Cauloramphus niger, 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 : 1081-1083

Cauloramphus niger new species

( Figure 12 )

Diagnosis

Zooids closely appressed; mural rim narrow, rounded, largely cryptocystal, covered with conical granules; gymnocyst reduced, evident proximally; 12–19 spines, including four to six vertical orificial spines and 8–13 curved opesial spines angled over opesia; spines light with dark bases in marginal zooids, dark brown to black in older zooids; avicularia single, numerous near colony periphery, longer than distal spines, with short peduncle rapidly expanding into chamber with terminal rostral face; mandible triangular, the tip rounded; kenozooidal ooecium much larger than in other species, granulated.

Etymology

The species name is from the Latin niger (dark coloured, black), referring to the colour of the spines.

Material examined

Holotype: DIN, seven colony fragments (NHM 2006.2.27.16). Paratypes: KAI, colony on rock (NHM 2006.2.27.41); KAI, ancestrular colony on rock (NHM 2006.2.27.17). Additional material: 664 specimens.

Description

Colony unilaminar, encrusting, coherent, forming irregularly circular patches up to 3 cm across; brown, dark yellow, or grey when alive, with reddish to pink marginal zone one or two developing zooids deep. Zooids ( Figure 12A–F ) oval to rounded-hexagonal, occasionally tapering proximally, 0.47–0.65 mm long (0.56¡ 0.04 mm), 0.30–0.45 mm wide (0.35¡ 0.03 mm), closely appressed, demarcated by a shallow groove. Mural rim ( Figure 12E ) narrow, rounded, largely cryptocystal, covered with conical granules. Gymnocyst reduced, smooth, occasionally elongate proximally between adjacent zooids, distinct from granulated mural rim. Opesia ( Figure 12E ) oval, widest in middle or sometimes proximally, 0.27–0.40 mm long (0.35¡ 0.03 mm), 0.17–0.28 mm wide (0.22¡ 0.02 mm), with crenulate outline due to granulation, occupying 60–80% of zooidal length. Around mural rim, 12–19 spines ( Figure 12B–D ), light yellowish with dark bases in marginal zooids, rapidly changing to entirely dark brown or black in older zooids, contrasting sharply with yellowish to greyish zooidal walls; two to three pairs of orificial spines long, hollow, thick, blunt, vertically orientated, with enlarged cylindrical bases, occasionally most distal pair reduced in size; 8–13 opesial spines thin, sharp, arched over opesia, occasionally meeting in midline; distance between adjacent opesial spines two to three times or more their basal thickness; in some proximally broadened zooids, one to four most proximal spines are vertically orientated and slightly longer and thicker than the others. Avicularia ( Figure 12C, D ) single, arising from distolateral gymnocyst between orificial and opesial spines, of same length as or slightly longer than orificial spines; short, thick peduncle rapidly expanding to thick, laterally compressed chamber with terminal rostral face; mandible triangular, the tip rounded, pointing in any direction, but most frequently laterally; avicularia numerous near periphery of colony but may be entirely absent in older areas. Kenozooidal ooecium ( Figure 12E ) distal to orifice is prominent, caplike, with granulose surface, occupying entire space between bases of distalmost spines. Six pore chambers in each lateral wall and two in distal wall. Ancestrula ( Figure 12F ) tatiform, oval, with entirely calcified basal wall, 0.39 mm long by 0.30 mm wide; large, oval opesia 0.28 mm long by 0.20 mm wide; 10 spines around opesial margin. Ancestrula buds triplet of small zooids distally and distolaterally, each with six or seven spines, including two pairs of hollow distal spines with enlarged bases and two or three thin proximal spines curving over opesia.

Remarks

Characters that distinguish C. niger from other reported species of this genus are the unusually large kenozooidal ooecium and the dark brown spines. The only other known species of Cauloramphus with similarly dark spines is C. brunnea Canu and Bassler, 1930 , originally described from the Galapagos Islands. However, whereas zooids of C. niger are closely appressed, those of C. brunnea are separated by a broad groove, so that the opesiae are about as far apart as their width. In addition, the avicularium of the latter species is long-pedunculate, narrowly fusiform, and attached proximal to the middle of the zooid, lateral to the zone of opesial spines. The light yellowish spines with dark bases on marginal zooids of C. niger are similar to spines of C. variegatus ( Hincks, 1881) ; however, the spines of the latter are never entirely dark brown, and other characters differ as well.

Distribution

Cauloramphus niger is known at present only from Akkeshi Bay.

Figures

Figure 12. Cauloramphus niger n. sp. (A–E) NHM 2006.2.27.16; (F) NHM 2006.2.27.17. (A) Developing zooids at colony margin, unbleached; (B) general view of group of zooids with immersed vestigial ovicells, unbleached; (C) zooids from colony periphery, showing numerous avicularia, unbleached; (D) close up of zooids with avicularia, unbleached; (E) autozooids with immersed ovicells and bases of spines, bleached; (F) ancestrula and periancestrular zooids, bleached. Scale bars: 0.5 mm.