Neophrissospongia nana Manconi & Serusi, 2008

Manconi, Renata & Serusi, Annalisa, 2008, Rare sponges from marine caves: discovery of Neophrissospongia nana nov. sp. (Demospongiae, Corallistidae) from Sardinia with an annotated checklist of Mediterranean lithistids, ZooKeys 4 (4), pp. 71-87 : 73-76

Neophrissospongia nana Manconi & Serusi , nov. sp.

urn:lsid:zoobank.org:act:63EE3CCC-0D80-4A9D-85FD-23B41D21F4EF

( Figs 1-4 ; Table 1 ; Appendix 1)

Type locality: Grotta delle Terrazze n. 2740Catasto Speleologico Regionale(40°34’16”N 08°13’43”E), Punta Giglio Promontory, Alghero, NW Sardinia, 10.iv.2004, R. Barbieri coll. by SCUBA diving.

Type material. Holotype MSNG 54599 , fragment of a living specimen. Schizotypes (TER 2) on SEM stubs and slides are deposited at present in the collection of R. Manconi.

Material studied: Corallistes nolitangere Schmidt, 1870, p. 23 , MNHN DT 781, Fayal, Campagne Prince Albert de Monaco Azores I, leg. E. Topsent, 1 slide; MOM 2144-0-04-0191, large specimen, collection E. Topsent, presumably Azores; AZR 71, collection G. Pulitzer-Finali, 4 slides, unknown locality of Azores.

Description. Known from a single specimen. Growth form as a large thick encrusting plate (10-12 x 5-7 cm) with a wide base adhering to the substrate and rounded margins. The sampled portion (holotype, 5 x 3.5 cm in width, ca. 1.2 cm in thickness) is one third of the entire living specimen. Colour white ice both in vivo

and in spirit, except for a brown degenerated portion at the margin. Consistency stony, harder toward the basal portion. Surface even without asperities, aconulose. Ectosome with irregular sub-dermal canals. Inhalant apertures (0.2-1.2 mm in diameter) grouped in slight concavities along the sponge margins. Exhalant areas scattered on the top surface with grouped oscules (0.5- 1 mm in diameter) each with a well-developed vertical atrial canal. Ectosomal skeleton armed by a layer of radially arranged dichotriaenes megascleres of two types. Dichotriaenes with cladomes (145- 270 µm in diameter) bearing few tubercles (10-20 µm in height) rarely subdivided at the upper surface of protoclades (20-50 x 10-20 µm, usually 20-30 µm in length) and deuteroclades (50-100 x 10-20 µm, usually 50-70 µm in length). Deuteroclades sometime with branched tips. Rare dichotriaenes with entirely smooth cladomes (93-172 µm in diameter) and scarcely developed clades also present with no differential localization. Rhabdomes with blunt to acute tips (290-540 µm in length) usually smooth, sometimes bearing a few large acute spines or tubercles (up to 30 µm in length) along the axis. Extremely rare triaenes with a few tubercles on the clades also present. Other ectosomal spicules of two types, namely asterose and monaxial. Microscleres as streptaster/amphiaster with short spiny rays (5-15 µm in length) in a variable number (3-7) with blunt tips. Notably thin styles/sub-tylostyles (59-86 µm, <3 µm in thickness) scattered and tangentially embedded in subectosomal membranes in both the inhalant and exhalant areas.

Architecture of the choanosomal skeleton as a loose network of slender dicranoclone desmas, strongly articulated along the canals of the aquiferous system. Desmas (280-360 µm) with rounded tubercles (5-35 µm in height, usually 10-15 µm) bearing smooth heads. Slender small young desmas with a smooth surface also present.

Diagnosis. N. nana nov. sp. is characterised by growth form as a large thick plate with inhalant apertures in concavities along the sponge margins and few conspicuous exhalant apertures grouped at the top. The spicular complement is characterised by a smaller size of spicules when compared to the other species of the genus. Ectosomal skeleton with tubercled to smooth dichotriaenes (rarely triaenes) radially arranged with no differential topographic distribution. Sub-ectosomal membranes bear styles/subtylostyles tangentially embedded and spiny streptaster/amphiaster microscleres.

Etymology. The specific epithet refers to the small size of the skeletal spicules.

Distribution. Known until now exclusively from the western Sardinian cave Grotta delle Terrazze (type locality).

Habitat. Shallow water (6 m) on the rocky wall in the innermost part of a dark horizontal tunnel (80 m in length) of a submerged cave (160 m along an N-S axis, main entrance at 17 m of depth, 40 m in length, 7 m in width). Another tunnel at the left of the entrance harbours a small population of Petrobiona massiliana Vacelet & Lévi (Manconi et al. in press). The absence of sand deposits and the presence of abundant large boulders suggest the cave is subjected to a notably high water movement (southwestern winds). In April water temperature was 14 ºC. Few serpulids and foraminiferans were found associated with the sponge on an almost bared rocky surface.

Figures

Fig. 1. Habitus of the cave-dwelling Mediterranean Neophrissospongia nana nov. sp. from north-western Sardinia. A. In situ plate-like growth form in the type locality Grotta delle Terrazze (photo by R. Barbieri), B. Holotype MSNG 54599 (top view) (photo by G. Delitala).

Fig. 2. Neophrissospongia nana nov. sp., holotype MSNG 54599, photomicrographs of the skeletal architecture and spicular complement. A-C. Subectosomal skeletal network of dicranoclone desmas. D. Dichotriaene (top) and simple triaene (bottom, arrows) radially arranged in the ectosome with tubercled cladomes. E. Articulation among desmas with scattered styles/sub-tylostyles in the sub-ectosome. F.Detail showing the arrangement of silica in dicranoclone desmas (cross section) and styles/sub-tylostyles (arrows). G-I. Streptaster/amphiaster microscleres with spines/tubercles.

Fig. 3. Neophrissospongia nana nov. sp., holotype MSNG 54599, spicular complement. A. Dichotriaene. B. Cladome of a tubercled dichotriaene (top view). C. Streptaster/amphiaster microscleres with tubercles. D. Cladome of a smooth dichotriaene (top view). E. Dicranoclone desma. F. Styles/sub-tylostyles.

Fig. 4. Geographic range of the genus Neophrissospongia with occurrences of the known species N. nolitangere in the Atlantic and N. microstylifer in the Pacific Ocean. The type locality of N. nana nov. sp. from Sardinia is indicated by a star.