Joeropsis adusta, 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 : 9-13

Taxon classification Animalia Isopoda Joeropsididae

Joeropsis adusta sp. n. Figs 2, 3, 4

Material.

Holotype. ♂ (1.6 mm), 'High Rock’, east of South Direction Island, 14.82428°S, 145.55270°E, 11 September 2010, clean coral rubble 6.0 m, stn LI10-134C, coll. CB (MTQ W33715).

Paratypes. 13 ♂ (1.1-1.6 mm; 3 damaged), 31 ♀ (11 ovig 1.4-1.8; 20 non-ovig. 1.1-1.7mm), same data as holotype (MTQ W33033). ♂ (2.0 mm), ♀ (ovig 2.2 mm), 2 imm. (1.6, 1.2 mm), Seabird Islet, patch reef, in from lagoon entrance, 14.68900°S, 145.46710°E, 11 April 2008, dead coral heads 1.0-2.0 m, stn CGLI-18A, coll. NLB & MB-P (MTQ W13975).

Additional material. 3, Bommie Bay, Lizard Island, 14.66127°S, 145.47130°E, 2 September 2010, dead coral, 6.5 m, stn LI10-57D, coll. CB (MTQ W32756). 12, Bommie Bay, Lizard Island, 14.66127°S, 145.47130°E, 2 September 2010, dead coral on bommie, 3 m, stn LI10-057A, coll. CB (MTQ W32743). 1, Bommie Bay, Lizard Island, 14.66127°S, 145.47130°E, 2 September 2010, coral rubble at base of bommie, 6 m, stn LI10-057B, coll. CB (MTQ W32747). 7, Bommie Bay, Lizard Island, 14.66157°S, 145.47160°E, 8 September 2010, dead coral, 8 m, stn LI10-101B, coll. CB (MTQ W32937). 1, Bommie Bay, Lizard Island, 14.66157°S, 145.47160°E, 8 September 2010, dead coral on wall, 10 m, stn LI10-100C, coll. CB (MTQ W32556). 1, High Rock, 14.82553°S, 145.55170°E, 6 September 2010, fine coral rubble, 6 m, stn LI10-091D, coll. CB (MTQ W32903). 2, High Rock, east of South Direction Island, 14.82462°S, 145.5520°E, 6 September 2010, dead Acropora plates, 4 m, stn LI10-092B, coll. CB (MTQ W32921). 1, 'Washing Machine’, northwest Lizard Island, 14.6482°S, 145.4570°E, 2 September 2010, coral rubble at base of reef, 12 m, stn LI10-056C, coll. CB (MTQ W32730). 9, Yonge Reef, 14.57735°S, 145.61050°E, 10 September 2010, lee side (western) of reef, coral rubble, 10 m, stn LI10-127A, coll. CB (MTQ W32992). 2, Yonge Reef, 14.57735°S, 145.61050°E, 10 September 2010, lee side (western) of reef, coarse coral rubble, 25 m, stn LI10-127F, coll. CB (MTQ W31809). ♀ (non-ovig. 1.3 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 W34025).

Also examined. Joeropsis salvati Müller, 1989; holotype (microslides-SMF 17697) and paratypes (SMF 17690, part; ♀ 1.6 mm, 2 imm 1.2, 0.9 mm).

Description.

Body 3.6 as long as greatest width, dorsal surfaces matte, dull, moderately setose. Cephalon length 0.6 width, lateral margins converging anteriorly, smooth. Pseudorostrum 0.5 as long as proximal width, anterior margin rounded. Eyes lateral, with ~8 ommatidia, colour orange. Pereonites compact, close to each other, without dorsal carinae; tergite lateral margin subtruncate (those of pereonite 5 rounded), lateral margins smooth; median keels on sternites 5-7 (or on 6 and 7 or 7 only), keels weakly developed. Pleotelson width 1.1 length, dorsal surface with weak and indistinct sub-lateral ridges, caudomedial lobe narrowly rounded; lateral margins weakly convex, each with 5 spines.

Antenna 1 with 5 articles; article 1 1.3 as long as wide, distolateral angle not lobed, weakly serrated, distomesial margin not serrate; article 2 0.5 as long as article 1, 1.2 as long as wide; lateral margins of articles 1 and 2 without cuticular scales; article 3 0.6 as long as article 2; article 4 0.8 as long as article 3; article 5 1.1 as long as article 3, 2.5 as long as proximal width, distally with 2 aesthetascs. Antenna 2 peduncle article 5 4.2 as long as article 3, 1.9 as long as wide, lateral margin convex, with small cuticular scales, mesial margin straight; article 6 1.4 as long as width, distally expanded, distal width 2.3 proximal width, 0.6 as long as article 5, lateral margin without cuticular scales, mesial margin with 4 simple setae, distodorsal surface without setae; flagellum with 5 articles, article 1 1.1 as long as peduncle article 6, 2.6 as long as combined lengths of remaining articles.

Mandible palp article 2 with 2 long biserrate setae (terminally spatulate), article 3 with 5 long pectinate setae. Right incisor with symmetrical cusps, margins convex, distally acute; left incisor similar to right. Molar process distal half finely serrate. Right mandible spine row composed of 9 spines; left spine row divided by truncate lobe, without lacinoid spine. Maxilla 1 lateral lobe with 12 strongly serrate RS; mesial lobe with 2 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, mesial lobe with 3 long simple setae and many long setules. Maxilliped endite 2 as long as greatest width, extending to middle of palp article 4, distal margin evenly rounded, mesially with 2 large serrations, with shallow distomesial concavity, with 4 mesial tubercular RS, distomesial margin with 3 coupling setae. Maxilliped palp article 2 2.3 as long as article 1, mesial lobe extending to distal margin of article 3, distomesial margin with 1 simple seta; article 3 0.5 as long as article 2, distomesial margin with 1 simple seta; article 4 4.6 as long as wide, mesial margin weakly concave, distally with 4 setae; article 5 0.2 as long as 4, with 4 terminal setae.

Pereopod 1 basis 3.6 as long as wide, inferior margin with 1 proximal simple seta; ischium 0.7 as long as basis, 2.6 as long as wide; merus 0.7 length of ischium, 2.0 as long as wide; carpus 1.0 as long as ischium, 2.8 as long as wide; propodus 3.5 as long as wide, superior margin with 2 simple setae, inferior margin with 3 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 basis 2.7 as long as wide; superior margin with 1 short proximal simple seta; ischium 0.8 as long as basis, 3.1 as long as wide, superior margin strongly convex at midpoint, superior margin with 1 simple seta (distal margin with cuticular scale fringe), inferior distal angle with 1 seta; merus 0.6 as long as ischium, 1.9 as long as wide, superodistal angle with 2 simple setae (and short cuticular scale-spines); carpus 0.9 as long as ischium, 3.6 as long as wide, inferior margin with 7 setae, superior distal angle with 1 prominent pappose seta; propodus 1.1 as long as ischium, 3.7 as long as wide, inferior margin with 3 acute RS, superior margin with 6 simple setae; dactylus 0.4 as long as propodus.

Pleopod 1 2.6 as long as greatest width, lateral margin strongly concave, apical lobe broadly rounded, with long marginal setae, lateral margin with slender setae, distolateral lobe acute, not extending to distal margin. Pleopod 2 protopod 2.3 as long as midwidth, lateral margin mid-half strongly convex, without setae, distal margin straight or weakly concave, with long marginal cuticular scales, apex narrowly rounded; stylet in retracted position extending beyond apex. Pleopod 3 endopod 2.2 midwidth; exopod article 1 2.5 as long as wide, not extending to endopod apex, lateral margin fringed with cuticular scale-spines; article 2 0.5 as long as article 1, lateral and mesial margins with spine-like cuticular scale-setae (laterally; mesial with cuticular scale-setae).

Uropod peduncle extending slightly beyond margin of pleotelson, mediodistal corner strongly produced and acute, distolateral margin with 2 simple submarginal setae, mesial margin finely serrate. Exopod 0.7 as wide as endopod, 1.3 as long as wide, with 8 simple setae. Endopod 1.0 as long as wide, 0.3 as long as peduncle proximolateral margin, apex with 8 long simple setae.

Female.Pleopod 2 1.2 as long as proximal width, lateral margins strongly convex, posterior margins straight, apex with 3 sub-apical simple setae.

Size.

Males 1.1-1.6 mm, mean 1.4 mm (n=11); ovigerous females 1.4-1.8 mm, mean 1.5 mm (n=11), non-ovigerous females 1.1-1.7 mm, mean 1.4 mm (n=10); all from type series.

Colour pattern. All somites with dark brown chromatophores, darker and more dense on the anterior part of the head. In fresh specimens there is an anterior marginal band clear of chromatophores that together with the clear pseudorostrum, antenna 1 and antenna 2 gives the impression of a white margin to the front of the head. Some brown chromatophores are present on the female operculum.

Variation.

The number of pleotelson marginal teeth varied from 1 to 5 (n=24) in males with 4 (23%) or 5 (39%) most frequent; 4-6 (n=22) in ovigerous females with 5 (73%) most frequent and 4 and 6 occurring twice each.

Remarks.

Within the Great Barrier Reef and nearby regions Joeropsis adusta sp. n. can be identified by being entirely dark brown with a moderately setose dorsal surface, antennular article 1 without distolateral lobe, antenna 2 article 5 not expanded with weakly convex margins and an anteriorly rounded pseudorostrum.

There are a number of species of coral reef Joeropsis , some as yet undescribed, that are largely or entirely dark brown in colour. Among these are Joeropsis salvati Müller, 1989 from the Society Islands, Joeropsis lentigo Kensley & Schotte, 2002 from the Seychelles and Joeropsis bicornis Kensley, 2003 from the subtropical Easter Island.

Joeropsis adusta sp. n. differs from the closely similar Joeropsis salvati in the uropod having an apical spine (weak or absent in Joeropsis salvati , Fig. 4D), antenna 1 article 1 without distolateral lobe (with lobe), antenna 2 article 5 with straight mesial margin (angled), distally wide uropod (uropod margins sub-parallel) and the pseudorostrum anteriorly rounded (subtruncate to weakly concave, but variable). Müller (1989, fig. 78) illustrated the uropod as lacking a terminal spine, but that is not the case. Re-examinations of the holotype slides shows that the illustrated uropod is damaged, while the other uropod has a small terminal spine (Fig. 4D); a small spine is also present in two of the three paratypes examined (not visible in the third specimen).

Joeropsis bicornis has a distinct head band, the brown chromatophores are more diffuse than in Joeropsis adusta and the uropod lacks a terminal spine (present in Joeropsis adusta ).

Joeropsis adusta sp. n. is closely similar to Joeropsis lentigo , but morphological comparisons are not possible as the species was only briefly diagnosed with a figure of the habitus, and small figures of the male pleopod 1 and uropod, and there were no comparative comments. Joeropsis adusta differs in being dark brown (vs red–brown in Joeropsis lentigo ), having a distally wider somewhat club-shaped uropod, the mesial margin of which is feebly serrate (smooth in Joeropsis lentigo ), fewer marginal spines on the pleotelson (1-5 vs 3-6), more dense chromatophores (though this is probably variable) and a longer clear band on the anterior margin of the head.

Joeropsis adusta sp. n. is the only entirely dark-brown setose species recorded from the Lizard Island region, and fresh material can be identified on that basis. Other largely brown species are either more pale (e.g. Joeropsis panstikta sp. n., described herein), lack the abundant dorsal setae or have distinct clear areas such as a single pereonite (usually pereonite 5) or certain tergite lateral margin, or darker patches. Characters of the head, pleotelson spines, pseudorostrum shape, setosity and details of the appendages should all be compared to other species where possible.

Distribution.

Fringing reef at North Point and Seabird Islet, Lizard Island, South Direction Island and back reef of Yonge Reef (Fig. 1); 1 to 25 metres.

Etymology.

The epithet taken from the Latin adustus, meaning singed or scorched (to brown).