Two tropical species of Stephanotheca (Bryozoa, Cheilostomata, Lanceoporidae) from the Gulf of Carpentaria, Australia
Author
Cumming, Robyn L.
text
Zootaxa
2015
3948
2
279
286
journal article
10.11646/zootaxa.3948.2.8
3d3c7ad3-5b3c-4a1e-9ac7-c3d5691b6db0
1175-5326
240503
C7BFCECE-7296-49A4-8331-3C78645850A5
Stephanotheca romajoyae
n. sp.
(
Figure 2
,
Table 2
)
Material examined.
Holotype
: MTQ G26769, Bryomol Reef,
16°32.658' S
,
139°53.567' E
,
33 m
.
Paratypes
: MTQ G26770, MTQ G26771, MTQ G26772, same data as for
holotype
; MTQ G26773, southeastern GoC,
16°40.914' S
,
140°12.029' E
,
33 m
.
Etymology.
Named for the author’s mother, Mrs Roma Joy Cumming.
Description.
Colony encrusting, with frontal budding; autozooids irregularly polygonal, variable in size and shape (average 0.4 ×
0.4 mm
;
Table 2
), especially variable in width (s.d. 0.117); frontal shield flattened to slightly convex; pseudopores round, irregularly spaced (c.
0.012 mm
diameter), most separated by more than the width of a pseudopore but some close together and sharing depressions or pits (average 47 per zooid), extending to zooid margins; interzooidal boundaries marked by sutural walls and regularly spaced, oval or round sutural pores that are larger than pseudopores in the frontal shield.
TABLE 2.
Measurements (mm) and counts for
Stephanotheca romajoyae
n. sp.
holotype (MTQ G26769).
| Mean |
Standard deviation |
Range |
N |
| Zooid length |
0.373 |
0.042 |
0.299–0.470 |
20 |
| Zooid width |
0.363 |
0.117 |
0.243–0.796 |
20 |
| Autozooid orifice length |
0.087 |
0.005 |
0.075–0.094 |
17 |
| Autozooid orifice width |
0.103 |
0.005 |
0.096–0.112 |
17 |
| Small adventitious avicularium length |
0.092 |
0.011 |
0.080–0.114 |
20 |
| Small adventitious avicularium width at crossbar |
0.040 |
0.004 |
0.034–0.048 |
20 |
| Large adventitious avicularium length |
0.283 |
0.009 |
0.276–0.289 |
2 |
| Large adventitious avicularium width at crossbar |
0.074 |
0.005 |
0.071–0.078 |
2 |
| Diameter of pseudopores in frontal shield |
0.012 |
0.002 |
0.008–0.015 |
20 |
| Number of pseudopores in frontal shield |
47 |
10.75 |
35–70 |
20 |
| Ooecium length |
0.392 |
0.014 |
0.369–0.406 |
5 |
| Ooecium width |
0.302 |
0.027 |
0.276–0.332 |
4 |
| Ooecium height |
0.057 |
0.023 |
0.041–0.073 |
2 |
| Ovicellate orifice length |
0.107 |
0.012 |
0.099–0.116 |
2 |
| Ovicellate orifice width |
0.140 |
0.004 |
0.135–0.144 |
4 |
FIGURE 2.
Stephanotheca romajoyae
n. sp.
holotype (MTQ G26769):
A
, general view with autozooids and ovicellate zooids; note dimorphic orifices, additional avicularia on some zooids, and irregularly spaced pseudopores, some sharing pits (see zooid lower centre with large avicularium);
B
, primary orifice;
C
, orificial condyle; note serrations;
D
, ooecium; note ring of nodules and irregularly shaped pseudopores;
E
, large adventitious avicularium (scale bar 50 µm);
F
, small adventitious avicularium (scale bar 20 µm);
G
, autozooids; note unusual proximolaterally directed avicularia, and autozooid with two avicularia.
Primary orifice wider than long (c. 0.09 long × 0.10 wide mm), broadest centrally; anter rounded; lunula extends to lateral margins and appears continuous with condyles; sinus a shallow arc; condyles large, rounded, serrate; a raised nodular thickening proximal to orifice.
Adventitious avicularia dimorphic in size, shape and position; usually one per zooid, occasionally two; smaller
type
common (c. 0.09 long × 0.04 wide mm at crossbar); subtriangular; widest proximally; proximal opesia semicircular, rostral foramen trifoliate to rounded triangular; crossbar complete; usually suboral, medial, directed distolaterally; sometimes with slight asymmetry, curving towards orifice; occasionally directed proximolaterally or positioned in a distolateral corner; occasional second avicularium positioned more proximally with variable orientation; larger
type
uncommon, occupying most of frontal shield (c. 0.28 long × 0.07 wide mm at crossbar); elongate oval with parallel sides; proximal opesia oval, rostral foramen rounded subtriangular with concave sides; crossbar complete; usually proximal, medial, directed distolaterally, terminating in a distolateral angle; vicarious avicularia absent.
Ovicell hyperstomial (prominent), recumbent on frontal shield of distal zooid; ooecium longer than wide (c. 0.4 ×
0.3 mm
); flattened frontally; with numerous pseudopores of variable shape and size, larger than those of frontal shield; an arch of nodules surrounding the pseudopores, terminating laterally; walls almost vertical, imperforate (height c.
0.06 mm
); orifice dimorphic, ovicellate orifice longer (c. 0.11 vs.
0.09 mm
) and much wider (c. 0.14 vs.
0.10 mm
;
Table 2
) than autozooidal orifice (1-tailed t-test: p<0.001).
Remarks.
The variability in avicularium size, shape, position and orientation sets
Stephanotheca romajoyae
n. sp.
apart from all other
Stephanotheca
species. The nine temperate species described by
Reverter-Gil
et al.
2012
all have a single, medial, proximally directed adventitious avicularium. While
S. romajoyae
n. sp.
also has a medial avicularium on each zooid, these vary in orientation from distolateral to proximolateral, there are also occasional additional avicularia elsewhere on the zooid, and occasional large elongate-oval avicularia that occupy most of the frontal shield. Sometimes the two different avicularium
types
occur together on a single zooid (
Figure 2
A).
Stephanotheca ipsum
n. sp.
is the only other
Stephanotheca
species with more than one avicularium on some zooids, but they are a distinctly different shape and are not dimorphic.
Stephanotheca ochracea
(
Hincks, 1862
)
is the only other species with dimorphic adventitious avicularia, but they are a different shape and proximally directed.
The level of variability in the avicularia of
Stephanotheca romajoyae
n. sp.
resembles that of
Calyptotheca australis
(
Haswell, 1880
)
in the dimorphism, the variable orientation and in sometimes being slightly asymmetrical and curved around the orifice (see
Cumming & Tilbrook 2014
). These two species also share similar small orifices of the same dimensions (c. 0.09 ×
0.10 mm
) and large, serrate condyles. The ooecia of the two species are clearly different (those of
C. australis
are fully pseudoporous), but colonies without ovicells are readily distinguished by the much shallower sinus in
S. romajoyae
, avicularium shape and colony form. The small avicularia of
S. romajoyae
are subtriangular and widest proximally, whereas those of
C. australis
are narrowly triangular proximally and usually widest midlength. The large avicularia of
C. australis
are also narrowly triangular proximally, whereas those of
S. romajoyae
are elongate oval with parallel sides. The growth form of
C. australis
is a network of unilaminar tubes, whereas
S. romajoyae
is an encrusting species.
Stephanotheca romajoyae
n. sp.
has the smallest orifice of the
Stephanotheca
species (0.09 ×
0.10 mm
), followed closely by
S. ipsum
n. sp.
(0.10 ×
0.10 mm
). The southern Australian species
S. ambita
and
S. victoriensis
also have smaller orifices than the European species (0.11 ×
0.11 mm
, 0.11 ×
0.13 mm
respectively vs 0.12–0.15 ×
0.13–0.15 mm
).
Stephanotheca ambita
shares with
S. romajoyae
n. sp.
a wide shallow sinus, but it has smooth rather than serrate condyles and a single, small, oval suboral avicularium.
Stephanotheca victoriensis
has a larger, wider, distinctly oval orifice, and a single oval avicularium distant from the orifice and almost in the centre of the zooid.
Orificial dimorphism occurs in all
Stephanotheca
species except
S. perforata
(0.15 vs
0.15 mm
;
Reverter-Gil
et al.
2012
), but is most pronounced in
S. romajoyae
n. sp.
, with ovicellate orifices much wider than autozooidal orifices (0.14 vs.
0.10 mm
). The ooecia of
S. romajoyae
differ from those of all known
Stephanotheca
species in being longer than wide. Ooecia of the Australian species differ in various ways from the typical crowned ooecium of the European species: those of
S. ipsum
n. sp.
are ridged, those of
S. victoriensis
have a single row of pseudopores forming an arch and those of
S. ambita
have a relatively large perforated area and smaller, lower nodular rim of calcification.
S. romajoyae
ooecia are most similar to those of
S. ambita
, with a similarly wide perforated area.
Distribution.
Stephanotheca romajoyae
n. sp.
is known only from the GoC, with four colonies collected from the same site at Bryomol Reef, east of Mornington Island at
33 m
, and a fifth colony from southeastern GoC at
33 m
.