Bathypoma enigma, Lowry & Berents, 1996

Lowry, J. K. & Berents, Penelope B., 1996, The Ericthonius group, a new perpective on an old problem (Crustacea: Amphipoda: Corophioidea), Records of the Australian Museum 48 (1), pp. 75-109 : 87-91

Bathypoma enigma n.sp.

Figs 4 -8

Type data. HOLOTYPE, male, 2.07 mm, NMV J20777 ; PARATYPE, female, 2.60 mm, NMV J20778 ; PARATYPE male, NMV J20779 ; 31 PARATYPES, NMV J14644 ; PARATYPE male, 2 mm, AM P40434 ; 20 PARATYPES, AM P40435; east of Freycinet Peninsula , Tasmania, Australia, 42°2.20'S 148°38.7'E, coarse shelly sand, 800 rn, epibenthic sled, M.F. Goman and party on. RV Franklin, 27 July 1986, SLOPE 45 ; PARATYPE, NMV J14645 , east of Freycinet Peninsula , Tasmania, Australia, 42°0.20'S 148°37.7'E, coarse shelly sand, 720 rn, epibenthic sled, M.F. Goman and party on RV Franklin, 27 July 1986, SLOPE 46 ; PARATYPE, NMV J14459 , south of Point Hicks , Victoria, Australia, 38°19.60'S 149°24.30'E, rock, rubble, clay, sand, biogenic sediment, 930-951 rn, epibenthic sled, M.F. Goman and party on RV Franklin, 23 July 1986, SLOPE 33 .

Material described. Holotype male, 2.07 mm; dimorphic characters based on paratype female, 3.60 mm.

Description. Head: rostrum short, curved down, apically acute, length 0.3 x head; lateral cephalic lobe well developed, ventral corner acute, subocular margin deeply recessed, anteroventral corner acute, ventral margin horizontal, posterior margin vertical. Antenna 1: long, 0.5 x body length, without scales; peduncular article 1 produced dorsodistally and dorsomedially, dorsodistal projection 0.4 along article 2, length 0.7 x peduncular article 3; accessory flagellum absent; flagellum long, 3­ articulate (female 2), aesthetascs present along ventral margin, article 1 long, 2.8 x article 2. Antenna 2: subequal in length to antenna 1; peduncle without scales; flagellum 4-articulate (female 4), article 1 long, 2.6 x article 2.

Epistome and upper lip: fused, produced, acute. Mandible: left incisor with 5 cusps, right incisor with 5 cusps; left lacinia mobilis with 4 cusps, right with one large cusp and minutely serrate margin; left accessory setal row with 3 pappose robust setae, with 3 intermediate plumose setae, right accessory setal row with 2 pappose robust setae, with 2 intermediate plumose setae; molar triturating, molar flake on left and right side, molar seta absent; palp article 2 short, broad, length 2.1 x breadth, 1 x article 3, with 1 proximal and 1 distal A2-setae, 5 submarginal A2- and 4 submarginal B2-setae; article 3 clavate, long, 2.5 x· breadth, with 2 proximal A3-setae, 4 submarginal A3- and 4 submarginal B3-setae and 7 E3-setae terminally. Maxilla 1: inner plate small, with 1 simple apical seta; outer plate with 9 setal-teeth; right palp with 3 and left with 3 terminal robust setae, flag seta present on distolateral corner, right palp with 1 and left with 1 subterminal setae. Maxilla 2: outer plate slightly broader than inner; inner plate with setae distallyalong medial margin. Maxilliped: inner plate subrectangular with 3 nodular robust setae, without subterminal robust setae on medial corner, oblique setal row with 6 plumose setae; outer plate with 2 apical plumose setae, and 4 apicomedial robust setae; palp article 2, length 2.9 x breadth, article 3, length 2 x breadth.

Peraeonite 5: male, length 1.4 x breadth, female, length 1.2 x breadth. Gnathopod 1: subchelate; coxa not fused to peraeonite 1 in male or female, length 1.3 x depth, without anteroventral lobe; basis in male with sparse setae along anterior margin, in female with sparse setae along anterior margin, without robust setae along anterior margin; carpus length 1.1 x depth with setose posterior lobe, anterior margin without setae in male and female; propodus length 1.6 x depth, with 5 rows of anteromedial setae; palm extremely acute, sparsely setose, with barbed robust setae. Gnathopod 2: subchelate in male and female; coxa not fused to peraeonite 2 in male or female, length 1.7 x depth, without anteroventral lobe; basis short, broad, length 1.4 x breadth; carpus small, short, compressed, length 0.8 x breadth, posterior margin without tooth; propodus length 1.7 x depth; with broad tooth bearing 3 barbed robust setae defining proximal end of palm; dactylus 0.8 x as long as propodus.

Peraeopod 3: coxa not fused to peraeonite 3 in male or female, length 2 x depth, without anteroventral lobe; basis length 1.6 x breadth, with inflated anterodorsal corner, with plumose setal group, without denticles along anterior margin; ischium length 1.6 x breadth; merus without ridges; carpus with 2 simple setae along distal half of anterior margin, with 3· plumose setae along distal half of posterior margin; propodus with 3 plumose setae along posterior margin. Peraeopod 4: coxa not fused to peraeonite 4 in male or female, length 2.2 x depth, without anteroventral lobe; basis length 1.5 x breadth, without setal group along anterior margin; ischium long, length 1.8 x breadth; carpus with 2 plumose setae along distal half of anterior margin, with 2 plumose setae along distal half of posterior margin; propodus with 3 plumose setae along posterior margin. Peraeopod 5: coxa, length 2.3 x depth, without patches of small setae; anterior lobe of merus not extending beyond anterior margin of carpus, posterior lobe with 3 plumose setae; propodus with 2 setae along posterior margin, dactylus short, uncinate with two accessory spines. Peraeopod 6: coxa with patch of small setae; basis with short, sparse setae anteriorly, with small denticles along posterior margin; merus, length 1.6 x breadth, without small anterodistal lobe; carpus without anterodistal lobe, with posterodistal lobe, posterodistal corner bearing small setal bunch; propodus, anterodistal corner bearing large setal bunch; dactylus short, uncinate with two accessory spines. Peraeopod 7: coxa without posterodorsal lobe, without patch of small setae; basis without denticles along anteroproximal margin, with small denticles along posterior margin; merus, length 2 x breadth, without small anterodistallobe, posterodistal corner bearing small setal bunch; carpus without anterodistallobe, with well-developed posterodistallobe, anterodistal corner bearing small setal bunch; propodus posterodistal corner bearing small setal bunch, anterodistal corner bearing large setal bunch; dactylus short, uncinate with two accessory spines.

Oostegites: from gnathopod 2 to peraeopod 5. Gills: from peraeopod 3 to peraeopod 6.

Pleopods 1 to 3: decreasing in size. Pleopod 1: peduncle with patch of small setae, with 2 small distomedial hooks; rami subequal in length; inner ramus without patch of small setae, 7-articulate; outer ramus, article 1 evenly swollen, 7-articulate. Pleopod 2: peduncle without patch of small setae, with 1 small distomedial hook; biramous, inner ramus without patch of small setae, reduced, I-articulate, length 0.4 x outer ramus; outer ramus broad, 4-articulate, without patch of small setae. Pleopod 3: peduncle without patch of small setae, without distomedial hooks; inner ramus absent. Uropod 1: biramous, peduncle with distoventral corona of cuticular teeth, length 1 x outer ramus, without distoventral spine; outer ramus with lateral row of denticles, with 4 lateral setae, with large apical robust seta; inner ramus length 0.8 x outer ramus, without setae, with apical robust seta. Uropod 2: uniramous, peduncle length 2.1 x breadth, 1.7 x ramus; ramus small, with denticles and 1 apical robust seta. Uropod 3: uniramous, peduncle length 1.7 x breadth; ramus with 2 curved spines. Telson: length 0.7 x breadth, cleft 0.90 x length, each lobe with 9 to 8 anteriorly directed spines in two rows.

Parasites. Some specimens of Bathypoma enigma had a parasitic copepod attached to the head between antennae 1. These specimens were examined by Grygier (pers. comm.) and identified as males and females of an undescribed species of a nicothoid copepod Sphaeronella sp. The specimens are held at the Museum of Victoria, registration NMV J15063 .

Thbe. Composed of annulated fine grains occasionally with detritus and foraminiferans.

Etymology. The name enigma refers to the subchelate second gnathopod of the species.

Remarks. At present this is the sole species in the genus.

Distribution. Off south-eastern Australia in 720 to 951 m depth.

Figures

Fig. 4. Bathypoma enigma n.sp., lateral view, male holotype, 2.1 mm, NMV J20777; dorsal view, female paratype, 2.6 mm, NMV J20778; east of Freycinet Peninsula, Tasmania.