Field Studies: Rocky Shore

1. Field Studies: Rocky Shore Boulder/Rocky shore A relatively exposed habitat where wave action is typically moderate. Tidal effect leads to periodic submersion and emergence of the organisms at the inter-tidal zone. The substratum of the habitat are large, rounded rocky outcrops.

2. Rocky shore Wave action in rocky shore is more severe and the shore is more exposed. The substratum of rocky shore is a large piece of mother rock with immobile rock surfaces. It provides firm attaching sites for organisms.

3. Rock pool Small pools of water may be found in the inter-tidal zone. This occurs in the low tide where the water mark retreats to lower shore, leaving the sea water trapped among rocks.

4. Puffer Fish雞泡魚in rock pool Some shore animals maybe trapped in the rock pool. They can tolerate the increasing temperature and increasing salinity in the limited volume of water, so as to survive there.

5. PLANTS - LICHENS地衣: Verrucaria spp. (Lichen) Lichens can be found on the splash zone of the shore which is only wetted by the highest tides. Grey patches of lichens can be seen, which are lower plants formed by tangling of fungus and alga. Lichens with black, yellow and orange colour may also be found.

6. ALGAE: DIVISION: CHLOROPHYTA Green Algae The algae are usually found at the lower shore. They are usually submerged but exposed in low tides. With holdfasts for attaching onto substratum. Very slimy.

7. Ulva lactuca (Sea Lettuce)石蓴 Fam: Ulvaceae石蓴科 This green alga is flat and 2-celled thick. Found sticking on rocks and usually submerged but sometimes emerges in low tides. Seldom found in summer due to the strong heating effect of sun. Flourish in spring and autumn into a mat.

8. DIVTSION: PHAEOPHYTA S. Sargassum sp. (Brown Alga)馬尾藻 The brown alga contains a brown pigment, fucoxanthin, which masks the chlorophyll. They are sea weeds found in sub-littoral zone; covered in mucilage. The round stalked floats and leaves in stem (thallus) are due to the vesicles where male and female gametes (sex cells) form.

9. PHYLUM: MOLLUSCA CLASS: GASTROPODA Nodilitorina milligrana (Periwinkle)玉黍螺 Family: Littorinidae玉黍螺科 They are minute snails found high on shore. They usually stay on bare rocks, grazing the lichens and algae found.

10. Nerita polita: ventral view錦天魚舟 Fam: Neritidae蜑螺科 They are marine snails up to 2 cm in diameter, usually found at the upper shore. The muscular foot is used for their locomotion.

11. Nerita polita: dorsal view The calcareous shell is spirally coiled with prominant growth lines. The shell is a protection against predators and desiccation. They are herbivores grazing on algae.

12. Monodonta australis(Top Shell)黑漬螺 Fam: Trochidae馬蹄螺科 The top shells can be found among the boulders at mid-shore, which is a behavioural adaptation to escape the heat of the sun when in low tides. Also Nerita albicilla (upside down) showing calcareous operculum; and touching a Tegula argyrostoma.

13. Monodonta australis (Top Shell)黑漬螺 The growth lines of the shell are close together near apex, but are further apart in the newer larger portion of the shell. Topshells ore also herbivores feeding on algae.

14. Chlorostoma rustica高腰螺 Fam: Trochidae馬蹄螺科 (Small Top Shell) Its shell is greyish-red and black in colour with white tip, usually found in the rock crevices at lower shore. It is a herbivore grazing on algae.

15. Cellana eucosmia (Smooth Limpet)虫戚 & Patelloida saccharina (Star Limpet) Fam: Patellidae Limpets are mainly found at the mid-level shore. They have a single shell and stick on rocks by means of a suctorial foot. They scrape algae off the rock by means of the powerful radula which is rasp-like.

16. Thais clavigera (Whelk) 峨螺 Fam: Muricidae The whelk is a predator on other molluscs especially the bivalves, found at the lower shore. It can bore a hole through the calcareous shell of the bivalve and digests the soft tissues extracellularly.

17. Morula musica (Oyster Tingle) Fam: Muricidae骨螺科 Its shell is greyish in colour and is very rough in texture. It is a predator feeding on oysters or barnacles by drilling with its radula teeth the calcareous shell of the prey. Frequently found in lower shore.

18. Cyprea tigris (Cowrie)寶貝 Fam: Cypraeidae They are found under the boulders at lower shore. Like the other sea snails, they also have the radula for rasping off algae. This species is very rare locally.

19. Aplysia sp.(Sea Hare)海兔 Famn: Aplvsiadae Sea Hares are gastropods but having no shells. Thus, they are vulnerable to predators. They can be found among algae which they feed upon. Their body colour usually resembles the algae and thus having a good camouflage.

20. CLASS: AMPHINEURA Liolophura japonica(Chiton)石敝 The shell splits into 8 dorsal plates, ventral side with a broad and flat suctorial foot, attaches firmly onto boulders. They are also herbivores feeding on algae at the lower shore.

21. CLASS: BIVALVIA Order: Ostreidae Saccostrea cucullata(Rock Oyster)石蠔 They are cemented onto boulders at mid and lower shore. Their body is bilaterally symmetrical, encased in a bivalved shell. Ciliary currents produced by cilia used for filter-feeding. They are edible and delicious.

22. Septifer bilocularis (Mussel)孔雀貝 Fam: Mytilidae They are brownish purple in colour, attached to rocks of mid-shore by means of the byssus threads. They are filter feeding bivalves, extracting planktons from the current of water which arc drawing in by ciliary movements.

23. PHYLUM: ANNELIDA CLASS: POLYCHAETA Hydroides norvegica(Ridged Tubeworni) Fam: Serpulidae Spirorbis forarninosus (Small Tubeworm)龍介 These fanworms construct calcareous tubes on boulder surfaces by their calcium carbonate secreting glands and then become sedentary. The crown of the fanworm extends from the end of calcareous tube when submerged, collecting detritus and planktons from the surround water. The particles adhere to the surface of the feeding structures and then conveyed to the mouth along ciliated tracts. This filter feeding mechanism is aided by the beating of cilia on the crown, producing a current of water into the tube.

24. PHYLUM: ARTHROPODA CLASS: CRUSTACEA Order: Isopoda Ligia oceanica(Sea Slater)水蟑螂 It is related to the terrestrial wood louse. Usually found among rocks and runs very fast. It is particularly active at night and difficult to catch. A detritivore feeding on organic remains.

25. SUB:CLASS: CIRRIPEDIA Balanus spp. (Acorn Barnacle)藤壺 They are volcano-like structures, grey in colour, and cover rocks at various sea depths. They can tolerate temporarv exposure and strong wave actions. They can also stick onto ships, piers etc. Two species can be found, B. amphitrite and B. variegatus.

26. Tetraclita squarnosa: close up (Acorn Barnacle) The larval barnacles attach themselves by using cement glands in the antennules, then undergo metamorphosis into the sedentary adult form. They build up their shell-plates by extracting minerals from sea. They are filter feeders sieving planktons from sea water. Feed only when submerged.

27. Pollicipes mitella(Goose Barnacle)茗荷兒,佛手 They are sedentary animals, found attached to exposed rock crevices by a stalk. They are also filter feeders that resemble the Acorn Barnacles. Although hermaphroditic, cross fertilization occurs and free- swimming larval forms result.

28. SUB-CLASS: MALACOSTRACA Order: Decapoda Diogenes edwardsi寄居蟹 Fam: Eupaguridae (Hermit Crab) The Hermit Crab lives inside the abandoned gastropod shell. It crawls around on rocks, seeking for decaying organic debris, i.e. a scavenger. Retreats into the shell when irritated.

29. Hemigrapsis sp.岸蟹 Fam: Grapsidae磯蟹科 (Small Shore Crab) Samll crabs around 3-4 cm across. This purple chelated crab begins to blow bubbles out when taken out of water. It is the most belligerent (aggressive) crab on Hong Kong shores.

30. Shore Crab Fam: Grapsidae This tiny crab tends to hide under rocks. Can walk sideways by its 4 pairs of walking legs, which have pointed ends.

31. Hemigrapsus sanguieneus: dorsal side Fam: Grapsidae (Small Shore Crab) This brown shore crab is 4 cm across (including limbs) with a pair of stalked compound eyes which are movable. A tough carapace covers the cephelothorax. 4 pairs of pointed thoracic appendages for walking sideways. Usually found in rock pools.

32. Hemigrapsus sanguieneus: ventral side The abdomen reduced to a flap under the thorax. A pair of pincer-like chelae for predacious feeding on small animals, detritus and grazing on algae.

33. Thalamita sp.(Swimming Crab)窟沙蟹 Fam.: Portunidae It is actually a pelagic (oceanic) crab living offshore, but occasionally visit the rocky shore. It is characterized by its rounded hind-limbs (i.e. the 4th pair of thoracic appendages) used for swimming.

34. Thalamita sp. : close up The pelagic crab when caught and put onto rocky substratum seems handicapped in its locomotion. It is adapted to submerged condition and soon dies if exposed under sun for a long period.

35. PHYLUM: ECHINODERMATA CLASS: ECHINOIDEA Anthocidaris crassispina Fam: Diadernatidae (Short-spined Sea Urchin)海膽 They are found on the sea bottom and rock pools where the algae grow thickly. They creep along by means of movable spines. The oral (or lower) surface bears the mouth, with 5 teeth for rasping off algae.

36. CLASS: HOLOTHUROIDEA Protankyra bidentata (Sea Cucumber)海參 They are found in the coarse sand under stones. Look like worms, with 5 longitudinal series of tube-feet. They collect sand particles by the sticky tentacles around their mouth, and sort out the organic particles within.