Saetoniscus meteori, 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 : 12-22

Saetoniscus meteori n. sp. ( Figs. 6 ­13)

Holotype: female of 2.8 mm length, ZMH, Nr. K­40106, station 348, 28 July 2000, 16°18.1'S 05°27.2'E ­ 16°19.3'S 05°27.2'S, 5389 m.

Paratype: 1 male, 2.8 mm, 3 females 2.7, 2.8, and 2.8 mm and 1 manca II 2.5 mm, ZMH, Nr. K­40107, same station as holotype.

Type locality: Angola Basin, Atlantic, 5389 m.

Distribution: known only from type locality.

Etymology: named after the German research vessel Meteor which collected the samples.

Description: Habitus of holotype female ( Fig. 6 ): Body dorsally smooth, without ornamentation, without setae, setules present on lateral margins of pereonites and pleotelson. Pleotelson lateral and caudal margins smooth. Cephalothorax broader than long, without rostrum, frontomedial margin nearly straight, lateral margins of cephalon smooth and straight, eyes lacking; A1 and A2 inserting frontolaterally. Coxae not visible in dorsal aspect, coxae 2­5 visible in lateral aspect. Pereonite 1 shortest, subequal to pereonite 7, pereonites 2­4 longer than pereonite 1 and 7, pereonite 5 subequal to pereonite 4, pereonites 6 and 7 dorsomedially fused, their combined length subequal to the combined length of pereonites 1 and 2. Pleonites fused with pleotelson. Pleotelson longer than broad.

Paratype male (dorsal and lateral view) is illustrated in Fig. 6 . Following figures show paratype male to avoid dissection and destroying of the holotype.

Al peduncular article 1 ( Fig. 7 ) large, subcircular, slightly longer than wide, with 1 feather­like seta; article 2 slightly longer, with four feather­like setae of different lengths; article 3 shortest, ring­like, without setation. Flagellum of 2articles, article 1 with 2 feather­like setae on top of a distolateral prolongation; distal article bulbous, round oval.

A2 article 1 ( Fig. 7 ) of male short, subtriangular, without setae; article 2 as long as 1, quadrangular, without setae; article 3 is 1.5 times as long as 2, with 1 seta on a lateral protrusion and 1 seta medially; article 4 shortest, with 1 seta; article 5 slightly swollen, about as long as articles 1­4 together, with 3 setae and 1 feather­like seta; article 6 about as long as 5, with three medial and three lateral setae and 1 distal feather­like seta; 10 flagellar articles, flagellar article 1 swollen, 1ongest, longer than peduncular article 6, with 3 setae; distal 9 flagellar articles tapering in width, with 1­3 setae, last article with 6 setae.

Mandibular palp ( Fig. 7 ) not reaching the distal tip of the pars incisiva, palp inserted in proximal fourth of mandibular body, 3 articulate; article 2 longest, articles 1 and 2 without setae in lMd and in rMd; article 2 3 times as long as article 3; article 3 with 3 distal setae and serveral setules. Incisor of lMd with 6, of rMd with 4 teeth, lacinia mobilis of lMd 3 teeth. Setal rows with 9 and 8 setae on left and right mandibles, respectively. Molars small, short, acute, bearing a tuft of long, distally serrated setae. RMd without lacinia mobilis.

Mxl ( Fig. 7 ) inner endite lateral and medial margin without short setae, distomedially with tuft of many slender setae and 2 stouter spine­like ones. Lateral endite tip with 11 serrated spines, medial and lateral margins with few setules.

Mx 2 ( Fig. 8 ) lateral and inner endites outer margins with long setules, inner margin with 6 setae distally. Lateral endite with 3 stout setae of varying lengths, medial endite with 4 setae.

Mxp epipod ( Fig. 9 ) long and slender, bare, distally acute, reaching almost to distal margin of palp article 4. Palp article 1 short, rectangular, without setae; second one 4 times as long as first, with 2 medial and 1 distolateral setae; article 3 slightly shorter than article 2, medial margin with 3 setae on serrated­toothed medial margin and 1 seta on lateral margin; article 4 slightly longer than 1, article 3 as wide as second with 3 setae; article 5 slightly shorter and narrower than 4, with 3 long setae. Endite with 3 medial coupling hooks, without setae ventrally, distally extending to distal margin of palp article 2, distally with 1 fan­like seta.

Pereopods ( Figs. 8­10 ) similar; P1 shortest, posterior pereopods longer than anterior. Female P1 ( Fig. 8 ) with setae as figured. Basis with 4 setae and 2 comb­like structures, setae on ischium, merus, and carpus, carpus also with a distoventral small comb, propodus distally narrowing, with 4 setae and few short ventral setules, dactylus with 2 distal claws and 2 long simple medial setae and 4 subapical setae.

Pereopods 1­7 ( Figs. 8­10 ) bases longest article, with some simple and 1­3 feather­like setae of varying lengths. Ischium of all pereopods with one distodorsal seta, of P5 and P6 with three dorsal setae and 0­1 ventral setae. Merus shorter than ischium, with 1­2 distodorsal setae and 1­2 ventral simple ones. Carpus longer than propodus in P2­4 more different than in P5­7, with a ventral row of 3­7 long sensory setae, dorsally with long setae and a feather­like seta in P4­6, propodus with 1­3 ventral sensory setae, a distodorsal feather­like seta and some simple long dorsal setae; P5­7 with fewer and much longer and more slender sensory setae on carpus. Dactylus shortest article, half as long as propodus, with 2 claws of different lengths, 4 distodorsal setae and 2 setae inserted between claws.

Pleopod 1 ( Fig. 10 ) 3.8 times as long as broad narrowing smoothly, tip 0.5 as long as proximal width, tips rounded, with few simple short setae. Pleopod 2 ( Fig. 10 ) sympod length 2.7 width. Lateral margin slightly rounded with 3 distolateral plumose setae. Endopod inserting at 0.3 sympod length from distal tip. Stylet half as long as sympod, only slightly bent. Exopod, small, bare, without setae. Exopod of Plp3 ( Fig. 10 ) uniform, rounded, laterally and medially surrounded by small setules, distally bearing an apical long seta. Endopod 3 times as long as exopod, with 3 fringed short setae. Plp 4 ( Fig. 10 ) with bare, broad­oval endopod. Exopod one third shorter than endopod and slender, distally with a fringed seta. Plp5 only one small oval lobe without setation.

Uropod ( Fig. 10 ) with short quadrangular sympod, which is twice as long as exopod, bearing 3 long setae; exopod less than one fifth of endopod length, with 4 distal featherlike setae of different lengths.

Paratype female ( Figure 6 shows lateral view of holotype) similar to male in habitus, but Plp2 ( Fig. 11 in detail) operculiform, broad ovate, with a dense row of caudal short whip setae. Additional differences of paratype female: A1 ( Fig. 11 ) with almost quadrangular first peduncular article, bearing 2 feather­like setae, second peduncular article also longer than first, like in male, but distally twice as broad as proximally, bearing 3 long feather­like setae, first flagellar article without, but second with a feather like seta, last bulbous flagellar article more elongate, with a short seta. Incisor of lMd ( Fig. 11 ) only with 4 teeth; P1 (Fig. 111) merus with 2 distodorsal setae, carpus with three, P2­7 ( Figs 11 ­13) with more ventral and dorsal setae on carpus and propodus. Plps 3­5 (Fig. 13) similar to male, exopod of pleopod 4 longer, plumose setae of Plps 3 and 4 longer.

Remarks

Saetoniscus meteori n. sp. is the only species of the genus. It is most similar to Regabellator Siebenaller & Hessler, 1981 and Exilinuscus Siebenaller & Hessler, 1981, differences to these genera are discussed under remarks of the genus diagnosis earlier in the manuscript.

Figures

FIGURE 6: Saetoniscus meteori n. sp. et n. gen., paratype male in dorsal (left) and lateral view (middle), holotype female in lateral view (right).

FIGURE 7: Saetoniscus meteori n. sp. et n. gen., paratype male, antennule (A 1), antenna (A 2), right mandible (rMd), left mandible (lMd), maxillula (Mx 1).

FIGURE 8: Saetoniscus meteori n. sp. et n. gen., paratype male of 2.8 mm, maxilla, maxilliped, pereopods 1, 2.

FIGURE 9: Saetoniscus meteori n. sp. et n. gen., paratype male of 2.8 mm, pereopods 3 ­ 6.

FIGURE 10: Saetoniscus meteori n. sp. et n. gen., paratype male of 2.8 mm, pereopod 7, pleopods 1 ­ 5, uropod.

FIGURE 11: Saetoniscus meteori n. sp. et n. gen., holotype female of 2.8 mm, antennule, detail of left mandible, pereopods 1, 2, pleopod 2 (operculum).