Parasmittina winstonae Liu et al., 2001

Taylor, Paul D. & Tan, Shau-Hwai Aileen, 2015, Cheilostome Bryozoa from Penang and Langkawi, Malaysia, European Journal of Taxonomy 149, pp. 1-34 : 19-21

Parasmittina winstonae Liu et al., 2001

Fig. 11 A–L

Parasmittina winstonae Liu et al., 2001: 623 , pl. 55, figs 1–7.

Parasmittina winstonae – Tilbrook 2006: 156, pl. 29b, 30d–e.

Material

MALAYSIA: MSL BRY018, Kuah jetty, Langkawi, several colonies encrusting bivalves growing on a rope hanging from jetty. MSL BRY019a, Kuah jetty, Langkawi, encrusting barnacles and bivalve growing on a rope hanging from jetty. MSL BRY020a, BRY021a, Pulau Betong, Penang, encrusting barnacles from oyster rafts.

Description

Colony encrusting, multiserial, unilamellar; growing edge developing giant buds ( Fig. 11J ). Ancestrula tatiform ( Fig. 11C ), about 0.22 mm long by 0.17 mm wide, with subcircular opesia 0.16 mm long by 0.14 mm wide surrounded by 9 spines, becoming overgrown in older colonies; periancestrular zooids numbering 5 or 6, 0.26–0.32 mm long by 0.22–0.30 mm wide, some bearing adventitious avicularia, calcification of their frontal shields extending as short lobes between oral spines of ancestrula ( Fig. 11D ). Autozooids subhexagonal, distally rounded, 0.32–0.45 mm long by 0.22–0.33 mm wide; boundary walls salient with a fine fissure; frontal shield gently convex, coarsely pustulose, about 15–20 marginal areolar pores separated by ridges, areolae impinging on central part of shield in older zooids ( Fig. 11H ), no pseudopores; primary orifice egg-shaped to rounded rectangular, 0.10–0.11 mm long by 0.10 mm wide, large relative to zooid size, lappets developed distolaterally, lyrula narrow, 17–20 μm high by 25–37 μm wide at top edge, condyles present about one-third distance along orifice, 15 μm high, medioproximal edge serrated ( Fig. 11K ); oral spine bases usually numbering two, occasionally one or lacking; ovicell hyperstomial ( Fig. 11 H–I), broader than long, 0.13–0.16 mm long by 0.18 mm wide, containing 25–40 pores with raised rims, variable in size, circular, elliptical or dumbbell-shaped, margins overgrown by cryptocystal calcification. Avicularia adventitious, of three types: small acuminate, small plectrum-shaped, and giant. Small acuminate avicularia variously located ( Fig. 11G, I ), increasing in number during ontogeny, usually directed distally or distolaterally to laterally and towards midline of zooid, occasionally proximolaterally, about 0.09–0.12 mm long by 0.05–0.06 mm wide; rostrum acuminate, a high triangle, shallow rostral shelf; cross-bar calcified, straight or slightly concave; opesia semicircular. Small plectrum-shaped avicularia located laterally or distolaterally of orifice ( Fig. 11K ), occasionally in more proximal positions around perimeter of autozooid, directed and inclined outwardly, narrow proximally, broadening distally, about 0.05–0.06 mm long by 0.05–0.08 mm wide (measured in plane of colony surface); rostrum rounded trapezoidal, shallow rostral shelf; cross-bar completely or incompletely calcified, straight; opesia semicircular, small. Giant avicularia occasionally present ( Fig. 11F ), directed distally, originating proximolaterally and passing laterally of orifice, which may be torqued, extending over frontal shield of distal zooid, straight or curved towards autozooid midline, 0.35–0.40 mm long by 0.11–0.13 mm wide; rostrum spatulate, long, with a deep shelf occupying onethird to two-thirds of length; cross-bar slightly concave; opesia semicircular.

Remarks

Parasmittina is a very diverse genus with a global distribution. Different species are best characterised by their avicularia, which are often of more than one morph within a single colony. First described formally from South China ( Liu et al. 2001), Parasmittina winstonae has three kinds of avicularia: small acuminate, small plectrum-shaped, and giant. The distally directed giant avicularia in P. winstonae ( Fig. 11F ) are very unusual, as giant avicularia in Parasmittina are normally directed proximally, for example in the numerous species described by Soule & Soule (1973), Hayward & Parker (1994) and Harmelin et al. (2009). Harmer (1957: 943) noted the rarity of distally directed giant avicularia when describing material, some from Malaysia and since assigned to P. winstonae by Liu et al. (2001: 802), as Smittina parsevalii (Audouin, 1826) . Likewise, the small plectrum-shaped avicularia lateral to the orifice are highly unusual, if not unique, to P. winstonae within Parasmittina .

Liu et al. ’s (2001) original description of this species from the South China Sea gives a slightly longer autozooid size (0.37–0.67 mm) than both the Malaysian material described here (0.32–0.45 mm) and specimens from the Solomon Islands (c. 0.45 mm) described by Tilbrook (2006), who did not mention the presence of plectrum-shaped avicularia. This leaves some doubt about whether the three occurrences are truly conspecific, which will require further studies to test.

Figures

Fig. 11. Parasmittina winstonae Liu et al., 2001. — A–I. Kuah jetty, Langkawi, MSL BRY018. A. Small colony. B. Tiny colony on same substrate. C. Ancestrula of colony shown in B (note that the prism is from a disaggregated bivalve shell). D. Early stages of another colony showing five budded autozooids surrounding the ancestrula. E. Group of zooids. F. Giant avicularium with small plectrum-shaped adventitious avicularium at right proximolateral corner. G. Young autozooids and small adventitious avicularia. H. Older autozooids and adventitious avicularia. I. Ovicell. — J. MSL BRY019a, same locality details; oblique view of growing edge with giant bud. — K–L. Pulau Betong, Penang. K. MSL BRY020a. Slightly oblique view of orifice showing oral spine bases, condyles and lyrula, with plectrumshaped adventitious avicularia distolaterally. L. MSL BRY021a. Old part of colony with numerous avicularia. Scale bars: A = 1 mm; B, J = 500 μm; C, F–G, I, K = 100 μm; D–E, H, L = 200 μm.