Joeropsis mije, Bruce, Niel L., 2015

Bruce, Niel L., 2015, Joeropsididae Nordenstam, 1933 (Crustacea, Isopoda, Asellota) from the Lizard Island region of the Great Barrier Reef, Queensland, Australia, ZooKeys 491, pp. 1-62 : 26-29

Taxon classification Animalia Isopoda Joeropsididae

Joeropsis mije sp. n. Figs 14, 15, 16

Material.

All material from the Lizard Island region, including outer barrier reefs.

Holotype. ♂ (1.8 [part dissected], 1.4 mm), Yonge Reef, 14.60681°S, 145.6311°E, 20 February 2009, outer reef front, dead coral, 30 m, stn LIZ09-15B, coll. S. Smith & JC (MTQ W31908, including dissection slide).

Paratypes. ♀ (ovig 1.4 mm [dissected]), Hicks Reef, 14.44803°S, 145.4992°E, 21 February 2009, outer reef front, small coral heads and rubble, 15 m, coll. MB-P & NLB, stn LIZ09-16C coll. NLB & MB-P (MTQ W31911). ♀ (non-ovig 1.1 mm), Hicks Reef, 14.44803°S, 145.4992°E, 21 February 2009, outer reef front, dead coral heads on reef edge, 5-7 m, LIZ09-16E, coll. NLB & MB-P (MTQ W31909). 2 ♂ (1.2, 1.0 mm), Day Reef, 14.48356°S, 145.5459°E, 13 February 2009, outer reef, fine rubble, 10 m, stn LIZ09-04C, coll. MB-P (MTQ W31910). ♂ (1.1 mm, poor condition), Day Reef, 14.48356°S, 145.5459°E, 13 February 2009, outer reef, coral heads in gully, 10 m, LIZ09-04B, coll. MB-P (MTQ W31906). ♀ (ovig. 1.3 mm), Day Reef, 14.47119°S, 145.5297 °E, 13 February 2009, outer reef, coral rubble in cave on vertical wall, 10-12 m, stn LIZ09-03B, coll. MB-P (MTQ W31907). ♂ (1.1 mm), Day Reef, 14.48283°S, 145.5564°E, 19 February 2009, outer reef front, small rubble in gully, 7.5 m, stn LIZ09-13A, coll. MB-P & NLB (MTQ W31284). ♂ (1.6 mm), Yonge Reef, 14.61383°S, 145.6182°E, 18 February 2009, back reef, small coral rubble on sand, 15 m, stn LIZ09-10F, coll. MB-P & NLB (MTQ W31283; microscope slide). ♂ (1.0 mm), ♀ (non-ovig 1.2 mm), Hicks Reef, 14.44803°S, 145.4992°E, 21 February 2009, outer reef front, coral rubble under bommie overhang, 15 m, stn LIZ09-16B, coll. NLB & MB-P (MTQ W31912).

Also examined. Holotype of Joeropsis minuta Müller, 1989. ♂ (1.0 mm), Französisch Polynesien, Iles du Vent, Mooréa. Temae, Islet Riff, NE vom Flughafen, tote Korallen nahe Strand, 2 m, Tiefe, tote Korallen, 31 March 1988, coll. H.-G. Müller (SMF 17689); 6 ♂ and ♀ paratype dissection, 6 microslides (SMF 17692). Near of airport, Tema’e, Mooréa, French Polynesia, c. 17.49°S, 149.76°W.

Description.

Body 2.9 as long as greatest width, dorsal surfaces smooth, with few setae. Cephalon length 0.6 width, lateral margins weakly concave, finely serrate (at mid-length). Pseudorostrum 1.5 as long as proximal width (with longitudinal ridge), anterior margin acute. Eyes lateral, with 12 ommatidia, colour orange. Pereonites not compact, widely spaced, without dorsal carinae; tergite lateral margin truncate, lateral margins smooth; median keels not observed. Pleotelson width 1.4 length; dorsal surface with weak and indistinct sub-lateral ridge, caudomedial lobe broadly rounded, not extending posteriorly beyond uropods; lateral margins weakly convex, each with 6-7 spines.

Antenna 1 with 5 articles; article 1 1.0 as long as wide, distolateral angle not lobed, strongly serrated, distomesial margin weakly serrate; article 2 0.8 as long as article 1, 1.3 as long as wide; lateral margins of articles 1 and 2 with weak cuticular scales on distal margins; article 3 0.2 as long as article 2; article 4 1.7 as long as article 3 (articles 3 and 4 distal angles acute); article 5 2.7 as long as article 3, 1.9 as long as proximal width. Antenna 2 peduncle article 5 1.8 as long as articles 1-4 combined, 4.8 as long as article 3, 1.2 as long as wide, lateral margin strongly convex, with prominent cuticular scales (and evenly spaced marginal setae), mesial margin convex; article 6 1.4 as long as width, distally weakly expanded, distal width 1.6 proximal width, 0.5 as long as article 5, lateral margin without cuticular scales, mesial margin with 12 simple setae, distodorsal surface with scattered simple setae; flagellum with 5 articles, article 1 0.8 as long as peduncle article 6, 2.1 as long as combined lengths of remaining articles.

Mandible palp article 2 with 2 long biserrate setae, article 3 with 3 long pectinate setae. Right incisor with symmetrical cusps, margins convex, distally acute. Molar process distal quarter finely serrate. Right mandible spine row composed of 9 spines. Maxilla 1 lateral lobe with 12 strongly serrate RS, and 2 simple RS; mesial lobe with 4 long, simple RS. Maxilla 2 lateral lobe with 4 long, curved, finely serrate setae (2 short, 2 long); middle lobe with 4 long serrate setae (2 short, 2 long), mesial lobe with 4 long simple setae and many long setules. Maxilliped endite 2.3 as long as greatest width, extending beyond palp, distal margin subtruncate, with 4 prominent serrations, with shallow distomesial concavity, with 3 mesial tubercular RS (and laterally with 1 distal rounded and finely serrated RS), distomesial margin with 2 coupling setae. Maxilliped palp article 2 3.6 as long as article 1, mesial lobe extending to article 4, distomesial margin with 3 simple setae; article 3 0.3 as long as article 2 (with ventral lobe), distomesial margin with 1 simple seta; article 4 4.2 as long as wide, mesial margin straight, distally with 2 setae; article 5 0.1 as long as 4, with 2 terminal setae.

Pereopod 1 ischium 2.3 as long as wide; merus 0.6 length of ischium, 1.7 as long as wide; carpus 0.8 as long as ischium, 2.2 as long as wide; propodus 3.8 as long as wide, superior margin 2 simple setae (and prominent penicillate seta at distal angle); inferior margin with 2 acute RS, dactylus 0.5 as long as propodus, with 2 claws. Pereopods 2-7 sub-similar, more slender than pereopod 1, each with 3 claws. Pereopod 7 ischium 2.4 as long as wide, superior margin weakly convex at midpoint, with 1 simple seta, inferior distal angle with 1 seta; merus 0.6 as long as ischium, 1.7 as long as wide, superodistal angle with 2 simple setae; carpus 0.8 as long as ischium, 2.1 as long as wide, inferior margin with 1 simple seta, superior distal angle with 2 prominent pappose setae; propodus 1.0 as long as ischium, 3.3 as long as wide, inferior margin with 3 acute RS, superior margin with 2 simple setae; dactylus 0.6 as long as propodus.

Pleopod 1 2.0 as long as greatest width, lateral margin strongly concave with mid-length straight, apical lobe broadly rounded, with short marginal setae, lateral margin with slender setae, distolateral lobe blunt, not extending to distal margin. Pleopod 2 protopod 2.3 as long as midwidth, lateral margin mid-half weakly convex, without setae (with fine cuticular scales), distal margin straight, without marginal cuticular scales (with setae), apex acute; stylet in retracted position extending beyond apex. Pleopod 3 endopod 2.3 midwidth (medially fused to protopod); exopod article 1 3.5 as long as wide, extending beyond apex, lateral margin densely fringed with cuticular scale-setae; article 2 0.5 as long as article 1, lateral and mesial margins with short cuticular scale-setae (mesial margin with 3 setae).

Uropod peduncle extending well beyond margin of pleotelson, mediodistal corner strongly produced and acute, distolateral margin with 4 simple submarginal setae, mesial margin serrate. Exopod 0.5 as wide as endopod, 0.9 as long as wide, with 4 simple setae. Endopod 1.0 as long as wide, 0.8 as long as peduncle proximolateral margin, apex with 3 long simple setae.

Female.Pleopod 2 1.3 as long as proximal width, lateral margins weakly convex, posterior margins straight, apex with 2 sub-apical simple setae (surface with sub-mesial row of setae). Antenna 2 peduncle article 5 not broadly expanded.

Colour pattern.

Head with diffuse, low-density transverse dark-brown band across the anterior 50% of the head; dorsal surfaces otherwise with few and faint chromatophores, mostly on pereonites 5-7 and anterior of pleotelson.

Size.

Males 1.0-1.8 mm (average 1.2 mm, n=8); ovigerous females 1.3-1.4 mm and non-ovigerous females 1.1-1.2 mm.

Remarks.

Joeropsis mije sp. n. is the smallest of the currently known Australian species of this genus and is best identified by the small size, acute pseudorostrum, diffuse dark brown head band, head lateral margin with two to four serrations just posterior to the eye, and the presence of only a few chromatophores over the dorsum; males are distinctive in having antenna 2 peduncle article 5 with an almost circular outline, a character readily observed in dorsal view.

Joeropsis minuta Müller (1989, fig. 30) is closely similar to Joeropsis mije sp. n. but the latter can be distinguished by the following characters (state for Joeropsis minuta in parentheses): head lateral margin weakly convex (mid-lateral margin weakly concave), pseudorostrum 2.5 as long that wide (as long as wide), pereonites widely spaced with lateral margins not in contact (closely spaced, pereonites 1-4 overlapping slightly) and pleotelson caudomedial lobe not extending posteriorly beyond uropods (extending beyond uropods).

Distribution.

Hicks, Day and Yonge Reefs (Fig. 1); depths 10 to 15 metres.

Etymology.

The epithet is an Aboriginal word meaning little, alluding to the small size of this species; noun in apposition.