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
Aplidium laticum
sp. nov.
(
Figure 6F, G
)
Distribution
Type locality.
Tasmanian Canyons (38.11482
°
S, 149.3565
°
E, Banks Strait,
168 m
,
25 April 2004
, Sherman sled, species 10,
syntypes
two
QM
G308832
;
King I. Canyon
,
294 m
;
Pieman Canyon
,
176 m
;
Big Horseshoe
,
159 m
)
.
Description
Colonies are sessile globes or cones or stumpy upright lobes, fixed to the substratum by a sandy hold-fast in the centre of the lower surface. The test in all the recorded specimens is soft and almost liquid and the arrangement of the zooids was not determined.
In most of the specimens, the zooids are in vegetative phase, with small, juvenile regenerating thorax and abdomen on a long posterior abdomina. Details of the zooid structure could be determined in only a few zooids in the
syntype
colonies. The zooids are long and thin as in many species in this genus. The atrial tongue arises from the anterior rim of the aperture and the thorax is long and narrow with 18 rows of about 20 stigmata. The abdomen is relatively short with five gastric folds and the posterior abdomen is long and narrow.
Remarks
The almost liquid test of this species is reminiscent of the test of
Pseudodistoma fragilis
Tokioka, 1958
(from
Japan
) and
P. gracile
Kott, 1992a
from the tropical Western Pacific (see
Kott 1992a
). However, the zooids in the
syntype
material are characteristic of the genus
Aplidium
. Although known species often have zooids and even colonies that generally resemble those of the present species, an
Aplidium
species
with its very soft test has not been encountered and the species is not readily assigned to any known Australasian or sub-Antarctic species.