Anthosactis pearseae Daly & Gusmao, 2007
Base and column: The column is stout, ca. equal diameter throughout in preserved specimens, or slightly flaring proximally, weakly ribbed longitudinally in highly contracted specimens. In live specimens the column flares from the base, being wider distally than proximally. Most specimens are a uniform opalescent white, although a few are pale pink. In all specimens the mesenteries are faintly visible through the column as pinkish lines. There is no fosse, although the distal lip of the column may extend beyond the base of the tentacles in contracted specimens. The distal column of some specimens is sparsely scattered with small, poorly demarcated suckers. No specimens had any material adhering to these suckers. The proximal column is smooth. The limbus may extend past the pedal disc, causing the pedal disc to look shrunken or retracted. The pedal disc is adherent, muscular, and is the same colour as the column. The pedal disc is ca. equal or slightly larger in diameter than oral disc in preserved specimens. The oral disc is larger than pedal disc in well-expanded live specimens. The ectoderm of the column contains small clusters of goblet-shaped basophilic (blue-staining) material without discernible nuclei or any other cellular structures surrounded by deeply staining epitheliomuscular cells. The column musculature is strong, ectodermal and mesogloeal and is concentrated into a mesogloeal marginal sphincter distally.
Oral disc and tentacles: The tentacles are partially covered by a distal column in contraction, and the oral disc is not visible. The tentacles and oral disc are same colour as the column. The mouth is central, with two prominent siphonoglyphs. The lips and siphonoglyphs are slightly paler than the oral disc in pink specimens, but are more opaque than the disc in white specimens. The tentacles are bluntly pointed, and longitudinally fluted in preservation, with a length ca. equal to diameter of oral disc. There are about 100 tentacles in four crowded cycles on the outer half of oral disc. Those of the outermost cycle are the longest. In live specimens, tentacle length is ca. equal to column height. The tentacle musculature is ectodermal. As the tentacles are partially retracted inside the column, the relative thickness of the oral and aboral ectoderm at the base could not be assessed.
Mesenteries and internal anatomy: The mesenteries are arranged hexamerously in three to four cycles, with only those of first cycle being perfect. There are two pairs of directives, each attached to siphonoglyph. All mesenteries of the first and second cycles (including directives) bear filaments and gonads. The mesenteries of the fourth cycle are weak, lacking filaments and reproductive tissue. The longitudinal muscles of the mesenteries are weak. The parietal muscle is not distinct from the mesenterial lamella, consisting of few short processes with no pennon. The retractor muscle is circumscribed but not very broad, and comprises of a few, unramified branches towards the coelenteron and a few larger, more ramified branches closer to the body wall
Cnidom: Spirocysts, basitrichs, holotrichs, microbasic p-mastigophores are all present
(Daly & Gusmao, 2007)
Ecology and Distribution
Monterey Canyon, (36°36.8031'N 122°26.1203'W), depth 2,893 m on a whale skeleton (Daly & Gusmao, 2007).
All specimens collected in late November were sexually mature, with either female or male gametes in any single specimen, whilst some were brooding larvae. The mode of larval production is unclear: some specimens with male gametes bear young (Daly & Gusmao, 2007).