Schizomavella linearis ( Hassall, 1841 )

Reverter-Gil, Oscar, Souto, Javier, Novosel, Maja & Tilbrook, Kevin J., 2015, Adriatic species of Schizomavella (Bryozoa: Cheilostomata), Journal of Natural History 50, pp. 281-321 : 303-307

Schizomavella linearis ( Hassall, 1841)

( Figure 11 ; Tables 8 – 10 )

Lepralia linearis Hassall, 1841: 368 , pl. 9, fig. 8.

Schizoporella linearis: Hincks 1880: 247 , pl. 38, figs 5 – 9.

Schizomavella linearis: Canu and Bassler 1928: 30 , pl. 3, figs 1 – 6; Gautier 1962: 140; Hayward and Thorpe 1995: 671, pl. 4; Reverter-Gil and Fernández-Pulpeiro 1996: 271, figs 2, 3G; Hayward and Ryland 1999: 282, figs 127, 128; Hayward and McKinney 2002: 59, fig. 26E – G; Novosel 2007: 64, fig. 27E, F.

Schizomavella hastiformis Hayward and Ryland 1978: 152 , figs C, D.

Schizomavella hastata: Novosel 2007: 64 , fig. 28A, D.

Material examined

Morphotype ‘typical’:

CNHM Inv. br. 62: St. 8, Jabuka Shoal (PJ-2), 43°06.060 N, 15°26.210 E, 28 August 2001, 32 m.

CNHM Inv. br. 63: St. 11, Biševo, 42°57.312 N, 16°00.261 E, 14 February 2006, 10 – 20 m.

MNCN 25.03 /3910: St. 7, Kornati (Mana), 43°47.922 N, 15°16.452 E, 10 July 2003, 10 – 20 m ( Figure 11A, B ) .

Morphotype ‘hastiformis’:

CNHM Inv. br. 64: St. 3, Silba, 44°32.894 N, 14°69.794 E.

CNHM Inv. br. 65: St. 4, Dugi otok (North), 44°10.225 N, 14°48.307 E, 11 October 2004, 5 – 12 m.

CNHM Inv. br. 66: St. 14, Hvar Island (Kozja), 43°11.374 N, 17°04.930 E, 2 April 2005, 15 – 20 m.

3914: St. 16,/3911: St. 12, Vis (Komiža Bay), 43°04.430 N, 16°07.213 E, 1 September 2001, 10 – 15 m ( Figure 11C, E ) .

3914: St. 16,/3912: St. 14, Hvar Island (Kozja), 43°11.374 N, 17°04.930 E, 2 April 2005, 15 – 20 m.

3914: St. 16,/3913: St. 14, Hvar Island (Kozja), 43°11.374 N, 17°04.930 E, 2 April 2005, 15 – 20 m ( Figure 11D ) .

3914: St. 16,/3914: St. 16, Korčula Island (Lucnjak), 42°94.973 N, 17°16.026 E, 2007, 15 – 20 m.

Morphotype ‘pseudolinearis’:

CNHM Inv. br. 67: St. 2, Ćutin Islet (Cres), 44°72.393 N, 14°49.374 E, 17 October 2001, 12 m.

CNHM Inv. br. 68: St. 6, Dugi otok Vele stijene, 43°54.282 N, 15°07.954 E, 12 July 2003, 20 – 40 m.

MNCN 25.03 /3915: St. 1, Ždralova Bay (Velebit Channel), 44°53.059 N, 14°53.458 E, 27 May 2002, 10 – 20 m.

MNCN 25.03 /3916: St. 7, Kornati (Mala Sestrica), 43°47.922 N, 15°16.452 E, 30 – 35 m ( Figure 11F ) .

Remarks

Schizomavella linearis was redescribed by Hayward and Thorpe (1995), who selected a neotype. Its supposed distribution ranges from west Norway and Faroe Isles in the north to the western Mediterranean, and into the Adriatic, in the south.

Having examined several specimens from different sampling sites, we have noted some morphological variations within them, and as a result we have outlined these variations in the three ‘ forms ’ noted below.

Material coming from Sts. 7, 8 and 11 ( Figure 11 A, B ) fits the redescription of S. linearis by Hayward and Thorpe (1995) (see also Hayward and Ryland 1999; Hayward and McKinney 2002), and is here named the ‘typical’ morphotype.

Material coming from Sts. 3, 4, 12, 14, and 16 develops a single suboral avicularium on a large, conical umbo proximal to the sinus, and is here named the ‘hastiformis’ morphotype. The extent of this umbo, actually the avicularian cystid, varies in morphology from a low, massive cone, to a long, finger-like projection ( Figure 11C – E ). The material cited here was previously reported as S. hastata by Novosel (2007). The true identity of S. hastata was uncertain until its redescription by Hayward and Thorpe (1995). Earlier authors (and even some later ones) based their identifications on the presence of the single, suboral avicularium on a large umbo; however, the character that best defines S. hastata is the shape of the orifice, it being rounded, with a broad, shallow sinus occupying its entire proximal border, and flanked by very small condyles. On the contrary, the material here studied has a primary orifice quite similar to the typical material of S. linearis , so we think that it does not correspond to S. hastata . A similar morphology can be also seen in material identified as S. hastata from La Atunara (Strait of Gibraltar; López de la Cuadra 1991: pl. 26, fig. F), Marseille (photos sent by J.G. Harmelin), Algeria (MNHN 11239, Gautier Coll.) and the Balearics (MNHN 11222, Gautier Coll.). The discovery of specimens from the north of the Bay of Biscay with a single suboral avicularium led Hayward and Ryland (1978) to describe the species Schizomavella hastiformis , which nevertheless they later considered to be a morphotype of S. linearis (see Hayward and Ryland 1999). Something similar may occur with Mediterranean material previously identified as S. hastata .

Finally, material coming from Sts 1, 2, 6 and 7, here named the ‘pseudolinearis’ morphotype, has a larger primary orifice that is longer than wide, and the avicularia are larger than in the typical form of the species, and frequently distally orientated, instead of medially ( Figure 11F ). Similar colonies have been observed off Avilés (northwest Spain) at 144 m depth, and off Brittany at 255 m depth (unpublished data). We are unable to discount the possibility that these differences are within the range of variation of the species, and we therefore tentatively include these specimens in S. linearis .

These three ‘ morphotypes ’ do not seem to follow any pattern of distribution along the Adriatic coast, and no particular abiotic pattern was observed that can explain the morphological variations. Taking into account the high degree of variation observed in material of S. linearis , not only in the Adriatic but also in the western Mediterranean, we believe that it is not impossible that we were dealing with several similar species. To corroborate this assumption, however, it will be necessary to undertake a thorough revision of Atlanto – Mediterranean specimens previously identified as S. linearis or any of its ‘ varieties ’, as well as S. hastata , using SEM observations, as well as utilising newly collected material for molecular work, and previous literature. This huge task is outside the scope of the present paper.

Figures

Figure 11. Schizomavella linearis. (A, B) Typical morphotype (MNCN 25.03/3910, St. 7, Kornati); (C–E) morphotype with a large single suboral avicularium (C and E, MNCN 25.03/3910, St. 12, Vis, Komiža Bay; D, MNCN 25.03/3913, St. 14, Hvar Island); (F) morphotype with larger primary orifice and avicularia (MNCN 25.03/3916, St. 7, Kornati).