Elasmopus tibarensis, Hughes, 2015

Hughes, L. E., 2015, Ampithoidae and Maeridae Amphipods from Timor-Leste (Crustacea: Peracarida), Records of the Australian Museum 67 (3), pp. 83-108 : 92-94

Elasmopus tibarensis sp. nov.

Figs 10–12

Type material. Holotype male, 8.0 mm, dissected, 4 slides, AM P.90521, off Tibar, west of Dili, (8°33'48" S 125°28'31" E), 10–12 m, on outer side of reef, rubble and sandy reef slope coral rubble and mixed algae, coll. A. Murray, 21 September 2012 ( TM 2012-037); paratype female, 5.0 mm, dissected slides, AM P.90522, off Tibar, west of Dili, (8°33'48" S 125°28'31" E), 10–12 m, on outer side of reef, rubble and sandy reef slope coral rubble and mixed algae, coll. A. Murray, 21 September 2012 ( TM 2012-037); paratype female, AM P.90520, off Tibar, west of Dili, (8°33'48" S 125°28'31" E), 10–12 m, on outer side of reef, rubble and sandy reef slope coral rubble and mixed algae, coll. A. Murray, 21 September 2012 ( TM 2012-037); paratype male, AM P. 90519, 300 m off Jesus Backside Beach, east of Cape Fatucama, (8°31'16" S 125°36'46" E), 12 m, red and green algae, coll. L.E. Hughes, 19 September 2012 ( TM 2012-019) .

Type locality. Off Tibar, west of Dili, Timor-Leste (8°33'48" S 125°28'31" E) .

Etymology. Named from the type locality.

Diagnosis. Antenna 1 peduncular article 1 with 1 robust seta on posterior margin; accessory flagellum minute, with 2 articles. Mandible accessory setal row with row 3 setae; palp, article 3 long, 4 times as long as broad. Coxa 1–3 posteroventral corner with 1 robust seta; propodus medial surface setal comb absent, anterior margin with rows of long slender setae, palm defined by posterodistal corner with 5 robust setae, posterior margin with row of large robust setae along. Gnathopod 2 merus acutely produced distoventrally; propodus expanded, rectolinear, posterior margin with clusters of long, slender setae, without medial setal bunch, palm acute concave, sculptured, 0.4 times length of propodus, distomedial shelf subquadrate, with group of 2 robust setae on shelf, palmar margin with distal subquadrate tooth, sparse robust setae, broadly rounded corner with 1 robust seta; Pereopods 5–6 basis slightly expanded, posterior margin straight, serrate without long slender setae. Pereopod 7 basis posterior margin convex, serrate, without long slender setae, posteroventral corner broadly rounded. Epimeron 2 ventral margin smooth with 3 robust setae, posteroventral corner with small acute tooth. Epimeron 3 ventral margin smooth, lined with short robust setae, posteroventral corner with small acute tooth. Uropod 3 rami distally truncated, with long and short apical robust setae; inner ramus long, length 2.5 times breadth, subequal in length to outer ramus. Telson as long as broad, moderately cleft (66%), lobes abutting, tapering distally, each lobe with long rounded inner and shorter subacute outer apical cusp, with 2 short apical robust setae, with 2 pair of lateral plumose setae.

Description. Based on holotype male, 8.0 mm, AM P. 90521.

Head. Eyes well developed, ovate; lateral cephalic lobe broad, truncated, anteroventral margin with notch/slit, anteroventral corner rounded. Antenna 1 longer than antenna 2; peduncular article 1 subequal in length to article 2, with 1 robust seta on posterior margin; peduncular article 2 longer than article 3; primary flagellum articles as long as broad, with 20 articles; accessory flagellum minute, with 2 articles. Antenna 2 peduncular article 2 cone gland not reaching to end

of peduncular article 3; article 4 subequal in length to article 5; flagellum with 9 articles. Mandible incisor asymmetrical; cuspidate margin; accessory setal row with row 3 setae; molar well developed, triturative; palp, well developed, 3-articulate; article 1 twice as long as broad, shorter than article 2; article 2 subequal to article 3, with many slender setae; article 3 strongly falcate, long, 4 times as long as broad, with apical setae and a comb of short robust setae along anterodistal margin. Lower lip inner lobes present, outer lobes without ducts. Maxilla 1 inner plate subquadrate, with 2 apical plumose setae. Maxilliped palp propodus with small distomedial flap.

Pereon. Gnathopod 1 coxa anterior margin concave, anteroventral corner slightly produced, rounded, posteroventral corner with 1 robust seta, without notch; merus without posterodistal tooth; carpus twice as long as broad, subequal in length to propodus; propodus subchelate, medial surface setal comb absent, anterior margin with rows of long slender setae, palm subacute, convex, entire, minutely serrate, lined with robust setae, defined by posterodistal corner with 2 robust setae, posterior margin with row of large robust setae along; dactylus closing along and reaching end of palm. Gnathopod 2 coxa posteroventral corner with 1 robust seta, notch absent; basis slender, anterior margin without setae, basis anterodistal corner subquadrate, without robust setae; ischium without lobes; merus acutely produced distoventrally; carpus compressed, lobate, projecting between merus and propodus, length subequal to breadth, anterior margin without setae; propodus expanded, rectolinear, anterior margin with several short robust setae, posterior margin with clusters of long, slender setae, without medial setal bunch, palm acute concave, sculptured, 0.4 times length of propodus, distomedial shelf subquadrate, with group of 5 robust setae

on shelf, palmar margin with distal subquadrate tooth, sparse robust setae, subpalmar surface smooth, broadly rounded corner with 1 robust seta; dactylus with 1 seta on anterior margin, without posteroproximal shelf, posterior margin smooth, closing along and reaching end of palm, apically subacute. Pereopod 3 coxa posteroventral corner with 1 robust seta. Pereopods 5–6 basis slightly expanded, posterior margin straight, serrate without long slender setae, posteroventral corner subquadrate; carpus and propodus without long, slender setae along anterior margin; dactylus unguis simple. Pereopod 7 basis posterior margin convex, serrate, without long slender setae, posteroventral corner broadly rounded; carpus and propodus with a few long slender setae along posterior margin.

Pleon. Epimeron 1 ventral margin smooth, posteroventral corner with small acute tooth. Epimeron 2 ventral margin smooth with 3 robust setae, posteroventral corner with small acute tooth. Epimeron 3 ventral margin smooth, lined with short robust setae, posteroventral corner with small acute tooth. Uropod 1 peduncle with 1 basofacial seta; inner ramus slightly longer than outer ramus. Uropod 2 inner ramus slightly longer than outer ramus. Uropod 3 rami distally truncated, with long and short apical robust setae; inner ramus long, length 2.5 times breadth, subequal in length to outer ramus, longer than peduncle. Telson as long as broad, moderately cleft (66%), lobes abutting, tapering distally, each lobe with long rounded inner and shorter subacute outer apical cusp, with 2 short apical robust setae, with 2 pair of lateral plumose setae.

Remarks. The presence of a robust setae on the ventral margin of coxa 1 to 3 is presently unique to E. tibarensis sp. nov. The only other Elasmopus species known to have robust setae on the coxae is E. pseudaffinis Schellenberg, 1938, which has 3 robust setae on the posterior margin of coxa 1.

The elongate article 3 of the mandibular palp aligns E. tibarensis sp. nov. with the pragmatic E. delaplata group (Hughes, 2011) which includes 15 species: E. aduncus Myers, 1995; E. alalo Myers, 1986; E. balkomanus Thomas and Barnard, 1988; E. bollonsi Chilton, 1915; E. delaplata

Stebbing, 1888; E. hawaiensis Schellenberg, 1938; E. karamani Souza-Filho and Senna, 2009; E. neglectus Chilton, 1915; E. piikoi J. L. Barnard, 1970; E. shepherdi sp. nov.; E. slatyeri Lowry & Hughes, 2009; E. thomasi Ortiz and Lalana, 1994; E. varanocephalensis Lowry & Hughes, 2009; E. wahine J. L. Barnard, 1972b and E. woodjonesi Hughes, 2011. Of these species, in only E. alalo and E. tibarensis sp. nov. the gnathopod 2 propodus palm of males lack a dense brush of setae.

Elasmopus tibarensis sp. nov. is most similar to E. alalo in the sculpturing and setation of the male gnathopod 2 palm. Elasmopus tibarensis sp. nov. has short rami on uropod 3 and pereopods 5 to 7 with serrate posterior margins, these character states separate it from E. alalo (which has elongate uropod 3 rami and smooth pereopod margins).

Distribution. Timor-Leste: Tibar, Cape Fatucama (current study).

Figures

Figure 10.Elasmopus tibarensis sp.nov., holotype male, 8.0 mm, AM P.90521, Tibar, west of Dili.

Figure 11. Elasmopus tibarensis sp. nov., holotype male, 8.0 mm, AM P.90521, Tibar, west of Dili, scales 0.1 mm.

Figure 12.Elasmopus tibarensis sp. nov., holotype male, 8.0 mm,AM P.90521; paratype female, 5.0 mm, AM P.90522, west of Dili, scales 0.1 mm.