Latrunculia occulta, Lehnert, Helmut, Stone, Robert & Heimler, Wolfgang, 2006

Lehnert, Helmut, Stone, Robert & Heimler, Wolfgang, 2006, New species of deep­sea demosponges (Porifera) from the Aleutian Islands (Alaska, USA), Zootaxa 1250, pp. 1-35 : 30-32

Latrunculia occulta sp. nov.

( Fig. 17 a–b)

Description

Thinly encrusting on Chondrocladia concrescens . Not detectable by the unaided eye.

Surface smooth, same whitish colour as Chondrocladia (in ethanol). No styles detected. This species was observed as a very thin encrustation with a thickness of only a unispicular layer of anisodiscorhabds on the Chondrocladia . All discorhabds are, as in the previous species, arranged parallel to each other and perpendicular to the surface. The discorhabds measure 42–54 µm and are almost smooth and rounded. The discs of the discorhabds do not consist, as in all other species, of a row of large spines but are two solid discs, their margins only slightly acanthose ( Fig. 17 a, b). The ends of the spicule are two differently sized spheres which are again slightly acanthose. The rather complicated terminology of the anisodiscorhabds (i.e. a succession of manubrium, median whorl, subsidiary whorl, apical whorl and apex) does not really apply to this species. One whorl is missing, either the manubrium and the median whorl are fused to the small sphere or the apical whorl and the apex are fused to build the large sphere.

Discussion

This is the only species of Latrunculia which is living epizoic on another sponge and the only species recorded which is lacking megascleres completely. Several spicule preparations taken from different areas of the Chondrocladia confirmed the complete lack of styles and the unusual shape of the discorhabds. If there were other spicule types present they always originated from the Chondrocladia . It furthermore differs from all known species in the smooth appearance of the discorhabds and a reduced number of whorls. The discorhabds have a small sphere as manubrium, slightly acanthose on top, which is followed by relatively long shaft. The median and subsidiary whorl are both solid discs; not notched as in other species. The apical whorl and the apex are not distinguishable and form a larger oval body. (A possible alternative interpretation of the spicule is given in the description). Like L. velera , L. occulta is known from deep water only.

Distribution

Known only from the type locality.

Etymology

The species name — occulta — is derived from lat. occultus — hidden, unnoticed, secret, referring to the almost invisible growth form of this species.

Figures

FIGURE 17. Latrunculia occulta sp. nov. Very smooth discorhabds with reduced number of whorls. Slight spination on ends and margins of whorls. Whorls are solid discs. b, Latrunculia occulta sp. nov. almost smooth anisodiscorhabds, finely acanthaceous at the spherical ends and the discs.