Acanthodendrilla levii, Uriz & Maldonado, 2000

Uriz, Maria J. & Maldonado, Manuel, 2000, The genus Acanthodendrilla in the Mediterranean Sea with description of a new species, Zoosystema 22 (2), pp. 401-410 : 403-405

Acanthodendrilla levii n. sp.

HOLOTYPE. — Centre for Advanced Studies of Blanes, Spain, No. CEAB. POR. BIO.138

PARATYPES. — Centre for Advanced Studies of Blanes, Spain, No. CEAB.POR.BIO.137a and 137b).

ETYMOLOGY. — The species is dedicated to C. Lévi, who established the guidelines for the modern sponge systematics.

TYPE LOCALITY. — Blanes ( Spain, western Mediterranean) sublittoral, at depths of 100- 130 m.

DESCRIPTION

External features

Foliaceous to massive, erect sponge ( Fig. 1 ). The holotype is a 9.5 cm high, 8 cm wide erect thin (0.2-0.3 cm in thickness) fan-like sheet, with some lateral projections perpendicular to the general sponge plane ( Fig. 1C ). One of the paratypes (CEAB.POR.BIO.137a) is a sheet 0.5 cm in thickness, which arises from the substrate by means of four stalks, 0.3-0.5 cm in diameter, and soon divides into several flat branches which often anastomose to produce an irregularly massive sponge ( Fig. 1A, B ). Paratype 2 exclusively consists of the skeleton, which shows a primarily dendritic, secondarily reticulate pattern ( Fig. 1D ).

The sponge surface is clean and smooth to the touch, conulose, with conules 1-3 mm high, 2-5 mm apart. The primary fibres protrude up to 2 mm from the conules but this might be the result of contraction after preservation in alcohol. Consistency soft in living specimens, somewhat coriaceous but easy to break in alcohol. The ectosome is firmly attached to the choanosome but can be separated with forceps in some places. Oscules, maximum width of 2 mm, are spread on the sponge top, either isolated or grouped in clusters of 3-4. Ostia are inconspicuous in preserved specimens. Living specimens were pinkish, cream after preservation in alcohol.

Skeleton and characteristics of the soft tissue Primary fibres strongly fasciculate and densely arranged at the sponge base (stalked zones) ( Fig. 1D ). They run parallel along the stalk and then spread divergently in a flabelliform pattern, branching and interlocking repeatedly ( Figs 2A ; 3A ). They also appear secondarily reticulate by means of secondary fibres, which often form perforate spongin plates ( Figs 2B ; 3C ). The reticulate pattern is much more evident at the sponge periphery, where a network is visible on the sponge surface.

Primary and secondary fibres have a strongly laminated bark ( Figs 2D ; 3 B-D). Spongin layers appear to be breakable and of different thickness ( Fig. 3B, C ). A distinct pith is present in both the primary and secondary fibres ( Fig. 2F ). Primary fibres are heavily cored with foreign material ( Figs 2 A-E; 4A, B). Secondary fibres also include some debris. Sponge spicules are particularly abundant among the debris incorporated into the fibres ( Fig. 4 A-C), and are present not only within the pith but between contiguous spongin layers of the bark ( Figs 2C, D ; 4B, D ). Some spicules completely traverse the fibre bark and the fibre surface thus appears perforated ( Fig. 4D ). Some foreign debris are present within the choanosome, outside the fibres.

Primary and secondary fibres are 230-400 µm and 20-150 µm thick, respectively. Fenestrate spongin plates are 400-1500 µ m in diameter. The fascicled skeleton at the sponge stalks ranges between 3 mm and 10 mm in diameter.

Fibres are more or less dark brown but are never purple, red or black as described for other dictyodendrillid genera (Bergquist 1995).

The choanosome is well-developed with large aquiferous canals and reduced mesohyl. The choanocyte chambers are large (60-150 µ m in diameter) and oval in a section with relatively large choanocytes ( Fig. 5A ). The ectosome is 100-200 µ m thick and has two differentiated layers ( Fig. 5B ): the external layer, 50-60 µ m thick, is rich in collagen; the inner layer, 100-130 µ m thick, has abundant cells. Large subectosomal canals separate the ectosome from the choanosome.

Habitat and reproduction

The species dwells on detritic bottoms at a depth of 100- 130 m. The specimen CEAB.POR.BIO. 137a (paratype) was reproducing in June. Embryos, 250 µ m in diameter, were located in groups of two to three at the distal part of branches.

Figures

FIG. 1. — A, B, paratype 1; C, holotype; D, paratype 2, consisting of the sponge skeleton. Scale bars: A, B, 2.5 cm; C, D, 2 cm.

FIG. 2. — Light microscope views of different aspects of the sponge skeleton; A, distal part of the skeleton with terminal primary fibres heavily cored with foreign debris, secondary fibres slightly cored; B, perforate plate formed by secondary fibres; C, detail of a primary fibre (distal zone) showing large amounts of foreign materials; D, detail of a primary fibre with the stratified bark (sb) and the pith masked by some foreign material; E, primary and secondary fibres showing reticulation; F, histological section showing the insertion of a secondary fibre (without inclusions) in a primary fibre (with inclusions): p, pith; sb, stratified bark; d, foreign debris. Scale bars: A, E, 500 µm; B, C, 200 µm; D, F, 100 µm.

FIG. 3. — SEM views of spongin fibres; A, view of several fibres; B, external aspect of a ramified secondary fibre; C, perforate plate; D, broken fibre showing the different layers of the stratified bark. Scale bars: A, 500 µm; B, D, 50 µm; C, 100 µm.

FIG. 4. — SEM views of fibre details; A, section of a secondary fibre showing abundant inclusions; B, broken fibre with sponge spicules among the foreign inclusions; C, tylostyle head protruding the fibre surface; D, orifices and other tracks in the fibre surface produced by detached materials previously incorporated to the fibre. Scale bars: A, 25 µm; B, 50 µm; C, 60 µm; D, 6 µm.

FIG. 5. — Light microscope images of sponge sections; A, choanosome: ch, choanocyte chamber; B, ectosome:el, external layer; il, internal layer; c, subectosomal canal. Scale bars: A, 15 µm; B, 40 µm.