Jessethoa ausubeli, Gordon, 2020

Gordon, Dennis P., 2020, New Hippothoidae (Bryozoa) from Australasia, Zootaxa 4750 (4), pp. 451-476 : 461-464

Jessethoa ausubeli n. sp.

( Figs 6 C–J; 7A–E)

Etymology. As above, honorific for Jesse H. Ausubel.

Material examined. Holotype: NIWA 132852, Stn Z9692, 34.3782° S, 172.8842° E, 52 m, 27 January 1999 on a species of Poirieria (Muricidae) . Paratype: NIWA 127695, same data as holotype, on a species of Pelicaria (Struthiolariidae) ; NIWA 132853, on a species of Amalda (Olividae) , 132854 (molluscan substratum indeterminate), Stn Z9711, 34.3208° S, 172.8687° E, 69 m, 29 January 1999. Other material: NIWA 132855, Stn Z9676, 34.3643° S, 172.8412° E, 57 m, 25 January 1999, on a species of Phenatoma (Turridae) . All samples collected by F. V. Ben Gunn NE of Spirits Bay, North Island, New Zealand.

Description. Colony encrusting, uniserial, initially open-branching and extensively ramifying, zooids becoming densely crowded and contiguous in mature state; maximum colony length or diameter c. 25 mm.

Autozooids initially all elongate-oval ( Fig. 6 C–E), becoming more clavate with reasonably stout non-filiform cauda ( Fig. 6H ), widest and highest in centre of dilatation, no carina. Typically 4–5 oval pore-chamber openings just inside lateral margins, facing frontally, variable in size, generally larger on dilatation. A few sparse gymnocystal pores more frontally spaced in gymnocyst. Zooids distal of ancestrula initially in linear uniserial chain before each zooid starts budding laterally from largest pore-chambers, one on each margin subjacent to orificial sinus, at right angles to axis of parent autozooid. At intermediate colony sizes autozooids becoming more variable in shape, ranging from more elongate, to more oval and less caudate, depending on availability of space for growth, in both cases having more pore-chamber openings (6–8 along each lateral margin), some of these relatively larger than the others, and second row of smaller pseudopores in an arc distal to the orifice. Autozooids leaving excavation in calcareous substratum. ZL 384±60, 274–482 (15); ZW 75±10, 61–89 (15).

Orifice longer than wide; anter evenly rounded, 2/3 length of entire orifice; sinus a wide, deep U shape about 1/3 orifice length ( Fig. 6I ), with small, rounded condyles at junction of anter and poster, pointing downwards. Operculum relatively thick. OL 75±8, 61–89 (15); OW 58±10, 40–80 (15).

Female zooids same size as autozooids, bearing relatively large ovicells ( Figs 6J ; 7C ). Ovicell prominent, terminal, cleithral; ooecium formed by distal kenozooid. Ooecium and female zooid each with relatively large number of pseudopores (up to 40 in ooecium); large pore-chamber openings tend to occur around periphery of ooecial kenozooid, constituting loci where interzooidal communications may be established with other zooidal elements in crowded colonies. Dimorphic combined maternal aperture larger than autozooidal orifice, near-circular; proximal corners of ooecium encroaching over opening, giving false impression of broad sinus ( Fig. 7B ). ♀ ZL 461±55, 361–525 (8); ♀ ZW 226±35, 175–275 (8); OoL 219±42, 157–283 (9); OoW 235±31, 191–268 (9); ♀ OrL 76±3, 71–81 (10); ♀ OrW 87±4, 79–95 (10).

Zooeciules developing once colony ramification underway; initially budded laterally in lieu of an autozooid, later, in mature reproducing colonies, becoming abundant and developing mid-distally from autozooids and female zooids, even forming linear chains of successive elongate zooeciules ( Fig. 7E ), all with frontolateral pseudopores (2–6 along each side), and many connecting with pore-chamber openings of adjacent autozooids, zooeciules, female zooids and ooecia. In mature crowded parts of colonies a zooeciule can develop mid-frontally on an autozooid ( Fig. 7A ), budded from one or a pair of frontal gymnocystal pores; these frontal zooeciules longitudinally elongate and linear (if from single pore) or wider and more oval (if from 2 pores). Each zooeciule having very small oval subterminal aperture (if elongate) or midfrontal aperture (if oval), aperture with tiny condyles near its midlength, with articulating operculum ( Fig. 7A ). Some small, constricted zooeciules in crowded parts of colonies (secondarily?) lacking aperture ( Fig. 7B ). Damaged frontal zooeciules can regenerate without forming aperture, their frontals with many pseudopores. One zooid with regenerated frontal zooeciule had a total of 33 pseudopores over entire frontalshield area, including in zooeciule. ZoL 221±92, 121–397 (15); ZoW 111±28, 62–182 (15); ZoOL 22±2, 20–27 (7); ZoOW 19±2, 17–22 (7); FZoL 118±25, 83–156 (8); FZoW 76±40, 34–159 (8); FZoOL 20±4, 16–25 (4); FZoOW 20±3, 15–24 (4).

Ancestrula like autozooid, sinusoid with frontal shield. Two forms seen, one oval, not budding proximally ( Fig. 6E, F ); second form elongate-oval, non-clavate, but bipolar, budding proximally as well as distally ( Figs 6D, G ; 7D ); in both cases having distolateral pair of pseudopores closer to orifice than in later zooids and frontal gymnocyst more fibrous. AnL 276±24, 260–303 (3); AnW 141±18, 121–158 (3).

Remarks. Whereas neanic colonies consist of mostly uniserial branching runners, ephebic colony parts can be so dense and irregular, with adventitiously budded female zooids and zooeciules as to appear almost celleporiform ( Fig. 6J ). The density of pseudopores in ooecia and frontal shields of female zooids is also exceptional among hippothoids.

Distribution. Endemic; known only from northeast of Spirits Bay, Northland, New Zealand, 52–69 m depth, on gastropod shells.

Figures

FIGURE 6. Neothoa bilderbacki n. sp., NIWA 132850 (holotype): A, B, en face views of autozooidal and ovicellate (dimorphic) orifices, respectively, tilted to show maximum lengths. Jessethoa ausubeli n. gen., n. sp., C–H (NIWA 132855), I, J (NIWA 132854, paratype): C, autozooids and zooeciules from proximal part of colony; D, elongate-oval ancestrula (middle zooid) with bipolar budding; E, oval ancestrula (at proximal end) with unipolar budding distalwards; F, close-up of ancestrula in E; G, another ancestrulate colony with bipolar budding (ancestrula lower middle); H, autozooids with frontal and laterally budded zooeciules; I, autozooidal orifice; J, zooids, mostly ovicellate, from crowded part of colony with frontal budding. Substratum darkened in D, E, H to show zooid outlines more clearly. Scalebars: A, B, 50 μm; C, D, 300 μm; E, J, 500 μm; F, 200 μm; H, 400 μm; I, 30 μm.

FIGURE 7. Jessethoa ausubeli n. gen., n. sp., A, D (NIWA 132855), B, C, E (NIWA 132854, paratype): A, operculate autozooid with frontal zooeciule, also operculate; B, varied zooid types in crowded part of colony; notice circular primary orifice of female zooid beneath broken ooecium; C, ovicellate zooid; note the density of pseudopores in both the female frontal shield and the ooecium; D, closeup of bipolar ancestrula in fig. 6G; E, sequential budding of elongate zooeciules [the dark lines with two zooid openings pertain to the ctenostome bryozoan Immergentia zelandica Silén, 1946]. Scalebars: A, C, D, 100 μm; B, 300 μm; E, 500 μm.