Cymadusa drummondae, 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 : 33-34

Cymadusa drummondae sp. nov.

( Figs. 16 , 17 )

Type material. Holotype male, 11.0 mm, dissected, 4 slides, NMVJ64944, Cape Otway, Victoria (38°52’S 143°31’E), 28 January 1967, coll. W. Seed; paratype male, 9.4 mm, dissected, 1 slide, NMVJ64946, Cape Otway, Victoria (38°52’S 143°31’E), 28 January 1967, coll. W. Seed; paratype female, 8.3 mm, dissected, 1 slide, NMVJ64945; paratypes 7 specimens, NMV J18115 , Cape Otway, Victoria (38°52’S 143°31’E), 28 January 1967, coll. W. Seed.

Additional material examined. Victoria: 1 specimen, AM P.88411, Walkerville South (38°51’S 145° 59’E), 0.5 m, brown algae Padina sp. and Dictyopteris sp., 7 December 2010, Coll. A.G.B. Poore.

Type locality. Cape Otway, Victoria, Australia (38°52’S 143°31’E).

Etymology. Named in honour of Margaret M. Drummond for her contributions to the taxonomy of the Australian amphipod fauna.

Diagnosis. Antenna 1 similar to antenna 2; accessory flagellum 1-articulate. Antenna 2 article 4 length 1.2 times article 5; flagellum incomplete with more than 28 articles. Mandible accessory setal row with 7 robust setae. Maxilla 1 inner plate with 5 slender setae; outer plate palp slender, with 6 robust setae. Gnathopod 1 coxa distinctly larger than coxa 2, anterior margin convex, anteroventral corner produced rounded; posterior margin with fringe of long, slender setae, with single anterodistal lobe large, rounded; ischium anterior margin with small lobe; propodus subrectangular, palm subacute, convex defined by rounded corner with 1 robust seta. Gnathopod 2 basis shorter than coxa, with single anterodistal lobe large, rounded, not reaching beyond ischium, anterodistal corner with 4 slender setae; ischium anterior margin with lobe; carpus subtriangular, anterior margin with slender setae; propodus subovate, broad, palm subacute, entire, defined by produced subquadrate corner with 1 robust seta; dactylus subequal in length to palm, apically acute, tapering evenly, inner margin crenate. Epimera 1–3 subquadrate, posterior margin straight, posterodistal corner subquadrate. Telson apically rounded with 5 pairs of lateral setae and 1 pair of apical setae.

Description of holotype. Head. Antenna 1 similar to antenna 2; article 1 length 1.1 times article 2 length; article 2 length 2.8 times article 3; primary flagellum incomplete, with more than 32 articles; accessory flagellum 1-articulate. Antenna 2 article 4 length 1.2 times article 5; flagellum incomplete with more than 28 articles. Mandible accessory setal row with 7 robust setae; palp 3-articulate; article 2 with 1 slender seta; article 3 length 2.1 times width. Lower lip outer plates with slit; lateral lobes distinctly longer than medial lobes, with apical ducts; mandibular lobes with curved margins, rounded apically. Maxilla 1 inner plate with 5 slender setae; outer plate palp slender, with 6 robust setae.

Pereon. Coxae 1–4 longer than broad. Gnathopod 1 smaller than gnathopod 2; coxa 1 distinctly larger than coxa 2, anterior margin convex, anteroventral corner produced rounded; basis shorter than coxa, posterior margin with fringe of long, slender setae, with single anterodistal lobe large, rounded with 2 robust setae; ischium anterior margin with small lobe; merus posterodistal corners subacutely produced; carpus subtriangular, length subequal to width, 0.8 times propodus length, posterior margin produced to form a subacute lobe; propodus subrectangular, length 1.9 times width, palm subacute, convex defined by rounded corner with 1 robust seta, palm length 0.4 times posterior margin; dactylus subequal in length to palm, apically acute, tapering evenly, inner margin crenate. Gnathopod 2 sexually dimorphic; basis shorter than coxa, with single anterodistal lobe large, rounded, not reaching beyond ischium, anterodistal corner with 4 slender setae; ischium anterior margin with lobe; merus posterodistal margins subacute; carpus subtriangular, length 1.2 times width, 0.8 times propodus length, anterior margin with slender setae; propodus subovate, broad, length 0.9 times width, palm subacute, entire, defined by produced subquadrate corner with 1 robust seta, palm length 0.5 times posterior margin; dactylus subequal in length to palm, apically acute, tapering evenly, inner margin crenate.

Pleon. Epimera 1–3 subquadrate, posterior margin straight, posterodistal corner subquadrate. Uropod 1 long, reaching past uropod 2 rami; peduncle length 3.1 times width, with 7 robust setae, setal fringe ¾ length of peduncle, with large, acute distoventral spine; inner ramus slightly longer than outer ramus, with 2 marginal robust setae; outer ramus slender, length 5 times width, with 4 marginal robust setae. Uropod 2 peduncle with 4 robust setae, without distoventral spine; inner ramus longer than outer ramus, with 1 marginal robust setae; outer ramus with 3 marginal robust setae. Uropod 3 peduncle longer than broad, 1.5 times width, twice rami length, with 1 marginal robust setae, with 8 distal peduncular robust setae, with 2 distal slender setae; inner ramus length 1.2 times width, with 6 distal robust setae, 5 distal slender setae and 1 lateral robust setae; outer ramus subequal in length to inner ramus, with patch of small lateral denticles. Telson subtrapezoidal, apically rounded, with small apical cusps, 5 pairs of lateral setae, 2 pairs of lateral plumose setae and 1 pair of apical setae.

Remarks. Cymadusa drummondae sp. nov. is distinguished from all other Cymadusa species by the combination of the gnathopod 2 basis and ischium with broad, anterodistal lobes and the broad propodus, where the length is subequal to breadth. Three Cymadusa species, C. drummondae sp. nov., Cymadusa elegantis and Cymadusa chuwae have the gnathopod 2 male propodus broad with an entire palm. In C. drummondae sp. nov. and C. chuwae , the male gnathopod 1 coxa anterior corner is broad and the propodus is subovid, while in C. elegantis the coxa 1 anterior corner is subacute the propodus rectolinear. The male gnathopod 2 propodus palm is subacute in Cymadusa drummondae sp. nov., which separates it from C. chuwae in which the palm angle is near transverse. The telson of Cymadusa drummondae sp. nov. is apically subacute with a single pair of apical setae similar to C. elegantis , whereas the telson of C. chuwae is apically truncate with several pairs of apical robust setae.

Cymadusa drummondae sp. nov. is also similar to C. grossimana in the form of gnathopod 1 and 2. Cymadusa grossimana has the gnathopod 1 coxa anterior margin less broadly rounded and the carpus is more elongate than C. drummondae sp. nov. The gnathopod 2 basis anterodistal lobe broadly rounded and concave propodus palm in C. drummondae sp. nov. further separates it from C. grossimana which has a subacute basis anterodistal corner and straight palm.

Cymadusa drummondae sp. nov. is very similar to another Australian species, Ampithoe mantissa sp. nov. in the form of the male gnathopod 2 basis, carpus and propodus, as well as the telson setation. The presence of the large distoventral spine on uropod 1 and accessory flagellum of antenna 1 of C. drummondae sp. nov. readily separates these species as well as placing them in separate genera.

Distribution. Australia. Victoria: Cape Otway (current study); Walkerville South (current study).

Figures

FIGURE 16. Cymadusa drummondae sp. nov., holotype male, 11.0 mm, NMVJ 64944, Cape Otway, Victoria.

FIGURE 17. Cymadusa drummondae sp. nov., holotype male, 11.0 mm, NMVJ 64944, Cape Otway, Victoria, scales 0.1 mm.