Protosuberites mereui Manconi, sp. nov.

Protosuberites mereui Manconi sp. nov.

Figs 1–4; Tables 1, 3, 4

Material examined. Holotype: MSNG 59362, BUEMARCAVE 21, Bue Marino Cave, 40°14'48.19" N, 9°37'22.76"E, southern branch, mixohaline pool ‘ Lago degli Specchi’, Eastern Sardinia, western Tyrrhenian Sea, ca. 0.30–1 m of depth, R. Manconi legit, vi.2008.

Paratypes: MSNG 59363, BUEMARCAVE 22, ibid.; MSNG 59364, BUEMARCAVE 30, ibid.; BMNH 2016.10.28.1, PROTOBM 0 3, ibid.; BMNH 2016.10.28.2, PROTOBM 0 4, ibid.; BMNH 2016.10.28.3, PROTOBM 0 5, ibid.; BMNH 2016.10.28.4, PROTOBM 0 6, ibid.; BMNH 2016.10.28.5, PROTOBM 0 7, ibid.; BMNH 2016.10.28.6, PROTOBM 0 8, ibid., P. Melis legit, viii.2013.

Other material: PROTOBM01, 0 2, 0 9, ibid., P. Melis legit; BUEMARCAVE, several specimens, slides and stubs, ibid., Daniela Demurtas legit, R. Manconi’s collection at DIPNET.

Comparative materials. Details of all material studied from other comparable Protosuberites species and from the literature are given in Table 1. In addition, Protosuberites cf. epiphytum (Lamarck, 1815) was studied from the Mediterranean Sea G. Pulitzer-Finali Collection at DISTAV, slides: TRI.274, Porto Tricase, Apulia, conglomerates, 30 m depth, 24.ix.1970; PC.125, Taranto, Mar Piccolo, Apulia, encrusting on stone, 0.5 m depth, 18.vii.1973; GAR.74, Gargano, Baia di Campi, Apulia, rocks and mud, 2–10 m depth, 15.ix.1971.

Description. Growth form encrusting, very thin (ca. 1–2 mm in thickness) in patches (from a few cm² up to 1 m ²) on rocky substrata. Colour light yellow in vivo, whitish after preservation in ethanol (Fig. 2). Consistency firm. Surface hispid due to tips of spicules, with subdermal canals and scattered oscules. Ectosomal skeleton lacking special architecture, with distal tips of spicules supporting the dermal membrane. Choanosomal skeleton of erected brushes of tylostyles from single in thinner portions to loosely arranged as tylostyles bundles/tufts in the thicker portions (Fig. 3 d). Basal spongin plate well developed in the surroundings of resting stages and in general armed by tylostyles heads. Megascleres tylostyles 100(295.3)650 x 3 (5.03)10 µm (n=200; Table 3) belonging to three length size classes 130–180 µm; 280–330 µm; 380–430 µm, straight to slightly bent, frequently sinuous, entirely smooth, with heads from rounded to suboval (4–11 µm in width, Fig. 3 a, b, c). Very rare small tylostyles with mushroom-like head, sinuous thin and short shaft (110–232 x 0.5–1 µm) also present. Very rare subtylostyles also present (Table 3). Resting bodies (gemmule-like) suboval, flat, firmly adhering to the substratum and scattered singly or in small groups (2–3) (Fig. 4). Theca of resting bodies as sublayered compact spongin (ca. 12 µm in thickness) with a smooth outer surface not armed by spicules (Fig. 4 a1). Active resting bodies with evident Species Spicule Length x Thickness Resting Geographic Presence in References

type µm bodies range brackish

water mereui sp. nov. Tylostyles (100– 295.3 –650) x (3– 5.03 –10) YES W-Mediterranean Sea YES Present Paper

(very rare

subtylostyles)

rugosus (Topsent, 1893) Tylostyles (200–1200) x 8 (shaft) x 12 (head) NO Mediterranean Sea NO Topsent, 1893 prototipus Tylostyles (162–417) x (5–7) NO Black Sea NO Swartschewsky, 1905 Swartschewsky, 1905

denhartogi Tylostyles (110– 258.7 –456) x (4– 6.3– 11) NO N-Atlantic Ocean NO Soest &Kluijver, 2003 Soest & Kluijver, 2003 (rarely 600) Ackers et al., 1992 ectyoninus Subtylostyles (97– 204.97 –320) x (2.5– 4.71– 9.5) NO N-Atlantic Ocean NO Present paper Topsent, 1900) Tylostyles (145–400) x (7–13) Mediterranean Sea cf. epiphytum Tylostyles (100–300) x (4–7) NO N-Atlantic Ocean NO Topsent, sensu Topsent, 1900) 1900 P. Denhartogi

modestus Tylostyles (400–1050) x (8–14) NO N-Atlantic Ocean NO Pulitzer-Finali, 1978 Pulitzer-Finali, 1978) Mediterranean Sea incrustans Tylostyles (225– 320.7 –477) x NO N-Atlantic Ocean NO Present paper Hansen, 1885) (7.38– 10.02– 15.11) Mediterranean Sea ferrerhernandezi Tylostyles (135.3– 510.1 – 965.6) x NO N-Atlantic Ocean NO Boury-Esnault & Lopes, Boury-Esnault & Lopes, 2.7– 8– 20.7 1985 1985)

aquaedulcioris Tylostyles, 330 x 5 YES Bay of Bengal YES Annandale, 1914 Annandale, 1914) subtylostyles, S-Atlantic Ocean

oxeas (rare bent

centrotylotes)

collaris Tylostyles ±800 NO Laut Banda YES Annandale, 1924 Annandale, 1924) Laut Jawa

Wallacea

lacustris Tylostyles (560–580) x 8 YES Bay of Bengal YES Annandale, 1915 Annandale, 1915) Subtylostyles Indian Ocean

single foraminal aperture and collar closer to the distal part of the suboval theca (430 µm, total length with collar) (Fig. 4). Foramen with well-developed, thin-walled, transparent collar (ca. 80 µm in length) (Fig. 4). Inactive resting bodies present in the same specimens with no foraminal aperture and no collar, but bearing a small area apparently devoid of cells closer to the distal part of the longer axis of the suboval theca (Fig. 4).

Habitat and topographic distribution. The population of Protosuberites mereui sp. nov. occurs as scattered facies (up to 1 m ² covered area) in mixohaline pool water within the totally dark main tunnel of the estuarine/ anchialine southern branch of the Bue Marino Cave. In this part of the cave, salinity varies from 24 ‰ up to 39.6 ‰, depending on the point, depth and date of sampling. Substrata range from vertical limestone walls and large boulders to artificial substrata (plastic) at 0.5–1 m of depth. The new species share the same microhabitat with the serpulid Ficopomatus enigmaticus (Fauvel, 1923) and sometime with unidentified haplosclerid sponges. The kamptozoan Barentsia gracilis M. Sars, 1835 was strictly associated with the suberitid sponges.

Geographic range. Protosuberites mereui sp. nov. is only known from the type locality Bue Marino Cave in the central-eastern Sardinian Karst, western Tyrrhenian Sea.

Etymology. The species is dedicated to the Sardinian speleologist and photographer Luigi Mereu, who died prematurely during the exploration of a terrestrial cave, in recognition of his key contribution in the present research.