mangrove

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Field Studies: Mangrove: 

Field Studies: Mangrove Mangrove Habitat at Ting Kok Road (汀角道) A general view of the lower shore at low tide, exposing the muddy substratum and the pneumatophores of mangrove plants.

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Hibiscus tiliaceus (Beach Hibiscus; Seacoast Mallow)(黃槿) Family: Malvaceae (錦葵科) An evergreen tree, with heart-shaped leaves of 5-15 cm in diameter. Fruits are capsules, about 2-5 long; each of 5 valves containing 3 seeds.

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Pandanus tectorius (Screw Pine) 露兜樹 Family: Pandanaceae露兜樹科 An evergreen shrub with spiny leaves, leaves about 1 m long, 5 cm broad, spirally arranged in tufts. Fruits about 20 cm in diameter, turning orange-red when ripe, resembles a pineapple, and is edible.

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SHRUBS (BACK-OF-SHORE) Scaevola sericea (Beach Naupaka)草海桐 Fam: Goodeniaceae A succulent shrub with fleshy leaves, bright green and oval shaped, 8-13 cm long. With white flowers of 2 cm long, borne in summer, usually several together.

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Clerodendrum inerme假茉莉 (Seashore Glorybower) Fam: Verbenaceae 馬鞭草科 Wild shrub about 1.2 in tall, with eliptical leaves 2.5-7.5 cm in length. Flowers white, about 2.5 cm long, with long purplish red stamens; 3 flowers as a group.

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LITTORAL ZONE MANGROVE PLANTS (From high water mark to low water mark) Suaeda australis (South Sea-Blite)南鰜蓬 Fam: Chenopodiaceae 藜科 It is a low-growing herb found at high water mark. With short, linear fleshy leaves. The fleshy leaves and stems are water storage organs. The leaves are scale-liked, so as to reduce surface area and thus reduce transpiration.

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Luinnitzera racemosa (Lumnitzera)欖李 Fam: Combretaceae 使君子科 Leaves rounded, fleshy, with a notch at the tip, 2 cm long. Flowers small, pink. (N.B.: The big pink flower shown is from the climber Canavalia maritirna).

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Acanthus ilicifolius 老鼠勒 (Spiny Bears Breech) Fam: Acanthaceae爵床科 It is an erect shrub found in upper shore, 0.3-2.5 m high; with smooth, cylindrical stem. Leaves opposite and stiff, 9-14 cm long, oblong in outline with spiny edges and short leaf stalk. Flowers appear from January to June in spikes, bluish rink in colour.

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Excoecaria agallocha (Milky Mangrove)土沉香,海漆 Fam: Euphorbiaceae Leaves entire, rounded, 5-8 cm long. A shrub reaching 3 in tall.

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Exeoecaria agallocha (Milky Mangrove) White latex found dripping down in case the petiole or the leaf blade is detached - a diagnostic feature of Milky Mangrove.

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Aegiceras corniculatuin (Goat‘s Horns)桐花樹 Fam: Aegicerataceae桐花樹科 A bush under 1.5 in tall; leaves leathery, with notched tip, petiole red in colour,. 5-8 cm long, 2.5-5 cm board.

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Aegiceras corniculatum (Goat's Horns) White flowers appear in clusters in April, at leaf axils or ends of twigs. Calyx with 5 sepals, 5 petals and 5 short stamens.

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Aegiceras corniculatuin (Goat's Horns) Fruits are the curved droppers, turning from green to red when mature. Droppers are pointed, about 3 cm long, eventually splitting open as the seed germinates inside it before it falls off.

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Sporobolus virginicus (Rat-tail Grass)鼠尾粟 Fam: Graminae The grass grows on drier sites of the shore, proliferates by runners and grows into green patches. The inflorescence is seemingly a long spike resembles the rat's tail but actually is panicle (outgrowth).

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Bruguiera conjugata 木欖 (Many-Petalled Mangrove) Fam: Rhizophoraceae 紅樹科 It is a small tree coaching 2 in or bigger. Leaves are opposite, up to 10 cm long, with acute apexes. Flowers appear from May to November, reddish in colour and pendulously hanging in leaf axils, usually single. Fruits are droppers with 12 to 14 calyx parts, often red in colour.

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Bruguiera conjugate (Many-Petalled Mangrove) The knee joints are the adventitious roots modified for providing support and also of breathing purpose. They are arch-liked structures with spongy cells inside.

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Kandelia candel 水筆仔,紅朗 Fam: Rhizophoraceae A much branched shrub reaching 2 in in height. Leaves waxy, 7.5-10 cm long. Partially submerged periodically since growing in inter-tidal zone.

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Kandelia candel Bark is smooth, greyish brown. Trunk with swollen ridged base extending outwards, the buttress roots, which are adventitious roots at stem base, are modified for providing extra support to the plant in a muddy substratum.

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Kandelia candel Flowers white; calyx with 5 sepals, surrounded at the base by a cup-shaped bract. Ovary develops into a young dropper after the petals have fallen.

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Kandelia candel Fruits are oval-shaped droppers, surrounded by the resistant reflexed calyx segments. Droppers are about 13-15 cm long, pointed, green in colour when mature. The seed in each dropper germinates on the plant, with the primary stem much elongated before dropping to the muddy substratum. Thus Kandelia is well-known as a viviparous plant.

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Kandelia candel After the dropper had anchored on the muddy ground, further development of the primary stem occurs, giving out the first few foliage leaves. Lateral roots develop simultaneously.

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Avicennia marina 海欖雄 (Black Mangrove) Fam: Verbenaceae It is the pioneer plant in the mangrove habitat, up to 1 m in height. The cable root system gives rise to the antennae-liked pneurnatophores, sticking out of the substratum, with air holes, enabling the root system to breathe the atmospheric air.

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Avicennia marina (Black Mangrove) Leaves are opposite; can reach 2.5 cm in length, with the upper surface brightly green and a characteristically white lower surface.

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Avicennia marina (Black Mangrove): fruit The fruit of Avicennia is a rounded capsule about 2 cm long. They are often washed up beach. Avicennia is one of the few mangrove plants which do not form droppers.

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ANIMALS PHYLUM: MOLLUSCA CLASS: GASTROPODA腹足綱 Clithon oualiensis (Estaurine Snail) Fam: Neritidae 蜑螺科 The Estaurine Snails are found on low tide mark of the mud-flat, with rounded shells showing polymorphism (i.e. different colour patterns in different individuals). Can tolerate a 1ow salinity (especially in low tide, the river dilutes the salinity of the mudflat). A detritivore grazer feeding on organic debris.

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Littorina scabra (Periwinkle)鶉濱螺 Fam: Littorinidae Found on the upper shore, about 2 cm long. Gliding on the rocks and leaf surfaces. The periwinkle feeds on plant materials and algae on the mangrove leaves.

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Littorina melanostoma (Periwinkle) Fam: Littorinidae Also found on the upper shore, usually on the trunks and leaf surfaces. With a greyish-white shell, about 2.5 cm long, the dark red pattern near the opening of the shell is the characteristic feature of Littorina melanostoma.

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Nerita chamaeleon Fam: Neritidae This sea snail is usually found under rocks in the middle shore region. With black and yellow patches on its shell. A herbivore grazing on algae. Also found on boulder shores usually.

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Terebralia sulcata Fam: Potamididae海蜷科 Usually found on mid-shore mud surface, but sometimes found on the trunks of mangrove plants. The characteristic hole on the shell is a diagnostic feature of this snail. Also a detritus feeder.

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CLASS: BIVALVIA 瓣鰓綱 Saccostrea cucullata (Rock Oyster)石蠔 Fam: Ostreidae Usually found cemented on rocks and trunks of plants. In this case sticking to a pneumatophore. Filter feeder feeding on plankton and organic debris. Edible.

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PHYLUM: ARTHROPODA CLASS: CRUSTACEA Order: Isopoda等腳目 Ligia oceanica (Sea Slater) 水蟑螂 They are wide-spread among rocks and leaf litter, crawling rapidly among rock crevices. With a pair of large compound eyes and 7 pairs of long legs. Breathing takes place in some of their posterior appendages which have thin surface areas. Detritivores feeding on dead leaves, organic debris etc.

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SUB-CLASS: CIRRIPEDIA 蔓腳類 Balanus albicostatus (Acorn Bamacle) 籐壺 The sedentary adult is about 1 cm in diameter, sticks on the trunk of mangrove plants. Barnacles are filter feeders; feeds only when submerged by sea water. Feed on planktons and organic particles suspended in water.

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SUB-CLASS: MALACOSTRACA Order: Decapoda十腳目 Sesarmid Crab 磯蟹 Fam: Grapsidae磯蟹科 The small crab is a scavenger ingesting dead fishes and organic debris. It makes burrow on the soft mud and goes out to feed only in low tides.

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Sesaminid Crab and Eupagurus sp. (Hemit Crab) 寄居蟹 Fam: Eupaguridae寄居蟹科 The Sesamrnid crab hides under the rock. The Hermit Crab bears a shell of the dead snail and crawls around. Also a scavenger.

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PHYLUM: CHORDATA CLASS: PISCES (FISH) Boleophthalmus spp. Fam: Gobiidae (Mudskipper)彈塗魚 A semi-aquatic fish, with brown spotted body. The head with a pair of large bulging eyes, and strong pectoral fins to prop up its body, then skips by a quick flip of tail. It eats small crabs and shrimps, occasionally the insects in air.

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Gobius spp. (Goby Fish) Fam: Gobiidae These small fishes are usually found in coastal water. In low tides, they are trapped in water pools. They are brown in colour with black spots, nearly invisible when laying on the mud. Can reach 8 cm long, feeding on small shrimps and organic debris.