Leipanthura casuarina, Poore, 2009

Poore, Gary, 2009, Leipanthura casuarina, new genus and species of anthurid isopod from Australian coral reefs without a " five-petalled " tail (Isopoda, Cymothoida, Anthuroidea), ZooKeys 18 (18), pp. 171-180 : 174-178

Leipanthura casuarina sp. n.

urn:lsid:zoobank.org:act:467A32DD-1206-4516-A8C6-03E22BC51EE7

Figs 1–4

Material examined. Holotype. Australia, Queensland, Great Barrier Reef, Lizard I., Casuarina Beach , 14.6839°S, 145.4453°E, N.L. Bruce, 15 April 2008 (CReefs stn CGLI31 B), dead coral heads, QM W13791 (ovigerous female, 2.5 mm).

Paratype. Collected with holotype, QM W31120 (juvenile, 2.6 mm, plus 1 microslide).

Non-type. Australia, Western Australia, Ningaloo Reef, off Frazer I., 22.65830°S, 113.61809°E, L. Hughes and C. Bagnato, 25 May 2009 (CReefs stn NR 09-60B), reef slope, coral heads, 6.8 m, WAM C40642 (juvenile, 2.7 mm).

Etymology. Casuarina, from the type locality and continuing the convention initiated by Poore and Lew Ton (1985) of naming Australian anthuroids after Australian plant genera (noun in apposition).

Description of holotype. Total length, 2.5 mm. Body with well-spaced patches of brown pigment all over (see fig. 4 ); 14 times as long as wide. Head longer than wide, smooth, with short, broad rostral projection; eyes lateral, of about a dozen ommatidia. Pereonites smooth, of equal width, pereonites 2–5 of similar lengths, pereonite 6, 0.8 length of pereonite 5, pereonite 7, 0.4 length of pereonite 6. Fused pleonites 1–5 smooth, pleonite 1 indicated ventrolaterally as a slight notch on deep pleural flange, others with minute lateral seta, pleonite 5 posterolaterally lobed around base of pleotelson and uropods; pleotelson half as long as pleonites 1–5, as long as width at base, evenly convex dorsally, tapering to broadly semicircular apex with pair of distal setae, with pair of large statocysts clearly visible.

Antenna 1 peduncle with stout article 1, shorter and progressively narrower articles 2 and 3; flagellum about as long as last peduncle article, of short article 1, longer article 2 and article 3 with 3 aesthetascs and 3 setae. Antenna 2 peduncle longer than peduncle of antenna 1, articles 4 and 5 longer than wide; flagellum of 6 minute articles.

Upper lip domed anteriorly. Mandible with incisor barely toothed, lamina dentata with 3 teeth (molar process not seen); palp of 3 articles, article 2 longer than 1, article 3 half as long as 2, with 3 short distal setae. Maxilla 1 outer lobe with 2 or 3 subdistal teeth (inner lobe not seen). Maxillipedal of fused articles with 1 mesial seta, 1 lateral seta, 2 subterminal facial setae, and 5 setae on lateral apical lobe (fused article 5); epipod rounded.

Pereopod 1 subchelate, with stout proximal articles bearing few setae; carpus cupping propodus, with short square free distal margin, with 2 setae on lower margin; propodus slightly swollen but proximally not overlapping carpus on upper margin, palm axial, concave, with 2 distal setae, another longer seta more distally and laterally; dactylus closing on palm, unguis about one-third its length. Pereopod 2 more slender than first, 1.3 times as long (measured through main axes of articles), proximal articles bearing few setae; merus overlapping carpus and base of propodus on upper margin; carpus triangular, with 2 setae on lower margin; propodus slightly tapering and curved, about 2.5 times as long as wide, palm concave, with palmar comb setae and 1 distal flagellated robust seta; dactylus slightly curved, unguis microscopically dentate. Pereopod 3 similar to pereopod 2, dactylus straighter. Pere- opods 4–6 similar in form and length to each other, about as long as pereopods 2 and 3, proximal articles with few setae; merus with convex upper margin; carpus with free upper margin about 0.7 length of lower margin, with setae on distal angles; propodus curved, about 2.5 times as long as width, palm with 1 flagellated robust seta distally; dactylus curved, unguis one-quarter length.

Pleopod 1 scarcely thickened, not indurate, exopod overlapping endopod and all other pleopods and base of uropods; endopod one-third as wide and half as long as exopod, with 3 distal seta; exopod 2.1 times as long as wide, with 6 distal marginal seta. Pleopods 2–5 progressively shorter, between 0.58 (pl2) and 0.44 (pl5) as long as pleopod 1; pleopods 2–4 with tapering endopods (2, 2, 1 apical setae) and more rectangular exopods (4, 4, 4 apical setae); pleopod 5 endopod oval, broad (without apical setae) and shorter oval exopod (3 apical setae).

Uropodal peduncle widest distally, mesially expanded, with oblique distal margin; endopod suboval in dorsal view, wider than deep, with 3 apical setae mesially and 3 setae ventrolaterally; exopod cylindrical, about half as long as endopod, with 1 lateral seta and 2 dorsal apical setae.

Oostegites on pereopods 2–5.

Remarks. Th e illustration of the female (fig. 1a) shows pleopod 1 in its operculate position; that of the juvenile (fig. 1b) with the pleopods open. Apart from the absence of oostegites, the juvenile paratype seems indistinguishable from the female.

The specimen from Ningaloo Reef, WA, on the opposite side of Australia from the type locality, was not dissected ( fig. 4 ) but differed in ways that could be interpreted as being of taxonomic value only after looking at more than the three specimens available now. General proportions and shapes were similar. Nevertheless, the distal palmar setae on pereopods 2−6 were noticeably trifid (flagellated and simple in type specimens) and the numbers of setae differed. The WA specimen possessed four setae on the mandibular palp article 3 (not three), three apical setae on the uropodal endopod (not two), and three setae ventrolaterally on the uropodal exopod (not two).

The species, at 2.7 mm long, is one of the smallest anthuroids known, considerably narrower than some expanathurids of similar lengths ( Poore and Lew Ton 2002).

Figures

Figure 1. Leipanthura casuarina sp. n. a holotype female (right lateral view, pereopods not shown, oostegites indicated, pleopod 1 in operculate position) b paratype juvenile (right lateral view, pereopods shown, pleopods exposed) c head and right antennae 1 and 2, holotype female (dorsal view); e pleon and pleotelson, holotype female (dorsal view, uropods in situ) u left uropod, paratype juvenile (ventral view); left mouthparts, holotype female, in situ (md mandible mx maxilla 1 mp maxilliped). Scale bar = 0.5 mm, refers to a and b only.

Figure 2. Leipanthura casuarina sp. n., paratype juvenile. p1-p6, pereopods 1–6 (drawn in situ to same scale). Scale bar = 0.1 mm.

Figure 3. Leipanthura casuarina sp. n., paratype juvenile. pl1-pl5, pleopods 1–5 (drawn to same scale). Scale bar = 0.1 mm.

Figure 4. Leipanthura casuarina sp. n., alcohol-preserved non-type specimen, WAM C40642. Photograph and image preparation by Ken Walker, Museum Victoria, 18 June 2009. Scale bar = 0.25 mm.