Celleporina minima, Grischenko & Dick & Mawatari, 2007

Grischenko, Andrei V., Dick, Matthew H. & Mawatari, Shunsuke F., 2007, Diversity and taxonomy of intertidal Bryozoa (Cheilostomata) at Akkeshi Bay, Hokkaido, Japan, Journal of Natural History 41 (17 - 20), pp. 1047-1161 : 1136-1138

Celleporina minima new species

( Figure 36 )

Diagnosis

Colony small, pisiform, up to 6 mm in diameter. Colony surface very irregular, with numerous knob-like lobes. Zooids erect, cylindrical, haphazardly orientated. Distal pores encircle an oval orifice with a V-shaped sinus. Orifice flanked by paired lateral avicularia on columnar chambers that are straight or curved inward, narrowing terminally, with a small, oval rostrum angled to plane of orifice, the semicircular mandible pointing laterally. Zooids with completed avicularia have a narrow, transverse, slit-like fold in proximal peristomial lip. Vicarious avicularia rare; with broadly spatulate mandible. Ovicell hyperstomial, globose, recumbent on neighbouring zooids; tabula small; circular, semicircular, or roughly triangular, with slit-like, radially arranged pores.

Etymology

The species name refers to the small size of colonies, which can be mature at a few millimetres in diameter.

Material examined

Holotype: ACT, five colonies detached from hydroid stolon (NHM 2006.2.27.97). Paratype: ANC, eight colonies detached from hydroid stolon (NHM 2006.2.27.98). Additional material: eight specimens.

Description

Colony ( Figure 36A ) pisiform, small, up to 6 mm in diameter, with multilayered arrangement of zooids, one over other, light pink when alive. Surface of colony very irregular with knob-like lobes. Zooids ( Figure 36B ) erect, cylindrical, 0.23–0.30 mm across (0.26¡ 0.02 mm), haphazardly orientated. Frontal wall convex, smooth, with a row of areolar pores; pore openings carried around orifice and encircling it. In some zooids, frontal wall rises to a small, wide umbo proximal to orifice. Primary orifice ( Figure 36D ) oval, 0.11–0.15 mm long (0.13¡ 0.01 mm), 0.10–0.14 mm wide (0.12¡ 0.01 mm), with small, flattened condyles and deep, V-shaped proximal sinus. Secondary orifice ( Figure 36C–E ) formed by peristomial lip proximally and by lateral columnar avicularia laterally. Avicularian columns ( Figure 36C ) on each side lateral to orifice long, stout, wide at base, tapering distally, with a small, round or oval, terminal rostrum tilted at an angle to the orificial plane and with a complete cross-bar, the semicircular mandible directed laterally; columns straight or curved inward, often submerged in sub-surface zooids. Development of avicularia accompanied by formation of narrow, transverse slit-like fold ( Figure 36C ) in proximal peristomial lip. Vicarious avicularia rare, scattered over colony surface, about 0.13–0.25 mm long, with complete cross-bar and semicircular ( Figure 36E ) to broadly spatulate ( Figure 36F ) mandible; rostral opesia large. Ovicell ( Figure 36B, D–F ) hyperstomial, globose, 0.18–0.23 mm long (0.20¡ 0.01 mm), 0.24–0.30 mm wide (0.26¡ 0.02 mm), recumbent on neighbouring zooids, initially prominent, subimmersed with age; tabula small; circular, semicircular, or roughly triangular, with slit-like, radially arranged pores. Ancestrula and early astogeny not observed.

Remarks

Celleporina minima n. sp. is similar to the Arctic-Boreal species C. nordenskjoldi in having a pisiform colony, columnar lateral avicularia, and globular, recumbent ovicells. However, colonies of C. minima are always smaller and can have ovicellate zooids at a diameter of just a few millimetres. Avicularian columns of C. minima tend to be curved inward, narrow terminally, with the rostrum angled to the orificial plane and the mandible directed laterally. The avicularian columns of C. nordenskjoldi are long and stout, do not narrow terminally, and are usually straight or only slightly curved inward; the mandible is directed distolaterally. Though the ovicells are quite similar in form in these two species, the tabula is much smaller in C. minima , its diameter one-third to one-half the width of the proximal orifical margin; the tabula in C. nordenskjoldi is usually nearly as wide as the proximal margin of the ovicell.

Distribution

Akkeshi Bay is the only known locality.

Figures

Figure 36. Celleporina minima n. sp. (A–C, F) NHM 2006.2.27.97; (D, E) NHM 2006.2.27.98. (A) General view of colony; (B) immature zooid surrounded by ovicellate zooids; (C) two zooids with developing ovicells, showing avicularian columns and external transversal slit-like fold in proximal peristomial lip; (D) zooids with developing and completed ovicells, showing form of primary orifice with deep proximal sinus; (E, F) ovicellate zooids surrounded by vicarious avicularia. Scale bars: 2 mm (A); 0.5 mm (B, D–F); 0.2 mm (C).