Hydroclathrus clathratus (C. Agardh) Howe, 1920: 590

Coppejans, Eric, Leliaert, Frederik, Verbruggen, Heroen, de Clerck, Olivier, Schils, Tom, de Vriese, Thomas & Marie, Daniel, 2004, The marine green and brown algae of Rodrigues (Mauritius, Indian Ocean), Journal of Natural History 38 (23), pp. 2959-3020 : 3006-3007

Hydroclathrus clathratus (C. Agardh) Howe, 1920: 590

References: Taylor, 1960: 261, pl. 36, figure 5 ; Jaasund, 1976: 47, figure 96; Tseng, 1984: 186, pl. 94, figure 2 ; Womersley, 1987: 300, figures 109A, 110A, B; Coppejans et al., 1995b: 178, figure 1 ; Cribb, 1996: 49, figure p. 48; Lewmanomont and Ogawa, 1995: 73; Littler and Littler, 2000: 248, figure p. 249; Payri et al., 2000: 144, figure p. 145; Skelton and South, 2002: 158, figure 19A ; Littler and Littler, 2003: 178, top figure p. 179.

Type locality. Uncertain.

Vouchers. HEC 14675azb (zF), 20 September 2001, Rivière Banane (s.s. 12) ; HEC 14756a, 22 September 2001, Grand Baie (s.s. 11) ; HEC 14786, 25 September 2001, Passe Grand Bassin (s.s. 1) .

Ecology. Epilithic, from high intertidal (rare) down to spring low water mark (more frequent).

Distribution. Aldabra Islands, Andaman Islands, Australia, Bahrain, Bangladesh, Diego Garcia Atoll, India, Indonesia, Kenya, Kuwait, Laccadives, Malaysia, Maldives, Mauritius ( Børgesen, 1941: 62, 1948: 49–50), Mozambique, Nicobar Islands, Pakistan, Réunion ( Montagne and Millardet, 1862: 21 ~ Hydroclathrus cancellatus Bory de Saint-Vincent ), Rodrigues ( Dickie, 1877a: 6), Saudi Arabia, Seychelles, Singapore, Somalia, South Africa, Sri Lanka, Tanzania.

Note. The crisp, three-dimensional thalli of H. clathratus mainly grow epilithic at about low water mark. The suppler, strap-like thalli of H. tenuis were usually entangled with other seaweeds (e.g. Sargassum ) or corals, although it has also been found drifting in the lagoon. In a few instances, we observed that H. clathratus , exposed at low tide to the air, was closely associated with thalli of H. tenuis , continuously submerged in the rock pool next to it. This casts doubt on the taxonomic identity of H. tenuis . Womersley (1987: 302) states that ‘ H. clathratus is distinctive in form but varies considerably in compactness of the net, the more compact forms usually occurring in shallow water with more wave action’. He does not refer to H. tenuis .

Figures

FIGS 2–6. Chlorophyta. (2) Microdictyon tenuius, detail of branching and anastomosing patterns (HEC 14849). (3) Bryopsis pennata var. pennata, branchlets of last order contiguous and in a single plane (HEC 14796 p.p.). (4) Bryopsis pennata var. leprieurii, branchlets of last order interrupted and in a single plane (HEC 14757).(5) Bryopsis pennata var. secunda, branchlets of last order curved in one direction (HEC 14796 p.p.). (6) Chamaedoris delphinii (HEC 14617). Scale bars: 250 mm (2); 5 mm (3–5); 1 cm (6).

FIG. 1. Sampling stations. See table 1 for a list of the stations and their GPS coordinates. Map redrawn from Wells (1988). The outer grey line represents the fringing reef.

FIGS 19–24. Chlorophyta. (19) Caulerpa nummularia, proliferating from primary, peltate assimilator (HEC 14609 p.p.). (20) Rhipidosiphon javensis (HEC 14763). (21) Udotea sp. (HEC 14759). (22–24) Udotea palmetta (HEC 14817): (22) general morphology of large, fertile specimen; (23) gametangia growing from the blade surface; (24) gametangia growing from the blade margin. Scale bars: 2 mm (19, 20); 1 cm (21, 22); 1 mm (23); 500 mm (24).