Willenstenhelia reducta, Gómez, 2020

Gomez, Samuel, 2020, On some new species of Stenheliinae Brady, 1880 (Copepoda, Harpacticoida, Miraciidae) from north-western Mexico, with the proposal of Lonchoeidestenhelia gen. nov., ZooKeys 987, pp. 41-79 : 41

Willenstenhelia reducta sp. nov. Figs 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21

Specimens examined.

One female holotype (ICML-EMUCOP-180119-25) from the type locality and one male allotype (ICML-EMUCOP-180119-26) from stn 4; four (ICML-EMUCOP-180119-31) and one (ICML-EMUCOP-180119-32) female paratypes from the type locality; one female and one male paratype (ICML-EMUCOP-180119-33), one female paratype (ICML-EMUCOP-180119-34), and two female paratypes (ICML-EMUCOP-180119-35) from stn 4; one female and one male paratype (ICML-EMUCOP-180119-36), one female paratype (ICML-EMUCOP-180119-37), and one CIV, one CV, one female and two male paratypes (ICML-EMUCOP-180119-38) from stn 9; one CIII, one CIV, and two female paratypes (ICML-EMUCOP-180119-39) from stn 10; all preserved in alcohol. Two dissected female paratypes (ICML-EMUCOP-180119-27, ICML-EMUCOP-180119-28) mounted onto eight and six slides, respectively, and one dissected male paratype (ICML-EMUCOP-180119-29) mounted onto three slides, all from stn 2; one dissected male paratype (ICML-EMUCOP-180119-30) from stn 4 mounted onto eight slides. 18 Jan. 2019. S. Gómez leg.

Differential diagnosis.

Stenheliinae : Willenstenhelia . Female antennule eight-segmented. Armature formula of P4EXP, 0,1,122. Female P5 baseoendopods not fused medially; endopodal lobe with two setae separated by wide gap, outer seta well-developed, inner seta minute; exopod with five setae, of which innermost as long as two outermost setae, middle seta smallest, inner neighboring seta longest. Male antennule ten-segmented. Male P5EXP discrete, with four elements, of which apical a strong spine, two medial ones small and subequal in length, innermost smallest arising midway inner margin; baseoendopods fused medially forming a continuous plate, each endopodal lobe with one strong spine-like element fused to endopod, both elements set close to each other.

Description.

Female. Total body length measured from tip of rostrum to posterior margin of caudal rami ranging from 445 µm to 510 µm (mean, 477 µm; n, 3; total body length of holotype, 510 µm); habitus (Fig. 12A ) pyriform, widest at posterior end of cephalothorax in dorsal view, tapering posteriad.

Prosome (Fig. 12A ): Consisting of cephalothorax with fused first pedigerous somite, and second to fourth free pedigerous somites, the latter without expansions nor spinular ornamentation; posterior hyaline frill of cephalothorax and pedigerous somites plain, of fourth pedigerous somite visibly narrower; integument smooth, weakly sclerotized.

Urosome (Figs 12A, B , 13A, B ): Consisting of fifth pedigerous somite (first urosomite), genital double-somite (genital second urosomite and third urosomite fused), two free urosomites, and anal somite; urosomites without expansions laterally nor dorsally; integument weakly sclerotized.

First urosomite (fifth pedigerous somite): Visibly narrower than preceding somites in dorsal view (Fig. 12A, B ), without spinular ornamentation (Figs 12A, B , 13A, B ).

Genital double-somite: Ca. 1.5 × as wide as long, widest part at proximal half (Fig. 12A, B ); separated dorsolaterally (Figs 12A, B , 13A ), completely fused ventrally (Fig. 13B ); without spinular ornamentation, with posterior sensilla as depicted.

Fourth urosomite: With short spinular row and pore laterally on each side (Fig. 13A ) and with sensilla as shown.

Fifth urosomite (Fig. 13A ): Without sensilla; spinular ornamentation and pores as in previous somite.

Anal somite (Figs 12A, B , 13A, B ): Twice as long as broad, maximum breadth measured at proximal margin; maximum length measured at the middle from anterior margin of somite to distal margin of anal operculum, with row of dorsolateral spinules close to joint with caudal rami (Figs 12A, B , 13A ), ventrally cleft medially (Fig. 13B ), with one subdistal pore on each side, with spinular row close to joint with caudal rami; anal operculum (Fig. 12A, B ) rounded, with minute spinules along its posterior margin, with one sensilla on each side.

Caudal rami (Figs 12A, B , 13B ): Typically divergent, cylindrical, ca. 2.7 × as long as broad, and 1.4 × as long as anal somite in dorsal view; each ramus with one subdistal lateral pore (Fig. 13A ); with spinules at base of setae I and II (Figs 12B , 13A ), and ventrally (Fig. 13B ); with seven elements; seta I very small, often masked behind spinules, ventral to seta II, the latter long, both arising subdistally on lateral margin; seta III ventral, subdistal, longer than seta II; seta IV and V situated distally, with fracture plane; seta VI issuing at inner distal corner; dorsal seta VII tri-articulate at base, situated subdistally close to inner margin.

Rostrum (Fig. 12A ): Trapezoidal, not fused to cephalothorax, reaching tip of first antennular segment, bifid at tip, without pore, with two subdistal sensilla.

Antennule (Fig. 14A, B ): Eight-segmented; all segments smooth, except for first segment with spinular row. All setae seemingly smooth; second and third segments each with one seta with fracture plane; seventh and eighth segments with two articulated setae each. Armature formula: 1(1); 2(11); 3(8); 4(5+(1+ae)), 5(3); 6(4); 7(4); 8(3+(2 setae fused basally)). Eighth segment seemingly without aesthetasc.

Antenna (Fig. 14C ): Coxa small, with some outer spinules. Allobasis as long as free endopodal segment, inner margin with some proximal spinules, with one (pinnate?) abexopodal seta arising midway on inner margin. Exopod three-segmented, issuing proximally; first and third segments longest, each 3 × as long as wide, second segment shortest and ca. 1.5 × as long as broad; first and second segments with one pinnate seta each, spinular ornamentation of first segment a single spinule, second segment unornamented; third segment with small spinules as shown, with one lateral pinnate element proximally, and three distal setae, of which two fused basally. Free endopodal segment elongate, inner margin with proximal row of small spinules, with medial and subdistal inner fringe; armature consisting of two lateral spines and two accompanying setae, one geniculate inner distal element, three geniculate distal spines (of which innermost shortest) and one slender seta, and one outer distal geniculate seta fused basally to pinnate element.

Mandible (Fig. 15A, B ): With relatively short coxa. Gnathobasis wide; with two strong bicuspidate teeth, several smaller bicuspidate teeth, some spinules, and one strong lanceolate element accompanied by slender seta. Basis elongate, tapering distally, with transverse spinular rows as shown, with three subdistal setae. Exopod arising from short pedestal, one-segmented, elongate, ca. 3.5 × as long as wide, tapering distally; with three lateral and three apical slender setae, none of which fused basally. Endopod recurved, twisted over exopod; with three lateral setae, and five distal elements (one smooth and one long pinnate element, two long setae fused basally and fused to endopod, and one long element fused to endopod and with hyaline flange in middle part).

Maxillule (Fig. 15C ): Arthrite of praecoxa with two surface setae and seven bare distal elements (one of which a slender seta arising next to ventralmost spine), one spinulose dorsal spine, and one lateral spinulose recurved seta. Coxal endite with three setae. Basis with two endites; proximal endite with four, distal endite with three slender setae. Exopod and endopod fused basally, and fused also to basis, each ramus one-segmented; endopod larger than exopod, with four setae; exopod small, with two setae.

Maxilla (Fig. 15D ): Large syncoxa with outer spinules as shown; with three endites; proximal endite smallest, with one slender proximal and two strong distal setae; middle and distal endites elongate, the latter slightly longer, with three elements each as figured. Basis drawn out into strong claw, additionally with strong spine and two slender setae, one of which arising from elongate setophore. Endopod one-segmented, 2 × as long as wide, with six slender setae.

Maxilliped (Fig. 15E ): Non-prehensile. Syncoxa rectangular, ca. 2 × as long as wide; with anterior and posterior spinules as shown; with two proximal elements arising from short pedestals, and one apical element arising from long pedestal. Basis shorter than syncoxa, oval; with inner and outer spinules as depicted, and two slender distal setae subequal in length. Endopod absorbed into basis, with two slender setae.

P1 (Fig. 16A ): Intercoxal sclerite narrow and elongate, without surface ornamentation. Praecoxa triangular, unornamented. Coxa quadrate, with spinular rows as shown. Basis with inner robust and pinnate spine, and outer smaller pinnate spine, with strong spinules at the base of inner spine and between rami. Exopod three-segmented, as long as endopod; first and third segments longest, second segment shortest; all segments without outer nor inner acute distal processes; with spinular ornamentation as shown; first segment without, second segment with inner seta, third segment with four elements. Endopod two-segmented; ENP1 reaching slightly beyond EXP1, ca. 1.5 × as long as wide, and 0.7 × as long as ENP2, with outer and distal spinules as depicted; with one inner long seta; ENP2 longer than ENP1, with outer and distal spinules as shown, with one inner proximal, one inner subdistal, and two apical elements of which outermost a spine.

P2 (Fig. 16B ): Intercoxal sclerite not transversely elongate, trapezoidal, with strong pointed process on distal outer corners, without surface ornamentation. Praecoxa triangular, unornamented. Coxa massive, quadrate, with outer spinules proximally and subdistally, with one pore close to inner distal margin. Basis with outer setiform element with small spinules at its base, and strong acute process between rami and on inner distal corner, the latter with slender spinules proximally. Exopod three-segmented, shorter than endopod, reaching middle of ENP3; spinular ornamentation of segments as shown; EXP1 and EXP2 with inner distal frill, with outer acute distal process, EXP1 without, EXP2 with medial pore and inner seta; EXP3 with processes as shown, with subdistal pore, with one inner and two apical setae, and three outer spines. Endopod three-segmented; ENP1 shortest, ENP2 and ENP3 subequal in length; spinular ornamentation of segments as shown; ENP1 and ENP2 with inner and outer acute processes, ENP1 with one, ENP2 with two inner seta; ENP3 with distal processes as shown, with medial pore, with one inner seta, two apical elements, and one outer distal spine.

P3 (Fig. 17A ): Intercoxal sclerite not transversely elongate, trapezoidal, with strong pointed process on distal outer corners, without surface ornamentation. Coxa as in P2. Basis as in P2, but with somewhat more slender outer seta. Exopod three-segmented, as long as ENP; spinular ornamentation of segments as shown; EXP1 and EXP2 with outer acute distal process, without pores, with inner distal frill, EXP1 without, EXP2 with inner seta; EXP3 with subdistal pore, with two inner setae of which the distal is visibly stronger, two apical elements, and three outer spines. Endopod three-segmented; ENP1 shortest, ENP3 longest; spinular ornamentation of segments as shown; ENP1 with small outer and inner distal processes, with inner seta; ENP2 with well-developed outer and small inner distal process, with inner seta; ENP3 with distal processes as shown, with subdistal pore, with one inner and two apical setae, and one outer apical spine.

P4 (Fig. 17B ): Intercoxal sclerite not transversely elongate, trapezoidal, with strong pointed process on distal outer corners; without surface ornamentation. Praecoxa triangular, unornamented; coxa and basis as in P3 except for comparatively smaller inner distal process of basis. Exopod three-segmented, longer than ENP; spinular ornamentation of segments as shown; EXP1 and EXP2 with outer distal process less developed than in P3, with inner distal frill, EXP1 without, EXP2 with subdistal pore and inner seta; EXP3 with subdistal pore, with one inner seta, two apical elements, and two outer spines. Endopod three-segmented, reaching proximal third of EXP3; ENP1 shortest, ENP3 longest; spinular ornamentation of segments as depicted; ENP1 with small outer distal process, with inner long stiff pinnate element; ENP2 with well-developed outer distal process, without inner armature; ENP3 with distal processes as shown, with subdistal pore, with one inner seta, two apical elements, and one outer apical spine.

Setal formula of swimming legs as follows:

P5 (Fig. 17C ): Baseoendopod transversely elongate; endopodal lobe with two setae, of which outer well-developed, inner minute, both separated by wide gap. Exopod trapezoidal, with some inner proximal spinules; with five setae, of which outermost, medial outer, and innermost setae pinnate and subequal in length, middle seta shortest and slender, medial inner seta bare and longest.

P6 (Figs 12B , 13A, B ): Represented by a minute flap covering ventrolateral genital aperture, fused to somite, without surface ornamentation, with one small seta.

Male. Total body length measured from tip of rostrum to posterior margin of caudal rami ranging from 251 µm to 363 µm (mean, 309 µm; n, 5; total body length of allotype, 363 µm).

Prosome: As in female.

Urosome: Largely as in female except for genital and third urosomites separated, and spinular ornamentation of fourth and fifth urosomites (Figs 18C , 19A, B ).

Caudal rami (Figs 18C , 19A, B ): As in female.

Sexual dimorphism: Expressed in A1, P2ENP, P3, P4, P5, and P6.

Antennule (Fig. 18A, B ): 10-segmented, haplocer. All segments smooth except for first and seventh segment with spinules as shown. All setae seemingly smooth; with one modified spine-like element on seventh segment. Armature formula: 1(1); 2(11); 3(7+ae); 4(1), 5(6+(1+ae)); 6(1); 7(3); 8(2); 9(4);10(3+2 setae fused basally).

Antenna, mandible, maxillule, maxilla, and maxilliped: As in female.

P1: As in female.

P2 (Fig. 20A ): Praecoxa, coxa, basis, and exopod as in female. Endopod sexually dimorphic, two segmented; first segment as in female; second segment with one proximal and one subdistal longitudinal row of spinules separated by medial process indicating division between ENP2 and ENP3 of the female ENP, with two inner elements homologues to the inner elements of the female ENP2, with subdistal pore, with one inner subdistal strong outer element, and one inner apical slender seta, and one apical outer spine-like element.

P3 (Fig. 20B ): Largely as in female, the general shape of the distalmost inner seta of EXP3 the only difference detected: very long, and pinnate element as in the female, but a visibly shorter and plumose seta in the male.

P4 (Fig. 21A ): Largely as in female, the relative length and shape of the inner seta on ENP1, inner seta of EXP2, and outer spine of EXP2 the only differences detected: inner seta of ENP1 very long and stiff in the female, but comparatively shorter, slender and plumose in the male; inner seta on the female EXP2 reaching beyond tip of EXP3 in the female, but visibly shorter in the male; outer spine of EXP2 of normal length not reaching tip of EXP3 in the female, but comparatively longer and reaching beyond tip of EXP3 in the male.

P5 (Figs 19A, B , 21B ): Baseoendopods of both P5 fused forming a continuous plate; each endopodal lobe with short row of spinules close to insertion of exopod, and with one element (the two elements are set very close together) fused to endopodal lobe. Exopod small, discrete; with four elements, of which apical a strong spine, two medial ones small and subequal in length, innermost smallest arising midway inner margin.

P6 (Fig. 19A, B ): Asymmetrical; each leg with three setae, of which medial longest, outer shortest.

Variability.

No variability was observed in the inspected material.

Etymology.

The specific epithet from the Latin reducta , reduced, in reference to the reduced inner seta on the female P5 baseoendopod, and to the reduced armature complement on the female and male P5BENP. It is an adjective in the nominative singular; gender feminine.

Type locality.

Mexico, Sinaloa State: Urías estuary, stn 2: 23.1587°N, 106.3326°W, depth 1.8 m, organic carbon content 3.99%, organic matter content 6.86%, sand 80.42%, clay 8.29%, silt 11.28%.

Other localities.

Mexico, Sinaloa State: Urías estuary, stn 4: 23.1840°N, 106.3579°W, depth 0.7 m, organic carbon content 1.13%, organic matter content 1.94%, sand 82.44%, clay 8.27%, silt 9.29%, stn 9: 23.1904°N, 106.4121°W, depth 5.4 m, organic carbon content 1.41%, organic matter content 2.43%, sand 64.81%, clay 8.09%, silt 27.11%, stn 10: 23.1815°N, 106.4214°W, depth 6.0 m, organic carbon content 1.20%, organic matter content 2.07%, sand 69.12%, clay 7.91%, silt 22.97%.

Figures

Figure 12. Willenstenhelia reducta sp. nov., female A habitus, dorsal B urosome, dorsal. Scale bars: 200 µm (A); 50 µm (B).

Figure 13. Willenstenhelia reducta sp. nov., female A urosome, lateral B urosome, ventral. Scale bars: 50 µm (A, B).

Figure 14. Willenstenhelia reducta sp. nov., female A antennule without armature B antennule with armature C antenna. Scale bars: 50 µm (A-C).

Figure 15. Willenstenhelia reducta sp. nov., female A mandibular coxa and basis B another mandibular basis, exopod and endopod C maxillule D maxilla E maxilliped. Scale bars: 50 µm (A-C); 25 µm (D, E).

Figure 16. Willenstenhelia reducta sp. nov., female A P 1, anterior B P 2, anterior. Scale bars: 50 µm (A, B).

Figure 17. Willenstenhelia reducta sp. nov., female A P 3, anterior B P 4, anterior C P 5, anterior. Scale bars: 50 µm (A-C).

Figure 18. Willenstenhelia reducta sp. nov., male A antennule without armature B antennule with armature C urosome, dorsal. Scale bars: 50 µm (A, B); 100 µm (C).

Figure 19. Willenstenhelia reducta sp. nov., male A urosome, lateral B urosome, ventral. Scale bars: 100 µm (A, B).

Figure 20. Willenstenhelia reducta sp. nov., male A P 2, anterior B P 3, anterior. Scale bars: 50 µm (A, B).

Figure 21. Willenstenhelia reducta sp. nov., male A P 4, anterior B P 5, anterior. Scale bars: 50 µm (A, B).