Stylasterids (Hydrozoa: Stylasteridae) from Mar del Plata submarine canyon and adjacent area (southwestern Atlantic), with a key to the species off Argentina
Author
Bernal, M. C.
Museo Argentino de Ciencias Naturales “ Bernardino Rivadavia ” - CONICET-Av. Ángel Gallardo 470, C 1405 DJR, Buenos Aires, Argentina
Author
Cairns, S. D.
0000-0001-7209-9271
Department of Invertebrate Zoology, Smithsonian Institution- 10 th St. & Constitution Ave. NW, Washington DC, 20560 USA cairnss @ si. edu; http: // orcid. org / 0000 - 0001 - 7209 - 9271
cairnss@si.edu
Author
Penchaszadeh, P. E.
0000-0002-2043-8814
Museo Argentino de Ciencias Naturales “ Bernardino Rivadavia ” - CONICET-Av. Ángel Gallardo 470, C 1405 DJR, Buenos Aires, Argentina & pablopench @ gmail. com; https: // orcid. org / 0000 - 0002 - 2043 - 8814
pablopench@gmail.com
Author
Lauretta, D.
0000-0001-5344-2425
Museo Argentino de Ciencias Naturales “ Bernardino Rivadavia ” - CONICET-Av. Ángel Gallardo 470, C 1405 DJR, Buenos Aires, Argentina & dlauretta @ gmail. com; http: // orcid. org / 0000 - 0001 - 5344 - 2425
dlauretta@gmail.com
text
Zootaxa
2021
2021-05-12
4969
3
401
452
journal article
6481
10.11646/zootaxa.4969.3.1
ea7a5aa0-0ce5-48f3-bebc-bae40df09c91
1175-5326
4751258
140804AC-7852-46F4-811D-3D86F4AA1130
Errinopsis reticulum
Broch, 1951a
(
Fig. 12b
;
Fig. 13
)
Errinopsis reticulum
Broch 1951a: 37–41
, pl. 2, fig. 2, pl. 3, figs. 1, 2, text figs. 3–7;
Boschma 1957: 59
;
Boschma 1966: 117
;
Lowe 1967: 93–95
, pl. 8, fig. a, text figs 14a–c;
Boschma & Lowe 1969: 15
, pl. 5, map 4;
Cairns 1983a: 78–80
, figs.
1g
–h, 9a–h, map 3;
Cairns 1983b: 428
, 457–458, figs. 10a–h, 502, fig. 27c; Cairns & Macintryre 1992: 98, table 1;
Río Iglesias
et al
. 2012: 191
;
Bax & Cairns 2014: 108–110
, table 1, map 6
Distribution.
Patagonia,
42° S
to
48° S
; area between Tierra del Fuego, Burdwood Bank and
Malvinas
Islands,
250–
771 m
.
New record off Mar del Plata,
854 m
.
Material examined.
USNM 1099407
off
Burdwood Bank
,
Lawrence M.
Gould
St.
8 (
54° 22.9’ S
,
61° 53.0’ W
);
MACN-In 40645 off
Mar del Plata
,
Argentina
, St. 11 (
37° 59.258’ S
,
54° 41.436’ W
),
854 m
,
August 2012
.
Description.
Uniplanar growth. Branch anastomosis frequent and regular, producing fenestrate fans. Two main fans fuse at base, resulting in a basket-shaped colony. Secondary, more fragile fans grow between them, more or less transverse to them. (
Fig. 12b
). Branches rectangular to elliptical in cross section, with larger axis transverse to plane of fan and width relation of up to 1:4 between axis. Thickest branch, measured at base where main fans fuse, is 7.3 x 5.0 mm wide. New branchlets may measure down to 1.0 mm. Fenestrae variable in size and shape (
Fig. 13a
).
Cenosteum compact, grey and eroded, smooth on posterior side of main fans. Coenosteal strips
36–74 µm
wide and poorly granular, placed longitudinally along branches where linear slits are present (
Fig. 13c
). In more eroded parts of colony slits are reduced to pores and strips are poorly defined.
Gastropores round,
0.26–0.46 mm
wide (average
0.38 mm
, n=18, σ=0.05), more or less aligned at anterior and antero-lateral face of branches, mainly at the latter (
Fig. 13d
). Gastropore tube short and peripheral (
Fig. 13b
). Basal two-thirds of tube consist of cylindrical chamber rounded at the top, which encompasses almost entire gastrostyle. At level of gastrostyle tip, tube constricts considerably into an upper cylindrical chamber. Gastrostyle in
Fig. 13b
spindle-shaped,
0.37 mm
tall and
0.14 mm
in maximum width (H:W=2.6). Although eroded, vertical ridges of spines are distinguishable. Gastrostyle in
Fig. 13e
more elongate, (H:W=2) and bears blunt spines fused with each other in horizontal layers.
Dactylopores of
two types
: those round,
40–60 µm
wide and raised on mounds and those surrounded by a Ushaped spine. They are distributed in all surfaces of branches, although less frequent at posterior side. Only one Ushaped spine, with a dactylotome around
67 µm
wide, was identified under a dissecting microscope in a less eroded zone of colony. Anterior and antero-lateral sides of branches bear rounded porous stumps which may be eroded bases of dactylopore spines, approximately as wide as gastropores.
Ampullae spherical, total or partially sunken in coenosteum, and up to
1.1 mm
in external diameter. Sex unknown. The silhouette of a scapellid barnacle attached to one of branches was identified, completely covered in coenosteum.
Discussion.
Errinopsis reticulum
was originally described by
Broch (1951a)
based on specimens collected off South of
Malvinas
Islands at 200 and
267 m
depth. The next records were from
Cairns (1983a)
in
Malvinas
, Burdwood Bank and Tierra del Fuego.
Cairns (1983b)
differs with
Broch (1951a)
in the description of dactylopore spines, stating that there are
two types
: the low, round ones with an apical pore (dactylopores on mounds) and the long, conical spines with a slit on one side, in contrast with
Broch (1951a)
, who states there is no dimorphism, that long spines derive from low ones with an apical pore, and that there are intermediate forms of spine as evidence of this hypothesis. The specimen from off Mar del Plata has both
types
of dactylopore and coincides with
Errinopsis reticulum
in growth and branching form, pore arrangement, gastrostyle and gastropore tube characteristics and in its robustness. Slitted dactylopore spines were not analyzed since most of them were worn. The specimen differs with material described by
Cairns (1983a)
in coenosteum color, which he described as bright orange to pink but is mainly grey or pale orange in the Mar del Plata specimen. Gastropores and dactylopores are wider than those reported by
Cairns (1983a)
. The faded color, larger pore diameter and lack of almost all U-shaped dactylopore spines in specimen from Mar del Plata are probably due to erosion. It was probably already dead when collected, since it was mostly covered by a layer of sponge and material in decay.
Río Iglesias
et al
. (2012)
reported a new record of this species since Cairns and Macintryre (1992) based on specimens from Patagonia from
42° S
to
48° S
within a depth range of
200–1500 m
(specific depth not stated).
Bax and Cairns (2014)
mentioned the occurence of
E. reticulum
in
South Georgia
and Cape Horn, but hitherto the descriptions and specific locations of these specimens have not been published. This new record off Mar del Plata extends the known distribution of
E. reticulum
within SWA.