Cymadusa euclidius, Hughes, Lauren E. & Peart, Rachael A., 2013

Hughes, Lauren E. & Peart, Rachael A., 2013, New species and new records of Ampithoidae (Peracarida: Amphipoda) from Australian Waters, Zootaxa 3719 (1), pp. 1-102 : 36-39

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).

Figures

FIGURE 18. Cymadusa euclidius sp. nov., holotype male, 17.0 mm, NMV J 64939, Vancouver Peninsula, Western Australia.

FIGURE 19. Cymadusa euclidius sp. nov., holotype male, 17.0 mm, NMVJ 64939, Vancouver Peninsula, Western Australia, scales 0.1 mm.