Farrea bowerbanki, Boury-Esnault, Nicole, Vacelet, Jean, Dubois, Maude, Goujard, Adrien, Fourt, Maïa, Pérez, Thierry & Chevaldonné, Pierre, 2017

Boury-Esnault, Nicole, Vacelet, Jean, Dubois, Maude, Goujard, Adrien, Fourt, Maïa, Pérez, Thierry & Chevaldonné, Pierre, 2017, New hexactinellid sponges from deep Mediterranean canyons, Zootaxa 4236 (1), pp. 118-134 : 124

Farrea bowerbanki n. sp. Boury-Esnault, Vacelet & Chevaldonné

Type-specimen. Sample VAL2-ACH-P15_ECH01. MNHN-HJV-03

Type-locality. Valinco Canyon, SW Corsica ( Western Mediterranean ), 383 m, 41.66148N / 8.7953E, 31/07/ 2014 .

Comparative material. Slides from specimens of the Ibero-Morrocan Gulf (BALGIM Cruise, 1984, Stn CP91-13, 34.3675N – 7.417W, 945 m).

External morphology. Several specimens were observed on ROV pictures and videos or by direct observations from the manned submersible ‘Remora 2000’ (Comex) in 2009, 2010, 2014 and 2016 ( Fig. 1 , 2 and 4 , Table 3). A complete specimen, designated as holotype, has been collected in 2014. The holotype ( Fig. 2 A, 2C) is 15 cm high, with a diameter of about 20 cm at its widest part. The body is formed by a branching and anastomosing system of tubes attached to the rocky substrate by a small basal plate, 2 cm in diameter. Two main tubes, 2 cm in diameter, arising from the basal plate, divide and merge several times, with distally infundibular openings 5–8 cm wide. The shape of these openings is reminiscent of a flower corolla. The thickness of the tube wall is about 1–2 mm. Color in life is white, with the basal plate and a short common basal part of the tubes, deep grey. The sponge is very fragile, and several parts of the tubes are broken on the preserved holotype which was very difficult to collect in a good state of preservation by the ROV. The other specimens observed, such as shown in Figures 2 B, 4A, 4B and 4D, have the same general shape, varying in size from a few centimeters to 40 cm. Several observed specimens were composed of a white living part and of a dead skeleton, colored in grey due to the deposit of mud.

Skeleton. The skeleton framework is a typical farreoid dictyonal type with smooth beams and spined spurs ( Fig. 2 D, 2F). Dictyonalia are formed in more than one layer. The meshes are mostly rectangular, sometimes square or triangular ( Fig. 2 E), with dictyonal beams 168–430/35–50 µm in size. The spurs are 90–210 µm in length, always spined and most often curved ( Fig. 2 F).

Figures

FIGURE 1. Distribution map of the two new species Farrea bowerbanki (grey squares) and Tretodictyum reiswigi (black circles) based on recent observations and collections as well as on literature records (see Table 3). 1. SW Corsican canyons (including Valinco canyon, the type locality of the two new species); 2. NW Corsican canyons; 3. French Riviera canyons and deep rocky banks; 4. Provence canyons and deep rocky banks; 5. Emile Baudot escarpment and seamounts; 6. El Loquet and de la Nau banks; 7. Galli Islands; 8. Malta escarpment; 9. Cape Santa Maria di Leuca; 10. Apulian escarpment; 11. Gulf of Athens; 12. Alboran Sea; 13. Rockall bank; 14. Cape Verde Islands.

FIGURE 2. Farrea bowerbanki n. sp. A: In situ view of the holotype before collection, Valinco canyon, Corsica, 383 m. B: Another specimen from the Valinco canyon, Corsica, at 425 m, next to a dead individual. The green dots in the center are laser beams 6 cm apart. C: preserved holotype. D, E: dictyonal framework near the base. F: beams and spur of a dictyonalium. G: pentactin. H: onychexaster. I, J: clavule. K: uncinate. A, B: Photos courtesy of AAMP.

FIGURE 4. Farrea bowerbanki n. sp. and Tretodictyum reiswigi n. sp. at the Cassidaigne canyon (Provence, NW Mediterranean), in areas exposed to industrial red mud discharge for decades. A: The highest density of F. bowerbanki observed so far, growing on (sub-fossil?) shells of the bivalve Neopycnodonte zibrowii, 580 m. In the center, the cold-water scleractinian coral Madrepora oculata. B: An isolated specimen of F. bowerbanki, ca 30 cm in diameter, and small specimens of T. reiswigi, at 536 m. C: High density of live T. reiswigi with a dead skeleton in the center, ca 480 m. D: Live specimens of T. reiswigi and F. bowerbanki at 521 m. The one on the lower left is apparently partly dead, as the distal parts accumulate red mud. A, B, D: Photos courtesy of COMEX S. A. C: Photo courtesy of MARUM - Center for Marine Environmental Sciences, University of Bremen, Germany.