Pseudelasmopus walkerae, Hughes, Lauren E., 2015

Hughes, Lauren E., 2015, Maeridae from the Indo-Pacific: Elasmopus, Leeuwinella gen. nov., Maeropsis, Pseudelasmopus and Quadrimaera (Amphipoda: Crustacea), Zootaxa 4059 (2), pp. 201-256 : 227-230

Pseudelasmopus walkerae sp. nov.

( Figs 26–28 )

Type material. Holotype male, 3 mm, dissected, 4 slides, AM P.92517, Emily Bay, Norfolk Island, 29°3'36"S, 167°57'12"E, 3.7 m, airlift, rubble on sand, 20 May 2008, coll. R.T. Springthorpe, MI NFK 82.

Paratypes: 1 specimen, AM P.92518, Emily Bay, Norfolk Island, 29°3'36"S, 167°57'12"E, 3.7 m, airlift, rubble on sand, 20 May 2008, coll. R.T. Springthorpe MI NFK 82; 8 specimens, AM P.92522, Emily Bay, Norfolk Island, 29°3'36"S, 167°57'12"E, 3.7 m, airlift, rubble on sand, 20 May 2008, coll. R.T. Springthorpe, MI NFK 82; 1 specimen, AM P.92519, Emily Bay, Norfolk Island, 29°3'36"S, 167°57'12"E, 3.7 m, airlift, rubble and algae, 20 May 2008, coll. R.T. Springthorpe, MI NFK 84; 1 specimen, AM P.92521, Swiss cheese reef, Norfolk Island, 29°00'23"S, 167°56'50"E, 12 m, airlift, under overhang, vertical face encrusted with sponges, coll. 15 May 2008, coll. R.T. Springthorpe, MI NFK 37; 5 specimens, AM P.92520, east of Sail Rock, Phillip Island, near Norfolk Island, 29°6'54"S, 167°57'31"E, 14.8 m, airlift, under stones, rubble, 14 May 2008, coll. R.T. Springthorpe MI NFK 20; 16 specimens, AM P.92523,east of Sail Rock, Phillip Island, near Norfolk Island, 29°6'54"S, 167°57'31"E, 13 m, airlift, under stones, 14 May 2008, coll. R.T. Springthorpe, MI NFK 22.

Type locality. Emily Bay, Norfolk Island, South Pacific, 29°3'36"S, 167°57'12"E.

Etymology. Named in honour of Wendy Walker, the zoological technician who performed the preliminary microscope processing of the Norfolk Island samples and has been a regular volunteer in the Australian Museum Marine Invertebrates section for over 20 years.

Description. Of holotype male, 3 mm, AM P.92517.

Head. Eyes round; lateral cephalic lobe broad, apically rounded, anteroventral margin with notch/slit, anteroventral corner rounded. Antenna 1 longer than antenna 2; peduncular article 1 length1.1 × article 2, without robust setae on posterior margin; peduncular article 2 longer than article 3; flagellum articles longer than broad, with 17 articles; accessory flagellum short, less than half length of primary flagellum, with 2 articles. Antenna 2 peduncular article 4 longer than article 5; flagellum with 9 articles. Mandible accessory setal row, well developed with 5 setae; palp well developed, article 1 length 1.5 × width, shorter than article 2, inner margin not distally produced; article 2 length subequal to article 3, with long slender setae; article 3 falcate, twice as long as broad, with well-developed setal comb. Lower lip without apical ducts, mandibular lobes subacute. Maxilla 1 inner plate with medial setal row; outer plate palp, 2 articulate slender, article 2 with 4 apical slender setae.

Pereon. Gnathopod 1 coxa anterior margin straight, anteroventral corner not produced, broadly rounded, ventral margin without robust setae, posteroventral corner without notch; basis anterodistal corner subquadrate; ischium anterodistal corner without lobes; merus with posteroventral corner subacute; carpus length 1.8 × width, subequal to propodus length, anterior margin with a few long slender setae, posterior margin lined with long slender setae, without dense rows of setae covering medial surface; propodus subovate, medial surface setal comb absent, palm subacute, straight, entire, lined with short robust setae, palm with weakly defined corner and no robust setae; dactylus posterior closing along palm, unguis present.

Gnathopod 2 symmetrical, subchelate; coxa posteroventral corner without notch, ventral margin without robust setae; basis slender, anterodistal corner subquadrate; ischium anterodistal corner without lobes; merus posteroventral corner acute; carpus compressed, length 0.7 × width, anterior margin with 1 slender seta, posterior margin with rows of slender setae; propodus subovate, length 1.4 × width, posterior margin with clusters of long slender setae, palm length half of propodus posterior margin, angle subacute, distal shelf absent, palm smooth, entire, defined by posteroventral corner with small subacute tooth androbust seta; dactylus reaching end of and closing along palm, posterior margin smooth, unguis absent. Pereopods 3–4 coxa subquadrate; basis long, length 3.5 × width; merus, carpus and propodus not broadened; dactylus unguissimple.

Pereopods 5–7 basis slender posterior margin straight;merus, carpus and propodus slender, margins lined with long slender setae; dactylus unguis simple.

Pleon. Pleonites 1–3 dorsally smooth. Epimera 1–3 posterior and ventral margins smooth, posteroventral corner with subacute to acute tooth. Urosomite 1 dorsally smooth. Uropod 1 peduncle with 1 basofacial seta, without interramal spur, peduncle length 0.8 × outer ramus; inner ramus subequal to outer ramus length. Uropod 2 peduncle length 0.9 × outer ramus; inner ramus slightly shorter than outer ramus. Uropod 3 peduncle 0.8 × inner ramus; inner ramus subequal to outer ramus, length twice width, apically rounded, without lateral setae, with apical long slender setae. Telson broader than long, deeply cleft (80%), lobes abutting, tapering distally, lobes apically convex, each lobe with2 short slender apical setae.

Remarks. Pseudelasmopus walkerae sp. nov. has a subchelate gnathopod 2 distinguishing it from P. cheliferus Ledoyer, 1978 of Mauritius which has a chelate gnathopod. Other characters that separate these species include the smooth posterior margin of pereopods 5–7 and the much longer than broad uropod 3 rami in P. walkerae sp. nov. The telson is well developed in P.walkerae sp. nov. unlike that of P. cheliferus in which the telson is vestigial and reduced as two small lobes. This is only the second species described from this fascinating genus. See also generic remarks for Pseudelasmopus .

Distribution. South Pacific Ocean: Tasman Sea: Norfolk Island (current study).

Figures

FIGURE 26. Maeropsis griffini (Berents, 1983) female, 6.5 mm, NTM Cr 18333, Bedout Island, Western Australia, scales 0.1 mm.

FIGURE 27. Pseudelasmopus walkerae sp. nov. holotype male, 3 mm, AM P. 92517, Emily Bay, Norfolk Island, scales 0.1 mm.

FIGURE 28. Pseudelasmopus walkerae sp. nov. holotype male, 3 mm, AM P. 92517, Emily Bay, Norfolk Island, scales 0.1 mm.