home Home
WCAG2AA
Hong Kong Fishnet Endangered Species Animal Welfare and Control
AGRICULTURE FISHERIES COUNTRY & MARINE PARKS CONSERVATION Inspection & Quarantine
* Do you know? Main Menu

Questions
 

1. Why are there so many holes and small dunes on the sandy flat?
 
  
Answer 1
 
 
 
2. Do all crabs walk laterally?
 

 
Answer 2 
 
 
 
3. Why the pincers of the following crabs are in uneven size?
 

Answer 3 
  
 
 
4. Why do people call mangrove as “red trees” in Chinese but apparently they are not red? 
 


Answer 4

 
 
 
5. Can trees carry embryo like human? 
 
Answer 5
 
 
 
6. Can trees sweat like human?
 
Answer 6 
    
 
   
7. As a kind of fish, why mudskipper can live in both water and land freely? 
   
  
     
Answer 7 
  
 
   
8. Can we walk along the mangrove? 
  
   
    
Answer 8 
 

 
  
Answers
 
 

Answer 1   
 
These holes are mainly dug by different types of crab and the dunes are originated from the holes.  These holes not only serve as homes for crabs, they can also facilitate air circulation of the lower soil and thus enhance decomposition of organic matters. 
  

  Back to Top
 
    
Answer 2  
 
No.  Most crabs can walk only laterally, however, soldier crabs walk forward instead sideway.  
 
 
  Back to Top

  
 
Answer 3 
 
Because they are male fiddler crabs.  They get a bigger pincer for self-defence, mating and fighting, while the smaller one is used for feeding on organic matters in the sand.  For the female ones, both pincers are small in even size.  


Uca borealis (Male) 
 
 Uca borealis (Female) 
 
                    
  Back to Top
     

Answer 4  
 
The Chinese name of mangrove came from the mangrove plants, especially family Rhizophoraceae. This family contains large amounts of reddish brown substance called tannin; therefore, Chinese called mangroves “red trees”.
  

  Back to Top

 
 
Answer 5
 
Some mangrove species (e.g., Kandelia obovata, Aegiceras corniculatum and Bruguiera gymnorrhiza) carry embryos called droppers inside their attached fruits and this phenomenon like “babies” being carried in their mothers.  Droppers are germinated seeds that attach to the parent plant of mangroves after germination.  This kind of viviparous reproduction allows rapid growth and establishment of mangrove seedlings once they come into contact with the substratum.  It increases the survival rate of the mangroves in the unstable substratum and the intertidal environment.


Kandelia obovata 
 
 
 
Bruguiera gymnorrhiza   
 
 
 
Kandelia obovata  
 
 
  Back to Top


Answer 6 
 
Without the sweat gland, trees certainly cannot sweat like human. Nevertheless, salt glands are present in the leaves of some mangrove species (e.g., Aegiceras corniculatum and Lumnitzera racemosa).  These salt glands are used to concentrate and actively excrete the absorbed salts so as to regulate the salt concentration inside the mangroves.  As the salt is excreted in liquid form, it seems like the sweat on human, but salt crystal will be formed once the water is evaporated. 
 


Salts were excreted as crystal on Aegiceras corniculatum’s leaf surface in bright daytime   
Salts were excreted as solution on Aegiceras corniculatum’s leaf surface in the evening
 

 

  Back to Top

 
Answer 7   
  
This distinctive fish inhabits intertidal mudflat because it can breathe through their moist skin and store water in their gills.  These special characteristics enable mudskipper to be out of water or in intertidal area for quite some time.
   
  

  Back to Top

  
Answer 8 
  
 
 
Ting Kok coastal area is a typical mangrove habitat. During high tides, sediments along coastal areas are covered by water; while during low tides, sediments along coastal areas are exposed in the air.  In general, when the tidal levels are less than 1m, we can walk along the mangrove. 
 
You may click HERE for details of Predicted Tides at Tai Po Kau from the Hong Kong Observatory.  Please be reminded that tidal levels may be affected by many factors, including rainfall and wind.  Be alert to the change in the environmental condition during your visit.
 
    

Back  Back to Top
 
Last Review Date : 19 December 2014