Rhipilia baculifera (J.Agardh) Huisman & Verbruggen, 2023

Huisman, John M. & Verbruggen, Heroen, 2023, A morphological and molecular study supports the recognition of Rhipilia psammophila sp. nov. and Rhipilia baculifera comb. nov. (Halimedaceae, Chlorophyta) from southern Australia, Australian Systematic Botany 36 (6), pp. 427-436 : 433-434

Rhipilia baculifera (J.Agardh) Huisman & Verbruggen , comb. nov.

Bryopsis baculifera J.Agardh, Acta Univ. Lund. 23(2): 21 (1887); Chlorodesmis baculifera (J.Agardh) Ducker, Phycologia 5: 245 (1966).

Type citation: ‘ad oras australes Novae Hollandiae; ad Port Phillip legit Br. Wilson!’. Type: Port Phillip Heads, Victoria, John Bracebridge Wilson (holo: Herb Agardh, LD 14898 n.v. ( Ducker 1966, p. 245, 1967, p. 156, noted that the type was J.B.Wilson 39, dredged at Port Phillip Heads in 1880)).

Cladophoropsis bulbosa Womersley , Pacific Sci. 9: 391 (1955); Chlorodesmis bulbosa (Womersley) Ducker, Phycologia 4: 149 (1965).

Type: Queenscliff , Victoria, s. dat., leg. ign. (holo: MEL 3007 ).

Thalli medium to dark green, erect, densely tufted, 4–10(–16) cm high, attached by colourless rhizoids and when mature arising from a matted bulbous base up to 2 cm high, formed of entangled rhizoids, in some specimens forming a conspicuous terete stipe up to 6 cm long, 5 mm in diameter. Filaments sparsely branched, of uniform width throughout, (250–) 300–500(–600) µm in diameter; wall lamellate, 6–10 µm thick; lateral branches slightly basally constricted; chloroplasts ovoid to lenticular, 2–4 µm long; amyloplasts elongate-ovoid, 6–10 µm long. Reproduction in much branched fertile tufts borne laterally or terminally on the filaments, with each branch of the tuft bearing numerous ovoid laterals that form biflagellate reproductive bodies (probably gametes) that are discharged through the branch apex; fertile in early summer (November–December). (Description modified from Womersley 1955, pp. 391–392 [as Cladophoropsis bulbosa ], 1984, p. 244 [as Chlorodesmis baculifera ]; Ducker 1965, pp. 150–155 [as Chlorodesmis bulbosa ]). ( Fig. 4 )

Distribution

Known from Rottnest Island , Western Australia, and from Pearson Island , South Australia, to Waratah Bay , Victoria, and the northern coast of Tasmania.

Habitat

According to Womersley (1984, p. 244), this species is uncommon and ‘apparently confined to deep water or shaded habitats’. Our recent collections in Victoria have primarily come from shaded areas, but we have also observed it quite commonly in large rock pools among seagrass growing on sand-covered rock. Ducker (1965, pp. 149–150) described similar habitats: ‘littoral rockpools’ and ‘among the dense stand of the marine flowering plant Cymodocea [ Amphibolis ] antarctica ’.

Etymology

From the Latin baculus ‘rod or staff’ and suffix - fer ‘bearing’, presumably in reference to the thick and firm branches (‘crassitie et firmitate filorum’; Agardh 1887, p. 21).

Notes

Our specimens conformed in most respects to descriptions of Chlorodesmis baculifera by Ducker (1965, as C. bulbosa , 1967) and Womersley (1984), differing only in the position of fertile heads, which Ducker (1965) described as ‘modified sidebranches’. In our specimens the fertile heads arose in what appears to be an apical position ( Fig. 4 e, f ), although the bearing filament might be interpreted as an elongate pedicel. Molecular analyses were undertaken with specimens collected from near the Point Lonsdale type locality at Port Phillip Heads, Victoria (e.g. H. Verbruggen, H.0888, MELU), and also with a specimen from Western Australia (J. Huisman, H.0880, MELU) that confirmed the close relationship of plants from this disjunct location. Chlorodesmis baculifera is essentially restricted to southern Australia and is very much a geographical outlier in Chlorodesmis , an otherwise warm-water genus. Our molecular analyses placed this species within the Rhipilia clade and sister to R. psammophila . As such, we here publish the new combination Rhipilia baculifera (J.Agardh) Huisman & Verbruggen.

Specimens examined

WESTERN AUSTRALIA. South of Rottnest Island , dredged, 18 Jan. 1996, C.Sim s.n. ( PERTH 08822182 ); Thomson Bay, Rottnest Island , limestone reef, 10 m depth, 11 Apr. 1979, M.A.Borowitzka R 4344 ( PERTH 01600060 ) .

Figures

Fig. 4. Rhipilia baculifera. (a) Specimen in situ at type locality at Point Lonsdale, Victoria, growing among the seagrass Amphibolis antarctica. (b) Freshly collected specimens, with a limited basal aggregation of siphons. (c) Pressed specimen dredged from deep water, south of Rottnest Island, with a substantial stipe. (d) Closer view of aggregated siphons at base of specimens in Fig. 4b. (e) Free siphons that are dichotomously divided with occasional shallow constrictions. A reproductive tuft is developing at the apex of the right-hand siphon. (f) View of densely branched reproductive tuft, with moniliform lower siphons. Scale bars: 2 cm (b, c); 1 mm (d–f). Voucher: (a, b) H.Verbruggen HV03984 (MELU); (c) C.Sim s.n. (PERTH 08822182); (d–f) living material, vouchers not retained. Photos: H. Verbruggen (a, b, d–f); J. M. Huisman (c).