Polymastiidae and Suberitidae (Porifera: Demospongiae: Hadromerida) of the deep Weddell Sea, Antarctic * Author Plotkin, Alexander S. Author Janussen, Dorte text Zootaxa 2008 1866 95 135 journal article 10.5281/zenodo.183878 810a9086-292c-4ca4-8075-91312cfac96e 11755326 183878 Genus Polymastia Bowerbank, 1864 Diagnosis (emended from BouryEsnault 2002 ): Thickly encrusting sponges of spherical, hemispherical or cushion shape, always with papillae. Choanosomal skeleton is composed by radial tracts of principal spicules between which free spicules are scattered. Cortical skeleton constituted by at least two layers, the superficial palisade of small tylostyles and the lower layer made of intermediary spicules, lying tangential to the surface. The principal spicules can be tylostyles, subtylostyles, styles, and strongyloxeas, intermediary spicules are most often tylostyles, and cortical spicules are always tylostyles. Remarks to diagnosis: At the moment 73 from 117 accepted polymastiid species are placed in Polymastia (van Soest et al. 2005 ), and some of them demonstrate noticeable discrepancies with the currently accepted diagnosis of the genus (see, e.g. KellyBorges & Bergquist 1997 ), that calls for its considerable reevaluation. Since we did not aim to revise Polymastia in the present study, the emendations of the diagnosis given in Systema Porifera ( BouryEsnault 2002 ) are minimized. Meanwhile, two Antarctic species, P. invaginata Kirkpatrick, 1907 and P. zitteli ( Lendenfeld, 1888 ) , concerned below, bear the features which somehow contradict the accepted diagnosis of Polymastia , the contradiction has not been previously emphasized. The dissimilarities include a singlelayered cortex of the former species and the reticulated choanosomal skeleton of the latter. However, as the species in question share some other diagnostic features of Polymastia , we retain them as is, until the revision of the whole genus can be completed. Type species: Spongia mamillaris Müller, 1806 (by monotypy). Polymastia invaginata Kirkpatrick, 1907 ( Figs. 4–5 , Tables 2–3 ) Synonymy Polymastia invaginata — Kirkpatrick 1907 : 271 ; 1908: pp. 15–16, pl. XII(1b), pl. XIV (5–15a); Burton 1929 : 446 ; 1932: 338; Koltun 1964 : 26 , pl. IV(10–14); 1976: 168; BouryEsnault and van Beveren 1982 : 36 –37, pl. IV (13–14), figs. 9d, e, f. Polymastia invaginata var. gaussi — Hentschel 1914 : 49 , Taf. V, Fig. 4 . Material examined SMF 10540–10541 ( 2 specimens ): PS61/1323; SMF 10542 ( 4 specimens ): PS61/1343; SMF 10543 ( 1 specimen ): PS61/1419; SMF 10544–10545 ( 2 specimens ) and 10546 ( 19 specimens ): PS61/1432; SMF 10547 ( 1 specimen ): PS67/0572; SMF 10548–10551 ( 4 specimens ): PS67/0747; SMF 10552 ( 1 specimen ): PS67/07811; SMF 10553 ( 4 specimens ) and 10554 ( 2 specimens ): PS67/10211; SMF 10555 ( 1 specimen ) and 10556 ( 4 specimens ): PS67/1217. Description External morphology. Sponges are cushionshaped or hemispherical, always attached to the substrata (figs. 4A–C). Their diameter may reach 3.7 cm and thickness is up to 2.9 cm . The surface is usually densely hispid, its colour varies from dark brown to dark grey due to the sediment particles incorporated between protruding spicules. The upper surface bears one or very rarely few papillae, light brown or grey coloured and measuring 2–13 mm in length and 2–8 mm in diameter. Papillae are usually slightly sunken below the surface hispidation, occasionally being located inside a small pit within which the surface is smooth and pale. Oscula are opened at the papillae summits and ostia are scattered over the walls of the papillae. No ostia can be seen on the surface. The cortex is pale grey to whitish, hardly detachable and rather resilient. The choanosome is grey to beige, heterogeneous in consistency. Skeleton. The main choanosomal skeleton is constituted by the radial tracts of principal spicules running from the sponge base to the surface, entering the cortex and diverging into bouquets (figs. 4D, E). The additional choanosomal skeleton is composed of small spicules scattered between the main tracts. These small spicules lie singly or grouped in stellate bundles (fig. 4F). Concentration of the scattered spicules under the cortex is higher than in the lower choanosome. The cortex, measuring 600–1560 µm in thickness, consists of the palisade of small spicules overlapped by the bouquets of the main tracts (fig. 4G). The latter are reinforced by extralong spicules making up a surface hispidation, the thickness of which is 100–2700 µm. In the cortical bouquets of some sponges we also observed a few remarkable sceptrelike spicules, which were probably modified tylostyles (fig. 4H). Spicules. Altogether 1267 spicules from 16 specimens were measured. Frequency distribution of length revealed three main categories of monactins, corresponding to extralong spicules of the hispidation, principal spicules of the main tracts, and small spicules forming the additional choanosomal skeleton and the cortical palisade (fig. 5A). The fourth category was constituted by the infrequent sceptrelike spicules. Summarizing results of spicule measurements are given in the main text below, indicating the total number of spicules measured for each category ( n ). Particular results of spicule measurements for each specimen (sceptrelike spicules excluded) are given in table 2. Principal spicules vary from styles to tylostyles (fig. 5B). They are mainly straight, often fusiform and measure: length 10261568 2186, proximal diameter 510.518 µm, central maximal diameter 818.532 µm ( n =264). Their tyles, if present, are spherical, terminally located and measure 814.524 µm in diameter ( n =228). Small spicules are usually straight or rarely slightly curved, stout and fusiform tylostyles with spherical, welldeveloped, terminally located tyles (fig. 5C). About 11% of these are subtylostyles and nearly 3% are styles. Altogether they measure: length 60383988 ìm, tyle diameter 29.422 µm, diameter of the shaft underneath the tyle 15.819 µm, maximal diameter of the shaft 29.430 µm ( n =860). Extralong spicules vary from styles to tylostyles (figs. 5D, E). They are straight, very slender and sharply pointed. Their dimensions are: length 22002753 4771 µm, proximal diameter 211.824 µm, central maximal diameter 524.641 µm ( n =135). The tyles of the extralong spicules, if present, may be spherical or oval, terminally located and measure 414.526 µm in diameter ( n =111). Sceptrelike spicules are considerably stout and either nearly isodiametric or its diameter increases from the proximal to the distal end, the former bearing a tyle and the latter being rounded (fig. 5F). The spherical tyles may be well or weakly developed, terminally located or slightly displaced. Sceptrelike spicules measure: length 1454821080 µm, tyle diameter 30 47.094 µm, proximal diameter 2342.391 µm, central diameter 2759.097 µm, distal diameter 2560.0103 µm ( n =8). Type locality : Antarctic : Southern Ross Sea: near Winter Quarters, 18–55 m and off Erebus volcano, 910 m . Distribution: Antarctic nearcontinent sectors ( Koltun 1964 ; Sarà et al. 1992 ): NN 2–5 including the Western Ross Sea and NN 8–9 including the Weddell Sea (present study as well) and the South Shetland Islands . Depth: 18–1080 m ( Koltun 1964 ); ca. 1050–4800 m in the Northern Weddell Sea (present study). FIGURE 4. Polymastia invaginata : external morphology and skeleton architecture. A–specimen SMF 10543. B–a specimen from series SMF 10546. C–a specimen from series SMF 10554. D–histological section of SMF 10543, general view. E–histological section of SMF 10546, general view. F–histological section of SMF 10548, detail of choanosome with stellate bundles of small spicules. G–histological section of SMF 10547, detail of cortex. H–histological section of SMF 10543, detail of cortex with a sceptrelike spicule. Scale bars: A–C 10 mm; D–E 1 mm; F–H 0.1 mm. FIGURE 5. Polymastia invaginata : spicules. A–frequency distribution of length (sceptrelike spicules excluded). B–principal spicules. C–small spicules. D–extralong spicule, general view. E–the same as D, details of proximal and distal ends. F–sceptrelike spicules. Scale bars: B–C 0.1mm; D 1 mm; E–F 0.1 mm. SW Atlantic: South Georgia and South Orkney Islands ( Koltun 1964 ; Sarà et al. 1992 ); South Sandwich Islands , ca. 750–2300 (present study). SE Pacific: Magellan area of Chile ( Desqueyroux & Moyano 1987 ). Southern Indian Ocean: Kerguelen, 245–346 m and Heard , 750 m (BouryEsnault & van Beveren 1982 ). TABLE 2. Polymastia invaginata : Results of spicule measurements. Measurements are given in µm. Each measurement is given as minimummeanmaximum. Upper row represents length. Middle row represents tyle diameter / diameter of the shaft underneath the tyle. Lower row represents maximal diameter of the shaft and the number of measured spicules (in brackets).

Specimen no. Small spicules	Principal spicules	Extralong spicules
SMF 10540 60218445	114013261634	No extralong spicules were observed
311.221 / 27.713	1011.716 / 810.113
212.522 ( n= 46)	161922 ( n= 17)
SMF 10541 180433720	148219432090	220423442508
48.613 / 56.710	813.616 / 610.613	1315.517 / 1112.914
59.818 ( n= 41)	1018.421 ( n= 7)	1821.927 ( n= 13)
SMF 10542 240397650 (specimen 1) 89.613 / 24.48	114014511710 813.316 / 69.211	No extralong spicules were observed
47.511 ( n= 83)	1116.719 ( n= 40)
SMF 10543 155403780	152018702090	224224022622
59.316 / 25.311	1417.521 / 1011.818	1618.924 / 1012.216
39.218 ( n= 44)	1825.630 ( n= 10)	2630.638 ( n= 10)
SMF 10544 165281950	110214952166	235623562356
510.113 / 25.610	913.518 / 59.913	1817.618 / 1312.813
48.818 ( n= 41)	817.622 ( n= 18)	161616 ( n= 1)
SMF 10545 135417929	128617072129	228630114771
58.816 / 35.611	1415.518 / 912.816	1518.526 / 141724
49.316 ( n= 60)	1924.330 ( n= 2)	2733.341 ( n= 29)

SMF 10546 429575943 10291579 2086 No extralong spicules were observed (specimen 1) 1113.115 / 57.411 1216.924 / 810.714 1113.916 ( n= 24) 1419.427 ( n= 36) SMF 10547 140429988 10261259 2052 24702786 3724 39.517 / 25.413 1113.719 / 68.413 56.816 / 24.211 39.618 ( n= 59) 1316.228 ( n= 8) 511.730 ( n= 13) SMF 10548 135374943 10291505 2186 22002791 3400 37.316 / 16.315 913.119 / 812.218 1517.119 / 1416.319 38.627 ( n= 60) 1621.332 ( n= 40) 2734.941 ( n= 20) SMF 10549 105244450 No principal spicules were 23182970 3534 observed 57.713 / 24.28 45.36 / 34.56 57.316 ( n= 47) 810.311 ( n= 20)

SMF 10550 100323988	102614622014	No extralong spicules were observed
26.813 / 2512	811.914 / 610.113
36.713 ( n= 45)	1318.224 ( n= 17)
SMF 10552 150375880	144418582166	220426253610
48.918 / 25.113	813.316 / 58.711	815.921 / 511.214
38.419 ( n= 125)	814.624 ( n= 9)	823.734 ( n= 29)
SMF 10553 160482790 (specimen 1) 68.713 / 35.48	129216362014 1014.519 / 71116	No extralong spicules were observed
68.813 ( n= 43)	1115.319 ( n= 20)

..... continued SMF 10556 111345914 No principal spicules were No extralong spicules were observed TABLE 2 (continued)

Specimen no. Small spicules	Principal spicules	Extralong spicules
SMF 10554 145318530 (specimen 1) 4710 / 34.56	133016972090 1014.218 / 810.713	No extralong spicules were observed
67.111 ( n= 41)	131822 ( n= 20)
SMF 10555 360608850	155817672014	No extralong spicules were observed
811.614 / 35.88	1317.521 / 1010.814
61216 ( n= 42)	1418.422 ( n= 20)

512.822 / 39.719 observed 51530 ( n= 59) Remarks The external and spicule morphology of P. i n v a g i n a t a varies greatly, that caused some discrepancy between the descriptions of different authors (table 3). Kirkpatrick (1907) noticed a sole exhalant papilla, completely invaginated in the thick surface hispidation, and a basal fleshy pad (the latter structure having never been mentioned by the following authors). A year later ( Kirkpatrick 1908 ) a sponge with two papillae was discovered. Kirkpatrick recognized two categories of spicules – principal styles, or strongyloxeas, of the main tracts, and small tylostyles including the slenderer ones of the stellate bundles in the choanosome and the fusiform ones making up the cortical palisade. In 1914 Hentschel established a new variety, P. invaginata var. gaussi , which he distinguished from Kirkpatrick’s sponges by the principal spicules being subtylostyles of smaller size. Koltun (1964) emphasized that the principal spicules could vary greatly in shape from styles to subtylostyles and in size. Both Hentschel (1914) and Koltun (1964) found no differences in shape between the choanosomal and cortical small tylostyles, though Koltun pointed out that the latter could be slightly larger. All authors mentioned above dealt with Antarctic sponges. Meanwhile BouryEsnault and van Beveren (1982) , who studied the material from the Southern Indian Ocean (Kerguelen and Heard ), described the specimens with papillae being only partially sunk in the surface hispidation. These authors recognized three spicule categories – principal tylostyles of the main tracts being considerably smaller than those described by the previous authors, small tylostyles of the choanosomal stellate groups and the cortical palisade, and long, sharply pointed tylostyles reinforcing the cortical bouquets of principal spicules and making up the surface hispidation. The latter echinating tylostyles of BouryEsnault and van Beveren had dimensions similar to those of the principal spicules described by the previous authors. The sponges examined by us share most of the morphological features with P. invaginata described by other authors. The presence of up to four papillae in a few ANDEEP specimens is not surprising if keeping in mind the note of Kirkpatrick (1908) . The minor invagination of papillae and the sufficient variety of principal spicules from tylostyles to styles might be also expected. In the meantime we observed the cortex reinforced by sharply pointed monactins morphologically similar to those described by BouryEsnault and van Beveren (1982) , but on average twice as long as any spicules previously registered in P. i n v a g i n a t a . The other feature distinguishing some of our sponges is the presence of cortical sceptrelike spicules. Principal spicules of our sponges fit well the dimension range given by Kirkpatrick (1907 , 1908 ), Hentschel (1914) and Koltun (1964) . Small spicules are also similar to the previous descriptions though their length maximum is relatively higher. This may be explained either by the insufficiently distinct discrimination between small and principal spicules or by the existence of intermediary size category being hidden because of insufficient sample size. We were unable to ascertain if there was any difference between the choanosomal and cortical small spicules. TABLE 3. Polymastia invaginata : comparison of characters given by different authors. All dimensions are given in µm as either a mean value or minimummaximum or minimummeanmaximum. In spicule dimensions the upper row represents length; the lower row represents central diameter of the shaft.

Characters	Kirkpatrick, 1907; 1908	Hentschel, 1914	Koltun, 1964	Boury–Esnault & van Beveren, 1982	Present study
Number of papillae	12	1	1	1	14
Invagination of papillae	Complete	Partial	Complete	Partial	Partial or none
Basal fleshy pad	Recorded	Not recorded	Not recorded	Not recorded	Not recorded
Spicules of choanosomal tracts	Slightly curved styles or strongyloxeas 2240 40	Slender, fusiform subtylostyles 8161792 1520	Styles or subtylostyles 8162240 1540	Fusiform tylostyles 227590890 1022.132	Fusiform, straight styles (subtylostyles, tylostyles) 102615682186 818.532
Spicules of choanosomal stellate bundles	Slender, slightly curved tylostyles 200 15	Stout, fusiform tylostyles 120600 1025	Fusiform tylostyles 70600 625	Fusiform tylostyles 71166312 56.59	Fusiform, straight or slightly curved tylostyles (subtylostyles, styles) 60383988 29.430
Thickness of cortex	5001250	400	400	1500	6001560
Spicules of cortical palisade	Fusiform, straight tylostyles 140350 1219	Stout, fusiform tylostyles 120600 1025	Fusiform tylostyles 70600 625	Fusiform tylostyles 71166312 56.59	1) Fusiform, straight or slightly curved tylostyles (subtylostyles, styles) 60383988 29.430 2) Infrequent scepterlike spicules 1454821080 2759.097
Spicules forming surface hispidation	Bouquets of choanosomal tracts	Bouquets of choanosomal tracts	Bouquets of choanosomal tracts	Bouquets of choanosomal tracts reinforced by slender, slightly curved, sharply pointed tylostyles 9231697.32106 1323.932	Bouquets of choanosomal tracts reinforced by slender, straight, sharply pointed tylostyles or styles 220027534771 524.641
Spicules of basal skeleton	Irregularly located spicules of various size	Not recorded	Not recorded	Not recorded	Not recorded

The considerable polymorphism of P. invaginata described above may be due to the environmental distinctions between different localities, e.g., between the Antarctic and Southern Indian Ocean. Nevertheless the existence of a species complex also cannot be excluded. In any case, all described specimens of P. invaginata share the possession of a single or at least very few exhalant papillae, a densely hispid surface and a single spicule layer in the cortex. P. hispidissima Koltun, 1966 from the NW Pacific and P. villosa DesqueyrouxFaúndez & van Soest, 1997 from the SE Pacific are also characterized by the single papilla and the thick surface hispidation formed by extralong spicules. However, these two species differ from P. invaginata by two spicule layers in the cortex. Meanwhile, a singlelayered cortex is shared by P. kurilensis Koltun, 1962 from the NW Pacific and P. atlanticus Samaai & Gibbons, 2005 from the SE Atlantic. The latter species also possesses the choanosomal clews of small spicules similar to the stellate bundles of P. i n v a g i n a t a . But other features of both P. atlanticus and P. kurilensis , including smooth surface, numerous wartlike papillae as well as spicule shape and size, distinguish them considerably from P. invaginata . Polymastia zitteli ( Lendenfeld, 1888 ) ( Fig. 6 ) Synonymy Sideroderma zitteli — Lendenfeld 1888 : 211 . Polymastia zitteli— Hallmann 1914 : 400 –402, pl. XV (fig. 6). Material examined SMF 10557 ( 1 specimen ): PS61/1323. Description External morphology. Sponge is cushionshaped, removed from substrate (fig. 6A). It measures approximately 33x27 x 5 mm . Surface is macroscopically smooth, grey coloured. The cortex is firm, transparent and easily detachable (fig. 6E). It is perforated by numerous small ostia which are not visible by a naked eye. There are several exhalant papillae of conical or tubular shape measuring 2–7 mm in length and 2–4 mm in diameter. The colour of papillae does not differ from that of the surface. Oscula measuring 0.5 mm in diameter are opened at the papillae summits. The choanosome is grey and rather friable. Skeleton. The main choanosomal skeleton represents a very loose reticulation formed by the tracts of principal spicules, which branch and anastomose (fig. 6B). Freely scattered intermediary spicules make up the additional choanosomal skeleton. The cortex, measuring 250–540 µm in thickness, consists of two layers (figs. 6C, D). The external palisade is made of the bouquets of small spicules. Its internal area is overlapped by the layer of intermediary spicules regularly arranged tangentially to the surface. Spicules. Three size categories of spicules are well distinguished. Thirty spicules of each category were measured. Principal and intermediary spicules are usually straight and fusiform styles, rarely strongyloxeas or subtylostyles (fig. 6F). Principal spicules measure: length 8129081315 µm, proximal diameter 67.510 µm, central maximal diameter 1316.021 µm. Intermediary spicules measure: length 340395598 µm, proximal diameter 68.310 µm, central maximal diameter 89.111 µm. Small spicules are subtylostyles with slightly subterminal tyles which are only feebly developed (fig. 6G). These subtylostyles are very slender, often slightly curved and measure: length 247287333 µm, proximal diameter 22.84 µm, central maximal diameter 34.04 µm. Type locality: SW Pacific: Eastern Australian Coast: Port Jackson, depth unknown. Distribution (other than type locality): Antarctic : NW Weddell Sea, ca. 2080 m (present data). FIGURE 6. Polymastia zitteli . A–specimen SMF 10557. B–histological section of idem, general view. C, D–the same as B, details of cortex. E–surface view of detached cortex of idem. F–principal and intermediary spicules. G–small spicules. Scale bars: A 10 mm; B 1 mm; C–E 0.2 mm; F–G 0.1 mm. Remarks. This is the second finding of P. zitteli since Lendenfeld (1888) described it from Eastern Australia . Our sponge fits well the original description as well as the redescription by Hallmann (1914) . The latter author clarified the misinterpretations made by Lendenfeld, namely so called trichites, making the cortical palisade, which were in fact very slender subtylostyles, chelae scattered within the palisade, which were evidently foreign, and oxeas found in the choanosomal tracts and in the internal cortical layer, which were obviously extremely fusiform styles or strongyloxeas. P. zitteli shares the reticulated choanosomal skeleton with two shallowwater species, P. boletiformis (Lamarck, 1813) from the North Atlantic and P. croceus Kelly Borges & Bergquist, 1997 from New Zealand . P. croceus and P. zitteli also share three spicule categories, which are typical of most other Polymastia spp., and the small cortical subtylostyles with faintlydeveloped tyles, which distinguish these species from other congeners. Conversely, P. boletiformis is distinguished by the absence of the intermediary spicule category, but its cortical tylostyles possess welldeveloped tyles, which are quite typical of the genus.