Reptadeonella riatanae, Jain & Gordon & Huang & Kuklinski & Liow, 2022

Jain, Sudhanshi S., Gordon, Dennis P., Huang, Danwei, Kuklinski, Piotr & Liow, Lee Hsiang, 2022, Targeted collections reveal new species and records of Bryozoa and the discovery of Pterobranchia in Singapore, Raffles Bulletin of Zoology 70, pp. 257-274 : 265-266

Reptadeonella riatanae , new species

( Fig. 4A‒C )

Material examined. Holotype: ZRC.BRY.0923 (Zoological Reference Collection, Lee Kong Chian Natural History Museum; collected as SG2019 No. 126; sequenced as BLEED No. 1523), Pulau Tekukor (1.2299°N, 103.8376°E), Singapore, 15‒17 m, coll. S.S. Jain & P. Kuklinski, 6 May 2019.

Etymology. Honorific for Ria Tan, tireless promoter of knowledge of Singapore’s biodiversity, notably through the WildSingapore website (http://www.wildsingapore.com).

Diagnosis. Colony encrusting, unilaminar, small. Zooidal frontal shield nodular-tubercular. Orifice transversely oval to bean-shaped. Spiramen longitudinally slit-like, immediately proximal to avicularium. Suboral adventitious avicularium single, variable in size, not symmetrically placed; rostrum acute. Large vicarious avicularia rare, at colony margin, of similar shape to adventitious avicularia. Obvious gonozooids not evident, but some autozooids have larger orifices. Ancestrular complex a tetrad.

Description. Colony encrusting, unilaminar, multiserial, up to 5–7 mm diameter, found on sponge. Colour in life purplish. Zooids arranged regularly in quincunx or surrounded by seven zooids at the bifurcation of zooid rows, separated by furrows with a thin boundary line. Zooids variably subhexagonal, widest in middle or parallel-sided [ZL 345‒563 (429), n = 15; ZW 235‒297 (256), n = 15]. Frontal shield umbonuloid, with nodular-tubercular surface and 19‒23 conspicuous marginal areolar-septular pores. Orifice wider than long, oval to bean-shaped, with straight to slight convex proximal margin [OrL 40‒59 (52), n = 15; OrW 76‒104 (91), n = 15]. A single conspicuous avicularium on each autozooid, borne adventitiously between the orifice and spiramen, variable in size [AvL 95‒149 (123), n = 15; AvW 52‒84 (71), n = 15]; the rostrum triangular, somewhat longer than wide, with tiny distal palate and large subquadrate foramen, the proximal margin of the mandible arcuate; avicularian cryptocyst subcrescentic smooth; mandible concealing spiramen when open. Spiramen elongate (up to 70 μm long) and exceptionally narrow, especially midlength, orientated longitudinally or obliquely so proximal to the avicularium. Vicarious avicularia occur at or near the colony margin, the rostrum and opesia having the same proportions as the adventitious avicularia [VavL 240‒300 (263), n = 4; VavW 157‒203 (176), n = 4]. Gonozooids not evident, but some of the larger zooids with wider orifices may function as such. Ancestrular complex a tetrad of zooids, their proximal ends converging.

Remarks. The Bryozoa Home Page ( Bock, 2022) lists 35 described species of Reptadeonella , 28 of which are living and the remainder exclusively fossil. All are restricted to particular regions, with 11 species now known from the tropical to subtropical western Pacific and eastern Indian Oceans. Prior to 2001, only three species were known from the region ( Harmer, 1957). Tilbrook et al. (2001) added three more species (two of them new) from Vanuatu, Tilbrook (2006) described four more from the Solomon Islands, and Yang et al. (2018) described a new species from subtropically influenced Jeju Island, South Korea. None of these has a slit-like spiramen and, in those for which early astogeny is known, the ancestrular complex is a triad not a tetrad. Examination of descriptions and illustrations of all remaining living species of Reptadeonella shows that they all have a circular or transversely crescentic or oval spiramen (e.g., Almeida et al., 2015; Haugen et al., 2020; Winston & Jackson, 2021). The two Miocene species from Kalimantan also have a circular spiramen ( Di Martino & Taylor, 2015).

Distribution. The species is so far known only from Singapore.

Figures

Fig. 4. A‒C, Reptadeonella riatanae, new species; A, unbleached autozooids, and avicularia with mandibles in place; B, bleached autozooids with long slit-like spiramina; C, light micrograph showing an ancestrular tetrad (radiating yellow arrows) and a vicarious avicularium (white arrow); D, Reptadeonella cellulanus Tilbrook, Hayward & Gordon, 2001. Scale bars = 0.5 mm (B, D); 0.3 mm (A, C).