Paramblyops petrescui, 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 : 79-85

Paramblyops petrescui sp. nov.

urn:lsid:zoobank.org:act:DEE643B6-6E0C-4B3D-A427-2B5DC2F4A9D2

Figs 41–44

Diagnosis

Based on adult female only. All known features within limits of generic diagnosis. Carapace with bare margins all around, no toothed ‘shoulders’. Rostrum broadly rounded, very short, covering only basal portions of subrostral lobe, which covers only about half ‘length’ of eyes. Eye rudiments separate, dorsoventrally compressed, reduced to roughly subtriangular pads, mesially rounded, disto-laterally with one tooth-like projection, no visual elements, no ocular papilla. Antennal sympod without teeth near disto-lateral edge. Clypeus with short, acutely converging, mid-rostral process, due to small size visible only in ventral view. Mouthparts normal, labrum rostrally rounded. Marsupium formed by three pairs of oostegites. Endopod of uropods with one small spine mesially below statocyst. Telson trapeziform, distally converging, length 5/3 times maximum width; its basal third with bare lateral margins; distal ⅔ of each lateral margin with 16 densely-set spines, distally weakly increasing in size in roughly continuous series. Transverse terminal margin of telson with weak mid-terminal indentation bearing plumose setae between minute spines; indentation flanked by four pairs of large spines, increasing weakly in size from submedian to most lateral position.

Etymology

The species name is a noun with masculine ending in genitive singular, dedicated to Iorgu Petrescu in recognition of his important contributions to the taxonomy of cumaceans.

Material examined

Holotype SOUTHERN OCEAN • 1 ♀ ad. ( BL = 38.7 mm, on slides); NW Weddell Sea, ANDEEP-II station 131-3; 65°19.83ʹ S, 51°31.62ʹ W to 65°19.95ʹ S, 51°31.41ʹ W; depth 3049–3050 m; 5 Mar. 2002; EBS epinet; ZMH 64684 .

Type locality

The type locality is ANDEEP II station 131-3: NW Weddell Sea, 65°19.83ʹ S, 51°31.62ʹ W to 65°19.95ʹ S, 51°31.41ʹ W, depth 3049–3050 m.

Description

Holotype (♀)

All features as in specific diagnosis. Female with BL 38.7 mm, marsupium empty ( Fig. 41A ). Rostrum contributing 1% to BL, carapace 25% (without rostrum), thorax 32%, pleon 55% and telson 12%. Subrostral lobe ( Fig. 41B–C ) dorsally completely covered by densely set, ellipsoidal cuticular structures, representing minute depressions in part (accidentally) filled with external material ( Fig. 41E ). Cuticular depressions of various sizes locally present on part of antennular trunk, antennal peduncle, carapace (arrows in Fig. 41C ), eyes, posterior thoracic sternites, basal plates of thoracic exopods 1–8 and outer face of oostegite 3 ( Fig. 41E–F ).

CARAPACE ( Fig. 42C ). With disto-lateral edges well rounded; its anterior margin with small triangular processes flanking short rostrum. Cervical sulcus distinct, cardial sulcus not established, no pores detected. Posterior margin weakly concave. Carapace leaving one thoracic segment exposed dorsally.

EYE RUDIMENTS ( Figs 41B , 42C ). Proximo-lateral portions of eye rudiments with similar, narrower, less densely set cuticular depressions compared with subrostral process ( Fig. 41F–G ). Eyes with tooth-like projection (when oriented anteriorly) extending at most to median segment of antennular trunk. Eyes without pores, no pigment, no organ of Bellonci.

ANTENNULA ( Figs 41B , 42A ). Basal segment of trunk with disto-lateral setose lobe extending beyond proximal half of median segment. Basal segment dorsally with well-developed antennular bursa and two setose apophyses. Median segment with many setae closely behind its rostral margin, no apophysis. Terminal segment almost as long as combined median and basal segments; disto-median lobe with four barbed setae, no tooth. This segment without female lobe and without callynophore. Basal portion of inner flagellum 0.8 times as wide as in outer flagellum.

ANTENNA ( Fig. 42B ). Sympod 2-segmented, caudally in addition with end sac of antennal gland. Sympod with distally rounded, linguiform lobe positioned ventrally behind antennal scale. Peduncle 3-segmented, its basal segment contributes 18%, median segment 52% and terminal segment 29% to total length. Its basal segment bare, median and terminal segments each with a few barbed setae and several smooth setae close to distal margin, lateral margins without setae. Antennal scale distally broken.

PRIMARY MOUTHPARTS ( Fig. 42D–H ). Labrum and labium normal. Mandibular palp with basal segment contributing 8%, median segment 59%, and terminal segment 33% to total palp length. Palp not hispid, its basal segment without setae. Length of median segment 2.0 times maximum width, mesial and lateral margins convex, setose. Terminal segment 3.6 times as long as broad and 0.5 times as long as median segment. Terminal segment well setose, with dense series of short, microserrated setae on distal ¾ of mesial margin. Right mandible ( Fig. 42G ) with three large teeth on pars incisiva and with six smooth blunt processes (worn teeth?) on well-developed digitus mobilis. Pars centralis modified, with continuous series of 13 tooth-like spines proximally (with respect to mouth field) increasing in length and slenderness; most spines smooth, only five most proximal spines slightly microserrated by stiff bristles. Processus molaris plate-like with stiff bristles along most of its periphery. Left mandible ( Fig. 42F ) less modified, pars incisiva with three large teeth, most proximal broad and bumpy, resembling a mammalian molar tooth. Digitus mobilis also bumpy with three large and two small teeth. Pars centralis with ten slender spines bearing stiff bristles. Processus molaris with strong grinding lamellae and with bundles of stiff bristles on and near proximal edge.

GUT. Foregut ( Fig. 43B–E ) essentially as in Amblyopsoides fenestragothica sp. nov. ( Fig. 34 ). As main differences, modified spines on anterior part of lateralia not serrated ( Fig. 43B–C vs Fig. 34B–C ) and spines on posterior part of lateralia and on dorsolateral infoldings less strongly serrated ( Fig. 43D–E vs Fig. 34D–E ). Storage volume filled to about ⅔ by numerous crustacean remains, unidentified masticated organic material, mineral particles and a few foraminiferans. Midgut full of finely masticated material and large amounts of mineral particles. Anal lobe distinct, weakly cuticularized.

MAXILLULA ( Figs 41D , 42I–J ). Distal segment with 9–10 strong spines on transverse terminal margin; most distal spine smooth, remaining spines unilaterally, bluntly serrated ( Fig. 42J ). This segment subterminally with 3–4 setae bearing long stiff barbs. Field of 16–20 pores laterally (= aborally) from this group of setae (not every pore visualized in Fig. 41D ). Lateral margin of basal segment furnished with longitudinal, comparatively long series of densely set long hairs. Endite terminally with three large, distally spiny (by stiff bristles) setae flanked by several less strong, shorter setae of that kind. Both sides of endite with numerous additional, barbed setae. As also in Dactylamblyops benthophilus sp. nov., most proximal seta of endite long, slender and backward curved.

MAXILLA ( Fig. 43A ). Most similar to that of Amphiakrops brandtae gen. et sp. nov. ( Fig. 60A ). Sympod with three mesial, only distally strongly setose lobes. Exopod extends to distal margin of basal segment of palp. Exopod with numerous plumose setae all along lateral margin; longest seta at tip (accidentally bent backward in Fig. 43A ), mesial margin bare. Palpus with apical segment 1.2 times as long as basal segment. Apical segment 1.8–2.2 times as long as maximum width. Basal segment basally broader, its mesial margin with three densely barbed, basally thick setae. Distal ⅔ of apical segment with well setose margins, proximal third bare except for minute hairs, no spines.

THORAX ( Fig. 43F–I ). Sternite 1 on each side with small, dense field (shaded areas in Fig. 43F ) of slender triangular scales. Group of 4–5 basally thick setae on intersegmental joint between sympod 2 and sternite 2. Basal plates of exopods 1–7 about twice as long as maximum width, three times as long as width in exopod 8. Disto-lateral edge with small tooth-like projection in all basal plates. Flagellum of exopods 1–8 with 18–19, 20–21, 22, 21, 21, 20, 22 and 20 segments, respectively (n = 2, 2, 1, 1, 1, 1, 1, 1). Basis of endopod 1 with setose endite (below drawing plane, visualized as dashed line in right endopod drawn to the left in Fig. 43F ), remaining segments without endite. Endopod 1 densely setose along mesial margin, much less along lateral margin; its smooth apical claw ( Fig. 43G ) almost as long as dactylus. Epipod 1 ( Fig. 43F ) linguiform with narrowly blunt apex, about as long as combined ischium, merus and carpus of endopod 1; no seta. Endopod 2 ( Fig. 43H ) with six segments counted including basal segment, the latter fused with sympod, no endites; dactylus densely setose, remaining segments less setose; dactylus not clearly reflexed, no claw detected in dense jungle of setae. Thoracic endopods 3–8 broken.

MARSUPIUM ( Fig. 43I ). Proximal portion of oostegite 1 with dense brush of setae on inner face. These comparatively long setae microserrated by series of stiff, acute bristles along distal half. Less dense brush of such setae on oostegite 2, even fewer on oostegite 3. Only distal third of oostegite 1 with barbed to plumose setae along its margins. Ventral margin of oostegite 1 all along furnished with setae, proximally with microserrated setae, distally turning into barbed setae and finally into plumose setae in about continuous series. Proximal third of dorsal margin bare, central third densely lined by tiny hairs. Most of dorsal margin bare in oostegites 2–3. These oostegites with ventral and anterior margins plus part of posterior margin bearing dense series of barbed to plumose setae contributing to ventral and caudal ventilation-pervious closure of marsupium. Oostegites 1–2 with smooth cuticle on outer and inner faces, not counting brush of setae proximally on inner face. Only oostegite 3 with cuticular ornamentation ( Fig. 41E–F ) and with many loosely scattered, slender whip setae on outer face.

PLEON AND TAIL FAN ( Figs 41A , 44 ). Pleomeres 1–5 are 0.5, 0.7, 0.6, 0.6 and 0.7 times length of pleomere 6, respectively; this value 1.7 for exopod of uropods, 1.2 for endopod and 1.0 for telson ( Fig. 41A ). Pleopods 1–5 widening from basis up to rudiment of pseudobranchial lobe, followed by a more slender, straight distal portion on top; setation as in Fig. 44A–E . Pleopod length increasing caudally. Scutellum paracaudale triangular with acute tip. Uropods ( Figs 41A , 44F ) all around with setose margins, exopod extends 0.3 times its length beyond endopod and 0.4 times beyond telson. Statoliths composed of fluorite, diameter 0.25–0.26 mm (n = 2). Lateral margins of telson ( Fig. 44G ) weakly sigmoid, almost straight. Telson with total of 43 spines and three plumose setae, no pores, no scales (such as otherwise found in Figs 8G , 14E ). Telson furnished with 2×16 small spines on lateral margins, 2× 4 large spines on terminal margin and three minute spines plus three setae in mid-terminal indentation. Additional specimens needed to judge whether asymmetrical arrangement of setae within indentation ( Fig. 44H ) represents a normal feature.

Figures

Fig. 41. Paramblyops petrescui sp. nov., holotype, adult female with BL of 38.7 mm (ZMH 64684). A. Holotype in toto, lateral view (thoracic endopods 3–8 and most exopods broken). B–C. Cephalon, lateral (B) and dorsal (C) views.D. Pore field laterally (= aborally) beneath setal group on distal segment of maxillula. E. Detail of C, with arrows pointing to cuticle structures at surface of subrostral lobe and of parts of carapace. F. Detail of C, with arrows pointing to smaller cuticle structures at surface of lateral portions of eye and of other parts of carapace compared with that of E. G. Tip of eye rudiment, dorsal view; small arrow points to tangential aspect of surface cuticle structures. Abbreviations: as = antennal sympod; re = right eye; ro = rostrum; rt = right antennular trunk; sr = subrostral lobe. A–C, G. Objects artificially separated from background. E–F. Many cuticle surface depressions (probably accidentally) filled with external material.

Fig. 42. Paramblyops petrescui sp. nov., holotype, adult female with BL of 38.7 mm (ZMH 64684). A. Antennula, dorsal view. B. Antenna with antennal gland, dorsal view; setae of fragment of antennal scale omitted. C. Carapace with subrostral lobe and eyes expanded on slide, dorsal view. D. Labrum, ventral = aboral view. E. Mandible with left palpus, rostral view. F–G. Masticatory part of left (F) and right (G) mandibles, rostral view. H. Labium. I. Maxillula, caudal view. J. Detail of I, showing bluntly serrated spine.

Fig. 43. Paramblyops petrescui sp. nov., holotype, adult female with BL of 38.7 mm (ZMH 64684). A. Maxilla, rostral view. B–E. Modified spines of foregut, from anterior (B), median (C) and posterior (D) parts of lateralia and from dorsolateral infolding (E). F. Thoracopod 1 with epipod 1 (caudal view) and sternites 1, 2 (ventral view); setae omitted from right endopod (drawn to the left). G. Detail of F, showing dactylus with nail, setae omitted. H. Thoracopod 2, caudal view. I. Oostegite 1, inner face.

Fig. 44. Paramblyops petrescui sp. nov., holotype, adult female with BL of 38.7 mm (ZMH 64684). A–E. Pleopods 1–5, lateral = rostral (A, C–E) and mesial = caudal (B) views. F. Uropods, dorsal view, setae omitted. G. Telson, dorsal view. H. Detail of G, showing terminus of telson.

Fig. 34. Foregut in Amblyopsoides fenestragothica sp. nov., holotype, immature male with BL of 16.2 mm (ZMH 64660). 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.

Fig. 60. Amphiakrops brandtae gen. et sp. nov., holotype, adult male with BL of 17.5 mm (A–H, J–K: ZMH 64667) and paratype, adult female 23.8 mm (I: ZMH 64668). A. Maxilla, rostral view, thin dashed lines indicate position of broken setae of exopod. B–E. Modified spines of foregut, from anterior (B), median (C) and posterior (D) parts of lateralia and from dorsolateral infolding (E). F. Male thoracic endopod 1 (exopod broken) with epipod 1 (caudal view) and sternites 1–8 with right penis (ventral view). G–H. Details of F, showing dactylus with nail (G, setae omitted) and setae on sternite 2 (H). I. Female sternites 1–8, ventral view. J. Thoracopod 2, rostral view. K. Detail of J, showing dactylus with nail, setae omitted.

Fig. 8. Dactylamblyops benthophilus sp. nov., paratypes, adult males with BL of 17.0 mm (A–B: ZMH 64674), 20.3 mm (F–I: ZMH 64670) and adult female 21.8 mm (C–E: ZMH 64676). A. Male pleopod 1, rostral = lateral view. B. Male pleopod 3, caudal = mesial view. C. Female pleopod 1, rostral view. D–E. Female pleopods 2 and 5, rostral view, most setae broken. F. Uropods, ventral, setae omitted. G–I. Telson including its ventral (dashed) anal lobe visible through the artificially transparent tissue (G), dorsal view; details showing apical spines (H) and right pore field (I). G, I. Pore diameters and scales of telson not to scale.

Fig. 14. Amblyops arianii sp. nov., holotype, adult female with BL of 25.8 mm (A–C, G: ZMH 64653) and paratype, subadult female 24.2 mm (D–F: ZMH 64655). A–B. Cephalon, dorsal (A) and ventral (B) views. C. Detail of A, showing rostrum and disto-mesial portion of eye rudiments. D. Detail of C, showing part of pore field sublaterally on rostrum in another specimen. E. Scale field close to lateral margin of telson, dorsal view. F. Scales near proximal margin of exopod of maxilla, caudal view. G. Cephalic region, latero-ventral view. Abbreviations: ca = carapace; er = eye rudiment; op = ocular papilla. A–B, G. Objects artificially separated from background.