Adeonellopsis periculosa, Liow & Gordon, 2020

Liow, Lee Hsiang & Gordon, Dennis P., 2020, New species of Adeonellopsis (Bryozoa: Adeonidae) from southern Zealandia and the western Tasman Sea, Zootaxa 4895 (3), pp. 301-331 : 316-319

Adeonellopsis periculosa n. sp.

( Figs 3D , 11 , 12 ; Tables 1, 2)

Etymology. Latin periculosus, dangerous, alluding to the large, presumably defensive, vicarious avicularia.

Material examined. Holotype: Australian Museum U. 5796, Stn I89, 29.4217° S, 168.0033° E, Norfolk Ridge , 65 m . Paratypes: Australian Museum U. 5797, same data as holotype . NIWA 144897 , 146072 , same data as holotype .

Diagnosis. Branches flattened or, more generally, slightly curled, 2.5–4.5 mm wide. Autozooids averaging 454 μm long, 241 μm wide. Autozooidal spiramen mostly with 3 pores. Large suboral adventitious avicularium on every zooid, including gonozooids, its elevated distal tip often projecting above proximal orificial rim. One or two additional smaller such avicularia may occur at proximal end of zooid. Vicarious avicularia at intervals on or adjacent to colony margins and proximal to branch bifurcations. All avicularia with open-channelled acute rostral tip. Gonozooids large, with dimorphic orifices and vestigial ooecia (visible during gonozooidal ontogeny); spiramen like that of autozooids but larger, with 4–6 pores.

Description. Mature intact colony not seen; largest fragment (holotype) 20 mm high, 21 mm broad, repeatedly bifurcating every 4–4.8 mm, even trifurcating, turned back on itself, with curled branches and branch fusions. Dried colour pale grey; residual patches of pigment on some zooids indicate purplish coloration in life. Branch diameters varying with age of colony from 2.2 to 4.5 mm. Autozooids arranged in quincunx; 8–10 longitudinal series across width of branch ( Fig. 11A ).

Neanic autozooids ( Fig. 11B ) more or less subhexagonal, becoming more elongate-rectangular with ageing and secondary calcification. Interzooidal boundaries indicated by thin lines of calcification in interzooidal furrows, which are bordered by 17–21 areolar pores in a series around the entire zooidal margin; a few additional areolar pores closer to orifice and suboral avicularium; marginal areolae sometimes merging as zooids acquire additional calcification. Average zooid length and width 454 μm and 241 μm, respectively.

Autozooidal peristomial orifice transversely D-shaped to subrounded, becoming sunken within distally cowled deepening peristome as zooids age. Interior view of orifice shows a pair of blunt condyles, one in each proximolateral corner. Multiporous spiramen ( Fig. 12A ) in frontal depression, central in zooid or in proximal half but position can vary; mean length 63 μm, mean width 50 μm; spiraminal pores 2–5, mostly 3, varying a little in size and shape, each with 6–8 spokes, only some of which may touch. Spiramen becoming deeply sunken and somewhat concealed as frontal shield thickens and the frontal opening reduces in diameter.

Adventitious avicularia ( Fig. 11B, D ) varying in size, position and orientation but all having same form, i.e. elongate-triangular rostrum with open-channelled acute tip and smooth raised (gymnocystal) margins, common rostral-opesial foramen, semicircular opesial margin, granular crescentic cryptocyst; no pivot bar but short curved pivot ridges at rostral-opesial transition; cryptocyst smooth. Suboral avicularium moderately large, the rostrum elevated obliquely frontalwards, directed mid-distally, its tip often projecting above the orifice margin. One or two additional similar avicularia laterally or midproximally in many ephebic zooids, pointing in any direction.

Vicarious avicularia ( Figs 11A ; 12 B–D) at intervals on or adjacent to colony margins and proximal to branch bifurcations.All avicularia with open-channelled acute rostral tip and groove ( Fig. 11D, E ), the rostral rims frontally arcuate in profile.

Gonozooids ( Figs 11 A–C; 12B) large, showing vestigial ooecia during gonozooidal ontogeny; orifice averaging 405 μm wide. Spiramen ( Fig. 11C ) like that of autozooids but larger, with 4–6 pores having spokes that may or may not touch.

Ancestrula and early astogeny not seen.

Remarks. Adeonellopsis periculosa n. sp. has a very similar colony form to that illustrated for the shallow coastal Victorian species Adeonellopsis parvipunctata MacGillivray, 1886 , which apparently has, however, only a single, spoked spiraminal pore in autozooids and small latero-oral avicularia. Adeonellopsis sparassis ( Ortmann, 1890) , apparently endemic to Japan, is also very similar, but differs in having larger mean autozooid size, vicarious avicularia confined to branch margins and gonozooids with 8–10 spiraminal pores ( Hirose 2016). The number of spiraminal pores in the gonozooid of A. periculosa n. sp. is the fewest (4–6) of any of the new species described herein ( Table 2).

Distribution. Norfolk Ridge south of Norfolk Island (Australian Exclusive Economic Zone), 65 m.

Figures

FIGURE 3. A, B. Adeonellopsis macewindui n. sp.: A. Holotype, NIWA 146070; B. NIWA 146098. C. Adeonellopsis tasmanensis n. sp., composite of three fragments, all NIWA 144892. D. Adeonellopsis periculosa n. sp., holotype, NIWA 146071. E. Adeonellopsis wassi n. sp., composite of three fragments, all NIWA 144898. F, G. Adeonellopsis gemina n. sp.: F. holotype, NIWA 146095; G. Two specimens, NIWA 146073. H. Adeonellopsis minor n. sp., composite of four fragments, NIWA 146152. I. Adeonellopsis gracilis n. sp., composite of two fragments, holotype (larger specimen), NIWA 92745; smaller specimen (separated by thin gap), NIWA 146099. Specimens A–I at same scale; scalebar 5 cm.

FIGURE 11. Adeonellopsis periculosa n. sp. (NIWA 146072): A. Part of stem showing incipient and developed branch bifurcations (arrows); note the disposition of axial and marginal vicarious avicularia and gonozooids. B. Two gonozooids at different developmental stages, with adjacent autozooids. C. Incompletely formed gonozooid shown in B before the vestigial ooecium (vo) is concealed by the completed distal rim of the peristome. D. Ephebic autozooids with accessory adventitious avicularia proximally, sunken spiramina and narrower peristomial orifices. Scalebars: A, 2 mm; B, 500 μm; C, 100 μm; D, 300 μm.

FIGURE 12. Adeonellopsis periculosa n. sp. (NIWA 146072): A. Autozooidal spiramen. B. Ephebic gonozooids and autozooids (with vicarious avicularium), in which spiramina are becoming sunken in secondary calcification. C. Vicarious avicularia on branch margin. D. vicarious avicularium showing deep distal groove and open rostral tip for accommodating curved mandible tip. E. Close-up of groove and rostral tip in D. Scalebars: A, 50 μm; B, 500 μm: C, 400 μm; D, 100 μm; E, 20 μm.