Discantenna metallica, Grischenko & Gordon & Melnik, 2018

Grischenko, Andrei V., Gordon, Dennis P. & Melnik, Viacheslav P., 2018, Bryozoa (Cyclostomata and Ctenostomata) from polymetallic nodules in the Russian exploration area, Clarion - Clipperton Fracture Zone, eastern Pacific Ocean-taxon novelty and implications of mining, Zootaxa 4484 (1), pp. 1-91: 21-25

publication ID

https://doi.org/10.11646/zootaxa.4484.1.1

publication LSID

lsid:zoobank.org:pub:D66524CF-9C6D-4DF4-8CA2-B2C9708CF5FD

persistent identifier

http://treatment.plazi.org/id/521587E4-5626-551F-09EE-FE04884FFD03

treatment provided by

Plazi

scientific name

Discantenna metallica
status

n. sp.

Discantenna metallica   n. sp.

( Figs 2I View FIGURE 2 , 10–12 View FIGURE 10 View FIGURE 11 View FIGURE 12 )

Material examined. Holotype: ZIRAS 1/50675, colony detached from nodule, YMG R.V. Yuzhmorgeologiya cruise YMG4–06, Stn 67, 8 August 2006, 13.18842° N, 134.51227° W, 4820 m. Paratype 1: ZIRAS 2/50676, colony detached from nodule, YMG R.V. Gelendzhik cruise GLD4–11, Stn 224, 2 May 2012, 12.55585° N, 133.08295° W, 4778 m. Paratype 2: ZIRAS 3/50702, colony detached from nodule, YMG R.V. Yuzhmorgeologiya cruise YMG18–01, Stn 37, 29 August 2003, 13.85300° N, 129.08458° W, 4715 m. Additional material: YMG4–06, Stns 69, 82; GLD4–08, Stn 151; GLD4–11, Stns 207, 225; YMG4–14, Stns 358, 362. Total specimens examined 11.

Etymology. Latin, metallica   , pertaining to a mineral, alluding to the substratum.

Description. Colony erect, white, stalked, from narrow encrusting base ( Fig. 11K View FIGURE 11 ). Initially uniserial, becoming biserial, distal end of base developing erect column that expands into shallow circular or irregular discoidal structure, up to 3.45 mm diameter, in which zooids are centripetally arranged; colony height up to 4.94 mm.

Apical disk bereniciform ( Fig. 10A, B View FIGURE 10 ); up to 52 zooidal peristomes, angled obliquely outwards from depressed center of disk; peripheral common bud thin, with narrow marginal lamina pierced by pseudopores and having skeletal microstructure of distally imbricated foliated crystallites. Calcified terminal diaphragms ( Figs 10F View FIGURE 10 , 11A, G, M View FIGURE 11 ) common in older, proximal zooids; diaphragms made up of fused sectors of needle-like crystallites ( Fig. 11F View FIGURE 11 ); 2–5 tiny pseudopores apparent.

Only two gonozooids seen, each produced at edge of small capitulum of unattached stem ( Fig. 11A View FIGURE 11 ). Stem with ~10 short peristomes of varied length, ~6 of them with apertures occluded by diaphragms. Capitulum with irregular profile in apical view owing to many peristomes broken at base; made up of four ‘sectors’, each comprising fused parts of adjacent peristomes, one of which bears gonozooid. Gonozooid broader than long ( Fig. 11C –E View FIGURE 11 ), with broadly W-shaped margin on capitulum side ( Fig. 11B View FIGURE 11 ) or this not evident ( Fig. 11C View FIGURE 11 ); moderately inflated frontally either side of shortly projecting ooeciostome ( Fig. 11C, I View FIGURE 11 ) with near-circular ooeciopore with thin slightly irregular rim ( Fig. 11D, E, H, I View FIGURE 11 ). Gonozooid wall with greater pseudopore density.

Ancestrula suberect, protoecium inclined at 50–60° angle to substratum ( Fig. 12A, C, D, E, H View FIGURE 12 ). Protoecium may be shortly flared at base ( Fig. 12H View FIGURE 12 ), continuous with peristome, surface with needle-like crystallites and sparse pseudopores. Abfrontal sides of ancestrular zooid, 3–4 daughter zooids and base of colony of erect fascicle of zooids supported by basal layer and skirt of kenozooids and extrazooidal calcification ( Fig. 12B, F View FIGURE 12 ); base of skirt with irregular margin depending on substratum; exterior surface marked by vertical striae and ridges ( Fig. 12H View FIGURE 12 ), and moderately sparse but evenly distributed pseudopores.

Daughter zooid distal to ancestrula initiating biseriality by budding two additional zooids, their respective peristomes directed to left and right ( Fig. 12E, F, H View FIGURE 12 ), after which 5–11 additional peristomes may be produced around base of what will become erect stem of capitulum ( Fig. 12I –L View FIGURE 12 ), which shows chambers of seven (some as small proximal ends) in cross section in one example ( Fig. 12J View FIGURE 12 ). Non-functioning older zooids with closure plates, near or below peristomial rim ( Figs 11 View FIGURE 11 , 12A, K View FIGURE 12 ).

Measurements (mm). Holotype, ZIRAS 1/50675 ( Fig. 10A –D View FIGURE 10 ): Colony height 2.95; capitulum length 4.15, width 3.45; stalk cross-section at point of breakage 0.35 × 0.40; stalk cross-section at junction with disk 0.71 × 0.53; stalk height (from point of breakage to disk) 1.53. Disk zooids: ZL 0.772–1.295 (0.979 ± 0.166); PeL 0.221–0.713 (0.414 ± 0.179); PeD 0.123–0.140 (0.131 ± 0.005); ApL 0.132–0.171 (0.151 ± 0.013); ApW 0.098–0.132 (0.115 ± 0.012). Stalk zooids (n = 4): ZL 0.543–0.628 (0.583 ± 0.035); PeL 0.142–0.211 (0.172 ± 0.029); PeD 0.135–0.148 (0.141 ± 0.006); ApL 0.113–0.128 (0.122 ± 0.006); ApW 0.103–0.123 (0.112 ± 0.009).

Paratype 1, ZIRAS 2/50676 ( Figs 10E –I View FIGURE 10 , 11C, E, H, I View FIGURE 11 ): Colony height 4.94. Stalk: height (substrate to disk) 3.57, cross-section (narrowest, near ancestrula) 0.45 × 0.33, cross-section at junction with disk 0.58 × 0.38. Disk zooids (n = 5): ZL 0.995–1.731 (1.342 ± 0.261); PeL 0.358–0.818 (0.456 ± 0.202); PeD 0.133–0.152 (0.143 ± 0.007); ApL 0.151–0.178 (0.164 ± 0.012); ApW 0.118–0.136 (0.130 ± 0.006). Stalk zooids (n = 4): ZL 0.698–0.953 (0.834 ± 0.126); PeL 0.078–0.103 (0.092 ± 0.010); PeD 0.138–0.161 (0.150 ± 0.011); ApL 0.128–0.147 (0.136 ± 0.008); ApW 0.122–0.130 (0.126 ± 0.003). Gonozooid (n = 1): GZL 0.406; GZW 0.483; GZH 0.352; OsL 0.114; OsD 0.117–0.077; OpD 0.067.

Paratype 2, ZIRAS 3/50702 ( Fig. 11A, B, D View FIGURE 11 ): Gonozooid (n = 1): GZL 0.337; GZW 0.561; GZH 0.294; OpL 0.072; OpD 0.078.

Non-type specimen YMG4–14, Stn 358 ( Fig. 12A –D View FIGURE 12 ): AnPeD 0.115 (n = 1).

Remarks. Discantenna metallica   n. sp. is only the second known species. The type species, D. tumba   , was described from 943–1097 m depth on the Chatham Rise, New Zealand. Inter alia, D. metallica   differs from it by achieving a larger colony size (> 4 mm high and wide, cf. <2.6 mm high and wide in D. tumba   ) with many more peristomes in the elevated disk (~52, cf. ~24) having a diameter up to 0.17 mm (cf. 0.08 mm). Whereas tubular peristomes are arranged along only the frontal side of the stem in D. tumba   (with the abfrontal side pseudoporous), such peristomes alternate around the stem in a spiral pattern in D. metallica   . Stem peristomes are short in D. tumba   , but can be quite elongate in D. metallica   , some exceeding the radius of the disk. Interestingly, even though disk size is bigger in D. metallica   , the only specimens with a gonozooid had incompletely developed capitula. Whereas the incubation chamber in D. tumba   is set back from the edge of the capitulum, that in D. metallica   projects a little from the margin, with the ooeciostome outermost. The gonozooid in D. metallica   n. sp. resembles that in the following new genus and species, which we attribute to the Oncousoeciidae   .

Distribution. Recorded from 10 stations within coordinates 12.55585– 14.37702° N, 129.08458– 134.51227° W, at depth range 4715–5238 m.