Ampithoe mantissa, 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 : 11-14

Ampithoe mantissa sp. nov.

( Figs. 4 , 5 )

Type material. Holotype male, 10.4 mm, dissected, 4 slides, SAMA C7642, 5 km north northwest of 5th creek mouth, near Port Pirie, South Australia, 4–6 m, seagrasses Poisidonia sp. and Amphibolus sp., August 1979, coll. T. Ward.

Type locality. 5 km north northwest of 5th creek mouth, near Port Pirie, South Australia.

Etymology. Mantissa —Latin for a trifling addition, in reference to the authors’ anguish in establishing a new species for an individual that has a close resemblance to a species in another genus.

Diagnosis. Antenna 1 accessory flagellum minute, scale-like. Maxilla 1 outer plate palp article 2 with 7 robust setae. Gnathopod 1 coxa 1 subequal to coxa 2, anterior margin convex, anteroventral corner produced rounded; basis shorter than coxa, anterodistal corner with reduced lobe and 2 slender setae; carpus rectolinear, anterior margin lined with a few slender setae, posterodistal margin lined with slender setae, posterodistal corner subquadrate; propodus subrectangular, palm acute, convex, defined by single robust seta, without corner or tooth. Gnathopod 2 basis posterior margin lined with slender setae, anterodistal lobe large, rounded, reaching beyond ischium, lobed lined with slender setae; ischium without anterior lobe; carpus subtriangular, length subequal to width; propodus subovoid, length subequal to width, palm subchelate, straight, defined by subquadrate corner with subacute tooth and single robust seta, dactylus subequal in length to palm, tapering evenly, inner margin crenulate. Telson apically convex with row of lateral slender setae and 1 pair of apical slender setae.

Description of holotype. Head. Antenna 1 similar to antenna 2; article 1 subequal to article 2 length; article 3 length 0.25 times article 1; primary flagellum incomplete, with more than 33 articles; accessory flagellum minute, scale-like. Antenna 2 peduncle article 4 length 1.1 times article 5; flagellum with 27 articles. Mandible accessory setal row with 6 robust setae; palp 3-articulate; article 2 with 6 slender setae; article 3 length 2.2 times width. Lower lip outer plates with slit; lateral lobe distinctly longer than medial lobe, with single pair of apical ducts; mandibular lobes with curved margins, apically rounded. Maxilla 1 inner plate with 2 slender setae; outer plate, palp broad, article 2 with 7 robust setae.

Pereon. Coxae 1–4 longer than broad. Gnathopod 1 smaller than gnathopod 2; coxa 1 subequal to coxa 2, anterior margin convex, anteroventral corner produced rounded; basis shorter than coxa, posterior margin with slender setae, anterodistal corner subquadrate, with 2 slender setae; ischium anterior margin without lobe; merus posterodistal corner subquadrate; carpus rectolinear, length 1.5 times width, 0.8 times propodus length, anterior margin lined with a few slender setae, posterodistal margin lined with slender setae, posterodistal corner subquadrate; propodus subrectangular, narrow, length twice times width, palm acute, convex, defined by single robust seta, without corner or tooth, palm length 0.4 times posterior margin; dactylus subequal in length to palm, inner margin crenate. Gnathopod 2 sexually dimorphic; basis length 0.9 times coxa, posterior margin lined with slender setae, anterodistal lobe large, rounded, reaching beyond ischium, lobed lined with slender setae; ischium without anterior lobe; merus anterodistal corner subacute; carpus subtriangular, length subequal to width, 0.8 times propodus length, anterior margin with clusters of slender setae; propodus subovoid, length subequal to width, palm subchelate, straight, defined by subquadrate corner with subacute tooth and single robust seta, palm length 0.45 times posterior margin; dactylus subequal in length to palm, tapering evenly, inner margin crenulate.

Pleon. Epimera 1–3 subquadrate, posterior margin weakly convex, posterodistal corner rounded. Uropod 1 long, reaching end of uropod 2 rami; peduncle length 3 times width, with 12 robust setae, setal fringe along 3/4 of margin, distoventral spine absent; inner ramus 0.7 times peduncle length, with 5 marginal robust setae, length 1.1 times outer ramus; outer ramus with 6 marginal robust setae. Uropod 2 peduncle with 3 robust setae, without distoventral spine; inner ramus without marginal robust setae, subequal in length to outer ramus; outer ramus with 4 marginal robust setae. Uropod 3 peduncle much longer than broad, length 1.8 times width, twice the length of the rami, with 6 distal robust setae, 8 distal slender setae; inner ramus length 1.5 times breadth, subequal to outer ramus, with 4 distal robust setae, 5 distal slender setae and 2 lateral robust setae; outer ramus with 2 large recurved distal robust setae and lateral denticles. Telson subtrapezoidal, apically convex, with small apical cusps, row of lateral slender, 2 pair of lateral plumose and 1 pair of apical slender setae.

Remarks. Ampithoe mantissa sp. nov. is similar to A. ulladulla Peart, 2007 b, in the form of gnathopod 2 propodus size and palm shape. These species can be distinguished by the shape of the gnathopod 1 propodus palm, which is convex in A. mantissa sp. nov. and sinusoidal in A. ulladulla . The morphology of the gnathopod 1 and 2 of A. mantissa sp. nov. is strikingly similar to that of Cymadusa drummondae sp. nov. However, the uropod 1 peduncle with ventromedial spine and the presence of an accessory flagellum on antennae 1 readily separates C. drummondae sp. nov. from A. mantissa sp. nov. and supports its different generic placement.

Distribution. Australia. South Australia: Port Pirie (current study).

Figures

FIGURE 4. Ampithoe mantissa sp. nov., holotype male, 10.4 mm, SAM C 7642, Port Pirie, South Australia.

FIGURE 5. Ampithoe mantissa sp. nov., holotype male, 10.4 mm, SAM C 7642, Port Pirie, South Australia, scales 0.1 mm.