Stellamblyops doryphorus, Wittmann, 2024

Wittmann, Karl J., 2024, The Mysidae (Crustacea, Mysida) of the ANDEEP I-III expeditions to the Antarctic deep sea with the description of twelve new species, establishment of four new genera and with world-wide keys to the species of Erythropinae and Mysidellinae, European Journal of Taxonomy 940, pp. 1-180 : 96-102

Stellamblyops doryphorus sp. nov.

urn:lsid:zoobank.org:act:D6415EFD-FF66-4C08-8041-910A2B7AC5F6

Figs 50–53

Diagnosis

Based on subadult females only. All features matching generic diagnosis. Rostrum triangular, short, not reaching beyond proximal half of basal segment of antennular trunk. Eye rudiments elongate tearshaped with finger-like distal process extending beyond median segment of antennular trunk. Eyes disto-laterally positioned, dorsoventrally weakly flattened, near basis 1.3–1.5 times as wide as thick; basis inside with bulbous, well-delimited corneal rudiment containing numerous reduced ommatidia not reaching surface. Antennular trunk without ventral carina. Antennal sympod with three teeth near insertion of scale. Antennal scale extending far beyond antennular trunk (tip of scale unknown). Clypeus with strong median process extending to second segment of antennular trunk or beyond. Rostral margin of labrum triangular with blunt tip. Female pleopods 3–4 rod-like, with residual differentiation of pseudobranchial lobe. Uropods without spine. Telson elongate linguiform, waisted, with minimum width at ⅓ of length from terminus. Lateral margins with spines along distal ⅔; spines increasing in length distally. Mid-terminal notch with four small laminae (toothlets) flanked by three pairs of spines, also larger than disto-lateral spines. Telson with total of ≈ 40 spines and four laminae, no setae.

Etymology

The species name is the transliterated Ancient Greek adjective ‘δορυφόρος’ (‘spear-bearing’) with Latinized masculine ending, related to the large rostral process of the clypeus.

Material examined

Holotype SOUTHERN OCEAN • 1 ♀ subad. (BL = 8.1 mm, on slides); eastern Weddell Abyssal Plain , S of Maud Rise and E of Sanae Canyon, ANDEEP-III station 059-5; 67°29.74ʹ S, 00°01.93ʹ W to 67°29.61ʹ S, 00°02.19ʹ W; depth 4655– 4655 m; 14 Feb. 2005; EBS supranet; ZMH 64690 .

Paratypes SOUTHERN OCEAN • 1 juv. (BL = 4.8 mm); northern Weddell Abyssal Plain , ANDEEP-II station 135-4; 65°00.06ʹ S, 43°01.19ʹ W to 64°59.97ʹ S, 43°00.91ʹ W; depth 4677.6–4678.2 m; 11 Mar. 2002; EBS supranet; ZMH 64692 • 1 ♀ subad. (tailfan broken, estimated BL ≈ 8.6 mm); Drake Passage , NW of Elephant Island, ANDEEP-I station 041-3; 59°22.24ʹ S, 60°04.06ʹ W to 59°22.40ʹ S, 60°03.99ʹ W; depth 2375– 2372 m; 26 Jan. 2002; EBS epinet; ZMH 64691 .

Type locality and distribution

The type locality is ANDEEP III station 059-5: eastern Weddell Abyssal Plain, S of Maud Rise and E of Sanae Canyon, 67°29.74ʹ S, 00°01.93ʹ W to 67°29.61ʹ S, 00°02.19ʹ W, depth 4655 m. This species was also recorded in the deep waters of the Drake Passage. Total ranges 59° S – 67° S, 00°– 60° W, depth 2372–4678 m.

Description

Holotype (♀)

All features as in specific diagnosis. Body length 8.1 mm. Rostrum contributes 2% to BL, carapace without rostrum 31%, thorax 34%, pleon 44% and telson 20%. Rostrum right-angled triangular with acute tip ( Fig. 51B ). Disto-lateral edges of carapace with small, tooth-like projection ( Fig. 51B ). Most of carapace surface ornamented by minute depressions as in Fig. 50D , no pores detected. Eye rudiments without pigment; long rostral process extending to distal segment of antennular trunk ( Fig. 50A–B ); no pores, no organ of Bellonci. Rostral process of clypeus ( Fig. 50B ) spit-like in dorsal view, blade-like with distally converging margins in lateral view.

ANTENNULA ( Fig. 50A–B ). Trunk dorsoventrally compressed with distally decreasing thickness ( Fig. 50A ), basal segment 1.4 times as wide as thick, terminal segment 2.4 times. Terminal segment of left and right trunks with artificial transverse fold (not present in paratypes) feigning an additional segmentation in Fig. 50A–B . Basal segment with disto-lateral, setose lobe extending beyond proximal half of median segment. No antennular bursa detected. Segmental border between median and terminal segment oblique in dorsal view, to a minor degree also in lateral view; distal portion of median segment dorsally overlapping part of terminal segment. Terminal segment with four barbed setae on disto-median lobe, no tooth. Basal portions of both flagella with about same width.

ANTENNA ( Fig. 51A ). Sympod 2-segmented, caudally in addition with large end sac of antennal gland. Sympod with a strong tooth (dashed line in Fig. 51A ) dorsally above basis of scale, another strong tooth (solid line) proximally accompanied by smaller tooth ventrally near disto-lateral edge of sympod. Peduncle 3-segmented, its basal segment contributes 14%, median segment 49% and terminal segment 37% to total length. Basal segment bare, median and terminal segments each with a few barbed setae near distal margin.

PRIMARY MOUTHPARTS ( Figs 51C–E , 53A–B ). Labrum and labium normal ( Fig. 53A–B ). Mandibular palp ( Fig. 51C ) with basal segment contributing 6%, median segment 62% and terminal segment 32% to total palp length. Palp not hispid, its basal segment without setae. Length of median segment four times maximum width, its mesial margin convex, lateral margin sigmoid, densely setose along mesial and lateral margins. Terminal segment seven times as long as broad and 0.6 times as long as median segment. Terminal segment comparatively sparsely setose along lateral margins, though with dense series of short microserrated setae on tip. Right mandible ( Fig. 51D ) with four large teeth on pars incisiva and with only two large teeth, each serrated by small secondary teeth, on digitus mobilis. Pars centralis modified, with distally serrated, broad tooth-like spines proximally followed by continuous series of nine smooth, subtriangular spines decreasing in size proximally. Processus molaris also modified, with series of 13 teeth, median teeth longest. Left mandible ( Fig. 51E ) almost normal, pars incisiva with three large teeth, digitus mobilis with five large, blunt, distal processes (one of which below drawing plane in Fig. 51E ). Pars centralis with seven slender spines bearing stiff bristles. Processus molaris with strong grinding lamellae not ending in teeth. Processus molaris of left mandible with bundle of stiff bristles on proximal edge. Right mandible with such a bundle on lateral margin of processus molaris.

GUT ( Fig. 52 ). Foregut, not considering its artificial deformation ( Fig. 52A ), most similar to that of Scolamblyops muehlenhardtae sp. nov. ( Fig. 47 ). Posterior part of lateralia (accidentally shifted caudally) in Stellamblyops doryphorus sp. nov. with complex of at least eight toothed spines of various sizes ( Fig. 52D ; potential additional spines poorly differentiated due to superposition in optical path. Dissected foregut with almost empty storage volume, midgut completely filled with finely masticated material. Anal lobe distinct, weakly cuticularized.

MAXILLULA ( Fig. 51F–G ). Distal segment with eleven strong spines on transverse terminal margin; most distal spine smooth, remaining spines unilaterally serrated, armed with acute to blunt micro-teeth (examples in Fig. 51G ). This segment subterminally with three setae bearing long stiff barbs. Lateral margin of basal segment furnished with longitudinal, comparatively long series of densely set, long hairs. Endite terminally with two large, distally spiny (due to stiff bristles) setae flanked by several less strong, shorter setae.

MAXILLA ( Fig. 51H ). Sympod with three mesial, only distally strongly setose lobes. Additional mesial bulge short, not clearly classified as lobe. Exopod extends shortly beyond basal segment of palp. Exopod with numerous plumose setae all along lateral margin; tip with two large plumose setae almost twice as long as largest lateral setae, mesial margin bare. Palp with two subequal segments. Apical segment 1.6 times as long as maximum width. Basal segment less wide, bearing two barbed, basally thick setae (below drawing plane, visualized by dashed lines in Fig. 51H ). Obliquely transverse distal margin of apical segment densely setose, lateral margin with only four barbed setae, mesial margin bare, no spines.

THORACOPODS ( Fig. 53C–F ). Basal plates of thoracic exopods 1–2 and 8 slender, disto-lateral edge with tooth-like projection ( Fig. 53E ); remaining exopods broken. Flagellum of exopod 1 with ten segments, exopods 2 and 8 each with eleven. Basis of thoracic endopod 1 with setose endite (mostly below drawing plane in Fig. 53C ), remaining segments without endite. Endopod 1 strongly setose along mesial margin; merus and carpus without setae on lateral margin; smooth apical nail ( Fig. 53D ) slightly longer than propodus. Epipod 1 linguiform, only about as long as carpus of endopod 1, no seta. Endopod 2 ( Fig. 53E ) with six segments including basal segment, the latter fused with sympod; ischium and dactylus strongly setose, remaining segments sparsely setose; dactylus not reflexed, nail smooth, slender (tip of nail broken, Fig. 53F ); no endite. Thoracic endopods 3–8 broken.

PLEON AND TAIL FAN ( Fig. 53G–I ). Pleomeres 1–5 are 0.5, 0.5, 0.5, 0.5 and 0.7 times as long as pleomere 6, respectively; this value 1.7 for telson. Subadult female pleopods 3–4 short, distally widening, with setation as in Fig. 53G ; remaining pleopods broken. Uropods with setose lateral margins, no spines, but tips of all available uropods broken. Statoliths not preserved. Telson ( Fig. 53H ) with total of 40 spines, including 17 spines on each lateral margin, 2×3 large, in part (artificially?) limp spines on transverse terminal margin; no pores and no scales detected. Notch with pair of small paramedian laminae flanked by a pair of even smaller laminae.

Paratypes

Carapace length about one third of BL. Antennular trunk clearly 3-segmented, terminal segment without artificial fold in both paratypes (unlike holotype in Fig. 50B ).

Figures

Fig. 50. Stellamblyops doryphorus sp. nov., holotype, subadult female with BL of 8.1 mm (ZMH 64690). A. Cephalon prior to dissection, lateral view. B. Cephalon mounted on slide, ventral view, antennae removed. C. Detail of B, showing right eye. D. Ornamentation of carapace surface. A–C. Objects artificially separated from background.

Fig. 51. Stellamblyops doryphorus sp. nov., holotype, subadult female with BL of 8.1 mm (B–H: ZMH 64690) and paratype, subadult female 8.6 mm (A: ZMH 64691). A. Antenna with antennal gland, ventral view; setae omitted from antennal scale. B. Carapace expanded on slide, dorsal view. C. Mandible with right palpus, caudal view. D–E. Masticatory part of right (D) and left (E) mandibles, caudal view. F. Maxillula, caudal view. G. Details of F, showing two examples of serrated spines. H. Maxilla, caudal view.

Fig. 52. Foregut in Stellamblyops doryphorus sp. nov., holotype, subadult female with BL of 8.1 mm (ZMH 64690). A. Foregut expanded on slide, dorsal view. B–E. Details of A, arrows point to modified spines of foregut. Abbreviations: di = dorsolateral infolding; la = lateralia; mg = midgut; sp = storage space. A. Foregut deformed, large portions of lateralia accidentally shifted caudally; object artificially separated from background.

Fig. 53. Stellamblyops doryphorus sp. nov., holotype, subadult female with BL of 8.1 mm (ZMH 64690). A. Labrum, ventral = aboral view. B. Labium. C. Thoracic endopod 1 with epipod 1, caudal view (exopod broken). D. Detail of C, showing dactylus with nail, setae omitted. E. Thoracopod 2, rostral view. F. Detail of E, showing dactylus with nail (tip broken), setae omitted. G. Right pleopod 3, mesial face. H. Telson, dorsal view. I. Detail of H, showing terminus of telson.

Fig. 47. Foregut in Scolamblyops muehlenhardtae sp. nov., holotype, adult female with BL of 20.1 mm (ZMH 64686). A. Foregut expanded on slide, dorsal view. B–E. Details of A, arrows point to modified spines of foregut. Abbreviations: di = dorsolateral infolding; la = lateralia; mg = midgut; sp = storage space. A. Object artificially separated from background.