Calyptotheca sesokoensis, Dick & Grischenko, 2016

Dick, Matthew H. & Grischenko, Andrei V., 2016, Rocky-intertidal cheilostome bryozoans from the vicinity of the Sesoko Biological Station, west-central Okinawa, Japan, Journal of Natural History 51 (3 - 4), pp. 141-266 : 203-204

Calyptotheca sesokoensis sp. nov.

( Figure 20 (b–d))

Etymology

The specific name is a Latinised adjective referring to the type locality, Sesoko Island , Okinawa .

Material examined

Holotype: NSMT-Te 1128 ( SES-1 ), bleached, on SEM stub.

Measurements

AzL, 0.51–0.68 (0.585 ± 0.049); AzW, 0.31–0.55 (0.403 ± 0.062) (n = 20, 1). AzOrL, 0.13– 0.15 (0.136 ± 0.008); AzOrW, 0.15–0.16 (0.156 ± 0.005) (n = 5, 1). OvZOrL, 0.13–0.15 (0.143 ± 0.008); OvZOrW, 0.17–0.18 (0.178 ± 0.004) (n = 6, 1). OvL, 0.33–0.42 (0.366 ± 0.037); OvW, 0.40–0.47 (0.419 ± 0.033) (n = 4, 1). One colony fragment, 12 × 6 mm.

Description

Colony forming a unilaminar, encrusting sheet. Zooids ( Figure 20 (b–d)) distinct, delineated by raised suture line flanked by areolae; variable in shape, irregularly hexagonal, rectangular, barrel shaped or spindle shaped, sometimes wider than long. Frontal wall moderately convex, mildly rugose, uniformly covered with circular infundibular pseudopores; with five to seven slit-like areolae along each lateral margin, areolae sometimes enlarged. Orifice ( Figure 20 (c)) transversely oval; condyles prominent, blunt; sinus broad, concave, its curvature more or less continuous with that of anter. Orifice usually located in midline, but sometimes offset to distolateral corner on either side ( Figure 20 (b)). Orifice weakly dimorphic, slightly larger in ovicelled than in non-ovicelled zooids. Zone proximal and lateral to orifice thickened and raised as low, crescentic ridge, smooth on inner curvature. Proximal end of zooid often with wide zone of smooth, imperforate gymnocyst that, together with corresponding zone around orifice of preceding zooid, forms flared, smooth, cormidial peristomial region ( Figure 20 (c)). Only one avicularium observed in entire colony ( Figure 20 (c)); small (rostrum 0.09 mm long), proximolateral to orifice; crossbar thin, complete; mandible long-triangular, acute, pointing proximomedially. Ovicell ( Figure 20 (d)) large, hyperstomial. Ooecium covered with rugose secondary calcification, with pseudopores distributed over entire surface. Zooids interconnect by up to five uniporous septula in transverse wall and five or more in each distolateral wall. Spines lacking. Ancestrula not observed.

Remarks

Calyptotheca sesokoensis sp. nov. is similar to C. rupicola Hayward and Ryland, 1995 , described from the Great Barrier Reef, Australia. The latter species likewise has avicularia present only rarely; when present, they are similar in position and orientation to those in C. sesokoensis , but have a rostrum about twice as long. Calyptotheca rupicola also differs in having a broader orifice relative to orifice length; pseudopores over the entire frontal wall, which is more coarsely rugose, with rounded tubercles between pseudopores; and a curved band of stout tubercles proximal to the orifice. Zooids in C. rupicola lack the smooth proximal gymnocystal area that contributes to the cormidial circum-oral region seen in C. sesokoensis . Another similar species is Calyptotheca tenuata Harmer, 1957 , zooids of which have an unpaired avicularium proximolateral to the orifice. In C. tenuata , the avicularia are larger and more frequent than in C. sesokoensis ; the orifice is broader and likewise lacks the smooth, cormidial circum-oral region seen in C. sesokoensis . The cormidial circum-oral region in C. sesokoensis resembles that in material from China that Liu et al. (2001, pl. 62, figs 5 and 6); identified as C. parcimunita Harmer, 1957 , a species originally described from Indonesia. The Chinese material differs from our specimen in having tiny avicularia, single or paired lateral or distolateral to the orifice, with an acute, long-triangular mandible directed medially.

Occurrence

We found a single colony at the SES site, the only known locality.