Bryopesanser serratus, 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 : 2233-2235

Genus Bryopesanser Tilbrook, 2006

Bryopesanser serratus new species

( Figure 12A–C )

Type material

Holotype: NHM 2006.7.21.17, specimen HI-66, bleached, coated for SEM; Kapa’a Beach Park, Island of Hawaii; 1 March 2005; M. H. Dick, collector; intertidal, 0.15 m low tide . Paratypes: same locality and collecting information as for holotype. Paratype 1, NHM 2006.7.21.18, specimen HI-3 (part), with Puellina sp. , bleached, coated for SEM. Paratype 2, YPM-38556, specimen HI-70, bleached, coated for SEM.

Etymology

The species name is from the Latin serratus (serrated), referring to the mandible of the avicularium.

Measurements

ZL, 0.50–0.75 (0.640¡0.084). ZW, 0.30–0.60 (0.430¡0.079). OrL (exclusive of sinus), 0.11–0.12 (0.112¡0.005). OrW, 0.12–0.14 (0.131¡0.009) (orifice n 55). OvL, 0.15–0.18 (0.162¡0.011). OvW, 0.18–0.20 (0.183¡0.008).

Description

Colony unilaminar, encrusting, sheet-like, small and irregular, the largest observed about 5 mm × 3 mm, with ovicells; light tan to cream in colour. Zooids irregularly hexagonal, widest at proximal third, narrowing distally, separated by a thin incision. Frontal wall ( Figure 12A ) moderately convex, uniformly granulated, covered with minute pores; pores may become constricted or occluded with increased calcification; there is a small, circular areolar pore at each of the angles of the lateral margin. Primary orifice ( Figure 12A, B ) exclusive of sinus broader than long; condylar shelves decorated with a row of fine denticles; condyles smooth, sloping; narrow sinus expanded proximal to opening. Peristome ( Figure 12B ) slightly raised, comprising a sharp, curved rim proximal to the orifice and a thickened rim laterally and distally that bears the swollen, closely set bases of seven oral spines; peristome not obscuring primary orifice. There is a large avicularium ( Figure 12A–C ) on one or both sides of the orifice; the area of the rostrum is equivalent to about half that of the orifice; rostrum with complete hinge bar and large, oval opesial opening; rostrum tilted distomedially, the mandibular end highly concave to accommodate mandible; mandible conspicuous, stout, setiform, serrate, extending beyond rostrum for a distance equal to or somewhat greater than zooidal width. Ovicell raised, hemispherical, broader than long, the proximolateral corners incorporating the distalmost two paired spines; with a smooth-textured but somewhat rugose surface; the proximal margin raised, thickened, sometimes developed into a smooth flange. The distal part of an ancestrula is shown in Figure 12C ; ancestrula smaller than, but of the same form as, subsequent zooids, including the oral avicularia, though spines are lacking; ancestrula gives rise to a daughter zooid laterally, and then to zooids of increasing size in a spiral budding pattern.

Remarks

Two similar-appearing species ( B. latesco and B. capitaneus ) described by Tilbrook (2006) from the Solomon Islands differ from B. serratus in having the long avicularian mandibles in the shape of a fan or duck’s foot, rather than stout, tapering, and serrated. Unfortunately, after observing the atypical mandibles, we inadvertently bleached all three specimens we collected of B. serratus , and thus cannot provide an illustration of this key character. In addition to the shape of the avicularian mandible, the following characters in combination separate B. serratus from the two species from the Solomons and from an Atlantic species, B. pesanseris , treated by Tilbrook (2006): zooids moderate in size; peristome flared, without proximal mucro; proximal margins of orifice flanking the sinus sloping rather than straight; frontal pores simple; both ovicell and avicularia large in proportion to orifice size, compared to the other species.

The diagnosis of the genus Bryopesanser ( Tilbrook 2006) includes fan-shaped mandibles. The serrated mandibles in B. serratus suggest that this generic character should be amended, because other characters indicate that the Hawaiian species belongs in this genus.

In his 2006 monograph, Tilbrook mentioned that he had been able to distinguish 11 morphologically distinct and geographically limited species of Bryopesanser among material from around the world that had been attributed to B. pesanseris ; he included descriptions and illustrations of only three of these. All of these species are highly similar in gross morphology, but differ in fine details and the relative sizes of the orifice, avicularia, frontal pores, and ovicell.

Distribution

Kapa’a Beach, Hawaii Island is the only known locality. Nominal B. pesanseris has previously been recorded from the Hawaiian Islands ( Canu and Bassler 1927; Soule et al. 1988).

Figures

Figure 12. (A–C) Bryopesanser serratus n. sp.: (A) paratype 1 (NHM 2006.7.21.18), autozooids; note predation hole in right-hand zooid; (B) holotype (NHM 2006.7.21.17), enlargement of distal end of an ovicellate zooid; (C) paratype 2 (YPM-38556), ancestrula (lower left-of-centre, broken) and periancestrular zooids, showing a spiral budding pattern. (D) Fenestrulina caseola Hayward: autozooid and ovicellate zooid. All specimens bleached. Scale bars: 400 Mm (A); 200 Mm (B); 500 Mm (C, D).