Neohyssura gladia, Kensley & Schotte, 2000

Kensley, B. & Schotte, M., 2000, New species and records of anthuridean isopod crustaceans from the Indian Ocean, Journal of Natural History 34, pp. 2057-2121 : 2095-2099

Neohyssura gladia sp. nov.

(Figures 27, 28)

Type material. HOLOTYPE: USNM 253134 , non-ovigerous m 2.0 mm, sta

K-AL-54, coarse sand and rubble, outer reef slope oOE Picard Is., Aldabra, 25 m,

FIG. 27. Neohyssura gladia sp. nov.: (A) lpleotelson and uropod; (B) lmandible; (C) l pleopod 1; (D) lpleopod 2; (E) lpereopod 1; (F) lpereopod 2; (G) lpereopod 3; (H) lpereopod 7; (I) lantennule.

15 April 1983. PARATYPES: USNM 253135 , two l 2.5 mm, sta K-AL-54, same data as holotype. USNM 253136 , one l 2.2 mm, four non-ovigerous m 2.0±3.0 mm, sta K-AL-38, K-AL-39, coral rubble, outer reef slope oOE Picard Is., Aldabra , 11 April 1983. USNM 253137 , two non-ovigerous m 2.2±3.0 mm, sta JR-29, JR-33A, Nosy Be , Madagascar, 1±1.5 m , February 1964.

Diagnosis. Non-ovigerous female: Body elongate±slender. Integument nonindurate. Cephalon with tiny weakly pigmented eyes; low rounded rostrum not extending anteriorly beyond anterolateral lobes. Pleonites 1±5 free, as broad as wide, laterally with numerous elongate plumose setae; pleonite 6 with posterodorsa l margin convex. Telson basally broad, tapering to narrowly rounded apex bearing numerous setae of varying lengths. Antennular peduncle with two basal articles broad, article 3 two-thirds width of 2; ¯agellum of three articles, middle article longest, short terminal article bearing single conspicuous aesthetasc. Antennal ¯agellum of seven articles, together barely longer than ®fth peduncular article. Mandibular palp of three articles, middle article longest, bearing two distal setae; terminal article almost one-third length of second, with single short terminal seta; incisor of three cusps; lamina dentata having ®ve marginal serrations; molar strong, spiculiform. Maxilla having six distal spines, terminal spine strongest. Maxilliped having ®ve-articulate palp; basal palp article short, having free lateral, but no free mesial margin; terminal article tiny, bearing four setae; strong endite reaching to third palp article, with single terminal seta. Pereopod 1 subchelate, carpus narrowly triangular, distally acute, extending well beyond proximal palm of propodus; latter somewhat expanded, palm bearing three setae plus transparent ¯ange divided into rounded sections between setae; unguis slightly more than half length of remainder of dactylus, with short seta at base. Pereopod 2 subchelate, carpus narrowly triangular, distally extending well beyond propodal palm; propodus more expanded than in pereopod 1, palm bearing two short sensory setae, with lobed transparent ¯ange between; unguis half length of remainder of dactylus. Pereopod 3 subchelate, carpus narrowly triangular, distally acute, extending well beyond propodal palm; latter bearing two sensory setae, plus lobed and marginally serrate transparent ¯ange; unguis about one-third length of remainder of dactylus. Posterior pereopods with carpi short, anterior margin shorter than posterior margin, serrate sensory seta at posterodistal angle; propodus with two serrate sensory setae on posterior margin; unguis just less than one-third length of remainder of slender dactylus. Pleopods 1±5 similar; pleopod 1 non-operculate, rami subequal in length and width, exopod with ten marginal plumose setae, endopod with eight distal marginal plumose setae. Uropodal exopod wider than, but subequal in length to endopod, elongate ±oval, with seven elongate setae distally; endopod elongate, narrowly rounded distally, with several elongate setae of varying lengths.

Male: Body proportions: Cephalon with large well pigmented eyes extending towards midline dorsally and constricting mouthparts ventrally. Pereopod and pleon essentially as in female. Telson less spiciform than in female, proximally slightly broader. Antennular ¯agellum of nine articles, all except ®rst and eighth bearing aesthetascs; short terminal article bearing single aesthetasc. Mandibular palp of three articles, middle article twice length of ®rst, four times length of third, with two short distal setae, terminal article with single seta; body of mandible modi®ed to form slender sclerotized sword-like structure reaching anteriorly beyond ramus. Maxilla and maxilliped reduced, both represented by low rounded exopods only. Pereopod 1 subchelate, carpus triangular, distally acute, reaching for short distance beyond proximal propodal palm; propodus with ®ve elongate setae on palm, mesial (inner) surface with three setae some distance from margin; unguis half length of remainder of dactylus. Pereopod 2 subchelate, carpus narrowly triangular, distally acute±spinose, extending well beyond propodal palm; propodus more expanded than in pereopod 1, palm bearing three sensory setae separated by rounded lobes of transparent ¯ange; unguis half length of remainder of dactylus. Pereopod 3 subchelate, carpus narrowly triangular, distally acute±spinose, extending well beyond propodal palm; propodus narrower than in pereopod 2, palm bearing three sensory setae separated by transparent ¯ange divided into distally acute lobes; unguis slightly less than half length of remainder of dactylus. Posterior pereopods as in female. Pleopod 2, exopod biarticulate, with transverse suture at about midlength, bearing ten marginal plumose setae; endopod slightly shorter and narrower than exopod, with ®ve distal plumose setae, copulatory stylet articulating on proximal half of mesial margin, extending well beyond ramus, distally rounded and ¯exed. Uropodal exopod narrower and slightly shorter than endopod, with eight distal setae; endopod with about 12 distal setae of varying lengths.

Remarks. Five species of Neohyssura have been described: N. irpex ( Menzies and Frankenberg, 1966) , from the north-western Atlantic, N. spinicauda ( Walker, 1901) from the Mediterranean, N. skolops Kensley, 1978a (from South Africa, the only other Indian Ocean species), N. atlantica WaÈgele, 1987 , from oOE the Cape Verde Islands and N. bilara Poore and Lew Ton, 1988c from Queensland, Australia. Poore and Lew Ton (1988c) characterized Neohyssura by two apomorphies, a tapering telson and marginal spines on the telson and uropodal exopod. The present species lacks one of these apomorphies in that the uropodal and telsonic margins do not have spines. Apart from this feature, and the structure of the male mandible, N. gladia agrees closely with the earlier species. The body of the mandible in the male of the present species shows a remarkable feature not noted for any other anthuridean, namely the modi®cation into a sword-shaped sclerotized structure. WaÈgele (1981a) in his redescription of N. spinicauda , described a male and mentioned that the mouthparts, except for the mandibular palp, are reduced; his ®gure of the male mandible merely shows a loss of de®nition of the normal mandibular structures, not a major reorganization as is seen in the present species. The stiletto-like structure of the maxilla and distal mandible in paranthurids comes to mind when this remarkable mandibular structure is viewed; its function, however, is uncertain and is perhaps more involved with reproduction than with feeding.

Etymology. The speci®c name is from the Latin `gladius ’, a sword and refers to the structure of the mandible in the male.