Joeropsis specca, 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 : 35-37

Taxon classification Animalia Isopoda Joeropsididae

Joeropsis specca sp. n. Figs 20, 21, 22

Material.

Holotype. ♂ (2.2 mm), Martin Reef, 14.75600°S, 145.36271°E, 30 August 2010, reef flat, dead corals, 5 m, LI10-35, coll. J. Reimer (MTQ W33804).

Paratypes. 5 ♂ (2.8, 2.6 [broken; dissected], 2.0, 1.9, 1.8 mm), 7 ♀ (ovig 2.7, 2.0 mm, non-ovig. 2.7, 2.5[dissected], 2.4, 1.9, 1.8 mm), same data as holotype (MTQ W32664).

Description.

Body 4.0 as long as greatest width, dorsal surfaces finely granular, with few setae. Cephalon length 0.6 width, lateral margins weakly sinuate, smooth. Pseudorostrum 0.7 as long as proximal width, anterior margin narrowly truncate, apex narrowly excavate. Eyes lateral, with 12-14 ommatidia, colour dark brown. Pereonites compact, close to each other, without dorsal carinae (with low tubercle, visible only with relief lighting); tergite lateral margin rounded, lateral margins smooth; median keels not observed. Pleotelson width 1.0 length, dorsal surface with weak and indistinct sub-lateral ridges, caudomedial lobe sub-acute; lateral margins convex, each with 6-7 spines.

Antenna 1 with 5 articles (may be a 6th fused terminal article); article 1 1.3 as long as wide, distolateral angle weakly lobed, with serrations, distomesial margin not serrate; article 2 0.7 as long as article 1, 1.5 as long as wide; lateral margins of articles 1 and 2 with weak cuticular scales on distal margin of article 2; article 3 0.4 as long as article 2; article 4 0.7 as long as article 3; article 5 1.3 as long as article 3, 1.7 as long as proximal width, distally with 3 aesthetascs. Antenna 2 peduncle article 5 1.6 as long as articles 1-4 combined, 1.8 as long as wide, lateral margin weakly convex, with prominent cuticular scales, mesial margin straight; article 6 1.8 as long as width, distally not expanded, distal width 1.3 proximal width, 0.8 as long as article 5, lateral margin without cuticular scales, mesial margin with 4 simple setae, distodorsal surface with few simple setae; flagellum with 8 articles, article 1 1.2 as long as peduncle article 6, 1.9 as long as combined lengths of remaining articles.

Mandible palp article 2 with 3 long biserrate setae (terminally spatulate), article 3 with 8 long pectinate setae. Right incisor with symmetrical cusps, margins convex, distally acute; left mandible incisor similar to right incisor. Molar process distal third finely serrate. Right mandible spine row composed of 9 spines; left mandible spine row composed of 10 spines, divided by truncate lobe, without lacinoid spine. Maxilla 1 lateral lobe with 11 strongly serrate RS, and 2 simple RS; mesial lobe with 3 long, simple RS. Maxilla 2 lateral lobe with 4 long, curved, finely serrate setae; middle lobe with 4 long serrate setae, mesial lobe with 4 long simple setae and many long setules. Maxilliped endite 2.1 as long as greatest width, extending to distal margin of palp article 4, distal margin evenly rounded, with 4 prominent serrations, with shallow distomesial concavity, with 4 mesial tubercular RS, distomesial margin with 3-4 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 2 simple setae (and mesial row of dense cuticular scale-setae); article 4 3.4 as long as wide, mesial margin weakly concave, distally with 4 setae; article 5 0.2 as long as 4, with 8 terminal setae. Epipod 2.7 as long as basal width, distally acute; 0.9 as long as palp, 0.5 as long as endite.

Pereopod 1 basis 3.2 as long as wide, superior margin with 4 simple setae, inferior margin with 2 simple setae; ischium 0.7 as long as basis, 3.1 as long as wide, superior margin with 3 simple setae, inferior margin with 1 simple seta; merus 0.6 length of ischium, 1.9 as long as wide, superior margin with 1 simple setae, inferior margin with 1 simple seta; carpus 0.8 as long as ischium, 3.9 as long as wide, superior margin with 2 simple setae, inferior margin with 2 simple seta; propodus 3.7 as long as wide, superior margin 2 simple setae (and prominent penicillate seta at distal angle); inferior margin with 3 acute RS, dactylus 0.4 as long as propodus, with 2 claws. Pereopods 2-7 sub-similar, more slender than pereopod 1, each with 3 claws (mesial claw slender). Pereopod 7 basis 314 as long as wide; superior margin with 4 short simple setae, inferior margin without setae; ischium 0.8 as long as basis, 3.3 as long as wide, superior margin convex, with 3 simple setae, inferior distal angle with 1 seta; merus 0.4 as long as ischium, 2.1 as long as wide, superodistal angle with 1 simple seta, inferior margin with 1 simple seta; carpus 0.8 as long as ischium, 4.9 as long as wide, inferior margin with 3 setae, superior distal angle without prominent pappose setae; propodus 0.8 as long as ischium, 5.2 as long as wide, inferior margin with 3 acute RS, superior margin with 4 simple setae and 1 distal pappose seta; dactylus 0.5 as long as propodus.

Pleopod 1 2.5 as long as greatest width, lateral margin weakly 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 2.5 as long as midwidth, lateral margin mid-half weakly convex, with setae (short setae and cuticular scales), distal margin weakly concave, with long marginal cuticular scales, apex narrowly rounded; stylet in retracted position extending beyond apex. Pleopod 3 endopod 2.7 midwidth; exopod article 1 3.1 as long as wide, extending to endopod apex, lateral margin fringed with cuticular scale-spines; article 2 0.4 as long as article 1, lateral and mesial margins with spine-like cuticular scale-setae (lateral only, mesial with 6 fine setae).

Uropod peduncle extending slightly beyond margin of pleotelson, mediodistal corner strongly produced and acute, apex with 4 simple setae, distolateral margin with 2 simple submarginal setae, mesial margin smooth. Exopod 0.6 as wide as endopod, 1.0 as long as wide, with 8 simple setae. Endopod 1.3 as long as wide, 0.3 as long as peduncle proximolateral margin, apex with 10 long simple setae (and 3 penicillate setae).

Female.Pleopod 2 1.3 as long as proximal width, lateral margins weakly convex, posterior margins weakly concave, apex with 2 sub-apical simple setae.

Colour pattern.

Head with relatively short diffuse, low-density, irregular transverse dark-brown band across the mid 30-48% of the head; dorsal surfaces otherwise with few and faint chromatophores on pereonites 1-4 and 6, 7 and pleotelson; pleonite 5 clear, head and pereonite 4 consistently darkest, pereonites 1 and 2 with chromatophores but variable and pereonites 6 and 7 consistently paler than anterior pereonites.

Size.

Males 1.8-2.8 mm (average 2.7 mm, n=6); ovigerous females 2.0 and 2.7 mm and non-ovigerous females 1.8-2.7 mm (average 2.3 mm, n=5).

Variation.

Male pleotelson margin (n=7) with 6 (21%) or 7 (64%) teeth, the largest male with 2 mid-marginal teeth only; females with 7 (100%, n=7) teeth on each margin. Colour varies from near black to pale brown.

Remarks.

Joeropsis specca sp. n. may be identified by the colour pattern, in conjunction with a pseudorostrum with straight lateral margins that converge mesially to a narrowly excavate apex, relatively large eyes, pleotelson margins each with 5 or 6 spines and the rounded tergite lateral margin.

There are many shallow-water species of Joeropsis that present an irregular pattern of chromatophores over most of the dorsum. In several such species pereonite 5 is without chromatophores: these species include, for example, Joeropsis dimorpha Kensley & Schotte, 2002 (Seychelles), Joeropsis faurei Müller, 1991a ( Réunion Island), Joeropsis gertrudae Müller, 1989 ( Mooréa), Joeropsis trilabes Kensley, 2003 (Easter Island) and Joeropsis bicornis Kensley, 2003 (Easter Island). The intensity (how dark) and density of the patterning does vary, and the arrangement of the chromatophores may not allow for species separation on its own. Critical characters to reference in separating these species are morphological (see 'Species recognition’, p. MS 9), in particular the shape of the pseudorostrum, details of the maxilliped, antennula and antenna, and the serration of the lateral margins of both the head and pleotelson.

Distribution.

Known only from the type locality, Martin Reef (midway between Lizard Island and the mainland, Fig. 1); at a depth of 5 metres.

Etymology.

The epithet is the Anglo-Saxon specca meaning speckled.