Gnathia wistari, N, Jörundur Svava R S S O & Bruce, Niel L., 2012

N, Jörundur Svava R S S O & Bruce, Niel L., 2012, New and little-known gnathiid isopod crustaceans (Cymothoida) from the northern Great Barrier Reef and the Coral Sea, Zootaxa 3380, pp. 1-33 : 26-31

Gnathia wistari sp. nov.

( Figs 18–21 )

Material examined. Holotype. 3, 3.7 mm, off northern Wistari Reef, Qld, 7 November 1978, 22 m, sediment, coll. D. Fisk (QM W24256).

Paratypes. 2 3, same data as holotype (MTQ W10676 [dissected, 12 microslides], 3 at IMNH 2725). 1 3, Wistari reef, 3 December 1979, 21 m, from dead coral, coll. N.L. Bruce (MTQ W10675). Lizard Island Series: 2 3, McGillivray’s Reef, 14.38567°S, 145.46710°E, 18 April 2008, 18 m, dead coral, CReefs stn CGLI 040B, M. Schlacher & T. Hendricks (MTQ W14159). 2 3, Yonge Reef, 14.57972°S, 145.61010°E, 20 April 2008, passage, 17– 15 m, rubble, CReefs stn CGLI 046C, coll. M. Błażewicz-Paszkowycz (MTQ W14158). 2 3, Day Reef, 14.48356°S, 145.5459°E, 13 February 2009, outer reef, flat rubble in gully, 10 m, CReefs stn LIZ09 04A, coll. M. Błażewicz-Paszkowycz (MTQ W30461). 1 3, Day Reef, 14.48539°S, 145.5464°E, 19 February 2009, outer reef front, coarse sand and fine rubble, 19 m, CReefs stn LIZ09 12C, coll. N. Bruce & M. Błażewicz-Paszkowycz (MTQ W31068). 1 3, Day Reef, 14.48539°S, 145.5464°E, 19 February 2009, outer reef front, coral rubble in gully, 17 m, CReefs stn LIZ09 12F, coll. N. Bruce & M. Błażewicz-Paszkowycz (MTQ W31053). 14 3, Hicks Reef, 14.44803°S, 145.4992°E, 21 February 2009, outer reef front, small coral heads and rubble, 15 m, CReefs stn LIZ09 16C, coll. N. Bruce & M. Błażewicz-Paszkowycz (MTQ W30462). 8 3, Day Reef, 14.50525°S, 145.5612°E, 22 February 2009, outer reef front, coral rubble, 27–29 m, CReefs stn LIZ09 17A, coll. S. Smith & J. Caley ( IMNH 2794).

Other non-type material. 1 3, Lizard Island, stn 7, 1980, coll. N.L. Bruce (MTQ W10737), 2 3, Lizard Island, stn 31, 1980, coll. N.L. Bruce (MTQ W10738).

Description. Body 3.1 times as long as greatest width, widest at pereonite 2 and pereonite 3; dorsal surfaces smooth, sparsely setose. Cephalosome quadrate, 0.8 as long as wide, lateral margins parallel; dorsal surface smooth and with sparse granules; dorsal sulcus wide, shallow, extended; translucent region absent; paraocular ornamentation weakly developed, posteromedian tubercle present. Frontolateral processes present. Frontal margin straight, median point with process. External scissura present, narrow, shallow. Mediofrontal process present, weak, rounded, without ventral notch, without fine setae. Supraocular lobe pronounced, wide; accessory supraocular lobe not pronounced. Superior frontolateral process present, strong, unequally apically bifid, without long simple setae. Inferior frontolateral process absent. Mesioventral margin straight. Eyes present, round, 0.3 as long as cephalosome length, contiguous with head surface, ommatidia arranged in rows, eye colour faded yellow.

Pereon lateral margins narrowing posteriorly, with few setae; anteriorly smooth. Pereonite 1 not fused dorsally with cephalosome; dorsolateral margins not obscured by cephalosome; pereonite 2 as wide as pereonite 1; areae laterales present on pereonite 5; pereonite 6 without lobi laterales; lobuii absent. Pleotelson 1.1 times as long as anterior width, lateral margins smooth, anterolateral margins weakly concave, posterolateral margin distally concave; mid-dorsal surface with 1 sub-median seta, anterolateral margin with 1 submarginal seta, posterolateral margin with 1 submarginal seta, apex with 2 setae.

Antennule peduncle article 2 1 times as long as article 1, article 3 1.7 times as long as article 2, 4.8 times as long as wide; flagellum 1.4 as long as article 3, with 5 articles. Antenna peduncle article 4 2.4 times as long as wide, 1.6 times as long as article 3, with 1 penicillate seta, and 8 simple setae; article 5 1.4 times as long as article 4, 2.9 times as long as wide, inferior margin with 5 penicillate setae, with 15 simple setae; flagellum 1.5 as long as article 5, with 7 articles.

Mandibl e 0.6 as long as width of cephalosome, mandible triangular, weakly curved, distally; mandible apex 25% total length; mandibular seta present. Carina present, smooth, along entire length. Incisor knob-like, distal denticulation absent. Blade present, dentate, strongly convex, midventrally convex, along proximal 40% of margin. Pseudoblade absent; internal lobe present, bifid, large, crenulate; dorsal lobe absent; basal neck short; erisma absent; lamina dentata absent.

Maxilliped 5-articled. Maxilliped article 1 lateral margin with continuous marginal scale-setae; article 2 lateral margin with 3 plumose setae; article 3 lateral margin with 8 plumose setae; article 4 lateral margin with 5 plumose setae; article 5 with 8 plumose setae; endite extending to distal margin of article 2; without coupling setae. Pylopod article 1 1.7 as long as wide, without distolateral lobe; posterior and lateral margins forming rounded curve; lateral margin with 30 large PMS; mesial margin with continuous scale-setae, distal margin with 3 long simple setae; article 2 1.6 as long as wide; article 3 absent, without setae.

Pereopods 2–6 without long plumose setae; propodus distal RS slightly longer than proximal RS; lateral and inferior margins with weak tubercles, pereopod 2 with tubercles on merus and carpus. Pereopod 2 basis 2.4 times as long as greatest width, superior margin 5 long setae, inferior margin 5 setae; ischium 0.7 times as long as basis, 2.3 as long as wide, superior margin with 4 setae, inferior margin with 5 setae; merus 0.6 as long as ischium, 1.6 as long as wide, superior margin with 2 long setae, inferior margin with 5 long setae; carpus 0.6 as long as ischium, 2.3 as long as wide, superior margin with 2 long setae, inferior margin with 3 setae (1 biserrate); propodus 0.5 times as long as ischium, 3.8 times as long as wide, superior margin 3 long setae (and one penicillate), inferior margin with 1 short seta, 2 long simple setae, and 2 RS; dactylus 0.7 as long as propodus. Pereopods 3 and 4 similar to pereopod 2. Pereopod 5 similar to pereopod 6. Pereopod 6 with tubercles on superior margin of basis, basis 2.5 times as long as greatest width, superior margin with 6 long setae, and no penicillate setae, inferior margin with 3 long setae; ischium 0.7 as long as basis, 2.3 as long as greatest width, superior margin with 5 long setae, inferior margin with 8 long setae; merus 0.6 as long as ischium, 1.5 times as long as wide, superior margin with 4 long setae (2 biserrate), inferior margin 4 long setae, with dense patch of scale-setae; carpus 0.5 as long as ischium, 1.9 times as long as wide, superior margin with 4 long setae, inferior margin with 6 long setae (1 biserrate); propodus 0.8 as long as ischium, 3.2 times as long as wide, superior margin with 4 long setae (1 penicillate), inferior margin with 3 long setae, and 2 RS; dactylus 0.7 as long as propodus. Penes opening flush with surface of sternite 7.

Pleopod 2 exopod 2.1 as long as wide, 9 PMS; endopod 1.9 as long as wide, endopod with 8 PMS. Pleopod 2 appendix masculina absent.

Uropod rami extending beyond pleotelson, apices broadly rounded. Peduncle with 1 dorsal seta. Endopod 2.5 as long as greatest width, dorsally with 5 sensory setae; lateral margin weakly sinuate, lateral margin with 2 simple setae; mesial margin strongly convex, with 6 long plumose setae. Exopod not extending to end of endopod, 3.8 times as long as greatest width; lateral margin weakly convex, with 7 simple setae (and 1 submarginal seta); proximomesial margin straight, distally convex, mesiodistal margin with 4 long PMS.

Remarks. Gnathia wistari sp. nov. is similar to Gnathia aureamaculosa Ferreira and Smit, 2009 in having large mesial lobes on the mandible. These two species can, however readily be distinguished by the shape of the mandible, which is rectangular in G. aureamaculosa and triangular–oval in Gnathia wistari , and by the shape of the superior frontolateral processes, being apically bifid in G. w i s t a r i, but conical in G. aureamaculosa .

Etymology. Named for the type locality; noun in apposition.

Distribution. Gnathia wistari sp. nov. is known from both the northern and southern Great Barrier Reef; recent collections from the northern Great Barrier Reef indicate that it occurs most commonly on the outer reefs rather than mid-shelf and continental island reefs; at depths of 8–29 metres.

Figures

FIGURE 18. Gnathia wistari sp. nov. A, habitus, 3, holotype, 3.7 mm (QM W 24256), B – E, 3, paratype, 3.3 mm (MTQ W 10676). B, cephalosome, dorsal view. C, cephalosome, dorso-lateral view. D, cephalosome, lateral view. E, cephalosome, ventral view. Scale = 1.0 mm.

FIGURE 19. Gnathia wistari sp. nov, 3, paratype, 3.3 mm (MTQ W 10676). A, antennule. B, antenna. C, maxilliped. D, pylopod. E, second article of pylopod.

FIGURE 20. Gnathia wistari sp. nov, 3, paratype, 3.3 mm (MTQ W 10676). A, pereopod 2. B, propodus and dactylus of pereopod 2. C, pereopod 6. D, propodus and dactylus of pereopod 6.

FIGURE 21. Gnathia wistari sp. nov, 3, paratype, 3.3 mm (MTQ W 10676). A, pleopod 2. B, pleotelson and outline of uropod. C, uropod.