Cornulum globosum, Lehnert, Helmut & Stone, Robert P., 2015

Lehnert, Helmut & Stone, Robert P., 2015, New species of sponges (Porifera, Demospongiae) from the Aleutian Islands and Gulf of Alaska, Zootaxa 4033 (4), pp. 451-483 : 453-455

Cornulum globosum n. sp.

( Fig. 2 , Table 1 )

Material examined. Holotype: ZSM 20150381, collected by Brian Knoth with a research survey bottom trawl from the FV Ocean Explorer; 18 June 2012, 226 m depth, 28.2 km south of Yunaska Island, eastern Aleutian Islands, North Pacific Ocean (52°17.3400' N, 170°48.2340' W). Water temperature = 4.2°C. Complete specimen in ethanol.

Description. Habitus: Globular, pale yellow colored sponge, 9–11 cm in diameter ( Fig. 2 A). The sponge is attached firmly to a fragmented pebble. The ectosome is a thick parchment-like membrane and the surface is covered with numerous fistules ( Fig. 2 B). These fistules are hollow, up to 12 mm high and 6 mm wide. The bottom of the fistule opens into the choanosome but they are closed on top.

Skeletal structure: The ectosome is fastened to the choanosome by polyspicular tracts which fan out into the ectosome and stick to the ectosome when it is detached ( Fig. 2 B) and, are then visible to the unaided eye. These polyspicular tracts are 4–6 mm long, with a diameter of 800–1100 µm, consist of choanosomal styles and are irregularly spaced. In some places up to 6 spicule tracts originate from the ectosome with no particular distance and in other places there are 4–5 mm or more in between single tracts. The ectosomal membrane is somewhat transparent, especially on the bottom side of the sponge where black sediment particles are visible within the sponge. The ectosome contains mainly tylotes except in places where choanosomal polyspicular tracts merge into the ectosome, and here ectosomal tylotes and choanosomal styles are observed together. Ectosomal tylotes are arranged paratangentially with the axis mostly horizontal but, within this plane facing in all directions. The ectosomal membrane with the attached spicule tracts has a high spicule density and is very resilient, while spicule density in the choanosome is much lower and therefore the choanosome is soft and easily torn. Spicule arrangement in the choanosome is halichondroid, only short and vague tracts are recognisable.

Spicules: Spicules are entirely smooth tylotes, 340–920 x 12–18 µm ( Fig. 2 C), in the ectosomal membrane, choanosomal smooth styles are 956– 1180 x 18–21µm ( Fig. 2 C). Microscleres are palmate isochelas measuring 52– 67 µm ( Fig. 2 D) and two size categories of toxa: thick toxa, 112–135 x 9–11 µm ( Fig. 2 E) and thin toxa, 180–210 µm ( Fig. 2 F).

Discussion. Entirely smooth tylotes would be a new characteristic within the genus Cornulum but do occur in Tedaniophorbas de Laubenfels, 1936. We excluded the possibility of the new species belonging to the monotypic Tedaniophorbas because it simply differs in too many characters. Tedaniophorbas is non-fistular and has a welldeveloped skeleton of spongin fibers without coring or echinating spicules, megascleres are smooth tylotes only, and microscleres consist of isochelas. Contrastingly, the species described here is fistular, lacks a spongin skeleton without inclusions, and additionally has choanosomal styles and different categories of toxas. Accordingly, we assign the new species to Cornulum since it more closely conforms to that genus and requires only the single modification to allow for smooth tylotes.

The WPD recognizes ten valid species in the genus Cornulum . Cornulum are massive or encrusting sponges of the family Acarnidae with erect fistules or pronounced pore areas, with apically spined tylotes or strongyles forming both tangential and plumo-reticulate choanosomal skeletons, sometimes together with choanosomal styles or aniso-strongyles ( Hooper, 2002a). We compare the new species with four species known from the North Pacific and the North Atlantic Oceans. Comparison of spicule categories and their dimensions are given in Table 1 . The remaining six species are described from the Antarctic, Indonesia, the Philippines, New Caledonia, the Caribbean and Brazil and were not considered given obvious zoogeographic reasons. Cornulum globosum n. sp. differs from the species compared with in the following characters:

C. clathriata : North Atlantic Ocean, Arctic Ocean, and Northwest Pacific Ocean (Commander Islands in Russia, western Bering Sea, and the central Aleutian Islands). Bush- or fan-shaped, ectosomal tylotes are shorter and thinner, spherical isochelae that are smaller, and toxa of different size categories.

C. enteromorphoides : North Atlantic Ocean (around Greenland). A cylindrical sponge, “light with a tint of yellow” ( Fristedt, 1887, p. 448), megascleres are microspined, both categories being shorter, two categories of isochelae, no toxa.

C. textile : North Atlantic Ocean and Northwest Pacific Ocean (Sea of Okhotsk). A lobate to digitate sponge, ectosomal tylotes have microspined ends and are shorter, choanosomal styles may have microspined bases and are shorter, isochelae are smaller, no toxa.

C. tubiforme Northwest Pacific Ocean (Sea of Okhotsk, Sea of Japan, and East Sea). A tube-shaped sponge with oxeote ectosomal spicules which are shorter and thinner, no choanosomal styles, smaller isochelae, and only one category of toxa.

C. globosum is somewhat unusual within the genus in having smooth tylotes but Hooper (2002a) mentions that C. textile also has smooth microspined tylotes and writes (p. 419) ”…all members of Cornulum share the microspined condition of megascleres (occasionally verging towards entirely smooth), ….”, so smooth ectosomal spicules have already been recorded for the genus.

Etymology. From the Latin globosum—referring to the sponge’s globular habitus.

+ Measurements are from Hooper (2002a).

++ The WPD lists the valid species name as C. tubiforme Burton, 1935 . Burton himself however, offers two names: in the list of species (p. 63) it appears as “43. C. tubiformis n. sp. ” but then when describing the species (p. 73) he indicates as “ Cornulum tubiformes sp. n. ”

Figures

FIGURE 2. Cornulum globosum n. sp. A. Globular holotype with fistules and parchment-like ectosome, grid marks are 1 cm. B. Detached part of ectosome with polyspicular tracts facing to the left. Scale bar is 2.5 cm. C. Smooth choanosomal styles (lower left to upper right) and smooth tylotes (horizontal in center) with scattered microscleres. Scale bar is 100 µm. D. Isochela. Scale bar is 10 µm. E. Thick toxon. Scale bar is 10 µm. F. Thin toxon. Scale bar is 10 µm.

Tables

TABLE 1. Spicule categories and measurements of Cornulum from the North Pacific and North Atlantic Oceans. All measurements are in µm.

species	tylotes	styles	palmateisochelae	toxa
clathriata (Koltun, 1955)	microspined ends, 280–420 x 6–8	215–2000 x 18–33	spherical, 17–25	two categories; large, 55–220 & small, 10– 12
enteromorphoides Fristedt, 1887	microspined ends, 300–335, thickness not provided	acanthostyles, 400, thickness not provided	two categories; large, 70 & small, 25	none
textile Carter, 1876 +	microspined ends, occasionally smooth, 290–370 x 8–14	styles to anisostrongyles, microspined or smooth bases, 390–480 x 15–22	11–15	190–310 x 1–-3
tubiforme Burton, 1935 ++	oxeote, mucronate tornotes, 280 x 10	none	280 (“0.28mm”, p. 73)	none
globosum n. sp.	340–-920 x 12–18	956–1180 x 18–21	52–67	two categories; thick, 112–135 x 9–11 & thin, 180–210