Arbocuspis bicornis ( Hincks, 1881 )

Vieira, Leandro M., Almeida, Ana C. S. & Winston, Judith E., 2016, Taxonomy of intertidal cheilostome Bryozoa of Maceió, northeastern Brazil. Part 1: Suborders Inovicellina, Malacostegina and Thalamoporellina, Zootaxa 4097 (1), pp. 59-83 : 73-74

Arbocuspis bicornis ( Hincks, 1881)

( Figs. 26–27 )

Membranipora bellula var. bicornis Hincks, 1881: 149 , pl. 8, fig. 4A. [ Ceylon (= Sri Lanka)] Electra bellula var. bicornis: Hastings, 1930: 706 (in part), pl. 2, fig. 8. [ Ceylon (= Sri Lanka)] Electra bellula: Marcus, 1937: 37 (in part), pl. 6, figs. 14C (not pl. 6, figs. 14A–B, D–F). [ Brazil: São Paulo] Electra bellula: Marcus, 1941: 16 (in part), fig. 6 (in part). [ Brazil: Paraná]

Electra bellula: Vieira et al., 2008: 12 (in part). [ Brazil: São Paulo and Paraná]

Material examined. Holotype: NHMUK 1899.5.1.691, Electra bellula var. bicornis, T. Hincks Collection, Ceylon ( Sri Lanka), on algae. Additional specimens: UFPE 0 42, Jacarecica, Maceió, Alagoas State, Brazil, 9º36'50" S, 35º41'12" W, intertidal, on algae, coll. February 2004. UFPE 0 46, UFPE 0 84, Riacho Doce, Maceió, Alagoas State, Brazil, 9º34'42" S, 35º39'19" W, intertidal, on algae, Sargassum spp., coll. 31 March 2007 by L.M. Vieira.

Description. Colony encrusting, uni- to multiserial, forming linear runners with parallel rows to mat-like colonies, calcified, and whitish. Zooids elongate, 0.229–0.383 mm (0.296 ± 0.033) long and 0.148–0.216 mm (0.175 ± 0.017) wide, with distal oval opesiar region covered by frontal membrane, about 0.136–0.173 mm (0.150 ± 0.010) long, and a slightly narrower calcified proximal region. Proximal gymnocyst extended, occupying half of the length of zooids, about 0.111–0.228 mm (0.145 ± 0.031) long, smooth. Frontal surface of gymnocyst convex, with an unbranched median spine placed on a slightly raised region in the midpoint of zooid, close to the proximal rim of the opesia, and two large branching spines, lateral to the median spine, arched over and above the frontal membrane. A pair of curving pointed spines occurs on either side of the operculum at the distal end of the opesia (but belongs to the distal zooids). Colonies develop from a single ancestrula.

Remarks. No differences were observed between Ceylon’s Electra bellula var. bicornis (NHMUK 1899.5.1.691) and the specimens from Alagoas herein assigned to A. bicornis . Arbocuspis bicornis is distinguished from A. bellula in having two branched spines overarching the frontal membrane. Specimens described by Hincks (1881) as Membranipora bellula var. multicornis (now Arbocuspis multicornis ) are distinguished from A. bellula and A. bicornis by the presence of three branched spines overarching and occupying most of the opesiar area.

Distribution. Arbocuspis bicornis is found on algae (red algae) in Brazil and Sri Lanka. This is the first record of this species in Alagoas.

Figures

FIGURES 24 – 27. Species of Arbocuspis from Maceió: 24 – 25, Arbocuspis bellula, Maceió, Alagoas Brazil; 24, group of zooids on algae; 25, close-up of three autozooids showing the frontal spines; 26 – 27, Arbocuspis bicornis, Maceió, Alagoas, Brazil; 26, group of zooids on red algae; 27, close-up of the autozooids showing the frontal spines.