Rhynchozoon turgidum, Almeida & Larré & Vieira, 2021

Almeida, Ana C. S., Larré, Igor R. N. M. & Vieira, Leandro M., 2021, Ten new species of marine bryozoans (Gymnolaemata: Cheilostomatida) from Brazil, Zootaxa 5048 (4), pp. 511-537 : 521-523

Rhynchozoon turgidum n. sp.

( Fig. 6A–F )

urn:lsid:zoobank.org:act:2207207E-9591-425B-A9FB-CA93EB8B24FD

Material examined. Holotype: UFBA 2238.12 , 12º45’ S, 38º06’ W, Camaçari, Costa dos Coqueiros, Bahia, Brazil, 22 m, coll. by LAMEB-UFBA, 2006 . Paratypes: UFBA 3028.1 , 12º44’ S, 38º04’ W, Camaçari, Costa dos Coqueiros, Bahia, Brazil, 28 m, coll. by LAMEB-UFBA, 2002 ; UFBA 3541.1 , 12º44’ S, 38º06’ W, Camaçari, Costa dos Coqueiros, Bahia, Brazil, 22 m, coll. by LAMEB-UFBA, 2008 ; UFPE 913 , 4 º49’– 5º10’ S, 36º10’– 36º50’ W, Bacia Potiguar, Rio Grande do Norte, Brazil, coll. by Petrobras, 2009–2010 . Additional specimens: UFBA 3776.2 , 12º46’ S, 38º05’ W, Camaçari, Costa dos Coqueiros, Bahia, Brazil, 27 m, coll. by LAMEB-UFBA, 2002 ; UFBA 3719.3 , 12º46’ S, 38º07’ W, Camaçari, Costa dos Coqueiros, Bahia, Brazil, 26 m, coll. by LAMEB-UFBA, 2002 .

Diagnosis. Rhynchozoon with tuberculate autozooids, large primary orifice with shallow U-shaped sinus and rectangular condyles, suboral avicularia with subtriangular rostrum and uncinate process, no oral spines, frontal shield sometimes with single rhombic frontal avicularium, and immersed ovicells with frontal tabula.

Type locality. Camaçari , Bahia, Brazil .

Etymology. Latin turgidus , swollen, alluding to the swollen tubercles on zooidal frontal shield and peristome of this species.

Description. Colony encrusting, uni- to multilaminar ( Fig. 6A ).

Zooids at the growing edge subrectangular, separated by furrows in which there are slightly raised boundary lines. Primary orifice often rounded by short and rounded marginal peristomial tubercles, and with a subtriangular suboral avicularium directed distolaterally, with complete crossbar ( Fig. 6B ). In later astogeny the autozooidal frontal shield thickens and the secondary orifice develops 3–6 large tubercles, obscuring the primary orifice and eventually the suboral avicularium ( Fig. 6C ). Autozooids becoming irregularly polygonal further from margin (0.271–0.320– 0.421 mm long, n = 15, SD = 0.053 mm; 0.237–0.304– 0.345 mm wide, n = 15, SD = 0.038 mm). Frontal shield smooth textured, with irregularly rounded to pointed tubercles mainly placed near the marginal areolar-septular pores, occasionally merged in larger tubercles; marginal pores 10–12, large. Primary orifice small relative to frontal shield, transversely elliptical (0.076–0.094– 0.109 mm long, n = 15, SD = 0.010 mm; 0.097–0.106– 0.127 mm wide, n = 15, SD = 0.009 mm), distal margin semicircular, beaded with 16–20 rounded denticles, a pair of subrectangular condyles at proximal corners and proximal broad, shallow, U-shaped sinus ( Fig. 6D ).

Suboral avicularia with subtriangular rostrum (0.107–0.110– 0.137 mm long, n = 15, SD = 0.010 mm; 0.028– 0.039– 0.047 mm wide, n = 15, SD = 0.006 mm), positioned slightly lateral to the proximal orificial border, directed obliquely distalwards; crossbar complete; uncinate process projected into the secondary orifice, sometimes occluded by oral tubercles ( Fig. 6B ). Frontal avicularia (0.089–0.111– 0.129 mm long, n = 15, SD = 0.011 mm; 0.040–0.051– 0.058 mm wide, n = 15, SD = 0.005 mm) may occur in some zooids (but often absent in young zooids), placed near zooidal margins; rhombic, small, with complete crossbar, rostrum elongate-triangular ( Fig. 6A, E ).

Ovicells (0.191–0.228– 0.254 mm long, n = 10, SD = 0.021 mm; 0.251–0.277– 0.325 mm wide, n = 10, SD = 0.026 mm) prominent in young zooids, becoming immersed with increasing calcification; ooecia subglobular and frontally flat, endooecium completely calcified, ectooecium frontally uncalcified, with semicircular tabula, completely bordered by endooecium along the proximal margin; ooecia often covered by tubercular secondary calcification of the frontal shields of surrounding zooids along the lateral and distal margins ( Fig. 6F ).

Remarks. Like its congeners Rhynchozoon brasiliensis Almeida,Souza,Menegola&Vieira,2017 and Rhynchozoon incrassatum ( Hincks, 1882) , R. turgidum n. sp. is characterized by autozooids with numerous frontal tubercles, a primary orifice with distinct sinus, suboral and frontal avicularia with similar size and morphology, an ovicell becoming immersed with colonial development, and absence of oral spines and a large avicularium. Rhynchozoon turgidum n. sp. differs from R. brasiliensis , however, by having a larger primary orifice (0.097 –0.127 mm in R. turgidus n. sp.; 0.037 – 0.062 mm in R. brasiliensis ), with a U-shaped, shallow and broad sinus (V-shaped in R. brasiliensis ), rectangular condyles (triangular in R. brasiliensis ), and smaller (0.089 –0.129 mm long and 0.040 –0.058 mm wide in R. turgidus n. sp.; 0.124 –0.210 mm long and 0.175 –0.262 mm wide in R. brasiliensis ) and less numerous frontal avicularia (typically one in R. turgidus n. sp.; two or more per autozooid in R. brasiliensis ) ( Almeida et al. 2017). Rhynchozoon incrassatum is distinguished from R. turgidum n. sp. by having subhexagonal or oval autozooids (subrectangular or irregularly polygonal in R. turgidum n. sp.), a frontal shield with a rough surface (smooth in R. turgidum n. sp.), and frontal avicularium placed medially on the frontal shield (marginal in R. turgidum n. sp.) ( Hincks 1882).

Additionally, adult colonies of R. turgidum n. sp. have merged frontal tubercles, forming rounded ridges that obscures the orifice, avicularia and ovicells, a character that distinguishes R. turgidum n. sp. from all other congeners reported from Brazil — Rhynchozoon coalitum Vieira, Gordon, Souza & Haddad, 2010 ; Rhynchozoon itaparicaensis Almeida, Souza, Farias, Alves & Vieira, 2018 ; and Rhynchozoon phrynoglossum Marcus, 1937 (e.g., Almeida et al. 2017, 2018; Marcus 1937, 1955; Vieira et al. 2010).

Distribution. Western Atlantic: Brazil (Bahia and Rio Grande do Norte). Rhynchozoon turgidum n. sp. commonly encrusts red algae and calcareous nodules; 22‒ 28 m.

Figures

FIGURE 6. Rhynchozoon turgidum n. sp., UFBA 2238.12, holotype.A. Overview of an encrusting colony. B.Autozooids at the growing edge. C. Older autozooids. D. Detail of primary orifice. E. Group of ovicelled zooids. F. Detail of ovicells. Scale bars: A. 500 µm; B, C, F. 200 µm; D. 100 µm; E. 250 µm.