Siphonidium ramosum (Schmidt, 1870)

Gómez, Patricia & Calderón-Gutiérrez, Fernando, 2020, Anchialine cave-dwelling sponge fauna (Porifera) from La Quebrada, Mexico with the description of the first Mexican stygobiont sponges, Zootaxa 4803 (1), pp. 125-151 : 136-138

Siphonidium ramosum (Schmidt, 1870)

Fig. 7

Synonymy and other records. Leiodermatium ramosum Schmidt, 1870:21 . Siphonidium ramosum ; Schmidt 1879:28; Pisera & Lévi 2002:342. Leiodermatium sp.; Calderón-Gutiérrez et al. 2018:14, S1 Table, S3 Table.

Material examined. CNPGG‒1497, 1498, 1499, 1500, Cenote S-1, La Quebrada anchialine cave, Cozumel, Quintana Roo, Mexico (20°26’16.75’’N, 86°59’47.44’’W). Depth 4.5 m, January 12, 2015; coll. F. Calderón-Gutiérrez and German Yañez. CNPGG‒1623. Same location. Depth 5.2 m, October 23, 2015; coll. F. Calderón-Gutiérrez and German Yañez. CNPGG‒1624, 1625, 1626, 1627, 1628, 1629, Same location. Depth 5.6 m, October 25, 2015; coll. F. Calderón-Gutiérrez and German Yañez.

Description. This is usually a small sized sponge that is kidney-shaped or irregularly massive in shape, overall size range 4.5‒7 mm long, 2‒7 mm wide and 3‒12 mm high. All of them have two to four cylindrical or siphon-like fistules, which measure less than 1 mm to 2 mm in diameter. The fistules are flattened and open at the top, provided with septate oscules inside ( Fig. 7a ). Oscules measure less than 1.0 mm to up to 2 mm diameter. Color orange-brown when alive and when in alcohol. Consistency hard, not compressible at all and crumbles easily when cut.

Skeleton. ( Fig. 7b ) Choanosomal skeleton consists of rhizoclone desmas tightly bounded to each other forming a strong structure and difficult to cut off; juvenile desmas are smooth, with just a few to several branches. A layer of interlocking tiny desmas at the surface covers the subjacent rhizoclone desmas from the choanosomal skeleton. Choanosomal exotyles, (tylostyle-like) are crossing the choanosomal skeleton, embedded deep in the choanosome, not crossing outside the surface.

Spicules. ( Fig. 6 c-e) Uneven tetraclone desmas with smooth clones sometimes warty that bifurcate several times, they measure 118‒220 µm towards the longest size; smaller and smooth desmas measure 13‒122 µm. Exo- tyles are smooth and straight, pointed ends wispy or blunt, with rounded and rugose or spined heads, 156‒255 × 2.6‒3.9 µm, head about 5.5‒6.7 µm.

Geographic distribution. Open reef: Florida ( USA), Barbados and Brazil. Anchialine cave: Cozumel ( Mexico).

Ecology. This is the first record of S. ramosum inhabiting cave environments. In the anchialine cave was regularly found adhered to the floor and under rocks, at the shallowest depth known for the species (4.5-5.6 m deep), previously recorded at 104 to 439 m. No individuals were observed inside the transects of the quantitative survey ( Calderón-Gutiérrez et al. 2018 as Leiodermatium sp.) most likely due to their small size and its similar color and shape to the surrounding rocks.

Remarks. Our Siphonidium ramosum is quite similar to the re-described holotype by Pisera & Lévi 2002 from Florida. Although their specimens are larger in size (2‒5.5 cm), compared with the present material, spicule measurements on both are quite similar (desmas 180‒220 µm, exotyles 160‒220 × 2‒3 µm). Other measurements in Mothes & Silva (1999, Table I) are probably out of the range with exotyles up to 532 × 9.5 µm from Brazil, and 304‒627 × 4.6 µm from Barbados. Consequently, it is noteworthy that our samples, collected from a different envi- ronment and depth, have quite the same desmas and exotyle sizes as those from deep water (229 m) from Florida. It is necessary to confirm the conspecificity of S. ramosum sensu Topsent (1904) from the Mediterranean, since exotyles are too large in size (800‒1000 × 4‒6 µm), and some spicules are registered as tylote type (with two swol- len heads) in Pl VIII fig. 5; in addition to the disjunctive geographic range.

Figures

FIGURE 6. Svenzea germanyanezi sp. nov. a) Holotype CNPGG‒2342 (ethanol); b) choanosomal skeleton (cross section, LM); c) granulous cells (LM); d) ectosomal skeleton, note the dermis and punctate surface at the upper flank (tangential section, LM); e) strongyles (LM); f) common spicule oxea II (LM); g) thinner oxea I (LM).

FIGURE 7. Siphonidium ramosum (Schmidt, 1870). a) CNPGG‒1624 habitus, CNPGG‒1625 (ethanol), notice the two siphonlike apertures; b) skeletal detail assembled by desmas (SEM); c) tetraclone desmas with smooth clones (SEM); d) tetraclone desmas with warty clones (LM); e) spined tylos of tylostyles (SEM).