Stylopoma vilaensis Tilbrook, 2001

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, pp. 141-266 : 209-213

Stylopoma vilaensis Tilbrook, 2001

( Figure 23 (a – c))

Stylopoma vilaensis Tilbrook, 2001, p. 29 , fig. 12(a – c).

Material examined

NSMT-Te 1131 ( MIN- 5), bleached, on SEM stub; NSMT-Te 1132, lot of two dried specimens, MIN site; NHMUK 2016.5.13.43 – 46, lot of four dried specimens, MIN site.

Measurements

AzL, 0.51 – 0.69 (0.617 ± 0.049); AzW, 0.30 – 0.53 (0.395 ± 0.062). OrL (including sinus), 0.14 – 0.16 (0.150 ± 0.008); OrW, 0.14 – 0.16 (0.145 ± 0.006). Adventitious AvRostL, 0.05 – 0.08 (0.062 ± 0.007) (all preceding, n = 15, 1). Vicarious AvRostL, 0.458 (n = 1). Largest colony fragment 25 × 15 mm.

Description

Colony forming a unilaminar, encrusting sheet; colour white, with light brown opercula. Zooids ( Figure 23 (a)) distinct, delineated by suture line flanked by areolae. Frontal wall weakly convex, minutely granulated, uniformly covered with minute pseudopores except in zone proximal to orifice; each pore at base of infundibular depression. Eight to 10 slit-like areolae along each lateral margin, fewer along proximal and distal margins. Primary orifice ( Figure 23 (b)) terminal or nearly so; anter broader than long; median proximal sinus long, V-shaped; orifice completely surrounded by thick, slightly raised, granulated peristomial rim. Condyles sloping, smooth, without sculptured cap. Adventitious avicularium proximolateral to orifice on one side or other, lacking in some zooids; rostrum inclined to frontal plane, pointing distolaterally, with complete crossbar; mandible an equilateral triangle. Vicarious avicularia ( Figure 23 (c)) uncommon; same size as autozooids, with large, broadly spatulate rostrum; crossbar complete, mandible directed distally. No spines. Ovicell and ancestrula not observed.

Remarks

This species is characterised by the long, V-shaped suboral sinus; smooth, tapering condyles; minute frontal pores in infundibular depressions; small adventitious suboral avicularia; and vicarious avicularia with a large, broadly spatulate mandible. In the original description, Tilbrook (2001) notes that the suboral avicularia may be single or paired, although we observed no paired ones.

Occurrence

We found seven colonies or fragments at the MIN site. This species has been previously reported from 1 – 2 m depth at Vanuatu, and 0 – 54 m depth at East Timor (Tilbrook 2001) .

Family STOMACHETOSELLIDAE Canu and Bassler, 1917

Genus Junerossia Dick, Tilbrook, and Mawatari, 2006

Junerossia copiosa Dick, Tilbrook, and Mawatari, 2006

( Figure 23 (d – f))

Junerossia copiosa Dick, Tilbrook, and Mawatari, 2006, p. 2227 , fig. 10(a – h).

‘ Genus and species, not determined ’: Tilbrook 2006, p. 147, fig. 21(d – f).

Material examined

NSMT-Te 1133 ( MIN- 5), two specimens, bleached, on SEM stub; NSMT-Te 1134, three dried specimens, SES site; NSMT-Te 1135, four dried specimens, MIN site; NSMT-Te 1136, 23 dried specimens, REEF site; NHMUK 2016.5.13.47-51, five dried specimens, REEF site.

Measurements

AzL, 0.57 – 0.85 (0.661 ± 0.063); AzW, 0.32 – 0.59 (0.437 ± 0.069) (n = 31, 1). SecOrL, 0.13 – 0.19 (0.162 ± 0.017); SecOrW, 0.14 – 0.17 (0.155 ± 0.012) (n = 25, 1). OvL, 0.21 – 0.22 (0.214 ± 0.006); OvW, 0.31 – 0.34 (0.320 ± 0.012) (n = 6, 1). Largest colony observed 20 × 13 mm.

Description

Colony forming an encrusting sheet; mostly unilaminar, but frontal budding produces secondary layer in local areas; white, covered with glistening ectocyst. Zooids ( Figure 23 (d – f)) irregular in size and shape; delineated by groove. Frontal shield well calcified, finely granulated, covered with widely spaced pseudopores except in orificial region; with increased calcification, pseudopores become infundibular and frontal surface quite rugose ( Figure 23 (f)). Areolae inconspicuous. Primary orifice ( Figure 23 (d)) much broader than long, semicircular, visible only in young zooids at colony margin, soon obscured by thick, raised, tapering peristome, with characteristic ‘ necklace ’ of pores at base; peristomial lip with up to six or seven digitiform processes; secondary orifice approximately circular. Spines lacking. Ovicell ( Figure 23 (f)) hyperstomial, completely covered with secondary calcification of same granulated texture as frontal shield, often with rugose area or small umbo on top; pseudopores lacking. Embryos inside ovicells light yellow in our dried specimens.

Remarks

The material from Okinawa is indistinguishable from specimens from the type locality (Kapa ’ a Beach, Hawaii Island ); for a full description, see Dick et al . (2006).

Occurrence

Junerossia copiosa was prominent in the study area, common at the SES site and abundant at the REEF and MIN sites ( Table 1). Likely broadly distributed in warm Pacific waters, this species was previously known from Hawaii Island ( Dick et al. 2006) and Guadalcanal, Solomon Islands ( Tilbrook 2006).

Family HIPPOPODINIDAE Levinsen, 1909

Genus Hippopodina Levinsen, 1909

Hippopodina adunca Tilbrook, 2006

( Figure 24 (a, b))

Hippopodina adunca Tilbrook, 2006, p. 248 , pl. 54C, D.

Hippopodina feegeensis: Philipps 1900, p. 446 , pl. 63, fig. 7. Ristedt and Hillmer 1985, p. 137, pl. 2, fig. 12. Winston and Heimberg 1986, p. 16, figs 28 – 30. Hayward 1988, p. 319. Ryland and Hayward 1992 (in part), p. 256, fig. 17(a). Seo 1992, p. 150, pl. 1, figs 6 and 7. Tilbrook 1999 (in part), p. 451. Tilbrook et al. 2001, p. 88, fig. 18(a). Seo 2005, p. 431, pl. 159.

Material examined

NSMT-Te 1137 ( MIN- 24), bleached, on SEM stub; NSMT-Te 1138, seven dried specimens, MIN site; NSMT-Te 1139, two dried specimens, SES site; NSMT-Te 1140, large dried specimen, MIN site; NSMT-Te 1168 ( MIN- 35), bleached, on SEM stub (with

Crepidacantha longiseta ); NHMUK 2016.5.13.52-55, four dried specimens, MIN site; NHMUK 2016.5.13.56-58, three dried specimens, SES site.

Measurements

AzL, 0.80 – 1.09 (0.910 ± 0.080); AzW, 0.60 – 0.87 (0.708 ± 0.083) (n = 16, 1). AzOrL, 0.21 – 0.25 (0.230 ± 0.011); AzOrW, 0.19 – 0.24 (0.225 ± 0.012) (n = 16, 1). OvL, 0.64 – 0.78 (0.742 ± 0.047); OvW, 0.56 – 0.70 (0.658 ± 0.047) (n = 7, 1). SecOrOvZ: L, 0.19 – 0.23 (0.211 ± 0.014); W, 0.24 – 0.28 (0.261 ± 0.015) (n = 7, 1). Largest fragment 35 × 25 mm, but larger colonies occurred.

Description

Colony ( Figure 24 (a)) forming an extensive, mostly unilaminar, encrusting sheet; self-overgrowth or frontal budding can produce secondary layer in parts of colony; living colonies light reddish brown. Zooids large; rectangular or irregularly hexagonal, sometimes wider than long; distinct, separated by a groove. Frontal wall convex, finely granulated, covered with numerous tiny, closely spaced pseudopores. Orifice keyhole shaped; short, wide poster separated from anter by prominent condyles; proximal margin slightly concave. Avicularia adventitious, single or paired, distolateral to orifice across distal margin, angled slightly distomedially; mandible setiform, hooked at tip, directed distomedially and reaching midline or close to it, slightly curved in distal direction; hinge bar complete. Ovicell ( Figure 24 (b)) hyperstomial, globose, longer than broad, closed by operculum; ooecium occupying half or more of frontal shield of next-distal zooid, entirely covered with small, closely spaced pseudopores. Secondary orifice of ovicelled zooids D-shaped, shorter and wider than primary orifice of non-ovicelled zooids. Some ovicelled zooids retain a small avicularium on one side, in the usual position, with tip of rostrum extending slightly inside ooecial margin. Spines lacking. One ancestrular complex observed, forming a triad.

Remarks

Hippopodina adunca is superficially similar to and can be confused with Hippopodina feegeensis Busk, 1884 . Tilbrook (2006) clarified the differences between the two and listed several previous records attributable to the former that had been mistakenly assigned to the latter. One among several diagnostic differences is that the ancestrular complex in H. adunca is a triad, as in H. iririkiensis (next description), whereas that in H. feegeensis is a tetrad. Among the specimens we identified as H. adunca , one clearly shows a triad ancestrular complex. A previous record of H. feegeensis from Japan ( Mawatari 1974) has proven not to be H. adunca , but rather H. tahitiensis Leca and d ’ Hondt, 1993 ( Tilbrook 2006).

Occurrence

Hippopodina adunca was common at the SES site, where it co-occurred with H. iririkiensis , and abundant at the MIN site, where it did not ( Table 1). This species is broadly distributed in shallow waters of the Indo-West Pacific from Mauritius westward to Fiji ( Tilbrook 2006) and northward to Korea ( Seo 1992, 2005).

Figures

Figure 23. (a–c) Stylopoma vilaensis Tilbrook, NSMT-Te 1131: (a) autozooids; (b) orifice; (c) autozooids and vicarious avicularium at colony margin. (d–f) Junerossia copiosa Dick, Tilbrook, and Mawatari, NSMT-Te 1133: (d) young autozooids at colony margin; (e) older autozooids in colony interior; (f) heavily calcified ovicelled and non-ovicelled autozooids. All panels are scanning electron microscopic images of bleached specimens. Scale bars: a, c–f = 300 µm; b = 100 µm.

Figure 24. (a, b) Hippopodina adunca Tilbrook, NSMT-Te 1137: (a), view of colony; note small relative size of zooids in overgrowing Puellina harmeri colony at upper right; (b) ovicelled and non-ovicelled autozooids; note unusual presence of avicularium on ovicelled zooids. (c, d) Hippopodina iririkiensis Tilbrook, NSMT-Te 1141: (c) view of colony; (d) ovicelled and non-ovicelled autozooids. All panels are scanning electron microscopic images of bleached specimens. Scale bars: a, c = 1.0 mm; b, d = 500 µm.