Amastigia okinawaensis, Martino & Rosso & Taylor & Chiu & Fujita & Kitamura & Yasuhara, 2025

Amastigia okinawaensis sp. nov. Di Martino, Rosso and Taylor

Figure 9 View FIGURE 9

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Type material. Holotype PMC. B46. 29.7.2024 a, sample 19035 ( Figure 9A–B, E–F View FIGURE 9 ); paratype PMC.

B46. 29.7.2024 b, sample 19065 ( Figure 9C–D View FIGURE 9 ); Core 19, Daidokutsu cave, Okinawa, Japan, Holocene .

Etymology. Referring to the type locality, the Japanese islands of Okinawa where Daidokutsu cave is located.

Diagnosis. Amastigia with biserial branches; club-shaped autozooids arranged in longitudinal alternating series; extensive, smooth gymnocyst proximally; narrow granular cryptocyst outlining the opesia proximally and laterally; opesia oval with 1– 2 inner and 2–3 outer distolateral spines; 0–2 teardrop-shaped avicularia on raised cystids on the gymnocyst, adjacent to opesia, directed proximolaterally inwards but distolaterally outwards in autozooids distal to an ovicell; ovicell globular, ooecium smooth, ectooecium limited to a peripheral band framing the endooecium laterally and distally; vibracula developed longitudinally for the entire length of the zooid. Frontal scuta and gigantic frontal avicularia apparently absent.

Description. Colony erect with relatively narrow (400–475 µm), biserial branches, presumably non-articulated, bifurcations not observed. Autozooids distinct, separated by thin grooves, club-shaped, elongate (mean ZL/ZW 2.12), alternately arranged in two longitudinal series. Gymnocyst smooth, forming an extensive, flat shelf proximally, occupying one-quarter to a half of the frontal surface, accommodating the avicularia; cryptocyst coarsely granular to nodular, narrow, more extensive proximally, tapering laterally, disappearing distally, gradually sloping towards the opesia proximally, steeply sloping laterally; cryptocystal granules 7–10 µm in diameter, arranged in concentric series, more prominent at the periphery. Opesia immersed, oval to pear-shaped, occupying half or more of the frontal surface, with communication pores and muscle scars visible through it; 1–2 inner and 2–3 outer distolateral spines present, indenting the opesial rim, usually with one having a slightly larger diameter than the others, spine diameter at the base 14– 22 µm; frontal scuta absent. Avicularia either absent, single or more commonly paired, placed at the distal margin of the gymnocyst adjacent to the proximal margin of the opesia on raised, columnar cystids, small, teardrop-shaped with acutely triangular rostrum, commonly directed proximolaterally inwards but oriented distolaterally outwards when associated with an autozooid placed distally of an ovicell; crossbar lacking, two blunt condyles present; gigantic frontal avicularia apparently absent. Ovicell hyperstomial, globular, occupying the entire length of the proximal gymnocyst of the distal zooid, often indenting or covering the proximal margin of the opesia; ooecium smooth, imperforate; ectooecium limited to a peripheral band, 22– 34 µm wide, framing the endooecium laterally and distally; proximal margin of the endooecium slightly curved upwards. Dorsal side occupied by two alternating series of Q-shaped (on the left portion of the branch) or P-shaped (on the right portion of the branch) vibracula, extending longitudinally for the entire length of the associated zooid, each with a large (42–66 µm in diameter), circular, radicular pore placed distolaterally.

Measurements (µm). ZL 371±17, 354–408 (2, 9); ZW 175±14, 159–200 (2, 9); OpL 235±10, 221– 252 (2, 10); OpW 157±10, 146–174 (2, 9); CryL 41±7, 32–54 (2, 17); GymL 135±26, 113–196 (2, 17); AvL 65±9, 55–82 (2, 16); AvW 44±6, 39–60 (2, 16); OvL 195±1, 194–195 (1, 2); OvW 190±8, 184– 196 (1, 2); VibrL 413±30, 368–441 (1, 6); VibrW 183±6, 176–193 (1, 6).

Remarks. Three species of Amastigia have been previously reported from the North Pacific: A. rudis (Busk, 1852) , A. biseriata Osburn, 1950 , and A. tricervicornis Gluhak, Lewis and Popijak, 2007 . Vieira et al. (2010) listed A. rudis among Pacific species without scuta, which aligns with the SEM image in Bock (2024) (https://bryozoa.net/cheilostomata/candidae/amastigia _rudis .html). However, in Busk’s (1852, p. 38, pl. 46) original description and illustration of the species, the author depicts autozooids with scuta, as does Osburn (1950, p. 127, pl. 16, figures 3–5). The new species differs by being biserial and lacking the giant frontal avicularia. Additionally, the vibraculum on the back develops longitudinally rather than transversely, following the entire length of the zooid. The absence of scuta seems to be genuine and not the result of preservational issues, as there are no internal attachment structures adjacent to the opesia that would indicate the presence of a scutum. The report of A. rudis throughout the Pacific—from Australia (Busk, 1852) to Japan (Ortmann, 1890) and on the eastern side, including California, Mexico, and Costa Rica (Osburn, 1950)—suggests it might be a complex of species. Amastigia biseriata from California is similar in having autozooids arranged in two alternating longitudinal series but differs by having small lateral avicularia and a single spine on each side (Osburn, 1950, pl. 15, figures 1–3). Amastigia tricervicornis from Taiwan differs by having a single frontal avicularium placed horizontally with a curved upward rostrum (Gluhak et al., 2007, figure 4).