Quadrisegmentum atauro, Hughes & Takeuchi, 2016

Hughes, Lauren Elizabeth & Takeuchi, Ichiro, 2016, Two New Species of Quadrisegmentum (Phtisicidae: Amphipoda: Crustacea) from the Central Indo-Pacific, with Notes on the Type Species Q. triangulum Hirayama, 1988, Records of the Australian Museum 68 (5), pp. 231-244 : 232-236

Quadrisegmentum atauro sp. nov.

Figs 1–4

Type material. Holotype ♂, 10.5 mm (illustrated), dissected in part, 1 slide, AM P.98327, Timor-Leste, east of Atauro Island , Outer Reef, dense coral reef slope (8°13'48"S 125°36'57"E), 17 m, green calcareous alga Halimeda sp., 20 September 2012, coll. L.E. Hughes ( TM 2012-087 ); paratype ♀, 9 mm (illustrated), AM P.98328, Timor-Leste, east of Atauro Island, Outer Reef, dense coral reef slope (8°13'48"S 125°36'57"E), 17 m, green calcareous alga Halimeda sp., 20 September 2012, coll. L.E. Hughes ( TM 2012-087 ) . Paratypes: 1 ♂, 5.1 mm [a smaller specimen has been chosen for SEM as it is in better condition], whole animal SEM pin mount, AM P.91095, Timor-Leste, east of Atauro Island, Outer Reef , dense coral reef slope (8°13'48"S 125°36'57"E), 17 m, green calcareous alga Halimeda sp., 20 September 2012,coll. L.E. Hughes ( TM 2012-087 ) ; 1 ♂, 10.5 mm, SEM pin mount, AM P.91091, Timor-Leste, east of Atauro Island, Outer Reef , dense coral reef slope (8°13'48"S 125°36'57"E), 17 m, green calcareous alga Halimeda sp., 20 September 2012, coll. L.E. Hughes ( TM 2012-087 ) ; 3 ♂♂, AM P.91097, Timor-Leste, east of Atauro Island, Outer Reef , dense coral reef slope (8°13'48"S 125°36'57"E), 17 m, green calcareous alga Halimeda sp., 20 September 2012, coll. L.E. Hughes ( TM 2012-087 ) ; 1 ♂, AM P.91092, Timor-Leste, east of Atauro Island, Outer Reef , dense coral reef slope (8°13'48"S 125°36'57"E), 17 m, green calcareous alga Halimeda sp., 20 September 2012, coll. L.E. Hughes ( TM 2012-087 ); 1 mature ♀, AM P.91096, Timor-Leste, east of Atauro Island, Outer Reef , dense coral reef slope (8°13'48"S 125°36'57"E), 17 m, green calcareous alga Halimeda sp., 20 September 2012, coll. L.E. Hughes ( TM 2012-087 ); many specimens, AM P.91094, Timor-Leste, east of Atauro Island, Outer Reef , dense coral reef slope (8°13'48"S 125°36'57"E), 17 m, green calcareous alga Halimeda sp., 20 September 2012, coll. L.E. Hughes ( TM 2012-087 ); 4 mature ♀♀, AM P.91093, Timor-Leste, east of Atauro Island, Outer Reef , dense coral reef slope (8°13'48"S 125°36'57"E), 17 m, green calcareous alga Halimeda sp., 20 September 2012, coll. L.E. Hughes ( TM 2012-087 ) ; 7 specimens (6 ♂♂ and 1 mature ♀), AM P.91090, Timor-Leste, east of Atauro Island, Inner Reef , reef slope (8°14'30"S 125°36'49"E), 14 m, mixed turfing algae, 20 September 2012, coll. L.E. Hughes ( TM 2012-034 ); 1 mature ♀, AM P.91099, Timor-Leste, west of Dili, off Tibar , on outer side of reef, rubble and sandy reef slope (8°33'48"S 125°28'31"E), 10–12 m, coral rubble and mixed algae, 21 September 2012, coll. A. Murray ( TM 2012-037 ) ; 9 specimens (5 ♂♂ and 4 mature ♀♀), AM P.91098, Timor-Leste, east of Metinaro, Secret Garden Reef (8°29'15"S 125°49'53"E), 20 m, tufts of red algae, 22 September 2012, coll. L.E. Hughes ( TM 2012-060 ) .

Type locality. Timor-Leste, east of Atauro Island , Outer Reef (8°13'48"S 125°36'57"E) .

Etymology. Named from the type locality, applied as a noun in apposition.

Description. (Based on male, body length, 10.5 mm, AM P. 98327, and male, body length, 10.5 mm, AM P.91901 for pereopod 5 and abdomen).

Body Somites slender. Head and pereonite 1 combined, completely fused, suture absent. Pereonite 2 with small acute anterolateral projection. Pereonites 3–6 without anterior or mid-lateral projections.

Antenna 1 ⅓× body length; peduncle article 2 longest, 1.9× article 1; article 3 length 0.8× article 2; flagellum length 0.24× peduncle with 4–6 articles (left and right, respectively). Antenna 2 0.9× Antenna 1; flagellum, 0.25× peduncle length, body with 8–9 articles (left and right, respectively).

Mandible right similar to left, incisor with 4 teeth, lacinia mobilis with 7 teeth followed by 2 plates; palp 3-articulate; article 2 longest, with 1 distal slender setae; article 3 with 1 distal and 1 midlateral slender setae, anterodistal margin pubescent. Mandible left, palp similar to right palp. Lower lip setose on outer lobe. Maxilla 1 outer plate with 5–6 robust setae; palp 2-articulate, article 2 with 2 triangular projections, each with a robust seta, with 3–4 subapical slender setae. Maxilla 2 inner plate short with 4 robust setae; outer plate long, with 4 apical and 1 subapical robust setae. Maxilliped basal endite (inner plate) larger than ischial endite (outer plate), rectangular, with 4 apically robust setae near distal margin; ischial endite (outer plate) several slender setae on inner margin; palp 4-articulate; article 2 laterally expanded, with 3–4 slender setae; article 3 with rounded distal projection with 2 setae.

Pereon. Gnathopod 1 basis similar in length to ischium, merus and carpus combined; carpus and merus subequal in length with anterior and posterior slender setae; propodus triangular; palm defined by prominent, curved, bifid process with 2 apical robust setae; dactylus falcate, inner margin lined with setules. Gill 2 elongate, length 5× width, 0.6× pereonite 2 length. Gnathopod 2 begins ⅓ along posterior margin of pereonite 2; basis length 1.9× pereonite 2 length, 1.6× ischium, merus and carpus combined; merus subrectangular, distally swollen (length 2.8× width), subequal to carpus; carpus subrectangular (length 3.1× width); propodus subovate, longer than wide (length 2.8× width); palm 60% of posterior margin, 3 proximal projections each with robust seta.

Gill 3 slender, 7× width, length 0.9× pereonite 3 length. Pereopod 3 length 0.3× body length; basis longest, 0.4× pereopod 3 length; ischium 0.1× basis length; merus 0.6× basis length; carpus 0.27× basis length; propodus 0.9× carpus length with 3 large and 1 small robust setae along palm; dactylus recurved. Gill 4 subequal to gill 3. Pereopod 4 shorter than pereopod 3, length 0.35× body length; basis longest, 0.4× pereopod length; ischium 0.06× basis length; merus 0.65× basis length; carpus 0.3× basis length; propodus shorter than carpus, length 0.9× carpus with 3 large and 1 small robust setae along palm; dactylus recurved.

Pereopod 5 with 4 articles; article 1 length 0.9× article 2; article 2 longest, 1.1× article 3; dactylus recurved. Pereopod 6 slender, 0.5× body length; basis longest, 0.37× pereopod 6 length; ischium 0.08× basis length; merus 0.7× basis length; carpus 0.33× basis length, anterior margin with 2 robust setae; propodus 0.6× basis length, anterior margin with 3 groups of long robust setae (middle group only with paired robust setae) and distal small robust setae; dactylus recurved. Pereopod 7 slender, smaller than pereopod 6, 0.4× body length; basis 0.27× pereopod 7 length; ischium 0.25× basis length; merus length subequal to basis; carpus 0.65× basis length, anterior margin with 2 robust setae; propodus 0.8× basis length, anterior margin with 3 groups of long robust setae (middle group only with paired robust setae) and distal small robust setae; dactylus recurved.

Pleon. Uropod 1 elongate (length 6× width), with minute a line of lateral setae; ramus damaged. Uropod 2 peduncle elongate (length 2.5× width), with a line of lateral setae; ramus 0.6× peduncle length. Telson small, with a pair of setae.

Female. (based on female paratype, body length 9 mm, AM P. 98328). Pereonite 4 without rounded anterolateral projection. Antenna 1 article 2 subequal to article 3 length, 1.8× article 1 length; flagellum with 10 articles. Antenna 2 near 2/3 length of antenna 1; flagellum 0.6× peduncle length with 7 articles.

Remarks. Quadrisegmentum atauro sp. nov. and Q. yirrgay sp. nov. have long rectilinear gills which separates them from Q. triangulum where the gills are much shorter and subovate. The pereonite 2 in Q. atauro sp. nov. has on one pair of acute anterior lateral projections which are not seen for Q. yirrgay sp. nov. and Q. lowryi Guerra-García, 2006 .

Distribution. Timor-Leste: Atauro Island, Tibar (current study).

Figures

Figure 1. Quadrisegmentum atauro sp. nov., holotype male habitus, 10.5 mm, AM P.98327 and paratype female,9 mm,AM P.98328;Atauro Island,Timor-Leste.

Figure 2. Quadrisegmentum atauro sp. nov. holotype male, 10.5 mm, AM P.98327, Atauro Island, Timor- Leste, scales 0.1 mm.

Figure 3.Quadrisegmentum atauro sp. nov.holotype male, 10.5 mm, AM P.98327, Atauro Island, Timor-Leste, scales 0.1 mm.

Figure 4. Quadrisegmentum atauro sp. nov. SEM image of paratype male, 5.1 mm, head and pereopod 4, AM P.91095; paratype male, 10.5 mm, gnathopod 2, pereopod 5 and urosome paratype male AM P.91091; Atauro Island, Timor-Leste. Scales: H and P4–5 scale 100 µm, Ur dorsal view scale 10 mm and Ur transverse view 20 µm.