Polyclinidae

Monniot, Françoise, Dettai, Agnès, Eleaume, Marc, Cruaud, Corinne & Ameziane, Nadia, 2011, Antarctic Ascidians (Tunicata) of the French-Australian survey CEAMARC in Terre Adélie, Zootaxa 2817, pp. 1-54 : 10-17

Polyclinidae

Aplidium balleniae Monniot & Monniot, 1983 ( Figure 4)

Monniot & Monniot, 1983: 13 fig. 2B, C, D. Primo & Vazquez 2007: 1777 fig. 2. Stations: 5-12-14-22 -61.

One or several elongated lobes are united at their base. Each lobe is composed of a thick short peduncle and a softer head ( Fig. 4). The tunic is encrusted with fine sand, but allows seeing long double rows of zooids. The common cloacal openings are apical but some can also be found on the lateral sides of the lobes. It is difficult to extract the zooids from the resistant vitreous tunic containing thin mineral particles. The oral siphon has 6 lobes. The atrial opening is wide; it begins at the level of the 3th or 4th stigmata row to end at half-length of the thorax. The languet with 3 teeth is longer near the common cloacal aperture. The branchial sac has 18 to 22 rows of 10 stigmata on each side. The 5 stomach folds are not well marked; an annular post-stomach is followed by a short segment of intestine which forms the bottom of the digestive loop. The zooids have very long post-abdomens. Almost all colonies are immature. When present the testis vesicles have each a separate sperm duct joining the common duct at some distance, as previously noted in the description of the type specimen. No ovaries and no larvae have been found.

Sequences were obtained for specimens A1 APL.B 527 (BOLD: ASCAN006-10) and A1 APL.B 525 (BOLD: ASCAN005-10) with 2.46% divergence between the two. Investigation with additional specimens and markers of whether this represents an intraspecific divergence would be interesting. No close hit in BOLD (best: 81%).

The distribution of Aplidium balleniae is strictly Antarctic but wide: Balleny Islands, Ross sea, Antarctic Peninsula and now Terre Adélie, from 150 to 600 m depth.

Aplidium falklandicum Millar, 1960 ( Figure 5)

Millar, 1960: 34 Fig. 3 . Monniot & Gaill 1978: 142 Fig. 1 D. Monniot & Monniot 1983: 15 and synonymy. Tatian et al. 2005: 207. Sanamyan, Schories & Sanamyan 2010:59 fig. 2A.

Stations (events when several trawling operations per station): 2-5-11 (429)-12-13A-18-27(33)-30(66)-35-50A-57- 86E.

The colonies in a single or multiple lobes are soft with some sand included in the surface tunic, mostly at the base of the colony. Internally the tunic is vitreous without sediment. The zooids are dense and parallel. The atrial aperture, opposite to the first branchial stigmata row, has a wide languet with a round tip. The zooids only have 14 to 16 rows of stigmata. The white triangular organ at the base of the thorax described by Millar (1960) was not found. The stomach is highly variable in zooids of a same colony, either with 5 longitudinal folds or with an almost smooth wall. The ovary is anterior to a long series of testis vesicles. The post-abdomen extends far beyond the gonad level. Two or 3 larvae are incubated in the peribranchial cavity. The elongated trunk measures 1.1 to 1.2 mm ( Fig.5), and has 3 adhesive organs alternating with 4 finger-like papillae and circled at their base by 4 vesicles on each side. Dorsally and ventrally are linear series of ampullae (as figured by Sanamyan & al 2010 fig. 2A).

One sequence for specimen A1 APL.B 531 (BOLD: ASCAN007-10). Closest hit in BOLD: Aplidium meridianum ASCAN008-10 and ASCAN009-10 (92.5%).

A. falklandicum differs from other Antarctic Aplidium species by its soft clear colonies, very muscular thoraces with an average of 15 stigmata rows and the larval shape. It has a wide Antarctic and Sub-Antarctic distribution and a large depth range from the infra-littoral to 800 m in Terre Adélie.

Aplidium meridianum ( Sluiter, 1906) ( Figure 6 )

Amaroucium meridianum, Sluiter, 1906: 15 pl.1 fig.12. Aplidium meridianum: Monniot F. 1978: 4 fig. 1 A. Monniot & Gaill 1978: 146 fig. 5 A. Monniot & Monniot 1982: 101. Monniot & Monniot 1983: 22 pl. 2 f-g.

Stations (events when several trawling operations per station): 10-13A-20-21-22-28-30(66)-31

The colonies have a characteristic appearance ( Fig. 6 ) although they are always damaged by trawls: they are arranged in large soft cushions on a wide base encrusted with sand, with a dark brown upper part, very mucous, and often in shreds. The zooid arrangement could not be detected from the colony surface. The zooids reach 2 cm in length with a long post-abdomen. The thorax is muscular with 6 pointed oral lobes and a simple thick atrial languet. An average of 20 stigmata rows were counted in the less contracted zooids. The stomach has 5 longitudinal folds and is followed by an inflated post-stomach. The ovary lies at some distance from the digestive loop. The testis vesicles are aligned along the anterior part of the post-abdomen behind the ovary. The common sperm duct is thick along the abdomen in all zooids of the collection. The larva is similar to those of Aplidium falklandicum , and figured in Monniot and Gaill (1978 Fig. 5 A) with a trunk measuring 1.1 mm long. A. meridianum has few distinctive characters except the dark and mucous colonies.

Two identical sequences for specimen A1 APL.B 538 (BOLD: ASCAN009-10) and specimen A1 APL.B 537 (BOLD: ASCAN008-10). Closest hit in BOLD: see A. falklandicum .

It is widely distributed in Antarctic and Sub-Antarctic regions down to 1500 m depth.

Aplidium siderum Monniot & Monniot, 1983 ( Figure 7 )

Monniot & Monniot, 1983: 28 fig. 5C–E, pl. 2 I –J.

Station: 14

A single spherical colony was collected at 168 m depth. The zooids are arranged in obvious circular systems, as the oral siphons open in a clear area of the surface test. Resistant at the upper layer with some fine particles embedded, the tunic becomes soft and gelatinous internally.. The zooids are very long but remain in the upper part of the colony. The oral aperture has 6 lobes; the atrial languet is long ( Fig. 7 A). The branchial sac has 22 rows of few stigmata leaving an imperforated space near the endostyle. The stomach has 5 folds. The rectum begins with a caecum taking place posteriorly to the intestinal curve ( Fig. 7 A, B). The long post-abdomen contains an ovary distant from the abdomen and followed by spaced testis follicles ( Fig. 7 C). No larvae were found in this colony.

This species is recorded here for the second time. Previously recorded from the Antarctic Peninsula, 73– 128 m.

Ritterella mirifica Monniot & Monniot, 1983 ( Figure 8)

Monniot & Monniot, 1983: 34 fig. 6 ABCD, pl. 3 F. Primo & Vazquez 2007: 1786 fig 9.

Station: 16A.

Three colonies have been collected from a single station at 625 m depth. The less damaged one is conical 23 mm long and 17mm in diameter ( Fig. 8). The oral siphon has 6 lobes. The rim of the atrial aperture is cut in languets. The branchial sac has 10 rows of stigmata without parastigmatic vessels or papillae. The gut is very short. The smooth stomach wall sometimes shows longitudinal ridges due to contraction. The long post-abdomen extends far into the base of the colony. Numerous testis vesicles are gathered in a cluster in the anterior part of the post-abdomen and the ovary is included inside this testis bunch. Immature larvae are incubated in the peribranchial cavity: they have 3 well separated adhesive papillae circled by a continuous line of vesicles. The neural vesicle contains a single sensory organite.

Previously recorded from the Antarctic Peninsula and the Ross Sea from 142 to 365 m, the new record from Terre Adélie at 625 m widely extends both its geographic and bathymetric range.

Synoicum adareanum ( Herdman, 1902) ( Figure 9A )

Polyclinum adareanum, Herdman, 1902: 195 pl. 22, fig. 1–9. Synoicum adareanum: Monniot & Monniot 1983: 31 . Tatian et al. 2005: 208 and synonymy. Primo & Vazquez 2007: 1787.

Stations (events when several trawling operations per station): 1-2-3-5-7- 8 -9-10-11(424)-11(429)-12-13A-14-17- 20-21-22-26A-27(45)-39-50A-61.

This species has either a single or several pedunculate lobes starting from a common base ( Fig. 9A ). The head contains the thoraces of the zooids, the abdomens and post-abdomens are included inside the harder tunic of the peduncle. The oral apertures are in obvious circular systems at the top side of the colony. Synoicum adareanum is very common in the whole Antarctic and Sub-Antarctic areas and lives in abundant populations. It may be confused with Synoicum ostentor Monniot & Monniot, 1983 which has the same colony shape. However, Synoicum ostentor has a sandy and harder peduncle and zooids with many more stigmata rows in the branchial sac.

Sequences were obtained from specimens A1 SYN 107a (BOLD: ASCAN011-10) and A1 SYN 108a (BOLD: ASCAN010-10). Sequence divergence is 0.52%. No close hit in BOLD (best: 84%).

Synoicum ostentor Monniot & Monniot, 1983 ( Figure 9 B)

Monniot & Monniot, 1983: 33 fig. 5G, H, I, pl. 2 C. Primo & Vazquez 2007: 1789.

Stations (events when several trawling operations per station): 1- 2 -3-7-8-35-36(297)-39-52-79.

The colonies are arranged in a single or several lobes. They are composed of a soft clear head on a stiff opaque peduncle ( Fig. 9 B). The cylindrical peduncle has embedded sand and its external wall is horizontally wrinkled. The zooids are arranged in circular systems clearly visible at the top of the head. The anatomy of the CEAMARC specimens corresponds well to the original description. The largest colony lobe is 14.5cm high. The thoraces are long with an average of 22 rows of stigmata, even in small colonies. Some post-abdomens reach 5.5 cm in length.

This species has an Antarctic distribution from the South Orkney Islands, Balleny Islands and Wilkes Land. Its deepest record in Terre Adélie is 800 m.

Figures

FIGURE 1. Ascidiacea stations and bathymetry over the George V and Terre Adélie Shelf. The bathymetry grid has a 250 m grid pixel resolution over the shelf (Beaman 2008).

FIGURE 3. Polysyncraton trivolutum. A, larva, scale bar = 1 mm; B, colonies.

FIGURE 6. Aplidium meridianum, colony, scale bar = 2.5 cm.

FIGURE 7. Aplidium siderum. A, thorax and abdomen of a zooid; B, abdomen of another zooid; C, gonads. Scale bar = 1 mm.

FIGURE 9. A, Synoicum adareanum. B, Synoicum ostentor. Scale bars: A = 3 cm; B = 5 cm.