Wellstenvalia wellsi sp. nov.

(Figs. 8–19)

urn:lsid:zoobank.org:act: B64386E5-AFDD-4283-86C7-02B5D7B0E7EF

Type locality. Off San Pablo Bay, Baja California Sur (Eastern Tropical Pacific), Mexico; Talud XV cruise, sampling station 24 (27.11806°N, 114.6008°W); depth, 1039 m; organic carbon content, 3.26%; organic matter content, 5.60%; sand 35.53%; clay, 7.95%; silt, 56.52 %.

Other localities. Off Todos Santos/ El Pescadero, Baja California Sur (Eastern Tropical Pacific), Mexico; Talud XV cruise, sampling station 5D (23.295°N, 110.3642°W); depth, 665 m; organic carbon content, 5.83%; organic matter content, 10.03%; sand 11.04%; clay, 5.99%; silt, 82.96 %.

Off La Bocana, Baja California Sur (Eastern Tropical Pacific), Mexico; Talud XV cruise, sampling station 20 (26.54278°N, 113.93889°W); depth, 479 m; organic carbon content, 3.18%; organic matter content, 5.47%; sand 47.08%; clay, 7.75%; silt, 45.16 %.

San Isidro Basin, off west coast of Baja California (Eastern Tropical Pacific), Mexico; Talud XVIB cruise, sampling station 21 (30.92472°N, 116.8267°W); depth, 2037 m; organic carbon content, 2.21%; organic matter content, 3.81%; sand, 1.08%; clay, 12.54%; silt, 86.38 %.

Guaymas Basin, between San Pedro Nolasco Island and Tortuga Island, Gulf of California, Mexico; Talud X cruise, sampling station 15 (27.7°N, 111.6333°W); depth, 1570 m; organic carbon content, 4.48%; organic matter content, 8.37%; sand, 4.49%; clay, 11.96%; silt, 84 %.

Guaymas Basin, off Santa Inés Bay, Gulf of California, Mexico; Talud X cruise, sampling station17 (27.16444°N, 111.7842°W); depth, 1332 m; organic carbon content, 4.76%; organic matter content, 8.19%; sand, 3.17%; clay, 10.33%; silt, 88.09 %.

Off Sinaloa State, Gulf of California, Mexico; Talud cruise IV, sampling station 26 (24.93333°N, 109.0692°W); depth, 1235 m; organic carbon content, 4.08 %.

Specimens examined. From the type locality. Adult female holotype preserved in alcohol (EMUCOP-010812- 02), adult male allotype preserved in alcohol (EMUCOP-010812-03), 28 paratypes (two adult females, three adult males, one CII, nine CIII, seven CIV, and six CV) preserved in alcohol (EMUCOP-010812-04), two dissected male paratypes (EMUCOP-010812-05, EMUCOP-010812-06), one dissected female paratype (EMUCOP-010812-07), and one dissected aberrant female paratype (EMUCOP-010812-08); August 1, 2012; coll. S. Gómez.

From other localities. One dissected female paratype (EMUCOP-050812-04) from sampling station 5D (Talud XV cruise; August 5, 2012; coll. S. Gómez) , one CV paratype preserved in alcohol (EMUCOP-020812-06) from sampling station 20 (Talud XV cruise; August 2, 2012; coll. S. Gómez), one female paratype preserved in alcohol (EMUCOP-280514-01) from sampling station 21 ( Talud XVIB cruise; May 28, 2014; coll. S. Gómez) , one dissected male paratype (EMUCOP-110207-03) from sampling station 15 (Talud X cruise; February 11, 2007; coll. S. Gómez), one female paratype preserved in alcohol (EMUCOP-120207-04) from sampling station 17 ( Talud X cruise; February 12, 2007; coll. S. Gómez) , one CIV paratype preserved in alcohol (EMUCOP-260800-01) from sampling station 26 ( Talud IV cruise; August 26, 2000; coll. S. Gómez) .

Two adult males from the type locality, one female from sampling station 21 (Talud XVIB cruise; May 28, 2014; coll. S. Gómez), and one CI from sampling station 15 together with one CIII and one CV from station 17 (Talud X cruise; February 11 and 12, 2007, respectively; coll. S. Gómez) were used for molecular analyses without satisfactory results.

Etymology. The species was named in honour to Prof. J. B. J. Wells for his contribution to the systematics and taxonomy of harpacticoid copepods. It is a noun in the genitive case.

Description of female. Total body length measured from tip of rostrum to posterior margin of caudal rami ranging from 690 µm to 820 µm (mean = 764 µm; n = 5); habitus pyriform, widest at posterior end of cephalothorax, tapering posteriad (Fig. 8A); cephalothorax/body length ratio, 0.32.

Prosome consisting of cephalothorax with fused first pedigerous somite, and second to fourth free pedigerous somites. Cephalothorax about as long as wide, with surface sensilla as shown (Fig. 8A), hyaline fringe broad and smooth. Free pedigerous somites without expansions laterally nor dorsally and without spinular ornamentation; integument smooth, weakly sclerotized; hyaline fringe of second and third pedigerous somites broad and smooth, of fourth pedigerous somite visibly narrower; width of second to fourth pedigerous somites decreasing progressively, with few surface sensilla (Fig. 8A).

Urosome (Figs. 8A, 9A, C) consisting of fifth pedigerous somite (first urosomite), genital double-somite (genital—second urosomite—and third urosomites fused), two free urosomites, and anal somite. Urosomites without expansions laterally nor dorsally; integument weakly sclerotized.

Fifth pedigerous somite visibly narrower than preceding somites; with surface sensilla as shown (Figs. 8A, 9A); without spinular ornamentation; hyaline fringe narrow.

Second and third urosomites completely fused forming genital double-somite, without any trace of division; as long as wide, widest part measured in proximal third close to P6; with few sensilla dorsally (Fig. 8A), laterally (Fig. 9A) and ventrally (Fig. 9C), with short spinular row laterally (Fig. 9A), and with transverse spinular row ventrally (Fig. 9C); posterior hyaline fringe broad and smooth. Genital complex (Fig. 9C) hardly distinguishable; copulatory pores not exposed; paired genital apertures located ventrolaterally and covered by P6.

Fourth urosomite with few sensilla dorsally (Fig. 8A), laterally (Fig. 9A) and ventrally (Fig. 9C); with some lateral spinules (Fig. 9A) and a ventral spinular row (Fig. 9C).

Fifth urosomite without sensilla nor lateral spinules (Figs. 8A, 9A); ventral row of spinules shorter than in preceding somite (Fig. 9C).

Anal somite three times as wide as long (Fig. 8B); with spinules around joint of caudal rami (Figs. 8B, 9A, C); ventrally (Fig. 9C) with spinules along each side of medial cleft and with two pores. Anal operculum rather straight, flanked by one sensillum on each side, posterior margin with transverse row of small spinules (Figs. 8B, 9A).

Caudal rami elongate, about five times as long as wide (Figs. 8A, B, 9A, C) and nearly four times as long as anal somite; each ramus with one inner and one ventral pore, the former in proximal third of ramus, the latter in distal third (Fig. 9C); with small spinules at base of setae I and II, and III (Fig. 9A–D); with seven elements (Figs. 8B, 9B, D); seta I minute, ventral to seta II, both arising laterally on distal third, the latter reaching slightly beyond posterior margin of ramus; seta III subdistal, arising laterally, slightly longer than seta II; seta IV arising at outer distal corner, without fracture plane, visibly slenderer than and about half as long as seta V, the latter rat-like, with fracture plane, both with outer pinnae (Fig. 9E–F); seta VI issuing at inner distal corner; dorsal seta VII triarticulate at base, situated subdistally close to inner margin.

Rostrum (Fig. 10A) trapezoidal, not fused to cephalothorax, reaching distal margin of second antennulary segment, strongly bifid, with two subdistal sensilla and with a proximal dorsal pore.

Antennule (Fig. 10A) eight-segmented; all segments smooth, except for spinular row on first segment, the latter without pore and with outer distal corner produced into blunt process. All setae smooth except for pinnate seta on first, second, and last segments; second segment with two, third segment with one seta with fracture plane; sixth segment with two, seventh segment with one articulated seta. Armature formula: 1(1); 2(9); 3(8); 4(5 + (1 + ae)), 5(2); 6(4); 7(4); 8(3 + acro). Acrothek consisting of two setae and one slender aesthetasc fused basally.

Antenna (Fig. 10B). Coxa short, with some outer spinules. Allobasis as long as free endopodal segment, with small outer spinules proximally, with proximal and medial longitudinal row of inner spinules, with one pinnate abexopodal seta arising midway inner margin. Free endopodal segment elongate; inner margin with two sets of proximal and medial spinules, with two outer subdistal spinular rows; armature composed of two lateral spines and two accompanying slender setae, distally with one inner apical spine, three apical geniculate setae and one slender element, and one outer distal pinnate element fused basally to slender seta. Exopod three-segmented; first segment longest, about five times as long as wide, with lateral and apical spinules as shown, with one bipinnate long seta; second segment shortest, without spinular ornamentation, with one long bipinnate seta; third segment slightly shorter than first segment, with one medial and one subdistal row of spinules, with one proximal bipinnate seta and three bare elements distally none of which seems to be fused basally.

Mandible (Fig. 11A–C). Coxa relatively short. Gnathobase wide; ventral distal corner produced into small sharp semi-hyaline process; with two strong and several smaller bicuspidate teeth, some spinules, and one bipinnate seta accompanied by strong element. Basis with wide base, tapering distally, with some medial and some subdistal spinules close to outer margin, with three subdistal outer setae. Exopod (Fig. 11C) arising from short pedestal, elongate, tapering distally; about three times as long as wide, and 0.4 times as long as basis; with two outer, two inner, and two apical slender setae, the latter fused basally. Endopod (Fig. 11B) recurved, twisted over exopod; with three lateral setae, and five distal elements (two slender setae and two strong elements, and longest element fused to endopod and with hyaline flange in middle part).

Maxillule (Fig. 11D–E). Arthrite of praecoxa (Fig. 11D) with two surface setae and nine distal elements, one of which a small seta arising next to ventralmost spine, one spinulose dorsal spine, and one lateral spinulose recurved seta. Coxa with arched spinular row and three setae (Fig. 11E). Basis (Fig. 11E) with two endites; proximal endite with four, distal endite with three slender setae. Exopod and endopod not fused neither to each other nor to basis, one-segmented; endopod larger than exopod, with four setae; exopod small, with two setae.

Maxilla (Fig. 11F–G). Large syncoxa seemingly without spinular ornamentation; with three endites; proximal endite smallest, bilobate, each lobe with two setae as shown; middle and distal endites elongate, the latter slightly longer, with three spinulose elements each. Basis (Fig. 11F–G) drawn out into strong spinulose claw, additionally with strong spinulose spine and two slender setae. Endopod (Fig. 11G) small, 1.5 times as long as wide, with six slender setae (one arising basally, two medially, and three apically).

Maxilliped (Fig. 11H–I) subchelate. Syncoxa rectangular, about 1.5 times as long as wide; with slender inner spinules; with one bare and two spinulose strong elements, of which bare seta and one spinulose element at the same level, the other arising distally from long pedestal (see also Fig.11I). Basis slightly shorter than syncoxa, oval; with slender outer spinules, and with one anterior and one posterior inner spinular row as depicted; with two slender distal setae, one of which visibly longer (see also Fig. 11I). Endopod (see also Fig. 11I) one-segmented, with one claw-like element and one seta.

P1 (Figs. 12A, 14A). Intercoxal sclerite transversely elongate, nearly straight, without surface ornamentation (Fig. 14A). Coxa massive; 1.4 times as long as wide; with small outer spinules, and with longer spinules on distal outer corner and medially close to basis. The latter with inner and outer spine; with small spinules at the base of the former, and with strong spinules at the base of the latter; with strong spinules close to inner proximal corner and with minute spinules between rami. Exopod three-segmented, as long as ENP; EXP2 longest, EXP3 shortest; all segments without outer nor inner acute distal processes; EXP1 with transverse rows of outer spinules medially and subdistally, with additional transverse spinular row medially on proximal third and distally close to EXP2, without inner armature; EXP2 with minute spinules midway outer margin and distally close to EXP3, with inner seta; EXP3 with some minute outer spinules, with two distal setae and two outer spines. Endopod two-segmented; segments without inner nor outer acute distal processes; ENP1 reaching middle of EXP2, 2.8 times as long as wide, and as long as ENP2, with long inner spinules and with longitudinal row of outer spinules, with one inner seta; ENP2 slenderer than ENP1, 4.3 times as long as wide, with one inner distal seta arising at proximal fourth, one inner distal seta, one apical element, and one outer spine.

P2 (Figs. 12B, 14B). Intercoxal sclerite not transversely elongate; trapezoidal; with strong pointed process on distal outer corners; without surface ornamentation (Fig. 14B). Coxa (not shown) as in P3. Basis with outer spine and strong acute inner process, the latter reaching middle of ENP1 and with slender spinules at its base. Exopod three-segmented, reaching slightly beyond ENP2; EXP2 shortest, EXP3 longest; EXP1 and EXP2 with outer acute distal process, with longitudinal row of outer spinules and with inner distal frill, with inner seta, EXP1 without, EXP2 with subdistal outer pore; EXP3 with small outer spinules proximally, with medial pore on distal third, with one inner and two apical setae, and three outer spines. Endopod three-segmented, longer than EXP; ENP1 and ENP2 subequal in length, ENP3 longest; ENP1 and ENP2 with outer acute and inner small process distally, with longitudinal row of small spinules, with small spinules at base of outer process and with inner distal frill, ENP1 with, ENP2 without medial pore, inner element of ENP1 fused to segment forming strong spike, ENP2 with inner seta; ENP3 with longitudinal row of outer spinules and with medial pore subdistally, with one inner seta, two apical elements and one outer spine.

P3 (Figs. 13A, 14C). Intercoxal sclerite not transversely elongate, trapezoidal, wider than in P2; with strong pointed process on distal outer corners, without surface ornamentation (Fig. 14C). Coxa squared, with small spinules close to proximal outer corner and with longer spinules close to inner and outer distal corners, with distal outer pore. Basis with outer seta, with pointed inner process smaller than in P2 and with slender spinules at its base, with minute spinules at the base of ENP. Exopod three-segmented, reaching proximal third of ENP3; EXP2 shortest, EXP3 longest; EXP1 and EXP2 with outer acute distal process, with longitudinal row of outer spinules and with inner distal frill, EXP1 without, EXP2 with outer subdistal pore, both segments with inner seta; EXP3 with small outer spinules proximally, without pore, with three inner setae, two apical elements, and three outer spines. Endopod three-segmented, longer than EXP; ENP1 and ENP2 subequal in length, ENP3 longest; ENP1 and ENP2 with outer acute and small inner process distally, with longitudinal row of small spinules, with small spinules at base of outer process and with inner distal frill, ENP1 with, ENP2 without medial pore, inner element of ENP1 a strong spine, ENP2 with inner seta; ENP3 with longitudinal row of outer spinules and medial pore subdistally, with three inner setae of which distalmost thicker and spinulose, with two apical elements and one outer spine.

P4 (Figs. 13B, 14D). Intercoxal sclerite not transversely elongate, trapezoidal, smaller than in P3, with strong pointed process on distal outer corners, without surface ornamentation (Fig. 14D). Coxa squared, ornamented as in P3 except for lack of inner spinular ornamentation, with distal outer pore. Basis as in P3, but inner process smaller. Exopod three-segmented, 1.3 times as long as ENP; EXP1 and EXP2 subequal in length, EXP3 slightly longer; EXP1 and EXP2 with outer distal process less developed than in P3, with longitudinal row of outer spinules and with inner distal frill, EXP1 without, EXP2 with outer subdistal pore, both segments with inner seta; EXP3 with small outer spinules proximally, with medial pore subdistally, with three inner setae of which medial element visibly thicker and with inner margin strongly serrate, two apical elements, and three outer spines. Endopod threesegmented, shorter than EXP; ENP1 and ENP3 subequal in length, ENP2 shortest; ENP1 and ENP2 with outer acute and small inner process distally, with outer longitudinal row of small spinules and with inner distal frill, without pore, ENP1 with inner long element with distal third serrate, ENP2 with inner slender seta; ENP3 with longitudinal row of outer spinules and medial pore subdistally, with two inner setae of which distalmost thicker, with two apical elements and one outer spine.

Setal formula of swimming legs as follows:

P5 (Fig. 9G). Baseoendopod pentagonal, reaching proximal third of EXP; with four setae, of which outermost shortest and set closely to adjacent seta, the latter and medial setae bipinnate, innermost seta thickest and strongly spinulose. Exopod oval, 1.7 times as long as wide, with some outer small spinules and one distal pore, with five setae of which second innermost shortest.

P6 (Fig. 9C) minute flap covering ventrolateral genital aperture, fused to somite, without surface ornamentation, with one slender seta.

Description of male. Total body length measured from tip of rostrum to posterior margin of caudal rami ranging from 541 µm to 700 µm (mean = 645 µm; n = 8); general shape of habitus (Fig. 15A) as in female. Pedigerous somites largely as in female except for narrower male fifth pedigerous somite. Genital somite with dorsal and laterodorsal rows of spinules and with posterior sensilla. Third and fourth urosomites with laterodorsal and ventral spinules, and with posterior sensilla. Fifth urosomite with laterodorsal spinules, with short ventral row of spinules, without sensilla.

Anal somite and caudal rami (Fig. 15A–B), and rostrum (not shown) as in female.

Antennule (Fig. 16A) nine-segmented, haplocer, with geniculation between third and fourth, and sixth and seventh segments; distal corner of first segment less produced than in female, without pore. All segments smooth except for some spinules on first, sixth and seventh segments. All setae smooth except for one pinnate seta on first and second segments; seemingly none seta with fracture plane; eighth segment with two, ninth segment with one articulated seta. Aesthetasc present on third, fifth, and last segments. Armature formula: 1(1); 2(9); 3(8 + ae); 4(2); 5(7 + (1 + ae)), 6(2); 7(1); 8(4); 9(3 + acro). Acrothek consisting of two setae fused basally to aesthetasc.

Antenna, mandible, maxillule, maxilla and maxilliped (not shown) as in female.

P1 (Fig. 17A) largely as in female. Sexual dimorphism expressed in the relatively shorter EXP (ENP 1.3 times as long as EXP), more robust ENP1 (2.3 times as long as wide), longer and slender ENP2 (1.5 times as long as ENP1, and 7.3 times as long as wide), stronger spinules on ENP1 and ENP2, and in the ornamentation of some setae (with setules) and outer spines (spinules coarser).

P2 (Fig. 17B–D). Basis as in female, except for comparatively shorter inner acute process. EXP largely as in female, except for ornamentation of setae and outer spines, and stronger outer spinules. ENP1 as in female, except for stronger outer spinules and for setules on inner spike; ENP2 and ENP3 fused forming a long and slender segment, 5.4 times as long as broad, outer spinules stronger than in female; original division between ENP2 and ENP3 indicated by remains of distal outer and inner processes of former ENP2 (arrowed in Fig. 17C–D).

P3 (Fig. 18A). Basis largely as in female, except for less developed inner process. ENP as in female except for ornamentation of armature complements, for slenderer subdistal inner seta, and for stronger outer spinules. EXP as in female except for stronger outer spinules.

P4 (Fig. 18B) largely as in female except for ornamentation of some armature complements, relative length of outer spinules of EXP, and stronger outer spinules on both rami.

P5 (Figs. 15B, 16B) dimorphic. EXP small, oval, with three elements as depicted. Baseoendopods fused medially forming a continuous plate, each endopodal lobe with one inner long pinnate seta and one outer small element.

P6 (Figs. 15B, 16C) dimorphic. Both legs separated, only one of them functional, the other fused to somite, with one outer seta and one inner spine each.

Variability. The outermost seta of the female P5 endopodal lobe of paratype EMUCOP-050812-04 from sampling station 5D (Talud XV cruise) does not reach the insertion level of innermost seta of EXP. Only a small notch and a well-developed outer process remain marking the original division between ENP2 and ENP3 of the male P2 (Fig. 17C) in some specimens from sampling station 24 (Talud XV cruise), while the original division between these two segments is marked by a less developed outer process and an inner small pointed projection (Fig. 17D) in some males from the same sampling station and from sampling station 15 (Talud X cruise); also, the length of the inner seta on P1 EXP2 (compare Figs. 17B and A) and the length of the inner spike on P2 ENP1 (compare Figs. 17C and D) may vary in length. One female (EMUCOP-010812-08) showed aberrant caudal rami (Fig. 19A), possesses two inner setae on left P1 ENP2, the inner seta on right P2 ENP3 is inserted more proximally (Fig. 19B), possesses one inner spine on the basis of right P2 (Fig. 19C), and the basis of left P2 lacks the inner process.