Microporella hastigera ( Busk, 1884 )

Martino, Emanuela Di, Taylor, Paul D. & Gordon, Dennis P., 2020, Erect bifoliate species of Microporella (Bryozoa, Cheilostomata), fossil and modern, European Journal of Taxonomy 678, pp. 1-31 : 8-11

Microporella hastigera ( Busk, 1884)

Figs 4–5 ; Table 3

Flustramorpha hastigera Busk, 1884: 136 , text-fig. 40, pl. 21, figs 7, 7a–c.

Diporula hastigera – Waters 1888: 23, pl. 3, figs 28–29. — Jullien & CalVet 1903: 51, pl. 1, fig. 3, pl. 6, fig. 3. — CalVet in Jullien & CalVet 1903: 129. — CalVet 1907: 407.

Microporella hastigera – CalVet 1931: 87. — d’Hondt 1975: 577 (listed).

Material examined

Lectotype (designated here)

AZORES • Unbleached branch fragment figured by Busk (1884: pl. 21, fig. 7a); near Pico Island; [38°38′ N, 28°28′ W]; depth 450 fms (ca 823 m); HMS Challenger Expedition 1873–1876, St. 75; volcanic mud; NHMUK 1887.12.9.547 ( Fig. 4 ).

Paralectotype (designated here)

AZORES • Bleached branch fragment; same collection data as for lectotype; NHMUK 1887.12.9.549a ( Fig. 5 ).

Description

COLONY. With an encrusting unilaminar and multiserial base, later becoming erect bilaminar, robust branching (adeoniform); branches narrow, 2–3 mm wide with usually 4–5 but up to eight linear series of alternating zooids on each side; interzooidal communication via multiporous septula.

AUTOZOOIDS. Rhomboidal to hexagonal, longer than wide (mean L/W = 1.21). Frontal shield relatiVely flat to moderately conVex, entirely coVered by distinct nodules of Varying shape with 30–35 pseudopores (diameter 5–15 µm) intercalated between them, plus 5–10 round marginal areolar pores, larger than frontal pores (diameter 20–45 µm); except for a single areolar pore distal to aVicularium rostrum, area between proximal margin of the orifice and ascopore field and directly proximally to aVicularium rostrum usually devoid of pores.

PRIMARY ORIfICE. Transversely D-shaped with a straight, distinctly crenulated hingeline; in each corner a short, blunt denticle directed distally; distolateral orificial rim with numerous low rounded and irregularly distributed denticles of variable size; operculum smooth but with a broad and slightly bent transverse depression in the centre; three or four distal oral spines (diameter 15–20 µm); no peristome.

ASCOPORE fIELD. Outlined by a low rim and a narrow, raised band of gymnocystal calcification, located at ca 65 µm from hingeline of the orifice, slightly displaced to the side by the aVicularium and often obliquely aligned; gymnocystal field elliptical, ca 50–60 × 70–80 µm; distal margin with median, subrectangular, projecting tongue leaVing a C-shaped opening, ca 10 × 50 µm, delimited by finely spinose margins.

AVICULARIUM. Single, placed in close proximity of and lateral or proximolateral to ascopore; rostrum directed distolaterally, broadly triangular with an open funnelled tip and thin raised lateral margins, slightly acute to frontal plane; mandible lanceolate, significantly exceeding length of rostrum, ca 230 µm long, abruptly decreasing in width between crossbar and rostrum and slightly widening distal to rostrum before thinning again, the distal third or quarter very narrow and downcurved; proximal and distal opesia semicircular, divided by a straight and thin but deep crossbar.

OVICELLS. Globular, entirely obscuring the orifice; surface densely nodular and with numerous pseudopores seemingly aligned in radial rows, the proximolateral margins joining the proximolateral orifice corners, opening arched aboVe proximal orifice margin, often equipped with a slightly projecting lip.

Remarks

This species was originally recorded from off western and northern Pico Island (Azores, central Atlantic) from depths between 80 and 820 m. During the French Biaçores expedition it was also reported from around the islands of Flores (105–170 m), Graciosa (190–406 m), São Jorge (245 m), Terceira (90– 220 m) and São Miguel (61–550 m), as well as the Formigas Islets south of São Miguel (190–220 m) ( d’Hondt 1975). PreVious records of this species, especially those pre-dating the adVent of scanning electron microscopy (e.g., Calvet (1931) from Cape Verde Islands at 52 m depth), need to be revised.

Figures

Fig. 4. Microporella hastigera (Busk, 1884), lectotype, NHMUK 1887.12.9.547 (unbleached), Recent, Challenger Expedition, St. 75. A. Group of zooids at the branch tip. B. Close-up of autozooids. C–E. Close-ups of the ascopore and adventitious avicularium with the lanceolate mandible either closed (C, E) or open (D). Scale bars: A = 500 µm; B = 200 µm; C–D = 50 µm; E = 100 µm.

Fig. 5. Microporella hastigera (Busk, 1884), paralectotype, NHMUK 1887.12.9.549a (bleached), Recent, Challenger Expedition, St. 75. A. Group of zooids at branch bifurcation. B. Close-up of two ovicellate zooids with coalescent ovicells. C. Close-up of an orifice with four oral spine bases distally, ascopore and avicularium. D. Close-up of the ascopore. E. OVicellate zooid with sealed orifice. F. Closeup of an orifice with three oral spine bases distally. Scale bars: A–B = 400 µm; C = 100 µm; D = 40 µm; E = 200 µm; F = 50 µm.