Aplidium eudistomum, Kott, 2008

Kott, Patricia, 2008, Ascidiacea (Tunicata) from deep waters of the continental shelf of Western Australia, Journal of Natural History 42 (15 - 16), pp. 1103-1217 : 1155-1156

Aplidium eudistomum sp. nov.

( Figures 8C–E )

Distribution

Type locality: Western Australia CSIRO SS10 / 05 (Albany, Stn 26, 118.3410E 35.3397S, 212 m, 23.11.05, holotype WAM Z27519 ; paratypes QM G328439 ? Kalbarri, Stn 102, 96– 98 m, 05.12.05, QM G328453 ) .

Description

The type material consists of a series of almost identical vertical stumpy finger-like lobes, to about 3 cm high and about 1 cm diameter throughout. Sand is present in the lower half of the colony but there is very little sand in the firm test of the upper half of the colony. Zooids open all around the upper half of the colony and converge into the centre and down into the stalk. A terminal common cloacal aperture is on the top of each colony and small, narrow common cloacal canals were detected extending down the sides of the colony. Zooids are small and muscular. A small atrial lip projects from just in front of the small atrial siphon, although when zooids are contracted it appears to be part of the anterior rim of the opening. Branchial stigmata are in 12 rows, although the number in each row could not be counted. The stomach is small and its wall has eight parallel rounded folds. The posterior abdomen is long, even in the contracted zooids.

The specimen (QM G328453) from Kalbarri, questionably assigned to this species, is damaged. Although it has the characters of the type material from Albany except that the terminal common cloacal aperture cannot be seen, many of the zooids are withdrawn into the base of the colony and the stomach appears to have only five folds rather than the eight of the type material.

Remarks

These small vertical lobes are different from the large massive colonies of most of the Aplidium spp. in this collection. Generally they resemble some species of Eudistoma . The species can be identified by the arrangement of its zooids that seems to represent a single cloacal system with its terminal common cloacal aperture and its zooids with eight stomach folds. It resembles Aplidium constrictum (Sluiter, 1900) from the sub- Antarctic Chatham I. The type locality of Sluiter’s species does not preclude the present specimens from Albany from conspecificity, although Sluiter’s species does not have the embedded sand. Van Name (1918) and Tokioka (1967) assigned to this species sandy specimens from the Philippines and the Palau Is. respectively. These specimens have similar colonies and similar numbers of rows of stigmata and stomach folds to the present specimens. However, only nine zooids are reported to be in the Philippine material ( Tokioka 1967) and neither these tropical specimens nor A. constrictum (Sluiter, 1900) from Chatham I. appear to be conspecific with either the present colonies from Albany or the one from Kalbarri.

Figures

Figure 8. Aplidium crustum sp. nov. (QM G328107): A, colony surface; B, thorax and abdomen. Aplidium eudistomum sp. nov. (QM G328439): C, colony; D, section through colony showing zooids; E, zooid, showing organs of thorax and abdomen. Scales: A, 1.0 cm; B, E, 0.5mm; C, D, 5.0 mm.