Chamberlainium occidentale Puckree-Padua, P.W. Gabrielson et Maneveldt, 2021

Puckree-Padua, Courtney A., Gabrielson, Paul W. & Maneveldt, Gavin W., 2021, DNA sequencing reveals three new species of Chamberlainium (Corallinales, Rhodophyta) from South Africa, all formerly passing under Spongites yendoi, Botanica Marina (Warsaw, Poland) 64 (1), pp. 19-40 : 30-34

Chamberlainium occidentale Puckree-Padua, P.W. Gabrielson et Maneveldt sp. nov. ( Figures 6 , 31–35 , 36–41 , 42–46 ; Tables 1, 2).

Holotype: L 3986120 , 01.x.2015, leg. G. W. Maneveldt and C. A. Puckree-Padua, collection number 15/61 B, epilithic on primary bedrock in low intertidal zone.

Isotypes: UWC 15 /58, UWC 15 /59, UWC 15 /61 A

Type locality: South Africa, Western Cape Province, Lamberts Bay (32°6.5728′ S, 18°18.1270′ E) .

Etymology: ‘ occidentale ’ from ‘ occidentalis ’, meaning western ( Stearn 1973), making reference to the species’ widespread distribution along the west coast of Southern Africa.

Description: Non-geniculate, thalli are variably thin to thick (up to 1000 µm), encrusting (smooth) to warty (mostly) to lumpy, becoming only slightly protuberant. Thalli are epilithic to epizoic and brownish beige in well-lit conditions. Individual crusts do not appear to coalesce (do not fuse together) and are easily discernible. The thallus construction is monomerous with a single layer of epithallial cells. A central columella is present in tetrasporangial conceptacles, which persists to maturity. The pore opening in mature tetrasporangial conceptacles is unoccluded and slightly sunken below the surrounding roof surface. The psb A (851 bp) and rbc L (691–1,384 bp) sequences are diagnostic.

Habitat: Thalli were epilithic on the primary bedrock in the high, mid- and low intertidal zones and epizoic on mollusc shells in the low intertidal zone.

Vegetative morphology and anatomy: Plants were non-geniculate, thalli were variably thin to thick (up to 1000 μ m), encrusting (smooth) to warty (mostly) to lumpy, becoming only slightly protuberant (protuberances 4 mm in height) ( Figures 6 , 31 ). Thalli were firmly adherent, brownish beige (in well-lit conditions) ( Figures 6 ) to bluegray to rosy pink (in dim light) when freshly collected. Individual crusts did not coalesce (did not fuse together) and were easily discernible ( Figure 31 ).

Thalli were dorsiventrally organized, monomerous and haustoria were absent. The medulla was thin and plumose (non-coaxial) ( Figures 32, 33 ). Medullary filaments comprised square to elongate cells, which gave rise to cortical filaments that comprised square to rectangular cells ( Figures 33, 34 ). Contiguous medullary and cortical filaments were joined by cell fusions; secondary pit connections were absent ( Figures 33, 34 ). Subepithallial initials were square to rectangular ( Figure 35 ). The epithallus was single layered with elliptical to round to elongate cells ( Figure 35 ). Trichocytes were common, mostly singularly, but also in clusters of up to 6 cells, separated by normal vegetative filaments ( Figure 35 ). Trichocytes were always terminal and never intercalary in the cortex; buried trichocytes were not observed. Data on morphological and measured vegetative characters are summarized in Table 1.

Reproductive morphology and anatomy: Gametangial thalli were dioecious and monoecious. The type specimen bore all (including tetrasporangial) life cycle stages.

Spermatangial (male) conceptacles were uniporate, low-domed, and raised above surrounding thallus surface ( Figures 36, 37 ). Conceptacle chambers were transversely elliptical to flatten and the roof nearly twice as thick along the pore canal ( Figures 37, 38 ). The roof was formed from filaments peripheral to the fertile area ( Figure 36 ). Throughout the early development, a protective layer of epithallial cells surrounded the conceptacle primordium ( Figure 36 ). This protective layer was shed once the pore canal was near fully developed. The pore opening was occluded by a mucilage plug ( Figure 37 ). In mature conceptacles terminal initials along the pore canal were enlarged and papillate, they projected into the pore canal and were orientated more or less parallel to the conceptacle roof surface ( Figure 38 ). Unbranched (simple) spermatangial systems were confined to the floor of the mature conceptacle ( Figures 36, 37 ). Senescent male conceptacles appeared to be shed as no buried conceptacles were observed.

Carpogonial (female) conceptacles were similar in size and shape to spermatangial conceptacles and were raised above surrounding thallus surface ( Figure 39 ). In mature conceptacles the terminal initials along the pore canal were enlarged and papillate, they projected into the pore canal and were orientated more or less parallel or nearly perpendicular to the conceptacle roof surface ( Figure 39 ). Carpogonial branches developed across the floor of the conceptacle chamber, comprising a single support cell, a hypogynous cell and a carpogonium that extended into a trichogyne ( Figure 39 ). Sterile cells were occasionally present on hypogynous cells ( Figure 39 ).

After presumed karyogamy, carposporophytes developed within female conceptacles and formed carposporangial conceptacles ( Figure 40 ). Carposporangial conceptacles were comparatively large, low-domed, and raised above the surrounding thallus surface. Conceptacle chambers were transversely elliptical with flattened bottoms presumably caused by the growth of the gonimoblast filaments. Pore canals tapered towards the surface, were lined by enlarged papillate cells that projected into the pore canal and were orientated more or less parallel to the conceptacle roof surface ( Figure 40 ). In mature conceptacles, the cells lining the pore canal were more elongate than their inward derivatives. The base of the pore canal was sunken into the chamber and terminal initials near the base characteristically pointed downward ( Figure 40 ). A discontinuous central fusion cell was present and 5–7 celled gonimoblast filaments (including a terminal carposporangium) developed along the periphery of the conceptacle chamber ( Figures 40, 41 ). The remains of unfertilized carpogonia persisted across the dorsal surface of the fusion cell ( Figures 40, 41 ). Senescent carposporangial conceptacles appeared to be shed as no buried conceptacles were observed.

Tetrasporangial thalli are morphologically similar to gametangial thalli. Conceptacles were uniporate, low domed and raised above the surrounding thallus surface ( Figures 42–45 ). Conceptacle chambers were transversely elliptical to bean-shaped. The roof was nearly twice as thick along the pore canal and was 5–7 cells (including an epithallial cell) thick. The pore canal tapered towards the surface an was arched ( Figure 46 ). The pore canal was lined by elongated papillate cells that projected into the pore canal and were orientated more or less parallel or nearly perpendicular to the conceptacle roof surface ( Figure 46 ). The roof was formed from filaments peripheral to the fertile area and terminal initials were more elongate than their inward derivatives ( Figures 42–44 ). Throughout the early development a protective layer of epithallial cells surrounded the conceptacle primordium ( Figures 42–44 ). This protective layer was shed once the pore canal was near fully developed. The pore opening was unoccluded and became slightly sunken below the surrounding roof surface ( Figures 45, 46 ). Throughout development of the immature tetrasporangial conceptacle a prominent columella of sterile filaments formed at the center of the conceptacle chamber ( Figures 43, 44 ), which persisted to maturity ( Figure 45 ). The base of the pore canal was sunken into the chamber and terminal initials near the base point downward ( Figure 46 ). Mature conceptacle floors were sunken 14–19 cells (including the epithallial cell) below the surrounding thallus surface. Zonately divided tetrasporangia at maturity were arranged at the extreme periphery of the conceptacle chamber and were attached via a stalk cell ( Figure 45 ). Senescent tetrasporangial conceptacles appeared to be shed as no buried conceptacles were observed. Data on reproductive characters summarized in Table 2.

Distribution: Confirmed by DNA sequences to be widely distributed (± 1,200 km distance) along the west and southern west coasts, occurring from Lüderitz ( Namibia) to Holbaaipunt (Western Cape Province), South Africa. The species is disjunct in the southern part of its range of ± 240 km.

Figures

Figures 4–6: Habit photographs of ChamberlainiUm capenSe, C. gleboSUm and C. occidentale. (4) ChamberlainiUm capenSe is moderately thick to mostly lumpy and only slightly protuberant. Scale bar = 20 mm. (5) ChamberlainiUm gleboSUm is thick, very lumpy and highly protuberant. Scale bar = 20 mm. (6) ChamberlainiUm occidentale is morphologically highly variable, occurring as thin encrusting (smooth) to thick warty (mostly) to lumpy plants, and are only slightly protuberant. Scale bar = 30 mm.

Figures 31–35: ChamberlainiUm occidentale habit and vegetative anatomy. (31) Rock fragment with holotype specimen showing the region (white arrow) of the holotype from which all analyses were done (L 3986120, gametangial and tetrasporangial). Scale bar = 10 mm. (32) Vertical section through the margin (black arrow) showing the monomerous thallus construction with plumose medulla (M) giving rise to cortical filaments (C) that terminate in a single layer of epithallial cells (black arrowhead) (UWC 15/59). Scale bar = 50 μm. (33) Vertical section of the inner thallus showing cell fusions (f) between adjacent medullary filaments (UWC 15/56). Scale bar = 20 μm. (34) Vertical section of the outer thallus showing a single layer of epithallial cells (e) subtended by a layer of subepithallial initials (i). Note the cell fusions (f) between adjacent cortical filaments (UWC 15/59). Scale bar = 20 μm. (35) Vertical section of the outer thallus showing a single layer of epithallial cells (e) subtended by a layer of subepithallial initials (i). Note a cluster of bottle-shaped trichocytes (t) each separated by vegetative filaments (UWC 15/59). Scale bar = 20 μm.

Figures 36–41: ChamberlainiUm occidentale gametangial anatomy. (36) Vertical section through the outer thallusshowing a spermatangial conceptacle primordium with peripheral roof development (black arrows) and simple spermatangial systems (black arrowheads) confined to the conceptacle floor. Note the protective layer of epithallial cells (white arrow) (L 3986120). Scale bar = 50 μm. (37) Vertical section through a mature, raised spermatangial conceptacle showing the mucilage plug (white arrowhead) that occludes the pore opening and simple, spermatangial systems (black arrowheads) confined to the conceptacle floor (UWC 15/56). Scale bar = 50 μm. (38) Magnified view through a mature spermatangial conceptacle showing the pore canal lined with terminal, elongate initials (black arrowheads) that project into the pore canal as papillae (UWC 15/56). Scale bar = 20 μm. (39) Magnified view of a mature carpogonial conceptacle with carpogonial branches comprising a single support cell (s), a hypogynous cell (h) with sterile cell (black arrowhead), and a carpogonium (c) extended into a trichogyne (black arrows) that may project out of the pore. Note that the pore canal is lined with terminal, elongate initials (white arrows) that project into the pore canal as papillae (L 3986120). Scale bar = 20 μm. (40) Vertical section through a mature carposporangial conceptacle showing a discontinuous central fusion cell (black arrowhead) with peripherally arranged gonimoblast filaments each terminating in a carposporangium (C) (L 3986120). Scale bar = 50 μm. (41) Magnified view of the floorof a carposporangial conceptacle showing a discontinuous central fusion cell (black arrowheads) bearing a peripherally arranged gonimoblast filament (1–6) terminating in a carposporangium (C). The remains of unfertilised carpogonial branches(black arrow) persist across the dorsal surface of the central fusion cell (L 3986120). Scale bar = 20 μm.

Figures 42–46: ChamberlainiUm occidentale tetrasporangial anatomy. (42) Vertical section through the outer thallus showing an early stage tetrasporangial conceptacle primordium with peripheral roof development (black arrowheads) and a protective layer of epithallial cells (e) (L 3986120). Scale bar = 50 μm. (43) Vertical section through the outer thallus showing a later stage tetrasporangial conceptacle primordium with peripheral roof development (black arrowheads) and tetrasporangial (t) initials arranged peripherally around a central columella (c). Note the persisting layer of protective epithallial cells (e) (UWC 93/220). Scale bar = 50 μm. (44) Vertical section through the outer thallus showing a maturing tetrasporangial conceptacle with peripheral roof development (black arrowheads) and tetrasporangial (t) initials, peripherally arranged around a central columella (c). Note the layer of protective epithallial cells (e) (UWC 93/220). Scale bar = 50 μm. (45) Vertical section through a mature, raised tetrasporangial conceptacle showing tetrasporangia (t) with stalk cells (white arrowheads), peripherally arranged around a well-defined central columella (C). Note, the sunken and unoccluded pore opening (white arrow) (UWC 93/220). Scale bar = 100 μm. (46) Magnified view of the pore canal of a mature tetrasporangial conceptacle showing terminal, elongate initials (black arrows) that project into the pore canal as papillae and the base of the pore canal sunken (black arrowheads) into the chamber with terminal, elongate initials near the base pointing downward. Note, the sunken and unoccluded pore opening (white arrow) (UWC 93/220). Scale bar = 20 μm.