10 Fruit Trees of Pulau Ubin 200609

Some RMBR volunteers met up on Saturday morning for an outing to Pulau Ubin cum durian feast. More about that in a later blog post! In this entry, ten fruit trees of Pulau Ubin which we saw will be featured. In horticultural usage, 'fruit tree' refers to a tree whose fruit is used for human consumption. So even though all flowering plants bear fruit, not all are called fruit trees. And 'trees' can be a misleading term...

The first fruit tree that we saw, which, at this time of year, is terribly hard to NOT notice was the Rambutan (Nephelium lappaceum). When I was a kid, I used to be unable to tell the difference between Lychee (Litchi chinensis), Longan (more than one species) and Rambutan. Well, there're all from the same family of Sapindaceae! Even now, I keep thinking that Lychee is Rambutan..and Longan is Lychee..you get the idea. Perhaps the following associations will help:

Rambutan - red and hairy (rambutan, derived from the Malay word rambut which means hairs)

Lychee - red and NOT hairy

Longan - brownish-yellow and NOT hairy

Rambutan trees grow in countries with tropical climates. They are evergreen ie. having leaves all year round. Some trees are dioecious while other are hermaphroditic.

The second fruit tree that we came across was that of the Custard Apple (Annona squamosa) (note: the common name refers to all three species in the genus Annona). This variety hails from the family Annonaceae which grows well in warm, humid climates. According to this website, "[t]here is a thick, cream-white layer of custardlike, somewhat granular, flesh beneath the skin surrounding the concolorous moderately juicy segments, in many of which there is a single, hard, dark-brown or black, glossy seed, oblong, smooth, less than 1/2 in (1.25 cm) long.". I remember eating a custard apple a very, very long time ago and thus cannot remember how it tastes like. Probably was not fond of it which explains why I've not eaten it ever since.

What's a durian feast without durians? In Pulau Ubin, a noticeable number of Durio zibethinus trees grow just along the main trail. When not fruiting, this tree, which hails from the family Malvaceae, can be distinguished by its leaves which have a bronze underside. There are 30 recognised Durio species but the one mentioned here is the variety which is available in international markets.

The durian has long been nicknamed 'the king of fruits'. The ripe fruit has a pungent, distinctive smell and comes in multiple segments. The seeds, found in shallow recesses in each segment, are covered in a soft and custard-like flesh, ranging from cream white to yellow and even red, depending on the species. Apart from the smell, the other distinctive feature is, of course, the husk, which is very prickly. Wallace, a famous naturalist, apparently said that for one to appreciate durian, he or she has to eat it three times. I used to love eating durians back when I was a kid but have since assiduously tried to avoid them (though what possessed me to eat some on Saturday is beyond me...).

Contrary to the title of this blog, the banana (Musa spp.) is not a tree but a herb - the world's largest herb, in fact. Basically, herbs are plants which have non-woody stems. The humble banana (family Musaceae) has its origins in Southeast Asia and over time, with the rapid spread of globalisation, it became well-known to the world. Musa comprises both dessert bananas (what we eat in Singapore) and plantains. The former is eaten raw while the latter has to be cooked or processed in other ways. Plantains have lower water content, making them drier and starchier than fruit bananas. They typically form a staple in the diets of people living in places such as Central America, the Caribbean and Peru.

The picture above shows the main stalks of banana plants which grow from rhizomes underground. In due time (if not already), the terminal inflorescence will grow out from the top of the stalk, and bear fruit. Each stalk produces one huge flower cluster and then dies. New stalks then grow from the rhizome. In summary, the growth of one main stalk is as follows:

Rhizome (produces more than one shoot but most are cut back in order to allow energy to be channelled to fruiting of the main stalk) -> new shoot (typically called a sucker) -> large leaves -> terminal inflorescence -> fruiting (bunch o' bananas) -> main stalk dies -> cycles repeats itself (main stalk forms from a new sucker of the same rhizome)

I was really confused about the whole process of propagation until I chanced upon these sites which can be accessed here and here (good diagram showing the parts of a banana plant). This other website details how the popularity of bananas spread and explains an interesting phenomenon - negative geotropism - which banana plants exhibit.

Hope you aren't suffering from banana overload (like I was). Here are a few more interesting things:

i. fibres are obtained from the stalks which can be made into material (for clothes) and other items such as bags. The pic on the right is a close-up shot of a bag made from banana fibres. It was given out by the Filippino restaurant, 7017 Flavours, on their anniversary. The staff there wear uniforms made from the fibre too.

ii. banana hearts (ie. male banana flowers) are used in dishes like rojak. They look like pink curlicues once cleaned off of gravy.

This pretty pink-streaked flower belongs to the Starfruit (Averrhoa carambola) (family Oxalidaceae).

Here, you can see the developing fruits which still have some way to go before ripening. The common name comes from the appearance of the cross-section of the fruit. It closely resembles a star, with both its (yellow) colour and shape.

Often eating with sour plum powder, the guava (Psidium spp.) (family Myrtaceae) is another fruit that is a favourite with locals. Apart from eating it fresh, guavas are also consumed in their preserved form. Personally, I prefer the preserved ones even though they remind me of curled-up pieces of dead skin (haha!).

When crushed, the leaves of this tree give off, what else, but a guava-ish smell.

I was surprised to see Cacao tree (Theobroma cacao) (family Malvaceae) growing in Pulau Ubin. Didn't think that they grow in this part of the world. Theobroma means 'food of the gods' in Greek, and indeed, processed cacao beans are what gives us cocoa from which the much prized chocolate is made. Each cacao pod contains 20 to 60 seeds (usually called beans). These contain a high percentage of cocoa butter, a fatty substance.

You'd think that with cocoa being so prized and all that everything about the plant must be grand. While flowers of many plants are pollinated by butterflies/moths or bees, cacao flowers are pollinated by...flies. Clearly, flies are not to be looked down upon.

While taking a break from writing this blog entry, I munched on some coconut candy - a sweet confection that is made from grated coconut. Coconut trees (Cocos nucifera) hail from the palm family of Arecaceae (Palmae is now considered taxonomically invalid), and are the only species in the said genus. Nearly everything about them is useful, from the nuts to the leaves.

Coconut palms are often seen growing by the coast for they are dispersed by water. The fruit itself has a hollow cavity that is filled with a liquid commonly called coconut water. The air-filled space allows the fruit to float on the surface of water.

I can't help but think of the Coconut Crabs (Birgus latro) upon the mention of Coconut Palms. These crabs have been observed to crack open coconuts whether by using their chelipeds or climbing up a tree and subsequently dropping the fruit to crack it open. Read more about their behaviour here and here.

This plant here is not a tree, but a climbing vine. The luscious (probably unripe) fruit here is a passion fruit (Passiflora spp.). Not sure if this is the kind that is consumed though. When ripe, the fruit is harvested and the juice, along with the pulp-covered seeds, are used in a variety of ways. In Singapore, it is not uncommon to find bubble tea that is passion fruit-flavoured.

Being a climbing vine, the plant has tendrils which it twines around a support structure. When mature, the evergreen leaves are deeply 3-lobed and finely toothed.

I 'expired' rather quickly that day and left out two other fruits which LK pointed out, namely, the Jackfruit and Nutmeg. After rooting around, I realised that I did have the resources to finish this entry (with a number 11 even), after all :D

Here we go...

Another fruit with a pungent smell is the Jackfruit (Artocarpus heterophyllus). It is the largest tree borne fruit in the world. The leaves are oblong, oval, or elliptic in form, 4 to 6 inches in length, leathery, glossy, and deep green in color. Juvenile leaves are lobed. This tree is commonly planted in and around housing estates. It is closely related to the Cempedak (Artocarpus champeden). Currently, I am not able to differentiate the two... Both hail from the family Moraceae.

Photo taken from nunukphotos.com

I'm not sure which species of nutmeg (family Myristicaceae) the ones found at Pulau Ubin belong to, but if I needed to hazard a guess, it would be Myristica fragrans, which is a commercially viable species.

The seeds are dispersed by big birds (which have bigger beaks and able to swallow larger fruits) like Imperial Pigeons and hornbills. For germination to occur, the seed has to swallowed and passed through the gut of the bird. Only then can the astringent mace (lace-like covering) around the seed be removed. With the dwindling numbers of big birds in Singapore, the nutmeg is suffering.

Nutmeg is used in cooking and baking as a flavouring. The powdered form available in supermarkets is obtained from grating the seeds. The mace is also used. Both impart a similar flavour.

Quite a few of the fruits featured are heaty, such as the Rambutan, Durian, Jackfruit and Cacao. Starfruit is cooling.

To recap, here is a list of the 10 fruits featured:

1. Rambutan (Nephelium lappaceum)
2. Custard Apple (Annona squamosa)
3. Durian (Durio zibethinus)
4. Banana (Musa spp.)
5. Starfruit (Averrhoa carambola)
6. Guava (Psidium spp.)
7. Cacao (Theobroma cacao)
8. Coconut (Cocos nucifera)
9. Passion Fruit (Passiflora spp.)
10. Jackfruit (Artocarpus heterophyllus)
(Additional) 11. Nutmeg (Myristica fragrans)

Semakau, in the Early Morning Light 140309

A couple of days back marked the last of afternoon and evening low tide windows. So, from now till several months along, trips are scheduled for the early morning.

In the wee hours of Saturday morning, dozens of Project Semakau volunteers left their homes in order to reach Marina South Pier by 5 am. We were going to the island to conduct the first transect survey.

It was still dark when we got to the pier and similarly when the ferry reached Semakau.

As transport is not provided at such an early hour, we had to walk to the intertidal zone from the visitor centre. The early morning air was cool and punctuated with bird calls, as our diurnal feathered friends slowly awoke from their slumber.

In no time, we had walked through the secondary forest and reached the intertidal area. At the beginning of the seagrass meadow, we had an encounter with...

...an unknown sea hare (Order Anaspidea).

Wen Qing, Samuel and myself were in seagrass transect team 2. While doing the survey, we saw plenty of seagrass in the 30 m stretch (but not as much as before like during the transect training) and also some interesting things like the mucus coating made possibly by a wrasse (Family Labridae) or some other kind of fish [edit]. One interesting fact about wrasses is that they can change their gender! O.O

Seagrass is indeed tricky as we soon realised for ourselves...

1) Thalassia hemprichii.

According to the ID sheet, the leaves have "short, black bars of tannin cells". But as you can see, these bars aren't obvious at all. This is a good example of how things in the field often differ from what is on paper... So how to ID Thalassia? Though their sickle-shaped leaves are a good giveaway, if unsure, it's best to feel for their rhizomes which are scarred and appear reddish-brown :)

2) Cymodocea serrulata.

Often confused with Enhalus acoroides and Thalassia hemprichii, this species does have one visible distinguishing feature - a serrated leaf edge! If that does not help, feel for the rhizomes, which are smooth and closer to the surface than Thalassia.

3) Halodule uninervis.

We didn't think we'd encounter this species, so we had to confirm its ID with Ron. The above is a young specimen. It has a white rhizome with black scars. In mature specimens, a distinctive centre vein is visible, and leaf tips have three distinct points.

Mostly, there was a lot of Tape Seagrass (Enhalus acoroides), noticeable numbers of Syringodium isoetifolium (Noodle Seagrass), some Cymodocea serrulata (Serrated Ribbon Seagrass), a little of Halophila ovalis/minor (Spoon Seagrass), even less of Thalassia hemprichii (Sickle Seagrass) and only one quadrat with Halodule uninervis (Needle Seagrass). For more info, visit the I.D. Seagrass page of the Seagrass-Watch website :)

After completing the transect survey, we were given some time to explore. One group followed Ron, while the other followed July. Saw this Sandfish Sea Cucumber (Holothuria scabra) soon after heading out.

There were numerous juvenile Knobbly Sea Stars (Protoreaster nodosus) out that day! Yay! They really come in a myriad of colours. As echinoderms have a water vascular system, they will get stressed and die if left out of water for too long. That's why we always replace them after a quick photo.

Knobbly no. 1.

Underside of Knobbly no. 1

Knobbly no. 2. One of its arms is slightly shorter than the rest which could be a result of an injury and subsequent regeneration.

Knobbly no. 3.

Underside of Knobbly no. 3, with focus on its mouth (centre) and the ambulacaral areas which house its tube feet.

Knobblies no. 4 and 5. The Knobbly on the left looks really 'juvenile' (but that's just my opinion).

Knobbly no. 6. With two of its arms closer than normal to each other, this sea star here looks like it's getting ready to dance.

Saw a few more Knobblies, but didn't upload all the pics here.

Growing in bunches were some green algae (Caulerpa sp.).

This is a first for me! In one of the tidal pools, this Heart Cockle (Corculum cardissa) was clearly visible in the shallow and clear water. When it dies, the heart breaks...

An Orange-edged Black Flatworm (probably Pseudobiceros uniarborensis). Another 'first' for me on Semakau.

Looking like a protrusion from the substrate was this Common Hairy Crab (Pilumnus vespertilio). The hairs on its body trap sediment which, over time, allows it to look like a piece of the substrate itself.

A view of the coral rubble area.

Growing in between this magnificent Staghorn Acropora Coral (Acropora sp.) was a fan shell (Family Pinnidae).

Hmm..egg cases of a mollusc? It's likely an egg ribbon of a nudibranch or some other species of slug.*

This sea cucumber (Actinopyga sp.) is thought to be a juvenile Stonefish Sea Cucumber due to similar physical traits, but that is based on speculation and not yet confirmed*.

This is by far the smallest Noble Volute (Cymbiola nobilis) that I have seen. Is it a juvenile? From its shell alone, I wouldn't have been able to ID it as the typically associated 'mountain ranges' pattern is absent. Lucky its black with orange spots muscular foot was showing.

Saw a lot of these Common Sea Stars aka Sand-sifting Sea Star (Archaster typicus). Here is a pair getting ready to mate with the male on top (such pairing behaviour is known as pseudocopulation) [edit]. Like other sea stars, external fertilisation takes place (meaning reproductive organs don't actually meet).

References:

Wild Fact Sheets of marine life on Singapore shores - http://www.wildsingapore.com/wildfacts/

Acknowledgements:

[edit], *Thanks to Ron for the corrections and IDs!

The Sun Blazes Down on Semakau 080309

Remember how in primary school there were a couple of 'standard' phrases used in writing compositions? I've never been a fan of them but if there ever was a time to use one, it would be to describe the weather on Sunday. So here goes:

The sun beat mercilessly down on us...(haha!). After doing battle with the mozzies (they love me but the feeling isn't mutual) in the forest trail, we finally arrived at the intertidal area. Split into 2 groups, Wen Qing, Nonis, Xiu Li and myself followed Luan Keng while Hui Yi, Ying Wei and Elvin had Ron as their leader. We were there to pile in the transect markers for the upcoming transect this Saturday. As we headed out...

...LK spotted this Mangrove Horseshoe Crab (Carcinoscorpius rotundicauda). Two species can be found in Singapore - the one above as well as the Coastal Horseshoe Crab (Tachypleus gigas). Two easy indicators to look out for are colour and tail structure. The mangrove species is brownish with a rounded tail while its coastal relative is greyish with spines on its tail. Read more about horseshoe crabs in general here, and the 2 species that can be found in Singapore here.

Kinda seemed apt that the first animal spotted was a horseshoe crab, for on that very day in the evening, a Horseshoe Crab Population & Distribution Survey was conducted around the mainland, organised by the Nature Society (Singapore). I sure hope that minimal damage was incurred for volunteers had to dig up (a lot of) mud in order to locate the horseshoe crabs...

After crossing the seagrass meadow, we entered the coral rubble/coral reef area where two huge pore corals (Porites sp.)* caught our attention with their different colouration.

Sadly, the top of both corals are dead and the scorching sun didn't help matters.

After piling in the transect markers, we had some time to explore. Hunter-seekers who arrived before everyone else found this synaptid sea cucumber (Family Synaptidae) and marked out its location.

Another find by the hunter-seekers was this Noble Volute (Cymbiola nobilis) and its eggs. Was amazed to see that the mass of eggs it laid was as big as it was. Its shell kind of looked faded to me, compared to the previous ones I'd seen at Changi before. Also, it was smaller. Size can't be used to judge its maturity, I realised.

A dead octopus (Class Cephalopoda, Order Octopoda).* Wen Qing's close examination of it revealed that some of its tentacles were shorter than the others. We learned from one of the visitors that tentacles can get bitten off by predators and are subsequently regenerated. Cool!

Bakaus (Rhizophora spp.) greet visitors to the Semakau intertidal area. Learned that 2 species can be found growing on the edges of the sandy shore - R. apiculata and R. stylosa.

Though both species look similar, they can be told apart even at a distance by their roots. Both mangroves have stilt or prop roots, but those of R. apiculata are not so spread out as compared to that of R. stylosa. In addition, the stipule^ of the former is red while that of the latter is yellow. The stipule wraps over the apical bud, protecting it. The red stipules will eventually drop off as the young leaves grow.* Can you tell which picture is of which species? One last thing to note, R. apiculata has a shorter flower stalk than R. stylosa.

Another Rhizophora species, R. mucronata has big leaves which distinguish it from the two above.

Taking one last look at a Rhizophora stylosa before we leave.

Some other things seen but not photographed:
i. Mosaic Crab (not too sure...it ducked for cover really quickly so I only caught a glimpse)

ii. Crab with yellowish-brown carapace (ditto the above)

iii. Black-lipped Conch

iv. Sand-sifting Sea Star aka Common Sea Star

v. Ovum Cowrie

vi. Eagle

Heard about the sightings of Knobbly Sea Stars and turtles from Ron but didn't get to see them D:

Acknowledgements:
Thanks to LK for the info! And to everyone for the company :)

*Ron, thanks for the corrections!

^Thanks to Anonymous for bringing my attention to the terms used (ie. stipule and apical bud)! [Refer to Anonymous' comment]

Notes:

Given the weather, a cap and a lot of water are essentials!

For other takes on the trip, check these entries out:

i. Ron's - http://tidechaser.blogspot.com/2009/03/scorching.html

ii. July's - http://wherediscoverybegins.blogspot.com/2009/03/discover-semakau-landfill-island-8.html

iii. Samson's - http://mantamola.blogspot.com/2009/03/semakau-tidal-walk-8-march-09.html

iv. Meiyi's - http://appreciateandlove.blogspot.com/2009/03/semakau-after-so-long.html

v. Eunice's - http://naturallyours.blogspot.com/2009/03/48-semakau-guiding-w-meiyi-giant-clams.html