Leucothoe adelphe, White & Thomas, 2009

White, Kristine N. & Thomas, James Darwin, 2009, Leucothoidae *, Zootaxa 2260 (1), pp. 494-555 : 498-501

Leucothoe adelphe sp. nov.

( Figs 3 , 4 )

Type material. Holotype, male, 1.6 mm, AM P 71436, Three Sisters Bommie, Yonge Reef (14°36.104’S 145°37.126’E), coral rubble, back reef bommie, 17 m, C. Rakocinski, 3 March 2005 ( QLD 1792 ) . Paratype, female, 1.9 mm, AM P 71271 , Horseshoe Reef , Lizard Island (14°41.21’S 145°26.49’E), clump of fibrous brown algae, large coral bommies surrounded by sand and rubble, 6 m, L . Hughes, 2 March 2005 ( QLD 1767 ) .

Additional material examined. 3 males, AM P 79819 ( JDT / LIZ 15 ) .

Type locality. Yonge Reef , Lizard Island, Queensland, Australia (14°36.104’S 145°37.126’E) .

Etymology. After the Greek ‘ adelphe ’, meaning ‘sister’ and referring to the type locality.

Description. Based on holotype, male, 1.6 mm, AM P71436.

Head. Head length less than pereonite 1+2, anterior margin weakly convex, without serrations or spines, anterodistal margin rounded with cusp, ventral cephalic keel transverse, rostrum small to medium; eyes with 10 or more ocelli, round. Antenna 1 0.3 x body length; flagellum 5-articulate, peduncle width less than 2 x article 2. Antenna 2 0.3 x body length, subequal to antenna 1; flagellum 5-articulate. Mandibles left mandible missing; right mandible lacking molar; incisor strongly dentate; lacinia mobilis small, with 7 accessory setae; palp 3-articulate, ratio of articles 1 – 3, 1.0:2.2:1.1, article 2 with 1 distal seta, article 3 with 2 distal setae. Upper and lower lips and maxillae 1–2 missing. Maxilliped inner plates fused, distal margin notched, with short spines; outer plate smooth, reduced, reaching much less than half of palp article 1, with 3 proximal and 2 facial setae; palp 4 - articulate, article 4 wide, slightly recurved.

Pereon. Coxae 1–4 relative widths 1.0:0.9:1.1:1.4. Gnathopod 1 coxa smooth, bare, anterodistal corner produced, narrowly rounded, distal margin straight, posterodistal angle subquadrate, facial setae absent; basis slightly inflated, anterior and posterior margins bare; ischium bare; carpus and propodus distally tapered; carpus length 9 x width, proximal margin with 2 dentitions, distal margin with 4 setae; propodus straight, palm dentate with 5 distal setae; dactylus smooth, reaching 0.1 x propodus length. Gnathopod 2 coxa length subequal to width, slightly narrower than coxa 3, anterior margin smooth, anterodistally rounded, distal margin evenly rounded, posterior margin straight, facial setae absent; basis stout, widened distally, without tubercles or serrations, anterior and posterior margins bare; ischium bare; carpus 0.3 x propodus length, gently curved, distally truncate, anterior margin smooth; propodus posterior margin without spines/serrations, with 1 mediofacial setal row above midline, reaching approximately 0.5 x propodus length, 1 row of 8 submarginal setae, palm convex with 4 blunt projections; dactylus recurved, proximal margin smooth, anterior margin distally subacute, reaching 0.7 x propodus length. Pereopod 3 coxa length subequal to width; smooth, bare, anterodistal corner over-riding distal face of coxa 2 and extending below it, anterior margin evenly rounded, distal margin oblique, posterior margin evenly rounded, facial setae absent. Pereopod 4 coxa smooth, bare, anterior margin evenly rounded, distal margin evenly rounded, posterior margin mildly excavate, facial setae absent. Pereopods 5–7 coxa facial setae absent; basis width length ratios 1:1.7, 1:1.9, 1:1.5, posterior margins smooth, bare.

Pleon. Epimera 1–3 bare. Epimeron 3 posteroventral margin subquadrate. Uropods 1–3 relative lengths 1.0:0.7:1.0; outer ramus 0.8 x inner ramus length. Uropod 1 peduncle 0.7 x inner ramus length. Uropod 2 peduncle 0.8 x inner ramus length. Uropod 1–2 inner ramus proximal margin lined with short setae, with robust setae; outer ramus distal margin lined with short setae, with robust setae. Uropod 3 peduncle and inner ramus subequal in length; inner and outer ramus proximal and distal margins lined with short setae; inner ramus with robust setae, outer ramus with 1 robust seta. Telson 1.7 x longer than wide, apex with weak point.

Female (sexually dimorphic characters). Based on paratype, female, 1.9 mm, AM P 71271. Gnathopod 1 carpus proximal margin without strong dentitions, weakly dentate anterodistally; propodus palm with fewer dentitions. Gnathopod 2 basis anterior margin with 2 long and 2 short setae, anterodistal margin with row of 4 short setae; propodus mediofacial setal row with fewer setae; submarginal setal row with 5 setae; dactylus distally acute .

Habitat. In coral rubble and fibrous brown algae from back reef bommies.

Remarks. This species appears to be closely related to Leucothoe micronesiae J.L. Barnard, 1965 and Leucothoe minuscula Schellenberg, 1938 based on the small size, short mediofacial setal row and strong dentition of the gnathopod 2 propodus palm. J.L. Barnard (1965) noted that the only difference between L. micronesiae and L. minuscula was the size and development of the female gnathopod 2. Closer examination suggests that these species may need to be synonymised. Leucothoe adelphe sp. nov. differs from L. micronesiae and L. minuscula in its narrow, smooth basis of pereopods 5 – 7, its rounded propodus on gnathopod 2 and its shorter, less recurved propodus of gnathopod 1. The strong dentition of the gnathopod 2 propodus palm is shared with Leucothoe ashleyae Thomas & Klebba, 2006 , Leucothoe hornelli Walker, 1904 , Leucothoe stegoceras Walker, 1904 , Leucothoe rudicula sp. nov. and Leucothoe serrata sp. nov., but differs in most other respects, namely the short gnathopod 1 dactylus. These species share the general shape of gnathopod 1 with species in the genus Paraleucothoe ; however, the propodus of L. adelphe sp. nov. is much narrower than in Paraleucothoe .

Distribution. Australia. Queensland: Yonge Reef and Horseshoe Reef, Lizard Island (current study).

Figures

FIGURE 3. Leucothoe adelphe sp. nov., holotype, male, 1.6 mm, AM P71436 (QLD 1792), Three Sisters Bommie, Yonge Reef, Great Barrier Reef; paratype, female, 1.9 mm, AM P71271 (QLD 1767), Horseshoe Reef, Lizard Island, Great Barrier Reef.

FIGURE 4. Leucothoe adelphe sp. nov., holotype, male, 1.6 mm, AM P71436 (QLD 1792), Three Sisters Bommie, Yonge Reef, Great Barrier Reef; paratype, female, 1.9 mm, AM P71271 (QLD 1767), Horseshoe Reef, Lizard Island, Great Barrier Reef.