Discodermia adhaerens, Van Soest & Meesters & Becking, 2014

Van Soest, Rob W. M., Meesters, Erik H. W. G. & Becking, Leontine E., 2014, Deep-water sponges (Porifera) from Bonaire and Klein Curaçao, Southern Caribbean, Zootaxa 3878 (5), pp. 401-443 : 416-419

Discodermia adhaerens new species

Figures 10a–e , 11a–f

Material examined. Holotype: RMNH Por. 9241, Caribbean Netherlands, Bonaire, Kralendijk Pier (Dive 2), 12.1469°N 68.2821°W, on a coral rock wall at 146m, coll. L.E. Becking & E. Meesters, field nr. BON1/ BDR012 , 30 May 2013.

Description. Bright orange sponge, thinly to massively encrusting limestone rockwalls ( Fig. 10a ). Size several dm 2 in lateral expansion, about 2–3 mm in thickness. The holotype consists of a dozen small fragments ( Fig. 10b ), each approximately 1 cm 2 or less, sucked off from the rock. Surface smooth. No apparent oscules visible in situ nor in the fragments. Consistency hard.

Skeleton. An ectosomal skeleton of closely packed discotriaenes ( Fig. 10c ) with margins of neighbouring spicules overlapping. Desma skeleton strongly zygosed ( Fig. 11e ) with thick, strong tubercles. Smaller discotriaenes and subdermal desmas show occasional zygosis ( Fig. 11a 1 ). Auxiliary spicules long thin oxeas ( Fig. 11c, 11c 1 ), not prominent.

Spicules. Discotriaenes, desmas, oxeas, microrhabds.

Discotriaenes ( Figs. 10b, 10d , 11a ) showing an extreme variation in shape and outline, from an almost perfectly rounded shape (rare) to a deeply notched irregular form. The outer surface is usually smooth, but may bear a group of central warts (verrucose condition). The discs vary also considerably in size, 130– 202 –350 x 100– 155 – 280 µm. The rhabds are conical and relatively short 24– 34 – 41 µm, and equally wide at the base.

Desmas ( Figs. 10e , 11b ) are large and robust, cladomes 320– 428 – 520 µm, shafts smooth, varying between 40 and 66 in thickness, and the arms are heavily tuberculated; juvenile desmas are tetraclones ( Fig. 10e , 11f ).

Oxeas ( Figs. 11c, 11c 1 ), thin, curved, with wispy thin endings, relatively rare and often broken in the preparations, 670– 795 –910 x 5– 6.3 – 7µm.

Acanthomicrorhabds ( Fig. 11d ), densely distributed on the surface of the discotriaenes and strewn in the interior, in a single rather uniform size range, 15– 20 – 25 µm.

Ecology and distribution. On vertical walls, in the upper dysphotic zone, at Bonaire.

Etymology. adhaereo (L.) = to cling to, referring to the habit thinly encrusting on rocks, which is so far unknown in the genus.

Remarks. From the Western Atlantic several Discodermia species have been reported, but only two species are currently considered accepted unequivocal species of Discodermia , viz. the type species of the genus, D. polydiscus ( Bowerbank, 1869) , originally from Saint Vincent, subsequently reported from Barbados ( Van Soest & Stentoft 1988), and D. dissoluta Schmidt, 1880 from Cuba, subsequently reported from various localities across the Caribbean, and also herein (see Table 2 and Fig. 21c ). Our new species differs from these two species by the encrusting growth form, whereas D. polydiscus is cup-shaped and D. dissoluta a group of cylinders. Further clear differences are the single category of microstrongylote microscleres, whereas the two other species have separate categories of microxeas and microstrongyles, and the very short rhabds of the discotriaenes which are only about 40 µm, while those of the other two species are always over 100 µm, even up to 170 µm in D. polydiscus . An interesting feature of our new species is the presence of proliferated discotriaenes, which appear to form a link with the underlying desma-skeleton, providing zygosed margins locking into the peripheral desma skeleton. No such zygosed discotriaenes have been reported in the literature so far, but possibly these have gone unnoticed in other species.

A fourth Caribbean Discodermia species might be D. inscripta ( Schmidt, 1879 as Collinella ), but the type material is deciduous and no discotriaenes or microscleres have been found in it ( Pisera & Levi 2002), making the species incertae sedis. On the eastern side of the Atlantic, several further species have been reported, D. ramifera Topsent, 1892 , D. verrucosa Topsent, 1928 , and D. polymorpha Pisera & Vacelet, 2011 . None of these species conforms closely to our new species in shape and spiculation.

Figures

FIGURE 1. Map showing the positions of Bonaire and Klein Curaçao (Southern Caribbean), where the present collections were obtained. Insets show details of locations and course of dives 2–4 of the Curasub.

FIGURE 10. Discodermia adhaerens n. sp., holotype RMNH Por. 9241, a. habit in situ, b. preserved holotype fragments, c. ectosomal discotriaenes, d. small discotriaene, showing triaxial canals, e. juvenile desma.

FIGURE 11. Discodermia adhaerens n. sp., holotype RMNH Por. 9241, SEM images of the spicules, a. various discotriaene shapes, a1. subdermal discotriaenes zygosing with other discotriaenes and with desmas, b. desmas, c. oxea, c1. details oxea endings and middle part, d. acanthomicrorhabds, e. desma skeleton, f. overview of discotriaenes and juvenile desmas.

FIGURE 21. Images of specimens belonging to already known species, briefly characterized in Table 2. All scale bars 1 cm, a. Characella aspera (Sollas, 1886) photographed after collection, from the front, a1. ditto photographed from the side, b. Theonella atlantica Van Soest & Stentoft, 1988, two specimens after collection, c. Discodermia dissoluta Schmidt, 1880, after collection, d. Corallistes typus Schmidt, 1870, after collection, e. Aciculites cribrophora (Schmidt, 1880), in situ, e1. ditto, after collection, f. Gastrophanella implexa Schmidt, 1870, in situ, f1. ditto, after collection, g. Daedalopelta nodosa (Schmidt, 1879), after collection, h. Neopelta perfecta Schmidt, 1880, after collection, i. Leiodermatium lynceus Schmidt, 1870, in situ, j. Hamacantha sp. after collection, k. Phakellia folium Schmidt, 1870, after collection.