Gnathostenetroides solitaria sp. nov.

(Figs 18–22)

Material examined. Holotype: ♂ (1.42 mm), northern Great Barrier Reef, Yonge Reef, 14.60694°S, 145.62310°E, 20 April 2008, back reef, dead coral heads, 13 m, CReefs stn CGLI-047A, coll. M. Błażewicz-Paszkowycz (MTQ W31945).

Etymology. The epithet is the Latin word for solitary or alone, in reference to the single specimen of this species.

Description. Terminal male. Body (Fig. 18) length 4.30 width, body height 0.10 of body length. Cephalon almost as long as wide, anterolateral margin of head with 4 setae, rostrum 0.15 cephalon length, 0.40 cephalon width. Eyes of 5 ommatidia located tightly to each other. Pereonite 4 length 0.60 pereonite 1 length; anterolateral projections acute, narrow, distinctly protruded, distal stout UB seta long, lateral margin of pereonites 1–3 with 4–5 setae, pereonite 4 with 2 setae laterally. Posterior body part length 0.40 body length; pereonite 7 length 1.65 pereonite 5 length, lateral margin of pereonites 5 – 7 with 3 – 4 setae. Pleotelson as long as wide, 0.20 body length; lateral margins to posterolateral indentation slightly tapering, with 3 long (1 anterior, 1 middle and 1 in front of denticle), 8 shorter setae and row of 14 small sublateral setae ventrally; posterion margin between indentations subtriangular, moderate projected, length 0.35 pleotelson length; posterolateral margin with 2 long setae directed laterally and 9 long sublateral setae ventrally directed posteriorly, 2 setae on posterior margin.

Antennula (Fig. 19A) length 0.35 body length; article 1 length 3 width, 2.50 as long as rostrum, 1 simple and 2 broom setae distolaterally, distomedially with 2 simple setae and 1 long broom seta; length ratios of articles 2–5 to article 1: 0.70, 0.35, 1.10; article 2 length 2.70 width, distomedially with 1 long broom and 1 simple setae, distolaterally with 1 simple and 2 broom setae; article 3 with 3 simple setae distally; article 4 with 1 simple short distomedial seta, article 5 with tuft of 4 long simple distal setae and 3 aesthetascs.

Antenna (Fig. 19B, C): left antenna shorter than right antenna, longer antenna length 0.65 body length, peduncle articles 1 – 4 reaching tip of antennula article 2. Article 3 scale with 3 lateral setae; article 4 with 2 small distal setae. Article 5 length 1.35 articles 1 – 4 total length; article 6 length 1.25 article 5 length, articles 5 and 6 with scattered long setae, article 6 with 2 broom setae distally, length together 0.30 body length. Flagellum of 15 articles, first article about 3 times longer than following ones, each article with few small distal setae.

Mandible (Fig. 20A, B) pars incisiva with 5 cusps; lacinia mobilis of left mandible broadening distally, almost reaching tip of pars incisiva, with 5 teeth; spine row with 7 and 8 spines on left and right mandibles respectively; pars molaris with 2 setae, length 0.65 pars incisiva length; palp length 0.90 mandibular body length, article 1 with 2 long distal setae, article 2 length 2 times article 1 length, with 3 short setae and 2 long distally serrated setae on distolateral half; article 3 with rows of cleaning setae gradually elongating from short proximal seta to long distal seta. Maxilla 1 (Fig. 20C) lateral endite width 2 mesial endite width, distally with 11 denticulate setae, setae length 0.70 endite width. Maxilla 2 (Fig. 20D) lateral and middle endite subequal in length, with 4 long distal setae each; mesial endite shortest, as wide as middle and lateral endites together, with numerous distal setae and distomedially few comb-like setae. Maxilliped (Fig. 20E) basis length 4.40 width, endite length 1.50 width, with 3 coupling hooks, distal margin slightly concave, with 5 broad fan-like setae and numerous simple slender setae; palp 0.50 as long and 0.70 as wide as basis and inserted after 0.5 basis length, article 2 as long as wide, medial margin length 1.25 lateral margin length, medial margin with 4 whip setae; articles 3 – 5 subequal in length as long as article 2 laterally, article 3 medial margin length 0.80 medial length of article 2, with 6 long setae; article 4 with 5 long distal setae; article 5 slender, with 4 long distal setae. Epipod length 4 width and 0.80 basis length.

Pereopod 1 (Fig. 21A) length 0.45 body length, length ratios of ischium–dactylus to basis: 0.50, 0.45, 0.30, 1.15, 0.75; basis length 3.60 width; ischium length 1.75 width, with 1 distoventral and 2 dorsal setae; merus length 1.20 width, ventral margin with 4 setae; carpus length 1.35 width, with 13 ventral long setae; propodal palm subtriangular, length 2.10 width, ventral margin length 0.70 dorsal margin length, with 4 long strong UB setae, distoventral spine-like UB seta length 0.45 anterior margin length, anterior margin with 7 setulated setae; dactylus with claw length 5.85 width, ventral (inner) margin with 7 slender short setae, claw length 0.30 dactylus length, small serrated seta ventrally, 2 long slender setae in between, 3 whip setae proximally to claw.

Length ratios of pereopods 2–7 to pereopod 1: 0.60, 0.50, 0.50, 0.45, 0.55, 0.55 (Fig. 21). Pereopod 2 (Fig. 21B) length ratios of ischium–dactylus to basis: 0.65, 0.40, 0.70, 0.70, 0.30; basis length 2.85 width, dorsal margin with 2 small setae, ischium length 2.40 width, with 1 strong dorsal seta; merus length 1.70 width, with 1 distoventral simple seta and 1 strong distodorsal seta; carpus length 3.90 width, with 2 ventral setae and 1 small distodorsal seta; propodus length 4.65 width, with 3 stout ventral whip setae; dactylus claws length 0.30 total length, 3 setae proximally claws, 1 seta between claws.

Pereopod 3 (Fig. 21C) length ratios of ischium–dactylus to basis: 0.65, 0.40, 0.65, 0.65, 0.30; basis length 2.80 width, dorsal margin with 2 small setae; ischium length 2.65 width, with 2 small and i strong dorsal setae, 2 ventral small setae; merus length 1.85 width, with 1 distoventral and 1 distodorsal small setae; carpus length 3.50 width, with 1 distodorsal and 2 ventral small setae; propodus length 3.50 width, with 4 ventral setae, and 2 distodorsal simple setae; dactylus length 2.20 width, claw length 0.50 dactylus length.

Pereopod 4 (Fig. 21D) equal in length to pereopod 3, length ratios of ischium–propodus to basis: 0.65, 0.45, 0.75, 0.85; 0.35; basis length 2.15 width, with 2 dorsal simple setae; ischium length 2.50 width, 1 dorsal and 1 ventral setae; merus length 1.45 width, with 1 distoventral seta; carpus length 3.15 width, with 2 ventral setae and 1 dorsal simple setae; propodus length 4.30 width, with 1 distodorsal and 4 ventral simple setae; dactylus length 2.20 width with 1 seta between claws.

Pereopod 5 (Fig. 21E) length ratios of ischium–dactylus to basis: 0.65, 0.35, 0.55, 0.65, 0.30; basis length 2.50 width, with 3 dorsal setae; ischium length 3.10 width, with 1 dorsal and 1 ventral setae; merus length 1.35 width, with 1 distodorsal and 1 distoventral setae; carpus length 3.0 width, with 2 ventral setae; propodus length 3.20 width with 2 long whip ventral setae and 1 distoventral UB and 2 distodorsal small setae; dactylus length 2.50 width, claw length 0.50 dactylus total length, ventral claw slightly broader than dorsal claw.

Pereopod 6 (Fig. 21F) length ratios of ischium–dactylus to basis: 0.65, 0.30, 0.55, 0.60, 0.25; basis length 2.50 width, with 2 dorsal setae; ischium length 3.25 width, with 1 dorsal seta; merus length 1.35 width with 2 distoventral and 1 distodorsal setae; carpus length 3.15 width, with 2 ventral and 1 distodorsal simple setae; propodus length 4.0 width, with 2 long whip ventral setae, one UB distoventral seta and 2 distodorsal small setae.

Pereopod 7 (Fig. 21G) length ratios of ischium–dactylus to basis: 0.70, 0.35, 0.60, 0.65, 0.25; basis length 3.1 width, with 2 dorsal and 1 ventral simple setae; ischium length 3.25 width, with 1 whip dorsal seta and 3 small ventral setae; merus length 1.35 width, with 1 distoventral and 1 distodorsal setae; carpus length 3.40 width, with 2 ventral and 1 distodorsal setae; propodus length 4.80 width, with 3 long whip ventral setae, 1 distoventral UB seta and 1 distodorsal small seta; dactylus length 2.60 width.

Pleopod 1 (Fig. 22A) length 1.30 pleopod chamber length; pleopod length 1.50 width, distal margins rounded, with 9–11 setae each. Pleopod 2 (Fig. 22C) protopod length 1.65 width, 0.35 pleopod 1 length, lateral margin without setae, endopod article 1 length 0.50 protopod length, article 2 length 0.70 protopod length, exopod length 1.35 width, 0.20 protopod length. Pleopod 3 (Fig. 22D) protopod length 0.90 width, endopod length 1.85 width, distal plumose setae 0.50 endopod length, position: 1 distomedial seta separated from 2 distolateral setae closely located to each other; exopod length 6.90 width, 1.60 endopod length and 0.45 endopod width, article 1 with 3 slender setae laterally, distal article separated, length 0.40 basal article length, with 2 distal setae. Pleopod 4 (Fig. 22E) endopod length 1.80 width, exopod length 0.65 endopod length, width 0.30 endopod width, 2 simple fine setae laterally. Pleopod 5 (Fig. 22E) length 2.05 width.

Uropod (Fig. 22F) 0.40 pleotelson length. Protopod length 1.55 width, lateral margin with 3 distal setae, medial margin slightly convex with 2–3 setae; 5 setae distally; endopod length 6 width and 1.90 protopod length, with 3 medial setae and 6 simple long and 2 broom setae distally; exopod length 6.0 width, 0.60 endopod length, with 5–6 long distal setae.

Female. Not known.

Remarks. The species differs from most species of Gnathostenetroides in having a relatively stout body (L/W 4.30), with only G. pugia being more stout (L/W 3.90); most species are slender L/W (4.60 – 5.50). The pleotelson is wider than the cephalon and uropods are relatively short, 0.40 pleotelson length (0.50–0.60 in other three described new species). The male pereopod 1 propodus broadens distally, with a convex anterior margin. The spine-like UB seta is situated more proximally from a distoventral corner.

Distribution. Known only from the type locality, Yonge Reef; at a depth of 13 metres.