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Order Ceramiales

Family Delesseriaceae

Acrosorium Zanardini ex Kützing

Plants of various shapes, mainly monostromatic but polystromatic on older (basal) parts and sometimes along (microscopic) veins; microscopic veins comprising elongated cells; branching where present from margins of blades. Growth from cells in thallus margin.

Tetrasporangia and spermatangia in sori below the edges of blades; cystocarps scattered in blades.

Key to Acrosorium species

Key to the species

 

1 a. Blades narrow, strap-like (to 3 mm wide), some apices forming hooks or sickle-like hamifera

A. ciliolatum

1 b. Blades wider, without terminal hooks or hamifera

2

2 a. Blades with scattered, pale to yellowish spots

A. maculatum

2 b. Blades without pale spots

A. acrospermum

 

Notes:

1. Two Acrosorium species recorded from this coast are not described here:

 Acrosorium deformatum (Suhr) Papenfuss 1943: 90-91

This small (to 5mm high) species is recorded from the Eastern Cape (type locality Algoa Bay) as an epiphyte on an unidentified Gelidium species, and was earlier included as a possible synonym of A. acrospermum by J. Agardh (see Papenfuss 1943: 90). We have neither collected nor seen specimens of this entity, but have seen several specimens of small A. acrospermum, A. maculatum and A. ciliolatum that grow as epiphytes on various larger algae, often partly wound around and adherent on the thallus.

Acrosorium amphiroae Jaasund 1976: 119 fig 241 (nom. inval.)

Two specimens are ascribed to this species from Hluleka in Transkei (Bolton and Stegenga 1987). The specimens are epiphytic on Amphiroa bowerbankii and Amphiroa ephedraea, growing as a thin tube that surrounds the thallus of the coralline alga, but with upright portions. However, the presence of pale spots in some of these indicates that they may be Acrosorium maculatum.

2. Examination of many BOL specimens suggests that all these species need to be re-examined. For example, there are some that are small, linear, have hooked tips but have pale spots (A. ciliolatum or A. maculatum?). Also, Stegenga et al. (1997) point out that A. maculatum and A. acrospermum seem to differ only in the former having pale spots.

 

References Acrosorium

Bolton JJ & H Stegenga 1987. The marine algae of Hluleka (Transkei) and the warm temperate / sub-tropical transition on the east coast of southern Africa. Helgolander Meeresuntersuchungen 41: 165-183.

Jaasund 1976. Seaweeds in Tanzania. A field guide. 116 pp. Tromsø, University of Tromsø.

Papenfuss GF 1943. Notes on South African marine algae II. Journal of South African Botany 9: 79-92.

Stegenga, H., Bolton, J.J. & R. J. Anderson. 1997. Seaweeds of the South African west coast. Contributions from the Bolus Herbarium 18: 655 pp.

 

Cite this record as:

Anderson RJ, Stegenga H, Bolton JJ. 2016. Seaweeds of the South African South Coast.
World Wide Web electronic publication, University of Cape Town, http://southafrseaweeds.uct.ac.za; Accessed on 24 September 2018.