Rusty trees around you?!

One of the things that strike me ever since I came to Singapore is that it is truly a Garden City. ” No roads has been left uncovered and no vacant land within the city left unplanted with shrubs ( W.Y.Chin and C.Richard, 1986).” Thanks to those big trees on campus I am able to survive the intense heat of the sun. There is one interesting feature on the tree that you might have observed before as well.

P1020148A "rusty" tree I saw on the way to Science Faculty. Taken outside Raffles Hall.

Above: An algae covered tree in PGP Residences. Below: “Rusty” trees seen outside Raffles Hall of Residences.

 Take a good look on the trees, some of them have brownish orange patches on the bark. Some of the patches are so extended that the whole trunk actually look orange! It certainly is not the plant pigmentation as it appears on different species of trees and trees of the same species do not necessarily possess this feature. So the first though that crossed my mind was: ” can trees actually get rusty….?”
 

After a closer examination, the orangy stuffs that look powdery from far, actually appear to be quite rough. Some patches looks like a rough orange carpet covering the bark, while some looks somehow like overcompressed breadcrumbs. Now it looks like some fungus or lichen. Since this question has been bugging me, I decided to find out the identity of the rusty patches. 

Closed up: lichen-like green algae (Trentepohlia sp.) on a tree bark

Closed up: lichen-like green algae (Trentepohlia sp.) on a tree bark

So…. It appears that the rusty orange patches are actually green algae! It’s not uncommon that algae lives attached to the trees, but what surprised me more was that it is actually classified under GREEN algae! Green algae, phylum Chlorophyta, now belongs to a well-established monophyletic group, Viridiplantae, in which the terrestrial plants are also included. This species of green algae comes from the order Trentepholiales and the genus of filamentous green algae,  Trentepohlia. Algae under this order are usually subaerial algae which are adapted to live on substratum like natural rocks, concrete walls, plastic nets, tree barks, fruits and leaves (Rindi F. et.al., 2009). Some of the algae under this order are actually lichenised-algae. Trentepholiales attached to the subtrata via filamentous hyphae and reproduce via spores.

 

Closed up: rough crust-like Trentepohlia carpet on a tree trunk.

Closed up: rough crust-like Trentepohlia sp. carpet on a tree trunk.

Now why is it in the same family as the green algae while it appears to be orange? Algae of order Trentepohliales produce large amount of carotenoids (which is also a component of chlorophyll), such as beta carotenoids and haematochorome. These pigments gave the algae their charateristic bright yellowish orange or red colouration. Trentepohlia sp. is well distributed across the humid tropic region.

Since the algae has chlorophyll pigments hence the ability to photosynthesize and the host plants do not show any signs of malnutrition or being parasited, the interactions of these green algae with the tree most probably are commensalism. While for non-living substrata, I was thinking that it too, merely serve as a host. However, these green algae actually post problems to substratum like the concrete wall. Pigments produced by Trentepholia sp. caused local erosion like pitting and discoloration of wall when present as biofilm (Gaylarde P. et.al., 2006).  

Okay, doubts cleared. Hopefully next time when you stumble across some trees with strage orangy trunks, you will know that it is actually algae growings instead of rust !

 

References:

Hugh, T.W.Tan et.al.,2007,  The Natural Heritage of Singapore 2nd Edition. Prentice Hall, Pearson Education, South Asia Pte. Ltd. Singapore.

Corlett, R. and Chin W.Y., 1986, The City and The Forest: Plant Life in Urban Singapore. Singapore University Press, National University of Singapore.

Rindi F. et.al., 2009, An Overview of The Biodiversity and Biogeography of the Terrestrial Green Algae, Nova Science Publishers, Inc. http://bama.ua.edu/~dwlam/index_files/Rindi_Biodiversity%20hospots_PC.pdf (retrieved 10th April 2010)

Gaylarde P. et.al., 2006, Lichen-like colonies of pure Trentepohlia on limestone monuments, Elsevier Ltd. http://www.sciencedirect.com.libproxy1.nus.edu.sg/science (retrieved 10th April 2010)

Trentepohlia, Wikipedia.http://en.wikipedia.org/wiki/Trentepohlia (retrieved 14th April 2010)

Nemo’s crib

Have you ever wondered how does Nemo‘s crib looks like? Here it is!

Giant carpet anemone

Giant carpet anemone - picture taken at Pulau Semakau

Underside of the giant carpet anemone

Underside of the giant carpet anemone - picture taken at Pulau Semakau

The giant carpet anemone, Stichodactyla gigantea, are commonly found in the shallow intertidal sand flats of Singapore’s southern shores. Usually growing up to 50cm in diameter, the S. gigantea is an opportunistic predator and scavenger.(R.Tan, 2009) It is capable of stinging and devour any fishes or invertebrates when brushed against its tentacles containing cnidocytes.(MarineBio.org, 2010) However, it also forms symbiotic relationship with other organisms such as zooxanthellae and false-clown anemonefish, generally the Amphiprion spp.

The False-clown anemonefish, Amphiprion ocellaris, is often seen to be associated with the giant carpet anemone in Singapore.(R.Tan, 2009) It resembles closely to the TRUE clownfish, Amphiprion percula, except that Percula has only 10 dorsal-fin spines while Ocellaris have 11.(MarineBio.org, 2010) Moreover, they also can be differentiated by their iris whereby Percula has orange iris that make their eyes look smaller and Ocellaris have orange-grey iris and make their eyes look bigger.

Amphiprion ocellaris

Amphiprion ocellaris - picture taken by Bictures, from photobucket

Amphiprion percula - taken by Jordan-to, from photobucket

Amphiprion percula - taken by Jordan-to, from photobucket

The interaction between A. ocellaris and S. gigantea is a form of mutualistic relationship whereby both parties benefit from one another. The S. gigantea provides the A. ocellaris and its clutch a shelter and protection from predators while the A. ocellaris provides protection to S. gigantea by chasing away anemone-eating fishes such as butterflyfish.(MarineBio.org, 2010) Moreover, A. ocellaris also helps to groom S. gigantea by getting rid of parasites and debris.(B. Berends, 2007) Furthermore, A. ocellaris indirectly provides a food source by luring fishes into the anemone or to excrete nitrogenous wastes for the photosynthetic zooxanthellae, which is an endosymbiont of the giant carpet anemone that shares the products of photosynthesis with its host. (E. Truelove, 2008)

References

E. Truelove. (2008). Mutualism between clownfish and anemone: Following my research at college of William & Mary. Retrieved on 14 April 2010, from http://clownfishandseaanemones.blogspot.com/

B. Berends. (2007). Interactions with other species. Retrieved on 14 April 2010, from http://bioweb.uwlax.edu/bio203/s2007/berends_bets/interactions.htm

Amphiprion ocellaris, Clown Anemonefish – MarineBio.org. Retrieved on 15 April 2010, from http://marinebio.org/species.asp?id=29.

R. Tan (2009) WILD Fact Sheets: Giant carpet anemone. Retrieved on 14 April 2010, from http://www.wildsingapore.com/wildfacts/cnidaria/actiniaria/gigantea.htm

Sponge Crab and ‘Spongetop’

While looking for organisms at the Labrador Rocky Shore, I was amazed by a little crab with a big sponge on top-Sponge Crab (Cryptodromia tuberculata).

The Sponge Crab that we saw at Labrador: Cryptodromia tuberculat

The Sponge Crab that we saw at Labrador Rocky Shore (Photo Courtesy of Pei Shuan)

These crabs usually have an ability to shape a living sponge into a cover especially at night when it is safer. They use their pincers to cut and trim the sponge to fit into their carapace, and then use their modified hind legs which bends over its back to carry the sponge cap over their dorsal surface (Wicksten, 1993). In some cases, the sponge is made bigger than the carapace, so that the crabs do not have to change the sponge when it decays or when the crabs moult (McLay, 1983).

 

An Unidentified Sponge Crab spotted at Pulau Sekudu (Photo courtesy of Hnerietta Woo)

An Unidentified Sponge Crab spotted at Pulau Sekudu (Photo courtesy of Henrietta Woo)

 

The sponge crab and its sponge have an interesting interaction. The sponge provides food and shelter for the crab to protect it against unfavourable conditions like currents (McLay, 1982). It also serves as a camouflage from predators (Wicksten, 1985), allowing it to blend in with the surrounding and thus escape from predators. Some sponges also secrete secondary metabolites as a defence against predation on them (Bell, 2008). These chemicals have a foul smell which may help to confer defence for the crab too.
As the sponges are sessile, they can benefit from this relationship when the crab moves them around. They may obtain more food through filter feeding and need not compete for living space when in other areas. As the crabs are specific in the type of sponge species they use, they can help in the selective asexual propagation of the sponge when they move around (McLay, 1983).

 

An Unidentified Sponge Crab spotted in Beting Bronok, Singapore. (Photo courtesy of Henrietta Woo)

An Unidentified Sponge Crab spotted in Beting Bronok, Singapore. (Photo courtesy of Henrietta Woo)

This association somehow benefits both parties, and when they are separated, the sponge can still survive by itself. As for the crab, if possible, it may utilise ascidians (sea squirt) such as those from Polycarpa sp. (McLay and Peter, 2007), or even  a rubber flip flop, otherwise, it can hide under the reefs. Thus, the relationship is likely to be facultative mutualism based on this. However, what happens in the long term if the crab really cannot find any cover?

 

References

Bell, J.J. (2008), The functional roles of marine Sponges, Esturine, Coastal and Shelf Science, 79(3):341-353.

McLay, C.L. (1982), Population biology of the Sponge Crab Cryptodromia hilgendorfi (Dromiaeea) in Moreton Bay, Queensland, Australia, Marine Biology, 70: 317-326.

McLay, C.L. (1983), Dispersal and use of sponges and ascidians as camouflage by Cryptodromia hilgendorfi (Brachyura: Dromiacea), Marine Biology, 76: 17-32.

McLay, C.L. and Peter, K.L.N. (2007), Revision of the Indo-West Pacific Sponge Crabs of the Genus Petalomera Stimpson, 1858 (Decopoda, Brachyura, Dromiidae), The Raffles Bulletin of Zoology, 55(1):107-120.

Wicksten, M.K. (1985), Carrying behaviour in the Family Homolidae, Journal of Crustacean Biology, 5(3):476-479.

Wicksten, M.K. (1993), A review and model of decorating behaviour in Spider Crabs (Decopoda, Brachyura, Majidae), Crustaceana, 64(3):314-325.

“Sponge Crab” by Cristian M. DeviantART, 09 October 2008. URL: http://cristian-m.deviantart.com/art/Sponge-Crab-40D0000793-100246309 (accessed on 11 April 2010

“No, I’m not an egg, nor a seed!”

“Seeds of Sweet Granadilla,” by Chrisbliss. SugarHead, 13 may  2010.

“Seeds of Sweet Granadilla,” by Chrisbliss. SugarHead, 13 may 2010. URL: www.sugarheadblog.com/blog1/2008/05/13/ (accessed on 14 April 2010).


They look alike, don’t they?

“Female (left) and Male (right) Vargula hilgendorfii,” by Abe Laboratory. Source of Wonder, 29 September 2003.

“Female (left) and Male (right) Vargula hilgendorfii,” by Abe. Source of Wonder, 29 September 2003. URL: http://umiho.net/efiles/1umiho.html (accessed on 14 April 2010).

At first glance, one would presume this to be an egg or maybe the seed of the sweet granadilla. But no, this is the Vargula hilgendorfii (in Japanese “umi-hotaru”), literally means sea-firefly (Abe, 2003). Formerly known as Cypridina hilgendorfii, this marine luminescent ostracod is found at the Pacific coast of central Japan (Vannier et. al., 1993).

Defined by a transparent bivalve carapace and a soft body within, consisting of 7 specialised pairs of appendages (Abe, 2003), this completely nocturnal ostracod behaves as predators of living prey such as polychaete annelids (for instance, sandworm), and as opportunistic scavengers on dead animals such as fishes and squids (Vannier et. al., 1998).

“Vargula hilgendorfii Feeding on Sandworm,” by Abe Laboratory. Source of Wonder, 29 September 2003.

“Vargula hilgendorfii Feeding on Sandworm,” by Abe. Source of Wonder, 29 September 2003. URL: http://umiho.net/efiles/1umiho.html (accessed on 14 April 2010).

Located on the upper lip region is a yellow luminescent organ which emits the blue light seen as a spiral-pattern emission during a “courtship dance” (Vannier et. al., 1993). However, it has been observed that most males exhibit luminescence to threaten predators such as the striped eel catfish, stinging eel catfish, blue swimming crab and three-spot swimming crab, rather than for courting females (Henmi et. al., 2002). In this defence mechanism, luciferase reacts chemically with luciferin substrate when released into the seawater, emitting a blue light in the process that distracts approaching predators (Katsumi et. al., 2000).

 “Luminescence of Vargula hilgendorfii,” by J. Day After Day, East of Sun, West of Moon, 12 October 2004.

“Luminescence of Vargula hilgendorfii,” by J. Day After Day, East of Sun, West of Moon, 12 October 2004. URL: http://sun-moon0.blog.drecom.jp/monthly/200410/ (accessed 14 April 2010).

Watch a video on Vargula hilgendorfii Electric Stimulation,” by Ostraking. YouTube Channel, 6 July 2009. URL: www.youtube.com/watch?v=nXaMC9LVG04 (accessed 14 April 2010).

Besides predation, the V. hilgendorfii is also often inhabited by small crustacean ectoparasites, for instance Onisocryptus ovalis (Vannier et. al., 1993). Researchers Vannier et. al. (1993) observed that these parasites cling on to the dorsal region, close to the heart of the V. hulgendorfii. This preferential location might be due to the seventh limbs (cleaning appendages) of V. hulgendorfii reaching this site less often, and hence, a lower chance of them being dislodged (Katsumi et. al., 2004). Vannier et. al. (1993) research also revealed that the flattened and arcuate appendages of the O. ovalis seemed to have adapted to the ectoparasitic lifestyle and the morphology of its host. However, the V. hulgendorfii do not seem to remove these parasites even though they are feeding on the food debris off the host body surface or tissue fluid excretion.

“Vargula hilgendorfii female with eggs in ovaries and parasite Onisocryptus ovalis on dorsal part of ostracode body,” by Vannier. The Crustacean Society, 1 February 1993.

“Vargula hilgendorfii female with eggs in ovaries and parasite Onisocryptus ovalis on dorsal part of ostracode body,” by Vannier. The Crustacean Society, 1 February 1993. URL: http://www.jstor.org.libproxy1.nus.edu.sg/stable/pdfplus/1549122.pdf (accessed 14 April 2010).

These parasites might just be establishing a symbiotic relationship of commensalism with the V. hulgendorfii. However, what is more significant and certain is that, the V. hulgendorfii functions as an important nutrient recycler in the marine ecosystem (Vannier et. al., 1998).

References:

Henmi, Y., Izuno, R., Okamoto, N., Kawada, K., 2002. Distribution and behaviour of the marine luminescent ostracod Vargula hilgendorfii. Japanese Journal of Benthology, 57: 21-27

Katsumi, A., Jun., H., 2004. Reproductive strategy of an isopod Onisocryptus ovalis, parasitizing a bioluminescene myodocope ostracod Vargula hilgendorfii. Hydrobiologia, 419(1): 191-196.

Katsumi, A., Takuo, O., Koshi, Y., Nasono, Y., Kyosuke, I., 2000. Multifunctions of the upper lip and a ventral reflecting organ in a bioluminescent ostracod Vargula hilgendorfii. Hydrobiologia, 419(1): 73-82

“Sea-firefly,” by Ade. Source of Wonder, 29 September 2003. URL: http://umiho.net/efiles/1umiho.html (accessed on 14 April 2010).

Vannier, J., Katsumi, A., 1993. Functional morphology and behaviour of Vargula hilgendorfii (Ostracoda: Myodocopida) from Japan, and discussion of its crustacean ectoparasites: preliminary results from video recordings. Journal of Crustacean Biology, 13(1): 51-76.

Vannier, J., Katsumi, A., Kyosuke, I., 1998. Feeding in myodocopid ostracods: functional morphology and laboratory observations from videos. Marine Biology, 132(3): 391-408.

If He Who Laughs Last, Laughs Best…

…then laughing round the clock must be most satisfying!

Or not.

There’s at least one Collared Kingfisher (Todiramphus chloris) around my block who laughs its heart out during the day, sometimes even at 2.00 a.m.! Have these diurnal birds suddenly developed a penchant for a nocturnal lifestyle? If not, what could be the cause of their activity at night?

Collared Kingfisher (Todiramphus chloris) at Changi Beach

Collared Kingfisher (Todiramphus chloris) at Changi Beach (own photo).

Light pollution, it seems. It never gets completely dark in urban areas of Singapore thanks to the multitude of streetlights. Apart from increased activity, birds may also be induced to feed into the night, disrupting their normal circadian rhythm. Life cycles could be impacted as well. In a study done on European Blackbirds (Turdus merula), breeding occurred earlier and finished later for urban-dwellers as compared to those in rural habitats (Coppack & Pulido, 2004).

However, it is not only diurnal birds that are affected. In the case of nocturnal migrants, navigation is done by using the moon and stars. Disorientation is inevitable with light pollution, and birds may end up crashing into buildings (Guynup, 2003).

On the other hand, daytime noise may also be keeping the Collared Kingfisher awake at night. Traffic during the day contributes to ambient noise with which birds must compete with when they communicate by calling. Urban European Robins (Erithacus rubecula) compensate for daytime noise by singing in the same areas at night. The same study also found that daytime noise had a greater effect on nocturnal singing than light pollution did (Fuller et al., 2007). However, kingfishers are not songbirds, so light pollution may affect them more…or it could be a whole different ball game altogether. The fact that these kingfishers only increased in range to urban areas in recent times (Tan, 2001) could explain why they seem to be the only ones calling at night – the others are already used to nights in semi-darkness.

Turn off those lights!

References

“Light Pollution Singapore,” by S. C. Chan, 2005. URL: http://lightpollutionsg.tripod.com/ (accessed 14 April 2010).

Coppack, T. & F. Pulido, 2004. Photoperiodic response and the adaptability of avian life cycles to environmental change. In A. P. Moller, W. Fiedler & P. Berthold (Eds.), Birds and climate change (pp. 131-147). Oxford: Elsevier Ltd.

“Collared Kingfisher,” by David Farrow. Xeno-Canto, 10 January 2006. URL: http://www.xeno-canto.org/sounds/uploaded/RNVWOVLEUN/collaredkingfishercallslwsiFarrow.mp3 (accessed 14 April 2010).

Fuller, R. A., P. H. Warren & K. J. Gaston, 2007. Daytime noise predicts nocturnal singing in urban robins. Biology Letters, 3: 368-370.

“Light pollution taking toll on wildlife, eco-groups say, ” by S. Guynup. National Geographic News, 17 April 2003. URL: http://news.nationalgeographic.com/news/2003/04/0417_030417_tvlightpollution.html (accessed 14 April 2010).

“Collared Kingfisher,” by R. Tan. Naturia, 2001. URL: http://www.naturia.per.sg/buloh/birds/Halcyon_chloris.htm (accessed 14 April 2010).

Second source

Fuller, R. A., P. H. Warren & K. J. Gaston, 2007. Daytime noise predicts nocturnal singing in urban robins. Biology Letters, 3: 368-370.

Invisible bed partners!

We all sleep with parasitic invisible bed partners’  every night! (Unfortunately, it’s not Edward Cullen!)

For some of us the consequences of this action is very dire – allergies in various forms such as itching, sneezing, inflamed or infected eczema, reddening eyes and even runny nose!

The culprit: dust mites!

Dust mite!

Dust mite! courtesy of wikipedia

Dust mites belong to the genus Dermatophagoides, which means “skin eater.” (Allergo,2010) They feed on animal material with high protein content especially dead human skin cells. The two common species throughout the world that are also allergenic are the Dermatophagoides pteronyssinus and Dermatophagoides farinae . In the context of tropical environments like Singapore, there is a third species called Blomia tropicanis.(Allergo,2010) However it is a misconception that it is the dust mites which are responsible for allergic reactions experienced by people. In fact, it is the droppings as well as the broken up exoskeleton which contains the antigen which triggers the allergy!

An experiment was conducted to determine the profiles of Dermatophagoides pteronyssinus and Blomia tropicanis sensitization among Singaporean and Malaysian subjects. It was revealed that “dual sensitization to B.tropicalis and D. Pteronyssinus is common in the general populations of Singapore and Malaysia. Sensitization to B.tropicalis was more prevalent than to D. Pteronyssinus. (Yeoh,2003)

The most prevalent mite species and allergen vary geographically, between homes within geographical region and even among areas in a home. The key factor that influences mite survival and prevalence is “relative humidity.” (Arlian,2007) Dust mites thrive best where relative humidity is above 70% RH and temperature above 23oC.(Allergo,2010) On average ,Singapore’s humidity level is about 89% RH.(Wunderground,2010) and therefore tends to be a hotspot for the dust mite population.

Having been personally afflicted with allergy to dust mites, I am continually assaulted every time I go to bed or even play with plush toys.

Dust mites have robbed my childhood!

“Dust mites,” by Allergo healthcare,1999-2010

URL: http://www.allergy.com.sg/dustMites.html#What2 (accessed on 14 April 2010)

“Singapore, Singapore,” by Weather Underground,Inc, 2010

URL: http://www.wunderground.com/global/stations/48698.html (accessed on 15 April 2010)

Arlian, Morgan , Neal, Dust mite allergens: Ecology and distribution in Current Medicine Group LLC, VOL 2,NO.5 , September 2002

URL: http://www.springerlink.com/content/cg02121p48530856/ (accessed on 15 April 2010)

S.M. Yeoh, I.C. Kuo Sensitization Profiles of Malaysian and Singaporean Subjects to Allergens from Dermatophagoides pteronyssinus and Blomia tropicalis International archives of Allergy and Immunology VOL 132, NO 3, 2003

URL:http://content.karger.com/ProdukteDB/produkte.asp?Aktion=ShowFulltext&ProduktNr=224161&Ausgabe=229729&ArtikelNr=74302(accessed on 15 April 2010)

Look closely, the caterpillar isn’t dead.

Caterpillar (to ant): Hey, let’s make a deal. If I supply you with food, will you give me protection against predators?

qwerty

Studies have shown that certain species of butterfly larvae (in particular Family Lycaenidae) are involved in food-for-protection mutualistic relationships with ants. This is termed myrmecophily, or the positive interspecies association between ants and butterflies. (Khew SK, 2010).

How does it work? Many lycaenid caterpillars possess a suite of anatomical structures for maintaining relations with ants. Nutritious secretions produced by certain lycaenid caterpillars are consumed by particular ants, which then protect the caterpillars from parasitism and predators (Pierce, 2002). Because caterpillars do not automatically pass honeydew, they must be stimulated to secrete droplets and do so in response to ant antennation (the drumming or stroking of the caterpillar’s body by the ants’ antennae) (Fiedler et al., 1996). Some caterpillars possess specialized receptors that allow them to distinguish between ant antennation and contact from predators and parasites, and others produce acoustic signals that agitate ants, making them more active and likely better defenders of the larvae (Fiedler, 1991).

The enemy-free space that ants can provide for lycaenids is significant: one experiment conducted by Pierce and colleagues in Colorado demonstrated that survival rates of G. lygdymus larvae declined 85-90% when ant partners were excluded (Fraser et al., 2001). However, ant-tended individuals were observed to reach smaller adult sizes than non-tended individuals due to the costs of appeasing ants during the larval stage (Pierce et al., 2002).

Adult females of many lycaenid butterflies also preferentially oviposit on plants where ant partners are present, possibly by using ants’ own chemical cues to locate sites where offspring will likely be tended by ants (Fiedler, 1991).

Finally, while most widely documented in Lycaenid butterflies, many other lepidopteran species are known to associate with ants, including moths.

References:

Fiedler K, Holldobler B. & Seufert P., 1996. “Butterflies and ants: The communicative domain,”. Cellular and molecular life sciences, vol. 52, 1996, pp. 14-24.

Fiedler K., 1991. Systematic, evolutionary, and ecological implication of myrmecophily withing the Lycaenidae. UND Museum Alexander Koenig: Bonner Zoologische Monographien.

Fraser A. M., Axen A. H., and Pierce N. E., 2001. “Assessing the Quality of Different Ant Species as Partners of a Myrmecophilous Butterfly,” Oecologia, vol. 129, Nov. 2001, pp. 452-460.

Pierce N.E., Braby M. F., Heath A., Lohman D. J., Mathew J., Rand D. B., and Travassos M. A., 2002. “The ecology and evolution of ant association in the Lycaenidae (Lepidoptera),” Annual Review of Entomology, vol. 47, 2002, pp. 733-771.

“Mergers, Partnerships & Betrayals”, by Khew SK. Butterflies of Singapore (21 Mar 2010). URL: http://butterflycircle.blogspot.com/2010_03_21_archive.html (accessed on 15 April 2010)

Images

“DSC04241,” by Henry Koh. Flickr, 8 June 2008.  URL: http://www.flickr.com/photos/henrykoh/2560311167/ (accessed on 14 Apr 2010).

“A Quiet Afternoon @ MNT Boardwalk,” by Frederick Ho. Beauty of Fauna and Flora in Nature, 15 Jan 2010.  URL: http://peacockroyal.blogspot.com/search?updated-max=2010-02-20T21:05:00%2B08:00&max-results=8&reverse-paginate=true (accessed on 14 Apr 2010).

Don’t step on that sponge!!!

Pics taken courtesy of McGizmo. Retrieved on 15Apr 2010 from http://www.candlepowerforums.com/vb/showthread.php?t=240253

 

A few weeks ago while I was on an excursion trip to Labrador rocky shore with my NUS mates, I happened to stumble upon this weird-looking crab with a sponge on it. I was initially taken aback by the movement of this sponge because as everyone knows, sponges are sessile creatures. After some clarification from our TA who is like a walking ecological dictionary to us, we came to know that it was actually a sponge crab.

 

The sponge crab holds a living sponge on top of its shell to keep itself hidden. Carrying a sponge on their backs makes these crabs look somewhat hilarious but it is actually an effective form of protection for them. The camouflage provided by the sponge makes their detection much more impossible unless they move.

 

It has been known that sponges also provide camouflage to a range of other organisms besides crabs (McClay, 1983). These sponges also benefit by constantly being on the move, avoiding overcongestion and dessication during low tides (Wulff, 2006) Interestingly, it has been found that several factors dictate the selection and growth of sponges on crab carapaces. These include the nutritional quality of the sponge which might act as a food source, its longevity, decay rate, structural integrity and presence of secondary metabolites to deter predators. (Woods & Page, 1999)

 

It seems that even non-human species choose their ”life partners” based on so many criteria! Nevertheless, there is one thing that still bugs me. The sponge lookalike feature of this crab does not actually deter me from accidentally trampling on it. In fact, its excellent camouflage would count against its survival if Labrador shore is populated with people who are less observant!

 

Wulff, 2006 J.L. Wulff, Ecological interactions of marine sponges, Canadian Journal of Zoology 84 (2006), pp. 146–166.

 McClay, 1983 C.L. McClay, Dispersal and use of sponges and ascidians as camouflage by Cryptodromia hilgendorfi (Brachyura, Dromiacea), Marine Biology 76 (1983), pp. 17–32.

Woods and Page, 1999 C.M.C. Woods and M.J. Page, Sponge masking and related preferences in the spider crab Thacanophrys filholi (Brachyura: Majidae), Marine and Freshwater Research 50 (1999), pp. 135–143.

Bats, not as bad as you think.

To many, bats are dirty, scary and mysterious while to the fruit farmers, fruit bats are persecuted as pests for the damage they do to their yield. All of these have rendered bats to be among the most hated and most feared animals in the world, hiding under a bushel the importance of fruit bat as a seed-dispersal agent.

The most commonly found fruit bat in Singapore is the Lesser Short-nosed Fruit Bat, Cynopterus brachyotis (Phua, P.B. and Corlett, R.T., 1989). Bearing a dog-like face with large eyes, it is also widely known as the Lesser Dog-faced Fruit Bat (Wild Fact Sheets, 2008). In Singapore, you can find them almost anywhere, ranging from coastal areas, forests, riverside to urban areas (Phua, P.B. and Corlett, R.T., 1989). According to Phua and Corlett (1989), the Lesser Short-nosed Fruit Bat (Cynopterus brachyotis) is a very important seed-dispersal agent for the Tiup-tiup (Adinandra dumosa), which is the dominant species in the secondary forest adjoining to National University of Singapore (NUS) (Phua, P.B. and Corlett, R.T., 1989).

Leeser Dog-faced Fruit Bat

Lesser Dog-faced Fruit Bat (Cynopterus brachyotis) ( From "A Guide to Mangroves of Singapore")

Flowering Tiup tiup (Adinandra dumosa)

Flowering Tiup tiup (Adinandra dumosa) (From Flickr)

With Tiup-tiup (Adinandra dumosa), the Lesser Short-nosed Fruit Bat (Cynopterus brachyotis) establish a mutualistic relationship. Though A. dumosa fruits all year round but its conspicuous green-hue fruits surprisingly, are not taken by birds or other mammals, but by the C. brachyotis ( Phua, P.B. and Corlett, R.T., 1989). The habit of Lesser C. brachyotis to defecate during its flight has greatly enhanced the dispersal of Tiup-tiup (A. dumosa) seeds to a wide range of habitat. Being the major food source, the Tiup-tiup (A. dumosa) thus maintains high population density of Fruit Bat (C. brachyotis) in the secondary forest (Phua, P.B. and Corlett, R.T., 1989).

One question raised here is why C. brachyotis the sole diepersing agent for A. dumosa. Phua and Corlett (1989) provide an explanation that A. dumosa has evolved over time in favor to be dispersed by the fruit bats. However, the mechanism underlying the evolution is not established. This calls for the study of natural history of both the bats and plants in the university’s secondary forest to explain this specific mutualism.

References:

  1. “Fruit Bats,” by Kelvin K. P. Lim, Dennis H. Murphy, T. Morgany, N. Sivasothi, Peter K. L. Ng, B. C. Soong et al. URL: http://mangrove.nus.edu.sg/guidebooks/text/2121.htm (accessed on 15 April 2010)
  2. Phua, P.B. & Corlett, R.T., 1989. Seed Dispersal by the Lesser Short-nosed Fruit Bat (Cynopterus brachyotis, Pteropodidae, Megachiroptera). Malayan Nature Journal, 42: 251-256.
  3. “Tiup-tiup flowers” by Flickr. URL: http://www.flickr.com/photos/shimmertje/35125906/ (accessed on 9 April 2010)
  4. Wild Fact Sheets. (2008). Common fruit bat. Retrieved 9 April, 2010, from  http://www.wildsingapore.com/wildfacts/vertebrates/mammals/brachyotis.htm