Electronic Flora of South Australia Family Fact Sheet

FAMILY DELESSERIACEAE Bory 1828: 181

Phylum Rhodophyta

Thallus mostly epilithic or epiphytic, some genera minute and parasitic, fronds strongly compressed to flat or foliose, almost entire to much branched from the midrib or the blade margins. Branching endogenous or exogenous, sometimes adventitious. Blades monostromatic to polystromatic, entire to lobed or divided, in a few genera forming a network. Midrib and veins present or absent. Older axes usually stipe-like by loss of lateral blade or wings, attached by a discoid or fibrous rhizoidal holdfast. Structure. Growth (Delesserioideae) by means of a dome-shaped or obconical apical cell segmenting to give an axial filament and 2 lateral pericentral cells followed by 2 transverse pericentral cells, the lateral pericentral cells developing second-order cell rows from which third-order cell rows (and often some fourth-order rows) arise abaxially, all or not all cells forming cell rows and all or not all rows reaching the blade margin, or (Nitophylloideae) growth by apical cells at the branch apices or on the margins or by means of marginal cells at the branch apices dividing by oblique divisions with 2 cutting faces, forming a flat membrane one or a few cells thick, with frequent intercalary divisions. Midrib and lateral veins present or absent, the midrib corticated or not, primary cells of blades corticated or not. Cortical cells equivalent to the primary cells in dimensions, or half or less (dimidiate) of the primary cells. Mature cells usually multinucleate. Rhodoplasts discoid, sometimes becoming elongate or ribbon-like in larger cells.

Reproduction: Reproductive organs formed on or in the blades or bladelets.

Gametophytes dioecious. Procarps produced on transverse pericentral cells near apices (Delesserioideae) or scattered over the blades (Nitophylloideae), with or without an anterior pericentral (cover) cell and with the supporting cell (pericentral or surface cell) forming 1 or 2 sterile groups and one or two 4-celled carpogonial branches. Post-fertilization the auxiliary cell is diploidised via a connecting cell or process from the carpogonium, and the carposporophyte develops usually a basal fusion cell, much branched gonimoblast filaments and single or chains of terminal carposporangia. Cystocarps ovoid and stipitate to immersed in the thallus, ostiolate, pericarp 1–5 cells thick with cells of the blade cortex in some genera forming erect filaments which may cut off outer cortical cells. Spermatangia develop in sori on the blade, often in linear patches on elongate blades, or irregularly scattered, with primary or cortical cells cutting off initials by periclinal then anticlinal divisions, which then produce several spermatangia.

Tetrasporangia produced in sori usually on both sides of blades, cut off from primary or inner cortical cells and lying in a single layer or 2 irregular layers, covered by a small-celled cortex, subspherical and tetrahedrally divided.

Type genus: Delesseria Lamouroux 1813: 122, nom. cons.

Taxonomic notes: A family of some 95 genera (Wynne 1983, 1996), arranged in several groups which are considered equivalent to tribes by some authors; however, few tribes have been formally described [e.g. Dicroglosseae by Millar & Huisman (1996), Myriogrammeae by Hommersand & Fredericq (1997a), Schizoserideae by Hommersand & Fredericq (1997b) and Hemineureae by Lin et al. (2001)]. Referral of the genera to groups, as in Kylin (1924), was followed by Wynne in his numerous publications and his 1996 key to the genera. Use of groups is followed here, since recognition of tribes has little advantage, and some of the characters used to separate them need further study, e.g. the absence or presence of veins in the blades; in Hymenena multipartita the veins are often very faint and scarcely recognisable, and in H. curdieana the veins are 2–4 cells broad in contrast to the veins in H. affinis which are only one cell broad. The nature of carposporangia also merits further study. While in some taxa they are clearly terminal only, in other taxa the next lower gonimoblast cell matures rapidly when the upper one is shed, and if this happens before shedding then they occur in short chains; this difference appears slight. In Platyclinia however, distinct rows of 3–5 carposporangia occur, with broad joint walls separating them. Use at generic level of gonimoblast cell fusions with cells of the primary cell plate on the cystocarp floor also needs caution. Such fusions are often extensive in Haraldiophyllum but occur close to the fusion cell in several genera (e.g. Cryptopleura, Kylin 1956, fig. 339B) and more extensively in Crassilingua and Platyclinia.

Some 27 genera occur on southern Australian coasts, with the richest representation on the cooler coasts of SE Australia and Tasmania.

The Sarcomenia group, due largely to the alternating (rhodomelaceous) order of pericentral cell formation, was referred to the Rhodomelaceae by Womersley & Shepley (1959), this difference being at that time considered an important basic separation between the Delesseriaceae and Rhodomelaceae. Other authors, following Papenfuss (1961), considered that other features ally the group more with the Delesseriaceae. Relationships of the Sarcomenia group have been clarified by DNA sequencing studies and the group is here regarded as a separate family (see below).

References:

BORY DE ST-VINCENT, J.B. (1828). In Duperrey, L.I., Voyage autour du monde, exécuté par ordre du Roi, sur la corvette de Sa Majesté, la Coquille, pendant les années 1822, 1823, 1824 et 1825. Botanique, Cryptogamie, pp. 1–300, Plates 1–39. (Bertrand: Paris.)

HOMMERSAND, M.H. & FREDERICQ, S. (1997a). Characterization of Myriogramme livida, Myriogrammeae trib. nov. (Delesseriaceae, Rhodophyta). J. Phycol. 33, 106–121.

HOMMERSAND, M.H. & FREDERICQ, S. (1997b). Characterization of Schizoseris condensata, Schizoserideae trib. nov. (Delesseriaceae, Rhodophyta). J. Phycol. 33, 475–490.

KYLIN, H. (1924). Studien über die Delesseriaceen. Lunds Univ. Årsskr. N.F. Avd. 2, 20(6), 1–111.

KYLIN, H. (1956). Die Gattungen der Rhodophyceen. (Gleerups: Lund.)

LAMOUROUX, J.V.F. (1813). Essai sur les genres de la famille des thalassiophytes non articulées. Ann. Mus. Hist. Nat., Paris 20, 21–47, 115–139, 267–293, Plates 7–13.

LIN, S.-M., FREDERICQ, S. & HOMMERSAND, M.H. (2001). Systematics of the Delesseriaceae (Ceramiales, Rhodophyta) based on large subunit rDNA and rbc L sequences, including the Phycodryoideae, subfam. nov. J. Phycol. 37, 881–899.

PAPENFUSS, G.F. (1961). The structure and reproduction of Caloglossa leprieurii. Phycologia 1: 8–31.

WOMERSLEY, H.B.S. & SHEPLEY, E.A. (1959). Studies on the Sarcomenia group of the Rhodophyta. Aust. J. Bot. 7, 168–223.

WYNNE, M.J. (1983). The current status of genera in the Delesseriaceae (Rhodophyta). Bot. Marina 26, 437–450.

WYNNE, M.J. (1996). A revised key to genera of the red algal family Delesseriaceae. Nova Hedwigia 112, 171–190.

The Marine Benthic Flora of Southern Australia Part IIID complete list of references.

Author: H. B. S. Womersley

Publication: Womersley, H.B.S. (24 February, 2003)
The Marine Benthic Flora of Southern Australia
Rhodophyta. Part IIID. Ceramiales – Delesseriaceae, Sarcomeniaceae, Rhodomelaceae
Reproduced with permission from The Marine Benthic Flora of Southern Australia Part IIID 2003, by H.B.S. Womersley. Australian Biological Resources Study, Canberra. Copyright Commonwealth of Australia.

KEY TO GENERA OF DELESSERIACEAE The following key applies only to southern Australian taxa.

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