Comprehensive Description

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General Description

Diagnosis: Live specimens are trumpet-shaped with a white column and moderately short, blunty conical tentacles that are deep red to light pink in colour and lacking aboral thickenings. The column of contracted preserved specimens are smooth and dome-like, with base of diameter 29 - 36 mm and a height of 24 - 30 mm. There is a distal belt of up to 24 cinclides. Tentacles have an abundance of microbasic p-mastigophores and spirocysts. Holotrichs are also present, but not abundant. The mesenteries are hexamerously arranged, with the first two cycles being perfect.

Oral disc and tentacles: The oral disc is flat, with a broad tentacle-free space surrounding a slit-like mouth. The mouth is elevated on a conical hypostome, with two prominent siphonoglyphs. The lips and siphonoglyphs are white in colour, whilst the actinopharynx is pink to red. The distal column covers the oral disc and tentacles in contraction, leaving only the tips of the tentacles visible. There are ca. 100 tentacles in six crowded marginal cycles, with the tentacles in the inner cycles longer than those of the outer cycle. The tentacles are blunt, with a length in contraction less than the radius of the oral disc. In live specimens, the tentacles are pink to red in colour, occasionally white. The tentacles of the inner cycles are typically held erect, whilst those of the outer cycle are held out or pointing towards the substrate. In preserved specimens, the tentacles are the same colour or slightly pinker than the column. The colour differences are more pronounced in live specimens. The longitudinal musculature of the tentacles is ectodermal.

Base and column: In preserved, contracted specimens the column is dome-shaped and smooth, with a height up to 30 mm and a diameter up to 36 mm. In live specimens the column flares slightly from the base. The column is not obviously differentiated into scapulus and scapus, although some specimens have small particles that adhere only to the lower column. There is a distal belt of inconspicuous perforate cinclides in stronger endocoels, which usually number 12 - 24 in number, although over 24 have been counted in one specimen. The colour of the column in preserved specimens is cream to tan, whilst in live specimens have an opaque pale pink column. There is no fosse. The distal edge of the column may extend over the base of the tentacles in contracted specimens. Column musculature is strong, with a strong, long mesogleal marginal sphincter. The sphincter encompasses most of the mesoglea distally and tapers proximally. It is closer to the gastrodermis than to the epidermis with many large lacunae. The pedal disc is adherent, muscular, flat or slightly withdrawn inside the column in preserved specimens. The pedal disc is the same colour as the column. The diameter of the pedal disc is ca. equal or slightly wider than the oral disc in preserved, contracted specimens. In live specimens the pedal disc is ca. equal or slightly smaller than the oral disc. The basilar musculature is well developed.

Mesenteries and internal anatomy: The mesenteries are arranged hexamerously in five cycles. The mesenteries of the first two cycles are perfect. The fifth cycle is incomplete and more developed distally, thus more mesenteries are present distally than proximally. There are two pairs of directives, each attached to a siphonoglyph. All of the mesenteries of the first three cycles (including the directives) are fertile and bear filaments. The mesenteries of the fourth and fifth cycles are weak, and without filaments or gametogenic tissue. The longitudinal muscles of the mesenteries are weak. The retractor muscles are diffuse, wide and span the first two-thirds of the distance between the body wall and the filament, are have relatively thick branches. The parietobasilar muscles are weakly differentiated from the mesentery, consisting of a few short processes with no pennon.

Cnidom: Robust and gracile spirocysts, basitrichs, holotrichs, microbasci p-mastigophores.

(Zelnio et al., 2009)


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