Sclerodomus myriozoides ( Busk, 1884 )

Branch, M. L. & Hayward, P. J., 2005, New species of cheilostomatous Bryozoa from subantarctic Marion and Prince Edward Islands, Journal of Natural History 39 (29), pp. 2671-2704 : 2689-2690

Sclerodomus myriozoides ( Busk, 1884)

( Figure 6 C–E) Reteporella myriozoides Busk 1884, p 127 , Plate 24, Figure 2 . Sclerodomus myriozoides: Gordon 1988, p 254 , Figures 12 –15.

Material

St. 45 Marion Island (47 ° 00 9 S, 37 ° 55 9 E), 420–540 m, on rock, SAM A27530 ; St. 39 Marion Island (46 ° 60 9 S, 38 ° 01 9 E), 360–376 m, on rock, SAM A27019 ; St. 42 Marion Island (46 ° 40 9 S, 37 ° 50 9 E), 460–560 m, on rock, SAM A27535 ; St. 52 Marion Island (46 ° 55 9 S, 37 ° 34 9 E), 340–400 m, on rock, SAM A27492 .

Description

Colony, erect, branching at irregular intervals, attached basally by chitinous rhizoids; at least 40 mm high, with cylindrical branches up to 1 mm diameter. Autozooids in four alternating longitudinal series (two series at branch tips), their apertures occupying about three-quarters of the branch circumference, defining a clear abfrontal surface; approximately 0.8X 0.4 mm but individual autozooid boundaries indistinct. Aperture circular, wider than long; 0.2X 0.16 mm, with a low, medio-proximal umbo, more pronounced in early ontogeny; a short lip present within the proximal rim, and a laterally orientated, adventitious avicularium, with short, triangular mandible, situated below it, deep within the peristome. A small laterally orientated frontal avicularium present proximal to the aperture in a minority of autozooids. Frontal shield of autozooids with marginal perforations; developing a reticulate secondary calcification which thickens progressively, and appearing regularly porous with elongate perforations in sinuous lines around the apertures. Ovicell not apparent in present material.

Remarks

Reteporella myriozoides was founded by Busk (1884) on material from a single station, at 210–500 fm depth, off Crozet Island, and does not seem to have been collected subsequently. Gordon (1988) re-examined, and redescribed, Busk’s specimens, demonstrating that R. myriozoides should be assigned to Sclerodomus . SEM illustrations of a syntype specimen ( Gordon 1988, Figures 12 –15) are closely similar to those of the Marion Island material ( Figure 6C, D ). Gordon stated that autozooids of the Crozet syntype colony were ordered in six longitudinal series, whereas those of the Marion Island specimens are in series of four. However, this difference may be an astogenetic or ecophenotypic effect, in other respects the Marion Island species seems identical to S. myriozoides , and considering the proximity of the two localities a single taxon seems most probable.

Figures

Figure 2. Pyriporoides judyae sp.nov., SAM A27566:(A)autozooids showing cryptocyst and opesia, X40; (B) ovicelled autozooid, X80; (C) autozooid, X100; (D) colony showing autozooids, small zooids and ovicelled zooid, X40.

Figure 6. (A, B) Filaguria lithocrustata sp. nov., SAM A27523: (A) ovicelled autozooid, X70; (B) autozooids and a small kenozooid, X40. (C–E) Sclerodomus myriozoides, SAM A27530: (C) part of colony plus young branch, X15; (D) abfrontal view of colony showing four series of autozoids, X30; (E) aperture showing associated avicularia.

Figure 12. Reteporellina berylae sp. nov., SAM A27527: (A) autozooids and ovicelled autozooids with small adventitious avicularia, X50; (B) part of the colony showing large irregular fenestrulae, X10; (C) small frontal avicularium, X125; (D) ovicell and aperture, X70; (E) large avicularium, X65.