Leucothoella gracilis Haswell 1879
Creators: name: White, Kristine N.
name: Thomas, James Darwin
Publisher: name: Zenodo
Year: 2009
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Amphipoda
Leucothoidae
Leucothoella
Leucothoella gracilis

description: Leucothoella gracilis Haswell, 1879   
(Figs 31, 32)  
 Leucothoella gracilis Haswell, 1879: 263–264, pl. 10, fig. 2. — Haswell, 1882: 249. — Stebbing, 1906: 168. —J.L. Barnard, 1974: 99–102, figs 60–61. — Stebbing, 1910: 636. — Moore, 1987: 258. — Lowry & Stoddart, 2003: 156 (catalogue).   
 Material examined. 2 males, AM P79288 (JDT / LIZ 14); 8 males, 3 females, AM P79289 (JDT / LIZ 15); 6 males, 1 female, AM P79290 (JDT / LIZ 20); 1 male, AM P70886 (QLD 1693); 1 female, AM P70993 (QLD 1708); 1 male, 1 female, 1 juvenile, AM P71096 (QLD 1716); 1 male, 1 female, AM P71206 (QLD 1743); 2 males, AM P71226 (QLD 1775); 2 juveniles, AM P79287 (QLD 1775); 5 males, 1 female, AM P71375 (QLD 1875); 1 male, AM P71420 (QLD 1815); 1 juvenile, AM P71597 (QLD 1838); 1 female, GCRL2891 (SEL/ LZI-2-4).   
 Type locality. Tasmania (~42 o S 147 o E).   
 Description. Based on male, 4.2 mm, AM P71375.   
 Head. Head length less than pereonite 1+2, anterior margin rounded, without serrations or teeth, anterodistal margin quadrate with cusp, ventral cephalic keel with projection, rostrum small to medium; eyes with 10 or more ocelli, round. Antenna 1 0.4 x body length; flagellum 7-articulate, peduncle width less than 2 x article 2. Antenna 2 0.4 x body length, shorter than antenna 1; flagellum 4-articulate. Mandibles lacking molars, palp 3-articulate, ratio of articles 1 – 3, 1.0:3.2:2.1, article 2 with 2 – 3 distal setae, article 3 with 2 distal setae, incisors weakly dentate; left mandible lacinia mobilis large, strongly toothed, with 7 accessory setae; right mandible lacinia mobilis small, with 8 accessory setae. Upper lip asymmetrically lobate, anterior margin setose. Lower lip inner lobes fused, weakly setose; outer lobes with moderate gape, anterior margins strongly setose. Maxilla 1 palp 2-articulate with 4 distal setae; outer plate with 5 distal spines and 3 distal setae. Maxilla 2 inner plate with 5 robust and 12 – 16 thin distal setae; outer plate with 7 distal and 3 proximal setae. Maxilliped inner plates fused, distal margin with v-shaped indentation, with short spines and long setae; outer plate smooth, vestigial, barely exceeding margin of palp article 1, with 5 distal setae, proximal margin lined with short setae; palp 4-articulate, article 4 slender, strongly recurved.   
 Pereon. Coxae 1–4 relative widths 1.0:1.6:1.0:1.2. Gnathopod 1 coxa serrate, setose, anterodistal corner not produced, subtriangular, distal margin straight, posterodistal margin straight, facial setae absent; basis constricted proximally, anterior margin with 5 – 6 setae, posterior margin with 7 short setae; ischium bare; carpus and propodus distally tapered; carpus 0.1 x longer than wide, proximal margin serrate, distal margin bare; propodus straight, palm serrate with 5 distal setae; dactylus smooth, reaching 0.5 x propodus length. Gnathopod 2 coxa length 0.5 x width, much wider than coxa 3, serrate, setose, anterodistally acute, distal margin oblique, posterior margin subquadrate, facial setae absent; basis linear, without tubercles or serrations, anterior margin with 9–10 setae, posterior margin with 5–6 setae; ischium with 2 posterior setae; carpus 0.5 x propodus length, curved, distally truncate, anterior margin smooth; propodus posterior margin without teeth/ serrations, with 2 mediofacial setal rows, primary mediofacial setal row above midline, reaching 0.5 x propodus length, secondary mediofacial setal row with 2 setae, 1 row of 7 submarginal setae, palm convex with 3 major projections; dactylus curved, proximal margin smooth, anterior margin distally subacute, reaching 0.6 x propodus length. Pereopod 3 coxa length 0.6 x width, anterodistal corner over-riding distal face of coxa 2, not extending below it, serrate, setose, anterior margin rounded, distal margin straight, posterior margin straight, facial setae absent. Pereopod 4 coxa serrate, setose, anterior margin straight, distal margin straight, posterior margin straight, facial setae absent. Pereopods 5–7 coxa facial setae absent; basis width length ratios 1:3.0, 1:2.5, 1:2.5, posterior margins smooth, bare.   
 Pleon. Epimera 1–3 bare. Epimeron 3 posteroventral margin subquadrate. Uropods 1–3 relative lengths 1.0:0.8:0.9; inner and outer ramus lined with short marginal setae. Uropod 1 peduncle and inner ramus subequal in length; outer ramus subequal in length with inner ramus. Uropod 2 peduncle 0.8 x inner ramus length; outer ramus 0.6 x inner ramus length; inner ramus with 1 robust seta; outer ramus with robust setae. Uropod 3 peduncle 1.4 x inner ramus length; outer ramus 0.7 x inner ramus length; outer ramus with distal row of serrations. Uropod 1+3 with robust setae. Telson 2.1 x longer than wide, apex tridentate, with 2 plumose distal setae.   
 Female (sexually dimorphic characters). Based on female, 3.5 mm, AM P71096. Gnathopod 2 propodus with fewer mediofacial setae, secondary mediofacial setal row with 4 setae, 1 row of 8 submarginal setae; dactylus with apical protuberance.   
 Habitat. In sponges and calcareous algae.   
 Remarks. Leucothoella gracilis is distinct in its serrate, acute coxae 1 – 4 margins, extremely narrow pereopods 5 – 7 basis, setose spines on pereopods 5 – 7 carpus and plumose distal setae on the telson. The specimens described here differ from previous reports of this species due to the setose proximal margins of the maxilliped outer plates. Females of L. gracilis have a secondary mediofacial setal row similar to L. ashleyae , females of L. assimilis, L. barana, L. kensleyi, L. ubouhu, L. bova sp. nov., L. laevipalma sp. nov., L. makrommatos sp. nov., L. odontiskos sp. nov. and L. undulata sp. nov.   
 Distribution. Australia. Queensland: Yonge Reef; Lizard Island; One Tree Island (current study). New South Wales: Victoria (J.L. Barnard 1974). South Australia: Port Phillip Bay (J.L. Barnard 1974). West Australia: north to Cape Naturaliste (J.L. Barnard 1974); Tasmania (Haswell 1879, Moore 1987).
description: Published as part of White, Kristine N. & Thomas, James Darwin, 2009, Leucothoidae *, pp. 494-555 in Zootaxa 2260 (1) on pages 544-545, DOI: 10.11646/zootaxa.2260.1.29, http://zenodo.org/record/5323471