Styloptilon ancoratum

Cabioch, 1968

Species Overview

Styloptilon ancoratum Cabioch, 1968 is a thinly encrusting deep-water species, identifiable only on its microscopic skeletal features. It has been recorded only once from Roscoff, NW France.

Taxonomic Description

Colour: Yellowish white in alcohol.
Shape, size, surface and consistency: Thinly encrusting, about 1 mm in thickness, agglutinating shell debris. The surface is finely hispid.
Spicules: Megascleres are acanthostyles and tornotes. The tornotes are smooth and have pointed, but unequal ends, one being slightly swollen; they may be somewhat polytylote or have an irregular outline: 140-200 x 2.5-5 µm. The acanthostyles are entirely spined and perhaps dividable in two size categories: 100-135 x 5-8 µm and 190-280 x 5-10 µm, but they do not constitute two functional categories (main and echinating).
Microscleres : Spatulate anchorate isochelae in two size categories: 35-48 µm and 11-15 µm; sigmas in a single variable size category: 32-50 µm.
Skeleton: The dermal membrane is charged with microscleres and carried by bouquets of tornotes, which also form short tangential bundles. The bouquets of tornotes are in turn erected on the peripheral ends of the choanosomal spicule tracts, which consist of acanthostyles. The skeletal columns are thick and form a plumoreticulate skeleton, in which the longitudinal elements dominate.
Ecology: On pebbles at 85 m.
Distribution: Known only from Roscoff, NW France.
Etymology: The name refers to the anchorate chelae, which are unusual in combination with a plumose skeletal structure.
Type specimen information: The type is in the collections of the Station Biologique de Roscoff.

Remarks

This species remains ill-known. Its characters are inbetween those of Phorbas (plumose columns, pointed tornotes, two sizes of acanthostyles) and Myxilla (anchorate chelae). For that reason it is assigned to its own genus in the Myxillidae (see also Desqueyroux-Faúndez and Van Soest, 1996).
Source: Cabioch, 1968.