Sporadopora dichotoma ( Moseley, 1876 )

Bernal, M. C., Cairns, S. D., Penchaszadeh, P. E. & Lauretta, D., 2021, Stylasterids (Hydrozoa: Stylasteridae) from Mar del Plata submarine canyon and adjacent area (southwestern Atlantic), with a key to the species off Argentina, Zootaxa 4969 (3), pp. 401-452: 29-30

publication ID

https://doi.org/10.11646/zootaxa.4969.3.1

publication LSID

lsid:zoobank.org:pub:140804AC-7852-46F4-811D-3D86F4AA1130

DOI

http://doi.org/10.5281/zenodo.4792431

persistent identifier

http://treatment.plazi.org/id/9E6F9574-4952-BA22-FF04-44D731A7F8AA

treatment provided by

Plazi

scientific name

Sporadopora dichotoma ( Moseley, 1876 )
status

 

Sporadopora dichotoma ( Moseley, 1876)  

( Fig. 12a View FIGURE 12 ; Fig. 17 View FIGURE 17 )

Polypora dichotoma Moseley, 1876: 94–95  

Sporadopora dichotoma: Moseley 1879: 429–440   , pl. 34, figs. 1–2, pl. 35, figs. 1, 2, 9, pl. 36, pl. 43, figs. 1–9, 12, pl. 44, figs. 13–14; Moseley 1881: 36–47, 83, pl. 1, figs. 1– 2, pl. 2, figs. 1, 2, 9, pl. 3, pl. 10, figs. 1–9, 12, pl. 11, figs. 13–14; Boschma 1957: 60–61; Boschma 1964: 61–62; Cairns 1983a: 65–67, figs. 1a–b, 2a–i, 3a–b, map 1; Cairns 1983b: 436–438, figs. 2a–h, 24f, 25h, 27a, 28c; Cairns 1991: 44–46; Cairns & Macintryre 1992: 98, table 1; Zamponi 2008: 188, 198, fig. 9; Río Iglesias et al. 2012: 191; Bax & Cairns 2014: 108–111, table 1, map 4

Distribution. Off Mar del Plata, Argentina, 1097 m; Patagonia, 42° S to 48° S; Scotia Arc from Tierra del Fuego to South Georgia, Malvinas Islands and Shetland Islands, 250–1498 m. New record off Mar del Plata, 854–2204 m.

Material examined. USNM 60098 View Materials off Burdwood Bank , Eltanin St. 1593 (54° 43–42’ S, 56° 37–39’ W)   ; USNM 60100 View Materials off South Georgia, ARA Islas   Orcadas St. 575–34 (54° 41.6’ S, 34° 51.1’ W); GoogleMaps   MACN-In 40650 off Mar del Plata , Argentina, St. 35 (37° 54.045’ S, 54° 24.091’ W), 1245 m, May 2013; MACN-In 40651 off Mar del GoogleMaps   Plata , Argentina, St. 59 (37° 49.688’ S, 54° 5.236’ W), 1398 m, September 2013 GoogleMaps   ; MACN-In 42502 off Mar del Plata , Argentina, St. 11 (37° 59.258’ S, 54° 41.436’ W), 854 m, August 2012 GoogleMaps   ; MACN-In 42503 off Mar del Plata , Argentina, St. 42 (37° 59.110’ S, 54° 41.136’ W), 877 m, May 2013 GoogleMaps   ; MACN-In 42504 off Mar del Plata , Argentina, St. 37 (37° 59.848’ S, 54° 24.206’ W), 1275 m, May 2013 GoogleMaps   ; MACN-In 42505 off Mar del Plata , Argentina, St. 41 (38° 01.631’ S, 54° 30.275’ W), 997 m, May 2013 GoogleMaps   ; MACN-In 42506 off Mar del Plata , Argentina, St. 25 (37° 51,688’ S, 54° 10,550’ W), 1950 m, August 2012 GoogleMaps   ; MACN-In 42507 off Mar del Plata , Argentina, St. 56 (37° 54.840’ S, 54° 2.470’ W), 2204 m, September 2013 GoogleMaps   ; MACN-In 42508 off Mar del Plata , Argentina, St. 60 (37° 51.700’ S, 54° 4.583’ W), 1584 m, September 2013 GoogleMaps   .

Description. Colonies robust and large. Uniplanar growth, although some deviations from main plane may occur. Branching dichotomous with ocassional anastomosis. Initial growth form is a branchless column. First dichotomous division occurs at around 5 cm height. Branches round to slightly elliptical in cross section, with larger axis generally parallel to plane of growth. Largest basal fragment 3.2 x 3.0 cm wide in cross section, whereas thinnest branches may measure only 7 mm. Branches round-tipped so that at an incipient dichotomic division new ones resemble lobes ( Fig. 12a View FIGURE 12 ). No lateral branchlets, only apical division, so decrease in diameter from main to secondary branches is gradual. Some colonies grow attached to small rocks through non-expansive base and new coenosteum may form over dead one.

Branches smooth and spineless, although some specimens may bear a more granulate apical zone. Coenosteum white and porous, with a rudimentary texture under SEM. Coenosteal strips 25–60 µm wide, lack granules or platelets, and form reticulate pattern.

Pores of two kinds: round ones and irregularly-shaped ones. Larger round pores are gastropores and smaller ones are dactylopores ( Fig. 17e, c View FIGURE 17 ). Irregular pores are the openings of efferent ducts, variable in size ( Fig. 17f, c View FIGURE 17 ). All types of pores uniformly distributed on surface of terminal branches, but in thicker branches pores concentrate on anterior face, and in basal branches a considerable section of basal zone may lack pores entirely. Gastropores 0.26–0.66 mm in diameter (average 0.49 mm, n=46, σ=0.09). Gastropore tubes cylindrical, long and axial and curve towards surface of coenosteum in upper section ( Fig. 17b View FIGURE 17 ). Dactylopores 0.16–0.23 mm wide (average 0.19 mm, n=31, σ=0.01). Dactylopore tubes long and axial and curve towards surface like gastropore tubes. Dactylopores slightly raised from surface in apical zone of some specimens, resulting in a rough surface of coenosteum. No tabulae or dactylostyles.

Gastrostyles needle-shaped and almost as long as tube. Gastrostyle illustrated in Fig. 17d View FIGURE 17 is 1.1 mm high and bears longitudinal ridges of short spines fused with each other.

Ampullae elliptical and completely sunken in coenosteum, with larger axis perpendicular to surface ( Fig. 17a View FIGURE 17 ). They may measure up to 1.2 mm x 1.0 mm. Given the size of ampullae and of efferent pores, specimens are probably female.

Discussion. Genus Sporadopora   was originally described by Moseley (1876) as Polypora   based on specimens collected off Mar del Plata in the Challenger expedition, but Moseley (1879) replaced this name by Sporadopora   , since Polypora   was preoccupied for a genus of bryozoans. Cairns (1983a) provided the second record of this species based on specimens from Mavinas Islands, Scotia Arc from Tierra del Fuego to South Georgia and Shetland Islands. The next record is from Río Iglesias et al. (2012) based on specimens from Patagonia from 42° S to 48° S within a depth range of 200–1500 m (specific depth not informed). The present work provides the fourth record of S. dichotoma   and extends its known bathymetric range of occurence to 2204 m depth.

Dactylopore size range of our specimens is higher than that reported by Cairns (1983a). However, Cairns (1983a) stated that the upper limit of dactylopore size range is unknown and that it may overlap with that of gastropores. Tabulae were not found along the examined gastropore tubes, contrary to what Cairns (1983a) described in some cases. It is probably necessary to examine more material and to use an alternative method of wearing down the gastropore tube wall, since sandpaper may have caused tabulae to dissapear in the examined fragments. Despite these differences, specimens coincide with S. dichotoma   in growth form, coenosteal texture, pore types and shapes, gastropore and dactylopore tube shape and ampullae characteristics.

Kingdom

Animalia

Phylum

Cnidaria

Class

Hydrozoa

Order

Anthoathecata

Family

Stylasteridae

Genus

Sporadopora

Loc

Sporadopora dichotoma ( Moseley, 1876 )

Bernal, M. C., Cairns, S. D., Penchaszadeh, P. E. & Lauretta, D. 2021
2021
Loc

Sporadopora dichotoma: Moseley 1879: 429–440

Bax, N. & Cairns, S. D. 2014: 108
Rio Iglesias, J. L. & Acosta & Yepes J. & Cristobo Rodriguez, J. & Martinez Portela, J. & Parra Descalzo, S. & Tel E. & Vinas Dieguez, L. & Munoz Recio, A. & Vilela Perez, R. & Jimenez, E. E. & Ibarrola, T. P. & Rios Lopez, P. & Almon Pazos, B. & Blanco Perez, R. & Murillo Perez, J. & Polonio Povedano, V. & Fernandez Feijoo, J. & Cabanas, J. M. & Gago Pineiro, J. M. & Gonzalez-Nuevo Gonzales, G. & Cabrero Rodriguez, A. & Besada Montenegro, M. V. & Schultze Prado, F. & Franco Hernandez, A. & Bargiela Barros, J. & Garcia Blanco, X. 2012: 191
Zamponi, M. O. 2008: 188
Cairns, S. D. 1991: 44
Cairns, S. D. 1983: 65
Cairns, S. D. 1983: 436
Boschma, H. 1964: 61
Boschma, H. 1957: 60
Moseley, H. N. 1881: 36
Moseley, H. N. 1879: 440
1879
Loc

Polypora dichotoma

Moseley, H. N. 1876: 95
1876