Cymadusa euclidius Hughes & Peart, 2013, sp. nov.
Creators: name: Hughes, Lauren E.
name: Peart, Rachael A.
Publisher: name: Zenodo
Year: 2013
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Amphipoda
Ampithoidae
Cymadusa
Cymadusa euclidius

description: Cymadusa euclidius sp. nov.
(Figs. 18, 19)
Type material. Holotype male, 17.0 mm, dissected, 4 slides, NMVJ64939, northeast end of Vancouver Peninsula, Western Australia (35°03’24”S 117°56’12”E), 6 m, 8 April 1984 (SWA 23).
Additional material examined. Western Australia: Male, dissected, 4 slides, AM P.82616, 2 km southeast of South Point, Two Peoples Bay (34°58’S 118°12’E), 12 m, mixed coralline and green algae, seagrass, 16 December 1983, coll. R.T. Springthorpe (WA 183); female, dissected, 2 slides, AM P.82617, 2 km southeast of South Point, Two Peoples Bay (34°58’S 118°12’E), 12 m, mixed coralline and green algae, seagrass, 16 December 1983, coll. R.T. Springthorpe (WA 183); male, 16 mm, dissected, 3 slides, AM P.82616, 24 km north of Dongara (29°3’30”S 114°47’47”–42’12”E), 15 m, mixed coralline and green algae, sea grass, dredge, 16 December 1983, coll. R.T. Springthorpe (WA 183); female, dissected, 2 slides, AM P.82617, 24 km north of Dongara (29°3’30”S 114°47’47”–42’12”E), 15 m, mixed coralline and green algae, sea grass, dredge, 16 December 1983, coll. R.T. Springthorpe (WA 183).
Type locality. Northeast end of Vancouver Peninsula, Western Australia (35°03’24”S 117°56’12”E).
Etymology. Named in reference to Euclidean geometry, inspired by the clearly defined right angled corner of the male gnathopod 2 propodus palm.
Diagnosis. Antenna 1 accessory flagellum 5-articulate. Antenna 2 peduncle article 4 subequal to article 5. Mandible accessory setal row with 9 robust setae. Maxilla 1 inner plate with 3 slender setae, outer plate palp slender, article 2 with 8 robust setae. Gnathopod 1 coxa distinctly larger than coxa 2, anterior margin convex, anteroventral corner produced, subacute; basis with single anterodistal lobe large, rounded; ischium anterior margin without lobes; propodus subrectangular, palm acute, convex, defined by 1 robust seta. Gnathopod 2 basis subequal in length to coxa, with single anterodistal lobe large, rounded, not reaching beyond ischium, without setae; ischium anterior margin without lobes; carpus subtriangular, 0.5 times propodus length, anterior margin with 4 robust setae; propodus subrectangular, palm nearly transverse, entire, with subquadrate distal tooth, palm corner subquadrate with 1 robust seta, palm length 0.3 times posterior margin; dactylus subequal in length to palm, apically acute, tapering evenly, inner margin crenate. Epimera 1–3 broadly rounded. Telson apically truncated, with 5 pairs of lateral setae and 4 pairs of apical setae.
Description of holotype. Head. Antenna 1 similar to antenna 2; article 1 subequal to article 2 length; article 2 length 2.5 times article 3; primary flagellum incomplete, with more than 33 articles; accessory flagellum 5- articulate. Antenna 2 article 4 subequal to article 5; flagellum with 30 articles. Mandible accessory setal row with 9 robust setae; palp 3-articulate; article 2 with 4 slender setae; article 3 length twice width. Lower lip outer plates with slit; lateral lobes distinctly longer than medial lobes, with apical ducts; mandibular lobes with curved margins, subacute apically. Maxilla 1 inner plate with 3 slender setae; outer plate palp slender, article 2 with 8 robust setae.
Pereon. Coxae 1–4 longer than broad. Gnathopod 1 coxa distinctly larger than coxa 2, as broad as deep, anterior margin convex, anteroventral corner produced, subacute; basis shorter than coxa, posterior margin with sparse slender setae, with single anterodistal lobe large, rounded with 2 slender setae; ischium anterior margin without lobes; merus anterodistal lobes subacute; carpus subrectangular, length 1.75 times width, 0.8 times propodus length, anterior margin with slender setae, posterior margin truncated; propodus subrectangular, length twice width, palm acute, convex, defined by 1 robust seta, palm length 0.5 times posterior margin; dactylus subequal in length to palm, apically acute, tapering evenly, inner margin crenate. Gnathopod 2 sexually dimorphic; basis subequal in length to coxa, with single anterodistal lobe large, rounded, not reaching beyond ischium, without setae; ischium anterior margin without lobes; merus margin anterodistal corner subacute; carpus subtriangular, length 1.1 times width, 0.5 times propodus length, anterior margin with 4 robust setae; propodus subrectangular, length 1.8 times width, palm nearly transverse, entire, with subquadrate distal tooth, palm corner subquadrate with 1 robust seta, palm length 0.3 times posterior margin; dactylus subequal in length to palm, apically acute, tapering evenly, inner margin crenate.
Pleon. Epimera 1–3 broadly rounded. Uropod 1 long, reaching past uropod 2 rami; peduncle length 3 times width, with 9 robust setae, setal fringe 4/5 length of peduncle, with large, acute distoventral spine; inner ramus 0.9 times peduncle length, longer than outer ramus, with 6 marginal robust setae; outer ramus with 5 marginal robust setae. Uropod 2 peduncle with small subacute distoventral spine, with 4 robust setae; inner ramus with 3 marginal robust setae, subequal to outer ramus length; outer ramus with 3 marginal robust setae. Uropod 3 peduncle length 1.2 times width, with 7 distal peduncular robust seta and 4 distal slender setae; inner ramus 1.3 times width, subequal to outer ramus, with 8 distal robust seta and 7 distal slender setae; outer ramus with patch of small lateral denticles and 1 lateral robust seta, and 2 large recurved robust setae. Telson subtrapezoidal, apically truncated, with small apical cusps, 5 pairs of lateral setae, 2 pairs of lateral plumose setae and 4 pairs of apical setae.
Remarks. Cymadusa euclidius sp. nov. aligns with C. brevidactyla, C. cavimana, C. hadros sp. nov., C. smilodonta and C. priscileo sp. nov., based on the short dactylus of gnathopod 2. In C. euclidius sp. nov. and C. hadros sp. nov. the gnathopod 2 propodus palm is transverse and the dactylus is subequal to the palm length, which separates these two speciesfrom C. brevidactyla, C. cavimana, C. smilodonta and C. priscileo sp. nov.
It is possible that C. euclidius sp. nov., at 17 mm, represents a smaller male growth stage of C. hadros sp. nov., which reaches ~ 20 mm. However, article 2 of the maxilla 1 palp has eight robust setae, whereas C. Hadros sp. nov. has no robust setae. Uropod 2 of C. euclidius sp. nov. has a peduncle with a small distoventral spine and broader rami, which are shorter than the peduncle, whereas in C. hadros sp. nov., the peduncle is without a spine and the rami are more slender and subequal to the peduncle length.
Distribution. Australia. Western Australia: Vancouver Peninsula, Two Peoples Bay, Dongara (current study).
description: Published as part of Hughes, Lauren E. & Peart, Rachael A., 2013, New species and new records of Ampithoidae (Peracarida: Amphipoda) from Australian Waters, pp. 1-102 in Zootaxa 3719 (1) on pages 36-39, DOI: 10.11646/zootaxa.3719.1.1, http://zenodo.org/record/246657