Botryllus tuberatus Ritter & Forsyth, 1917

Monniot, Françoise & Monniot, Claude, 2001, Ascidians from the tropical western Pacific, Zoosystema 23 (2), pp. 201-383 : 313-314

Botryllus tuberatus Ritter & Forsyth, 1917

Botryllus tuberatus Ritter & Forsyth, 1917: 461 . Type locality: California. Synonymy: see Monniot C. & Monniot F. 1987: 104, Polynesia.

MATERIAL EXAMINED. — Philippines. Bohol Sea, Camiguin Island, 9°14.71’N, 124°39.61’E, 10 m, 17.IV.1997 ( MNHN S1 BOT.B 159).

DESCRIPTION

This species is black with small, round systems. It has been collected on Ulva reticulata . This very common ascidian is distributed worldwide.

Botryllus tyreus ( Herdman, 1886) ( Figs 86 ; 126E )

Botrylloides tyreum Herdman, 1886: 344 . Type locality: Philippines. Synonymy: see Monniot C. & Monniot F. 1987: 104, fig. 39D-H, Polynesia.

MATERIAL EXAMINED. — Federated States of Micronesia. Yap, Colonia, main wharf, 9°30.91’N, 138°07.57’E, 7 m, 4. VI.1996 ( MNHN S1 BOT.B 160).

DESCRIPTION

The colonies are massive, lobed, 3 to 4 mm thick. The common cloacal apertures are raised in short chimneys at the junction of several cloacal channels, and this gives the colony a spongy appearance. In life the colonies are beige ( Fig. 126E ); there are darker rings around the oral siphons, while the surface above the cloacal channels is almost white. In formalin preservative the tunic becomes transparent, with reddish zooids and clear vascular ampullae at the periphery of the colony. The buds develop deep in the colony, below the nourishing zooids, and they part very early from the mother zooid.

The cloacal siphon has no languet ( Fig. 86A ). Its size is small compared to that of other Botryllus species , and it sometimes forms a tube. Its rim is even. There are 12 stout oral tentacles of three orders; the longest may extend through the siphon. The prepharyngeal band, in a circle, has a single crest. The dorsal tubercle has a circular opening.

The branchial sac has 12 to 13 rows of stigmata on each side ( Fig. 86A ). The second row is entire and reaches the dorsal lamina. The last row is irregular. The formula on the left side is:

E. 4 V 2-3 V 2-3 V 2 V 6-7 D.L.

The oesophagus is perpendicular to the two last stigmata rows. The stomach is wider in its cardiac part than at its pyloric end. There are about 12 entire protruding stomach folds, which are not dilat- ed anteriorly. The caecum is an inflated ampulla on a long peduncle. The pyloric gland is poorly developed and does not narrow the intestine; its channel opens at the base of the peduncle of the caecum. The long rectum opens at the level of the eighth row of stigmata by an anus with a plain rim. In the nourishing zooids there is a testis on each side ( Fig. 86 ), made of only a few lobes (up to six), located at the level of the two last stigmata rows on the right side, and at the same level or one or two rows ahead on the left side. In some zooids we have found a small larva, 220 µm in diameter and with only one sensory organ, in the right cloacal cavity at the level of the anus. The larva does not distend the body wall. In one of the incubating individuals an oocyte was present anterior to the right side testis.

The first order buds have functional testes. We have not found oocytes in the first order buds, but second order buds have a lateral mass of large undifferentiated cells on each side.

Figures

FIG. 86. — Botryllus tyreus (Herdman, 1886); A, left side of a zooid; B, right gonad. Scale bar: 0.5 mm.

FIG. 126. — A,?Phallusia obesa (Herdman, 1880); B, Phallusia philippinensis Millar, 1975; C, Phallusia sp.; D, Botryllus perspicuus (Herdman, 1886); E, Botryllus tyreus (Herdman, 1886); F, Eusynstyela hartmeyeri Michaelsen, 1904.