Stephanollona aff. contracta ( Waters, 1899 )

Ramalho, Laís V., Moraes, Fernando C., Salgado, Leonardo T., Bastos, Alex C. & Moura, Rodrigo L., 2021, Bryozoa from the reefs off the Amazon River mouth: checklist, thirteen new species, and notes on their ecology and distribution, Zootaxa 4950 (1), pp. 1-45 : 22-23

Stephanollona aff. contracta ( Waters, 1899)

( Fig. 11A–C )

Lepralia contracta Waters, 1899: p. 11 , pl. 3, figs 4–6.

Cleidochasma contractum: Cook 1964: p. 14 , fig. 5A; Arístegui 1984: p. 301, fig. 63d, e, pl. 21, figs 3, 4.

Stephanollona contracta: Souto et al. 2010: p. 1434 , fig. 15.

Material examined. MNRJBRY-1515: Brazil, Amapá state (Sta #3, 03°35.4267’N – 049°07.6028’W), 90 m, on sponge, 26 September 2014, collected by Fernando Moraes & Rodrigo Moura (NHo Cruzeiro do Sul ).

Description. Colony encrusting, multiserial, uni- to multilaminar ( Fig. 11A ).Autozooids polygonal, longer than wide [L 377–458–518 (SD 44, N 14); W 338–416– 486 µm (SD 35, N 20)]; frontal shield tubercular, imperforate except for about six rounded [11–19– 31 µm diameter (SD 6, N 27)] marginal areolar pores ( Fig. 11A, C ). Orifice cleithridiate, longer than wide [L 114–128–137 (SD 5, N 20); W 92–102– 110 µm (SD 5, N 22)]; poster denticulate with 15–20 small beads; shallow, broad sinus, almost rectangular; two prominent condyles facing downwards ( Fig. 11B, C ); six hollow distal spines [12–22– 30 µm diameter (SD 4, N 26)] in non-ovicellate zooids and four visible in ovicellate zooids ( Fig. 11B, C ). Two types of avicularia: (1) single or paired, small [L 87–99– 113 µm (SD 8, N 24)] and rounded avicularia laterally oriented, placed laterally to orifice; sometimes located more proximally to the orifice or near the proximal zooidal edge; rostrum serrated, raised from the frontal surface; crossbar complete with a strong columella ( Fig. 11A, C ); (2) single, large and elongate avicularium [L 265–331– 379 µm (SD 59, N 3)], placed lateral to orifice and distally oriented; rostrum with almost parallel sides and rounded tip; crossbar complete, with elongate, thick columella ( Fig. 11B ). Ovicell hyperstomial [L 146–169–179 (SD 13, N 9); W 172–184– 197 µm (SD 8, N 12)], occupying the proximal region of the next distal zooid; ooecial surface smooth, frontal area with a rounded triangular membranous window ( Fig. 11A, C ).

Remarks. Stephanollona contracta is a species complex with wide morphological variability, mainly in the number of spines (4–8) and colony appearance, which vary depending on colony age and avicularia development ( Cook 1964). The material examined herein shows similarities with specimens of S. contracta described from Algarve, Madeira, Havana and Africa ( Souto et al. 2010), including the orifice with broad and shallow sinus and beaded anter, ovicell with large uncalcified frontal area, and elongate and rounded avicularia. However, specimen MNRJBRY-1515 differs from those of other Atlantic localities in having always six spines, shorter avicularia with smaller columella, and in the lack of a suboral umbo. Despite such differences, owing to the high intraspecific variability observed for this species, specimens from Northern Brazil are provisionally identified as S. aff. contracta , pending molecular analysis essential to disentangle the species complex.

Winston (2005) synonymized Perigastrella contracta , described by Marcus (1937) from São Paulo state, with Stephanollona asper ( Canu & Bassler, 1923) , described from the Caribbean. Nevertheless, the Brazilian specimens studied by Marcus need to be reassessed, because they differ from the type material of S. asper in having a broader sinus, up to seven oral spines, and circular avicularia occupying most of the frontal surface and also can be interzooidal. Marcus’ material differs from Stephanollona aff. contracta in having adventitious circular avicularia without serrated rostra, sometimes interzooidal avicularia, and ovicells with umbones, while Stephanollona asper from the Caribbean differs in having smaller orifice (L 90–110–140, W 72–90– 108 µm), deep U-shaped sinus (shallow, broad, and almost rectangular in Stephanollona aff. contracta ), inner rim of orifice with large beads that extend until the condyles, and small avicularia with rough edges (but not serrated; see Winston 2005).

Three other Stephanollona species have been recorded from Brazil: S. angusta Vieira et al., 2010b , S. arborescens Vieira et al., 2010b , and S. robustaspinosa Ramalho et al., 2011 , all with six oral spines and differing from each other mainly in the shape of the orificial sinus. Stephanollona angusta has a narrow U-shaped sinus, in addition to a pair of elongate avicularia with narrower rostrum; S. arborescens has erect colonies and U-shaped narrower sinus; and S. robustaspinosa has longer sinus, spear-shaped elongate avicularia, and ovicell with an almost quadrate membranous frontal area. Stephanollona propinqua Winston & Woollacott, 2009 is also similar to S. aff. contracta in having a rounded avicularium in the same position, but it has a wider and shallower sinus, up to eight spines and elongate avicularia scattered over the colony surface, not lateral to the orifice. Finally, S. boreopacifica Yang et al., 2018b from Korea, also has six oral spines, similar elongate avicularia with well-developed ligula, and small rounded avicularia with serrated rostrum, but differs in having a narrower U-shaped sinus and avicularia associated with the ovicell.

Figures

FIGURE 11. A–C. Stephanollona aff. contracta (Waters, 1899) (MNRJBRY-1515). A. General view of the colony. B. Distal part of a zooid with elongate, latero-oral avicularium and orifice with six spines and a shallow, broad, almost rectangular sinus. C. Zooids bearing rounded avicularia with serrated rostrum and ovicell with a frontal, uncalcified area. D, E. Stephanollona domuspusilla Ramalho & Moraes n. sp. (Holotype MNRJBRY-1543). D. Colony showing irregular growth pattern. E. Autozooids showing distal lanceolate and spear-shaped oral spines, and one zooid with a broader and shallow sinus. Scale bars: A, 500 µm; B, C, 100 µm; D, E, 200 µm.