(Ridley, 1881)
Species Overview
Axinella egregia (Ridley, 1881) is a greyish yellow, stalked, branched form which a tendency to become fan-shaped. Surface hirsute and conulose. It can only be distinguished with certainty from the similar Axinella flustra by the absence of trichodragmas. It is a southern species, originally described from southern South America.
Taxonomic Description
Colour: Greyish yellow in life; cream in alcohol.
Shape, size, surface and consistency: Erect stipitate specimens, 5.5-7 cm high, with
short stalks ending in laminae 0.5-0.9 cm thick with irregular contours (Axinella egregia 2). Some short, rounded, newly formed branches are in evidence in one specimen. Surface hirsutely conulose owing to skeletal projections. Oscula and ostia indistinguishable. Ectosome of a pseudoepitelial type almost totally damaged in preserved specimens. Consistency firm in the stalk, somewhat more flexible in the remaining sponge.
Spicules: (Axinella egregia spics) Styles I long and relatively thin, slightly curved, tapering to a sharp point, some of them swollen subterminally: 1250-1400 x 10-11 µm. They echinate the peripheral tracts protruding from the sponge surface. Styles II, stout, slightly and widely curved: 370-580 x 11-18 µm. Styles III, stout, sharply bent at approximately one-fourth of its length (in the form of a rhabdostyle), with sharp points or gradually ending in a step-wise fashion: 200-320 x 11-15 µm. Oxeas, sharply bent in the middle, with sharp points or gradually ending in a step-wise fashion: 170-340 x 10-13 µm.
Skeleton: Strong axial condensation of stout styles linked by spongin, perpendicularly echinated by plumose fibers of stout and long styles interconnected by single oxeas in such a way that the extra-axial skeleton has a plumoreticulate structure.
Ecology: On pebble bottom, from 13 to 135 m.
Distribution: Iberian Peninsula (Asturias, Santander, Galicia), France (Roscoff, Iles de Glénan); Mediterranean. South Atlantic: Strait of Magellan, Chile.
Etymology: Egregius (Latin) = distinct, distinguished, referring to the shape which was considered unusual at the time of its description.
Type specimen information: The type is in the Natural History Museum, London.
Remarks
This Axinella shows unusual features compared to the more common species of the genus, such as the thickness of the foliaceous branches and the hirsute-conulose surface. Fan-shaped specimens of this species differ from Axinella flustra with certainty only by the absence of trichodragmas. As indicated by Ridley (1881), it seems to be close to A . cinnamomea Schmidt from the Adriatic and Algerian coast, although there are clear differences such as the presence of two different categories of slightly curved styles and the rhabdostyloid form of the sharply bent styles, both typical characteristics of A . egregia .
The original specimen of this species was recorded from southern South America (Straits of Magellan); the conspecificity of specimens from that area and from Western Europe needs further corroboration.
Source: Uriz and Maldonado, 1993.