Plesiocleidochasma brasiliensis, 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 : 517-520

Plesiocleidochasma brasiliensis n. sp.

( Fig. 4A–F )

urn:lsid:zoobank.org:act:2B338FEE-BEDD-40BF-9D1E-78AA75727351

Cleidochasma porcellana: Machado & Souza 1994: p. 259 .

Plesiocleidochasma porcellanum: Almeida et al. 2015a: p. 5 .

Material examined. Holotype: UFBA 012.1 , 12º45’ S, 38º06’ W, Camaçari, Costa dos Coqueiros, Bahia, Brazil, 25 m, coll. by LAMEB-UFBA, 1995 . Paratypes: UFBA 1884.4 , 12 º44– 12º45’ S, 38º05’– 38º06’ W, Camaçari, Costa dos Coqueiros, Bahia, Brazil, 22–23 m, coll. by LAMEB-UFBA, 2007 ; UFBA 2885.1 , 13°07’ S, 38°38’ W, 13–21 m, Baía de Todos os Santos , Bahia, Brazil, coll. by Ricardo Miranda, 2017 ; UFPE 907 , 4 º49’– 5º10’ S, 36º10’– 36º50’ W, Bacia Potiguar, Rio Grande do Norte, Brazil, coll. by Petrobras, 2009–2010 . Additional specimens: UFBA 2005.1 , UFBA 2166.3 , UFBA 2168.3 , 12 º44– 12º45’ S, 38º05’– 38º06’ W, Camaçari, Costa dos Coqueiros, Bahia, Brazil, 22–23 m, coll. by LAMEB-UFBA, 2007 ; UFBA 2877.3 , UFBA 2878.3 , UFBA 2881.1 , 13°07’ S, 38°38’ W, 13–21 m, Baía de Todos os Santos , Bahia, Brazil, coll. by Ricardo Miranda, 2017 ; UFBA 1127.3 , 12°43’ S, 38°02’ W, Banco de Abrolhos , Costa das Baleias, Bahia, Brazil, 41 m, coll. by REVIZEE Score Central, 1996 ; UFBA 295 , 16º07’ S, 38º29’ W, Banco Royal Charlotte, Costa do Descobrimento , Bahia, Brazil, 35 m, coll. by REVIZEE Score Central, 1996 ; UFBA 3642 , UFBA 3644 , 05°03’ S, 36°19’ W, 50–53 m, Guamaré , Rio Grande do Norte, Brazil, coll. 2005 .

Diagnosis. Plesiocleidochasma with encrusting colonies of zooids with rugose and imperforate frontal shield except for 3–6 circular areolar-septular pores, keyhole-shaped primary orifice with broad proximal sinus, downcurved subtriangular condyles, 3–4 oral spines, orifice becoming surrounded by 3–6 rounded tubercles (3–4 around the orifice and 1–2 on the proximal margin of the distal zooid) with secondary calcification, single or paired small adventitious avicularia with acute rostrum and large subtriangular opesia.

Type locality. Camaçari , Bahia, Brazil .

Etymology. The specific epithet refers to the type locality of the species, Brazil.

Description. Colony encrusting, uni- to multilaminar ( Fig. 4A, E ).

Autozooids subhexagonal or irregularly polygonal (0.279–0.377– 0.491 mm long, n = 30, SD = 0.053 mm; 0.240– 0.327– 0.392 mm wide, n = 30, SD = 0.040 mm), often not well defined, but separated by shallow grooves and almost inconspicuous sutures ( Fig. 4B, E ). Frontal shield rugose, imperforate except for 3–6 circular areolar-septular pores. Primary orifice keyhole-shaped (0.090–0.123– 0.149 mm long, n = 30, SD = 0.013 mm; 0.085–0.104– 0.118 mm wide, n = 30, SD = 0.008 mm), distal margin semicircular, proximal margin with a broad U-shaped sinus ( Fig. 4C ), about 0.030–0.033– 0.035 mm long; 3–4 oral spines ( Fig. 4C ), becoming concealed by increasing calcification ( Fig. 4B ); a pair of subtriangular condyles hooked downwards ( Fig. 4C ). Multilaminar colonies often with peristome formed by 3–6 rounded tubercles, 3–4 around the orifice and 1–2 on the proximal margin of the distal zooid ( Fig. 4E, F ).

Adventitious avicularia single or paired (0.069–0.082–0.100 mm long, n = 30, SD = 0.007 mm; 0.037–0.050– 0.058 mm wide, n = 30, SD = 0.004 mm), placed laterally below the orifice, sometimes at same level as sinus; rostrum laterally directed, often slightly oblique to the distal zooidal corners at an angle of 45, drop-shaped (rounded proximal but with pointed distal end); cryptocyst forming distal rim, with almost incomplete palatal area resulting in a subtriangular to lanceolate foramen; complete crossbar with small, almost rounded columella; opesia narrowly semicircular ( Fig. 4C ).

Ovicell submerged (0.111–0.150– 0.201 mm long, n = 13, SD = 0.025 mm; 0.147–0.184– 0.228 mm wide, n = 13, SD = 0.021 mm); ooecium with same calcification as the frontal shield; labellum semicircular ( Fig. 4D ).

Remarks. Among the 16 living species of Plesiocleidochasma , P. brasiliensis n. sp. most resembles Plesiocleidochasma foliosum Winston, Vieira & Woollacott, 2014 , from Brazil, Plesiocleidochasma mediterraneum Chimenz Gusso & Soule, 2003 , from the Mediterranean Sea, Plesiocleidochasma porcellaniforme ( Soule, Soule & Chaney, 1991) , from the Indo-Pacific, and Plesiocleidochasma porcellanum ( Busk, 1860) , reported in different tropical and subtropical areas (see below), all sharing small, subtriangular, latero-oral avicularia ( Berning 2012; Pizzaferri & Berning 2007; Soule et al. 1991; Winston et al. 2014). These species differ from P. brasiliensis n. sp., however, in having a deeper orificial sinus (broad and shallow in P. brasiliensis n. sp.) and contrasting avicularian opesial morphology (subtriangular in P. brasiliensis n. sp.; trifoliate in P. foliosum ; elliptical in P. mediterraneum and P. porcellaniforme ).

At least three additional species of Plesiocleidochasma were reported from Brazil: P. acuminata Ramalho, Taylor, Moraes, Moura, Amado-Filho & Bastos, 2018 , P. arcuatum Ramalho & Moraes in Ramalho et al. 2021 and P. porcellanum ( Vieira et al. 2021) . Plesiocleidochasma acuminata is easily distinguished from P. brasiliensis n. sp. by the single, large, latero-oral avicularium with a trifoliate opesia (single or paired and small avicularia with triangular opesia in P. brasiliensis n. sp.). Differences between P. arcuatum and P. brasiliensis n. sp. include the shape of the sinus (V-shaped in P. arcuatum and U-shaped in P. brasiliensis n. sp.), adventitious avicularia (single and triangular in P. arcuatum and single or paired and drop-shaped in P. brasiliensis n. sp.), and ovicell labellum (trapezoidal in P. arcuatum and semicircular in P. brasiliensis n. sp.). Based on the lectotype specimens of P. porcellanum (see Berning 2012), this species is distinguished from P. brasiliensis n. sp. by the presence of two marginal pores (3–6 in P. brasiliensis n. sp.), the proximal margin of the primary orifice having a broader sinus that is slightly smaller than the distal region (orifice with a distinctly narrower sinus than the distal region in P. brasiliensis n. sp.), an often single latero-oral avicularium with an elliptical opesia (single or paired latero-oral avicularia with narrowly semicircular opesia in P. brasiliensis n. sp.) that is always directed laterally (often slightly oblique to the distal zooidal corners at an angle of 45 in P. brasiliensis n. sp.), and ovicell with median fenestra (with a semicircular labellum in P. brasiliensis n. sp.).

Different authors pointed out that specimens with small, subtriangular, latero-oral avicularia previously reported as P. porcellanum (attributed to different genera) from tropical and subtropical regions including Brazil (e.g., Cook 1964; Marcus 1937, 1955; Winston 1984; Vieira et al. 2018), may comprise distinct species (see also Berning 2012 for redescription of P. porcellanum ). Winston et al. (2014) also indicated that specimens from NE Brazil previously attributed to P. porcellanum ( Vieira et al. 2008) may represent an undescribed species. Ramalho et al. (2018) tentatively assigned specimens from Bahia (see Almeida et al. 2015a) to P. acuminata , but specimens reported from that locality are here reassigned to P. brasiliensis n. sp.

Distribution. Western Atlantic: Brazil (Bahia and Rio Grande do Norte). Plesiocleidochasma brasiliensis n. sp. is usually found as small colonies encrusting rhodoliths and calcareous nodules; 13‒ 53 m.

Figures

FIGURE 4. Plesiocleidochasma brasiliensis n. sp., UFBA 012.1, holotype (A–D), UFBA 1884.1, paratype (E, F). A. Overview of an encrusting colony.B. Detail of autozooids.C. Detail of primary orifice. D. Detail of ovicelled zooid. E. Group of autozooids with secondary calcification. F. Peristomial tubercles. Scale bars: A. 500 µm; B, D–F. 200 µm; C. 100 µm.