Rhepoxynius variatus (J. L. Barnard 1960)

Rhepoxynius variatus (J.L. Barnard)

Paraphoxus variatus J.L. Barnard, 1960:198–202, pls. 3, 4; 1964b:245; 1966a:90; 1966b:30.

Description of Female (female “n,” 3.21 mm).—Head about 17 percent of total body length, greatest width about 72 percent of length, rostrum constricted, narrow, elongate, exceeding apex of article 2 on antenna 1. Eyes small, clear of pigment, ommatidia ordinary. Article 1 of peduncle on antenna 1 about 1.3 times as long as wide, about 2.2 times as wide as article 2, ventral margin with about 4 setules, weakly produced dorsal apex with 2 setules-setae, article 2 about 0.65 times as long as article 1, with widely spread ventral row of 8 setae, and 2 midlateral setae; primary flagellum with 7 articles, about 0.55 times as long as peduncle, bearing 1 short aesthetasc on articles 3–6; accessory flagellum with 6 articles. Antenna 2 strongly ensiform; article 3 lacking dorsal spine; spine formula of article 4 = 3–2, dorsal margin with notch bearing 5 setae, ventral margin with 13 groups of 1 long seta each, 1 ventrodistal long spine; article 5 about 0.75 times as long as article 4, facial spine formula = 0, dorsal margin naked, bearing 2 sets of medium setae, ventral margin with 3 sets of 1–2 long to short setae, 3 ventrodistal long to medium spines, 1 set facially; flagellum about 0.85 times as long as articles 4–5 of peduncle combined, with 9 articles.

Epistome with long sharp anterior cusp. Mandibles with weak palpar hump, right incisor narrow, with 3 teeth, third set apicad, left incisor with 4 humps in 2 branches; right lacinia mobilis weakly bifid or with side tooth, distal branch much shorter than proximal, pointed, proximal branch broad, blunt, left lacinia mobilis narrow, with 5 teeth, middle teeth slightly shortened; right rakers 8 plus 2 rudimentaries, left rakers 11 plus 1 rudimentary; molars composed of short bulbous protrusions, right molar with 5–6 primarily medium spines, no spine disjunct, left molar with 4–5 primarily medium spines, no spine disjunct, no molar with plume; palp article 1 short, article 2 without setae, article 3 about as long as article 2, oblique apex with 13 spine-setae, basofacial formula = 0–1 or 0–2. Each outer lobe of lower lip with 1 cone. Inner plate of maxilla 1 especially thin, bearing 1 medium apical pluseta, 1 similar apicomedial seta, 2 apicolateral much shorter setae, palp article 2 with 1 apical spine, 2 apicolateral, 7 apicomedial and 5 submarginal setae. Plates of maxilla 2 extending equally, outer very much broader than inner, outer with 1 apicolateral seta, inner with 2 medial setae. Inner plate of maxilliped with 1 large thick apical spine, 3 apicofacial setae, 4 medial setae, outer plate with 5–6 medial and apical spines, no apicolateral setae or cusp, palp article 1 with 1 apicolateral seta, article 2 with 2 groups of 3 apicolateral setae, medial margin of article 2 moderately setose, article 3 with 8 scattered facial setae, 3 lateral setae, nail of article 4 short, almost fully fused, with 2 accessory setules.

Coxa 1 expanded apically, anterior margin weakly convex, main ventral setae of coxae 1–4 = 6–8–6–5, posteriormost seta of coxae 1–4 slightly shortened, anteroventral setule close to main setae, coxae 2–3 very narrow; anterior and posterior margins of coxa 4 almost parallel, posterior margin almost straight, posterodorsal corner rounded, posterodorsal margin ordinary, concave; width-length ratio of coxa 4 = 11:15.

Gnathopods with very thin hands, moderately setose anteriorly, width ratios on articles 5–6 of gnathopods 1–2 = 27:21 and 26:21, length ratios = 65:48 and 56:43, palmar humps ordinary, palms transverse, short, article 5 of gnathopod 1 elongate, ovate, posterior margin flat, long, article 5 of gnathopod 2 elongate, ovate, posterior margin rounded.

Pereopods 3–4 similar, facial setae formula on article 4 = 7 and 8, aligned parallel to apex, on article 5 = 6 and 4, main spine of article 5 extending to M. 100 (or 90 on pereopod 4) on article 6, article 5 with no proximoposterior spines, spine formula of article 6 = 5 + 6 and 5 + 6 plus no middistal seta, some spines especially long; acclivity on inner margin of dactyls of pereopods 3–4 weak, emergent setule short, midfacial pluseta short. Coxae 5–7 posteroventral seta formula = 2–11–1; articles 4–5 of pereopods 5–6 broad, facial spine rows moderately developed (spines thin), facial ridge formula of article 2 on pereopods 5–7 = 0–1–1. Width ratios of articles 2, 4, 5, 6 of pereopod 5 = 68:60:59:19, of pereopod 6 = 88:55:38:15, of pereopod 7 = 103:24:19:9; length ratios of pereopod 5 = 110:54:50:42, of pereopod 6 = 105:80:47:58, of pereopod 7 = 100:28:28:32; article 2 of pereopod 7 reaching middle of article 4, posterior margin with 3 large teeth; medial and lateral apices of articles 5–6 coarsely combed, lacking digital processes.

Posteroventral corner of epimeron 1 rounded, posterior margin weakly convex, naked, anteroventral margin with 7 short to medium setae, posteroventral margin with 2 long setae parallel to margin or arranged vertically (variable). Posteroventral corner of epimeron 2 rounded, posterior margin weakly convex, naked, ventral marginal setae = 12, none set vertically. Posteroventral corner of epimeron 3 rounded, posterior margin straight, with 3 setae near corner, ventral margin with 5 posterior setae.

Urosomite 1 with lateral setule at base of uropod 1, articulation line almost complete, urosomite 3 unprotuberant dorsally. Rami of uropods 1–2 with articulate but tightly fixed apical nails, rami naked. Peduncle of uropod 1 with 3 basofacial setae and 1 apicolateral spine, medially with 3 widely spread marginal setae and spines, apicalmost an enlarged spine, no displaced spine. Peduncle of uropod 2 with 3 long dorsal spines, medially with 1 large apical spine; apicolateral corners of peduncles on uropods 1–2 without comb. Peduncle of uropod 3 with no ventral spines, dorsally with 1 lateral setule, 1 medial setule, rami feminine, inner extending to M. 30 on article 1 of outer ramus, apex with 1 setule, medial and lateral margins naked, article 2 of outer ramus elongate, 0.30, bearing 2 medium setae, apicomedial margin of article 1 with 1 seta, lateral margin with 2 acclivities, short setal formula = 1–1–1, long setal formula = 1–1–1.

Telson especially long, length-width ratio = 2:1, almost fully cleft, each apex very narrow and pointed, lateral acclivity shallow, narrow, bearing ordinary lateral setule, next seta laterad much longer than setule; midlateral setules diverse, largest medium.

VARIABLES.—See J.L. Barnard (1960). Rostrum broader or narrower; hands of gnathopods broader or narrower; teeth on article 2 of pereopod 7 larger or smaller; posterior facial setae on epimeron 1 horizontal or vertical; rami of uropods 1–2 naked or with 1 spine each except inner ramus of uropod 2; setal elements on each telsonic lobe alternative, lateralmost either shortest or longest.

MATERIAL.—AHF Velero IV 5973, southern California, 17 m, female “n,” 3.21 mm (illus.), female “o,” 3.22 mm, and 4 other specimens. Data not cited as sample within middle of species range.

RELATIONSHIP.—This species belongs to the variatus-fatigans-daboius-abronius group with sharp epistomal cusp, lack of displaced medial spine on peduncle of uropod 1, and no other unusual characters such as spikes on pereopod 7 or urosome.

Rhepoxynius variatus differs from its flock members in the absence of vertically placed facial setae on epimeron 2 and generally larger teeth or serrations on article 2 of pereopod 7, though these are variable.

DISTRIBUTION.—Eastern Pacific Ocean from Monterey Bay, California to Bahía San Ramon, Baja California, 5–93 m.