Leiocanthus quinquenudus, Cepeda & Sánchez & Sørensen & Landers, 2022

Cepeda, Diego, Sánchez, Nuria, Sørensen, Martin V. & Landers, Stephen C., 2022, Leiocanthus quinquenudus sp. nov. and L. satanicus sp. nov., two new species of pycnophyid Kinorhyncha (Allomalorhagida: Pycnophyidae) from the Gulf of Mexico, Zootaxa 5093 (3), pp. 315-336 : 319-323

publication ID	https://doi.org/ 10.11646/zootaxa.5093.3.3
publication LSID	lsid:zoobank.org:pub:0A4DE130-B44E-4526-8752-DFB6E60DDFA5
DOI	https://doi.org/10.5281/zenodo.5910865
persistent identifier	https://treatment.plazi.org/id/CA784956-977A-FF96-FF54-0709F864FEEE
treatment provided by	Plazi
scientific name	Leiocanthus quinquenudus
status	sp. nov.

Treatment

Leiocanthus quinquenudus View in CoL sp. nov.

Zoobank code: urn:lsid:zoobank.org:act:72EC0153-2637-449D-A08D-BDB8E997C413

( Figs. 2–4 View FIGURE 2 View FIGURE 3 View FIGURE 4 )

Synonymy

Leiocanthus sp. 2 —in Landers et al. 2020: p. 496, Table III.

Leiocanthus sp. 2 —in Hoffman et al. 2021: p.377, Table 4 View TABLE 4 .

Material examined. Holotype, adult female, collected on March 17, 2018 at St. 13-2018 in the northern Gulf of Mexico continental shelf: 30.1463° N, 88.2583° W ( Table 1 View TABLE 1 ) at 18 m depth; mounted in Fluoromount G ®, deposited at the NHMD under catalogue number: NHMD-915196 GoogleMaps . Paratypes, three adult males and two adult females, all of them collected at different stations than the holotype ( Table 1 View TABLE 1 ), mounted in Fluoromount G ® and stored at NHMD under catalogue numbers: NHMD-915197–915201. One additional female mounted for SEM and deposited in the personal reference collection of SCL .

Diagnosis. Leiocanthus with middorsal cuticular elevations on segments 2–6. Unpaired paradorsal setae on segments 2, 4, 6 and 8; paired setae in laterodorsal position on segments 3, 5, 7 and 9, in lateroventral position on segments 2, 4, 6, 8 and 10 (two pairs in the latter), ventrolateral position on segment 5 and ventromedial position on segments 3–4 and 6–9 longitudinally aligned. Anterior margin of segment 1 tergal plate irregularly denticulated, posteriorly followed by a transverse band of minute, circular perforations. Males with sexually dimorphic ventromedial tubes on segment 2, females with ventrolateral setae instead. Lateral terminal spines present.

Etymology. The specific epithet of the species derives from the Latin quinque (meaning five) and nudus (meaning naked), referring to the unique lack of ventromedial setae on segment 5 of the species.

Description. See Table 2 for measurements and dimensions and Table 3 View TABLE 3 for summary of seta, spine, tube, glandular cell outlet and sensory spot positions.

Head. Only one specimen, which was mounted for LM, had the head everted, hence exact details on the morphology and arrangement of the mouth cone and introvert structures cannot be completely provided. Internal rings of mouth cone not observed. Ring 00 of mouth cone with nine, equally sized outer oral styles, each one composed of a single, flexible unit, wider at the base, bearing a fringed basal sheath, progressively tapering towards a distally pointed tip. Outer oral styles located anterior to each introvert sector, except in the middorsal sector 6 where a style is missing.

Introvert with six transverse rings of scalids and 10 longitudinal sectors defined by the position of the primary spinoscalids. Ring 01 of introvert with 10 primary spinoscalids; primary spinoscalids larger than scalids in remaining rings; each primary spinoscalid composed of a basal, rectangular, wide sheath and a distal, elongated, flexible, laterally compressed, distally rounded end-piece. Basal sheath of primary spinoscalids superficially fringed, bearing a rhomboid cuticular piece superficially fringed near the articulation point with the end-piece. Rings 02–06 of introvert with several regular-sized scalids, also composed of a basal, rectangular, superficially fringed, wide sheath and a distal, elongated, flexible, distally rounded end-piece. Exact arrangement of regular-sized scalids cannot be provided due to the collapsed condition of the only available introvert when mounted for LM. A ring of 14 trichoscalids posterior to the scalid rings, arranged as two in the odd-numbered sectors (except sector 1 with a single trichoscalid) and one in the even-numbered sectors of the introvert.

Neck. Neck with four dorsal and two ventral sclerotized placids ( Fig. 2A–B View FIGURE 2 ). Mesial dorsal placids subquadrangular, conspicuously higher than lateral ones ( Fig. 2B View FIGURE 2 ), ca. 26–32 μm wide at the base; lateral dorsal placids rectangular ( Fig. 2B View FIGURE 2 ), ca. 20–23 μm wide at the base. Mesial and lateral dorsal placids with saw-toothed anterior margin and longitudinal striation on the surface ( Fig. 2B View FIGURE 2 ). Ventral placids even more rectangular, longitudinally compressed, with straight laterodistal margins ( Fig. 2A View FIGURE 2 ), ca. 17–30 μm wide at the base.

Trunk. Trunk rectangular, stout, triangular in cross-section, composed of 11 segments ( Figs. 2A–B View FIGURE 2 , 3A View FIGURE 3 , 4A View FIGURE 4 ). Segment 1 with one tergal, two episternal and one midsternal plates; remaining segments with one tergal and two sternal plates ( Figs. 2A–D View FIGURE 2 , 3A–J View FIGURE 3 , 4A–H View FIGURE 4 ). Maximum sternal width at segment 5 ( Table 2), almost constant in width throughout the trunk until segment 8, and progressively tapering along the last trunk segments ( Figs. 2A–B View FIGURE 2 , 3A View FIGURE 3 , 4A View FIGURE 4 ). Sternal cuticular plates relatively narrow in relation to trunk length (MSW–5:TL interval ratio = 20.6–28.2%) ( Table 2), giving the animal a relatively slender appearance ( Figs. 2A–B View FIGURE 2 , 3A View FIGURE 3 , 4A View FIGURE 4 ). Segments 1–10 with rounded to slightly oval glandular cell outlets, each consisting of a single, round opening located in subdorsal and ventromedial positions, except ventral outlets of segment 1 shifting its position to ventrolateral ( Figs. 2A–D View FIGURE 2 , 3 View FIGURE 3 B-J); intraspecific variation of this character was found in a single specimen that showed two round openings in some glandular outlets. Segments 2–10 with paired, small, not always conspicuous cuticular ridges in ventrolateral position, with adjacent, minute glandular cell outlets ( Fig. 2A, C View FIGURE 2 ). Minute, acicular cuticular hairs widely covering the cuticular surface of segments 1–10, except in ventromedial position, denser at the tergosternal junctions ( Fig. 4B–G View FIGURE 4 ). Muscular scars in laterodorsal and ventrolateral positions throughout segments 1–10 as rounded to oval, hairless cuticular areas, poorly conspicuous, even less visible on the sternal plates ( Figs. 2A–C View FIGURE 2 , 3B–J View FIGURE 3 ). Pachycycli and ball-and-socket joints well-developed and thick on segments 2–10 ( Figs. 2A–D View FIGURE 2 , 3A, F, H View FIGURE 3 ). Apodemes absent. Posterior margin of segments straight, with primary pectinate fringes showing weakly serrated free flaps ( Figs. 2A–D View FIGURE 2 , 3B–J View FIGURE 3 , 4B–G View FIGURE 4 ). Secondary pectinate fringes as three (dorsal) to two (ventral) transverse rows, finely serrated, becoming slightly wavier at the sternal plates, extending posteriorly in triangular extensions in ventrolateral position ( Figs. 2A–D View FIGURE 2 , 3C, H, J View FIGURE 3 ).

Segment 1 without middorsal process or elevation. Anterolateral margins of tergal plate as low, distally rounded protuberances ( Figs. 2 View FIGURE 2 A-B, 3A, 4A). Anterior margin of tergal plate irregularly denticulated, posteriorly followed by a transverse band of minute, circular perforations ( Fig. 2B View FIGURE 2 ). Anterior margin of sternal plates with several semicircular ridges and a few, scattered, minute, circular depressions ( Fig. 2A View FIGURE 2 ). Midsternal plate slightly wider at the posterior edge ( Figs. 2A View FIGURE 2 , 3A View FIGURE 3 ). Sensory spots in subdorsal (two pairs), laterodorsal (one pair), ventrolateral (two pairs longitudinally arranged) and ventromedial (one pair) positions ( Figs. 2A–B View FIGURE 2 , 3B View FIGURE 3 ). Sensory spots on this and remaining segments rounded to oval, with a single posterior pore surrounded by several rings of micropapillae.

Segment 2 with middorsal elevation not projecting beyond the posterior margin of segment, with conspicuous paradorsal, butterfly-like atria of sensory spots ( Figs. 2B View FIGURE 2 , 3D View FIGURE 3 ). Unpaired seta in paradorsal position, and paired setae in lateroventral and ventrolateral positions, the latter only in females (sexually dimorphic) ( Figs. 2A–C View FIGURE 2 , 3C–E View FIGURE 3 , 4B View FIGURE 4 ). Sensory spots in paradorsal, subdorsal, laterodorsal and ventromedial positions ( Figs. 2A–C View FIGURE 2 , 3C–E View FIGURE 3 , 4B View FIGURE 4 ). Males with conspicuously large, sexually dimorphic tubes in ventromedial position ( Figs. 2A View FIGURE 2 , 3E View FIGURE 3 ).

Segment 3 with middorsal elevation as on the preceding segment ( Figs. 2B View FIGURE 2 , 3D View FIGURE 3 ). Paired setae in laterodorsal and ventromedial positions ( Figs. 2A–B View FIGURE 2 , 3D View FIGURE 3 , 4B View FIGURE 4 ). Sensory spots in paradorsal, subdorsal, laterodorsal and ventromedial positions, the latter more lateral than the ventromedial setae ( Figs. 2A–B View FIGURE 2 , 3D View FIGURE 3 , 4B View FIGURE 4 ).

Segment 4 with middorsal elevation as on the preceding segments ( Fig. 2B View FIGURE 2 ). Unpaired seta in paradorsal position, and paired setae in lateroventral and ventromedial positions, the latter longitudinally aligned with those of segment 3 ( Figs. 2A–B View FIGURE 2 , 4F View FIGURE 4 ). Sensory spots in paradorsal, subdorsal, laterodorsal and ventromedial positions ( Figs. 2A–B View FIGURE 2 , 4F View FIGURE 4 ).

Segment 5 with middorsal elevation as on the preceding segments ( Fig. 2B View FIGURE 2 ). Paired setae in laterodorsal and ventrolateral positions ( Figs. 2 View FIGURE 2 A-–B, 3F, 4D, F). Sensory spots in paradorsal, subdorsal, laterodorsal and ventromedial positions ( Figs. 2A–B View FIGURE 2 , 3F View FIGURE 3 , 4D, F View FIGURE 4 ).

Segment 6 similar to segment 4 in the arrangement of cuticular elevation, setae and sensory spots ( Figs. 2A–B View FIGURE 2 , 3F View FIGURE 3 , 4D, G View FIGURE 4 ).

Segment 7 similar to segment 3 in the arrangement of setae and most sensory spots, but lacking the middorsal elevation and paradorsal sensory spots ( Figs. 2A–B View FIGURE 2 , 3H View FIGURE 3 , 4C, G View FIGURE 4 ). Bilateral deviation was observed in two specimens, as the ventromedial seta was lacking on one of the sternal plates.

Segment 8 without middorsal process or elevation. Unpaired seta in paradorsal position, and paired setae in lateroventral and ventromedial positions, the latter longitudinally aligned with those of the preceding segments ( Figs. 2A–B View FIGURE 2 , 3G–H View FIGURE 3 , 4C View FIGURE 4 ). Sensory spots in subdorsal (two pairs), laterodorsal (one pair) and ventromedial (one pair) positions ( Figs. 2A–B View FIGURE 2 , 3G–H View FIGURE 3 , 4C View FIGURE 4 ). Bilateral deviation was observed in two specimens, as the ventromedial seta was lacking on one of the sternal plates.

Segment 9 without middorsal process or elevation. Paired setae in laterodorsal and ventromedial positions ( Figs. 2A–B View FIGURE 2 , 3G, J View FIGURE 3 , 4E View FIGURE 4 ). Deviation was observed in a single male specimen, as the ventromedial pair of setae was absent. Sensory spots in subdorsal (two pairs), laterodorsal (one pair), ventrolateral (one pair) and ventromedial (one pair) positions ( Figs. 2A–B, D View FIGURE 2 , 3G, J View FIGURE 3 , 4E View FIGURE 4 ). Nephridia externally opening as short cuticular tubes with fringed tips ( Fig. 2A View FIGURE 2 ).

Segment 10 without middorsal process or elevation. Two pairs of setae in lateroventral position ( Figs. 2A–B, D View FIGURE 2 , 4E View FIGURE 4 ). Sensory spots in subdorsal, laterodorsal, ventrolateral and ventromedial positions ( Figs. 2A–B View FIGURE 2 , 3I View FIGURE 3 , 4E View FIGURE 4 ).

Segment 11 with three pairs of type 3 sensory spots in subdorsal position ( Fig. 2B View FIGURE 2 ). Males with two pairs of sexually dimorphic penile spines and genital pores ( Figs. 2A View FIGURE 2 , 3I View FIGURE 3 ). Lateral terminal spines ( Figs. 2A–B, D View FIGURE 2 , 3A View FIGURE 3 , 4A View FIGURE 4 ) relatively long (LTS:TL interval = 19.7–33.0 %; LTS:TL mean = 27.2%; Table 2).

Remarks. The specimen mounted for SEM carried several epibiontic Ciliophora on the sternal plates of segments 1 and 5 ( Fig. 4A, H–I View FIGURE 4 ).

References

Figures

Tables

TABLE 2. Measurements (in μm) of six adult specimens of Leiocanthus quinquenudus sp. nov. (three females and three males) from the Gulf of Mexico. Abbreviations: LTS, lateral terminal spine length; MSW-5, maximum sternal width (measured at segment 5); n, number of measured specimens; S, segment length (followed by number of corresponding segment); SD, standard deviation; SSW, standard sternal width (measured at segment 10); TL, trunk length. Character Holotype Range Mean (SD; n) TL 475.9 475.9–661.7 556.7 (70.0; 6) MSW-5 134.0 127.4–143.5 135.9 (6.4; 6) MSW-5/TL (%) 28.2 20.6–28.2 24.7 (2.9; 6) SSW 113.8 108.5–150.4 121.6 (15.1; 6) SSW/TL (%) 23.9 17.6–23.9 22.0 (2.2; 6) S1 85.5 80.7–96.5 88.0 (6.5; 6) S2 49.5 49.5– 62.4 56.7 (5.3; 6) S3 51.5 51.5–61.2 55.8 (4.5; 6) S4 52.1 52.1–71.0 61.6 (8.2; 6) S5 52.9 52.9–72.1 62.0 (7.4; 6) S6 56.0 56.0–71.2 64.1 (5.7; 6) S7 59.7 57.9–78.9 65.4 (9.2; 6) S8 58.9 58.9–78.6 66.7 (8.4; 6) S9 54.4 54.4–80.4 64.6 (9.5; 6) S10 54.1 48.0–75.6 62.7 (12.4; 6) S11 42.1 34.8–51.5 40.0 (6.2; 6) LTS 157.1 130.1–157.1 145.4 (10.4; 6) LTS/TL (%) 33.0 19.7–33.0 27.2 (5.0; 6)

Character	Holotype	Range	Mean (SD; n)
TL	475.9	475.9–661.7	556.7 (70.0; 6)
MSW-5	134.0	127.4–143.5	135.9 (6.4; 6)
MSW-5/TL (%)	28.2	20.6–28.2	24.7 (2.9; 6)
SSW	113.8	108.5–150.4	121.6 (15.1; 6)
SSW/TL (%)	23.9	17.6–23.9	22.0 (2.2; 6)
S1	85.5	80.7–96.5	88.0 (6.5; 6)
S2	49.5	49.5– 62.4	56.7 (5.3; 6)
S3	51.5	51.5–61.2	55.8 (4.5; 6)
S4	52.1	52.1–71.0	61.6 (8.2; 6)
S5	52.9	52.9–72.1	62.0 (7.4; 6)
S6	56.0	56.0–71.2	64.1 (5.7; 6)
S7	59.7	57.9–78.9	65.4 (9.2; 6)
S8	58.9	58.9–78.6	66.7 (8.4; 6)
S9	54.4	54.4–80.4	64.6 (9.5; 6)
S10	54.1	48.0–75.6	62.7 (12.4; 6)
S11	42.1	34.8–51.5	40.0 (6.2; 6)
LTS	157.1	130.1–157.1	145.4 (10.4; 6)
LTS/TL (%)	33.0	19.7–33.0	27.2 (5.0; 6)

Abbreviations

SCL	St. Cloud State University

Copyright notice

No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.

Taxonomy

Kingdom	Animalia
Phylum	Kinorhyncha
Class	Allomalorhagida
Family	Pycnophyidae
Genus	Leiocanthus