Micropora nodimagna, Ramalho, Laís V. & Calliari, Lauro, 2015

Ramalho, Laís V. & Calliari, Lauro, 2015, Bryozoans from Rio Grande do Sul Continental Shelf, Southern Brazil, Zootaxa 3955 (4), pp. 569-587 : 572-574

Micropora nodimagna sp. nov.

( Fig. 3 A–C)

Material examined. Parcel do Carpinteiro, Rio Grande do Sul, Brazil: Holotype: MNRJ-1166 and Paratype: MNRJ-1167, am28, point 2, 32°08.402’S, 51°28.045’W, 28 August 2009.

Diagnosis. Colony encrusting, unilaminar. Autozooids rectangular with frontal wall perforated by small pores; orifice D-shaped, large ‘knobs’ lateral to the orifice; oecia are smooth, hood- to crescent-shaped with a triangular suture medially and several transverse lines on the proximal region, near the orifice.

Description. Colony encrusting shell, unilaminar. Autozooids slightly longer than wide (358–527 (433) µm long x 291–464 (345) µm wide), budding in a fan-shaped arrangement; frontal cryptocystal wall crenulated and perforated by tiny rounded pores and at each corner one small opesiule, rounded to slightly elliptical in shape ( Fig. 3 A). Lateral border and rim below the orifice elevated, thick, and granulose, meeting each other at the proximal corners of the orifice in large, elliptical protuberances (knobs) (50–71 (61) µm long x 75 –107 (86) µm wide)( Fig. 3 A–B). Orifice D-shaped (64–79 (72) µm long x 86 –109 (102) µm wide) the anter semi-circular and poster practically straight ( Fig. 3 A–C).

Oecium hood-shaped to half-moon-shaped (100–154 (125) µm long x 200–264 (242) µm wide), wider than long, with a median triangular suture and several transverse lines on the proximal region, near the orifice ( Figs. 3 A and C).

Avicularia not observed.

Etymology. The name nodimagna refers to the large protuberances (knobs) at the side of orifice of this species (Latin nodus = knot, tubercle; magna = large).

Geographic distribution. Rio Grande do Sul State–Parcel do Carpinteiro (present study).

Remarks. Winston (2005) synonymised Micropora coriacea described by Marcus (1949, 1955) with M. acuminata ( Winston, 2005) , and Winston et al. (2014) described another species from Brazil, M. angistiscapulis (Bahia State). These are the two only species described from Brazil until now. But the former species has larger zooids (560–864 (670) µm long x 460–594 (540) µm wide), a coarse frontal surface, the protuberances on the corner are very small (in comparison with our species), the surface of the oecium is crenulate like the surface wall; Smitt’s illustration (see Smitt 1873, fig. 74) shows interzooidal avicularia. The latter species ( M. angistiscapulis ), is similar to M. nodimagna by the lateral oral large protuberances, but it can be distinguished as it has polygonal and smaller autozooids (342–450 (396) µm long x 234–360 (291) µm wide), beaded cryptocyst with rounded pores with radiating spines, shorter orifice (45–54 (51) µm long), smaller and rounded knobs located just below the proximal rim of the orifice, and opesiules narrowly oval slits.

Practically all species of Micropora have avicularia located just distal of the zooidal orifices, however they can be absent on some colonies. M. c oriacea (Johnston, 1847) also lacks avicularia. However, this species is distinguished from M. nodimagna because it does not display large protuberances and the oecium shape is different.

Moyano (1994) described Micropora karukinkaensis and M. selknami from the Magellan Strait, and both have large protuberances and similar zooidal measurements. M. karukinkaensis has orifice measurements that are shorter and wider (40–63 (50) µm long x 100–150 (131) µm wide), the oecium is composed of the oecium proper and a kenozooid in which it is developed, so becoming a very long structure (250–275 (260) µm long); Micropora selknami has smaller knobs, and a slightly different aperture size (38–63 (51) µm long x 100–150 (123) µm wide), with additional proximal dentate crescentic opesiules and an oecium with a different form (Moyano 1994). M. normani Levinsen, 1909 is another species with large lateral protuberances, but it has smaller zooids (320–400 µm long x 220–320 µm wide), fewer frontal pores (about 15), a granulose oecium, and frequent avicularia.

Micropora brevissima Waters, 1904 described from Antarctic does not have the protuberances but avicularia are frequent, and the oecium is granulose. In M. robusta Cook, 1985 again, the protuberances are absent and the zooidal measurements are large.

Therefore, we believe that the specimens collected on the continental shelf of Rio Grande do Sul represents a new species.

Figures

FIGURE 3. Micropora nodimagna sp. nov. (A, C: MNRJ- 1166; B: MNRJ- 1167). A, colony fragment showing fertile and nonfertile zooids; B, frontal view of some non-fertile autozooids; C, fertile zooid with an ooecium. Scalebars: A, 200 µm; B, C, 100 µm.