Pyloderma latrunculioides (Ridley & Dendy, 1886)

Göcke, Christian & Janussen, Dorte, 2013, Demospongiae of ANT XXIV / 2 (SYSTCO I) Expedition — Antarctic Eastern Weddell Sea, Zootaxa 3692 (1), pp. 28-101 : 52-54

Pyloderma latrunculioides (Ridley & Dendy, 1886)

( Fig. 7 , Tab. 4 )

Pyloderma latrunculioides (Ridley & Dendy, 1886) : Hentschel 1914: 83.

Synonymy:

Halichondria latrunculioides Ridley & Dendy, 1886: 326, 1887: 6 , pl. 1, fig. 5, pl. 2, fig. 1, pl. 46, fig. 5. Van Soest et al. 1990: 49, fig. 82.

Inflatella latrunculioides (Ridley & Dendy, 1886) : Kirkpatrick 1908: 51. Dendy 1924: 370. Koltun 1964: 49, pl. 9, figs. 1, 2.

Material. 1 specimen from station 017-10 (SMF 11798), 602.1 m, 70° 23.94' S, 8° 19.14' W, 12.01.2008.

Description. Observed specimen almost complete, consisting of a rounded, almost heart-shaped lamella, about 25 mm in width, 60 mm in height and 10 mm in thickness. On the narrow lower side a breakpoint, probably indicating the former presence of a stalk-like attachment structure. Living sponge thus very likely growing upright, erect. One round pebble of 6 mm diameter laterally incorporated in tissue. Color of the sponge ex situ and in ethanol greenish grey. Its texture is soft fleshy. Epidermis very dense and velvety, bearing several small papillae, usually about 2 mm high. Few papillae seem to have oscular openings at their top, but these could be damages due to the trawling process. Apart from these, no distinct oscula exist. The epidermis is easily detachable. The choanosome is very cavernous and the whole sponge is traversed by several large aquiferous canals.

Skeleton: Basal skeleton made up of long plumose tracts consisting of a thick arrangement of oxeas. Tracts run towards the surface, where they attach to the epidermis. At least in parts, tracts becoming thicker towards the epidermis, forming bouquets or even palisade like paratangential structures underneath the surface. Thus, when detaching the surface, some small remains of the choanosomal tissue staying attached to the removed fragments. Ectosomal skeleton a dense multispicular layer of tangential oxeas ( Fig. 7 ).

Spiculation ( Tab. 4 ): Only spicule type rather straight oxeas ( Fig. 7 E) with characteristic articulated apices, in some cases quite elongate and characteristically bent ( Fig. 7 F–H). Oxeas 705–950 µm long with diameter of 15– 25 µm.

Remarks. A curious point about this species is the absence or presence of two different size classes of oxeas. In the key within his recent review van Soest (2002c) identifies the genus Pyloderma (of which P. latrunculioides is the type species) by the presence of two different size classes of oxeas. However, in the following redescription of the type species with designation of a lectotype he does not mention those size classes again, but only repeats the values given by Ridley and Dendy (1887), which can also be found in Tab. 4 . These values cover the whole range of variation, including any possible differing size classes, which are not distinguished (or reported explicitly) by Ridley and Dendy (1887). The presence of different size classes was again reported by Koltun (1964), who unfortunately does not distinguish his measurement values into these classes, but only reports the smaller size to have an average length of around 700 µm. Values given by Ríos (2006) are interestingly completely different and much smaller ( Tab. 4 ). The species thus might have a larger variability in spicule sizes than recognized so far, unless of course these sponges would show sufficient differences from the type specimen to establish a new species/ subspecies. Our specimen however clearly showed no large oxeas, but only the smaller kind, according to the description by Koltun (1964). Nevertheless very few fragments of large diactinal spicules (> 1000µm) were present, which might be oxeas of P. latrunculioides , but might as well be fragments of diactins from Bathydorus spinosus Schulze 1886 , which was represented by 4 specimens at that station. Thus it seems that the large oxeas may be extremely rare or even absent in Pyloderma , so that the presence of two size categories of oxeas is not obligatory for inclusion in the genus. The mere absence of one size class of oxeas is nonetheless not here considered a sufficient character for species determination or even a genus assignment. Thus, Pyloderma is best characterized by its shape and other skeletal features.

The species has a remarkably wide depth range, the type was sampled from a depth of 1100 m (van Soest 2002c), Koltun (1964) recorded it from similar depth 920–1080 m, but also gave the extension of 180 m in brackets. Ríos (2006) sampled the species from 141– 233 m. Our new specimen was trawled from a depth of 2190 m, which extends the species depth range significantly, so that it might be considered adapted to continental shelf habitats as well as to deep-sea environments.

Figures

FIGURE 7. Pyloderma latrunculioides (Ridley & Dendy, 1886), SMF 11798. A, habit alive ex situ. B, epidermis in topview. C – D, skeletal sections, the choanosome (ch) is in the center, surrounded by the ectosome (ec). E – H, Oxea and details thereof. Scale bars: A: 10 mm, B: 500 µm, C – D: 1 mm, E: 100 µm; F – H: 20 µm.

Tables

TABLE 4. Spicule sizes of Pyloderma latrunculioides (Ridley & Dendy, 1886). Values in µm are given as follows: minimum – mean – maximum (number of spicules measured). For comparison, values from Ridley & Dendy (1887), Koltun (1964) and Ríos (2006) are given.

parameter	SMF 11798	Ridley & Dendy (1887)	Koltun (1964)	Rios (2006)
Oxea I
length	705–834.5–950 (30)	700–1250	640–1400	410–585.22–960
diameter	15–18.1–21.25 (30)	22–31	26–31	10–14.96–27.50
Oxea II
length				182.5–278.57–475
diameter				5–7.13–10