Regabellator abyssi, 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 : 4-9

publication ID	https://doi.org/ 10.5281/zenodo.155900
DOI	https://doi.org/10.5281/zenodo.6277491
persistent identifier	https://treatment.plazi.org/id/7B0F5E35-265F-FFC7-FA3D-F9FB33DBF950
treatment provided by	Plazi
scientific name	Regabellator abyssi
status	sp. nov.

Treatment

Regabellator abyssi View in CoL n. sp. ( Figs. 1 5 View FIGURE 1 View FIGURE 2 View FIGURE 3 View FIGURE 4 View FIGURE 5 )

Holotype: ZMH, Nr. K40104, female 2.1 mm, station 348, 28 July 2000, 16°18.1'S 05°27.2'E 16°19.3'S 05°27.2'S, 5389 m

Paratypes: ZMH, Nr. K40105, 2 females of 2.4 and 2.9 mm (the latter preparatory), station 348, 28.7.2000, 16°18.1'S 05°27.2'E 16°19.3'S 05°27.2'S, 5389 m; 1 female of 2.9 mm, station 340, 22.7.2000, 18°18.3'S 04°41.3'E 18°19.4'S 04°41.9'E, 5395 m, 1 manca I 1.8 mm, station 344, 25.7.2000, 17°06.2' S 04° 41.7'E 17°07.5'S 04°42.3'E, 5415 m.

Type locality: Angola Basin, Atlantic, 53895415 m.

Distribution: only known from type locality.

Etymology: named for the type locality, the abyss of the Angola Basin.

Description: Habitus of female holotype ( Fig. 1 View FIGURE 1 ): Body dorsally smooth, without setae or elevations, and also without setules on lateral margins of pereonites and pleotelson. Lateral and caudal margin of pleotelson smooth, without spines or notches. Cephalothorax broader than long, ( Fig. 1 View FIGURE 1 ), without rostrum, frontomedial margin slightly rounded, lateral margins of cephalon smooth and straight, eyes lacking; antennae inserting frontolaterally.

Coxae not visible in dorsal view. Pereonites 1 4 only with slightly frontally directed frontolateral aspects, pereonite 1 as long as 2 and 3, pereonite 3 slightly longer than the anterior ones; pereonite 5 about as long as 4, pereonites 6 and 7 dorsomedially fused, slightly longer than pereonite 5. Pereonite 6 with medioventral spine directed caudally. Pleonites fused with pleotelson. Pleotelson longer than broad. Lateral view illustrates that pleotelson is quite long. Since the specimen was slightly curved and could not be straightened before pereopods were dissected, dorsal view portrays pleotelson deceptively shorter than it actually is.

Basal article of Al ( Fig. 2 View FIGURE 2 ) large, almost quadrangular, with 2 featherlike setae; article 2 slightly longer, with two blunt elevations of different lengths and two featherlike setae on top of these; article 3 shortest, ringlike, without setation. 2 flagellar articles, first with 2 featherlike setae; terminal article bulbous, with 4 setae and one aesthetasc.

A2 article 1 ( Fig. 2 View FIGURE 2 ) short, nearly square, with 1 seta; article 2 slightly longer than 1, without setae; article 3 slightly longer than 2, with 1 medial and 2 lateral setae; article 4 shortest, with 2 setae; article 5 slightly longer than articles 14 together, with 3 distal setae and 1 featherlike seta; article 6 slightly longer than 5, with 3 medial and 3 lateral setae and 3 distal featherlike setae; flagellar article 1 1ongest, as long as peduncular articles 1 3, with 4 setae; flagellar articles 27 decreasing in length and width distally, with 34 setae, terminal article small, knoblike, with 5 setae and one featherlike seta.

Mandibular palp ( Fig. 2 View FIGURE 2 ) not reaching the distal tip of the pars incisiva, palp inserted in proximal third of mandibular body, consisting of 3 articles; article 2 longest, article 1 with 1 seta in both mandibles; article 2 nearly twice as long as 1, with 2 ventral setae and several setal combs. lMd with 2 additional dorsal setae; article 3 with 2 distal setae and several setules. lMd incisor with 5; lMd lacinia mobilis with 4 teeth rMd incisor with 3 teeth. Both Md setal row with 8 setae. Molars small, short, acuminating, bearing a tuft of 6 long, slightly serrated setae. RMd without lacinia mobilis.

Mxl ( Fig. 2 View FIGURE 2 ) inner endite lateral margin without setae, distally with tuft of many slen der setae and 2 stouter spinelike ones. Lateral endite tip with 12 serrated spines, medial margin without setules, outer margin with 2 setae.

Mx 2 lateral and inner endites ( Fig. 2 View FIGURE 2 ) outer margins with long setae, inner endite inner margin setose, with 5 fringed setae distally. Lateral and medial endites with 3 stout setae.

Mxp epipod ( Fig. 3 View FIGURE 3 ) short, bare, reaching to lateral edge of endite. palp article 1 short, rectangular, without setae; article 2 4 times as long as 1, with 2 medial and 1 lateral setae, palp article 3 medial margin with 5 setae on a serratedtoothed margin; palp article 4 slightly longer than 1, 1/3 width of palp article 3, with 2 setae; palp article 5 slightly shorter and narrower than 4, with 3 setae. Endite with 2 medial coupling hooks, without ventral setae, distally extending to distomedial margin of palp article 2, distally with 2 fanlike setae.

Pereopods ( Figs. 35 View FIGURE 3 View FIGURE 4 View FIGURE 5 ) similar in shape; pereopod 1 shortest, posterior pereopods becoming progressively longer. Pereopod 1 ( Fig. 3 View FIGURE 3 ) of female with few setae as figured. Dactylus with 2 distal claws, 2 long, simple medial setae 4 shorter setae.

P17 ( Figs. 35 View FIGURE 3 View FIGURE 4 View FIGURE 5 ) bases longest article, with simple and 05 featherlike setae of varying lengths, distodorsally 13 comblike structures. Ischium of all pereopods with one dorsal seta and 12 ventral setae. Merus shorter than ischium, with 12 distodorsal setae and a ventral simple one. P24 carpus longer than propodus. P57 carpus about as long as propodus with dorsal and ventral rows of long sensory setae, distodorsally with a featherlike seta. Carpus of P4 and P7 without setae. Propodus with dorsal and ventral sensory setae and a distodorsal featherlike seta. P57 with fewer and more slender sensory setae on carpus and propodus than P14. Dactylus short, half length of propodus, with 2 unequal claws, 4 distodorsal setae and 2 setae inserted between claws.

Female Plp2 ( Fig. 3 View FIGURE 3 ) operculiform, broad ovate, with a dense row of caudolateral short setae.

Plp3 exopod ( Fig. 5 View FIGURE 5 ) subtriangular, lateral and medial margins with small setules, with long apical seta distally. Endopod 4 times as long as exopod, with 3 long fringed setae.

Plp 4 ( Fig. 5 View FIGURE 5 ) with bare, broadoval endopod. Exopod slightly shorter than endopod and slender (a fifth as wide as endopod), laterally with some short setules and distally with a long fringed seta. Plp5 (not illustrated) with one small ovalshaped lobe without setation.

Uropod ( Fig. 5 View FIGURE 5 ) long with quadrangular sympod, which is only slightly longer than exopod, bearing 1 long seta. Exopod 1/3 endopod length, with 2 long setae. Endopod more than twice width of exopod, with 4 long setae and 3 featherlike setae of different lengths.

Remarks

Siebenaller & Hessler 1981 described the genus Regabellator and published an extensive diagnosis of the genus, some of these characters are the dorsally fused pereonites 6 and 7, a bulbous antennuler terminal article, two large ventral spines on pereonites 6 and 7, the posterior one with a broad basal region, pereopods 24 with very long robust setae from ventral to dorsal surfaces of propodus and carpus, pereopods 57 not broadened, without natatory setae. Regabellator abyssi n. sp. can easily be distinguished from R. profugus Siebenaller & Hessler, 1981 , the species it most closely resembles. The pleotelson of R. abyssi is laterally smooth and lacks tiny laterocaudal notches present in R. profugus . Ventral spine of pleonite 6 is directed caudally, and not frontally in R. abyssi . Maxillipedal epipod of R. abyssi is short, reaching only to tip of palp article 1, whereas in R. profugus epipod reaches apical margin of palp article 2. Pereopod 4 with fewer and more slender, and longer sensory setae than in R. abyssi . Uropodal exopod of R. abyssi slightly longer than endopod (roughly 1/4 as long as endopod), whereas R. profugus exopod is only one fifth as long as endopod.