Text and Photos by Gloria Seow, Education
Committee Chairperson
Weekend intertidal walks are few and far between in any given year, as
such walks in places like Sentosa island and Changi beach (southern and eastern part of Singapore respectively) are possible only if the
tide falls to 0.2 metres and below. Another inconvenience involves the tendency
of ultra-low tides to be in the pre-dawn hours and on weekdays. So we counted
ourselves lucky to be out jaunting around Tanjong Rimau, a rare natural shore located
just beyond Rasa Sentosa Resort, on the clear Sunday morning of 24 July 2016
just after the sun had peeked above the horizon.
Located just beyond Rasa Sentosa Resort, the exposed rocky shoreline of Tanjong Rimau yielded bountiful sightings.
Uncle Marcus Ng was our erudite lead guide, assisted by Auntie Juria
Toramae and Uncle Ivan Kwan who moved ahead as scouts. First up, we found an
ethereal Blue-lined Flatworm (Pseudoceros concinnus) in the
shallows, a regular encounter on many of our intertidal habitats. Continuing
the blue theme, we saw a Pimply Phyllid Nudibranch (Phyllidiella
pustulosa), a sea slug around 4 cm long with a hard body sporting clustered
bumps called tubercles. Some tubercles even come in colours such as pink, red,
grey or green. Kids and their parents were intrigued by the profusion of
soft and hard corals, anemones, sponges, seagrass and seaweed that characterise
this stretch of wild rocky shoreline.
Next, Auntie Gloria came across an exposed Snapping
Shrimp (family Alpheidae).
Unfortunately, this nervous critter was so stressed by our presence that it
dropped its pincer as it ducked under a rock. Thankfully, lost pincers can
regenerate with time. Like many crustaceans, the Snapping Shrimp can willingly
shed its claws when threatened or attacked, as it is better to lose a pincer
than its life. Of its two pincers, the enlarged one can produce a one-of-a-kind
sound, so loud that it can stun tiny fish prey and even crack the shells of
small clams. Snapping Shrimps are responsible for the regular pops that one
hears around intertidal areas.
We had a really adorable baby Reef Octopus (family Octopodidae) swimming around our booties
and wellies. Uncle Marcus gently lifted it out of the water to the delight
of many. In general, octopus can survive for between 30 to 60 minutes on land,
as oxygen diffusion can still take place through moist skin. It is known to
crawl around to get from intertidal pool to pool, or to feed on shellfish or
snails found above the waterline.
One of the kids reported seeing a ‘snake’. Upon investigation, it turned
out to be a shudder-inducing metre long Giant Reef Worm (Eunice aphroditois).
Uncle Marcus said that this was a fierce predator best left alone as it can
deliver a nasty bite. Equally crabby creatures populate the intertidal
environment. In quick succession, we found a Spotted-belly Forceps Crab (Ozius
guttatus) that had both pincers raised in attack-defence mode, as well
as the highly poisonous Red Egg Crab (Atergatis integerrimus) that took
on a crouched defensive stance.
Our seekers Auntie Juria and Uncle Ivan brought back several interesting
finds including a huge Spider Conch Shell (the classic looking shell
that people can hold to their ears to ‘hear’ the sea), as well as a Giant
Top Shell Snail (Tectus niloticus), an enormous snail with a pyramidal
shell. Other marvellous encounters included the Black Long Sea Cucumber (Holothuria
leucospilota), Blue Jorunna Sponge (Neopetrosia spp) and Leather
Coral (Sarcophyton spp).
The rare Masked
Burrowing Crab we found is likely the first sighting for Sentosa.
Fortunately or unfortunately, we had our most significant sighting when
the group had already dispersed. Auntie Gloria noticed a strange ‘unicorn’ crab
barely 3 cm across on a sandy substrate between the rocks. Uncle Marcus
promptly identified it as the rare Masked Burrowing Crab (Gomeza
bicornis). He pronounced that this was likely the first sighting for
Sentosa. The perceived ‘unicorn’ is actually a pair of long antennae joined
together with interlocking hairs. The united antennae are speculated to
form a breathing tube, used when the crab buries itself in the sand with only
the tip of its antennae visible. We were jubilant at this find, a cool lifer
for Auntie Gloria, Uncle Tim and Auntie Lena.
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