Aplidium breviventer

Aplidium breviventer

The peach-coloured colonies are soft, lobed, veryinflated underwater. The common
cloacal apertures protrude in chimneys at the cloacal channel crossings. These channels are visible from the colony surface, as the tunic above them is transparent. The zooids are irregularly lined up along these channels.
The zooids have a wide thorax, a short abdomen that is narrower than the thorax, and a short
post-abdomen separated by a narrow sectionbelow the bottom of the gut loop. The oral
siphon has six small lobes. The cloacal aperture iswide, opening the branchial sac from the second
to the fourth stigmata row. The languet is large and clearly planted above the rim of the
cloacal siphon. There are 12 short and stout tentacles in two orders. The branchial sac has nine to
ten rows of stigmata, which are not interrupted on the dorsal line. There are at least 25 stigmata
in a row on each side. The most posterior rapheal languets are much displaced on the left side. The
thoracic muscles are thinly spaced bundles, of a sinuous design and often anastomosed.

The thorax narrows abruptly behind the branchial sac and the oesophagus opening proj-
ects inside the branchial cavity. The oesophagus is extremely short. The spherical stomach has an
irregularly folded wall, in some zooids with almost entire longitudinal ridges, while
in others the folds are so cut in pieces that the stomach seems areolated. A transverse
section shows 20 to 24 folds. The post-stomach and mid-intestine are very short. The anus opens
at the level of the fifth or sixth stigmata row. The post-abdomen is no longer than
the thorax when the gonads are fully developed. It begins with a short and narrow segment and
progressively widens. The testis follicles number about 50 in a cluster placed against and behind
the ovary. The gonads leave only restricted space for the terminal heart.
Five to six larvae are incubated inside the wide cloacal cavity. The most advanced ones have
already an uncoiled tail and a thick tunic. The spherical trunk measures 0.9 mm in diameter;
four rows of numerous stigmata are clearly visible. The three adhesive papillae are
well-spaced on long, thin stems. Round ampullae are distributed in four anterior median
groups alternating with the adhesive papillae. There are also two or three of these ampullae on
the posterior ventral side of the larvae. The tail does not exceed half a turn around the
trunk.

Occurrence:
Central Pazific, Indonesia, Java, Western Pacific Ocean
Size:
up to 3.94" (10 cm)
Taxonomy
KingdomAnimalia
DivisionChordata
ClassAscidiacea
OrderAplousobranchia
FamilyPolyclinidae
GenusAplidium
SpeciesAplidium breviventer
Photographed in
Indonesia