Cliona minuscula, Schönberg, Christine Hanna Lydia, Grass, Stefanie & Heiermann, Anke Tarja, 2006

Schönberg, Christine Hanna Lydia, Grass, Stefanie & Heiermann, Anke Tarja, 2006, Cliona minuscula, sp. nov. (Hadromerida: Clionaidae) and other bioeroding sponges that only contain tylostyles, Zootaxa 1312, pp. 1-24 : 4-6

Cliona minuscula , sp. nov.

Material examined

Two specimens of Cliona minuscula , sp. nov. from Little Pioneer Bay, Orpheus Island, Palm Island Group, Central Great Barrier Reef, Australia (18 40’S 146 30’E; Fig. 1 ):

Cliona minuscula , sp. nov. holotype: QM G322595, wet sample in alcohol, original sample number: 5.46, 27.10.2003: in dead, unattached shell of Tridacna crocea in 1.0 m depth on reef crest ( Fig. 2 A–B).

Cliona minuscula , sp. nov. paratype: QM G322596, slide preparation, entire specimen was used up for the preparation, original sample number: 2.80, 25.10.2003: in a dead brain coral in 2.2 m depth, from the reef flat.

Other species examined:

Cliona caesia new comb., various specimens from Little Pioneer Bay, Orpheus Island, Palm Island Group, Central Great Barrier Reef and Heron Island, Capricorn Bunker Group, Southern Great Barrier Reef Australia, wet samples in alcohol, Queensland Museum, spicule preparations in first author’s collection.

Cliona patera : MHNG38767 from the Museum in Geneva, dry specimen, section of a massive sponge. Sample site unknown.

Description of the holotype QM G322595

Live ectosome dark brown, endosome lighter brown to beige. Colour fading when frozen or in alcohol, with endosomal tissue becoming almost transparent. Papillae minute, mean papillar diameter 0.44 mm when contracted (minimum = 0.20 mm, maximum = 0.70 mm, SD = 0.14 mm, N = 25). Form circular in outline, occasionally irregular. Contracted papilla margins flush with surface, but towards centre ‘sunken’ into substrate, latter forming small circular pits around papillae ( Fig. 2 C–D). Some of these pits in sample QM G322595 no longer filled with sponge tissue, but with mud and algae. Papillae evenly dispersed, mean distance from each other 0.40 mm (minimum = 0.16 mm, maximum = 0.80 mm, SD = 0.18 mm, N = 25), fusion rare. Except for small areas opposite shell umbo, tissue not traversing entire width of shell, but penetrating to a depth of 1–2 mm. Sponge tissue emerging on inner side of shell forming net­like pattern ( Fig. 2 B). External erosion traces on shell outer surface as papillar pits and shallow grooves that connect papillar pits in close vicinity to each other ( Fig. 2 D). Endolithic erosion chambers minute, appearing finely porous, with spherical to oval chambers ( Fig. 2 E–F). Under magnification some chambers more irregular in shape as result of merging ( Fig. 2 F). Mean chamber diameter 0.59 mm (minimum = 0.2 mm, maximum = 1.3 mm, SD = 0.29, N = 25), mean diameter of canals connecting chambers 0.20 mm (minimum = 0.08 mm, maximum = 0.33 mm, SD = 0.07, N = 10).

Endosomal tissue thinly coating chambers and forming fragile membranes. Tylostyles in papillae in loose palisade, spicule points protruding from tissue by about 1/3 of spicule length ( Fig. 2 G). Tissue with zooxanthellae (dinoflagellate symbionts) concentrated at the sponge surface ( Fig. 2 H). Endosomal tylostyles aligned in parallel, forming bundles. Bundles in confused orientation. Skeleton comprised of megascleres only, i.e. of tylostyles ( Fig. 3 ). Mean tylostyle dimensions comparatively small, with shaft length x shaft width x tyle width: 225.3 x 4.5 x 6.8 µm ( Tab. 1). Tylostyle width size­frequency distributions skewed to left, indicating very uniform final size. Most tyles oval, slightly elongated ( Fig. 3 A–B), but some round ( Fig. 3 C–D), rarely with secondary swellings. Shafts predominantly straight ( Fig. 3 A–B), neck regions usually subtle, few with sharp creases ( Fig. 3 C–D). Axial threads extending about 2/3 into tyles. No vesicles observed when using light microscopy, but occasionally striations in tyles (layering of silica).

Additional species in the holotype

Specimen QM G322595 contains three other species of bioeroding sponges: Cliona ensifera , Cliona cf. orientalis in ­form and an unidentified species of Aka . Latter two species were only tentatively or incompletely identified, as C. cf. orientalis lacked microscleres and Aka sp. is a small specimen with indistinct fistules. Aka sp. and C. minuscula , sp. nov. occur in two tiers, with C. minuscule , sp. nov. forming the upper layer near the shell surface, being traversed by Aka sp. papillar canals ( Fig. 2 E–F). The additional species in QM G322595 are distinct from C. minuscula , sp. nov. by their spicules ( Tab. 2, Fig. 4), papillar size ( Tab. 2, Fig. 2 A) and form of erosion chambers ( Tab. 2, Fig. 2 B, E–F).

Ecology and distribution

To date only two specimens of Cliona minuscula , sp. nov. have been found, and only from one sample site at Orpheus Island, Palm Island Group, Central Great Barrier Reef.

The sponges were sampled from very shallow depths between 1 and 2 m in unattached rubble (dead clam shell) and in part of the reef framework (dead massive coral). The specimens were from the reef flat, i.e. from the mixed zone ( Schönberg 2001), and from the reef crest.

Etymology

The species name ‘ minuscula ’ was chosen, as compared to other species of Cliona , the new species has minute papillae and erosion chambers and smaller than average tylostyles.

Figures

FIGURE 1. Sample location of Cliona minuscula, sp. nov. (arrow). HIRS—Heron Island Research Station, LPB—Little Pioneer Bay, PB—Pioneer Bay, QLD—Queensland.

FIGURE 3. Cliona minuscula, sp. nov. tylostyles of QM G 322595. A – B—Tylostyles mostly have straight shafts and oval to drop­shaped tyles that are slightly longer than wide. C – D—Occasionally, tylostyles have more spherical tyles with distinct neck areas.