Regabellator abyssi Brandt, 2002, n. sp.
Creators: name: Brandt, Angelika
Publisher: name: Zenodo
Year: 2002
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Isopoda
Nannoniscidae
Regabellator
Regabellator abyssi

description: Regabellator abyssi n. sp. (Figs. 1 ­ 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): 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), 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) 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) 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) 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) 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) 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) 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) similar in shape; pereopod 1 shortest, posterior pereopods becoming progressively longer. Pereopod 1 (Fig. 3) of female with few setae as figured. Dactylus with 2 distal claws, 2 long, simple medial setae 4 shorter setae.
P1­7 (Figs. 3­5) 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) operculiform, broad ovate, with a dense row of caudolateral short setae.
Plp3 exopod (Fig. 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) 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) 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.
description: Published as part of Brandt, Angelika, 2002, New species of Nannoniscidae (Crustacea, Isopoda) and Saetoniscus n. gen. from the deep sea of the Angola Basin, pp. 1-36 in Zootaxa 88 on pages 4-9, DOI: 10.5281/zenodo.155900