Amphicarpa duploplicata ( Sluiter, 1913 )

Monniot, Françoise, 2010, Some new data on tropical western Pacific Ascidians, Zootaxa 2561 (1), pp. 1-29 : 19

Amphicarpa duploplicata ( Sluiter, 1913)

( Figures 20A , 21 )

Stolonica duploplicata Sluiter, 1913:67 pl.6, Figs 4–10 . Monniot C. 1988:185 Fig. 9 ; 1991:9 Fig.2 and synonymy.

Not Kott 1985: 244 fig.118 = Amphicarpa styeliformis .

Material. Coll. N.J. Pilcher et al., Viet Nam, Con Dao isl., Hong Vung Isl., 08°37.78’N – 106°33.34’E, 21m, 05/VIII/2008, 0PHG 1785-X ( MNHN S1 AMP 33 °. Malaysia, Sabah, Mabul Isl. , 4°14.37’N – 118°37.55’E, 17m, 0PHG 1118-X ( MNHN S1 AMP 24 ).

The zooids are tightly pressed against each other to form compact masses ( Fig. 20A ) but are only linked by basal sandy stolons. The tunic is impregnated with sand, except the tip of the siphons of a red-orange colour. The largest individuals are 18mm in height. The internal layer of the tunic is very soft, mucous-like. The body-wall extends into the stolons: it is opaque brown in formalin. The rim of the siphons is not lobed and darker. A large velum closes both siphons. The thin, long, and numerous oral tentacles have brown pigment cells. The peripharyngeal band in two blades is little or not indented around the button-like dorsal tubercle. There is no space between the peripharyngeal band and the branchial tissue. The branchial sac ( Fig. 21C ) has 2 high folds on each side, their height decreasing progressively toward the oesophagus over 19–20 stigmata rows. For one of the specimens the formula is:

E-9- 10 - 6- 12 -4-DL-2- 12 -7- 10 -8-E.

The stigmata are crossed by parastigmatic vessels. The dorsal lamina is prolonged below the oesophageal opening. The branchial sac is attached to the body wall by thin filament on each side of the endostyle and by stronger bridles between the series of endocarps. The gut ( Fig. 21A ) in posterior position, is attached only by a series of strong bridles. The short oesophagus is followed by a round stomach with 10 internal folds on the mesial side. The gut loop is narrow without a gastric caecum and with a long intestine in a straight line. The anus without lobes opens close to the cloacal aperture. The numerous gonads are embedded in the body wall ( Fig. 21B ). Ovaries and testes are separated and do not seem to mature at the same time. The ovaries are in a line parallel to the endostyle with 1 or 2 oocytes; they open by a wide papilla ( Fig 21B ). The testes are very small composed of a single vesicle; the most anterior ones are in a line parallel to the ovaries, but others are scattered over the posterior part of the body. The endocarps have the same distribution in all zooids observed: on each side are 3 parallel lines of 4 to 5 foliated vesicles ( Fig. 21A ). Two endocarps occupy the gut loop. A ring of filiform tentacles are at the base of the cloacal velum and some are scattered on its internal lining. The body wall penetrates into the stolon arising from the posterior left body side

Described at first from Indonesia, A. duploplicata later described from New Caledonia is certainly widely distributed in the Pacific Ocean, but covered with sand the colonies are difficult to see.

Figures

FIGURE 2. A:Trididemnum cyclops. B: Trididemnum lanugineum n. sp. C: Trididemnum biglutinum from New Guinea. D: Trididemnum biglutinum from Palau.

FIGURE 4. Trididemnum lanugineum n. sp.: A: abdomen of a zooid, B: thorax, C: larva. Scale bars: 0.5mm.

FIGURE 9. Didemnum nocturnum: A: thorax, B: abdomen. Scale bar 0.5mm.

FIGURE 20. A: Amphicarpa duploplicata. B: Polycarpa argentata. C: Polycarpa mytiligera. D: Microcosmus exasperatus.

FIGURE 21. Amphicarpa duploplicata: A: body of a zooid, B: part of the posterior left side of the body, scale bar=2mm C: branchial sac.