Reptadeonella costulata

Almeida, Ana C. S., Souza, Facelucia B. C., Sanner, Joann & Vieira, Leandro M., 2015, Taxonomy of recent Adeonidae (Bryozoa, Cheilostomata) from Brazil, with the description of four new species, Zootaxa 4013 (3), pp. 348-368 : 354-355

Reptadeonella costulata ( Canu & Bassler, 1928a)

( Figs 10–12 ; Table 1 )

Adeona costulata Canu & Bassler, 1928a: 37 , pl. 8, figs 7–8. [ Brazil: Rio de Janeiro] Reptadeonella costulata: Vieira et al. 2008: 24 . [ Brazil; checklist]

Material examined. Holotype: USNM 8570, Adeona costulata, F. Canu & R. Bassler det., Rio de Janeiro, Brazil, 128 m, coll. 1877 by Steamer Norseman.

Description. Colony encrusting, multiserial, unilaminar. Zooids more or less elongate-hexagonal to polygonal, longer than wide, delimited by slightly raised margins. Frontal shield heavily calcified, finely granular, marginally punctured by a single row of 22–34 areolar pores. Orifice approximately 16% of total length of frontal shield, mostly slightly elliptical or subcircular, a little wider than long; peristome low, bordered by distal areolar pores. An additional areolar pore, rarely paired, proximal to orifice adjacent to suboral avicularium. Avicularium elongate, more or less latero-oral, placed on frontal shield such that it is directed obliquely past one side of the orifice, the rostral tip almost level with its distal margin; rostrum elongate-triangular, tiny condyles placed one-third length, no opesial cryptocystal shelf. No other frontal avicularia. Spiramen narrower than an arerolar pore, transversely elliptical, placed at midlength of zooid. Gonozooids not recognized.

Remarks. Reptadeonella costulata can be distinguished from all congeners by the combination of characters—elongated autozooids with a single row of areolar pores, low peristome, and 1–2 smaller areolar pores adjacent to suboral avicularium that is directed obliquely past the orifice, and tiny elliptical spiramen. Reptadeonella costulata is distinguished from R. bipartita by the proportionally smaller additional areolar pore (larger in R. bipartita ), oblique suboral avicularium (straight in R. bipartita ) and elliptical spiramen (crescentic in R. bipartita ).

Since its original description, R. costulata has been reported from Jamaica and Belize ( Best & Winston 1984; Winston 2005), but the specimens figured by Best & Winston (1984) have a relatively large additional areolar pore (rather than a small elliptical pore as in the holotype), a hood-like peristome (low in the type specimen) and circular spiramen (transversely elliptical in the R. costulata holotype). Winston (2005) measured autozooids in R. costulata from the Caribbean as having a mean length of 0.85 mm and mean width of 0.50 mm), much larger than in the type specimen (mean length 0.57 mm, mean width 0.29 mm), and pointed out that the avicularia sometimes extend beyond the distal margin of the orifice, whereas those in the holotype are level with distal margin. We conclude that the Caribbean specimens of R. costulata (sensu Best & Winston 1984) may comprise a distinct species.

Distribution. Atlantic: Brazil (Rio de Janeiro); sublittoral.

Figures

FIGURES 10 – 12. Reptadeonella costulata, USNM 8570, holotype, Rio de Janeiro State, Brazil: 10, part of encrusting colony; 11, 12, autozooids showing avicularia, subperistomial areolar pores adjacent to avicularia and tiny transverse spiramina. Scale bars: 10 = 500 µm; 11 = 200 µm; 12 = 100 µm.