Echinoderes tubilak Higgins & Kristensen 1988

Echinoderes tubilak

DIAGNOSIS.—Middorsal spines on segments 6–10, increasing uniformly in length posteriorly; lateral spines on segments 7–11, round to oval cuticular scars (pores?) in L–4 (adhesive tubes) and SD-4 positions; lateral terminal spines short to moderate, 64–160 μm long, 17.0–41.6 percent of trunk length; slight indication of sutured ventral midline near pachycyclus of segment 4; pectinate fringe well developed on ventral surface of segments 3 and 4; pectinate fringe on segment 3 with median area of distinct fringe and lateral areas of wider fringe elements; segment 4 with uniformly distinct fringe; perforation sites sparsely distributed over both dorsal and ventral surfaces.

DESCRIPTION.—Adult (Figures 65–80) trunk length 333–415 μm; MSW-8, 58–68 μm, 14.6–19.8 percent of trunk length; SW 44–56 μm, 10.9–15.6 percent of trunk length.

Segment 2 consisting of 16 placids, 14–18 μm long, x 53 = 16.4±0.8 μm; midventral placid truncate, anterior margin slightly expanded laterally, wider (∼14 μm) than others (∼8 μm); ventral trichoscalid plates (of head segment) overlapping alternate placids, broadly expanded posteriorly; dorsal trichoscalid plates narrow (Figures 67, 68, 71, 72).

Segment 3, 31–42 μm long, x 54 = 39.0±2.1 μm; middorsal cuticular scar near anterior margin, narrowly oval in vertical axis; round cuticular scars on sides of ventral midline near posterior margin of segment, smaller cuticular scars situated more laterally; small, angular muscle(?) scars near anterolateral margins of ventral surface; few perforation sites scattered along anterior margin of dorsal surface, single row near posterior margin; few posteromedial perforation sites on ventral surface; pectinate fringe of median one-third of ventral surface uniform in width (∼2 μm) and length (∼9 μm), contrasting distinctly with wider (∼4 μm), longer (∼13 μm) uniform-sized fringe laterally (but not continuing dorsally); pectinate fringe slightly diminished in size in females, fringe barely visible on dorsal margin in either sex.

Segment 4, 18–39 (μm long, x 54 = 34.9±2.9 μm; narrowly elongate middorsal scar similar to that on previous segment; subdorsal and additional lateral round cuticular scars near posterior margin; narrowly elongate cuticular scars on sides of ventral midline, additional oval to round cuticular scars (pores?) at presumptive sites of missing lateral spines (adhesive tubes), near posterior margin; perforation sites in 2 poorly organized 2 rows dorsally, 2 or 3 rows ventrally; pectinate fringe barely visible on dorsal margin; pachycyclus well developed, cuticularization extending posteriorly for short distance along midventral line, slight fissure indicated within midventral cuticularization.

Segment 5, 34–46 μm long, x 54 = 39.4±2.8 μm; narrowly elongate middorsal cuticular scar near anterior margin, similar cuticular scars centered on each ventral plate; 3 rows of perforation sites on both dorsal and ventral surfaces; pectinate fringe barely visible on both dorsal and ventral surfaces.

Segment 6, 35–50 μm long, x 54 = 42.3±3.6 μm; middorsal spine 44–60 μm long, x 52 = 49.4±3.7 μm; subdorsal, narrowly elongate cuticular scars at sides of middorsal spine; additional circular cuticular scars situated posterolateral to middorsal spines; segment otherwise similar to segment 5.

Segment 7, 40–53 μm long, x 54 = 46.9±4.9 μm; middorsal spine 50–66 μm long, x 52 = 59.9±3.5 μm; lateral spines, probably adhesive tubes, 8–26 μm long, x 27 = 17.0±3.2 μm, near lateroventral margins of tergal plate; subdorsal pair of narrowly elongate cuticular scars flanking middorsal spine, no other cuticular scars noted; similar anteromedian cuticular scars on ventral plates, additional round cuticular scars laterally, near posterior margins of ventral plates; perforation sites organized into 3 rows dorsally, 3 or 4 less organized rows ventrally; segment otherwise similar to segment 6.

Segment 8, 44–60 μm long, x 54 = 52.0±4.1 μm; MSW 58–68 μm, x 53 = 63.7±2.4 μm, MSW/TL 14.6–19.8 percent, x 53 = 16.6±1.1 percent; middorsal spine 54–71 μm long, x 52 = 63.2±3.7 μm; lateral spines 36–48 μm long, x 54 = 41.2±2.3 μm; as compared with segment 7, ventral plates with additional perforation sites, and round cuticular scars directly posterior and closer to narrowly oval cuticular scars; otherwise similar to segment 7.

Segment 9, 48–62 μm long, x 54 = 55.9±4.0 μm; middorsal spine 60–78 μm long, x 53 = 65.5±4.0 μm; lateral spines 42–50 μm long, x 54 = 44.0±2.2 μm; ventral plates with fewer perforation sites than on segment 8; round cuticular scars of previous segment now more oval than those on segment 8 and positioned posterolaterally as on segment 7; segment otherwise similar to segment 8.

Segment 10, 52–66 μm long, x 54 = 58.4±3.2 μm; middorsal spine 58–76 μm long, x 51 = 64.5±4.0 μm; lateral spines 38–50 μm long, x 53 = 44.0±2.5 μm; round cuticular scars of previous segment absent; segment otherwise similar to segment 9.

Segment 11, 51–60 μm long, x 54 = 54.4±2.2 μm; middorsal spine absent; lateral spines 30–48 μm long, x 51 = 37.2±4.7 μm; narrowly elongate subdorsal cuticular scars in same position as those on segment 10, 2 circular cuticular scars situated more posteriorly than those on segment 10; prominent, narrowly elongate muscle scars positioned laterally; as in segment 9, circular cuticular scars near posterolateral margins of ventral plates but with slightly fewer perforation sites; segment otherwise similar to segment 10.

Segment 12, 46–55 μm long, x 54 = 49.8±6.5 μm; SW44–56 μm, x 53 = 49.4±3.4 μm; SW/TL 10.9–15.6 percent, x 53 = 12.8±1.2 percent; lateral spines absent; narrowly elongate middorsal scar near anterior margin, second such scar posteriorly adjacent; narrowly elongate muscle scars as in segment 11; additional narrowly elongate cuticular scars posteromesial to muscle scars; ventral plates with prominent oval muscle scars posterior to narrowly elongate cuticular scars near anteromesial margins; perforation sites few; pectinate fringe barely visible.

Segment 13, 20–38 μm long, x 54 = 27.7±3.9 μm; tergal furcae evenly lanceolate (Figures 69, 70, 73, 74); ventral plates with rounded posterior margins, moderately fringed; lateral terminal spines 64–160 μm long, x 54 117.4±31.7 μm; LTS/TL 17.0–41.6 percent, x 54 = 30.7±8.1 percent; lateral terminal accessory spine of females 42–66 μm long, x 26 = 56.0±5.8 μm; LTAS/TL 10.5–17.8 percent, x 26 = 14.8±2.1 percent; LTAS/LTS 52.5–83.9 percent, x 26 = 65.8±7.2 percent; penile spines of male: P-l 28–40 μm long, x 21 = 31.9±3.0 μm; P-2 16–22 μm long, x 15 = 18.8±1.7 μm; P-3 30–36 μm long, x 12 = 32.0±.2.3 μm.

In addition to the lack of lateral accessory spines and the presence of 3 pairs of penile spines, males differ from females in having a slightly narrower standard width (relatively narrower posteriorly), slightly shorter lateral spines, and much shorter lateral terminal spines (an average of 22.8 percent of the trunk length as contrasted with an average of 38.0 percent of the trunk length in females).

Morphometric data for adult specimens are shown in Table 5.

HOLOTYPE.—Adult female, TL 415 μm (Figures 65–70, 75–79), Disko Island, sta RH 1529, USNM 233226.

ALLOTYPE.—Adult male, TL 395 μm (Figures 71–74, 80), other data as for Holotype, USNM 233227.

PARATYPES.—Eleven females and 16 males, TL 360–415 μm, other data as for holotype, USNM 233228; 1 female and 1 male, TL 385–395 μm, Disko Island, sta RH 1532, USNM 233229; 3 females and 4 males, TL 365–385 μm, Disko Island, sta RH 1533, USNM 233230; 115 unmounted specimens, Disko Island, sta RH 1535, USNM 233231; 3 females, TL 400–415 μm, Disko Island, sta RH 1536, USNM 233232; 4 males, TL 398–410 μm, Disko Island, sta RH 1537, USNM 233233; 6 females and 1 male, TL 333–350 μm long, Disko Island, sta RH 1538, USNM 233234.