DIET OF Labuanium politum (AN OBLIGATE ARBOREAL ) AT KAMPUNG TANJONG ASSAM, SPAOH, SARAWAK

NUR AMIRAH BINTI MOHAMAD ALWIE

Bachelor of Science with Honours (Aquatic Resource Science and Management) 2015/2016 Pusat Khidmat "WaklwuatAkadem. UMVEItSITt MALAYSIASARAWAi.

P. KNIDMAT MAKLUMAT AKADEMIK UNIMAS 11

100027267911111 Diet of Labuanium politum (An Obligatei Arboreali i11111 iCrab) at Kampung Tanjung Assam, Spaoh, Sarawak

Nur Amirah Binti Mohamad Alwie

This report is submitted in partial fulfillment of the requirement for degree of

Bachelor of Science with Honours

(Aquatic Resource Science and Management)

Faculty of Resource Science and Technology UNIVERSITI SARAWAK DECLARATION OF AUTHORSHIP

I, NUR AMIRAH BINTI MOHAMAD ALWIE declarethat the final year project report

entitled: DIET OF Labuanium politum (AN OBLIGATE ARBOREAL

CRAB) AT KAMPUNG TANJUNG ASSAM, SPAOH, SARAWAK.

and the work presentedin the report are both my own, and have been generatedby me as the result of my own original research.I confirm that:

" this work was done wholly or mainly while in candidature for a research degree at this University;

" where I have made corrections based on suggestion by supervisor and examiners, this has been clearly stated;

" where I have consulted the published work of others, this is always clearly attributed;

" where I have quoted from the work of others, the source is always given. With the

exception of such quotations, this report is entirely my own work;

"I have acknowledged all main sourcesof help; " where the thesis is based on work done by myself jointly with others, I have made clear exactly what was done by others and what I have contributed myself;

" none of this work has been published before submission

Signed:

d ýA N "11!

Aquatic Resource Science and Management Programme Department of Aquatic Science Faculty of Resource Science and Technology Universiti Malaysia Sarawak (UNIMAS)

Date: 17 June 2016

I ACKNOWLEDGEMENT

Alhamdulillah, all praises to Allah the Almighty for giving me a chance and strength in

order to complete my final year project. I would like to express deepest gratitude to my

supervisor, Dr. Siti Akmar Khadijah Ab Rahim for giving me great support amd guidance,

patient and perseverance in assisting me to complete my work from the beginning until the

end. Special thanks also to my examiner for the precious time spent to evaluate my final

year report.

My sincere thanks also given to local people of Kampung Tanjong Assam,

especially Mdm Kelan Cahaya, Mdm Siti Ra'abah, Mr. Rahman, Mr. Narawi and others

that are involved during field trip that are wiling full to help me to get the samples, giving

comfortable place for us to stay and feed us with delicious foods. I would also like to

acknowledge help that I received from my kind postgraduate senior, Mr. Norhakimi

Mohamad, Ms. Aina Syuhaida, Mr. Wan Zabidi, Mr. Mohd Izwan and Mr. Shahir for their

willingness to guide me anything regarding to my final year project.

Thanks also for all of my lab mates, Akma Iddin, Farah Nazirah, Muliana, Ernalis,

Nurfarhanie, Zarul and Corinth for always cheering me on my works in the lab. Not to

forget my friends that always cheering me in doing this project, Euanice and Izaty. Next to

it, the most important life support, my precious parents and family for giving nic

emotionally and financial support for me to finish this report.

11 Put Khi4mat MaklumatAkademit U1viVE1tSM! º'tALAYSU SARAWAk

TABLE OF CONTENTS

DECLARATION OF AUTHORSHIP I

ACKNOWLEDGEMENT II

TABLE OF CONTENTS III

LIST OF ABBREVIATIONS V

LIST OF TABLES VI

LIST OF FIGURES VII

ABSTRACT 1

1.0 INTRODUCTION 2

2.0 LITERATURE REVIEW 4

2.1 Mangrove ecosystem 4

2.1.1 Zonation of mangroves 4

2.1.2 Nipah palm area 5

2.2 Taxonomy of Labuanium politum 6

2.3 Sesarmid Family 7

2.3.1 Arboreal Climbing Skills of Sesarmid 8

2.3.2 Feeding Habits of Sesarmid 8

3.0 MATERIALS AND METHODS 9

3.1 Study Area 9

3.2 Sampling Procedure II

3.3 Stomach Content Analysis 13

3.4 Feeding Experiments 14

III 3.5 Data Analysis 15

4.0 RESULTS 16

4.1 Diet Composition of Labuanium politum 16

4.1.1 Frequency of Occurrence for each of Food Groups 19

4.2 Stomach Fullness 22

4.2.1 Comparison of StomachFullness between Day and Night 22

4.2.2 Comparison of StomachFullness between Disturbed Vs 23

Undisturbed

4.3 Feeding Behaviour of L. politum 27

4.3.1 Field Observation at the Natural Habitat 27

4.3.2 Feeding Experiment 28

4.3.3 Leaf Categories Preference 30

5.0 DISCUSSION 32

5.1 Diet Composition of Labuanium politum 32

5.2 Comparison of StomachFullness 33

5.3 Feeding Behaviour of L. politum 34

5.4 Limitation and Recommendation 34

6.0 CONCLUSION 35

REFERENCES 36

APPENDICES 40

IV LIST OF ABBREVIATIONS

L. = Labuanium

N. = Nypa

CW = Carapace width

CL = Carapace length

EtOH = Ethanol

V LIST OF TABLES

Table 1: Description of sampling site at Kampung Tanjong Assam. 10

Table 2: Classification of food groups for stomach content analysis. 15

Table 3: The presence of food group materials in the disturbed and undisturbed 16 nipah area.

VI LIST OF FIGURES

Figure 1: Labuanium politum found at Kpg Tanjong Assam. 6

Figure 2: Study site plots of Kampung Tanjong Assam, Spaoh. 11

Figure 3: Mangrove area of Kpg. Tanjong Assam. 13

Figure 4: `Pengait', a tool used to catch L. politum. 13

Figure 5: Debris (Sand and mud) found in the stomach of L. politum. 17

Figure 6: Plant materials found in the stomach of L. politum. 17

Figure 7: Insect found in the stomach ofL. politum. 18

Figure 8: Frequency of occurrence of food groups in disturbed and undisturbed 19

area.

Figure 9: Frequency of occurence of food groups in six male and nine females of 20

L. polituni in disturbed area.

Figure 10 : Frequency of occurence of food groups in 20 male, 20 female of 21

L. politum in undisturbed area.

Figure 11 : Differences in stomach fullness index in L. politum between day and 22

night.

Figure 12 : Comparison of the stomach fullness in disturbed and undisturbed area. 23

Figure 13 : Empty stomach fullness estimation of L. politum. 24

Figure 14 : 25% stomach fullness estimation of L. politum.

VII Figure 15 : 50% stomach fullness estimation of L. politum. 25

Figure 16: 75% stomach fullness estimation of L. politum. 26

Figure 17 : 100% stomach fullness estimation of L. politum. 26

Figure 18 : Labuanium politum foraging on nipah leaves. 27

Figure 19 : L. politum emerging from between the base of nipah tree. 28

Figure 20 : Set up of experimental tanks during day time. 29

Figure 21 : Pinch mark on the leaves by L. politum during night time (7.00 p. m. ). 29

Figure 22 : Leaf categories preference of L. politum. 30

Figure 23 : Set up of experimental tanks with three type of leafs Nypa fruticans 31

(Green, yellow, brown).

Figure 24 : Leaf preferenceof the . Shows the pinch mark on the green leaves 31

by L. politum after 24 hours.

VIII Diet of an Obligate Arboreal Crab (Labuanium politum) at Kampung Tanjong Assam, Spaoh, Sarawak

Nur Amirah Binti Mohamad Alwie

Aquatic Resource Science and Management Programme, Faculty of Resource Science and Technology Universiti Malaysia Sarawak.

ABSTRACT

Labuanium politum is an obligate arboreal crab that belonged to Family and can be found at nipah palm mangrove in Kampung Tanjong Assam, Spaoh, Sarawak. It is known as `Geramak apong' by local people. It lives and hides inside the base fronds of the nipah tree. On 7-9 November 2015,68 samples for diet composition and comparison of the stomach fullness of these crabs at disturbed and undisturbed nipah palm area were obtained using special hooks `pengait'. Later, the second samplings were done on 23`d March 2016 for the observation of the feeding behavior of this crab where three samples were obtained. Results showed that this crabs highly preferred debris (100%) and plant materials (80%) as their primary consumption on disturbed nipah palm area compared to undisturbed area where only 57.5% and 70% of debris and plant materials, respectively. For the overall of the stomach fullness of crabs, higher stomach fullness were observed during night time (41.7%) compared to day time (23.2%). Comparing the crabs that were caught at night time, disturbed area showed higher stomach fullness (75%) than the undisturbed area (25%). For the feeding behavior experiment, it is proven that this crab is nocturnal. L. politum strongly preferred green leaves of Nypa fruticans when offered three different types of categories of the leaves (green, yellow, brown). Therefore, this study provides a new information on the diet of L. politum as this is a first attempt to record diet of this crabs.

Key words: Labuanium politum, Geramak apong, nocturnal, arboreal, Nypafruticans.

ABSTRAK

Labucrnium olpittrnt adalah ketarn arboreal obligat oleh Fantdi Sesarmidae dan boleti didapati di kawasan nipah di Kampung Tanjong Assam Spaoh, Sarawak. lcr dikenali sebagai 'Geramak apong' oleh penduduk tentpatan. la hidup darr bersemhturyi di dalam pangkal pelepah pokok nipah. Pada 7-9 November 2015,68 sampel telah dikutip dari kawasan nipah yang terganggtr dan tidak terganggtr untuk penrerhatian kompo.cisi ketam diet dan perbandingan kepentrhan perul ini di mann in diperolehi dengan ntenggunakan pengait'. Kenulian, sampe! kechut telah dijalartkan pada 23 Mac 2016 bagi pemerlrcrtiart tingkah laku ketanr ini di mmna tiga sanrpel ketam diperolehi. Hasil kajian ntenunjukkan hahawa ketam ini nremilih urttuk makcrn debris (100 %,) dan diiktuti bahan-bahan tunthuhan ( 80 `%) sebagai pemakanan utama mereka di kawa.can nipah terganggu berbanding dengan kawasan nipah yang tidak terganggu di nrana hanya 57.5 uruuk debris don 70 % huhan-hahan turnbultan. Untuk keselurtchan pemerhatiamr terhadap kepenuhrna ke tant, ia nterturtjukkan lebih tinggi pada waktu rnalant ( 41.7 (Ya)hencunding dengan slang hari (23.2 ketunt Perhandingan yang ditcutgkctp pada tiraktu rnalant antara kairasart nipah vang diganggtr mentrnjtrkka kepenuhan perut lebih tinggi ( 75 %) daripada kawa.can tidak terganggu ( 25 Bagi eksperinten tingkah ketant laka pemakanan, iu memhrrklikan bahaH"a ini aktif pada wakttt ntalanr, L, polihmt lebilr rrtengtrtamakan hijau ditairarkan tiga jenis kalegori dann (hijau kuning, ). Oleh itu, kajian ini dann nipah apabila , coklat diet L. kerana ntemheri makltnrtat harn mengenai polittan ini adcrlalt percubaan per7ama tattuk nterekod diet ketant irti.

Kata kunci: Labuanium ý ol,itum, Geramak apong, malam,memanjat pokok, Nwa frutican

1 1.0 INTRODUCTION

Knowledge of the diet preferences of a species is important to understand certain species nutritional requirements and thus its interactions with other groups of . Brachyuran crabs are known as decapodsand comprised more than 6,793 species(Hoseini et al. 2012).

The crabs show various feeding habits such as a filter feeders, sand cleansers,mud, plant, and carrion feeders,predators, commensalsand parasites (Dall and Moriarty, 1983). Crabs occupy many different niches and inhabit many different habitats in a variety of geographical areas, and this show in the variety of food consumed by them (Dahdouh-

Guebas et al. 1999). In the highly diverse mangrove systems of and

Australia, Sesarmid decapod graze on large proportions of mangrove litter

(Micheli, 1993).

Crabs habitats include freshwater, marine and terrestrial. One of the most common habitats for crabs is in the mangroves area where it is one of the biologically diverse ecosystems in the world, rich in organic matter and nutrients that can support very large biomass of flora and fauna (Pawar, 2012). The mangrove area of Kampung Tanjong

Assam, Spaoh, Sarawak, also support population of obligate arboreal tree climbing crabs on their nipah palm tree. The word arboreal means that this crab is a tree climber and can cling on the nipah tree leaflet. Local people called it as `geramak apong' because

`geramak' stands for small crabs, while `apong' stands for nipah palm tree. The scientific name of these crabs is Labuanium politum. It primarily lives hiding deep between thc narrow spaces of the nipah tree base fronds. According to Ng et al. (2015), this crabs are known to be associated with nipah palm tree area and exhibit a nocturnal behaviour.

Local people of Kampung Tanjong Assam collect this crab in large number as foorl and they identified the crab by its claws that were completely red. This crab is collected

is long, bamboo using a traditional gear, called `pengait'. It a stick that have a sharp hunk

2 end. The study site is conducted on mangrove area of two different sites, disturbed and undisturbed nipah area. On the disturbed area, the presenceof embankment causethat area is not exposed to the tidal inundation. While for undisturbed area, its area is behind the embankmentand exposedto the tidal inundation.

The presence of L. politum on other mangrove area such as in Labuan, Johor,

Singapore and Philippine had been reported by Ng et al., (2015) but not in Sarawak yet.

This study on L. politum at other mangrove areas only focused on the taxonomy and ecology of this crab. However, there is no study yet done about the feeding behaviour and diet preference of L. politum. Therefore, the study of the diet preference of this was conducted in order to: 1) document the diet composition of L. politum found at disturbed nipah area and undisturbed nipah area; 2) compare the stomach fullness of L. politum obtain during the day and the night time; 3) investigate the feeding behavior and leaf category preference (green, yellow, brown) of Nypafruticans leaves by L. politum.

3 2.0 LITERATURE REVIEW

2.1 Mangrove ecosystem

Mangrove forest or mangal, is one of the major forests at the coastal ecosystem where it dominates along most tropical and subtropical shoreline. The term `mangrove' itself is used to define both the plants that occur in tidal forest throughout tropical and subtropical region (Tomlinson, 1986). It is consisting of the biotic and abiotic components, including inter and intra-specific interactions where it is influence by the tides (Ellison and

Farnsworth, 1993). In Malaysia, the total area of mangrove forest gazetted as reserves and protected area is unclear. From the reports of Wetlands International-Asia Pacific (1996), mangrove forest reserves in Sarawak has much larger mangrove areas than Sabah and

Peninsular Malaysia, but 131,000 out of 168,000 hectares in 1993, is not protected in mangrove forest reserves.

The vegetation in a mangrove forest is mostly covered by salt and flood tolerant trees and shrubs that are considered as wetland. Although they are from different family genera and family, they have morphological and adaptive mechanisms in common that allows them to grow in saline environment. The existence of each distinct zone is dominated by different mangrove species (Rey, 1999). Most mangrove forests are made up of only a few species and each species only grows in a certain area such as crab species.

This mangrove litter is an important source of food for animals that inhabit this ecosystem as well as an ultimately a form of basis in primary production in mangrove environment.

2.1.1 Zonation of mangroves

Mangroves exhibit zonation patterns in a number of different geographic regions. This pattern gives variation in speciesoccurrence across environmental gradients of mangroves.

in habitats The zonation of plant communities intertidal often results in monospecific

4 Pusat Kh; sjmacMaklumat Akaücui: UNIVERSII7MALAYSIA SARAWA F. bands of vegetation occurring parallel to the shoreline where the vegetation typically

linked from soil type (mud, sand or peat), exposure to wave action, salinity, freshwater

inflow and tidal influence (White et al., 1989). The mangrove zones usually narrow in width where it rarely exceeds four kilometers (Danielsen and Verheugt, 1990). The cause of this zonation has been attributed to salinity, elevation and exposure to wave action where tidal inundation is the dominating factor (Aksornkoae, 1993). This in turn can gives variety of mangrove crab species along the zonation of the mangroves where mangrove crab inhabit on each of the zone in mangrove area depending on its habitat structure and its physical appearance that can adapt with their environment. Crabs are particularly abundant in mangroves where the densities per square metres are 10-70 individuals can be found on mangroves (Macintosh, 1984), especially of burrowing species of the genera

Cleistocoeloma, Macrophthalmus, Metaplax, Ilyoplax, Sesarma and Uca (Sasekumar et al., 1994). In Malaysia, more than 100 species of mangrove crabs are known and 76 species are known from ; in the latter this represents 22 percent of the total crab fauna for the island (Ng et al., 2015).

2.1.2 Nipah palm area

Nipah (Nypa fruticans) is a useful mangrove species in South, Southeast Asia and Oceania.

Many palm species including nipah, have been tapped throughout the tropical region for the production of fresh juice, fermented drinks, syrup, and raw and refined sugar

(Dransfield, 1977). The sugary sap from the nipah in inflorescence stalk is used to make vinegar, and like those of other palms such as the coconut. In Malaysia, and

Bangladesh, its saps are also used to make a popular alcoholic beverage. The nipah palm

1986; Dransfield, can grow up to 10 m tall (Tomlinson, 1977). Because of this variety

5 flora in mangrove that have nipah palm tree, it become a habitat of mangrove crabs that

depend on the nipah tree as their source of diet.

2.2 Taxonomy of Labuanium polituni

Taxonomic classification of Labuaniuin polituni (Sesarmid crab). It has 31 genera under it based on Dana (1851), adapted from World Register Marine Species (WORMS).

Phylum : Arthropoda (Latreille, 1829)

Subphylum : Crustacea (Brunnich, 1772)

Class :

Order : (Latreille, 1802)

Family : Sesarmidae (Dana, 1851)

Genus : Labuanium (Serene & Soh, 1970)

Species : L. politum (de Man, 1888)

ýi

Figure 1: Labuanium politiun that can be found at Kpg Tanjong Assam, Spaoh, Sarawak.

6 2.3 Sesarmid Family

Sesarmid crabs dominate the fauna of mangrove forests (in the Indo-West Pacific and in eastern America (Micheli, 1993). Jones (1984), has reported that a zonation of sesarmids across the intertidal area, with small sized species generally occupying the lower levels and larger species on the high intertidal forests. The crabs of Family Sesarmidae are known to have significant ecological role in mangroves (Lee, 1998) where it is one of the most common and abundant faunal groups in retaining nutrients within mangrove forests (Jones

1984; Smith et al. 1991). This crab also helps in removing and processing of mangrove leaves before the tide can carry them away (Lee, 1998; Skov and Hartnoll, 2002), and alter the properties of the soil by their burrowing activities (Smith et al., 1991). From studies of mangrove environments, it has showed that litter consumption and burial by Sesarmids removed 30-90% of the annual litterfall (Micheli, 1993). This crabs also involved in competitive interactions with other species (Fratini et al. 2005).

Studies of gut content shows that sesarmid crab consume significant amount of mangrove detritus (Malley, 1978). The feeding habits of mangrove crabs have been divided into seven groups; herbivore, carnivore, omnivore, deposit feeder, omnivore/deposit feeder, specialized filterer, and filterer/omnivore (Jones, 1984). The examples of sesarmid crabs of genus Episesarma; Sarmatium germaini, Perisesarma eumolpe and Neosarmatium smithi feed on the mangrove litter where it is composed of fallen mangrove leaves of Rhizophora sp. seedlings, and twigs that fall from the trees ui; the forest floor and into the water (Masagca, 2009). While for sesarmid crabs of the genus

Labuanium; Labuanium politum where this species live among the fronds base of the nipa h palm (Nypa frutiean), hiding deep in the bases and only coming out to feed on the lca%c:..

by (Sivasothi, 2000). (Ng et al., 2008) as it is reported herbivorous

7 2.3.1 Arboreal climbing skills of sesarmids

On the observation by Jimmy (2009), Perisesarma bidens are having preferences in arboreal environment whereas Selatium elongatum and Episesarma versicolor were seen clinging on mangrove stems. They rush to the mangrove stems when there are disturbance and remain stationary. The probable reasons of these crabs cling to mangrove stems or mangrove trees, may be to find food or as avoidance from predator or from very long immersion in the water during high tides (Masagca, 2009). Another member of sesarmid genera Labuanium, Selatium (Serene & Soh, 1970), and Aratus and some species of

Parasesarma (De Man, 1895) occur regularly on trees and also regarded as an obligate tree-climbing crabs (Cumberlidge et al., 2005; Fratini et al., 2005; Sivasothi, 2000;

Vannini et al., 1997).

2.3.2 Feeding habits of sesarmids

Most Sesarminae are either grazers or shredder detrivores dependent on mangrove biomass. Crabs forage continually on fallen leaves; either feeding directly or transporting them to burrows for later consumption. Sesarmids species select particular litter types of the mangrove leaf species available, where it leads to variable rate litter mineralization.

Ravichandran et. al., (2007) said that the analysed diet of sesarmids species mainly consisted of mangrove leaves and together with matter where it is as their major food source. Based on Malley (1978) studies, sesarmids stomach content comprises of 55-

95% of leaf fragments. They feed on leaves whether on the sediment surface or pulling them back into the burrow for later consumption (Slim et al., 1997). Some of sesarmids

during leaves from also are even climbing up the trees the night to consume the canopy

(Fratini et al., 2005)

8 3.0 MATERIALS AND METHODS

3.1 Study Area

The study was conducted at Kampung Tanjung Assam, Spaoh Sarawak where it is located along Sungai Padeh, Spaoh (1'28'17.8"N 111°24'33.2"E). The sample was collected at six different plots at Kampung Tanjong Assam terrestrial area, on disturbed nipah area (Plot 1,2 and 3) and undisturbed nipah area (Plot 4,5 and 6) during the day and night time. Descriptions of sampling site at Kampung Tanjong Assam (Table 1) with map of the study site (Figure 2). The sampling was done on 7-9 November 2015.

Table 1: Description of sampling site at Kampung Tanjong Assam

Plot Coordinates Site description

1N 01°28.226' No sap tapping activities around six E 111°24.483' months. Geramak apong exploited. Do not exposed to tidal inundations.

2N 01°28.297' Sap tapping on going. E I11 °24.428' Do not exposedto tidal inundations.

3N 01°28.348' The sap tapping was still at the E I11 °24.385' beginning stage. Do not exposed to tidal inundations

4N 01°28.382' Undisturbed area. Behind the E 111°24.345' enbankment.

5N 01°28.389' Undisturbed area. Behind the E 111 °24.347' enbankment.

6N O1°28.390' Undisturbed area. Behind the E 111°24.350 enbankment.

9 Figure 2: Study Tanjong Assam, Spaoh. PI Plot 1, site plots of Kampung = P2 = Plot 2, P3 = Plot 3, P4 = Plot 4, P5 Plot 5, P6 Plot 6. tree " = = ° nipah palm area , river, road, buildings.

10 3.2 Sampling procedure

The samples were collected by using a special gear, `pengait' (Figure 3) at six different plots site along the mangrove area where three different plots at disturbed nipah area and another three plot at undisturbed nipah area. For the size of plot 1 and plot 2, there was 10 in x 10 in, for plot 3; 13 mx 10 m, plot 4; 10 in x 20 in, plot 5; 10 in x 13 in and plot 6; 5 in x 14 in respectively where it was determined by using range finder (Nikon, Prostafff S).

Within each of the plots, GPS reading was taken by using (Garmin, GPSMAPO 78s) and the sampleswas collected as much as could. The collection of sampleswas done during the day for each of the plots while for plot 2,3 and 4 during the night time. The caught crabs during the day and night was counted and sorted to make the comparison of stomach fullness betweenthe samplescollected during the day and night.

Immediately after being captured, the crabs was narcotised by cooling (immersion in ice water), and preserved in 10% buffered formalin where it need to be done as soon as possible to prevent the digestion of the food they had taken. After back to the camp site, the samples collected was transferred into 70% ethanol. The measurementwork was done on the day of the sampling where the carapacewidth (CW), carapacelength (CL), and sex for all the captured specimenswas recorded. The CW and CL of the crabs on the disturbed area are range from 17.53 to 36.23 mm and 20.65 to 40.10 mm, respectively while CW and

CL of the crabs on the undisturbed area are range from 17.56 to 33.96 mm and 20.81 to

38,96 mm, respectively. The sex of the crabs was determined based on their abdominal characteristics.Then, the photograph of the sample was taken.

During the sampling, 11 of the samples that were collected that are in perfect conditions are let to live to make feeding experiments to see the feeding behaviour of thr crabs. The carapacewidth and carapacelength of the crabs are range from 17.80 to 30.

before mm and 20.96 to 34.49 mm, respectively. Sexesof the crab was recorded they were

11 placed in experimental tanks where each of the tanks was filled with the mud from the

nipah area and covered with 50% sea water up to 1cm depth to avoid desiccation of the

crabs and to imitate the natural habitat of the samples to interpret the stomach content

analysis. The experimental tanks are placed in a box to cover it from daylight where to

keep it in the dark. Some of the nipah leaves pieces were offered to the crabs. The feeding behaviour of the 11 crabs were frequently observed and recorded using camera to see whether they are having a nocturnal behaviour.

Figure 3: Mangrove area of Kpg. Tanjong Assam

12 Figure 4: `Pengait', a tool used to catch L. polittnn

3.3 Stomach Content Analysis

The carapace width and carapace length of the studied crabs ranged from 17.53 to 35.96 mm and 19.54 to 40.10 mm, respectively. The dorsal side body of the samples was cut open, where the attached musculature and gills was cleared, and the foregut was removed carefully by cutting of the oesophagus as following the method adapted from Sukumaran

(1997). The stomach intact with the digestive tract was removed carefully into a Petri dish.

The stomach was dissected from each sample with dissecting needles to get the contents and was transferred into 70% EtOH into a Petri dish (Williams, 1981). To acquire the degree of stomach fullness, a visual estimate of the fullness of the stomach was made after the removal where the subjective scale are from 1 to 5 (1: empty, 2: 1% to 25% full, 3:

25% to 50%, 4: 50% to 75% full 5: 75% to 100% under stereo microscope (RaxVision).

Then, the food components of the stomach contents examined under stereo microscope, where the recognizable items was recorded. The whole of the stomach contents of all th, specimens was segregated into food-group wise and each group's contribution was

13 assessedvisually. Then, each of food groups was evaluated by ranking them by its percentagefrequency of occurrence (Sukumaran and Neelankantan, 1997). These methods include recording the number of stomachs containing individuals of each food category, where it is expressedas percentageof all the stomachsexamined according to the formula:

Frequency of occurrence= No. of stomachswith particular food group x 100

Total no. of stomachswith food

The frequency of occurrenceof will be calculated and recorded.

3.4 Feeding Experiments

Another short trip was done on 8th February 2016 for second collection of the samples.

Total of three L. politum was collected during the trip. The carapace width and carapace length of the crabs are range from 17.80 to 30.74 mm and 20.96 to 34.49 mm, respectively.

Three samples of crabs were placed individually in different, clear experimental tanks, 18 cm in diameter and 11 cm high. The sexes of the crab were recorded before they were placed in it. The experimental tanks were conducted in a shaded place in the laboratory in which crabs experienced a regular diurnal cycle. Range of CW and CL each of the crabs

filled were recorded. Each of the tanks was with the mud from the nipah area and covered

depth desiccation with 50% sea water up to 1 cm to avoid of the crabs. It is also to imitate

Three the natural habitat of the sample. type categories of Nypa fruticans leaves was

leaves divided into offered to the crabs where the are green, yellow and brown, on the basis

leaf. The leaf biomass of the colour. Each crab only received only a single type of each

0.001 was taken at the beginning of the experiment to the nearest g using an electronic balance before offered to the crabs. The consumption of three nipah leaf types is compared

biomass The after 24 hours, when the final was taken. experiment was conducted and repeated over a period of 3 days.

14