Hyssura reptans, Annisaqois & Wägele, 2021

Annisaqois, Manikmayang & Wägele, J. Wolfgang, 2021, Morphology and Taxonomy of Isopoda Anthuroidea (Crustacea) from Sulawesi with description of six new species, European Journal of Taxonomy 768, pp. 1-52 : 3-10

Hyssura reptans sp. nov.

urn:lsid:zoobank.org:act:D0451121-5E07-4F60-BADC-85D3D8BA38E9

Figs 2–5

Differential diagnosis

Blind species of Hyssura (eyes also lacking in male), pereopod 1 propodus palm concave in male, a comb of 6 setae on mesial surface in addition to two stronger medial setae and distally 4 setae, pleopod rami rectangular, pleopod 1 exopod not larger than endopod; exopods of pleopods 1 and 2 distally with more, 10 resp. 9 swimming setae, endopods with 5, uropod exopod narrow lanceolate, outer lateral margin smooth, medial margin slightly serrated, apex with several long simple setae, endopod of uropod as wide as sympod but about 2.5 times longer, a bit shorter than exopod, proximal two thirds of margins nearly parallel, distal margins with simple setae of varying length. Telson tongue-like, lateral margins serrated, not parallel; apex rounded and with 5 pairs of simple setae.

Hyssura ligurica Wägele, 1981 (see Wägele 1981a) is most similar, with a tail fan that resembles that of H. reptans sp. nov. Hyssura ligurica also has rectangular pleopod rami, but in comparison with H. reptans longer meri and carpi in P4–7 and only one sensory spine on the propodi. The female has strong propodi of P1 and P2; unfortunately, the females of H. reptans still remain to be discovered.

Etymology

The species epithet is derived from repto (to crawl).

Material examined

Holotype and type locality INDONESIA • ♂ (2.1 mm); Bangka Island, off Areng Kambing; 1°46′27.53″ N, 125°11′19.53″ E; 5 m depth; in coral rubble; M. Annisaqois and J.W. Wägele leg.; Sep. 2019; MZB Iso 099.

Description of type specimen

BODY. Without chromatophores, 15–16 times as long as wide (rostrum to tip of telson). Head 1.7 times as long as wide, with a lateral constriction at half of its length. Eyes lacking. A small rostral projection between antennae. Pereonites dorsally smooth, as long as wide, length ratio of pereonites: 1<2>3<4> 5> 6> 7, pereonite 3 being about as long as pereonite 7. Pleonites 1–5 free, as wide as pereonites, total length of pleonites 1–5 exceeds length of pereonites 6 + 7. Telson about as long as uropods and shorter than three pleonites.

ANTENNAE. Antenna 1 peduncle of three articles, first 1.5 times as long as wide, articles 2 and 3 progressively shorter; flagellum with typical male modifications: nearly twice as long as peduncle and composed of 9 articles; distal articles narrower, last article tiny; all flagellum articles except the first with long and thin aesthetascs, arranged in a single transverse row per article, number of aesthetascs distally decreasing, last article with only one aesthetasc. Antenna 2 peduncle with 5 articles, second article longest and widest; flagellum of 8 articles, not as long as peduncle articles 4 + 5, with several simple setae, longest on distal article.

MOUTHPARTS. Were lost during dissection; however, in situ a maxilliped palp with five articles was visible, not covering mouthparts but erected nearly perpendicularly, and a mandible with an atrophied endite. Presumably the mouthparts of males are not functional.

PEREOPODS. Pereopod 1 weakly subchelate, propodus palm concave, a comb of 6 setae on mesial surface in addition to two stronger medial setae and distally 4 setae; carpus triangular with short, not prominent ventrodistal projection bearing a simple seta; more proximally another seta; merus dorsal portion nearly triangular. Pereopod 2 propodus less curved than in P1, elongated, about three times as long as wide, palm distally with 3 sensory spines and basally slightly concave; carpus ventrodistally only little projecting, as in pereopod 1. Pereopod 3 similar to pereopod 2. Pereopods 4–7 similar. Propodi distally with two short sensory spines on distoventral margin, with a tooth-like projection in between, carpus trapezoidal, with shorter dorsal margin, merus subtriangular and as long as carpus.

PLEOPODS. All of similar shape, rami nearly rectangular. Pleopod 1 exopod not larger than endopod; exopods of pleopods 1 and 2 distally with 10 resp. 9 swimming setae, endopods with 5. Exopod of Plp 2 composed of two articles. Appendix masculina on Plp 2 in form of a cylindrical rod about 30% as long as endopod, distally rounded, without further conspicuous features.

UROPOD. Exopod narrow lanceolate, length about 7.6 times greatest width, outer lateral margin smooth, medial margin slightly serrated with some single setae in notches; apex with several long simple setae. Endopod as wide as sympod but about 2.5 times longer, a bit shorter than exopod, proximal two thirds of margins nearly parallel, distal margins with simple setae of varying length. Telson tongue-like, lateral margins serrated, not parallel; apex rounded and with 5 pairs of simple seate.

Remarks

We place this species in the genus Hyssura Norman & Stebbing, 1884 because autapomorphies of other genera are missing. Species of Hyssura are blind, the P1–3 carpus is barely projecting ventrodistally. A reduction of male mouthparts has been reported for H. vimsae ( Kensley, 1978 a) (see Wägele 1981a), other males have not been described. The male of H. vimsae also has a comb of setae on P1 propodus; similar combs have also been described for some species of Kupellonura ( K. biriwa , K. marrongie , see Poore & Lew Ton 1988). It is remarkable that also the male is blind, while in other Hyssuridae at least males have prominent eyes. In the present species the carpus of P4–7 is shorter than in previously described species. Other characters are plesiomorphic and occur also in other Hyssuridae .

This is the first Hyssura described from the Indo-Pacific. The other species occur in the Atlantic Ocean or in the Mediterranean and often in bathyal waters

Figures

Fig. 2. Hyssura reptans sp. nov., ♂, holotype in dorsal and lateral view (2.1 mm) (MZB Iso 099).

Fig. 3. Hyssura reptan sp. nov., ♂, holotype (MZB Iso 099). Abbreviations: A1 = antenna 1; A2 = antenna 2; P1–P3 = pereopods 1–3.

Fig. 4. Hyssura reptans sp. nov., ♂, holotype (MZB Iso 099). Abbreviations: P4–P7 = pereopods 4–7; Plp1–2 = pleopods 1–2.

Fig. 5. Hyssura reptans sp. nov., ♂, holotype. Abbreviations: Urp = uropod; Tel = telson.