Stephanollona robustaspinosa, Ramalho & Muricy & Taylor, 2011

Ramalho, Laís V., Muricy, Guilherme & Taylor, Paul D., 2011, Taxonomic revision of some lepraliomorph cheilostome bryozoans (Bryozoa: Lepraliomorpha) from Rio de Janeiro State, Brazil, Journal of Natural History 45 (13 - 14), pp. 767-798 : 790-792

Genus Stephanollona Duvergier, 1920

(= Brodiella Uttley and Bullivant, 1972 ; Paracleidochasma Soule et al., 1991 ) Stephanollona robustaspinosa sp. nov.

( Figure 10 )

Material examined

Holotype: MNRJ-178; Paratype: MNRJ-241, REVIZEE Station 2 (23 ◦ 47.629 ′ S, 041 ◦ 42.514 ′ W), collected by D.C. Savi from the naval ship Diadorim using a trap, 20 July 2004, depth 341 m. Stephanollona longispinosa : holotype: NHM 99.5.1.1086, Hincks Collection. NHM 1990.11.20.19, 25 March 1927, depth 79 m. NHM 1991.4.18.5–6, Discovery station WS84, depth 75 m. Stephanollona armata: NHM 1936.12.30.215, Providence , Thornely Collection, depth 228 m. NHM 1966.1.12.16, Kullana Point, Malta .

Etymology

The name robustaspinosa refers to the strong, thick spines.

Diagnosis

Colonies small, almost circular; frontal wall granular, with marginal areolar pores only; orificial sinus long, narrow; oral spines numbering six, either spear-shaped or tapering towards tips; ovicell imperforate, ectooecium with a broad, membranous frontal area, exposing the entooecium; a short, broad labellum present, defined by short lateral fissures; avicularia lateral to orifice dimorphic, one small, rounded with dented rostrum, the other setose, directed distally.

Description

Colony either small, roughly circular, semi-erect, generally with free borders, or larger, irregular in shape, closely encrusting substratum, up to 15 mm in diameter; translucent ( Figure 10A ).

Autozooids almost hexagonal, a little longer than wide (782 µm long, range 637–862 µm, by 729 µm wide, range 441–902 µm wide ( Figure 10B ). Frontal wall granular, slightly convex, pseudopores absent, areolar pores around margin rounded; zooids separated by slender salient walls ( Figure 10B,C ). Orifice circular, slight dilated proximally; sinus long, slightly wider in some zooids; condyles present; lyrula absent; denticles developed around distal and lateral edges of orifice ( Figure 10C ); oral spines numbering six, basally articulated, irregularly calcified, dilated and flattened at distal ends of some, followed by narrowing towards tip, resembling a spear; other spines resembling needles; sometimes all of the oral spines become very elongated ( Figure 10B–E ). Ovicell slightly wider than long (232 µm long, range 225–235 µm, by 219 µm wide, range 205–235 µm), imperforate, not closed by operculum ( Figure 10C ), frontally slightly flattened, sometimes covered only by the entooecium ( Figure 10B ); labellum wide with fissure ( Figure 10C ).

Avicularia oral, dimorphic, one on each side above proximal line of orifice ( Figure 10B–E ). Smaller avicularia measuring 98 µm long (range 88–108 µm) by 82 µm wide (range 78–88 µm); teeth well developed ( Figure 10B–D ). Large avicularia measuring 252 µm long (range 98–302 µm) by 101 µm wide (range 59–118 µm); mandible thin and elongated (265 µm long, range 157–294 µm), sometimes slightly bent at the tips, directed distally; rostrum with same shape as mandible ( Figure 10B,D,E ). The two types of avicularium seemingly occur randomly on autozooids: one small plus one large ( Figure 10B ), two small ( Figure 10C ), or two large ( Figure 10E ).

Habitat

Colonies found on rock substrata and tubes of polychaetes, 6–10 m deep.

Geographical distribution

REVIZEE Station 2 (23 ◦ 47.629 ′ S, 041 ◦ 42.514 ′ W), Rio de Janeiro State, Brazil .

Remarks

Two fossil species and a few Recent species distributed in the Atlantic and Pacific are known of this genus. Only one species has been recorded from Brazil: S. asper (Canu and Bassler, 1923) , which was mentioned by Marcus (1937: 98) as Perigastrella contracta (Waters, 1899) . Canu and Bassler’s species differs from S. robustaspinosa sp. nov. in having a shorter sinus, a large spatulate avicularium with rounded rostrum, small avicularia with rough rostra, unserrated, and in the position of the avicularia, shape of the distal spines, and colonies that may be multilamellar. The new species is more similar to S. longispinata (Busk, 1884) but differs mainly in having a median frontal avicularium. Other differences are the thinner oral spines, which are generally longer, large avicularium directed to the sides and / or distally, and the much narrower labellum.

The species S. orbicularis (Hincks, 1881) has a wider sinus with an avicularium just below it. Differences between S. robustaspinosa sp. nov., S. armata (Hincks, 1861) and S. ignota Hayward and Cook, 1983 are in avicularium shape and position, and oral spine number and shape. Although S. serrata (Osburn, 1912) has small avicularia with serrated rostra, this species differs from S. robustaspinosa sp. nov. in having a shorter and wider sinus, only four distal spines, and avicularia oriented in several directions.

Superfamily CONESCHARELLINOIDEA Levinsen, 1909

Figures

Figure 10. Stephanollona robustaspinosa sp. nov. (A) General view of the colony; (B) part of the colony showing arrangement and shape of autozooids, marginal pores, oral spines, ovicells and dimorphic avicularia; (C) detail of distal region of an autozooid with small avicularia spines and an ovicell; (D) dimorphic avicularia and oral spines of different shapes; (E) detail of distal region of an autozooid with elongate avicularia. Scale bars: A: 1 mm; B: 200 µm; C–E: 100 µm. MNRJ-178.