Pandanipora helix, 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: 9-15

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/521587E4-563A-5509-09EE-FCEF884EFDBB

treatment provided by

Plazi

scientific name

Pandanipora helix
status

n. sp.

Pandanipora helix   n. sp.

( Figs 2A –E View FIGURE 2 , 3–5 View FIGURE 3 View FIGURE 4 View FIGURE 5 )

‘? Incertae sedis   no. 4’ Harmelin & d’Hondt 1982: 13, pl. 4, figs 1–2; d’Hondt & Schopf 1985: 950, pl. 8, fig. 5.

‘Cyclostome indéterminé’ d’Hondt & Schopf 1985: 949, pl. 8, fig. 3.

Material examined. Holotype: ZIRAS 1/50667, colony detached from nodule, YMG R.V. Gelendzhik cruise GLD4–12, Stn 238, 11 March 2013, 13.44587° N, 132.91008° W, 4772 m. Paratype 1: ZIRAS 2/50668, colony detached from nodule, YMG R.V. Yuzhmorgeologiya cruise YMG4–04, Stn 61, 5 September 2005, 13.59717° N, 130.65212° W, 5008 m. Paratype 2: ZIRAS 3/50669, colony detached from nodule, YMG R.V. Gelendzhik cruise GLD4–08, Stn 153, 26 July 2009, 13.15205° N, 133.89166° W, 5014 m. Paratype 3: ZIRAS 4/50670, colony detached from nodule, YMG R.V. Gelendzhik cruise GLD4–12, Stn 259, 10 April 2013, 12.86148° N, 132.82182° W, 4910 m. Paratype 4: ZIRAS 5/50671, colony detached from nodule, YMG R.V. Gelendzhik cruise GLD4–09, Stn 176, 24 December 2010, 12.93062° N, 133.56097° W, 4865 m. Paratype 5: ZIRAS 6/50672, colony attached to nodule particle, YMG R.V. Gelendzhik cruise GLD4–09, Stn 190, 3 January 2011, 13.38432° N, 133.51833° W, 4838 m. Additional material: YMG18–01, Stns 17, 23, 27, 32; YMG4–04, Stns 52, 53, 54, 55; YMG4–06, Stns 65, 68, 73, 85, 94, 96, 105, 106, 110, 114; YMG4–07, Stns 116, 117, 120, 125, 134, 136, 141, 143; GLD4–08, Stns 144, 145, 146, 150, 154, 155, 157, 160, 161, 164; GLD4–09, Stns 165, 166, 169, 170, 173, 174, 181, 185, 193, 194, 197, 199; GLD4–11, Stns 212, 214, 215, 217, 218, 219, 224, 225, 226, 227, 231, 233; GLD4–12, Stns 235, 236, 245, 246, 253, 255, 258, 260, 262, 263, 264, 265, 272; YMG4–13, Stns 275, 276, 282, 285, 289, 292, 293, 295, 305, 308, 310, 319, 321; YMG4–14, Stns 324, 326, 328, 329, 330, 331, 332, 334, 335, 336, 338, 340, 342, 343, 346, 349, 350, 352, 354, 356, 358, 359, 361, 363, 364, 365. Total specimens examined 203.

Etymology. Latin and Greek, helix   , a coil or spiral, alluding to the common form of the colony; used as a noun in apposition.

Description. Colony uniserial, semi-erect, white, comprising chain of zooids borne above solid substratum by elongated prop-like supports ( Figs 2A –E View FIGURE 2 , 3A –G View FIGURE 3 ), typically one (very rarely two) per zooid, body cavity of zooid continuous with that of prop ( Fig. 5E View FIGURE 5 ). Zooidal chain varied in disposition, either straight and more or less parallel to substratum or often ascending as open helicospiral, with up to 2.5 turns ( Fig. 3C View FIGURE 3 ) depending on age; many colonies have form somewhat intermediate between these extremes. Branching of uniserial stem uncommon, typically near colony origin, rarely further along stem ( Fig. 3E View FIGURE 3 ). Maximum colony length or diameter 12.60 mm; maximum colony height 3.74 mm. Most zooids seen in colonies ~24 (holotype; Fig. 3A, C View FIGURE 3 ) and 26 ( Fig. 2E View FIGURE 2 ).

Autozooids comprising proximal and distal components; axial proximal component forms part of continuous uniserial stem of colony, while distal component forms erect peristome of varying length. Frontal peristomial surface typically curving obliquely frontalwards from axial frontal surface; distal peristomial surface forming much sharper angle (up to 90°) with frontal wall of daughter zooid. Autozooidal surface wholly gymnocystal (i.e. exterior-walled), with weak longitudinal and transverse striae or wrinkles ( Figs 4B, C, J, K View FIGURE 4 ), latter more apparent in zooidal peristomes; at higher magnification exterior surface made up of wall-perpendicular needle-like crystallites ( Fig. 4P, Q View FIGURE 4 ). Very tiny simple pseudopores occurring sparsely in zooidal walls ( Fig. 4O –Q View FIGURE 4 ). Peristomial opening circular, very thin-walled ( Figs 4J –M View FIGURE 4 ), becoming thicker through accretion of additional layers of crystallites. Interior surface of peristomes lined by distally imbricated foliated fabric of wedge-shaped crystallites ( Fig. 4N View FIGURE 4 ) that tend to be shorter and chunkier in proximal axial walls of zooids, especially around interior openings of pseudopores ( Fig. 4D View FIGURE 4 ). Zooidal axial and peristomial lengths generally similar, but can be independently variable, with peristomes slightly shorter than, or up to more than twice length of proximal axial portion of zooid ( Fig. 3G View FIGURE 3 ).

Budding of daughter zooids achieved by development of partition from floor of parent zooid ( Fig. 4B, C View FIGURE 4 ) that slopes frontalwards under elevating peristomial portion, with completed parent zooids overlapping proximal portion of daughter zooids; thus parts of 2–3 zooidal chambers seen in transverse section of stem ( Fig. 4A View FIGURE 4 ). In lessattenuated colonies with tight helicospiral form, axis becomes thicker ( Fig. 3A, B View FIGURE 3 ) and budding sites are condensed.

Prop-like supports elevate colony after its founding. These greatly variable in size and form. Some props have widened (up to three times wider than their mean diameter) bases at their points of contact with substratum. Typically, one prop per autozooid, originating near point where internal partitioning of daughter autozooid takes place ( Figs 4A View FIGURE 4 , 5E View FIGURE 5 ); sometimes additional prop interpolated in series (e.g. Fig. 3G View FIGURE 3 ). Props can be length of peristome or very much longer and almost filiform ( Fig. 3B View FIGURE 3 ). Short, stumpy props that do not reach substratum appear to represent repaired broken props. Where they encounter substratum, proximal ends of props have short branches that splay out over irregularities ( Fig. 5A –C View FIGURE 5 ). Tiny sparse pseudopores occur in prop walls ( Fig. 5F View FIGURE 5 ).

Gonozooid not seen.

Ancestrula erect ( Fig. 5G –L View FIGURE 5 ). Protoecium short, rounded, squat, imperforate, broader than peristome that emerges from its dome, with scarcely any differentiation in calcification. Peristome typically bent in direction of initial colony growth.

Measurements (mm). Holotype, ZIRAS 1/50667 ( Fig. 3A, C View FIGURE 3 ): Colony height 3.74, length 2.91, width 2.58 (L × W = helix   in frontal view); ZL 1.373–1.918 (1.628 ± 0.181) (n = 8); PrL 0.458–2.443 (1.518 ± 0.999) (n = 3); PrD 0.120–0.186 (0.145 ± 0.035) (n = 3); PeL 0.243–0.442 (0.318 ± 0.067) (n = 8); PeD 0.177–0.186 (0.181 ± 0.003) (n = 4); ApL 0.170–0.178 (0.173 ± 0.003) (n = 4); ApW 0.162–0.170 (0.165 ± 0.004) (n = 4).

Paratype 1, ZIRAS 2/50668 ( Fig. 3B View FIGURE 3 ): Colony height 3.39, length 6.41, width 4.88 (L × W = size of coil in frontal view); ZL 1.443–2.288 (1.989 ± 0.287) (n = 6); PrL 1.211–3.165 (2.373 ± 0.672) (n = 6); PrD 0.073–0.104 (0.082 ± 0.012) (n = 6); PeL 0.516–0.893 (0.776 ± 0.137) (n = 6); PeD 0.174–0.185 (0.180 ± 0.004) (n = 6); ApL 0.165–0.173 (0.168 ± 0.003) (n = 6); ApW 0.155–0.164 (0.160 ± 0.004) (n = 6).

Paratype 5, ZIRAS 6/50672 ( Fig. 3G View FIGURE 3 ): Colony height 2.52, length 6.92; ZL 1.823–2.838 (2.261 ± 0.338) (n = 6); PrL 0.628–0.993 (0.834 ± 0.149) (n = 6); PrD 0.083–0.138 (0.108 ± 0.019) (n = 6); PeL 0.924–1.581 (1.214 ± 0.244) (n = 6); PeD 0.178–0.198 (0.190 ± 0.007) (n = 6); ApL 0.173–0.185 (0.180 ± 0.004) (n = 6); ApW 0.161–0.187 (0.174 ± 0.009) (n = 6).

Non-type specimen YMG4–14, Stn 326 ( Fig. 5G –I View FIGURE 5 ): AnPeD 0.156 (n = 1).

Remarks. In the collections examined for this study, Pandanipora helix   n. sp. is represented by 203 colonies, which makes it all the more remarkable that not one bears a gonozooid. One possibility is that it never has gonozooids, but, among living cyclostomes, only species of Cinctiporidae   unequivocally lack such structures ( Boardman et al. 1992). Insofar as cinctiporids have exceptionally large autozooids, it appears likely that oogenesis and embryo formation takes place within them (see Schwaha et al. 2018). Zooidal size in Pandanipora helix   n. sp. is not exceptional and there seems no reason that a peristomial gonozooid like that in Peristomatopora   should not be present. Gonozooids were also notably absent from most colonies in the large collection of Antarctic cyclostomes studied by Ostrovsky & Taylor (1996) and Ostrovsky (1998a). What is striking is that non-fertile colonies otherwise were of the same size as those bearing gonozooids, thus supporting the idea that incubation chambers will develop only if a colony is fertilized by alien sperm ( Ryland 1996). In other words, sperm limitation may be a reason for the lack of gonozooids in many colonies. Experiments conducted on two cyclostome species by Jenkins et al. (2015) showed restrained female investment in the absence of mating opportunity; either the production of female zooids and progeny is much reduced in reproductive isolation, or development of gonozooids begins, but ceases further development in the absence of mating opportunity. Another possibility in Pandanipora helix   is that incubation chambers are produced but are shed after release of embryos. Alternatively, gonozooids may be very fragile, and lost during the process of collection from the seafloor and subsequent processing of the polymetallic nodules.

Harmelin & d’Hondt (1982) illustrated an unnamed species from 3392–3429 m depth off the coast of Surinam that conforms to the characters of the genus. D’Hondt & Schopf (1985) reported this same species again from 943 m off Recife and 3459–3783 m on the equatorial mid-Atlantic Ridge. What they interpreted as ‘épines autozoéciales’ appear in their illustrations to be broken prop-like supports, of proportionately smaller diameter than in P. helix   n. sp. Even closer to P. helix   in appearance, and almost certainly conspecific, was a colony from 6065–6079 m in the central North Pacific north of the Hawaiian seamount chain. Based on this evidence, it appears likely that P. helix   n. sp. may be fairly widespread in the abyssal north Central Pacific, with an undescribed sibling species in the abyssal tropical Atlantic.

Our material shows up to five brown bodies retained in zooidal chambers ( Fig. 5E View FIGURE 5 ), indicating multiple regression and regeneration of polypides.

Distribution. Recorded from 118 stations within coordinates 12.26676– 14.64985° N, 129.08802– 134.67060° W, at depth range 4677–5280 m.