Rapaniscus multisetosus, Brandt, Angelika, 2002

Brandt, Angelika, 2002, New species of Nannoniscidae (Crustacea, Isopoda) and Saetoniscus n. gen. from the deep sea of the Angola Basin, Zootaxa 88, pp. 1-36 : 22-27

Rapaniscus multisetosus n. sp. ( Figs. 14­16 )

Holotype: female of 3.8 mm length ZMH, Nr. K­40108, station 348, 28.7.2000, 16°18.1'S 05°27.2'E ­ 16°19.3'S 05°27.2'S, 5389 m.

Paratype: Manca II of 3.1 mm length, ZMH, Nr. K­40109, station 348, 28.7.2000, 16°18.1'S 05°27.2'E ­ 16°19.3'S 05°27.2'S, 5389 m.

Type locality: Angola Basin, Atlantic 5389 m.

Distribution: only known from type locality.

Etymology: named for the many long sensory setae on ventral side of pereopod 1 propodus.

Description: Habitus of holotype female only illustrated in lateral view, as this specimen was bent very much and very fragile ( Fig. 14 ). Body dorsally smooth, without setae, setules or elevations. Lateral and caudal margins of pleotelson also smooth. Cephalothorax broader than long, without rostrum, frontomedial margin slightly rounded, lateral margins of cephalon smooth and straight, eyes lacking; antennae inserting frontolaterally. Coxae not visible in dorsal, but in lateral view ( Fig. 14 ). Pereonite 1 longer than 2 and 3, which are about subequal in length, pereonite 4 longest of the anterior ones; pereonite 5 slightly shorter than 4, pereonites 6 and 7 dorsomedially fused, together slightly longer than pereonite 5. Pleonites all fused with pleotelson. Pleotelson slightly longer than broad. Body quite deep, sternites almost of same measurements as tergites.

Basal article of Al ( Fig. 14 ) large, almost quadrangular, with 2 feather­like setae and one simple one; article 2 1.5 as long as first, with 3 feather­like setae and 2 simple ones, distally with long protrusion and 1 feather­like seta; article 3 shortest, ring­like, without setation. 2 flagellar articles, first with 2 feather­like setae; last one bulbous, round oval, with 1 seta.

A2 broken off in holotype, not illustrated.

Mandibular palp short ( Fig. 14 ), consisting of 3 articles; article 1 and 2 longest, subequal in length, article 2 with 2 distoventral setae; article 3 with 2 distal setae and some setules. Incisor of IMd with many smaller teeth (almost saw­like distal margin), of rMd with 3 teeth, lacinia mobilis of IMd 3 toothed. Setal rows with 9­10 setae. Molars small, short, acuminating, bearing a tuft of long setae, in left mandible there are probably some broken off. RMd without lacinia mobilis.

Mxl ( Fig. 14 ) inner endite not illustrated. Lateral endite with 12 apical spines, medial and lateral margins with fine setules.

Mx 2 ( Fig. 14 ) outer margins of lateral and inner endites with long setules, inner margin of inner endite setose, with 9 setae distally. 3 strong setae of varying lengths on lateral and medial endites.

Mxp epipod ( Fig. 14 ) short, bare, reaching to mid of palpal article 3. First palpal article short, almost rectangular, with 1 seta, second one 3 times as long as first, with 3 medial and 1 lateral setae, medial margin of the 3rd palpal article with 5 setae on serrated margin; article 4 only slightly longer than 1, a sixth as wide as third with 3 setae, and article 5 slightly shorter and narrower than 4, with 4 long setae. 2 coupling hooks medially on endite. Endite without setae ventrally; endite distally reaching to distolateral margin of 2nd palpal article, distally with 3 fan­like and 2 setae.

Pereopods ( Figs 15­16 ) dissimilar in shape; pereopod 1 broadest and stoutest, carpochelate, posterior pereopods longer than anterior. P 1 ( Fig. 15 ) with few simple, but many sensory setae on propodus and carpus. Basis as long as carpus, only with 4 ventral setae and 2 comb­like structures, few setae on ischium and merus. Carpus broad oval, with three simple short dorsal setae and a row of long, strong and stout sensory setae on palma, one long seta distoventrally in distal third of length. Propodus and dactylus subchelate to carpus, propodus distally with 4 setae, ventrally with a row of 5 sensory setae (shorter than of carpus), and a comb­like structure between these. Dactylus with 2 distal claws and 2 long simple medial setae as well as another 4 setae.

P 2 ( Fig. 15 ) with short basis, bearing no setae, merus with 2 distal setae and 1 ventral one, carpus longest article, twice as long as merus, with 3 dorsal setae and a ventral row of 9 sensory setae of different lengths. Propodus slightly more than half as long as carpus, with 2 simple dorsal setae and one feather­like seta, ventrally with a row of 4 long sensory setae and a comb­like structure inbetween, like in P1. Dactylus damaged, dorsal claw broken off in this specimen, otherwise similar to following pereopods.

P 5­7 ( Figs. 15­16 ) (P3, 4 broken off in this specimen): bases longest article, with 1­3 feather­like setae of varying lengths dorsally, ventrally 0­6 setae. Ischium with 1 dorsal seta (in P7 without) and 1­2 ventral setae; merus about half as long as ischium, with 1­2 distodorsal setae and 2­3 ventral simple ones; carpus about as long as propodus, with few ventral simple and 1­2 long sensory setae, distodorsally of P6 1 feather­like seta, absent in P5 and P7; propodus also with ventral sensory setae and 1 distodorsal feather­like seta (not in P5), and long setae; dactylus shortest article, a third as long as propodus, with 2 claws of different lengths, 4 distodorsal setae and 2 setae inserted between claws.

Plp2 of female ( Fig. 16 ) operculiform, almost round, with 2 groups of caudolateral short setae.

Plp3 exopod ( Fig. 16 ) uniform, rounded, laterally and medially surrounded by small setules, distally bearing 1 apical long seta. Endopod 2 times as long as exopod, with 3 fringed distal setae.

Plp 4 ( Fig. 15 ) with bare, broad, almost quadrangular endopod. Exopod as long as endopod and slender (a fourth as wide as endopod), with 1 long fringed seta. Plp5 ( Fig. 16 ) only one small lobe without setation.

Uropod ( Fig. 16 ) long with quadrangular sympod, bearing 1 distomedial lobe with 1 seta and 1 distomedial seta; exopod almost one half of endopod length, with 2 long setae; endopod only slightly wider than exopod, with 5 long feather­like setae (2 of these broken off) and 2 additional setae.

Remarks

Rapaniscus Siebenaller & Hessler, 1981 is characterised by dorsomedially fused pereonites 6 and 7, a 5­segmented antennule with a swollen last article, a massive pereopod 1 with a broad carpus, bearing long, robust setae, and a female with a large recurved ventral spine on operculum. These characters are present in R. multisetosus n. sp. as well, however, the carpus of pereopod 1 of the new species bears a row of much stronger and longer sensory setae than in R. dewdneyi Siebenaller & Hessler, 1981 , or R. crassipes Siebenaller & Hessler, 1981 . The propodus of pereopod 1 of R. multisetosus is also much shorter, only half as long as carpus.

Figures

FIGURE 14: Rapaniscus multisetosus n. sp., holotype female of 3.8 mm length in lateral view, antennule, left mandible, right mandible, maxillula, maxilla, maxilliped.

FIGURE 15: Rapaniscus multisetosus n. sp., holotype female of 3.8 mm length, pereopods 1, 2, 6.

FIGURE 16: Rapaniscus multisetosus n. sp., holotype female of 3.8 mm length, pereopods 5, 7, pleopods 2 ­ 5, uropod.