Leviapseudes segonzaci segonzaci Băcescu, 1981

Esquete, P. & Cunha, M. R., 2017, The Apseudomorpha (Crustacea: Tanaidacea) of the Gulf of Cadiz and Horseshoe Continental Rise (NE Atlantic): A taxonomic review with new records, species, and ecological data, Zootaxa 4276 (1), pp. 61-95 : 73-81

Leviapseudes segonzaci segonzaci Băcescu, 1981

( Figs 7–12 )

Leviapseudes segonzaci Băcescu, 1981: 37 –42, figs. 2–3; 1984: 32 (key).

Remarks. The material from the Horseshoe Continental Rise has been illustrated and described in order to complement the original description by Băcescu (1981).

Material examined. Horseshoe Continental Rise—Mud volcanoes. M. Ivanov MV: St. M86-5_329, 4492 m, 3 ♀♀, 3 neuters; St. M86-5_348, 4497 m, 1 ♀; St. M86-5_388, 4485 m, 4 specimens; St. M86-5_407, 4507 m, 1 neuter (DBUA0002010.01–04). Tiamat MV: St. M86-5_339, 4551 m, 1 specimen (DBUA0002010.05). Abzu MV: St. M86-5_349, 4560 m, 1 ♂; St. M86-5_369, 4550 m, 1 ♀ with oostegites, 3 neuters (DBUA0002010.06–07).

Horseshoe Abyssal Plain—Reference samples. Site 2: St. M86-5_366, 4864 m, 1 specimen (DBUA0002010.08).

Additional material: 2 ♀♀ allotypes ( GANMNH 530 /30699), cruise Biogas III, station DS42, Bay of Biscay, 47°32’01’’N, 9°35’06’’W, 4104 m depth ; 1 ♂ paratype ( GANMNH 521 /30700), cruise Biogas III, station DS79, bay of Biscay, 46°30’04’’N, 10°27’01’’W, 4715 m depth ; 16 specimens (3 ♀♀, 4♂♂, 10 neuters) (MNHN-IU- 2014-12475), cruise INCAL, station DS13, 0 8.06.1976, NW Bay of Biscay, 46°2' 59.9''N; 10°18'0.0''W.

Description of female with oostegites. Body ( Figure 7 A, B) length 16.5 mm, 9.3 times as long as broad. Cephalothorax including rostrum as long as pereonites 1–2 and half of pereonite 3. Rostrum long, reaching beyond half of antennule first article. Anterolateral and lateral processes well developed. Pereon, all pereonites with hyposphenia. Pereonite 1 the shortest, 2.5 times as broad as long, without lateral processes. Pereonites 2–6 with anterolateral processes and a pair of anterodorsal rounded tubercles, all with hyposphenia. Pleon ( Figure 7 A–C), pleonite 1 1.2 times as long as following pleonites, pleonites 2–5 similar in length; all pleonites with triangular epimera, ventrally each with anterior small process bearing a minute seta and a medial large process bearing one anterior and one posterior small setae. Pleotelson ( Figures 7 A–D) as long as pleonites 3–5 and half of pleonite 4, with lateral setae.

Antennule ( Figure 7 E) peduncle article 1 4.6 times as long as broad, inner margin bearing multiple small simple setae and outer margin bearing multiple penicillate setae; article 2 0.3 times as long as article 1, bearing multiple anterolateral penicillate setae; article 3 0.6 times as long as article 2, bearing one distal seta. Flagellum common article naked; inner flagellum of three segments, distal segment bearing two terminal setae; outer flagellum of 15 segments, segment 13 bearing one aesthetasc, terminal segment bearing three terminal setae.

Antenna ( Figure 7 F) peduncle article 1 0.9 times as long as broad, distally with inner rounded process, smooth, bearing seta; article 2 3.0 times as long as first, with two setae on inner margin; squama with one subdistal and two terminal setae; article 3 about as long as broad, inner margin with distal seta; article 4 as long as article 2, inner margin with one medial seta and one subdistal penicillate seta, outer margin with subdistal penicillate seta; article 5 about as long as article 4, inner margin with subdistal seta, outer margin with four subdistal penicillate setae; flagellum of seven segments, each bearing a pair of distal small setae, segments 1 and 3 bearing also one long, outer distal seta, segment 7 bearing multiple distal setae.

Mouthparts. Labrum ( Figure 8 A) bilobed, concave, with medial triangular process, lobes with setules. Left mandible ( Figure 8 B) molar with no denticles or setule, incisor with four denticles (not illustrated); setal row consisting of four multifurcate setae; lacinia mobilis with seven denticles; mandibular palp first article 1.5 times as long as broad, bearing one long and two shorter setae, second article, 3.0 times as long as broad with row of 13 pinnate spines, third article with row of eight pinnate spines and two terminal simple setae. Right mandible ( Figure 8 C) as left mandible, but with no lacinia mobilis and row of setae consisting of 7–8 multifurcate spines. Labium ( Figure 8 D) with marginal setules, palp with one terminal stout, circumplumose seta. Maxillule outer lobe ( Figure 8 F) with ten terminal spines and two subdistal setae on outer margin, both margins with setules; inner lobe ( Figure 8 E) with five terminal spines, inner margin with a protuberance bearing setules; palp ( Figure 8 G) with eight setae. Maxilla ( Figure 8 H) outer lobe of movable endite with two outer and four inner plumose setae; inner lobe of movable endite with seven simple setae; outer lobe of fixed endite with two simple, one circumplumose and eight multifurcate setae; inner lobe of fixed endite with a row of distally widening setae arising from a peduncle in front of four plumose and two simple setae. Outer margins of maxilla with spiniform processes.

Maxilliped basis naked; palp ( Figure 8 I) article 1 with one distal seta on outer margin; article 2 inner margin with row of 13 pinnate and six simple setae, outer distal margin with three setae, longer than remaining articles; article 3 with three setae on inner margin; article 4 with seven terminal setae, two of them shorter than length of article, rest longer than articles 3–4. Endite ( Figure 8 J) with three coupling hooks (not figured), inner margin with row of six plumose spines, distal margin with setules, ten bifurcate setae and one subdistal, fan shaped spine. Epignath ( Figure 8 K) with one circumplumose seta.

Cheliped ( Figure 9 A) basis 4.1 times as long as broad, with one short proximal and one long medial ventral setae, and small dorsoproximal spine. Merus with two dorsodistal setae and tuft of ventrodistal setae. Carpus 6.6 times as long as broad, 1.3 times as long as basis, with one medial and three distal setae on dorsal margin and six setae on ventral margin. Propodus about as long as basis, with two dorsodistal and one inner setae near dactylus insertion. Fixed finger with three ventral setae, cutting edge with spinules and row of five small setae. Dactylus longer than fixed finger, with two proximal and two medial setae. Exopod biarticulate, proximal article 3.0 times as long as broad, distal article polygonal, about as long as broad bearing four plumose setae.

Pereopod 1 ( Figure 9 B) coxa naked; basis 3.5 times as long as wide, naked. Ischium with one ventral and one long dorsodistal seta. Merus 0.8 times as long as basis, with medial seta, a subdistal row of four dorso-marginal setae, a dorsodistal tuft of setae, three subdistal ventral setae, one ventrodistal spine, and two short distal setae. Carpus 0.4 times as long as merus, dorsal margin with a row of six setae, and dorsodistal spine, ventral margin with four setae and two spines. Propodus about as long as carpus, ventral margin with eight spines, dorsal margin with four setae and two spines. Dactylus and unguis combined as long as propodus. Exopod biarticulate, proximal article 3.0 times as long as broad, distal article polygonal, about as long as broad bearing plumose setae.

Pereopod 2 ( Figure 9 C) coxa naked; basis 5.1 times as long as broad, with dorsal penicillate and simple seta, small mid-ventral seta, and ventrodistal seta. Ischium with ventrodistal seta. Merus about half length of basis, with five ventral and one dorsodistal seta. Carpus 1.2 times as long as merus, with seven setae on ventral margin, six setae on dorsal margin, and two shorter, mesial, subdistal setae. Propodus as long as carpus, with six setae on dorsal margin, ventral margin with eight long setae and seven short, slender spines. Dactylus and unguis together 0.8 times as long as propodus. Dactylus with two medial setules on each margin, and one ventrodistal setule near unguis insertion. Unguis 0.6 times length of dactylus.

Pereopod 3 ( Figure 9 D) coxa naked; basis 4.0 times as long as broad, with penicillate seta. Ischium naked. Merus 0.3 times as long as basis, with two ventrodistal setae. Carpus 1.7 times as long as merus, ventral margin bearing two sets of one long and one short setae, distal margin with three long and two short setae. Propodus about as long as merus, ventral margin with three spines and four setae, distal margin with two spines and one seta. Dactylus and unguis together 1.2 times as long as propodus, with one dorsomedial and one ventrodistal setule. Unguis about half length of dactylus.

Pereopod 4 ( Figure 9 E) coxa ( Figure 9 F) with anterior triangular protuberance and seta; basis 4.2 times as long as broad, naked. Ischium naked. Merus 0.4 times as long as basis, with one ventrodistal and dorsodistal seta. Carpus 1.5 times as long as merus, with two ventromedial and eight distal slender spines. Propodus with a dorsal penicillate seta and eight distal simple setae, four of them twice or more as long as others. Dactylus and unguis together 0.9 times as long as propodus. Dactylus with dorsal and ventrodistal setules. Unguis 0.5 times as long as dactylus, with six serrations.

Pereopod 5 ( Figure 10 A) coxa naked; basis 0.3 as long as broad, with one dorsal and two ventral penicillate setae. Ischium with ventral seta. Merus 0.3 times as long as basis, with a pair of ventrodistal setae. Carpus 1.6 times as long as merus, with ventral simple seta and two ventrodistal slender spines. Propodus 3.6 times as long as carpus, dorsal margin with medial penicillate seta, dorsodistal corner with one long spine and one seta, ventral margin with medial seta followed by two slender spines, a row of four small spines between them, and two mesial setules. Dactylus as long as propodus, with two dorsal setules. Unguis lost.

Pereopod 6 ( Figure 10 B) coxa naked; basis 4.3 times as long as broad, with two dorsal penicillate setae. Ischium with two ventral setae. Merus 0.3 times as long as basis, with ventral seta. Carpus 1.4 times as long as merus, with dorsodistal short seta, ventral margin with subdistal seta and distal spine. Propodus 0.7 times as long as carpus, dorsodistal corner with two long spines and two short pinnate spines, ventral margin with two long spines and row of short pinnate spines. Dactylus with two dorsal setules. Unguis lost.

Uropods ( Figure 10 C) protopod 2.5 times as long as broad, bearing four distal setae. Exopod of six segments segment 3 with terminal seta, segment 6 with three terminal setae, endopod of 19 segments, some with setae, some with pair of penicillate setae.

Distinctions of subadult male (Bay of Biscay and HCR). Body ( Figure 11 A) length 2.7 mm. Pleonites with marked lateral epimera.

Antennule ( Figure 11 B) Peduncle article 1 5.6 times as long as broad, 2.3 times as long as article 2, inner margin bearing multiple small simple setae and outer margin bearing multiple penicillate setae and one simple seta; article 2 inner margin with two simple setae, outer distal corner with simple and penicillate setae; article 3 0.6 times as long as article 2, with two distal setae. Flagellum common article naked; inner flagellum of three segments, second segment 2.0 times as long as first, with distal penicillate seta, terminal segment 0.7 times as long as second, with two simple and one penicillate terminal setae; outer flagellum multi-segmented, proximal segments broader than long, distal segments longer than broad, segment 20 with one aesthetasc, distal segment bearing few simple and one penicillate, setae.

Mouthparts. Labium ( Figure 11 C) bilobed, convex, with triangular medial process, covered by setules. Mandibles ( Figure 11 D, E) incisor and lacinia mobilis with multiple cusps.

Pereopod 4 ( Figure 11 F) unguis with fewer serrations than in female.

Pleopods present ( Figure 11 G). Basal article 4.0 times as long as broad, naked. Endopod longer than exopod, with subproximal plumose seta on inner margin, and 11 plumose setae on distal margin. Exopod biarticulate, proximal article naked, 0.5 times as long as distal article, distal article bearing proximal plumose seta on outer margin and eight plumose setae on distal margin.

Distinctions of adult male from Bay of Biscay. Antennule ( Figure 12 A) inner flagellum all segments except distalmost with four aesthetascs.

Pereopod 4 unguis without serrations.

Uropods ( Figure 12 B) protopod with seven setae on inner margin, 1–2 setae on outer margin, and four distal setae. Exopod with six segments. Endopod with 17–19 segments.

Remarks. The sub-specific nomen for this species was applicable following the description of Leviapseudes segonzaci gasconicus Băcescu, 1984 . Both taxa are recognisable by the lack of apophyses on the ventral margin of the cheliped and pereopod 1 basis, three-segmented antennule inner flagellum, long rostrum, pereopod 1 coxa annular and narrow, inter alia ( Băcescu 1984). The subadult males of L. segonzaci segonzaci from the Bay of Biscay and HCR show significant differences from the adult males described and illustrated by Băcescu (1981). These are more consistent with early developmental stages: the antennular outer flagellum has only one aesthetascs, the uropod protopod has fewer setae and the uropod inner ramus has fewer segments. More remarkably, the unguis of pereopod 4 has no serrations. Băcescu (1981: Figure 3 I) illustrated and described the male “pereopod V” that, according to the terminology used here, would correspond to pereopod 4. But, the illustration matches pereopod 5 (that is, pereopod VI under Bacescu’s terminology), as observed in the specimens from MNHN.

Distribution and ecology. This is a deep-sea species, previously found in the Northwest Bay of Biscay at depths of 4104–4715 m ( Băcescu 1981, 1985). In the HCR, L. segonzaci was found in deep, active MVs (Abzu, Tiamat, M. Ivanov) from 4485 to 4560 m depth, and in the Horseshoe Abyssal Plain at 4864 m depth, extending its known bathymetric distribution. In all MVs, the sediment was composed of mud breccia covered by hemipelagic sediments.

Figures

FIGURE 3. Atlantapseudes curvatus sp. nov. Female paratype DBUA 0002002.01. A, labrum. B, left mandible. C, detail of left mandible. D, detail of right mandible. E, right mandible palp. F, right mandible molar. G, labium. H, maxillule endites. I, maxillule palp. J, maxilla. K, maxilliped palp. L, maxilliped endite. M, epignath.

FIGURE 7. Leviapseudes segonzaci. Female DBUA 0002010.01 a. A, habitus (dorsal view). B, habitus (lateral view). C, detail of pleonite 1 (lateral view). D, detail of pleotelson and uropod (lateral view). E, antennule. F, antenna (lateral view).

FIGURE 8. Leviapseudes segonzaci. Female DBUA 0002010.01 a. A, labrum. B, left mandible. C, incisor and setal row of right mandible. D, labium. E, maxillule inner endite. F; maxillule outer endite. G, maxillule palp. H, maxilla. I, maxilliped palp. J, maxilliped endite. K, epignath.

FIGURE 9. Leviapseudes segonzaci. Female DBUA 0002010.01 a. A, cheliped. B, pereopod 1. C, pereopod 2. D, pereopod 3. E, pereopod 4.

FIGURE 10. Leviapseudes segonzaci. Female DBUA 0002010.01 a. A, pereopod 5. B, pereopod 6. C, uropod.

FIGURE 11. Leviapseudes segonzaci. Male DBUA 0002010.06. A, habitus (lateral view). B, antennule. C, labrum. D, left mandible. E, right mandible. F, pereopod 4. G, pleopod.

FIGURE 12. Leviapseudes segonzaci. Male DBUA 0002010.06. A, antennule. B, uropod.