Raspailia agnata Topsent, 1896


Family : Raspailiidae

Form: Erect stalked specimens, 6.5-28 cm high, branching mostly in a single plane. The stalk, 0.6-2.5 cm wide, splits up at 1-6 cm of the base into two to several branches that successively bifurcate to many branches (10-39) in the biggest specimens. The branches, 0.5-2 cm in diameter, are compressed and frequently concrescent in their basal part but grow freely in a cylindrical-acuminate shape in the apical zone. They show lateral serial small expansions, 2-3 mm wide, similar to those found in some species of Axinella such as A . cannabina or A . dissimilis. These expansions can produce additional narrower branches by growth.

Colour: Orange-yellow in life, ochre in alcohol.

Consistency: Firm and hard in the basal parts, flexible in the apical zones.

Surface: Surface quite hispid, especially in the inner parts of branches, velvety to the touch.

Apertures: Functional orifices, 100-200 Ám in diameter, widespread through the whole sponge without any clear differentiation between oscules and ostia. Superficial depressions perpendicular to the main axis of branches separating the lateral expansions in fixed specimens seem to correspond to subectosomal exhalant canals.

Internal characters

Skeleton: An axially condensed zone, notably wider in the stalk and basal part of the branches, and a looser peripheral area are clearly discernible. The axis is comprised of ascending reticulate tracks of 4-7 styles. In the peripheral (extra-axial) area, plumose bundles of styles divergently rise from the central axis, ending in a brush of two to four long spicules. These spicule brushes protrude from the sponge surface and thus cause the external hispidation. Bundles of oxeote ectosomal spicules surround the hispidating styles near the sponge surface. The spongin is abundant around the main spicule tracks, and it cements the base of the styles in the extra-axial bundles. Its abundance decreases from the sponge base to the apex of branches.

Spicules: Styles of two categories, difficult to separate on the basis of their dimensions or form since intermediate spicules are frequently found. The two categories are distinguished mainly by their axial or extra-axial location within the skeleton. Both are curved in the basal zone or even flexuous. Those forming part of the central axis, styles I: 225-700 x 10-30 Ám are in general more curved and stronger than those responsible for the sponge hispidation, styles II: 400-1200 x 10-30 Ám. Some of the longer styles can occasionally have both ends rounded in the shape of a strongyle. The supplementary category of oxeas described by Descatoire (1969) is not present in any of the eight Mediterranean specimens, which perfectly match the spicule types described in the holotype. Ectosomal thin oxeote spicules: 200-410 x 2-3 Ám, slightly curved, occasionally flexuous, with short points (called tornotes by previous authors: Topsent, 1896; Descatoire, 1969).

Habitat: On horizontal rocky substrates and on pebble bottoms, 30-108 m.

Distribution: Channel area, west coast of France and Spain; Mediterranean.

Distribution Map from NBN: Grid map (fast) : Interactive map (slower, requires login to view records) : National Biodiversity Network mapping facility, data for UK.

Identity: This species was assigned to the genus Axinella by Topsent (1896), who nevertheless suggested that its character was intermediate between Axinella and Raspailia. Descatoire (1969) argued that a new genus was needed for this species despite the fact that two genera (Raspailopsis Burton, 1959b and Syringella Schmidt sensu Ridley, 1884) had been previously used for sponges matching the genus Raspailia but lacking acanthostyles, as is the case in Topsent's species. According to Hooper (1991), Syringella was in use when Burton (1959) erected the genus Raspailopsis for similar sponges and consequently it has priority. Because the absence of acanthostyles does not seem reason enough to separate genera in this family, we agree with Hooper (1991) that Syringella should be considered a subgenus. The present species is related to other Raspailia lacking acanthostyles such as R . australiensis Ridley, R . clathrata Ridley, R . elegans Lendenfeld, R . nuda Hentschel, and R . stelliderma (Carter). Despite the fact that it has seldom been recorded, R . agnata seems to be frequent along the French Atlantic coasts at depths of 30-100 m (Borojevic et al., 1968). Curiously, it has never been recorded outside this region. The specimens found by Descatoire (1969) displayed additional oxeas, absent from the type. The specimens described from Ouessant by LÚvi and Vacelet (1958) do not seem to correspond to this species, since oxeas are present, the ectosomal oxeote spicules and the long styles are lacking.

Editors: Christine Morrow, Bernard Picton & Rob van Soest.

 Picton, B.E., Morrow, C.C. & van Soest, R.W.B., 2011. [In] Sponges of Britain and Ireland