The once sleepy town of Hua Hin (หัวหิน), now a popular beach resort in Thailand's
Prachuap Khirikhan (ประจวบคีรีขันธ์) province, still has a rather quiet sandy beach in comparison
to other tourist locations along the nation's 3,219 km long coastline. However,
besides some stray dogs and domesticated horses, the beach also teems with
wildlife. We found a lone Sand Crab and some Little Egrets that were feeding on
whatever they could catch, as well as thousands of tiny Sand Bubbler Crabs. This
species of tiny crab of the genus Scopimera inflata, sometimes referred to by
the scientific name Dotilla fenestrate, and belonging to the family Ocypodidae,
don't grow much larger than a mere 1.5 centimeter and have pincers that point
downwards, enabling them to scoop sand into their highly adapted mouthparts at
high speed. They feed on organic matter and microscopic small creatures called
myofauna that are living in the upper layer of damped soil on sandy beaches.
Soon after the tide has exposed the beach these tiny crabs emerge from small
burrows in the sand and start sieving detritus from the sand. During this
process they pass sand particles through their mouths, filtering the edible
elements out and regurgitating unwanted particles in the form of tiny pellets of
sand, which they discard all over the beach. In Thai, they are called poo pan
saay (ปูปั้นทราย), which translates as ‘sand molding crab’. The Little Egrets we
saw were in breeding plumage. These wading birds, with the scientific name
Egretta garzetta, are 55 to 65 centimeters tall, white plumage and a mostly
blackish bill, blackish legs and -oddly- yellow feet, although during the
breeding season the feet may turn reddish yellow, whereas their distant cousin,
the subspecies Egretta garzetta nigripes, has blackish feet. Breeding adults
also develop long nape-, back- and breast-plumes, while the facial skin may
become reddish in colour. Their habitat consists of various open freshwaters and
coastal wetlands, as well as cultivation, and in Thai, it is is known as nok
yahng pia (นกยางเปีย) and nok krayahng pia (นกกระยางเปีย). The Sand Crab we came
across was a juvenile. The species, with the binomial name Portunus pelagicus,
is known in Thai as poo mah (ปูม้า), i.e. ‘horse crab’ or ‘bench crab’. When
fully grown, this baby marine crab, will grow a carapace that can measure up to 20
centimeters in width. The colour of adult females is greenish grey with some
shades of blue and marked with white blotches, whereas adult males are more
bluish allover and have longer claws. These crabs are indigenous throughout the
Indic and West Pacific Oceans, from Japan and the Philippines throughout South,
East and Southeast Asia. Though largely marine, this large crab also enters
estuaries for food and shelter, especially when reproducing. Yet, unable to
tolerate low salinities for extended periods, it will eventually move back to
the sea, especially during the rainy season when mass emigrations occur. In
English, the Sand Crab is also known by a variety of other names, including Blue
Swimming Crab, Blue Manna Crab, Blue Crab, Flower Crab and Blue Swimming
Crab. Since they are edible, adults can often be seen at restaurants and on
markets, usually still alive with their claws tied. Live blue crabs are called
poo mah pen (ปูม้าเป็น), in Thai.
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