A new species of Biemna (Porifera: Poecilosclerida) from Antarctica: Biemna strongylota

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1 J. Mar. Biol. Ass. U.K. (2006), 86, 949^955 Printed in the United Kingdom A new species of Biemna (Porifera: Poecilosclerida) from Antarctica: Biemna strongylota Pilar R os* and Javier Cristobo O *C/Mar a n8 39, 28, Ares, A Corun a, Spain. O Departamento de Zoolog a y Antropolog a F sica, Universidad de Alcala de Henares, Madrid, Spain. s: pilar.rios.lopez@gmail.com and fjcristobo@yahoo.es A new species of Biemna, Biemna strongylota sp. nov. is described from Antarctica. The new species is compared to other Antarctic species of Biemna, B. chilensis and B. macrorhaphis from which it di ers in that it possesses strongyle megascleres, instead of styles, and of the microsclere complement which includes microxeas, raphides and two categories of sigmata. INTRODUCTION Porifera represent one of the most important elements in the Antarctic biota due to their diversity and to their dominance in diverse areas (Sara et al., 1992). In the Antarctic benthos, at depths of 100 m these sponges can attain a biomass comparable to the highest found in tropical areas (Beliaev & Ushakov, 1957). This circumstance, together with the fact that these areas are rich in silica (Demospongiae and Hexactinellida), the great size Figure 1. Map of the Antarctic Peninsula and Bellingshausen Sea. Location of Biemna strongylota is indicated by * in the South of Gerlache Strait near Anvers Island.

2 950 P. R os and J. Cristobo New species of Biemna (Porifera) from Antarctica MATERIALS AND METHODS The material examined originates from the Gerlache Strait (Antarctica), S W (Figure 1), and was collected at a depth of 656 m by a 2.01m Agassiz trawl in February The specimens were preserved in 70% ethanol. In order to study the spicules, the organic matter was digested with nitric acid taken to boiling point following the methods of Ru«tzler (1978) and Cristobo et al. (1993). Spicules were examined with a Leica S440 scanning electron microscope. The data for spicule sizes are based on 25 measurements for each spicule category, comprising minimum, maximum and average lengths in micrometres (mm). The classi cation system adopted in this work is that proposed by Hajdu & van Soest (2002) in the Systema Porifera (Hooper & van Soest, 2002). The holotype and one paratype have been deposited in the Porifera collection of the Museo Nacional de Ciencias Naturales, Madrid (MNCN). The other paratype has been deposited in the collections of the Muse um National d Histoire Naturelle, Paris (MNHN). Figure 2. Biemna strongylota sp. nov. habitus (A) paratype 1; (B) paratype 2; and (C), holotype. of their spicules, their uniform distribution and the shortage of calcareous sponges, are the main aspects that characterize them. Desmacellidae are poecilosclerids lacking chelae. Noticeable in this group is the preponderance of toxic or dermatitis-producing sponges. Six valid genera are included in this family. Only two are recorded in Antarctic waters (Sara et al., 1992): Desmacella and Biemna. With respect to the taxonomic position of these two genera and the family, Hallman (1916) put forward the hypothesis that Desmacella Schmidt, 1870 (and Desmacelidae) was close to Axinellidae Carter 1875; while Gray, 1867 considered Biemna to be in a separate family Biemnidae which was closer to the Mycalidae. In accordance with Hajdu & van Soest (2002) we prefer to assign both Biemna and Desmacella to the Poecilosclerida and to the same family. Since Desmacellidae has priority over Biemnidae, the latter is designated a junior synonym. During the Spanish Antarctic expedition Bentart 03, sponges were collected from several locations, principally in the Bellingshausen Sea and surrounding areas such as the Gerlache Strait, at depths from 48 to 2045 m. The collection contained material of a species of Biemna, which appeared to di er from the two Biemna species recorded from Antarctic waters so far, B. chilensis Thiele, 1905 and B. macrorhaphis Hentschel, The present study gives the description of this new material. SYSTEMATICS Class DEMOSPONGIAE Sollas, 1885 Order POECILOSCLERIDA Topsent, 1928 Suborder MYCALINA Hajdu, van Soest & Hooper, 1994 Family Desmacellidae Ridley & Dendy, 1886 Genus Biemna Gray, 1867 Biemna strongylota sp. nov. (Figure 2) Type material Holotype: Museo Nacional de Ciencias Naturales, Madrid. MNCN 1.01/360. Paratype 1: Muse um National d Histoire Naturelle, Paris. MNHN DCL Paratype 2: Museo Nacional de Ciencias Naturales, Madrid. MNCN 1.01/361. Type locality: Gerlache Strait (Antarctic) S W, 656 m depth. Coll. RV Hespe rides, 25 February Three specimens. Muddy substrate with a little gravel and sand. External morphology Erect sponges, supported by a short stalk 5 to 10 mm long and 1.5 to 2 mm in diameter at the base. From the substrate to the sponge body, the stem gets gradually thicker until its diameter increases from 3 to 5 mm. The surface features in this stalk region are di erent from the rest of the sponge as it is smoother and nely hispid bearing small tufts of strongyles and microxeas. The height of the specimens varies between 34 and 36 mm, while the largest diameter is 10 to 17 mm. The surface of the main body is rough to the touch, caused by the ends of the choanosomal bres which give it a curly appearance. Neither pores nor oscules were observed. Colour white in ethanol (Figure 2). Skeleton The choanosomal skeleton (Figure 3) is formed by bundles of 3^6 spicules, surrounded by spongin, that

3 New species of Biemna (Porifera) from Antarctica P. R os and J. Cristobo 951 Figure 3. Biemna strongylota sp. nov. skeleton. splits dichotomously and form angles of 458, showing a plumo-reticulate appearance. The main bundles measure 70^200 (130) mm in length and are connected at points to secondary bundles, which are 20^110 (74) mm thick. These secondary bundles are formed of 1^4 strongyles at angles of 90^1508 in relation to the main bundles. Microscleres are very abundant around these bundles. The largest sigmata sometimes form small groups (sigmodragmata) while the raphides occur both loose in the choanosome and also in trichodragmata. The ectosomal skeleton is not apparent in most of the body in those specimens where only the ends of the bundles of strongyles are found at the surface. This ectosomal skeleton is composed only of microscleres, with the raphides

4 952 P. R os and J. Cristobo New species of Biemna (Porifera) from Antarctica Figure 4. Biemna strongylota sp. nov. (A) Strongyles; (B) raphide; (C) microxea; (D) sigma I; and (E) sigma II. occurring in trichodragmata and the microxeas loose and very abundant, sometimes forming groups in a disordered disposition. Sigmata of two sizes are also frequent. Spicules (Figures 4 & 5) Megascleres: strongyles are abundant, thick and straight or slightly curved at the tips, although a sharper curvature was observed in the basal third in some of them. One of the ends is smooth and the other has small granulations, which appear as indistinct spines. Some of them seem to get thinner towards one end, resembling styles. Size: 400^640 (553)19^30 (26.5) mm. Microscleres: fusiform microxeas are very frequent. Size: 58^86 (72)2 mm.

5 New species of Biemna (Porifera) from Antarctica P. R os and J. Cristobo 953 Figure 5. Biemna strongylota sp.nov.(a)strongyle;(b&c)detailofextremitiesof strongyle; (D) raphide; (E) microxea; (F) sigma I; and (G) sigma II. Raphides: very abundant and thin, both ends are sharp-pointed. They are grouped in trichodragmata. Size: 130^238 (179) mm long. Sigmata I (C-shaped sigmas) have the shape of a agellated sigma with both ends sharp-pointed, one opposite the other, and curved along the inner region. Size: 35^ 100 (82)2 mm. Sigmata II (C-shaped sigmas) are smaller, with short, sharp ends. They are slightly curved along the inner region. Size: 10^22 (16)1 mm. Etymology The species name refers to the presence of strongyles as megascleres.

6 954 P. R os and J. Cristobo New species of Biemna (Porifera) from Antarctica Table 1. Antarctic species of Biemna. Megascleres (mm) Microscleres (mm) Species Reference Habitus Styles Strongyles Sigmas Microxeas Raphides Distribution depth (m) B. chilensis Thiele, 1905 Palmatodigitate Desqueyroux, 1972 Rounded or irregularly digitated I. 46^55 II ^240 Calbuco 814^104611^33 22^85 160^398 Calbuco (191) Koltun, MacRobertson Land; Kemp Land; Enderby Land (300^603) Boury-Esnault & Van Beveren, ^97513^26 I. 60^823^3.5 II. 17^34 318^364 Kerguelen (95) B. macrorhaphis Hentschel, 1914 Spherical 664^101625^29 25^ ^4241 St Gauss (385) B. strongylota This work Stemmed 400^64019^30 I. 35^1002 II. 10^221 58^ ^238 Gerlache Strait (656) DISCUSSION According to Hajdu & van Soest (2002) only two of approximately 55 species belonging to this genus have been reported in Antarctic waters: Biemna chilensis Thiele, 1905 and B. macrorhaphis Hentschel, 1914, both studied by Burton (1932). Biemna chilensis Thiele, 1905, is a species with the following characteristics: styles present, raphides of one size and sigmata of two size-categories (Thiele, 1905). Apart from the original description, this species was also collected by Desqueyroux (1972) at the same location, by Koltun (1976) at three di erent Antarctic locations and by Boury-Esnault & Van Beveren (1982) from the Kerguelen Islands. The descriptions by each of these authors di er from the original description: Desqueyroux records only one category of sigmata with a wide size-range; in Koltun s description the styles and the raphides are much longer than those given by the other authors (1500 mm) and he does not mention the presence of sigmata; the spicular dimensions recorded by Boury- Esnault & Van Beveren are the most similar to the original description (Table 1). Biemna macrorhaphis Hentschel, 1914 has straight styles, curved along one-third of its length, sigmata with a wide size-range and very long raphides (Hentschel, 1914). The species studied in this report presents distinct and obvious di erences from both of these species because, apart from possessing strongyles as the main spicule type, the dimensions of sigmata, raphides and microxeas clearly di er from those of the other Antarctic species (Table 1). The distinction of Biemna and Neo bularia Hechtel, 1965 is subtle. Currently, both genera are distinguished essentially by their skeletal arrangement. Neo bularia has a rather uniform skeletal architecture with reticulate choanosomal skeleton. Biemna has a skeleton ranging from halichondroid-reticulate to hymedesmioid with sub-renieroid reticulate and plumose examples. Four species of Neo bularia have been described from Tropical Atlantic and West Paci c locations; Biemna occur in all oceans in a large depth range (Hajdu & van Soest, 2002). The new species has been assigned to the genus Biemna because of the presence of a plumo-reticulate skeleton, formed by bundles of strongyles surrounded by spongin, with dichotomous rami cations. The principal di erentiation between the new species and the other known species of the genus is the presence of strongyles as the main spicule type. There are two other species, Californian B. rhadia de Laubenfels, 1930 and Cuban B. cribaria (Alcolado & Gotera, 1986) in which strongylote forms may also be present. Biemna rhadia in addition to styli has strongyles, rhaphides and three size-classes of sigmas (de Laubenfels, 1932). Biemna cribaria has stronglyles, rhaphides and two size-classes of sigmas (Lehnert & van Soest, 1999). In Biemna strongylota sp. nov. the only megascleres found are strongyles; microscleres are microxeas, raphides and two forms of sigmas. In addition to this, it is necessary to point out the presence in our specimens of some strongyles that get thinner in one of their ends, giving an appearance of round-pointed styles. In addition to this, in our specimens some strongyles get thinner at one tip, giving an appearance of rounded styles. We are particularly grateful to Dr Rob van Soest from the Zoological Museum, University of Amsterdam (ZMA), for his recommendations and his many positive comments and Clare Valentine from the Natural History Museum, London (BMNH) for thoughtful review of the manuscript. This work is part of the projects: Spanish Ministry of Science and Technology (REN ANT; REN /ANT). The useful comments by two anonymous referees are also gratefully acknowledged. REFERENCES Alcolado, P.M. & Gotera, G.G., Nuevas adiciones a la fauna de por feros de Cuba. 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