Metacleidochasma verrucosa, Dick & Tilbrook & Mawatari, 2006

Dick, Matthew H., Tilbrook, Kevin J. & Mawatari, Shunsuke F., 2006, Diversity and taxonomy of rocky-intertidal Bryozoa on the Island of Hawaii, USA, Journal of Natural History 40 (38 - 40), pp. 2197-2257 : 2240-2242

Genus Metacleidochasma Soule, Soule, and Chaney, 1991 Metacleidochasma verrucosa new species

( Figure 14A–C )

? Metacleidochasma ovale Soule et al. 1991, p 480 , Plate 1, Figure 7 , Plate 4, Figures 1 , 2 .

Type material

Holotype: NHM 2006.7.21.21, specimen HI-46, bleached, coated for SEM; Kapa’a Beach Park, Island of Hawaii; 1 March 2005; M. H. Dick, collector; intertidal, 0.15 m low tide.

Etymology

The species name derives from the Latin verrucosus (warty), referring to the finely tuberculate frontal wall.

Measurements ZL, 0.29–0.53 (0.370¡0.068). ZW, 0.21–0.33 (0.272¡0.032). OrL, 0.09–0.11

(0.104¡0.008). OrW, 0.08–0.09 (0.084¡0.006).

Description A single small colony was found, 4 mm × 2.5 mm. Colony unilaminar, encrusting, sheet-

like, white; zooids irregularly hexagonal, rounded distally. Frontal wall ( Figure 14A ) flat, finely tuberculate, with a single rimmed pore near each lateral margin near middle of zooid; many zooids have a low umbo on each side lateral to orifice. Orifice ( Figure 14B ) terminal, keyhole-shaped, the anter an interrupted circle in outline and separated from broad, curved poster by prominent, sharp condyles directed posteromedially. Marginal zooids usually with three distal spines (range two to four). Our specimen lacks avicularia and ovicells, though other species of this genus typically have frontal avicularia and a globose ovicell that is immersed to a greater or lesser extent, with a slit near proximal margin ( Soule et al. 1991). Ancestrula ( Figure 14C ) like subsequent zooids and with a similar orifice, but smaller, without frontal pores, and with five distal spines; surrounded by six periancestrular zooids: one distal, two distolateral, two proximolateral, one proximal.

Remarks

Soule et al. (1991) originally described a similar species, M. ovale , from Lahaina, Maui, Hawaiian Islands, and reported this species to occur broadly in the Indo-West Pacific. Tilbrook et al. (2001) later synonymized M. ovale with M. planulata ( Canu and Bassler, 1929) , originally described from the Philippine region. Although Soule et al. (1991) did not describe the ancestrula of M. ovale, Tilbrook et al. (2001) illustrated a tatiform ancestrula for M. planulata . The ancestrula ( Figure 14C ) in our single specimen is clearly not tatiform, and our specimen further differs from descriptions of M. planulata and M. ovale in having a coarsely tuberculate frontal wall, even in periancestrular zooids, and marginal zooids usually with three rather than four distal spines.

Distribution

Kapa’a Beach on the northwest coast of Hawaii Island is the only known locality.

Figures

Figure 1. Outline map of the Island of Hawaii, showing the location of the main town, Hilo, and the four localities examined for bryozoans (smaller circles).

Figure 2. Photographs of rock-pile habitats examined at study sites on the Island of Hawaii; all taken within an hour of low tide (20.03 to +0.15 m referenced to mean lower low water). (A) Kealakekua Bay; study site is shallow inlet beginning at centre and extending to just below left centre; plastic kayak at upper right indicates scale. (B) Whittington Beach Park; sheltered lagoon inside benchrock barrier, part of which can be seen in distance at far upper right; scale indicated by water bottle at lower left. (C) Kapa’a Beach Park; an exposed site with roundedboulder beaches (centre) and solid benchrock (in distance, upper right); sampling site was a tidepool in the benchrock just beyond the upper right of the photograph. (D) Kiholo Bay; entrance to large lagoon separated from the sea by a long barrier spit, on which palm and other trees are growing; end of spit is seen just above right centre, with lagoon evident beyond that in the distance; the shallow area with boulders protruding from water, left to right just below centre, was examined for bryozoans; photograph taken about an hour before low tide.

Figure 7. (A, B) Hippothoa flagellum Manzoni: (A) autozooid; (B) autozooid (part) and ovicellate zooid. (C, D) Chorizopora brogniartii (Audouin) sensu lato: (C) autozooids, ovicellate zooids, interzooidal kenozooids, and avicularia; (D) ancestrula (lower left) and early astogeny. (E, F) Poricella spathulata (Canu and Bassler): (E) autozooids, ovicellate zooids, and interzooidal avicularia; (F) ancestrula (bottom centre) and periancestrular zooids. All specimens bleached. Scale bars: 200 Mm (A, B); 500 Mm (C–F).

Figure 14. (A–C) Metacleidochasma verrucosa n. sp., holotype (NHM 2006.7.21.21): (A) autozooids; (B) enlargement of orifice; (C) ancestrula. (D–F) Rhynchozoon ferocula Hayward: (D) view of entire colony; this small colony of 27 zooids has produced eight ovicells; (E) ovicellate zooids; (F) enlargement of primary orifice. All specimens bleached. Scale bars: 400 Mm (A, E); 100 Mm (B, C, F); 1 mm (D).