Macrostylis angolensis, Brandt, Angelika, 2004

Brandt, Angelika, 2004, New deep­sea species of Macrostylidae (Asellota: Isopoda: Malacostraca) from the Angola Basin off Namibia, South West Africa, Zootaxa 448, pp. 1-35 : 16-21

Macrostylis angolensis , sp. nov. ( Figs 9–11 )

Holotype: ovig. Ψ (2.2 mm), Angola Basin, South Atlantic, 18°18.3’S 004°41.3’E – 18°19.4’S 004°41.9’E, 22 July 2000, ZMH K­ 40280; EBS, station 340, 5395 m.

Paratypes: ovigerous Ψ (3 mm) (slightly damaged) and Ψ (2.1 mm), ZMH K­ 40281; both EBS, station 340, same data as holotype.

Distribution: Only known from type locality.

Etymology: The epithet is adapted from that of the type locality.

Diagnosis: Very long second antennal article, at least three times as long as preceding article.

Description: Female (holotype) body ( Fig.9 ): 3.5 times as long as wide, and about 4 times as long as body depth; body dorsum and margins smooth, without setae. Head about 3 times as wide as long, almost as wide as first pereonite, without dorsal spines or any sculpture. Pleotelson oval. Proximally broader than distally, caudal tip rounded, slightly acuminating, 0.6 as wide as body and 0.2 as long as body, 0.6 as long as pereonites 5–7 together. Pereonites 5 and 6 longest, pereonites 1 and 2 shortest.

A1 ( Fig. 9 ): less than 0.1 as long as body length, of 5 articles decreasing in length and width. Article 1 longest, with 1 distal broom seta. Article 2 slightly shorter, also with 1 distal broom seta, articles 3 to 5 with 1 aesthetasc each, article 5 also with another 2 simple setae.

A2 ( Fig. 9 ): 0.2 as long as body, with 5 peduncular and 7 flagellar articles. Peduncular article 1 short, almost quadrangular, articles 1 to 3 without setae, article 2 at least 3 times as long as 1 and also longer than 3, peduncular article 4 longest, with 1 simple seta and 2 distal broom setae, article 5 distally with 6 broom setae. Flagellar articles generally decreasing in length and width to distal tip, second flagellar article with 1 simple distal seta, tip with 3 simple setae of different lengths.

La ( Fig. 9 ): Broad oval, twice as broad as long, with distal short setules.

LMd ( Fig. 9 ): Incisor with 6 teeth, lacinia mobilis shorter than incisor (0.6), bearing 3 teeth, spine row of 14 setae, pars molaris stout, tapering distally, with 8 simple setae of various lengths. Mandibular palp absent. RMd ( Fig. 9 ): similar to left, but incisor only with 3 teeth.

Mx1 ( Fig. 9 ): Inner endite 0.4 as wide as outer endite. Outer endite with 11 strong spine­like setae, inner endite with 1 strong simple seta.

Mx2 ( Fig. 9 ): Of 3 endites, outer and medial endites most slender, with 3 long setae, medial endite with at least 9 distal setae.

Mxp ( Fig. 9 ): Endite reaching to 0.8 of palp article 2, with 4 fan and several simple setae distally and 2 medial coupling hooks. Palp length 0.4 of total basis length. First palp article shortest, ring­like, with 1 distomedial simple seta; article 2 broadest and longest, with 1 distodorsal simple seta; article 3 0.9 as wide as article 2, with 4 medial simple setae, article 4 narrow, 0.2 as wide as article 3, with 2 simple distal setae, last article narrowest, as long as first, with 3 simple setae. Epipod 4 times as long as wide, epipod as long as basis, lateral angular projection at 0.25 of length.

P1–P4 ( Figs 10–11 ): P1–P3 about subequal in length, P4 shortest. Bases of all pereopods longest articles, of P1 and 2 with 6 broom setae, of P3 with 1, of P4 with 3, ischia about 0.6–0.7 as long as bases, with varying numbers of sensory setae on both margins, especially distodorsally. Meri slightly shorter than ischia, in P2 of same length, with long sensory setae, on P1 with broom seta distodorsally on merus. Carpi slightly narrower and shorter than meri, except for P 3 in which it is slightly longer on P1 and P2 mainly with setae on ventral side, P2 and P3 with many long sensory setae distodorsally and 1 broom seta, P4 also with 1 broom seta and 1 long sensory seta. Propodi 0.8 (in P1 as long as carpus) shorter than carpi with 1 broom seta distodorsally of P2, and few setae on the other pereopods, P3 without setae. Dactyli with 2 claws and 2–4 setae.

P5 and P6 ( Fig. 10 ) (P7 broken off in this specimen and the other material): Long and slender, basis longest article, with 2 broom setae and 2 simple setae in P5 and 7 broom and 4 simple ones in P6. Ischium of P5 0.8 (1 as long in P6) as long as basis, with 5 sensory setae on ventral margin and 1 to 2 on dorsal side. Meri 0.6–0.7 as long as ischia, with 5 sensory setae, 4 of these distally. Carpus (broken off in P6) only slightly longer than propodus, with 6 sensory setae ventrally (5 distally) and 1 sensory and 1 broom seta distodorsally. Propodus of P5 with 4 sensory setae on ventral side, most proximal and most distal ones being longest, 1 distodorsal broom seta. Dactylus shorter than propodus, with 2 claws of different lengths.

Plp 2 ( Fig. 11 ): Elongated, oval, waisted at proximal half, broadest medially, with 12 proximolateral whip setae, distally with 14 plumose setae.

Plp 3 ( Fig. 11 ): Endopod 3 times as long as wide, almost rectangular, with 3 distal plumose setae, exopod almost as long as endopod, laterally with simple setules.

Plp 4 (not illustrated): Endopod round­oval, bare, twice as long as wide, exopod almost as long as endopod, distally with 1 long plumose seta.

Plp 5 ( Fig. 18 ): Only one small oval lobe.

Urp ( Fig. 11 ): Broken off at tip, total length unknown, proximal part bearing 7 setae of different lengths and 1 broom seta.

Remarks. Macrostylis angolensis sp. nov. is most similar to M. vinogradovae Mezhov, 1992 and M. truncatex Menzies, 1962 . The new species bears a very long second antennal article, by which it can be distinguished from the latter. The second article of the antenna is more than three times as long as the first and third articles, in M. truncatex it is less than twice as long as the first, and the female operculum is more slender and narrow distally than in the new species. M. vinogradovae also bears a prolonged second article on the antenna, but this is only twice as long as the first.

Figures

FIGURE 9. Macrostylis angolensis sp. nov., holotype Ψ (2.2 mm), dorsal view, antennule, antenna, labrum, left and right mandibles, maxillule, maxilla, maxilliped, basis of pereopod 7.

FIGURE 10. Macrostylis angolensis sp. nov., holotype Ψ (2.2 mm), pereopods 1, 2, 5, 6.

FIGURE 11. Macrostylis angolensis sp. nov., holotype Ψ (2.2 mm), pereopods 3 – 4, pleopods 2, 3, 5, proximal part of uropod.

FIGURE 18. Macrostylis longispinis sp. nov. holotype ɗ (2.5 mm), pereopod 7, pleopods 1 – 3. proximal part of uropod sympod.