crowned with two pappose setae; outer lobe with nine serrated stout robust setae distally; palp reduced, unsegmented, reaching to less than half distance between its insertion and distal margin of inner lobe, tapering with tiny conical robust seta on tip.

Maxilla 2 (Fig. 2D) inner lobe with two unequal pappose setae proximally on inner margin, proximal-most seta largest, hyperthophied.

Maxilliped ordinary; basal endite (= inner plate) (Fig. 2E) subrectangular with three flattened triangular short cuspidate robust setae distally and row of pappose setae along medial margin.

Coxal gills (Figs 3E; 4 A–D) on gnathopod 2 to pereiopod 6, smooth, unstalked, sac-like. Sternal gills on pereionites II to VII, finger-like (Fig. 4F), placed antero-laterally at each side on corresponding sternite.

Gnathopod 1 (Fig. 3 A–D) subchelate. Carpus longer than propodus. Propodus 1.5 times as long as broad, with concave posterior margin; palm margin evenly convex; palm angle with two short flagellate robust setae subequal in length on medial side (Fig. 3C). Dactylus with single triangular denticle subdistally on medial margin (Fig. 3D).

Gnathopod 2 (Fig. 3 E–G) subchelate. Propodus massive, broadly expanded, 1.3 times as long as broad with palm length longer than carpal lobe; palm margin longer than posterior margin of segment, convex but sinuous, with continuous row of densely set robust setae along both sides of margin (only row on medial side shown in Fig. 3G); palm angle with two short, reduced flagellate robust setae on medial side. Unguis completely incorporated into dactylus (Fig. 3G).

Pereiopods 3-4 (Fig. 4A, B) similar except for coxal plates. Pereiopod 4 slightly shorter than pereiopod 3, with coxa deeply excavated posteriorly.

Pereiopods 5-7 (Fig. 4 C–E) progressively longer towards posterior. Basis of pereiopod 7 broadest, 1.2 times as long as broad; basis of pereiopod 5 1.3 times as long as broad; basis of pereiopod 6 more slender, 1.5 times as long as broad. All limbs with propodus distinctly longer than their respective carpus.

Pleopods (Fig. 1D) all similar, biramous, rami multi-annulated and provided with long plumose setae; integument of posterior face of protopod (= peduncle) and proximomedial margin of proximal article of endopod, setulose, as figured.

Uropod 1 (Fig. 1E) protopod longer than rami. Armature of protopod consisting of series of 3-4 flagellate robust setae proximally along posterolateral margin, and single flagellate robust seta at each posterodistal and posteromedial angle of segment; posteromedial margin of segment unarmed. Exopod with series of five flagellate robust setae along lateral margin and three robust setae on tip, none of which flagellate; medial margin of segment unarmed. Endopod with four flagellate robust setae along medial margin and three robust setae on tip, none of which flagellate; lateral margin of segment with series of four flagellate robust setae disposed subdistally on margin, of which proximal-most modified, longer than rest, slightly surpassing tip of endopod, slightly curved and complexly denticulate on tip ("copulatory spine" sensu Bousfield 1986; Fig. 1F).

Uropod 2 (Fig. 1G) protopod about as long as rami. Protopod with three flagellate robust setae along posterolateral margin; robust seta present on each posterodistal and posteromedial angle of segment, of which that on posteromedial angle non-flagellate and more slender than counterpart; posteromedial margin of segment unarmed. Exopod with five flagellate robust setae along lateral margin and three robust setae on tip; medial margin unarmed. Endopod with 3-4 flagellate robust setae along medial margin, three robust setae on tip, and three flagellate robust setae disposed subdistally on lateral margin.

Uropod 3 (Fig. 1H) ramus about as long as protopod. Protopod with transverse comb of 3-6 flagellate robust setae on distolateral angle, simple seta on distomedial angle, and isolated reduced simple seta on medial margin. Ramus 2.2 times longer than broad, with short robust seta and a bunch of long simple setae on tip.

Telson (Fig. 1I) broader than long, with distal margin evenly rounded. Armature consisting of continuous marginal series of 4-7 (exceptionally only three) flagellate robust setae distally plus three tiny plumose setae disposed distolaterally at each side.

Description of brooding female.

Differing from male in smaller size (body up to 6.5 mm long); presence of oöstegites on pereionites II-V (Fig. 5A, B); aspect of gnathopod 2 (Fig. 5A), which is similar to male gnathopod 1 but with a more slender propodus (1.7 times as long as broad and attaining 95% length of carpus; versus 1.5 times as long as broad and attaining 89% length of carpus in male gnathopod 1); unequal length of robust setae on palm angle of gnathopod 2 (Fig. 5C); and endopod of uropod 1 with two flagellate robust setae along distolateral margin (versus four in male), of which none modified (Fig. 5D).