Mound Characteristics of Mud Lobster Thalassina Anomala (Herbst 1804) in
Because of mound formed by this fauna, it can change environmental condition of mangrove ecosystem. Abiotic factors such as soil humidity, pH and acid oxidation in the soil are factors which influence distribution and density vegetation especially mangrove which will be rehabilitated (Macintosh et al., 2002). Ecologically, the existence of Thalassinidae family is important macrofauna component because this activity can restore the nutrient cycle on sedimentation area (Kartika and Patria, 2012).
In some areas, it can become areal indicator with FeS2 oxidated and resulting sulfat acid (Ashton and Macisntosh, 2002; Teo et al., 2008). The information about the nest existence (mound and burrow) of mud lobster T. anomala in Southeast Sulawesi especially South Konawe is not available, therefore this research become important to be conducted to describe nest characteristics, density and mound distribution pattern formed by T. anomala in mangrove ecosystem. The results is expected to give ecological information of T. anomala especially related to nest characteristics (mound and burrow) and its role in aquatic biota at mangrove ecosystem.
Materials and Methods Time and Location
This research was conducted from January to March 2016. The research consisted of two steps which were field sampling (physics and chemical parameters) which taken in Tanjung Tiram (Figure 1) and laboratory analysis water quality analysis conducted in Texting Laboratory of Faculty of Fishery and Marine Science, University of Halu Oleo.
Figure 1. Research Station at Tanjung Tiram of Southeast Sulawesi Materials
The materials were pH indicator, thermometer, hygrometer, soil tester, GPS Garmin 60, scaled stick, pipe, digital camera, shovel, calipers (mm), stopwatch, protractor, compass, kite current, secchi disc, paper label, plastic sample, transect, quadrant plot 1 x 1m2, plastic bucket diameter of 30 cm, other materials and chemical compounds .
Research Procedure
Research station was determined using purposive random sampling method (station interpretation determined based on location or area that has mound and burrow of T. anomala at every observation station). Quadrant plot size of 10 m x 10 m was made and the distance between the nearest quadrant plots was 10 m. At every sampling point, the number of burrows or mounds made was counted. Each mound was measured its upper part, base diameter, height, burrow depth, slope and burrow direction.
Water quality parameters at each statin were measured such as temperature, transparency, current velocity, pH of water and sediment, dissolved oxygen, total suspended solid and total organic matter. Humidity of air and burrow were measured and sediment sampling was taken from a burrow of each quadrant plot. Organic content and texture fraction of the sediment was analyzed at laboratory.
Data analysis
Mound density formed by mud lobster T. anomala was calculated based on density equation (Soegianto, 1994), while mound distribution pattern used spread index formula by Marisita (Brower et al., 1990). The results of mound measurement and the correlation between burrow diameter and carapace width of mud lobster were analyzed using nonparametric analysis of Spearmen test.
Results and Discussion Results
Density and Mound Distribution
The results of research showed that the highest density was 4.5 ind/m2 at station 2 (S: 4o2’ 8,84”
and E: 122o40’18,83”) with a muddy sand substrate, followed by 2.9 ind/m2 at station 1 (S: 4o2’12,99”
and E: 122o 40’18,84”) with sand substrate and 1.5 ind/m2 at station 3 (S: 5o 6’15,75” and E: 122o 11’28,88”) with combination substrate of sludge, sand and gravel, respectively. The density of mound varied according to station, while mound distribution pattern at each research station was the same (Table 1).
Table 1. Density and mound distribution pattern of T. anomala
Station Density (ind/m2) Morisita Index (Id) Dispersion Pattern
1 2.9 1.00 random
2 4.5 1.00 random
3 1.5 1.00 random
Those data in Table 1 showed the mound distribution pattern formed by T. anomala.
Distribution pattern of those mounds at each station following random distribution pattern (Id = 1). The density and the distribution of mounds of T. anomala were clearly seen on the surface of land. Station 2 had the highest number of mounds of 4.5 ind/m2. The nearest distance between mounds was 6.7 cm, while the farthest was 227 cm with the average of 58.24 cm.
All water quality and texture substrate (including organic matter) measured at each station were quite similar (Table 2). According to Spearmen test between humidity and temperature, and salinity and substrate pH showed significantly correlation (p < 0.01) (Table 4). It means that those limiting factors had close correlation with substrate humidity parameter of burrow.
Table 2. Water and substrate quality of the mound of T. anomala measured
Parameters Average ± Standard Deviation
Station 1 Station 2 Station 3
Temperature 25.75 ± 0.45 25.33 ± 0.65 25.92 ± 0.51
Salinity 30.5 ± 0.52 29.75 ± 0.62 30.58 ± 0.51
pH substrate 6.31 ± 0.19 5.35 ± 0.19 6.72 ± 0.17
pH water 7.5 ± 0.52 7.5 ± 0.52 7.5 ± 0.52
Humidity of burro substrate 7.26 ± 0.29 17.86 ± 0.57 6.54 ± 0.32
DO 4.1 ± 0.40 4.53 ± 1.20 4.3 ± 1.25
Total suspended solid 0.35 ± 0.25 0.42 ± 0.26 0.33 ± 0.11
Total organic matter 25.44 ± 0.98 43.53 ± 9.43 42.65 ± 11.37
Table 3. Texture Substrate and Organic Matter of the mound of T. anomala measured
Station Percentage (%)
Dust Clay Sand Class BO
1 6.8849 0.2758 92.8393 Sand 2.2
2 2.4562 8.553 88.9908 Sand 6.5
3 5.881 0.1709 94.6104 Sand 4.9
Table 4. Correlation between substrate humidity of burrow and temperature, salinity, and substrate pH
Parameters Substrate Humidity of Burrow (%)
Temperature (oC) 0.0001**
Salinity (ppt) 0.0001**
Substrate pH 0.0001**
**Significantly difference (p < 0.01)
Mound Characteristic of T. anomala
Some mound architectural parameters showed no much different, although the depth of mound was different between station 2 and station 1 and 3 (Figure 2 and Figure 3).
Figure 2. Average and standard deviation of high mound, upper and bottom diameter of the mound, burrow depth and burrow diameter formed by T. anomala on each station
Figure 3. Average and standard deviation of mound slope, burrow slope and burrow direction formed by T. anomala on each station.
Those mound architectural parameters (mound height, mound upper and bottom diameter, burrow depth, mound and burrow slope, and burrow direction) clearly showed that they had relatively the same value at each station, except burrow depth which had much different between station 2 and station 1 and 3. The average of burrow depth was 28.14 ± 11.82 at station 2, while the values were relative similar 16.4 ± 2.01 and 16.26 ± 3.21 at station 1 and 3, respectively. Based on correlation analysis between mound height and burrow depth at each station showed significantly correlation (95%) which it is showed by probability rate in spearmen correlation test of 0.026 less (p < 0.05).
Among these parameters, the mound height and the mound bottom diameter, and the mound height and burrow depth had significantly correlation (p < 0.01) I t s u g g e s t s that the higher mound made by lobster, the deeper burrow the higher mound, and the wider bottom diameter of mound architecture produced by mound lobster.
Table 5. Mound architectural correlation of T. anomala at all station
Parameters Mound Height Mound Slope Mound Upper Diameter
Burrow
Slope Burrow Depth
Mound Bottom Diameter 0.005** 0.043*
Mound Height 0.043* 0.026*
Mound Slope 0.041* 0.417ns
** significantly different at p < 0,01); * significantly different at p < 0,05) and ns = not significantly different The results of burrow diameter measured and the correlation between burrow diameter and carapace width (CW) size are presented in Table 6. Based on Spearman correlation test, data in Table 6 showed empirically CW and burrow diameter had significantly correlation p < 0.01). It indicates that mound of T. anomala exited and entered the burrow from a mound connected t o 2 - 5 secondary tunnels which lead out the burrow (outside burrow of the mound).
Table 6. Carapace width measured (cm) and the burrow diameter of mound
No Station Carapace Width (CW) Burrow Diameter
(mm) (cm)
1 1
2.1 4.2
1.6 3.4
1.6 3.4
2 3.9
1.3 2.9
2 2
2.3 5.4
2.1 4.4
1.7 3.6
1.6 3.3
1.5 3.1
3 3
1.9 3.8
1.9 3.8
0.8 2.1
1.7 3.5
0.9 2.5
Average and Sd 1.67 ± 0.424 3.55 ± 0.791
Correlation 0.0001 (significantly different, p < 0.01)
Discussion Mound Density and Distribution
This study showed that the highest density was 4.5 ind/m2 at station 2 with muddy sand substrate. Visually the density rate formed by T. anomala could be clearly seen based on the measurement of the distance between mounds of mud lobster. The closest distance between mounds was 6.7 cm at station 2, while the furthest was 227 cm. The average distance between distances between
the mounds was 58.24 cm, and 193.94 cm and 453.7 cm at station 1 and 3, respectively. This proved empirically that mound density at station 2 was higher than that of two other stations (station 1 and 3). This study also presented that an individual T. anomala could form more than one mounds adjacent and connected to one another. This was identified when the mound architectural measurement (opening of the cross section of the mound) showed that burrows were connected by 1 - 5 tunnels and interconnected among them. Those channels connect each other at outside of the burrow as inlet access of mud lobster T. anomala. Those mound have a function as a camouflage to cover the main burrow which protecting T. anomala from competitors and predators. I t is in accordance with description of Mukai and Koike (1984; Kinoshita, 2002) that other species of thalassina such as Upogebia and Callianassa had typical mound form resembling letters of U, Y and I. Those burrow shapes associate with the feeding activity. For instance, letter of Y is a typical form of crustacean class (burrowing crustacean) used to obtain suspended particles in water and to ingest the substances deposited inside the burrow.
The percentage of mounds found at each station, particularly station 2 that have the largest number of 45 mounds. Those mounds tended to distribute between mangrove vegetation and its association. T. anomala interaction with mangrove vegetation was dominantly at Rhyzopora and Sonneratia vegetations. Those niche characteristics indicates that each nest or mound formed by mud lobster was accessible to water source and those were strongly affected by tidal dynamics. Several studies had stated that mounds formed by T. anomala always interacted with mangrove vegetation such as Bruguiera sp., Rhyzopora sp., Xylocarpus sp., and other mangrove plants located in the interior forest (Sasekumar, 1974); Ashton and Macintosh, 2002). Teo et al., (2008) stated that burrow characteristics shaped by T. anomala was made to branch and towards water sources. The distribution pattern of mounds was random. It is an indication that T. anomala activity in making mound was no depending on certain environmental conditions.
The results of some water quality measured showed relative similar values Random distribution pattern usually occurs in a group of solitary organisms with a specific characteristic (Brower et al., 1990). Johnson (1961) and Sasekumar (1974) revealed that macrofauna groups of random distribution pattern tend not to have difficulty in finding food and adapting to their environments. Such conditions cause T. anomala widely spread in mangrove ecosystem (Kartika and Patria, 2013). The correlation of humidity substrate among temperature, salinity and soil pH was significant correlation (p < 0.01). It indicates that when temperature increase that salinity also increase and the burrow humidity decrease and vice versa. Furthermore, the temperature and texture of burrow clay also has significant correlation. The clay texture tends to bind large amount of water because it has a smaller pore space and high surface pressure (Colemen et al., 2004; Ruiz et al., 2008). Due to clay texture that muddy sand substrate has the highest density of T. anomala mound. It indicates that the muddy substrate is one among environmental parameters which is suitable for habitat preferred by mud lobster.
The average pH of substrates at all stations ranged 5.35 – 6.71. Sasekumar (1974) stated that the substrates derived from T. anomala’s nest will be acid. Thus, the presence of T. anomala can be a bioindicator of acid sulphate soil (Ashton and Macintosh, 2002; Teo et al., 2008; Kartika and Patria, 2013). The highest level of soil organic matter (BO) was obtained 6.5% at station 2, followed by 4.9%
and 2.2% at station 3 and station 1, respectively. The percentage of BO content on burrow substrate is strongly influenced by the presence of clay texture, as one of clay characteristics which tends to a bind large amount of water. The present study proves that the amount of organic matter at station 2 has significant correlation to the clay texture which was higher percentage of 8.553% compared to station 1 of 0.2578% and station 3 of 0.1709%. One of T. anomala’s role as burrow crustacean is producing organic materials in the sediment with low toxicity. Kristensen (2008) stated that the increase of aeration in the soil due to burrow formed by the excavations of decapoda groups may affect the anoxic properties in mangrove substrates. These fauna groups are also able to change the physical properties of substrates because burrow and mound made by them and is also related to physical transport processes (materials, liquids and gases) as well as chemical reactions.
Characteristic of T. anomala’sNest
The mound architectural parameters of mud lobster nest were mound height, upper and bottom mound diameter, burrow depth, burrow diameter, mound and burrow slope, and burrow direction. The correlation of these parameters was significant (p < 0.05), except burrow slope was not significantly correlation (p > 0.05). The deeper burrow of T. anomala and the higher mound of excavation activity of T. anomala, the wider the bottom burrow mound diameter. Kartika and Patria (2013) stated that the soil
substrates released to the surface by T. anomala form like a chimney on the ground. Kinoshita (2012) stated that Upogebia sp. and Callianasa sp. tended to differ with their excavation activity. Both these Thalassinidae groups show the nests in the form of burrow and remaining substrates (pellets) around the burrow without making stacks or forming chimneys. Kartika and Patria (2013) stated that mound formed by T. anomala is clearly seen and unique in mangrove ecosystem. The size and amount of nest is also formed continuously. The existence of nest T. anomala will change the topography and landscape of substrate and also create a microhabitat for other species associated with mangrove ecosystem (Ashton and Macintosh, 2002; Teo et al. 2008). It was observed that during 12 hours (20.00 – 08.00 WITA) and 08.00 – 20.00 ) of mud lobster T. anomala was a solitary and nocturnal organism. Mud lobster T.
anomala is usually caught at night using net. The latest observation at study area showed that the burrows formed a letter of L, where the upper part of the letter is the mouth of the burrow covered by the mound, and the bottom end of the letter of L or tunnel is a tunnel connected to the outside of T. anomala burrow. Nowadays, some nests found in the several studies were in the form of U, Y and I. (Mukai and Koike, 1984; Kinosita, 2002) which indicated that individual of T. anomala has build more than one mound.
Conclusion
The mound formed by T. anomala show a random distribution pattern at each station. The highest density was found 45 mounds at station 2 with muddy substrate, while the lowest density was 15 mounds at station 3 with a substrates mix of mud, sand and gravel. A significant correlation was found between the burrow diameter and the carapace width of T. anomala.
Acknowledgment
The authors would like to thank to the Directorate of Research and Community Service, Ministry of Research, Technology and Higher Education of the Republic of Indonesia who has financed this research.
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