Systematics of some calloporid and lacernid Cheilostomata (Bryozoa) from coastal South Korean waters, with the description of new taxa
Author
Min, Bum Sik
Author
Seo, Ji Eun
Author
Grischenko, Andrei V.
Author
Lee, Sang-Kyu
Author
Gordon, Dennis P.
text
Zootaxa
2017
4226
4
471
486
journal article
37250
10.11646/zootaxa.4226.4.2
0a944aa0-a00e-4de7-aacc-6b2a8c64435c
1175-5326
265083
758449A2-1B82-45E2-B6C4-8D83354C6CA7
Retevirgula asiana
n. sp.
(
Figs 4–7
)
Material examined.
Holotype:
MBRBKSP031, RV
Kuklipgongwon-yeoungu 1
Station
I3
, 34.1585° N, 126.7689° E,
29 July
2016
, 42 m, west of Cheongsan
Island
(Cheongsando).
Etymology.
Derivative of the old Latin name Asia, the region east of Europe.
Description.
Colony encrusting, unilaminar, reticulate, up to
10 mm
in diameter. Autozooids more or less elongate-oval, highly disjunct, arranged in quincunx, with 8–12 tubular connections to adjacent autozooids and/or heterozooids leaving large spaces between them. Gymnocyst most developed proximally, with lateral walls sloping steeply to substratum. Cryptocyst extremely narrow, smooth, the inner margin weakly scalloped between adjacent spine bases. 10–14 articulated periopesial spines, the 4 distalmost spines more erect, the others angled steeply part way across the membranous frontal wall; spine length c. 80–135 µm. Kenozooids mostly subvicarious, occasionally as large as an autozooid, generally abundant, of variable zooidal and opesial size, connected by 7–8 tubes to zooids, with a relatively large circular to subcircular opesia encircled by a smooth cryptocystal shelf; 0–2 frontal spines. Avicularia rare, smaller than and occupying the place of a kenozooid in a subvicarious position, longer than wide, the shape of the rim somewhat like a figure 8 but much less constricted; with elevated rostral rim and large combined foramen, no crossbar or pivot bars. Ooecium not seen. Ancestrula not seen.
Measurements.
ZL 341–479 (375) µm, ZW 169–224 (203) µm; OpL 261–286 (275) µm, OpW 109–154 (141) µm; AvL 70 µm, AvW 56 µm.
Remarks.
This is the first record of a species of
Retevirgula
in Korean
waters.
Mawatari & Mawatari (1980)
, however, illustrated three species of
Retevirgula
in modern Japanese seas. These were all originally described elsewhere, and conspecificity is unlikely owing to differences in geographic and temporal distribution, as well as character differences.
Retevirgula areolata
(
Canu & Bassler, 1923
)
, reported by
Mawatari & Mawatari (1980)
from Shirayama,
Wakayama Prefecture
, Honshu, was originally described from the Pleistocene of
California
.
Subsequently,
Kataoka (1961)
identified it in the Pleistocene of
southern Japan.
Retevirgula periporosa
(
Canu & Bassler, 1928
)
, likewise reported from Shirahama, was originally described from
Cuba
,
Florida
and the Gulf of
Mexico
.
Subsequently,
Hayami (1970)
identified it in the Miocene of
Hokkaido
.
Retevirgula triangulata
(
Silén, 1941
)
, reported by
Mawatari & Mawatari (1980)
from Atami in
Shizuoka prefecture
, Honshu, was originally described from the
Ryukyu (Bonin) Islands
.
Retevirgula asiana
n. sp.
differs from the fossil found in
California
and living
R. areolata
in having slightly fewer spines, a proportionally smaller avicularium, not found distal to an autozooid, more numerous kenozooids and larger interzooidal spaces.
Retevirgula periporosa
from
Cuba
has more spines (16–18) than
R. asiana
(12–14), but other characters appear similar. Based on Silén’s (1941) illustrations and description,
R. triangulata
has a proportionally larger avicularium with a circular rostral/opesial area. Of the mainland records for
Japan
,
R.
periporosa
and
R. triangulata
, both
sensu
Mawatari & Mawatari (1980)
, have similar spine numbers to
R. asiana
and either could be conspecific. Curiously, neither
Mawatari & Mawatari (1980)
nor
Silén (1941)
mentioned interzooidal kenozooids in any of the material they described, though they must presumably have been present; perhaps some were mistaken for avicularia.
FIGURES 4–7.
Retevirgula asiana
n. sp.
, Stn I3 near Cheongsan Island.
4,
Unbleached zooids with periopesial spines; scalebar 400 µm.
5,
Part of a colony with numerous kenozooids and an interzooidal avicularium (arrow); scalebar 200 µm.
6,
Part of a colony showing kenozooids with spine bases and a retained entire spine (arrows); scalebar 400 µm.
7,
Close-up of the avicularium shown in fig. 5; scalebar 50 µm.
In general appearance,
R. asiana
n. sp.
appears closest to
Retevirgula akdenizae
Chimenz, Nicoletti & Boncambi, 1997
, from the Aegean Sea area of
Turkey
, which has a similar-shaped avicularium. This species is the only known
Retevirgula
from the vast area of Europe, Africa and the Indian Ocean and may possibly be an immigrant to the Mediterranean. In spite of its similarity to
R. asiana
, it differs in having larger zooids (mean length 470 µm, mean width 260 µm) with granules on the thin cryptocystal rim; additionally, it has 13–16 periopesial spines that are longer (300–400 µm) than in
R. asiana
. Avicularia are larger and may bear a spine, and the kenozooids have up to six spines.
The attribution of
Retevirgula
to the resurrected family-rank taxon Ellisinidae (
Vigneaux 1949
) is explained by Gordon (in press).
Inter alia
, the ooecium in ellisinid genera is always associated with a heterozooid, either an avicularium or a kenozooid, both ooecial layers are calcified (some species of
Retevirgula
have, however, a small ectooecial foramen), and the zooidal cryptocyst is minimally developed, with no shelf.
Distribution.
Korea
: South Sea;
42 m
depth on rock.