Synagoga arabesque, Kolbasov, Gregory A., Petrunina, Alexandra S., Ho, Ming-Jay & Chan, Benny K. K., 2019

Kolbasov, Gregory A., Petrunina, Alexandra S., Ho, Ming-Jay & Chan, Benny K. K., 2019, A new species of Synagoga (Crustacea, Thecostraca, Ascothoracida) parasitic in an antipatharian from Green Island, Taiwan, with notes on its morphology, ZooKeys 876, pp. 55-85 : 55

publication ID	https://dx.doi.org/10.3897/zookeys.876.35443
publication LSID	lsid:zoobank.org:pub:C63AD0D7-F0A1-4596-922D-8C42D44604E1
persistent identifier	https://treatment.plazi.org/id/3BE6E08C-6AF5-45A9-946D-7DA1AF2BD63D
taxon LSID	lsid:zoobank.org:act:3BE6E08C-6AF5-45A9-946D-7DA1AF2BD63D
treatment provided by	ZooKeys by Pensoft
scientific name	Synagoga arabesque
status	sp. nov.

Treatment

Synagoga arabesque sp. nov. Figs 1 View Figure 1 - 18 View Figure 18

Type locality.

Gongguan harbor, Green Island (Ludao), ca. 33 km off the southeastern coast of Taiwan, 22°41.438'N, 121°29.678'E, 35 m depth, 08 and 09 September 2017.

Material examined.

Twelve specimens of the new species, Synagoga arabesque sp. nov. (five males and seven females), were collected from two colonies of the antipatharian Myriopathes cf. japonica . Slides of the holotype female Mg 1243, and three paratypes (female, Mg 1244 and two males, Mg 1245) are deposited in the Zoological Museum of Moscow State University in Moscow, Russian Federation. The remaining two undissected paratypes (female and male) are deposited in alcohol in the Biodiversity Research Museum, Biodiversity Research Center, Academia Sinica, Taipei, Taiwan (ASIZCR000412). The other four SEM specimens and two undissected specimens in alcohol have been retained by the first author for further study and comparison with other synagogids.

Diagnosis.

Diagnoses for both adult females and males are provided for the new species, and a full list of interspecific differences is given in Table 2 View Table .

Females: carapace oval, slightly elongated in posterio-dorsal direction, up to 2.3 mm long and 2.0 mm high, with projecting posterio-dorsal tip. Massive setae (spines) of fourth antennular segment with row of dense, conspicuous denticles along anterior edge and rare, tiny denticles on posterior edge; fifth segment with 6-9 large setae; concave margin of antennular claw serrate in middle part. Exopod of second segment of thoracopod I with seven setae. Telson spines ca. 1/3 of blade length of furcal ramus; inner surface of furcal ramus with eight setae. Gut diverticulum red-orange, W-shaped, with numerous branches; dorsal, ventral, anterior and posterior branches terminate with light orange, wide areas at the edge of carapace.

Males: carapace ellipsoidal, up to 1.5 mm long and 0.9 mm high, with slightly projecting posterio-dorsal tip. Massive setae (spines) of fourth antennular segment differing slightly in length, with anterior and posterior rows of small denticles; fifth segment with 4-6 large setae; other characters of antennules similar to those in female. Exopod of second segment of thoracopod I with eight setae. Telson spines ca. 1/3 of blade length of furcal ramus; inner surface of furcal ramus with six setae. Gut diverticulum red-orange, W-shaped, with short anterior, posterior, and two ventral branches; branches terminate with light orange wide areas at edge of carapace.

Etymology.

From French arabesque borrowed from Italian arabesco - foliate ornament, used in the Islamic world, referring to the complex ornament of gut diverticula in carapace valves. The name arabesque has no appropriate equivalent in Latin and is used in this context as an arbitrary combination of letters (sensu ICZN Article 11.3) to avoid using the word in the vernacular.

Relation to host and behavior.

Animals were seen freely swimming from one branch of the antipatharian colony to another and represent small predators rather than ectoparasites. All live specimens of Synagoga were collected after washing the colonies. Animals were quite motile and moved in a Petri dish by jumping. To accomplish these jumping movements, they bent and unbent their developed abdomen with furca, while thoracopod beating was used for slow swimming.

Description.

Living specimens of both sexes semitransparent, light colored, but with bright red-orange gut diverticula; rounded embryos brooded inside female mantle cavity visible through carapace ( Figs 1 View Figure 1 , 2 View Figure 2 ). Abdomen and antennules often extending out of carapace during movements ( Fig. 1 B–D View Figure 1 ).

Female ( Figs 1 View Figure 1 - 4 View Figure 4 , 8 View Figure 8 - 12 View Figure 12 ): Carapace oval, up to 2.3 mm long and 2.0 mm high, bivalved ( Figs 1B, C View Figure 1 , 2 A–C View Figure 2 , 8A, B View Figure 8 ), valves joined and hinged along dorsal margin ( Fig. 17A View Figure 17 ). Dorsal and posterior margins of valves feebly convex, meeting at slightly produced posterio-dorsal angle; anterior and ventral margins rounded ( Figs 1B, C View Figure 1 , 2 A–C View Figure 2 , 8B View Figure 8 ).Exterior of carapace smooth, lacking setae but covered with small pores ( Figs 8A View Figure 8 , 17A, B View Figure 17 , 18 A–D View Figure 18 ). Right and left gut diverticula ( Figs 1B, C View Figure 1 , 2 A–C View Figure 2 ) lying within respective carapace valve, resembling letter “W”; short main branch descending toward ventral margin and bifurcating, with anterior branch shorter than posterior and numerous simple and bifid small branches extending from them in various directions; dorsal, ventral, anterior and posterior small branches terminated with light orange, wide areas at edge of carapace ( Fig. 1B, C View Figure 1 ). Inner surface of carapace valves with cuticular lining or mantle ( Fig. 8 B–F View Figure 8 ). Small, narrow pit on inner surface of anterior part of each valve ( Figs 2A, C View Figure 2 , 8E View Figure 8 ). Anterior pit of carapace infundibuliform, with wide entrance and long, narrowed internal part ( Figs 2D View Figure 2 , 8E View Figure 8 ); cuticle of pit wrinkled, with circular folds, small pores and volcano-shaped papillae ( Fig. 8E, F View Figure 8 ). Body situated within mantle cavity ( Figs 2B View Figure 2 , 8A View Figure 8 ); oval brood chamber for embryos in posterior portion of each valve ( Fig. 2B View Figure 2 ). Cuticular armament of mantle similar to that in S. grygieri (see Kolbasov and Newman 2018). Main cuticular structures of mantle arrayed along its margin: anterior and ventral sides with submarginal underlying folder consisting of dense row of cuticular projections forming fringe or palisade ( Fig. 8C View Figure 8 ); anterior, ventro-posterior and posterior sides of mantle bearing long setae with short setules, these being absent ventro-anteriorly ( Fig. 8 B–D View Figure 8 ).

Body proper consisting of unsegmented head and segmented thorax and abdomen. Head bearing W-shaped prehensile antennules followed by large ventral oral cone formed of mouth parts surrounded by labrum ( Fig. 2B View Figure 2 ). Frontal filament complex ( Fig. 8D View Figure 8 ) originating on mantle rather than body proper, ~380 μm long and trifid, with anterior ramus longest (ca. 350 μm) and densely covered by long, setiform protrusions; ampuliform, short basal ramus (ca. 70 μm) with smooth cuticle; and small, thin posterior ramus (ca. 40 μm).

Thorax consisting of six segments ( Figs 2B View Figure 2 , 9A, B View Figure 9 ), each with pair of biramous natatory thoracopods described in detail below. Dorsal sides of segments ( II–VI) covered with thin setae ( Fig. 9A, B View Figure 9 ). Posterio-ventral angles of sixth thoracic segment formed as small triangular projections or epaulets, their surface covered by rounded plaques ( Fig. 9B View Figure 9 ).

Abdomen U-shaped, five-segmented, including telson ( Figs 2B View Figure 2 , 8A View Figure 8 , 9B View Figure 9 ). First segment with vestigial penis on ventral side ( Figs 2E View Figure 2 , 9B, C View Figure 9 ), an unpaired process - 140-190 μm long, its distal part bearing ctenoid scales ( Fig. 9C View Figure 9 ). Second segment trapezoid, bigger than either third or fourth. Last body segment (telson) cylindrical, ca. 300 μm long, its posterio-ventral margin bearing fringe of ctenoid scales and pair of conspicuous telson spines ( Figs 2B View Figure 2 , 9B, D View Figure 9 ) approximately 190 μm long with row of nine or ten sharp denticles along their dorsal margins. Furcal rami unsegmented ( Figs 2B, F View Figure 2 , 9B View Figure 9 ), approximately 410-560 μm long, thus approximately 2.5-2.9 times longer than telson spines; ventral margin with one medial, one subdistal and two distal setae, rarely with long setules ( Figs 2F View Figure 2 , 9B, E, G View Figure 9 ); proximal half of ventral margin armed with large, sharp denticles and ctenoid scales ( Figs 2F View Figure 2 , 9D, F, H View Figure 9 ). Inner subdorsal margin of each ramus with row of eight long natatory setae with long setules ( Figs 2F View Figure 2 , 9F, H View Figure 9 ); row of dense ctenoid scales along inner side of dorsal margin ( Fig. 9 F–H View Figure 9 ).

Extendable, prehensile antennules subchelate, folded into W-shape, consisting of six segments with complex of intrinsic and extrinsic flexor and extensor muscles ( Figs 2B View Figure 2 , 3A, B View Figure 3 , 10A View Figure 10 ). First segment rectangular, narrowing somewhat distally, without setae. Second segment irregularly rectangular, with dense, thin omniserrate setae along postaxial/ventral margin ( Figs 3A, B View Figure 3 , 10A, C View Figure 10 ). Third segment equilaterally triangular, narrowing toward ventral margin; preaxial/dorsal margin curved, densely covered by thin omniserrate setae ( Figs 3A, B View Figure 3 , 10A View Figure 10 ). Fourth segment rectangular, trapezoid (appearing triangular in folded antennules, Fig. 3A, B View Figure 3 ), very narrow, narrowing towards dorsal margin, with two massive and denticulate setae ( ‘spines’) armed with row of dense, conspicuous denticles along anterior edge and, rarely, tiny denticles on posterior edge; these two spines sitting on dorsal projection apex bearing ctenoid scales with sharp denticles ( Figs 3A, B View Figure 3 , 10A, F View Figure 10 ). The two spines form a fork to accept movable claw. Fifth segment conical, forming a palm against which sixth segment can fold in order to grasp host tissue, with 6-9 strong, simple setae along upper margin ( Figs 3A, B View Figure 3 , 10A View Figure 10 ). Sixth segment longer than fifth segment and armed with sensory and grasping structures ( Figs 3A, B View Figure 3 , 10A, D, E, G–I View Figure 10 ). Short proximal sensory process on lower margin at base of sixth segment ( Figs 3A, B View Figure 3 , 10A, G View Figure 10 ), with 3 terminal setae, middle one setulated and longest, and 1 thick, blunt sub-basal seta (at least this seta probably an aesthetasc). Curved claw on distal end of sixth segment apparently with muscles attached ( Figs 3A, B View Figure 3 , 10A, D, E View Figure 10 ); concave margin of claw serrate, with sharp tiny denticles in middle part ( Fig. 10D, E View Figure 10 ); three small setae at base of claw, two lateral on inner and outer surfaces and one on anterior dorsal margin ( Figs 3A, B View Figure 3 , 10D, H View Figure 10 ). Relaxed claw sheathed by grooved claw guard ( Figs 3A, B View Figure 3 , 10D, E, H, I View Figure 10 ), latter approximately 110 μm long, with wide flange on inner side, thin, membranous, apical ctenoid hood ( Fig. 10I View Figure 10 ) and four small terminal setae including two longer and one tiny subapical ( Fig. 10E View Figure 10 ) and 1 tiny apical seta ( Fig. 10I View Figure 10 ). Cuticle on sides of antennular segments bearing dense small ctenoid scales ( Fig. 10B View Figure 10 ).

Oral cone prominent, approximately 600-650 μm long; distal end often protruding outside carapace ( Figs 1B, D View Figure 1 , 2 A–C View Figure 2 , 11A View Figure 11 ); formed by cone-shaped labrum surrounding piercing mouth parts ( Fig. 11A View Figure 11 ). Posterior margins of labrum free, unfused ( Fig. 11A View Figure 11 ). Tuft of long, thin simple setae in middle of anterior face of labrum; dense, small ctenoid scales on external cuticle ( Fig. 11A View Figure 11 ). Mandibles in form of lanceolate stylets, approximately 350 μm long ( Figs 3D View Figure 3 , 11B View Figure 11 ); cutting edge of each bearing approximately 80-90 sharp, complex teeth with four tips (quadrifid), length of teeth increasing towards middle part of blade, with row of small setae paralleling them ( Fig. 11D View Figure 11 ); neck of mandible lacking denticles or teeth but bearing small simple setae; distal part with row of 16-20 curved teeth on posterior margin ( Figs 3D View Figure 3 , 11B View Figure 11 ). Maxillules consisting of a wide basal half and narrow distal half ( Figs 3E View Figure 3 , 11B, C View Figure 11 ); cutting edge bearing numerous denticles with serrate margin and cuticular setiform projections, these denticles being massive in proximal part and thin and elongate in middle and distal parts ( Fig. 11B, C, E View Figure 11 ); tip with thin, curved setiform projections (probably setae, Fig. 11F View Figure 11 ). Maxillae ( Figs 3F View Figure 3 , 11C View Figure 11 ) thin, fused at bases, with row of thin, needle-shaped denticles along inner cutting edge at distal end ( Fig. 11G View Figure 11 ); tips not distinctly bifid, not harpoon-shaped, with apical projection and adjacent tiny process (probably seta, Fig. 11G View Figure 11 ). Unpaired process or medial languette (fused paragnaths?) originating from between paired mouth parts, with sharp tip and two rows of denticles on anterior margin ( Fig. 3C View Figure 3 ).

All thoracopods natatory and biramous ( Figs 4 View Figure 4 , 12 View Figure 12 ). Seminal receptacles found in lateral proximal parts of coxae of thoracopods II–V ( Fig. 4 B–E View Figure 4 ), consisting of ampuliform sacs with proximal parts converging but external opening(s) not observed; thoracopods II with four seminal receptacles, thoracopods III and IV each with three and thoracopod V with one. Thoracopodal setation summarized in Table 1 View Table . First thoracopod ( Fig. 4A View Figure 4 ) slightly separated from others, with elongate protopod comprised of coxa and basis and two-segmented exopod and endopod; margins of basis with tufts of short setae; segments of exopod with ctenoid scales and small denticles, inner margin of basal segment lined with dense thin, small setae; seven long, plumose setae situated at distal end of second segment; basal segment of endopod bearing three long, plumose setae, margins being lined with dense thin, small setae; distal segment with three terminal plumose setae. Thoracopods II-V with three-segmented endopods and two-segmented exopods ( Figs 4 B–E View Figure 4 , 12 A–E View Figure 12 ). Coxae of thoracopods II and III ( Figs 4B, C View Figure 4 , 12B, C View Figure 12 ) with large, distal seta in position “1” (see Table 1 View Table for further explanation) and row of plumose setae along inner edge (position “9”); these setae absent on coxae of thoracopods IV and V ( Fig. 4D, E View Figure 4 ). Number of setae on rami of thoracopods II and III much more numerous than on thoracopods IV and V. Protopod of thoracopod VI ( Figs 4F View Figure 4 , 12F View Figure 12 ) narrow; coxa and basis without setae; both rami two-segmented with long, plumose terminal setae on distal segments; two tufts of thin, small setae on basal segment of endopod and distal segment of exopod. Surface of all thoracopods bearing conspicuous ctenoid scales ( Fig. 12 View Figure 12 ).

Male ( Figs 1D View Figure 1 , 5 View Figure 5 - 7 View Figure 7 , 13 View Figure 13 - 16 View Figure 16 ): Carapace bivalved, ellipsoidal, up to 1.5 mm long and 0.9 mm high, with slightly produced posterio-dorsal tip ( Figs 5A, B View Figure 5 , 13A View Figure 13 ). Dorsal margin almost straight; anterior, ventral and posterior margins rounded. Exterior of carapace smooth, lacking setae but covered with small pores ( Figs 13A View Figure 13 , 17E, F View Figure 17 , 18 E–H View Figure 18 ). Conspicuous deep pit with curved lumen opening on inner surface of anterior part of each valve ( Fig. 5A, B View Figure 5 ). Gut diverticulum of simplified W-shape in comparison to female ( Figs 1D View Figure 1 , 5A, B View Figure 5 ), with 4 short lateral branches extending from anterior, posterior and ventral parts and terminated with light orange, widened areas at edge of carapace. Lobed testis within each carapace valve along lower part of gut diverticulum ( Fig. 5A View Figure 5 ). Cuticular armament of mantle is similar to that of female ( Fig. 13 C–E View Figure 13 ). Edge of mantle forming thin marginal fold adjacent to margin of carapace and consisting of dense, tiny cuticular projections ( Figs 13E View Figure 13 , 15A View Figure 15 ). Anterior, ventral and posterior sides with submarginal underlying folder consisting of dense row of cuticular projections forming fringe or palisade, these projections longer in posterior side ( Fig. 13 C–E View Figure 13 ); anterior, ventro-posterior and posterior sides of mantle bearing setae with short setules ( Fig. 13C, E View Figure 13 ).

Frontal filament long, trifid, more complex or less reduced than in female, with well-developed anterior and posterior rami covered by long, setiform cuticular projections ( Figs 5C View Figure 5 , 12B, F View Figure 12 ). Anterior ramus thicker and shorter than posterior, approximately 200-250 μm long; medial (basal) ramus short (50-80 μm), ampulliform, with smooth cuticle; posterior ramus longest, approximately 470 μm.

Body of male resembling that of female ( Figs 5A View Figure 5 , 13B View Figure 13 ): head bearing similar W-shaped antennules and well-developed oral cone; trunk consisting of 6 thoracic and 5 abdominal segments ( Figs 5A View Figure 5 , 13B View Figure 13 , 14B View Figure 14 ); telson spines of same proportions and morphology ( Figs 5F View Figure 5 , 14E View Figure 14 ). Furcal rami resembling these of female in many details ( Fig. 14 E–H View Figure 14 ) but differ in having fewer long natatory setae on inner subdorsal margin (six instead of eight, Fig. 5F View Figure 5 ). Unlike in females, epaulets of sixth thoracic segment more strongly developed ( Fig. 14A View Figure 14 ).

Condition of penis considerably different between male and female, tergite of penis-bearing first abdominal segment with conspicuous pair of long (approximately 100 μm), posteriorly directed pleural processes with four sharp terminal extensions that are absent in females ( Figs 5D, E View Figure 5 , 14B View Figure 14 ). Penis complex, approximately 600 μm long, ~ 4 times longer than supporting segment, and consisting of three parts: basal, medial and distal ( Figs 5D View Figure 5 , 14B, C View Figure 14 ). Basal shaft cylindrical, approximately 160 μm long. Medial part swollen, ~ 136 μm long, with unpaired thin process ~ 110 μm long extending from anterior side, tip of process ( Fig. 5D View Figure 5 ) covered by thin layer of epicuticle. Distal part consisting of two rami originating from medial part and narrowing toward tips ( Figs 5D View Figure 5 , 14B, C View Figure 14 ). Cuticular setiform projections 10-20 μm long with apical pore (not setae) present along anterior margin of each ramus ( Figs 5D View Figure 5 , 14B, C View Figure 14 ). Tip of each ramus terminating in pair of these projections ( Fig. 14C View Figure 14 ).

Antennules of male resembling those of female ( Figs 6A, B View Figure 6 , 15 View Figure 15 ) but relatively thinner and longer with respect to body size. Second and third segments with dense, thin setae in same positions as in female. Two massive spines of fourth segment armed with row of conspicuous denticles along both anterior and posterior edges ( Fig. 15A View Figure 15 ). Fifth segment with 4-6 rather than 6-9 setae on anterior margin ( Figs 6A, B View Figure 6 , 15B View Figure 15 ). Sensory and grasping structures of sixth segment of same morphology as in females, but ctenoid scales denser in lateral surfaces of segment ( Figs 6B View Figure 6 , 15C, D View Figure 15 ).

Oral cone and mouth parts similar to those of female ( Figs 6 C–G View Figure 6 , 16 View Figure 16 ), consisting of labrum ( Figs 6G View Figure 6 , 16 A–C View Figure 16 ) enclosing an unpaired medial languette ( Fig. 6D View Figure 6 ) and paired mouth parts, mandibles ( Figs 6E View Figure 6 , 16C, D View Figure 16 ), maxillules ( Figs 6F View Figure 6 , 16C View Figure 16 ) and maxillae ( Figs 6G View Figure 6 , 16C, E View Figure 16 ); tips of maxillules bifid, not harpoon-shaped, apical projection and adjacent process slightly larger than in females ( Figs 6G View Figure 6 , 16E View Figure 16 ). Thoracopodal setation of male (Table 1 View Table , Fig. 7 View Figure 7 ) similar to that of female ( Fig. 4 View Figure 4 ) but showing some differences (only thoracopod VI have same setation); distal segment of exopod of thoracopod I with eight rather than seven setae ( Fig. 7A View Figure 7 ), coxae of thoracopods II and III and bases of thoracopods II–IV have fewer setae along inner margins ( Fig. 7 B–D View Figure 7 ).

Lattice organs.

( Figs 17 View Figure 17 , 18 View Figure 18 ): both sexes with five pairs of trough-like slits along hinge line of carapace (lattice organs: lo1-5, Figs 17 View Figure 17 , 18 View Figure 18 ), situated co-linearly in two groups: anterior pairs 1-2 and posterior pairs 3-5. Those of both female and male are of similar morphology and arrangement and are therefore described together.

Lattice organs straight, each trough containing one short, modified seta (so-called crest) with terminal pore at free distal end ( Figs 17D View Figure 17 , 18B View Figure 18 ), terminal pore maybe hidden by debris, shrinkage or trough. Normally, each trough has oblique and rounded ends; distal part of crest lies at rounded end ( Figs 17C, D View Figure 17 , 18 B–D View Figure 18 ). Cuticle of crests smooth, not perforated by small pores. Anterior lattice organs situated just posterior to point of divergence of carapace valves ( Fig. 17A, E View Figure 17 ). Lo1 15 μm long in female ( Fig. 17B, C View Figure 17 ) and 10-11 μm long in male ( Fig. 17F, G View Figure 17 ), with posterior terminal pore, located 5-6 μm from hinge line ( Fig. 17B, F View Figure 17 ). Lo2 100 μm behind first pair in female ( Fig. 17B View Figure 17 ) and 80 μm behind in male ( Fig. 17F View Figure 17 ), 16 μm long in female ( Fig. 17D View Figure 17 ) and 10 μm long in male ( Fig. 17H View Figure 17 ), with anterior terminal pore, located 9-10 μm from hinge line ( Fig. 17B, D View Figure 17 ). Posterior lattice organs situated somewhat anterior to point of divergence of carapace valves, near their apices ( Figs 17A, E View Figure 17 , 18A, E View Figure 18 ), 530-550 μm behind anterior organs in mature female ( Fig. 17A View Figure 17 ), 370-380 μm behind in male ( Fig. 17E View Figure 17 ). Lo3 14-15 μm long in female ( Fig. 18B View Figure 18 ) and 12 μm long in male ( Fig. 18F View Figure 18 ), with anterior terminal pore, located 5-6 μm from hinge line. Lo4 25-28 μm behind lo3 in female and 40-45 μm behind in male ( Fig. 18A, E View Figure 18 ), 17-18 μm long in female ( Fig. 18C View Figure 18 ) and 13-14 μm long in male ( Fig. 18G View Figure 18 ), with posterior terminal pore, located 7-8 μm from hinge line ( Fig. 18A View Figure 18 ). Lo5 45-50 μm behind lo4 in female and 40 μm behind in male ( Fig. 18A, E View Figure 18 ), 17 μm long in female ( Fig. 18D View Figure 18 ) and 14 μm long in male ( Fig. 18H View Figure 18 ), with posterior terminal pore, located 10-15 μm from hinge line.

Comparison.

Having both sexes of S. arabesque available makes it possible to compare this species with all other described species of Synagoga . The main characters used for comparison are given in Table 2 View Table . Owing to a lack of detailed description, no meaningful comparison with the juvenile “McKenzie’s larva" from the eastern Indian Ocean (cf. Grygier 1988) can be made. Only one species, S. millipalus represented by a single male, found in the Pacific Ocean off Okinawa, Japan. It differs in having fewer setae on the fifth antennular segment (three instead of four-six) and on the inner side of the furcal ramus (three instead of six), and also relatively longer telson spines ( Grygier and Ohtsuka 1995). Only a single species, S. normani (based on a female), is known from the western Indian Ocean ( Grygier 1983a). It has fewer setae on the fifth antennular segment (five instead of 6-9) and on the inner side of the furcal ramus (five or six instead of eight), and more setae on the second exopodal segment of thoracopod I (nine instead of seven). Four species inhabit the Atlantic and adjacent seas, these are S. mira , S. bisetosa , S. paucisetosa and S. grygieri ( Norman 1888; Grygier 1983a, 1990a; Kolbasov and Newman 2018). The new species differs from S. mira ( Norman 1888; Grygier 1983a) by having smooth, unscalloped edges of the gut diverticula, fewer setae on the fifth antennular segment (4-9 instead of 15), the second exopodal segment of thoracopod I (seven(eight) instead of 18) and the inner side of the furcal ramus (eight(six) instead of 14). It can be distinguished from S. bisetosa ( Grygier 1990a) by having fewer setae on the fifth antennular segment (four-nine instead of ten), the second exopodal segment of thoracopod I (seven(eight) instead of ten) and the inner side of the furcal ramus (eight(six) instead of 13). The new species differs from S. paucisetosa ( Grygier 1990a) in having more setae on the fifth antennular segment (four-nine instead of three) and the inner side of the furcal ramus (eight(six) instead of three); it also has relatively shorter telson spines. Finally, it can be distinguished from S. grygieri ( Kolbasov and Newman 2018) by fewer setae on the fifth antennular segment of males (four to six instead of eight) and more setae on the inner side of the furcal ramus of females (eight instead of six); it also has relatively shorter fifth antennular segment and telson spines.