Demospongiae of ANT XXIV / 2 (SYSTCO I) Expedition — Antarctic Eastern Weddell Sea Author Göcke, Christian Author Janussen, Dorte text Zootaxa 2013 3692 1 28 101 journal article 10.11646/zootaxa.3692.1.5 ddffc7b3-2654-49ec-b046-f32bc78af2d6 1175-5326 249019 136660B8-7DCC-490E-AB79-46546CC18E40 Calyx cf. arcuarius (Topsent, 1913) ( Fig. 24 , Tab. 20 ) Calyx arcuarius (Topsent, 1913) : Burton 1932:277, 1934:14. Koltun 1964: 106, pl. 14, figs. 8–10, 1976: 196. Synonymy: Calyx stipitatus Topsent, 1916: 171, 1917: 81 , pl. 4, fig. 13, pl. 6, fig. 24. Burton 1929: 422, pl. 5, figs. 5, 6. Gellius arcuarius Topsent, 1913: 638 , pl. 6, fig. 11. Vagocia arcuaria (Topsent, 1913) : de Laubenfels 1936: 133. Material. Fragments of probably 2 different specimens from station 048-1 (SMF 11815, 11822), 602.1 m , 70° 23.94' S , 8° 19.14' W , 12.01.2008 . Description. Fragments of two distinct differing colors, whitish yellow and brown, possibly originating from two different specimens. Freshly sampled SMF 11815 ( Fig. 24 A) a relatively large, fan-shaped sponge, possibly incomplete. Sponges lamellar, fan-shaped, in life possibly consisting of multiple fans originating from one stalk. Fans often flat, but also folded, forming peaks and basins. Edge of lamella usually sharp, thickness of lamella about 4 to 5 mm . Surface of upper side ( Fig. 24 B) of lamella often smoother than the underside (fig. 24 C), which is quite uneven with branching folds running disorganized, but generally parallel from center to edge. Between folds, pores present. Surface of upper side bearing distinct growth rings, which run more or less parallel to outer edge. Between growth rings, discrete lines of pores present, following shape of the growth rings. Without distinct oscules. A stalk present ( Fig. 24 D), possibly connected to hard substrate, indicated by remains of stony material. Skeleton: Skeleton a weakly organized isotropic reticulation ( Fig. 24 I–J). Edges of meshes consisting of up to 5 spicules, these only very rarely unispicular. Partly, with spicule tracts extending quite far throughout the sponge, not completely penetrating. Within choanosome, several small aquiferous canals present, usually about an oxea length in width. Ectosome of upper side a dense tangential crust of oxeas, about 5 to 10 spicules thick, strongly connected to choanosomal skeleton below, not mechanically detachable. In surface view a well developed structure of mostly parallel, sometimes intercrossing oxeas visible, covering the sponge very closely, leaving open only distinct oscules/pores surrounded by rims of oxeas ( Fig. 24 E–F). Ectosome of underside usually less distinct, a specialization of the skeleton forming a closure to the surface, in topview recognisable as a rather well organised reticulation ( Fig. 24 G–H). Surface skeleton of the underside not detachable. Spiculation ( Tab. 20 ): Sole spicules oxeas ( Fig. 24 K–L), 290–375 µm in length and 8.75–25 µm in diameter. Many oxeas with quite unusual characteristic shape: with two distinct kinks, forming a middle and two sharppointed end pieces, each separated by angles of about 30°. These oxeas abundant among variable spicules, also including oxeas with one kink as well as absolutely straight ones. TABLE 20. Spicule sizes of Calyx cf. arcuarius (Topsent, 1913) . Values in µm are given as follows: minimum–mean– maximum (number of spicules measured). For comparison, values from Topsent (1913), Topsent (1916), Burton (1932), Koltun (1964) and Campos et al. (2007a) are given. *) reported as Calyx stipitatus Topsent, 1916 . parameter SMF 11815 SMF 11822 Topsent (1913) Topsent (1916) * Burton (1932) * continued.

Oxea
length	290–334.5–375 (30) 300–329.3–365 (30)	350–400	300–325	180–280
diameter	8.75–21.3–25 (30) 16.25–20.9–23.75 (30)	12–15	17	11–18
Toxas
length	70–110
diameter	1–2

parameter	Koltun (1964)	Campos et al. (2007a)
MCNPOR 1954 MCNPOR 1964	MCNPOR 3135
Oxea
length	180–400	190–216.2–237.5 209–205–294.5	190–225–256.5
diameter	11–19	16.1–19.4–23 11.5–17.2–19.6	11.5–18.4–20.7
Toxas
length	70–160	78.2–115.2–147.2 69–119.1–181.7	80.5–129.8–174.8
diameter	1–5	1.2–4.0–6.9 1.2–3.2–4.6	1.2–3.7–5.8

Remarks. Calyx arcuarius is a complicated species because several reports and synonymizations have led to a wide, rather inconsistent species diagnosis including several variations (Topsent 1913; Topsent 1916; Burton 1932; Koltun 1964; Campos et al . 2007a). One major point in the taxonomic history of the species is the synonymization of Calyx stipitatus Topsent, 1916 with C. arcuarius by Burton (1932), who stated that the mere absence of toxas in a sponge is not sufficient as a discriminating character between two otherwise similar species. This was also stressed by Koltun (1964) who reported specimens with high densities of toxas as well as those with a low density of toxas and some which had no toxas at all. Our specimens show some differences to those previously reported. First, the sizes of the oxeas, especially their diameters, are larger than those in most records (see Tab. 20 ). Second, the density of spicules in our sponges is higher than in most earlier records, especially in comparison with the sections figured in Campos et al . (2007a). These higher densities are especially significant in the ectosome; crustlike ectosomal skeletons are not present in any specimen recorded so far. Furthermore, all specimens known so far are in the shape of thin lamellae with a stalk on one end, growing erectly on a hard substrate, or as thin tubes. Our specimens are aberrant in this respect as they were probably cup- or plate-shaped, attached to the ground with a stalk, growing in a more or less central position of the plate’s underside. These differences led to the question, whether our specimens represent a new species. After detailed consideration, we decided not to erect a new species based on our findings. In the light of the already known high variability of C. arcuarius and many similarities to our sponges, it seems more reasonable to interpret our specimens as variations of C. arcuarius , as the differencesalthough clear—do not seem sufficient for the erection of a new species. FIGURE 24. Calyx cf. arcuarius (Topsent, 1913) , SMF 11815. A, habit alive, ex situ. B–D, fragments in ethanol, B, underside of fan, C, topside, D, stalk. E–F surface of the sponges upside in overview and in detail, G–H surface of the sponges underside in overview and in detail. I, skeletal section, with ectosomal arrangement at the top. J, close-up of skeletal section. K–L oxea in SEM. Scale bars: A: 30 mm, B–C: 20 mm D: 10 mm, E, G: 5 mm, F, H: 1 mm, I–J: 1 mm, K–L: 30 µm. Another very similar species which has to be considered here is Calyx imperialis (Dendy, 1924) . It has a general shape very similar to our specimens, being more plate- to cup-shaped with a stalk and very thin wall. Also it has a dense, crust-like ectosome (Dendy 1924). On the other hand, its oxeas of about 240 x 16 µm are smaller than those in our specimens. Also it has sigmas as microscleres. The surface of the outside/underside bears few strong ribs, the surface of the inside/upper side shows a “curious pock-marked appearance” (Dendy 1924). Furthermore, the species has so far only been recorded from New Zealand . Thus, in spite of some strong similarities apparent to our new specimens, we consider the differences to be stronger than those between the new specimens and C. arcuarius .