Disporella compta, 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 : 2245-2247

Disporella compta new species

( Figure 16A–D )

Type material

Holotype: NHM 2006.7.21.22, specimen HI-53, bleached, coated for SEM; Kapa’a Beach Park, Island of Hawaii; 1 March 2005; M. H. Dick, collector; intertidal, 0.15 m low tide . Paratype 1, NHM 2006.7.21.23, same locality and collecting information as for holotype, specimen HI-71, partly overgrown by Junerossia copiosa , bleached, coated for SEM.

Etymology

The species name is from the Latin comptus (formed, framed, neat), referring to the welldelineated maculae imparting a tidy appearance to the surface of the colony.

Measurements

Peristomial openings slightly longer in radial than transverse direction, 0.08–0.10 (0.089¡0.009)×0.07–0.09 (0.080¡0.008), respectively. Kenozooidal openings 0.08– 0.11 (0.088¡0.015).

Description

Two colonies found, one complete and the other a fragment. Colony approximately circular, convex, adnate, but with marginal lamina raised from substratum; light violet in colour; marginal lamina traversed by raised, closely spaced radial lines indicating lateral boundaries of incipient zooids; the complete colony measures 7 mm × 8 mm; the other is broken and partly overgrown by an ascophoran, and measures 6 mm in maximum dimension. Cormidial arrangement of larger colony ( Figure 16A ) clearly evident, with seven maculae, six of them oval or elongate-oval, and the other narrowly elongate, twothirds as long as colony diameter; macula of the colony fragment is narrow and elongate. Surfaces of maculae ( Figure 16B ) sunken, regular; due to constriction of kenozooidal openings, maculae appear less porous than intermacular areas; maculae are well delineated and can be easily counted with the naked eye. Peristomes in uniserial connate radii two to four peristomes in extent ( Figure 16B, C ) and orientated perpendicular to macular margin, with occasional single peristomes at periphery of cormidial unit (macular area and surrounding radii); peristomes sometimes vertically orientated near macula but generally angled toward colony margin, tallest at macular end of series, lowest at abmacular end; fused along entire length; ends truncate, somewhat irregular; peristomial openings slightly oval. Kenozooidal openings circular or oval, usually as large as or larger than peristomial openings in areas outside maculae; often constricted by centripetal growth of surface calcification within maculae, but not closed. Two columns of kenozooids between connate columns of peristomes; three to five rows between cormidial (macular) units. Inner walls of kenozooids and zooidal peristomes have numerous palm-tree-shaped pinhead spinules ( Figure 16D ), the heads with five to seven sharp rays. Brood chambers lacking in our specimens.

Remarks

Disporella compta is similar to D. californica (d’Orbigny, 1853) and D. ovoidea Osburn, 1953 , both of which are fairly widely distributed in the subtropical to tropical Eastern Pacific, sharing with these species the following characters: connate, uniserial radii; pinhead spinules (abundant in D. californica , rare in D. ovoidea ); peristomial tubes only moderately tall, and truncate; colonies small. However, D. compta differs from these species in having at most four peristomes in a connate column; D. californica has around 10, and D. ovoidea , seven. The macular cormidia of D. californica appear to be nearly circular ( Osburn 1953), larger in proportion to colony size, and hence less numerous than in D. compta ; furthermore, D. californica also commonly undergoes zoarial budding, producing smaller, short-stipitate colonies at the margin, which was not observed in D. compta . Disporella ovoidea appears typically to have only a single large, central macular area, with radii extending from the macular margin to the colony margin. Disporella compta may eventually prove to be a geographic or ecophenotypic variant of one of these species; examination of brood chambers in Hawaiian material will help resolve this issue.

Distribution

Kapa’a beach, Hawaii Island, is the only known locality.

Figures

Figure 16. Disporella compta n. sp., holotype (NHM 2006.7.21.22): (A) partial view of colony, showing one elongate and two oval maculae among seven maculae present in colony; (B) enlargement of a macula; (C) columns of fused peristomes of three to four autozooids; (D) enlargement of kenozooidal opening showing palm-tree-shaped pinhead spinules. All specimens bleached. Scale bars: 2 mm (A); 1 mm (B); 400 Mm (C); 50 Mm (D).