Myrmekioderma granulatum ( Esper, 1829 )

Calcinai, Barbara, Belfiore, Giuseppe, Pica, Daniela, Torsani, Fabrizio, Palma, Marco & Cerrano, Carlo, 2020, Porifera from Ponta do Ouro (Mozambique), European Journal of Taxonomy 698, pp. 1-56 : 21-22

Myrmekioderma granulatum ( Esper, 1829)

Fig. 12

Alcyonium granulatum Esper, 1829: 71 , pl. 24.

Material examined

PONTA DO OURO • 1 fragment 3×2 × 1 cm; 26°49′50.408″ S, 32°53′45.97″ E; Doodle; 17.6 m deep; 20 Apr. 2017; Cerrano leg.; PO98 .

Description

Live sponge massive, bulbous, partially burrowing ( Fig. 12A ) and with the surface covered by large, circular, low, rounded plates, similar to flat tubercles. Color bright orange, while the tubercles are darkred, brownish colored ( Fig. 12A ); the sample preserved in alcohol is beige. The sponge is fleshy and compressible. The surface appears smooth, but is micro-hispid at microscope magnification.

SKELETON. Ectosome composed of brushes of densely packed spicules ( Fig. 12B ). Choanosome constituted by a lax skeleton of ascending fibers of oxeas ( Fig. 12B ).

SPICULES. Oxeas microspined, slightly curved or flexuous ( Fig. 12C ), 260–(415, 176.6)– 840 µm ×7.5– (10, 2)– 12.5 µm, tips acerate or stepped ( Fig. 12D ); less common, smooth oxeas with same characteristics; very thin raphids, in thricodragmas, on the surface 22.5–(29.25)– 50 µm.

Remarks

The specimen belongs to the genus Myrmekioderma Elhers, 1870 characterized by a halichondroid organization of the choanosomal skeleton, a detachable ectosomal skeleton of acanthoxeas and by the presence of trichodragmata on the surface ( Hooper 2002).

To date, there are 11 species belonging to this genus, six of which have records only in the Atlantic Ocean ( Van Soest et al. 2019). Among the others, Myrmekioderma niveum (Row, 1911) presents a yellowish-white color and has just one category of smooth oxeas. Myrmekioderma dendyi ( Burton, 1959) was recorded from Madagascar ( Van Soest et al. 2019), but is characterized by an even surface with some digitate processes. Myrmekioderma pacificum Pulitzer-Finali, 1996 from the Bismark Sea has smooth and thicker oxeas (7–45 µm) with, sometimes, strongylote modifications (never found in this specimen) and longer trichodragmata (100–130 µm). Myrmekioderma tubercolatum (Keller, 1891) , found in the Red Sea, has a different morphology and the spicule composition is different, with the absence of trichodragmata and the presence of strongylote modifications.

The very peculiar external morphology, with the rounded plates and the oxea shape, fit the descriptions of Myrmekioderma granulatum ( Esper, 1829) . This species has a wide distribution in the Indian and Pacific Ocean ( Van Soest et al. 2019), with a corresponding high degree of variability, even concerning the presence or the absence of some spicule category ( Bergquist 1965).

Figures

Fig. 12. Myrmekioderma granulatum (Esper, 1829). A. Specimen PO98 in situ. B. Ectosomal skeleton. C. Microspined and flexuous oxea. D. Magnifications of the tips.