Sunamphitoe angrox, Peart, Rachael A., 2017

Peart, Rachael A., 2017, Analysis of the genus Sunamphitoe Spence Bate, 1857 (Amphipoda: Ampithoidae) with descriptions of eight new species, Zootaxa 4269 (3), pp. 301-345 : 305-308

Sunamphitoe angrox sp. nov.

( Fig. 1–4 )

Type material. Holotype: male, 8.0 mm. AM P51277, 5 m, in Ecklonia radiata canopies, Cape Banks , New South Wales, Australia, 34°00’S 151°14’E, coll. N. Gallahar, 11 January 1994 .

Other material examined. Many specimens (males and females), 2.0–8.0 mm, AM P51278, Wollongong area, New South Wales, Australia, 34°26’S 150°53’E, coll. S. Mila, 1996.

Diagnosis (male). Antenna 2 robust, thicker and shorter than antenna 1. Mandible palp absent. Maxilla 1 inner plate with one slender seta. Maxilla 2 inner and outer plates equal width. Lower lip outer plate notched, lobes of equal height, inner lobe apically rounded. Gnathopod 2 carpus shorter than propodus; propodus broad; palm transverse, entire, no midmedial tooth, no defining posterodistal tooth, with defining robust seta; dactylus overreaching palm, inner margin denticulate. Pereopod 5 distal articles slightly broadened. Pereopods 6–7 distal articles slender. Uropod 3 peduncle with five distal robust setae; outer ramus with patch of lateral denticles, small lateral setal fringe; inner ramus with one distal robust seta. Telson distally truncate, apical cusps small, apical and lateral setae present and no lateral denticles.

Description. (Based on holotype male, 8.0 mm, AM P51277. Female, not described.)

Head as long as deep. Antenna 1 longer than antenna 2; peduncular article 1 longer than (1.6 ×) article 2; article 2 longer than (2.3 ×) article 3; article 3 shorter than (0.3 ×) article 1. Antenna 2 not densely setose on ventral margin; peduncular article 4 longer than article 5; flagellum 8–10 articulate. Mandible molar well developed, triturating, with eight robust setae in accessory setal row. Maxilla 1 palp well developed, with apical robust setae. Maxilliped outer plate reaching to midlength of palp article 3; article 4 with marginal setules only.

Pereon. Gnathopod 1 smaller than gnathopod 2, without densely setose margins, coxa smaller than gnathopod 2 coxa, with ventral setal fringe; not produced anteroventrally; anterior margin straight, distoventral corner rounded; basis subequal to coxa, with medial and lateral plumose setae, anteroventral lobe small and without setae; merus produced to form small subacute lobe, anterior margin with setae absent; carpus longer than merus, subtriangular, shorter than propodus (0.8 ×), posterior margin not lobate, rounded, with slender setae on posterior margin, anterior margin with distal slender setae only; propodus narrow (length 2.5 × width), subrectangular; palm transverse or nearly so, entire, without posterodistal tooth defining palm, with one defining robust seta; dactylus overreaching palm, inner margin denticulate. Gnathopod 2 without densely setose margins; coxa ventral margin with row of setules and tuft of slender setae on posterior corner; basis subequal in length to coxa with group of three slender meio-posterior setae, anteroventral lobe small and without setae; merus slightly produced to form small rounded lobe, anterior margin without setae; carpus subequal in length to merus, subtriangular, anterior margin with slender setae distally; propodus not produced into anterodistally setose lobe; dactylus tapering evenly, acute, inner margin denticulate. Pereopods 3–4 basis and merus expanded. Pereopods 5–7 weakly prehensile. Pereopods 5–6 propodus slightly expanded distally, with 3 distal robust setae; dactylus hooked. Pereopod 6 basis posterior margin rounded.

Pleon. Epimeron 3 posteroventral corner broadly rounded. Uropod 1, in situ, reaching midlength of rami of uropod 2; peduncle with eight marginal robust setae, and short lateral setal fringe (reaching half length of peduncle); inner ramus slightly longer and narrower than outer ramus, with one marginal robust seta and four apical setae; outer ramus with six marginal and four apical robust setae. Uropod 2 peduncle with five marginal robust setae and no lateral slender setal fringe; inner ramus slightly longer and narrower than outer ramus and without marginal robust setae, with four apical robust setae; outer ramus with six marginal and three apical robust setae. Uropod 3 peduncle longer than broad (1.4 ×), peduncle long with respect to rami (2.1 ×), marginal robust setae absent, marginal slender setae present in two bundles; rami broad; outer ramus longer than the inner one, with two large recurved robust setae.

Etymology. The specific epithet is an anagram of graxon alluding to the similarities of the new species to another Australian species, Sunamphitoe graxon Freewater & Lowry, 1994 .

Remarks. Sunamphitoe angrox sp. nov. is one of the species within the genus lacking a mandibular palp. Among these species, it is morphologically close to Sunamphitoe graxon , especially in the proportions and structure of gnathopod 1. The main difference between the two species is the structure of gnathopod 2. Sunamphitoe angrox has a gnathopod 2 with a transverse palm, which is similar in shape though broader and more robust than gnathopod 1. In Sunamphitoe graxon , the gnathopod 2 propodus is narrower, with an excavate palm. Sunamphitoe angrox sp. nov. is also close morphologically to S. aorangi but differs primarily by the absence of the mandibular palp (present in S. aorangi ). Sunamphitoe angrox is in a clade with S. sineplumosa ( Fig. 1 , clade 30), but differs in the shape of gnathopod 2 palm (sinuous in S. sineplumosa , straight in S. angrox ) and the presence of the short setal fringe of the uropod 1 peduncle (absent in S. sineplumosa ).

Habitat. Living in the canopy of the brown macroalga Ecklonia radiata at 5 m depth.

Distribution. Cape Banks and Wollongong, New South Wales, east coast of Australia.

Figures

FIGURE 1. One of fifteen most parsimonious trees (length 335 steps, consistency index 0.248, retention index 0.440). Clade numbers correspond to character state reconstructions listed in Appendix C. (p) indicates former placement in Peramphithoe. * indicates species described in this paper.

FIGURE 2. Sunamphitoe angrox sp. nov., holotype male, 8 mm, AM P 51277, Cape Banks, Botany Bay, New South Wales, Australia.

FIGURE 3. Sunamphitoe angrox sp. nov., holotype male, 8 mm, AM P 51277, Cape Banks, Botany Bay, New South Wales, Australia. Scales 0.2 mm.

FIGURE 4. Sunamphitoe angrox sp. nov., holotype male, 8 mm, AM P 51277, Cape Banks, Botany Bay, New South Wales, Australia. Scales 0.5 mm.