Cliona tumula, Friday & Poppell & Hill, 2013

Friday, Sarah, Poppell, Ericka & Hill, Malcolm, 2013, Cliona tumula sp. nov., a conspicuous, massive Symbiodinium-bearing clionaid from the lower Florida Keys (USA) (Demospongiae: Hadromerida: Clionaidae), Zootaxa 3750 (4), pp. 375-382 : 376-381

Cliona tumula sp. nov.

(Table 1, Figs. 1–5 )

Material examined. Holotype ( USNM 1155078 ), Florida Keys , USA (24°33.180’ N; 81°22.845’ W, adjacent to Looe Key reef), 15 m depth, coll. M. Hill, 27 June, 2008 ( Fig. 1 ) . Paratypes – USNM 1226125 , cross ref. ICI, Florida Keys , USA (24°33.180’ N; 81°22.845’ W), 10 m depth, coll. M. Hill, 27 June 2008 . USNM 1226126 , cross ref. IA2, Florida Keys , USA (24°33.174’ N; 81°22.832’ W), 15 m depth, coll. M. Hill, July 2009 .

Description. The holotype consists of a large, pincushion-shaped mounding specimen typical of those encountered in the field. Cliona tumula sp. nov. does not appear to conform to standard life stage designations (i.e. alpha, beta, gamma) for the Cliona because these large bodied sponges have clearly not outgrown their substrata as might be expected in the gamma stage of development. Evidence for this conclusion comes from the type of calcareous debris found in the choanosome that must come from the surrounding environment (e.g., molluscan shells, urchin spines, calcareous algae), and is clearly not remnant scleractinian coral skeleton (see below). The C. tumula sp. nov. holotype has a flattened top with a central cluster of approximately 50 oscula. We observed 12 individual sponges in the field with oscular clusters ranging from 2 to 159 individual oscula. These oscular diameters ranged from 29 to 52 mm ( Fig. 1A ), but disturbance to the sponge caused oscula to contract with diameters decreasing to 14–34 mm ( Fig. 1B ). When fully open, the osculum has a thin, pale yellow rim. The colour of the holotype in life was yellowish brown to dark yellowish brown due to the presence of zooxanthellae, which are mostly concentrated in the ectosome (colour characteristics determined using the Munsell ® Soil Colour Chart). Due to chlorophyll loss in 70% ethanol, the holotype is very pale brown. The texture of the choanosome is grainy due to calcareous fragments dispersed throughout. The consistency is hard and incompressible, and the surface is microhispid due to clusters of spicular projections distributed uniformly.

Skeleton. The ectosomal skeleton consists of clusters of megascleres oriented perpendicular to the surface, which forms an irregular palisade and a loose crust of superficial spirasters ( Fig. 2 ). The choanosomal skeleton is a complex mix of sponge tissue, mega- and microscleres, canals, and calcareous fragments haphazardly distributed through the tissue ( Fig. 2 ). Calcium carbonate fragments of variable size (from greater than 5 mm to less than 300 µm) are found running longitudinally in the choanosome ( Fig. 3 ). The composition of the calcium carbonate fragments matches the sedimentary constituents found in the surrounding sands. That is, we found molluscan shells, urchin spines, calcareous algae, various calcareous protozoa, among other constituents within the choanosome of C. tumula sp. nov. ( Fig. 3 ). Thus this material is not remnant skeleton from a scleractinian coral.

Spicules. C. tumula sp. nov. megascleres are tylostyles. Megascleres exhibit noticeable plasticity in head shape and placement of the head along the shaft. Numerically dominant tylostyles have an ellipsoid head at the end of the shaft ( Fig. 1C–G ). Average tylostyle length, head width, and shaft width are 379.8, 11.7, and 8.9 µm, respectively (Table 1). Two distinct types of microscleres are present. Normal spirasters are abundant ( Fig. 1H–K ). Uncommon diplaster-like spirasters, 17.3 to 25.4 µm in length, were also present. These had sparse spines along the shaft and spiked caps approximately three times the diameter of the shaft ( Fig. 4 ).

Ecology. Cliona tumula sp. nov. is common on shallow reefs adjacent to Looe Key reef between 10 and 15 m. We encountered some specimens growing in sand flats surrounding the southern side of the reef at depths greater than 15 m. Numerically dominant sponges from this habitat include Callyspongia vaginalis , Xestospongia muta , Spheciospongia vesparium , Cliona varians , C. delitrix , Amphimedon compressa , Iotrochota birotulata , Niphates erecta , and N. digitalis . The sponge has not been found in the sand flats on the northern side of the reef tract.

One notable behavior of C. tumula sp. nov., as has been described in other clionaids, is that it has the capacity to rapidly constrict its oscular openings. We observed this sponge with tightly closed oscula on several occasions, but especially during periods with poor visibility (and high levels of material suspended in the water column). At these times, the ostial surfaces of C. tumula sp. nov. were covered in sediment.

Geographic distribution. Specimens were only found on patch reefs to the east of Looe Key , Florida (24°39.601’ N, 81°22.775’ W). To date this sponge has not been located outside of this region .

Etymology. The name, tumula , is derived from the Latin word tumulus, for mound or small hill (i.e., pincushion-like), which is reflective of the body form of the new species.

Remarks. Cliona tumula sp. nov. is characterized by its large body, organized oscula, and clionaid-type spicules. Given that the osculum and external surface texture share some superficial phenotypic similarities to sympatric encrusting C. varians (Duchassaing & Michelotti, 1864) , we initially thought C. tumula sp. nov. might represent a morphological variant of C. varians . Thus, all C. tumula sp. nov. spicules were compared to C. varians spicules to determine if the new sponge harbored anthosigmas, which are diagnostic of C. varians ( Fig. 5 ). Both massive and encrusting morphotypes of Cliona varians had a high prevalence of anthosigmas whose average lengths, respectively, were 13.9 µm and 12.5 µm. Diplasters were only encountered in C. varians , where their average lengths were 32.8 µm (massive) and 36.8 µm (encrusting). No anthosigmas or true diplasters were found in C. tumula sp. nov.

One of the most taxonomically relevant traits that will help distinguish C. tumula sp. nov. from the other clionaids (other than overall morphology), was the presence of rare diplaster-like spirasters ( Fig. 4 ). The ratios of tylostyle length to head width and shaft width are within the range seen in the other Caribbean clionaids, but C. tumula sp. nov. tylostyles have head widths much thinner than those of C. aprica and C. caribbea , albeit similar to head widths reported for C. tenuis and C. varians (Table 1). Cervicornia cuspidifera (Lamarck, 1815) and Pione lampa (de Laubenfels, 1950) had smaller heads than C. tumula sp. nov. (Table 1). The ubiquitous presence of calcareous fragments that were acquired from the surrounding sediments and dispersed throughout the choanosome was intriguing and represents a diagnostic trait ( Figs. 2– 3 ). It appears that C. tumula sp. nov. transports these fragments throughout its body organizing them in tracts that run perpendicular to the ectosome ( Fig. 2 and inset). This sponge lacks pore sieves, thus does not have characteristics of Spheciospongia , even though the overall growth form is reminiscent of the adult S. vesparium (Lamarck, 1815) body plan.

Cliona tumula sp. nov. may have a very restricted geographic distribution. We have not observed this sponge in surveys of patch reefs in similar habitats in the upper and middle Florida Keys. Despite his thorough inventory of sponges in the Dry Tortugas, which lie to the west of Looe Key, de Laubenfels (1936) did not document this species. Additional effort is required to rule out the possibility that C. tumula sp. nov. does not occur elsewhere in the Florida Keys or Caribbean.

Figures

FIGURE 1. A. In situ photograph of Cliona tumula sp. nov. B. Preserved holotype (scale = 10 cm); C. Micrograph of representative subtylostyle from C. tumula sp. nov. (scale = 100 µm); D-G. Micrographs of variability in C. tumula sp. nov. tylostyle head shapes (scale = 10 µm); H–K. Micrographs of C. tumula sp. nov. spirasters (scale = 5 µm).

FIGURE 2. Camera lucida drawing of thin section of Cliona tumula sp. nov. showing embedded calcareous fragments (in bold) in the choanosome (scale = 1 mm). Inset: choanosome of ethanol preserved specimen highlighting tracts of sediment that the sponge incorporates in its mesohyl. The tracts run perpendicular to the ectosome.

FIGURE 3. Micrographs of calcium carbonate fragments extracted from Cliona tumula sp. nov. choanosome tissue. A. Mollusc shell with clear evidence of sponge bioerosion (scale = 200 µm); B. Evidence of cellular etching and calcareous chip removal by C. tumula sp. nov. (scale = 100 µm); C–D. Unidentified calcareous fragments found in the choanosome that are clearly derived from calcareous tests of organisms on the reef. That is, the material is not remnant skeleton from a scleractinian coral that this species out-grew as can be found with some gamma-stage clionaids (scale = 200 µm).

FIGURE 4. Diplaster-like spiraster from C. tumula sp. nov. (scale = 5 µm).

FIGURE 5. Microscleres from Cliona orientalis, Cervicornia cuspidifera, and C. varians. A. C. orientalis spiraster; B. Cervicornia cuspidifera spiraster; C. Cliona varians (encrusting) spiraster; D. Cliona varians (encrusting) anthosigma; E. Cliona varians (encrusting) diplaster; F. Cliona varians (massive) spiraster; G. Cliona varians (massive) anthosigma; H. Cliona varians (massive) diplaster. Scales: A, C–D, F, 5 µm; B, G, 2 µm; E, H, 10 µm.