Macrostylis longispinis, 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 : 29-33

Macrostylis longispinis sp. nov. ( Figs 16–18 )

Holotype: ɗ (2.5 mm), Angola Basin, South Atlantic, 17°06.2’S 004°41.7’E – 17°07.5’S 004°42.3’E, 25 July 2000, ZMH K­ 40286; EBS, station 344, 5415 m.

Distribution: Only known from type locality.

Etymology: The epithet alludes to the long, caudally directed ventral spine on the male pereonite 7.

Diagnosis: Pereonite 7 with long ventral caudally directed spine. Long and broad antennule, broader than antenna. Maxillipedal endite narrow, less than 0.4 as broad as palp. Males with long stylet on the pleopod 2, about 2.0 as long as sympod.

Description: Male (holotype) body ( Fig. 17 ): 4 times as long as wide; body dorsum and margins smooth, without setae. Head about 1.5 as broad as long, without dorsal spines or any sculpture. Pleotelson 1.4 as long as wide, 0.2 as long as total body, of quadrangular shape, but caudolaterally acuminating, creating concave notches, mediocaudally almost straight. Pereonite 6 longest, pereonites 1–2 shortest, pereonite 3 longest anterior pereonite. Pereonite 7 with strong ventral caudally directed spine. Uropods broken off in this specimen.

A1 ( Fig. 16 ): About 0.2 as long as body, of 5 articles. Article 1 about as long as 3, without setae. Article 2 1.5 as long as one and following ones, almost rectangular, with 2 distal broom setae and 1 simple seta. Third article longer than fourth, without setae, fourth one bare as well, last one shortest and narrowest, with 2 short and slender aesthetascs.

A2 ( Fig. 16 ): 0.4 as long as total body length, with 5 peduncular and 7 flagellar articles. Peduncular articles 1–3 short, articles 4 and 5 long, 4 longest, with 5 simple setae, fifth article with 2 simple and 3 distal broom setae of different lengths. Flagellar articles generally decreasing in length to distal tip, with 1 or none seta, last article with 2 simple setae, 1 being very long.

LMd ( Fig. 16 ): Incisor with 4 teeth, lacinia mobilis 0.4 as short as incisor, bearing 4 teeth, spine row of 8 setae, pars molaris stout, tapering distally, with 6 simple setae of various lengths. Mandibular palp absent. RMd ( Fig. 16 ): Similar to left, but incisor and lacinia mobilis only with 3 teeth, spine row with 6 members.

Mx1 ( Fig. 16 ): Inner endite 0.8 as wide as outer endite. Outer endite with 11 strong spine­like setae, inner endite with 1 strong simple seta (broken off) and few setules.

Mx2 ( Fig. 16 ): 3 endites, outer and medial endites most slender, with 4 long setae, medial endite with at least 8 distal setae.

Mxp ( Fig. 16 ): Endite exceeding second palpal article in lenght, with 2 fan and several simple setae distally, 2 medial coupling hooks. Palp 0.3 as long as basis. First palp article quadrangular, ring­like, with 1 distomedial simple seta; article 2 broadest and longest, with 3 distodorsal simple setae and 2 distomedial ones; article 3 0.5 article 2 length, with 4 medial and 2 lateral simple setae, articles 4 and 5 narrow. Epipod 4 times as long as wide, epipod about as long as basis, lateral angular projection proximally at 0.6 of length.

P1–P4 ( Fig. 17 ): P1 shorter than P2 and P3 ( Fig. 17 ), P2 and P3 about subequal in lengths (Fig. 31), P4 shortest ( Fig. 17 ). Bases of all pereopods longest articles, of P1 with 2 simple setae, P2 with 3 broom and P3 with 1 broom setae on basis, P4 without. Ischia about 0.5–0.8 basis length, P1 with 4 setae of different lengths, P2 without setae, P3 with 3 long distal sensory setae, P4 with 2 small sensory and 3 long distodorsal sensory setae of varying lengths. Meri slightly shorter than ischia, with 3 to 5 long distodorsal sensory setae, ventrally 1–2 short sensory setae. Carpi slightly longer than meri, with 1–4 sensory setae of different lengths distodorsally and 2–4 smaller and more slender setae distoventrally, some serrated. Propodi 0.5–2 as long as carpi, with few ventral and dorsal setae and 1 broom seta each. Dactyli with 2 claws.

P5–P7 ( Figs 17–18 ): Long and slender, basis longest article, with 4 broom setae and 4 simple setae in P5, in P6 only with 1 broom seta and 5 simple ones, P7 with 11 whip setae and 5 ventral simple setae. Ischium of P5–P7 0.8–0.9 as long as basis, with several simple setae of varying lengths on both sides. Meri 0.6–0.8 as long as ischia, with varying numbers and varying lengths of sensory setae, most distally. Carpus 1.2–1.4 as long as merus, in P6 about as long as basis, with several sensory setae on both sides. Propodus slightly shorter than carpus, of P6 and P7 with 1 distodorsal broom seta and additionally with some sensory setae in all pereopods. Dactylus much shorter than propodus, with 2 long claws of different lengths.

Plp 1 ( Fig.18 ): Long and slender, distally acuminating. Proximal part damaged. Distal tips with 5 plus 1 simple setae.

Plp 2 (ig. 18): Almost straight, with long and slender sympod, bearing 8 lateral whip setae in proximal half and 4 long plumose setae around distal tip. Stylet 1.3 sympod length, exopod small, bare, oval.

Plp 3 ( Fig. 18 ): Endopod much longer than wide, with 3 distal plumose setae, exopod slightly shorter than endopod, laterally with simple setules.

Remarks. Macrostylis longispinis sp. nov. can easily be discriminated from the other species of Macrostylis by the long ventral caudally directed spine of pereonite 7 and the long and very broad antennule. The maxillipedal endite of this species is extremely narrow, the males have a long stylet on the second pleopod, which exceeds the sympod almost twice its length, a character which has not been described for other species of Macrostylidae .

Figures

FIGURE 16. Macrostylis longispinis sp, nov. holotype ɗ (2.5 mm), dorsal and lateral views, antennule, antenna, left and right mandibles, maxillule, maxilla, maxilliped.

FIGURE 17. Macrostylis longispinis sp. nov. holotype ɗ (2.5 mm), pereopods 1 – 6.

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