Aplidium meridianum ( Sluiter, 1906 )

Primo, Carmen & Vázquez, Elsa, 2007, Ascidians collected during the Spanish Antarctic expedition CIEMAR 99 / 00 in the Bransfield and Gerlache Straits, Journal of Natural History 41 (29 - 32), pp. 1775-1810 : 1781-1783

Aplidium meridianum ( Sluiter, 1906)

Amaroicum meridianum Sluiter, 1906 .

Aplidium meridianum: Monniot F 1978 ; Monniot and Gaill 1978; Monniot and Monniot 1982, 1983, 1994; Ramos-Esplá et al. 2005.

Distribution

New record: Bransfield Strait (Station B3: three specimens; Station B5: three specimens; Station B6: 15 specimens). Previously recorded: Antarctic continent ( Monniot and Monniot 1983; Ramos-Esplá et al. 2005); South Shetland, South Orkney, and South Georgia Islands ( Monniot and Monniot 1983, 1994; Ramos-Esplá et al. 2005); Kerguelen, Heard and Crozet Islands ( Monniot and Gaill 1978); Magellan Strait ( Monniot and Monniot 1983). From 27 to 1000 m depth.

Description

Colonies from 11 to 46 mm height. The description agrees with that of Monniot and Gaill (1978).

Remarks

Aplidium meridianum was synonymized with several species, although none of these synonymies has been retained ( Monniot F 1978). The most similar species is Aplidium falklandikum Millar 1960 , but the shape of the colony and the arrangement of zooids are different.

Aplidium millari Monniot and Monniot, 1994

( Figure 6 )

Aplidium millari Monniot and Monniot, 1994 ; Ramos-Esplá et al. 2005.

Distribution

New record: Bransfield Strait (Station B5: one specimen; Station B7: two specimens). Previously recorded: Weddell Sea ( Monniot and Monniot 1994); South Shetland Islands ( Ramos-Esplá et al. 2005). From 96 to 407 m depth.

Description

Globular colonies from 17 to 25 mm height ( Figure 6a ) with incrusted sand in the external surface of the test; circular systems hardly visible. Small zooids (6–7 mm) with a six-lobed branchial aperture and a tubular atrial aperture with a simple or slightly lobed languet. The branchial sac is formed by 12–13 rows of stigmata. Asymmetrical stomach with five or six poorly marked longitudinal folds. Short postabdomen (3–4 mm), sometimes with short and numerous vascular processes at the cardiac end. Most zooids are immature, but some of them have cluster-grouped testes in the upper part of the postabdomen ( Figure 6b ).

Remarks

This is the second record of this species since its description by Monniot and Monniot (1994). After re-examining the holotype deposited at the MNHN (registration number A1 APL.B 295), we can conclude that our specimens are juvenile colonies of this species. Although colonies (17–25 mm versus 45 mm height) and zooids (6–7 mm versus 11 mm length) are shorter, they agree in several significant characters: tunic, systems, cloacal languet, number of rows of stigmata and gonads. Some differences from the holotype (pink soft cushion-shaped colonies, six to seven incomplete stomach folds) may be attributed to the juvenile condition of our specimens. The most important difference is the lack in our specimens of parastigmatic vessels, which may be due to the great contraction of the branchial sac and/or the state of development of the zooids .

Figures

Figure 6. Aplidium millari. (a) Colony; (b) young specimen.