Observations on non-didemnid ascidians from Australian waters (1)
Author
Kott, Patricia
text
Journal of Natural History
2006
2006-04-26
40
3 - 4
169
234
http://dx.doi.org/10.1080/00222930600621601
journal article
10.1080/00222930600621601
1464-5262
5232431
Distaplia florida
Kott, 1990
(
Figure 8G
)
Distaplia florida
Kott 1990a
, p 118
.
Distribution
Previously
recorded (see
Kott 1990a
):
South Australia
(
Great Australian Bight
);
Victoria
(
King I.
);
New South Wales
(
Byron Bay
).
New
records:
Victoria
(
Flinders Pier
,
QM
G308566
)
;
Tasmania
(
Tasman Peninsula
,
15–18 m
,
SAM
E3293
;
Port Davey
,
6–8 m
,
SAM
E3233
)
.
Description
Colonies are soft, hemispherical or cushion-shaped (up to
3 cm
diameter) to flat encrusting sheets with circular to elongate systems of zooids around large circular common cloacal apertures, about
5 mm
apart. They are beige in preservative, and minute crystalline particles in the test give it a cloudy appearance. In the preserved specimens, radial furrows around the common cloacal apertures may be the result of preservation and/or contraction. A shallow concavity in the surface over each circular common cloacal cavity has its margin overhung by the surrounding surface test. Branchial apertures open beneath this overhang. The atrial apertures are large sessile openings around the common cloacal cavity with their anterior lips extending out into the margin of the common cloacal aperture. Black faecal pellets in the base of the circular common cloacal cavities are conspicuous from the surface. About 10 zooids surround each common cloacal cavity.
Zooids have a long oesophageal neck, a smooth stomach wall and gonads in the gut loop. Four rows of about 25 stigmata are each crossed by a parastigmatic vessel. A vegetative stolon projects into the base of the colony.
Remarks
Species of
Distaplia
are difficult to distinguish from one another, often having circular systems and soft cloudy test like the present one. The presence or absence of a posterior abdomen is a useful character but, when zooids are immature as in the present case, the smooth stomach wall helps to distinguish this species from others in which it is folded. The concavities over each common cloacal cavity in the preserved specimens appear to be characteristic of this species, although both species have circular systems, smooth stomachs and gonads in the gut loop. The present species is distinguished from
Distaplia viridis
Kott, 1957
by the more numerous branchial stigmata, and by its colour.