Thalassia hemprichii (Ehrenb.) Asch.

J. R. Timberlake, E. S. Martins (2009). Flora Zambesiaca, Vol 12 (part 2). Royal Botanic Gardens, Kew

Type

Type Eritrea, Massawa, 1820–1826, Ehrenberg 170 (B† holotype, BM lectotype, K, L, P).

Morphology General Habit

Submerged marine herb

Vegetative Multiplication Rhizomes

Rhizome terete, 2–5 mm wide, greenish to light brown, with many annular scars; erect stem terete, to 5 mm wide

Morphology Leaves

Leaves 4–25(40) 0.3–0.7(1.1) cm, bright to dark olive-green with red-violet spots or streaks; nerves 9–13(17), margins appearing smooth, apex rounded, finely serrated

Morphology Leaves Leaf sheaths

Sheaths 3–7 cm long, old ones persisting as torn membranous remnants

sex Male

Male spathe with peduncle 3–4(5) cm long, spathe-bract 1.7–2.5 cm, entire or finely serrated at apex Male flowers 1 per spathe, pedicel 2–3 cm long; tepals 7–8 3 mm, entire; stamens (3)6–9(12), anther 7-11 mm long

sex Female

Female flowers subsessile, ovary of 6 carpels up to 10 mm long, hypanthium 2–3 cm long, styles 6, 5–7 mm long, stigmatic branch nearly as long or up to twice as long as style, becoming recurved at maturity Female spathe with peduncle up to 1.5 cm long, spathe-bract 1.7–2.5 1 cm

Morphology Reproductive morphology Fruits

Fruit 2–2.5 1.7–3.2 cm, light green, with a 1–2 mm long beak, splitting into 8–20 irregular valves

Morphology Reproductive morphology Seeds

Seeds 3–9, c.8 mm long, conical part greenish, thick basal portion dark brown.

Distribution

Mozambique. Widely distributed throughout tropical regions of the Indian Ocean and western part of the Pacific, along the East African coast from Egypt to Mozambique, also in Madagascar and the Seychelles.

Ecology

On sandstone and coral rocks, especially on dead reef platforms and sublittoral flats consisting of coral-debris or coral-sand, often luxuriant in shallow eulittoral pools on coral-sand covered with fine mud, where it forms extensive meadows, reportedly eaten by fish. Often associated with Halodule wrightii with Thalassia occupying small depressions and Halodule higher places exposed at low spring tides; from low water mark to 7 m depth.

Phenology

Flowers in July and August.

Conservation

Conservation notes Widespread species; not threatened except locally by food collectors on intertidal beds.

Recognition

Thalassia hemprichii can be readily distinguished from Thalassodendron ciliatum (Forssk.) Hartog (Cymodoceaceae). The latter has the old leaf sheaths falling away, the erect stem are long, ligneous and bare, not covered with leaf sheaths but with prominent annular leaf-scars, and the leaf margins are more deeply serrulate near the apex.