Birubius muldarpus

Birubius muldarpus

DESCRIPTION OF FEMALE.—Head about 21 percent of total body length, greatest width about 60 percent of length; rostrum slightly constricted, narrow, not reaching middle of article 2 on antenna 1. Eyes large, largely occluded with pigment. Article 1 on peduncle of antenna 1 about 1.3 times as long as wide, about twice as wide as article 2, ventral margin with about 11 setules, weakly produced dorsal apex with 3 setules; article 2 about 0.73 times as long as article 1, with ventral cycle of 7 setae; primary flagellum with 9–10 articles, about as long as peduncle, lacking aesthetascs; accessory flagellum with 7–8 articles. Spine formula on article 4 of antenna 2 = 1–3–4–3, dorsal margin with notch bearing 3 setae, ventral margin with 4–5 groups of 1–4 long to medium setae, one ventrodistal long spine; article 5 about 0.75 times as long as article 4, facial spine formula = 1–2–1, 1–2–0, or 1–2–2, dorsal margin naked, ventral margin with 3 sets of 1–2 long to short setae, 2 ventrodistal long to medium spines and setae; flagellum about 1.4 times as long as articles 4–5 of peduncle combined, with 11 articles. Mandibles with medium palpar hump; right incisor with 3 teeth and accessory tooth; left incisor with 4 humps in 2 branches; right lacinia mobilis bifid, distal branch little shorter than proximal, distal branch flabellate, denticulate, proximal branch simple, pointed, with 2 facial humps; left lacinia mobilis with 4 teeth, middle teeth shortened; right rakers 9, plus one rudimentary; left rakers 9; molar in form of bulbous hump demarcated mainly by spines, molars with 4–5 primarily long spines, plus one weakly disjunct, each molar with plume; palp article 1 short, article 2 with one short inner apical seta and 2 other shorter inner setae, article 3 about as long as article 2, oblique apex with 9 spine-setae, basofacial formula = 1 + 1. Inner plate of maxilla 1 ordinary, bearing one long apical pluseta, one similar apicomedial seta, 2 apicolateral much shorter setae; palp article 2 with 4 apicomedial marginal spines and 3 submarginal setae. Plates of maxilla 2 extending equally, outer slightly broader than inner, outer with 3 apicolateral setae, inner with one medial seta. Inner plate of maxilliped with 2 large, thick, apical spines, 3 apicofacial setae, 3 medial setae; outer plate with 6 medial and apical spines, 2 apicolateral setae; palp article 1 with one apicolateral seta, article 2 with 4 apicolateral setae, medial margin of article 2 moderately setose, article 3 weakly protuberant, with 3 facial setae, 2 lateral setae, nail of article 4 long to medium, with 2 accessory setules. Coxa 1 expanded distally, anterior margin weakly concave; main ventral setae of coxae 1–4 = (5–7)-(5–7)-(4–7)-0, posteriormost seta of coxae 1–2 shortest (or aberrantly long on coxa 3); anterior and posterior margins of coxa 4 almost parallel, posterior margin convex, posterodorsal corner sharply rounded, posterodorsal margin short, concave, width-length ratio of coxa 4 = 19:22; long posterior setae on article 2 of gnathopods 1–2 and pereopods 1–2 = (1–2)—3—(2–3)–3, short anteriors = (2–3)-(2–3)-(2–3)-(1–2), long anteriors = (2–4)-(5–6)-0–0, no others. Gnathopods ordinary; width ratios of articles 5–6 on gnathopods 1–2 = 26:35 and 26:35, length ratios = 67:63 and 60:58; palmar humps small, palms oblique; article 5 of gnathopod 1 elongate, ovate, posterior margin almost flat; article 5 of gnathopod 2 ovate, posterior margin almost flat. Pereopods 1–2 similar; facial setae formula on article 4 = 3 and 3, on article 5 = 4 and 5; main spine of article 5 extending to M. 80 on article 6, article 5 with 2 proximoposterior spines: spine formula of article 6 = 3–4 and 4–5 plus middistal seta; acclivity on inner margin of dactyls of pereopods 1–2 sharp, produced as tooth, emergent setule long, midfacial pluseta short. Coxae 5–7 posteroventral setule formula = 1–1–1. Articles 4–5 of percopods 3–4 medium broad, facial spine rows moderately developed, facial ridge formula on article 2 of pereopods 3–5 = 0–2–2; width ratios of articles 2, 4, 5, 6 of pereopod 3 = 41:40:35:17, of pereopod 4 = 64:37:25:13, of pereopod 5 = 78:24:22:11, length ratios of pereopod 3 = 70:27:36:41, of pereopod 4 = 80:47:37:50, of pereopod 5 = 100: 26:21:27; article 2 of pereopod 5 slightly exceeding apex of article 4; medial apex of article 6 bearing 5 digital processes. Posteroventral corner of epimeron 1 rounded, posterior margin weakly convex, anteroventral margin with 2–4 medium setae, posteroventral face with 2 long setae; posteroventral corner of epimeron 2 weakly protuberant, posterior margin convex, facial setae = 7–9; posteroventral corner of epimeron 3 weakly protuberant, with setule sinus, posterior margin almost straight, face with crescent of 3–6 setae near ventral posterior margin; epimeron 3 with setule on posterodorsal margin. Urosomite 1 naked, articulation line complete; urosomite 3 weakly protuberant dorsally. Rami of uropods 1–2 with articulate enlarged apical nails, inner ramus of uropod 1 with two accessory nails, outer ramus of uropod 1 with 3–4 dorsal spines, inner with one, outer ramus of uropod 2 with 2 dorsal spines, inner with one circular dorsomedial spine; peduncle of uropod 1 with 2 apicolateral spines and 2 basofacial setae, medially with 3 marginal setae and spines, apicalmost an enlarged spine; peduncle of uropod 2 with 5–7 dorsal spines, medially with one small apical spine. Peduncle of uropod 3 with 6 ventral spines, dorsally with one lateral spine, one medial setule; rami submasculine,line, inner extending to M. 80 on article 1 of outer ramus, apex with 2 setae, medial margin with 3 setae, lateral margin naked, article 2 of outer ramus short, 0.14, bearing 2 long setae, medial margin of article 1 with 2 setae, lateral margin with 3 acclivities, spine formula = 1–1–1–1 or 2–1–1–1, setal formula = 1–1–1–2 or 0–1–1–1. Telson ordinary, length-width ratio = 5:4, not fully cleft, each apex wide, rounded, lateral acclivity shallow, weak, bearing long lateral setule, spine next medial shorter than setule, midlateral setules equal on holotype, diverse in other specimens. Cuticle with ordinary bulbar setules mixed with pipes, surface lacking fine striations.

OBSERVATIONS (female).—Female “c”: Setal formulae of article 4 on pereopods 1–2 = 3 and 3, of article 4 = 4 and 5, spine rows of article 6 = 3 and 5 plus seta; this specimen better developed than holotype except in outer ramus of uropod 3 and peduncle of uropod 2, the high counts of spines and setae on various appendages in the description mainly originating from this specimen.

DESCRIPTION OF MALE.—Rostrum slightly longer and narrower than in female. Article 2 of antenna 1 with 5 ventral setae; primary flagellum with 10 articles, one calceolus each on articles 1–6, aesthetascs poorly developed or absent; accessory flagellum with 7 articles. Facial spine formula on article 4 of antenna 2 = 0–3–3–3, on article 5 = 2, article 5 with 3 dorsal sets of male setae and 2 calceoli, ventrodistal apex with 2 thin spines; flagellar formula = 26, 2, 3, 5, 7…25. Right rakers 8 plus 1–2 rudimentaries; left rakers 9; molars with 6 spines plus one disjunct spine more strongly separated than in female; basofacial setal formula of article 3 on mandibular palp = 2–1. Palp of maxilla 1 with 5 spines and 4 setae. Palp article 3 of maxilliped with 4 facial setae. Coxa 4 like that of female but smaller in relation to coxa 1; ventral setal formula of coxae 1–4 = (6–7)-6–5–0. Long posterior setae on article 2 of gnathopods 1–2 and pereopods 1–2 = 1–(1–2)–2–2, long anteriors = 4–(5–6)-0–0, short anteriors = 2–2–2–2, no others. Facial and setal spine formulas of pereopods 1–2 on article 4 = 4 and 3, on article 5 = 5 and 5, on article 6 = 3 + 5 plus middistal seta. Article 2 of only pereopod 5 narrower than in female, pereopod 4 slightly larger relative to pereopod 3 than in female, pereopod 5 much larger, pereopod 5 with special spine on article 5. Epimera 1–3 broadened, posterior margin of epimeron 3 shortened; setal formulas, epimeron 1 anteroventral = 3, posteroventral = 2, epimeron 2 facial = 6, epimeron 3 posterior = 2 setules, facial = 6. Spine formulas of uropods, uropod 1 peduncle apicolateral = 3, basofacial = 4, medially = 4 spines and setae, uropod 2 peduncle dorsal = 13; dorsal spines on outer ramus of uropod 1 = 4, of uropod 2 = 3, inner ramus of uropod 1 = 1, of uropod 2 = 1, ventral spines on peduncle of uropod 3 = 7, spine formula on article 1 of outer ramus = 1–1–2–2–2–2, setal formula = 1–1–1–1–1–1. Telson not elongate, distal spines not shortened.

ILLUSTRATIONS.—Palp of maxilla 1 fully flattened in illustration; epimeron 1 of male heavily damaged and illustration omitted.

HOLOTYPE.—AM, female “a,” 3.50 mm.

TYPE-LOCALITY.—SBS DIS4, 17 May 1972, off Malabar, New South Wales, Australia, 31 m, coarse sand.

VOUCHER MATERIAL.—Type-Locality: juvenile “b,” 2.70 mm. SBS D2S5: female “c,” 3.39 mm (illus.). EBS 20: male “n,” 3.64 mm (illus.); female “e,” 2.97 mm.

RELATIONSHIP.—From the B. cartoo-thalmus (7–8) group, B. muldarpus differs in the smaller tooth and absence of midposterior setules on epimeron 3, the absence of a midfacial ridge on article 2 of pereopod 3 and the shorter wrists of the gnathopods.

Birubius muldarpus differs from the B. myalluskareus (4–5) group in the absence of fully facial setae on epimeron 3 and from B. myallus in addition by the smaller protrusion on epimeron 3. From B. panamunus (1) and B. apari (6), B. muldarpus differs in the smaller tooth on epimeron 3 and the absence of a midfacial row of setae on epimeron 3.

The absence of long setae on coxa 4 differentiates B. muldarpus from B. lorus (2) and B. nammuldus (3).

Birubius yorlunus (31) has a simple right lacinia mobilis and fully facial setae on epimeron 3.

See comments with B. thalmus about the possibility of conspecificity.

MATERIAL.—SBS, 4 samples (4); EBS, one sample (1).

DISTRIBUTION.—New South Wales: off Malabar, 31–49 m, sand and shell frags.; Jervis Bay, Murray's Beach, 6 m, Zostera.