Microporella crustula, Hayward & Winston, 2011

Hayward, Peter J. & Winston, Judith E., 2011, Bryozoa collected by the United States Antarctic Research Program: new taxa and new records, Journal of Natural History 45 (37 - 38), pp. 2259-2338 : 2314-2315

Microporella crustula sp. nov.

( Figure 26 )

Material

Holotype. NMNH 1154041 : Eltanin cruise 11, station 974, 53 ◦ 32’ to 53 ◦ 34’ S, 64 ◦ 57’ to 64 ◦ 55’ W, 119–124 m, 12 February 1964; a single colony encrusting a piece of gravel.

Description

Colony encrusting, unilaminar. Autozooids oval to hexagonal, thickly calcified, convex, separated by distinct grooves. Primary orifice slightly wider than long, with a thickly calcified rim, and the proximal edge with a slight median convexity; six spines evenly spaced around lateral and distal borders of orifice, two persisting in ovicelled zooids. Frontal shield nodular, with a border of small, regularly spaced areolar pores, and 20 to 30 smaller pseudopores scattered frontally. Ascopore in distal half of zooid, forming a shallow crescent with a denticulate edge, recessed within a thick, oval rim; distance between proximal edge of orifice and distal edge of ascopore equivalent to orifice length. A single avicularium situated proximo-lateral to ascopore, on right or left; rostrum directed disto-laterally, short, its tip truncate and slightly flared, inferred to support a setiform mandible; crossbar stout, lacking a columella. Ovicell recumbent on distally succeeding autozooid, globular and prominent, its nodular surface with a conspicuous median umbo; aperture highly arched, with a broad lip of smooth calcification; imperforate frontally, but with a peripheral series of small pores.

Measurements

For all measurements n = 20, mean ± SD: autozooid length 0.74 ± 0.05 mm; autozooid width, 0.52 ± 0.05 mm; orifice length 0.16 ± 0.01 mm; orifice width 0.13 ± 0.01 mm.

Etymology

Latin, crusta: a hard outer surface, with reference to the thick, nodular frontal shield.

Remarks

Taylor and Mawatari (2005) noted that more than 150 species have been assigned to the genus Microporella , and that although perhaps one-third of these do not belong in the genus, its actual diversity is still obscured by incorrect attribution of material, from worldwide localities, to a few taxa formerly considered to be cosmopolitan in distribution. Kuklinski and Taylor (2008) usefully chose a neotype for the type species, M. ciliata (Pallas, 1766) . A single endemic Antarctic species is known, M. stenoporta Hayward and Taylor, 1984 , and two others have been described from the magellanic region, M. hyadesi (Jullien, 1888) and M. personata (Busk, 1854) . It is possible that M. crustula sp. nov. has been previously recorded from the southwest Atlantic as the “cosmopolitan” M. ciliata (Pallas, 1766) , but it differs from northeast Atlantic specimens attributed to that species in the proportions of its primary orifice, which is wider than long in M. ciliata , in its smaller ascopore and more delicate frontal pores. Further, the adventitious avicularium is much larger in M. ciliata , and the ovicell is shorter and less prominent, and lacks the conspicuous umbo seen in the new species.

Figures

Figure 26. Microporella crustula sp. nov. Holotype. (A) Ovicelled zooids; (B) a single autozooid, showing detail of the primary orifice. Scale bars: 0.25 mm (A), 0.125 mm (B).