Urstylis, 2014

Riehl, Torben, Wilson, George D. F. & Malyutina, Marina V., 2014, Urstylidae - a new family of abyssal isopods (Crustacea: Asellota) and its phylogenetic implications, Zoological Journal of the Linnean Society 170 (2), pp. 245-296 : 267-276

URSTYLIS SOLICOPIA SP. ET GEN. NOV.

FIGURES 11–21

Zoobank registration urn:lsid:zoobank.org:act:8BCACEA0-2180-4CB8-ACF5-0F36DE73A3B8

Etymology

The species name refers to the type locality in the Pacific Ocean (Clarion-Clipperton Fracture Zone; CCFZ) being rich in manganese nodules ( Fig. 10 ). The epithet solicopia is derived from the Latin words soli, singular genitive of solum earth, bottom, and copia meaning plentiful translating into of plentiful bottom. It is a feminine adjective .

Type fixation

Ovigerous female holotype, 2.0 mm, ZMH K-43070, designated here .

Type material examined

ZMH K-43070: ovigerous female holotype, 2.0 mm, station (st.) 8717 . ZMH K-43052: non-ovigerous female paratype, 2.0 mm, st. 8581, greatly damaged ; ZMH K-43053: one non-ovigerous female anterior fragment, sputter-coated for SEM, st. 8687; ZMH K-43054: juvenile female paratype, 1.7 mm, st. 8698 ; ZMH K-43055: adult male paratype, 2.1 mm, st. 8581, dissected for illustrations ; MIMB 28178 : adult male paratype, 1.7 mm, st. 8719 ; ZMH K-43057: juvenile female paratype, 1.2 mm, st. 8670 ; ZMH K-43058, juvenile female paratype, 1.6 mm, st. 8571 ; ZMH K-43059: non-ovigerous female paratype, 2.0 mm, st. 8615, greatly damaged ; ZMH K-43060: juvenile male paratype, 1.1 mm and juvenile female paratype, 1.2 mm; st. 8660 ; MIMB 28178 : one juvenile female, 1.6 mm, and two mancae paratypes, 1.1 mm, st. 8717 ; ZMH K-43062: juvenile female paratype, 1.5 mm, st. 8721 ; ZMH K-43069: ovigerous female paratype, 2.0 mm, st. 213 .

R/V, Research Vessel.

Type locality

Collected with box corer from the Russian claim in the Clarion-Clipperton Fracture Zone manganesenodule area during several expeditions by the Russian Scientific Centre ‘Yuzhmorgeologia’ (Federal State Unitary Geological Enterprise, Southern Scientific & Production Association for Marine Geological Operations), Gelendzhik ( Table 1). The locality is characterized by soft sediment with manganese nodules of varying size and density ( Fig. 10 ).

Type material – remarks

The holotype ovigerous female and several paratypes show some shrinking artefacts possibly caused by treatment with ethanol and low degree of calcification. These caused the depressions shown in the habitus illustrations of the female. The natural condition is shown in the SEM figures. Uropods are broken and missing in the complete type series except in one manca, which is extremely damaged and therefore not illustrated.

Further records

GDFW collection: USA National Oceanic and Atmospheric Administration ( NOAA) Deep Ocean Mining Study ( DOMES), 0.25 m 2 box corer samples: DJ08, manca, DJ08 24.xi.1977 9°25.23′N, 151°4.46′W, 5205 m; DJ32, manca, 30.xi.1977, 9°16.00′N, 151°56.10′W, 5043 m; DJ39, manca, 03.xii.1977, 9°35.80′N, 151°6.80′W, 5117 m; GDFW collection, DJ46, brooding female, five mancae, 19.v.1978, 9°28.00′N, 151°27.60′W, 5216 m ; DJ49, manca, 20.v.1978, 9°23.40′N, 151°25.30′W, 5171 m; DJ73, manca, 27.v.1978, 9°28.10′N, 151°15.60′W, 5107 m.

Diagnosis

Body dorsoventrally flattened, tergite surfaces rather hirsute; pereonite 4 width subequal to pereonite 5 width, pereonite 6 shorter pereonite 5; pereonite 7 posterolateral margins projecting posteriorly. Pleotelson length/width ratio 1.3, paired dorsal organ expressed as pedestal broom setae articulating on flat conical elevations. Pereopod I ischium dorsal lobe with two setae; pereopods’ V–VII ischium and carpus mid-dorsally with seta present.

Description of female

Body ( Figs 11A, B , 12A, C, E ) length 2.0 mm, 3.4 width, dorsoventrally slightly flattened, tergite surfaces hirsute, with long setae on pedestal (calcified) articulations along lateral and anterior tergite margins. Ventral spines on pereonites 1–7 absent. Imbricate ornamentation on cephalothorax–pleotelson covering whole tergite. Cephalothorax–pereonite VII posterolateral setae simple, asensillate.

Cephalothorax ( Figs 11A, B , 12A–E ) length 0.61 width, 0.13 body length; frons in dorsal view convex, smooth, frontal ridge present, slightly convex; dorsal surface with array of setae. Posterolateral margins angular, blunt; posterolateral setae asensillate, simple, flexibly articulated on calcified pedestal articulations. Pereonite 1 length 0.24–0.29 width, 0.07 body length, anterior margin straight. Pereonite 2 length 0.28–0.32 width, 0.08–0.09 body length. Pereonite 3 length 0.32–0.37 width, 0.09–0.10 body length. Pereonite 4 width 1.1 pereonite 5 width, length 0.37–0.38 width; lateral margins in dorsal view convex, almost parallel; posterolateral margins rounded.

Pereonites 5–7 ( Fig. 11A, B ) of similar shape, diminishing in length and width from 5 to 7. Posterior tergite margins with four simple, asensillate, flexibly articulating setae; setae long, extending beyond posterolateral margin. Posterolateral margins rounded. Coxae setose, setae simple, asensillate, on pedestals. Pereonite 5 length 0.45 width, 1.1 pereonite 4 length. Pereonite 6 length 0.44 width, 0.91 pereonite 5 length. Pereonite 7 length 0.43–0.75 width.

Pleonite 1 length 0.32 pereonite 7 length, dorsally with two setae. Pleotelson length 0.22–0.24 body length, 1.25–1.32 width, slightly wider than or as wide as pereonite 7; paired dorsal organ expressed as pedestal broom setae. Posterior margin straight or slightly concave laterally at uropod insertions, apex convex, length 0.13–0.18 pleotelson length, posterolaterally with four simple setae. Pleopodal cavity width 0.80 pleotelson width.

Antennula ( Fig. 11C ) length 0.45 head width, 0.54 antenna length; width 0.90 antenna width. Article 1 without setae. Article 2 with six simple setae. Article 3 length subequal width, with one simple seta. Article 4 length subequal width, with two simple setae. Article 5 distinctly longer than wide, cylindrical. Article 6 with two aesthetascs.

Antenna ( Fig. 11C ) length 0.18 body length; relative length ratios of articles 1.0, 1.3, 1.3, 1.3, 2.0, 2.3, L/W ratios of articles 0.75, 1.0, 0.80, 1.0, 2.5, 2.3. Basis angular with dorsolateral projection; longer than coxa. Ischium angular with medial projection, longer than coxa. Merus shorter than articles 1–3 together, distally with one simple seta. Merus articulating distolaterally on ischium, antennal proximodistal axis with distinctly sharp bend. Carpus longer than merus, distally with seven simple setae. Flagellum with nine articles. Mouthparts as in female.

Pereopod I–VII ( Figs 13–15 ) dactyli with two claws and two sensillae inserting terminally and two sensillae subdistally, pereopod I dorsal claw subequal to dactylus in length, ventral claw length 0.5 dorsal claw length, pereopods’ II−VII dorsal claw length about 0.6 dactylus length, ventral claw scale-like, tiny, length 0.23−0.25 dorsal claw length.

Pereopod I ( Figs 13A , 14A–E ) length 0.24 body length; article L/W ratios 2.9, 1.5, 0.67, 1.3, 2.0, 2.0; relative article length ratios 1.0, 0.45, 0.20, 0.40, 0.30, 0.10. Ischium dorsal margin with two simple setae, dorsal lobe projecting near basal width of article. Merus dorsal margin with two simple setae, one long, one short, ventral margin with two setae, one small, simple, one long, bifid, monoserrate. Carpus dorsally with two simple setae. Articular plate on propodus absent; dactylus distally with two sensillae, dactylus dorsal claw length 1.0 dactylus length.

Pereopod II ( Figs 13B , 14G ) length 0.30 body length; article L/W ratios 3.5, 1.0, 2.0, 2.5, 3.3, 2.5; relative article length ratios 1.0, 0.48, 0.24, 0.48, 0.48, 0.24. Ischium dorsally with two simple setae, one long medially, one short distally, with dorsal setae on dorsal margin. Merus dorsally with two simple setae, one long, one short and slender, with dorsal setae on dorsal margin, ventrally with two simple setae: one short medially, one long distally. Carpus distodorsally with one simple seta, ventrally with three bifid setae. Pereopod III ( Fig. 13C ) length 0.31 body length; article L/W ratios 3.5, 2.2, 1.0, 2.8, 3.7, 2.0: relative article length ratios 1.0, 0.52, 0.24, 0.52, 0.52, 0.19. Ischium with one simple, not prominent seta on apex. Merus dorsally with two long, simple setae, ventrally with two short, simple setae. Carpus distodorsally with one broom seta and one short simple seta; ventrally with three setae: one bifid medially, one simple and one bifid subdistally. Pereopod IV length 0.31 body length, about as long as neighbouring pereopods; article L/W ratios 3.0, 2.2, 1.0, 3.3, 3.7, 2.0; relative article length ratios 1.0, 0.61, 0.28, 0.72, 0.61, 0.22.

Pereopods V–VII ( Fig. 15 ) similar in setation. Ischium mid-dorsally with one simple seta, distodorsally with setae absent, midventrally with two simple setae. Merus distodorsally with two setae, one simple, slender, one bifid, midventrally with one simple, small seta, distoventrally with two setae, one simple, long, one simple, small. Carpus mid-dorsally and distodorsally with one bifid seta respectively, distoventrally with three bifid setae. Pereopod V length 0.33 body length; article L/W ratios 3.4, 2.2, 1.8, 3.3, 6.5, 2.5; relative article length ratios 1.0, 0.65, 0.41, 0.76, 0.76, 0.29. Pereopod VI length 0.35 body length; article L/W ratios 4.3, 2.8, 2.0, 5.0, 7.5, 2.5; relative article length ratios 1.0, 0.65, 0.47, 0.88, 0.88, 0.29. Pereopod VII length 0.37 body length; relative article length ratios 1.0, 0.61, 0.50, 0.83, 0.89, 0.28; article L/W ratios 3.6, 2.8, 2.3, 5.0, 8.0, 2.5.

Operculum ( Fig. 11D, E ) ovoid, length 1.1 width, 0.69 pleotelson dorsal length; apical width 0.82 operculum maximal width. Lateral fringe consisting of ten to 11 setae, with fluent transition to row of 17 asetulate apical setae. Apical setae completely covering anal opening.

Uropod (measured from other material) length 2.8 pleotelson length; protopod length 23.3 width, 2.1 pleotelson length, protopod distal margin blunt, endopod insertion terminal; endopod length 12.1 width, 0.37 protopod length, endopod width; exopod length 0.05 endopod length.

Description of adult male

Body ( Fig. 16A, C ) length 2.1 mm, 4.0 width. Cephalothorax frontal ridge present, slightly convex; length/ width ratio larger than in female, length 0.74 width, 0.15 body length; with conspicuous dorsal array of setae: four simple setae in a quadrate arrangement, posterolateral setae absent, posterior margins setulose. Pereonite 1 length 0.20 width, 0.05 body length. Pereonite 2 length 0.36 width, 0.09 body length. Pereonite 3 length 0.34 width, 0.09 body length. Pereonite 4 posterolateral margins not produced posteriorly.

Pleotelson ( Fig. 16A, C, D ) in dorsal view similar to female, constricted anteriorly to uropod articulation, width maximum anterior to waist, setal ridges not visible in dorsal view; length/width ratio in male subequal to female, 0.23 body length, width subequal pereonite 7 width, tergite with several projecting and calcified pedestals with setal articulations. Posterior apex length 0.14 pleotelson length, pleopodal cavity width 0.87 pleotelson width.

Antennula ( Fig. 16B ) length 0.81 head width, 0.57 antenna length, width 0.88 antenna width; article L/W ratios 1.7, 2.0, 1.0, 1.0, 1.0, 2.0; relative article length ratios 1.0, 0.83, 0.25, 0.25, 0.25, 0.30; terminal and penultimate articles with two aesthetascs respectively. Article 1 with two simple setae and one broom seta. Article 2 with five setae: two simple, three broom. Article 3 with one simple seta and one broom seta. Article 4–5 both with one simple seta. Article 6 elongate, distinctly longer than article 5. Antenna ( Fig. 16B ) length 0.29 body length, flagellum of six to nine articles, article length−width ratios subsimilar in males and females. Merus distally with four simple setae and one broom seta. Carpus distally with ten setae: five simple, five broom.

Mandible ( Fig. 17 ) molar process apex with two spines and three setulate setae; left mandible incisor process with five cusps, lacinia mobilis with four denticles; right mandible incisor process with four cusps, lacinia mobilis with six denticles. Maxillula ( Fig. 18A ) lateral lobe terminally with 11 robust and three slender setae. Maxilla ( Fig. 18B ) lateral lobe with five setae terminally: one robust, serrate, two simple, two slender, simple; middle lobe with five setae terminally: three robust, serrate, two slender, simple; medial lobe terminally with six setae: two short, robust, laterally, two long, robust, two slender, simple. Maxilliped ( Fig. 18C, D ) basis length 3.9 width; endite distally with two fan setae; with two coupling hooks; palp articles 1 and 2 subsimilar in width, article 1 distomedially with one seta, distolateral lobe length 0.35 article 1 length, article 2 wider than article 3, article 1 shorter than article 3, article 4 distomedial extension with three setae, article 5 with five distal setae; epipod length 2.6 width, 0.85 basis length, distolaterally fringed with setulae.

Pereopods I–VI ( Figs 19 , 20 ) similar to those in female in size, proportions and setation. Pereopod VII length 0.42 body length, shorter than pereopod VI; relative article length ratios 1.0, 0.74, 0.58, 1.1, 1.1, 0.26. Article L/W ratios: 3.8, 2.8, 2.8, 6.7, 6.7, 2.5. Pleopod I ( Figs 16D , 21A ) length 0.84 pleotelson length, distal width 1.6 proximal width, distomedial lobes rounded, distally with six to eight long setae, distolateral lobes with five to seven small setae, ventral surface subdistally with five short setae on each side. Pleopod II ( Fig. 21B ) protopod with fringe of> 32 thin setae on distolateral margin; apex projected, narrowly rounded. Endopod distance of insertion from protopod distal margin 0.35 protopod length. Stylet sublinear, extending beyond distal margin of protopod, length 0.88 protopod length.

Pleopod III ( Fig. 21C ) length 1.8 width, protopod length 2.0 width, 0.56 pleopod III length, endopod terminal plumose setae longer than endopod. Exopod length 0.84 pleopod III length, proximal article as wide as endopod, with fringe of fine setae; seta length subsimilar to pleopod III exopod width; distal article length 0.36 proximal article length, width 0.47 proximal article width, conspicuous subterminal seta present. Pleopod IV ( Fig. 21D ) length 2.0 width, endopod length 1.7 width, exopod length 4.7 width, exopod length 0.78 endopod length, lateral fringe of setae present. Pleopod V ( Fig. 21E ) length 2.4 width.

Remarks

Urstylis solicopia gen. et sp. nov. is the most setose species currently known for this genus. The anterior tergites bear rows of setae along their anterior margin as well as medially across the segments. The posterior tergites have medial and posterior rows of simple setae. Another distinguishing feature is that all pereonal and pleonal tergites of U. solicopia are covered with imbricate ornamentation and to a lesser degree the sternites, too. Dorsally on the pleotelson, a pair of broom setae on flat, cone-shaped elevations is located in approximately the same position as the tubercles in U. zapiola or the statocysts in Macrostylis . The operculum of this species has a lower length−width ratio than in U. zapiola .

The 0.25 m 2 box corer samples from the USA National Oceanic and Atmospheric Administration (NOAA) Deep Ocean Mining Study (DOMES) collected by GDFW and colleagues in 1977–1978 provide data on the population of this species at DOMES site A. The species appeared in six out of 55 samples with a total of 11 individuals. As the samples were open box corers with no partitions, the total area sampled is 13.75 m 2, which gives a population density of this species of 0.8 individuals per m 2, based on random expectations. As most species do not occur randomly but show patchy (under-dispersed) distributions ( Kaiser & Barnes, 2008), the effective density can be expected to be much higher. Despite the large number of samples collected at DOMES site A, no males were found, suggesting that, as observed in haploniscids ( Brökeland, 2010), macrostylids ( Riehl & Kaiser, 2012), and tanaids, the males occur at a lower density than females or juveniles. The expectation that juveniles should be the most frequent size class is borne out by these samples.

Figures

Figure 10. Bottom characteristics in the Russian claim in the Clarion-Clipperton Fracture Zone manganese-nodule area at the type locality of Urstylis solicopia gen. et sp. nov. Station 90, R/V Yuzhmorgeologia cruise 4–06; 13°13.11780′N, 134°29.49900′W; 4804 m. A, photograph taken by autonomous camera mounted on giant box corer before impact. B, box core sample, size of sample 0.25 m2, scale: one interval on left inner wall of the box = 5 cm. Courtesy of Slava Melnik, State Scientific Center Yuhzmorgeologia.

Figure 11. Urstylis solicopia gen. et sp. nov., ovigerous female holotype ZMH K-43070. A, habitus, lateral. B, habitus, dorsal. C, antennula and antenna, dorsomedial, in situ. D, pleopods, ventral, in situ. E, pleotelson, ventral. Scale bars = 0.5 mm (A, B, E); 0.1 mm (C); 0.2 mm (D).

Figure 12. Urstylis solicopia gen. et sp. nov., paratype female fragment ZMH K-43053. A, lateral habitus. B, lateral cephalothorax. C, ventral habitus. D, frontal head. E, dorsal habitus. F, mouthfield. G, cephalothorax right posterolateral margin and pereonite anterolateral margin. H, pereonite 2 posterolateral margin, lateral view. Scale bars = 0.1 mm (A–F); 10 μm (G, H).

Figure 13. Urstylis solicopia gen. et sp. nov., ovigerous female holotype ZMH K-43070. A, pereopod I. B, pereopod II. C, pereopod III. Scale bar = 0.2 mm.

Figure 14. Urstylis solicopia gen. et sp. nov., paratype female fragment ZMH K-43053. A, pereopod I propodus distodorsal margin bisetulate seta. B, medial pereopod I propodus, dactylus. C, lateral pereopod I. D, pereopod I carpus distoventral margin robust seta with subdistal fringe-like sensilla. E, pereopod I ventral dactylus. F, pereopod II dorsal dactylus. G, pereopod II medial dactylus. H, close-up of G. I, pereonite 2 lateral dactylus. Scale bars = 10 μm (A, B, D–I); 0.1 mm (C).

Figure 15. Urstylis solicopia gen. et sp. nov., ovigerous female holotype ZMH K-43070. A, pereopod IV. B, pereopod V. C, pereopod VI. D, pereopod VII. Scale bar = 0.2 mm.

Figure 16. Urstylis solicopia gen. et sp. nov., adult male paratype ZMH K-43055. A, habitus, dorsal. B, cephalothorax, lateral. C, habitus, lateral. D, pleotelson, ventral. Scale bars = 0.5 mm (A, C); 0.3 mm (B); 0.2 mm (D); 0.05 mm (E).

Figure 17. Urstylis solicopia gen. et sp. nov., adult male paratype ZMH K-43055. A–C, left mandible. D–F, right mandible. Scale bar = 0.1 mm.

Figure 18. Urstylis solicopia gen. et sp. nov., adult male paratype ZMH K-43055. A, maxillula. B, maxilla. C, maxilliped, ventral, endite setation omitted. D, maxilliped endite close-up, dorsal. Scale bars = 0.1 mm.

Figure 19. Urstylis solicopia gen. et sp. nov., adult male paratype ZMH K-43055. A, pereopod I. B, pereopod II. C, simple seta as found on the trunk cuticle and pereopods with indicated internal structures. D, simple seta with cuticle broken and internal tissue exposed distally. E, bisetulate seta. F, pereopod III. G, pereopod IV. Scale bars = 0.1 mm (A, B, F, G); 0.025 mm (C–E).

Figure 20. Urstylis solicopia gen. et sp. nov., adult male paratype ZMH K-43055. A, pereopod V. B, pereopod VI, basis broken and lost, ischium damaged. C, pereopod VII. Scale bar = 0.1 mm.

Figure 21. Urstylis solicopia gen. et sp. nov., adult male paratype ZMH K-43055. A, pleopod I. B, pleopod II, ventral. C, pleopod III. D, pleopod IV. E, pleopod V. Scale bar = 0.1 mm.