Birubius mayamayi Barnard & Drummond 1978

Birubius mayamayi

DESCRIPTION OF FEMALE.—Head about 19 percent of total body length, greatest width about 58–68 percent of length; rostrum unconstricted, broad, reaching or exceeding middle of article 2 on antenna 1. Eyes medium, 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 10 setules, weakly produced dorsal apex with one setule; article 2 about 0.8 times as long as article 1, with ventral cycle of 6 setae; primary flagellum with 9–11 articles, about 0.90 times as long as peduncle, bearing several long aesthetascs; accessory flagellum with 6–8 articles. Spine formula on article 4 of antenna 2 = 1–3–4–4, dorsal margin with notch bearing 3 setae, ventral margin with 5–6 groups of 1–2 long and medium setae, one ventrodistal long spine; article 5 about 0.8 times as long as article 4, facial spine formula = 1–2–2–2 or 1–2–3–2 or 1–2–2–1, dorsal margin bearing 2 setules, ventral margin with 5 sets of 1–2 setae, 2 ventrodistal long spines, one subdistal facial spine; flagellum about 1.3 times as long as articles 4–5 of peduncle combined, with 9–13 articles. Mandibles with weak to medium palpar hump; right incisor with 3 teeth and notch; left incisor with 4 teeth on 2 branches; right lacinia mobilis bifid, distal branch much shorter than proximal, distal branch flabellate, broad, variable, subbifid or denticulate, occasionally with facial humps, proximal branch simple, pointed, with marginal denticles; left lacinia mobilis with 4 teeth plus one accessory tooth, middle teeth slightly shortened; right rakers 8–10; left rakers 9–11; molar in form of elongate plaque, right and left molars with 8–9 primarily long spines, each molar with plume; palp article 1 short, article 2 with one long inner apical seta and 1–3 other similar or shorter inner setae, article 3 about 1.3 times as long as article 2, oblique apex with 8–9 spine-setae, basofacial formula = 1–2. Inner plate of maxilla 1 ordinary, bearing one long apical pluseta, one shorter similar apicomedial seta, 2 apicolateral much shorter setae; palp article 2 with 3–4 apicalmedial marginal spines and 3–5 submarginal setae. Plates of maxilla 2 extending subequally, of subequal breadth, outer with 3–4 apicolateral setae, inner with one medial seta. Inner plate of maxilliped with 2 large thick apical spines, 2–3 apicofacial setae, 3–6 medial setae; outer plate with 10–11 medial and apical spines, 4–6 apicolateral setae; palp article 1 with apicolateral seta, article 2 with one apicolateral seta, medial margin of article 2 moderately setose, article 3 not protuberant, with 4 facial setae, no lateral setae, nail of article 4 long, with 2 accessory setules. Coxa 1 expanded distally, anterior margin straight; main ventral setae of coxae 1–4 = 9–9–7–11, posteriormost seta of coxae 1–3 shortest; anterior and posterior margins of coxa 4 strongly divergent, posterior margin very oblique, weakly convex, posterodorsal corner sharp, posterodorsal margin ordinary, weakly V-shaped, width–length ratio of coxa 4 = 15:16. Long posterior setae on article 2 of gnathopods 1–2 and pereopods 1–2 = (2–3)–3–3–5, plus one long facial on gnathopod 1, long anteriors = 4–(7–9)–0–0, short anteriors = (1–2)–(1–3)–(1–2)–(1–2). Gnathopods generally ordinary, hands slightly broadened; width ratios of articles 5–6 on gnathopods 1–2 = 25:36 and 27:38, length ratios = 65:68 and 59:62; palmar humps ordinary to small, palms oblique; article 5 of gnathopod 1 elongate, ovate, posterior margin rounded; article 5 of gnathopod 2 elongate, ovate, posterior margin rounded. Pereopods 1–2 similar, facial setae formula on article 4 = 5 and 5, on article 5 = 6 and 6 or 5 and 5; main spine of article 5 extending to M. 95 on article 6, article 5 lacking proximoposterior spines; spine formula of article 6 = 4 + 5 or 3 + 4 plus middistal seta, some spines especially long; acclivity on inner margin of dactyls of pereopods 1–2 weak, emergent setule short, midfacial pluseta ordinary. Coxae 5–7 posteroventral setule-seta formula = 7–3–1. Articles 4–5 of pereopods 3–4 of ordinary width, facial spine rows sparse, facial ridge formula on article 2 of pereopods 3–5 = 0–2–2; width ratios of articles 2, 4, 5, 6 of pereopod 3 =40:35:29:15, of pereopod 4 = 57:25:17:8, of pereopod 5 = 80:22:20:7, length ratios of pereopod 3 = 68:28:39:39, of pereopod 4 = 86:45:45:58, of pereopod 5 = 88:25:25:28; article 2 of pereopod 5 almost reaching middle of article 5; medial apex of article 6 finely combed, bearing 5–6 digital processes. Posteroventral corner of epimeron 1 weakly protuberant, posterior margin weakly convex, with 0–3 setules, corner with or without setule, anteroventral margin with 4–5 medium setae, posteroventral margin with 2 long setae; posteroventral corner of epimeron 2 with small rounded or pointed tooth guarded by setule sinus, posterior margin weakly convex, with 2–3 setules, facial setae = 8–11, occasional pair set vertically; posteroventral corner of epimeron 3 rounded, weakly protuberant, with small rounded tooth guarded by setule sinus, posterior margin straight, with 3 setule notches, ventral margin with 2–4 setae evenly spread; epimera 1–3 with large to small seta on posterodorsal margin set in weak notch. Urosomite 1 with ventral setule at base of uropod 1, articulation line complete; urosomite 3 unprotuberant dorsally. Rami of uropods 1–2 with articulate enlarged apical nails, rami of uropods 1–2 lacking accessory nails, outer ramus of uropod 1 with 5–6 dorsal spines, inner with 2–3, outer ramus of uropod 2 with 4 dorsal spines, inner with 1–2 dorsomedial spines; peduncle of uropod 1 with 2 apicolateral spines and 4–5 basofacial setae, medially with 5–6 marginal spines, apicalmost enlarged; peduncle of uropod 2 with 7–9 dorsal spines, medially with one apical spine. Peduncle of uropod 3 with 4–5 ventral spines, dorsally with one lateral spine, 2 medial setules or one spine and one setule; rami submasculine, inner extending to M. 85 on article 1 of outer ramus, apex with 2 setae, medial and lateral margins more or less setose, article 2 of outer ramus short, 0.15–0.22, bearing 2 long setae, medial margin of article 1 with 1–4 setae, lateral margin with 4 acclivities, spine formula = 1–1–1–1–1, setal formula = 1–1–1–1–2. Telson long, length–width ratio = 12:11, almost fully cleft, each apex of medium width, rounded, lateral acclivity broad, shallow, weak, bearing ordinary lateral setule, spine next medial of length equal to or shorter than setule, midlateral setules highly diverse. Cuticle with sparse ordinary bulbar setules of varying sizes mixed with pipes, emergent setules ordinary.



DESCRIPTION OF MALE.—Rostrum and head slightly shorter and narrower than in female. Primary flagellum of antenna 1 with 10–12 articles, one calceolus each on articles 1–6; accessory flagellum with 6–7 articles. Facial spine formula on article 4 of antenna 2 = 3–4–4, of article 5 = 2–2–2 or 2–2, article 5 with 2 dorsal sets of male setae and 1–3 calceoli, ventrodistal apex with 3 setules, flagellar formula = 28, 1–3, 5, 7…27. Article 2 of mandibular palp with 2–3 inner setae, basofacial setal formula on article 3 = 2–2 or 3–2. Article 2 of only pereopod 5 narrower than in female, article 6 and dactyl of pereopod 3 elongate, articles 5–6 narrower than in female, anterior facial ridge of pereopod 5 shortened, article 6 subequal to article 5 in length. Epimera 1–3 broadened; posterior margin of epimeron 3 shortened, posterior setule notches more crowded and sharper than in female; dorsoposterior setule on epimera 1–2 absent, shortened on epimeron 3; setal formulas, epimeron 1 anteroventral = 5, posteroventral = 2, epimeron 2 facial = 9–14, epimeron 3 posterior = 4, ventral = 3–5. Spine formulas of uropods, uropod 1 peduncle apicolateral = 2–4, basofacial = 6–7, medial = 5, uropod 2 peduncle dorsal = 12–16, dorsal spines on outer ramus of uropod 1 = 6–7, of uropod 2 = 5–6, inner ramus of uropod 1 = 2–3, of uropod 2 = 1–2. Telson slightly elongate, distal spines shortened.

VARIATIONS.—The major variant, of subtle distinction, comprises specimens with shorter, apically broader rostrum combined with slightly stouter article 6 of pereopod 4, somewhat narrower hands of gnathopods as illustrated and a spine instead of setules on the apicomedial margin of uropod 3 peduncle. But minor variations occur among other specimens in lengths of spines on article 6 of pereopods 1–2, dorsal outline of head and wide variations in setal and spine counts on epimera and uropods and especially in the form of the right lacinia mobilis (as illustrated). Loss of pigment occurs in the eyes of various specimens, after prolonged exposure to formaldehyde, especially in those of the “major variant” noted above.

Botany Bay Variants: Five out of six specimens from New South Wales in EBS 304 and 311, differ from Victorian material in the absence of a dorsomedial spine on the inner ramus of uropod 2; one specimen, female “p” of EBS 311 bears this spine. Female “v” of that sample is unusual in that the 2 posterofacial setae on epimeron 2 are set horizontally, not vertically. Female “v” is illustrated as voucher material to demonstrate that, despite minor differences, the Botany Bay material belongs with B. mayamayi. Unillustrated parts are described as follows: setal and spine formula of articles 4, 5, 6 of pereopod 2 = (4–5)–6–(4 + 4); head about 19 percent of total body length; view of upper lip shown from oblique dorsal aspect; coxae and mandibles as in Victorian material; flagellum of antenna 2 with 12 articles, 1.45 times as long as articles 4–5 of peduncle together. The posteroventral tooth on epimeron 2 is smaller and sharper in Botany Bay material than in the majority of Victorian specimens.

Male “u” of EBS 304: Article 4 of antenna 2 with spine formula of 3–4–3, and on article 5 = 2–2.

HOLOTYPE.—NMV, female “z,” 4.78 mm.

TYPE-LOCALITY.—PPBES 902/5, 21 Sep 1970, Port Phillip Bay, Victoria, Australia, 10 m, sandy silt.

VOUCHER MATERIAL.—Illustrated: PPBES 902/2: male “b,” 4.60 mm; female “g,” 4.72 mm; female “h,” 4.75 mm. PPBES 977/4: male “c,” 4.61 mm. PPBES 977/2: female “f,” 4.2 mm. PPBES 961/1:male “d,” 4.10 mm. PPBES 964/4: male “e,” 4.70 mm. PPBES 983/5: female “i,” 4.2 mm; female “j,” 4.40 mm. PPBES 951/2: female “k,” 4.50 mm. PPBES 959/5: female “l,” 4.60 mm. PPBES 938/5: juvenile “m,” 3.50 mm; juvenile “n,” 3.30 mm. CPBS 03N/2: female “a,” 4.9 mm; female “w,” 4.3 mm. CPBS C6/3: female “y,” 4.65 mm. EBS 304: female “v,” 4.92 mm; female “s,” 4.64 mm.

Not Illustrated: EBS 311: female “p,” 4.48 mm, EBS 304: male “u,” 3.94 mm.

RELATIONSHIP.—This species and species 12–15 differ from the B. panamunus group (1–10) in the absence of accessory apical nails on uropod 1. Birubius mayamayi forms the model to which species 12–15 are compared.

Because B. mayamayi retains an unconstricted rostrum and bears a fully developed posterodorsal setule on epimeron 3 the direct relationship to any of species 1–10 appears to be remote. Only B. panamunus (1) retains the unconstricted rostrum but lacks the epimeral setule. Both B. mayamayi and B. panamunus have setose coxa 4 but epimeron 3 of B. mayamayi is distinct in other ways, such as reduction of tooth, loss of facial setae and development of posteroventral setules.

MATERIAL.—PPBES, 104 samples from 43 stations (169); CPBS, 5 samples from 5 stations (8); EBS, 11 samples from 11 stations (20).

DISTRIBUTION.—Victoria: Port Phillip Bay and Western Port, 2–23 m, sand, clay, silty sand, sandy silt, silty clay, clayey silt. New South Wales, Botany Bay, Towra, 1–3 m, sand, Zostera.