Macrostylis longipedis, 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 : 10-16

Macrostylis longipedis sp. nov ( Figs 6–8 )

Holotype: ɗ (2.5 mm), Angola Basin, South Atlantic, 16°14.3’S 005°26.8’E – 6°14.9’S 005°26.7’E, 2 July 2000, ZMH 40278; EBS, station 350, 5389 m.

Paratype: ɗ (2.2 mm), 18°18.3’S 004°41.3’E – 18°19.4’S 004°41.9’E, 22 July 2000, ZMH 40279; EBS, station 340, 5395 m.

Distribution: Only known from the Angola Basin, 5389–5395 m.

Etymology: From the Latin words longus (long) combined with pedis (foot); alluding to the extraordinary length of pereopod seven.

Diagnosis: Fourth pereopods shorter than others. Pereopod 7 about twice as long as body. Uropods elongate, very slender, about as long as total body length.

Description: Male (holotype) body ( Fig. 6 ) 6 times as long as wide, and about 6 times as long as body depth; body dorsum and margins smooth, without setae. Head about twice as wide as long, almost as wide as first pereonite, without dorsal spines or any sculpture. Pleotelson rectangular, 0.6 as wide as body and 0.2 as long as total body length, 0.3 as long as pereonites 5–7 together. Pereonite 6 longest, 3 and 7 almost as long as 6, pereonites 1 and 2 shortest.

A1 ( Fig. 6 ): 0.2 as long as total body length, of 7 articles of different lengths but all about the same width. Article 2 shortest, article 3 longer than articles 1 and 2 together, with 1 simple seta and 1 broom seta. Article 4 about as long as 3, with 2 simple setae. Following articles slightly narrowing in width distally, last but one article about twice as long as preceding ones with many long and slender aesthetascs.

A2 ( Fig. 6 ): 0.3 as long as body, with 5 peduncular and 9 flagellar articles. Peduncular article 1 short, almost quadrangular, articles 1 to 3 without setae, article 2 longer than 1 and 3, peduncular article 4 longest, with 6 long setae of different lengths, article 5 distally with 7 broom setae and 2 lateral simple setae. Flagellar articles all narrower and shorter, generally decreasing in length to distal tip, with 1 simple distal seta, tip with 3 simple setae of different lengths.

LMd ( Fig. 6 ): Incisor with 4 teeth, lacinia mobilis 0.7 as short as incisor, bearing 3 teeth, spine row of 11 setae, pars molaris stout, tapering distally, with 5 simple setae of various lengths. Mandibular palp absent.

RMd (not illustrated): Similar to left, but without lacinia mobilis, incisor with 3 teeth.

Mx1 ( Fig. 6 ): Inner endite 0.4 as wide as outer endite. Outer endite with 12 strong spine­like simple setae distally and few long marginal setae, inner endite with 1 strong simple seta and some setules.

Mxp ( Fig. 6 ): Endite reaching second palpal article, with 4 fan and several simple setae distally and 2 medial coupling hooks. Palp 0.5 as long as basis. First palp article shortest, ring­like, with 1 distomedial simple seta; article 2 broadest and longest, with 2 distomedial simple setae; article 3 0.5 as wide as article 2, with 4 medial simple setae, article 4 narrow, 0.2 as wide as article 3, with 2 simple distolateral setae, last article narrowest, as long as first, with 4 simple setae. Epipod length 4 times of width, epipod slightly shorter than basis, semicircular in shape.

P1–P4 ( Fig. 7 ): P1 ( Fig. 7 ) slightly shorter than 2 and 3, about as long as P4, but more stout, basis longest article, with 2 ventral simple setae, 4 dorsal broom setae. Ischium 0.7 as long as basis, with 1 short ventral and 1 long dorsal simple setae. Merus smaller, 0.7 as long as ischium, with 7 simple setae, carpus about as long as propodus, with 3 ventral sensory setae, only 1 long dorsal seta. Propodus with 3 ventral setae and 1 distodorsal simple seta. Dactylus 0.8 as long as propodus, with 3 apical setae, 2 claws and 1 seta between claws.

P2–P3 ( Fig. 7 ): Similar in general shape, P3 longer than P2. Bases of different lengths, of P2 longer and more slender than of P3, with 1 dorsal broom seta in P2, 3 in P3, 3 long ventral simple setae. Ischia and meri distodorsally with several long sensory setae on both pereopods, with more, longer, and more slender setae on P3. Carpi 1.1 as long as meri, also with long setae especially distodorsally. Propodus about as long as dactylus, with 2 ventral simple short setae, dactylus tip with 4 apical setae, 2 claws and 1 seta between claws.

P4 ( Fig. 7 ): Smallest and shortest, with long and slender basis bearing 1 broom seta only, ischium 0.8 as long as basis, with 1 distomedial long seta, merus and carpus shorter than ischium, merus with 2 very long distal and 1 shorter medial sensory seta, carpus with 4 sensory setae of different lengths and 1 distodorsal broom seta, propodus shorter than carpus, with 1 distodorsal broom, 1 simple seta and 1 small distoventral sensory seta; dactylus with 2 claws of different lengths and 2 setae inbetween.

P5–P7 ( Figs 7–8 ): Of different lengths. P7 longest ( Fig. 8 ), P 5 ( Fig. 7 ) shortest of posterior pereopods, carpi and propodi of posterior pereopods longest articles, propodus of P6 longest. Basis of P5 with 5 broom, and 3 simple setae, ischium as long as basis, with 4 setae of different lengths, merus 0.8 as long as ischium, with 6 setae of different lengths, carpus with 1 distodorsal broom seta and 4 very long distal sensory setae, propodus about as long as carpus, with 1 distodorsal broom seta and 2 distal sensory setae, dactylus 0.3 length of propodus, with 1 long dorsal and 1 shorter ventral claw and 2 setae inbetween. Basis of P6 ( Fig. 13 ) dorsally with 2 broom setae, 5 ventral setae, ischium 1.1 as long as basis, with 5 long ventral and 3 dorsal sensory setae, merus 0.9 as long as ischium, with 1 medioventral and 8 distodorsal sensory setae of varying lengths, carpus 1.6 as long as merus, with 3 medioventral and 2 mediodorsal long sensory setae, 6 distal sensory setae and 1 distodorsal broom seta, propodus as long as ischium, with 3 medioventral and 3 distal sensory setae of different lengths and 1 distodorsal broom seta, dactylus 0.8 as long as propodus, with 1 very long and 1 very short claw and 1 seta. P7 ( Fig. 14 ) very long and slender, basis slightly shorter than ischium, with 8 ventral and 4 dorsal simple setae, ischium with 7 ventral and 4 dorsal setae, merus 0.6 as long as ischium, with 6 ventral and 3 distodorsal setae, carpus slightly longer than ischium, with 10 ventral short sensory setae, 1 distoventral and 1 distodorsal broom seta, 4 dorsal simple setae; propodus longest article, almost twice as long as carpus, with 14 ventral setae and 1 distodorsal broom seta, dactylus also long and slender, slightly shorter than propodus, with 1 very long and slender distal claw, 1 very short one and 1 broom distal seta.

Plp 1 ( Fig. 8 ): Long and slender, broadest proximally, proximal third with lateral setules, slightly bent ventrally, with serrated longitudinal keels on ventral basal half. Distal tips with 7 setae of varying lengths, medial ones longest.

Plp 2 ( Fig. 8 ): Slightly bent, with long and slender sympod, bearing 9 proximolateral whip setae, 7 long plumose setae around distal tip. Stylet 0.4 as long as sympod, not reaching tip of sympod, exopod small, bare.

Plp 3 ( Fig. 6 ): Endopod much longer than wide, almost rectangular, with 3 distal plumose setae, exopod slightly shorter than endopod, laterally and medially with simple setules.

Plp 4 ( Fig. 6 ): Endopod round­oval, bare, twice as long as wide, exopod almost as long as endopod, distally with 1 long plumose seta.

Plp 5 (not illustrated) only 1 small oval lobe.

Urp ( Fig. 8 ): Very long and slender; sympod 32 times as long as wide, bearing 7 sensory setae laterally, additional 4 distally and 1 lateral broom seta. Only 1 ramus, 56 times as long as wide, with 3 lateral simple short setae and 5 distal broom setae as well as 3 long distal simple setae of different lengths.

Remarks. Macrostylis longipedis sp. nov. can easily be distinguished from the other species of the genus by the extremely long seventh pereopod, which is more than twice as long as the body. The uropods of M. longipedis are slightly longer than the body, much longer than in the other known species of Macrostylis , allowing easy identification lasting the absence pereopod 7. The last two flagellar articles of the male antenna possess a huge number of very long and slender aesthetascs, each of which is about as long as the article itself, another unique character within the genus. Females are not known.

Figures

FIGURE 6. Macrostylis longipedis sp. nov., holotype ɗ (2.5 mm), dorsal and lateral views, antennule, antenna, left mandible, maxillule, maxilliped, pleopods 3, 4.

FIGURE 7. Macrostylis longipedis sp. nov., holotype ɗ (2.5 mm), pereopods 1 – 5.

FIGURE 8. Macrostylis longipedis sp. nov., holotype ɗ (2.5 mm), pereopods 6, 7, pleopods 1, 2, uropod.

FIGURE 13. Macrostylis meteorae sp. nov. holotype Ψ (2.2 mm), pereopods 1, 2, 4, 5, pleopods 2 – 5, uropod.

FIGURE 14. Macrostylis abyssalis sp. nov. holotype Ψ (2 mm), in dorsal and lateral (pereonites 4 – 7) views, paratype female, antennule, antenna, left and right mandibles, maxillule, maxilliped, pereopods 1, 2.