Fenestrulina commensalis, Vieira, Leandro M. & Stampar, Sergio N., 2014

Vieira, Leandro M. & Stampar, Sergio N., 2014, A new Fenestrulina (Bryozoa, Cheilostomata) commensal with tube-dwelling anemones (Cnidaria, Ceriantharia) in the tropical southwestern Atlantic, Zootaxa 3780 (2), pp. 365-374 : 367-368

Fenestrulina commensalis n. sp.

( Figures 2 A–C, 3A–F; Table 1 )

Type material. Holotype. MZUSP 856, from Guaibura Beach (20°43'39.2" S, 40°31'17.7" W), Guarapari, Espírito Santo state, Brazil, on tubes of Pachycerianthus sp., 5–10 m, coll. S.N. Stampar, 10/12/2008 (part of specimen without organic tissues).

Etymology. The specific name alludes to the association of the species with the tube-dwelling anemone host.

Diagnosis. Unilaminar colonies anchored to substratum by chitinous rhizoids; hexagonal autozooids weakly connected to adjacent zooids; frontal shield with 50–70 reticulate pseudopores. Orifice transversely D-shaped with small proximal angular condyles and a single distal spine; orifice of ovicelled zooids wider than in non-ovicelled zooids; ascopore with median distal process and several short denticles on proximal edge of lumen; no avicularia; ooecia subglobular, longer than wide, with peripheral pores. Abfrontal surface of zooid often with 1–2 pore chambers.

Description. Colony unilaminar ( Fig. 2 A–B), loosely attached to substratum by chitinous rhizoids from abfrontal pore chambers ( Fig. 2 C). Autozooids hexagonal, longer than wide ( Table 1 ), separated by distinct grooves and slightly raised walls, with adjacent zooids weakly contiguous ( Fig. 3 A–B). Frontal shield almost flat; 50–70 reticulate pseudopores on frontal surface, these more densely spaced around orifice ( Fig. 3 C) and between orifice and ascopore ( Fig. 3 D); each pseudopore with 3–6 radial partitions subdividing the pore into deltoidpetaloid areas, each of which may also have a short radial denticle ( Fig. 3 C,D). Primary orifice dimorphic, wider than long ( Table 1 ), transversely D-shaped, with a pair of small angular condyles; ovicelled zooids with wider orifice than in non-ovicelled zooids. A single thin mid-distal spine in non-ovicelled zooids ( Fig. 3 C). Ascopore placed on frontal wall at c. three-fifths of zooid length, transversely ⊂-shaped, wider than long ( Table 1 ), with median distal process and 10–15 short denticles on proximal edge of lumen ( Fig. 3 D). Avicularium absent. Ooecia subglobular, smooth, slightly longer than wide ( Table 1 ), with a peripheral row of basal pores ( Fig. 3 B). Ancestrula not seen. Abfrontal surface of zooid often with 1–2 pore chambers ( Fig. 3 E–F).

Geographical distribution. The species occurs on tubes of Pachycerianthus sp. on the coast of Espírito Santo, Brazil, at 5–10 meters depth.

Remarks. More than 60 species of Fenestrulina have been described worldwide ( Bock 2013). Fenestrulina commensalis n. sp. is only the third species of the genus reported in Brazilian waters ( Vieira et al. 2008) and the first species in the Atlantic with only a single oral spine in infertile zooids ( Vieira et al. 2010a; see also below). Among the species reported in Brazil, Fenestrulina ampla Canu & Bassler, 1928 is known from Rio de Janeiro and São Paulo from 99–147 meters ( Vieira et al. 2010a) and Fenestrulina malusii ( Audouin, 1826) is reported from Espírito Santo ( Marcus 1955). Both are distinguished from F. commensalis in having more numerous oral spines (3 in F. ampla and 3–4 in F. malusii ) in non-ovicelled zooids and a less-porous frontal wall. The characteristic rootlets of the basal wall in F. commensalis are apparently lacking in F. ampla and F. malusii .

Two other species of Fenestrulina may have only a single oral spine— Fenestrulina harmeri Winston & Heimberg, 1986 from Indonesia and Fenestrulina delicia Winston, Hayward & Craig, 2000 from the NW Atlantic, Europe ( De Blauwe 2009) and the Gulf of Alaska to California ( Dick et al. 2005)—but basal rootlets have not been described in these species. Fenestrulina harmeri differs from F. commensalis in having shorter zooids (0.450– 0.540 mm long in F. h a r m e r i versus 0.635–0.790 mm long in F. commensalis ) and a narrow ascopore (0.036–0.054 mm wide in F. h a r m e r i versus 0.057–0.071 mm wide in F. commensalis ). Fenestrulina delicia has large zooids like those of F. commensalis , but it is distinguished by its ovicelled zooids with two oral spines (non-ovicelled zooids may also have 1–4 spines), shape of frontal pores (large and closely spaced in F. delicia ) and ascopore with irreguarly branched processes terminating in tiny projections.

Fenestrulina commensalis is most similar to Fenestrulina mutabilis ( Hastings, 1932) , described from Australia, in having rootlet-chambera in the basal wall and in the shape of frontal pores. Fenestrulina mutabilis has erect or slightly encrusting colonies anchored by chitinous rhizoids developing from 1–3 basal chambers (see Hastings 1932; Harmer 1957). Erect colonies were not observed in F. commensalis n. sp. Fenestrulina mutabilis is particularly distinguished from F. commensalis in having an oval uncalcified area in the distal part of basal wall and in the number of oral spines (one spine in F. commensalis n. sp. versus 2–4 spines in F. mutabilis ). Gordon (1984) also described a Fenestrulina from New Zealand with three large basal pores, Fenestrulina malusii pulchra (= Fenestrulina thyreophora (Busk, 1857)) ; it is distinguished from F. commensalis in having large and finely punctured frontal pores and no oral spines.

Figures

FIGURE 2. Fenestrulina commensalis n. sp. A – B, Colony on tube of tube-dwelling anemone Pachycerianthus sp.; C, abfrontal surface of the colony with abfrontal chitinous rhizoids. Scale bars: A, 0.6 mm; B, 0.3 mm; C, 0.25 mm.

FIGURE 3. Fenestrulina commensalis n. sp. A, Part of colony with autozooids and ovicelled zooids; B, zooids with ovicells; C, close-up of orifice; note the small angular condyles in the proximolateral corners and the single distal spine base; D, closeup of ascopore and frontal pseudopores. E – F, abfrontal surface of colony with holes indicating the location of abfrontal pore chambers. Scale bars: A, 0.5 mm; B, F, 0.15 mm; C, D, 0.05 mm; E 0.3 mm.

Tables

TABLE 1. Measurements (in mm) of Fenestrulina commensalis n. sp. from Brazil. Abbreviations: number (n), Min (minimum), Max (maximum), standard deviation (SD), zooid length (Lz), zooid width (Wz), orifice length (Lo), orifice width (Wo), orifice width in the ovicelled zooid (Wo 2), ascopore length (Lasc), ascopore width (Wasc), gap width of ascopore lumen (Gasc), pseudopore diameter (Dp), ooecium length (Lov) and ooecium width (Wov).

	Lz	Wz	Lo	Wo	Wo2	Lasc	Wasc	Gasc	Dp	Lov	Wov
n	10	10	10	10	10	10	10	10	10	10	10
Min	0.635	0.238	0.112	0.154	0.185	0.039	0.057	0.013	0.025	0.310	0.242
Max	0.790	0.417	0.122	0.172	0.200	0.043	0.071	0.016	0.034	0.338	0.248
Mean	0.695	0.334	0.115	0.165	0.196	0.042	0.065	0.014	0.030	0.322	0.267
SD	0.050	0.059	0.004	0.006	0.005	0.001	0.005	0.001	0.003	0.008	0.015