Adeonella assegai, Boonzaaier-Davids & Florence & Gibbons, 2020

Boonzaaier-Davids, Melissa K., Florence, Wayne K. & Gibbons, Mark J., 2020, Novel taxa of Cheilostomata Bryozoa discovered in the historical backlogs of the Iziko South African Museum, Zootaxa 4820 (1), pp. 105-133 : 118-120

Adeonella assegai n. sp.

( Fig. 7 A–E, Table 6)

zoobank.org/ 8F29F3F4-B3B9-4D83-BA31-DD65E8779508

Material examined. Holotype: SAMC-A 028960 (dry), station AFR273 A31650 (34°55’54”S, 23°17’7”E), off Knysna, South Coast, South Africa, Africana South Coast Demersal Survey, trawl, depth 211 m, 2 May 2011. Additional comparative material: Adeonella circumspecta , SAMC-A 026913 (paratype), Port Natal (29°51’01.2”S, 31°03’09.7”E), Durban, East Coast, South Africa, no additional information. Adeonella confusanea , SAMCA026439 (holotype), station SM 185 (33°39.3’S, 27°11.6’E), off Port Alfred, Southeast Coast, South Africa, RV Meiring Naude Survey, dredge, depth 90 m, 31 May 1978. Adeonella conspicua , SAMC-A 026440 (holotype), station SM 179 (33°30.3’S, 27°22.1’E), off Great Fish River Mouth, Southeast Coast, South Africa, dredge, depth 80 m, 29 May 1978. Adeonella coralliformis , SAMC-A 026316, no additional information; NHMUK 1923.7.26.13 (pt of type), Cape Province, South Coast, South Africa, O’Donoghue Collection, no additional information. Adeonella cracens , SAMC-A 026312 (holotype), station SM 86 (27°59.5’S, 32°40.8’E), St. Lucia MPA, East Coast, South Africa, RV Meiring Naude Survey, heavy dredge, depth 550 m, 22 May 1975. Adeonella falcicula, NHMUK 1983.8.2.2, John Murray station 105B (5°34’37’’S, 39°14’06’’E– 5°37’00’’S, 39°14’36’’E), Zanzibar, Mozambique, depth 238 m, 11 January 1934. Adeonella gibba , SAMC-A 026444 (holotype), station SM 179 (33°30.3’S, 27°22.1’E), off Great Fish River Mouth, Southeast Coast, South Africa, dredge, depth 80 m, 29 May 1978. Adeonella ligulata, NHMUK 1923.7.26.16 (pt of type), Green Point, West Coast, South Africa, no additional information; NHMUK 7.26.16 (pt of type), same locality as above. Adeonella lobata , SAMC-A 026917 (paratype), Port Elizabeth (33°55’00.2”S, 25°39’08.4”E), Southeast Coast, South Africa, no additional information. Adeonella pluscula , SAMC-A 026912 (paratype), Whittle Rock (34°15’S, 18°33’E), False Bay, South Coast, South Africa, depth 30 m, no additional information. Adeonella purpurea , SAMC-A 026911 (paratype), Vulcan Rock (34°04’S, 18°18’E), West of Cape Peninsula, South Africa, depth 25 m, no additional information. Adeonella tuberosa , SAMC-A 026910 (paratype), Hangklip Berg (34°29’54.5”S, 18°38’48.9”E), Agulhas Bank, South Coast, South Africa, depth 133.5 m, no additional information.

Etymology. ‘ Assegai ’ is a term used by the Victorian British settlers, indicating a pole weapon with iron tip used for throwing by isiZulu and Nguni tribes of southern Africa. The shape of the iron tip resembles the slender colony morphology of this species. Used as a name in apposition.

Diagnosis. Colony erect, bilaminar. Autozooids with granular and densely pseudoporous frontal shield. Primary orifice wider than long with no condyles; secondary orifice circular. Circular spiramen immediately proximally to the secondary orifice. Adventitious avicularia paired, triangular, proximolateral to spiramen. Vicarious avicularia triangular, less frequent. Brooding dimorphic zooids present at branch edges.

Description. Colonies developing from narrow cylindrical bases (about 1 mm wide) to form slender, flat, straight to slightly curved, sabre-like structures, up to 3 mm wide; longest branch 42 mm, showing no evidence of branching/bifurcations. Autozooids oval or hexagonal at growing edge, elongated and irregular in outline in later ontogeny, about 0.77 mm long by 0.37 mm wide; frontal shield finely granular and densely punctured by small pseudopores. Primary orifice wider than long, no visible condyles; secondary orifice circular. Spiramen circular, situated immediately proximal to secondary orifice. Adventitious avicularia typically paired, arising proximolateral to spiramen, directed mostly distally, variably orientated in later ontogeny; mandibles acutely triangular. Branch edges composed of single linear series of dimorphic brooding zooids, elongate and rectangular, about 0.79 mm long by 0.41 mm wide (N T = 3), distally rounded and proximally concave; orbicular to semicircular secondary orifice; typically paired adventitious avicularia, lateral to spiramen, directed distally or obliquely towards peristome corners. Branch edges may occasionally bear kenozooids with vicarious avicularia; mandible acutely triangular, distally raised.

Remarks. Adeonella is a species-rich genus including 51 extant and fossil species (www.bryozoa.net, accessed 06 June 2020). A comprehensive review of extant Adeonella species ( Hayward 1988), along with subsequent publications ( Amui 2005; Rosso & Novosel 2010), indicate that 44 species are distributed throughout the Indo-West Pacific realm, the Mediterranean and South Atlantic Ocean. About sixty percent of extant adeonellids occur in South Africa, with the highest diversity of Adeonella species occurring along the East Coast ( Hayward 1988). However, a recent genetic analysis indicates that the genus is polyphyletic and in urgent need of revision ( Orr et al. 2019).

Adeonella cultrata Hayward, 1981 and A. falcicula Hayward, 1981 are the only known species with slender, sabre-like branches. No material of these two species is housed at SAMC, but the holotypes are at the Zoological Museum of University of Copenhagen in Denmark and some material of A. falcicula at the NHMUK. Images of A. falcicula were obtained from Ms Mary Spencer-Jones (NHMUK) for comparison, while material of A. cultrata was unattainable.

Adeonella falcicula resembles A. assegai n. sp. in having slender colonies (up to 45 mm long and maximum width of 3 mm) that form from a cylindrical encrusting base ( Hayward 1981). However, the new species differs from A. falcicula in the shape of autozooids, orifice and spiramen, in having occasionally marginal vicarious avicularia and in the absence of an additional pair of distally situated adventitious avicularia in marginal autozooids.

Additionally, A. falcicula has larger autozooids, about 0.98 ± 0.11 mm long (N T = 50) ( Hayward 1981, p. 45), compared to about 0.77 ± 0.16 mm long (N T = 15) in A. assegai n. sp. (see also Table 6).

Adeonella cultrata resembles the new species in the zooidal shape, but has larger autozooids about 0.81 ± 0.14 mm long (N T = 20) ( Hayward 1981, p. 46). Additionally, A. cultrata has a large, oval spiramen, a semicircular or oval secondary orifice, very rarely paired adventitious avicularia and only marginal vicarious avicularia, characteristics not shared by A. assegai n. sp.

Two colonies of A. assegai n. sp. were attached to hydroids collected at one station at a depth of 211 m. The new species is only known from South Africa, off Knysna on the South Coast .

Figures

FIGURE 7. A–E. Adeonella assegai n. sp. (SAMC-A028960) A. Autozooids at the growing edge (scale bar = 0.2 mm, magnified x75). B. Frontal view of autozooids near the margin (scale bar = 0.2 mm, magnified x75). C. Close-up of two zooids (scale bar = 0.2 mm, magnified x100). D. Close-up of the secondary orifice, paired frontal avicularia and spiramen (scale bar = 0.1 mm, magnified x200). E. Dimorphic brooding zooids at the branch margin (scale bar = 0.4 mm, magnified x50).