Diversity of Macro Invertebrates and Their Habitat Characteristics in Lan-Kuu Freshwater Wetland, Myanmar

Lan-Kuu freshwater wetland of Auk SaThar in Mingin Township, Sagaing Region was investigated for its species composition, relative abundance, and diversity of aquatic macro-invertebrates from June 2020 to January 2021. This wetland has water throughout the year and is used by many local people for fishing and trapping birds. Thirty macro invertebrates’ species belonging to 28 genera, 19 families, 11 orders, 5 classes, and 3 Phyla were identified and recorded. These species belonged to the orders Hemiptera (23%), Coeleoptera and Odonata (14% each), Orthoptera, Architaenioglossa and Sorbeoconcha (10% each), Lepidoptera (7%), and Hymenoptera, Araneae, Decapoda, and Opithopora (3%). Among the collected specimens Dytiscus verticalis accounted for the highest number of individuals while the least number of individuals were Arocatus rusticus. Average relative abundance indicated 9 species as ‘uncommon’, 14 species as ‘common’ and 7 species as very common in the studied wetland. According to the Shannon index, the diversity of macro invertebrates recorded in Lan-Kuu freshwater wetland, Myanmar, was high, (2.746-3.016), and so was the evenness (0.888-0.956).

abundance of some aquatic macro invertebrates in Kan Thone Sint Lake of Pathein Township, Ayeyarwady Region in Myanmar (Ahmad et al., 2018). She recorded eight species of order Hemiptera, three species of order Decapoda and Caenogastropoda, two species of order Odonata, Diptera and Coleoptera, and one species each of Araneae, Amphipoda and Hygrophila under phylum Arthropoda. Among them, nine species were observed in the open water, six species were recorded in the surface water and attached to the aquatic plants and only three species were recorded from the bottom dweller.
The highest number of species Gerris remigis was recorded. The highest value of species richness index was (741.596) in site IV and Shannon index (2.522) in site III were observed in Kanthonesint Lake. The objectives of the present research were to -1) Identify and record the occurrences of macro invertebrate species in freshwater wetland, 2) Evaluate the diversity and other related features of the macro invertebrates community in the wetland and 3) Document habitat characteristics and comment on the opportunities for their conservation.

MATERIALS AND METHODS: Study area
The selected study area was the Lan-Kuu freshwater wetland in Mingin Township, Sagaing Region in Myanmar. Mingin is a town on the Southern side of the Chindwin River in Kale District in Sagaing Division of Burma (Myanmar). Mingin Township is situated between Latitude 22˚ 55́ 30̋ N & 94˚ 37́ 0̋ E. Lan-Kuu wetland is about 2 miles from the Mingin Township, near Auk Satha village (Fig 1).

Wetland Plants
There are many macrophytes such as water hyacinths, cattails, hydrilla, duckweed, willow trees and grasses in LanKuu freshwater wetland. The depth of water is a primary determinant of their distribution. As water levels in many wetlands change seasonally and from year to year, most wetland plants grow in varying water depths, including no standing water at all (Cook et al., 1974;Cook 1990Cook , 1999. There are also paddy fields, and farms cultivating sesame, groundnut, and beans are near the LanKuu freshwater wetland.

Sampling of macro invertebrates
Macro invertebrate samples were collected once a month from the study site during the study period from June (2020) to January (2021). A net made of bamboo and wood, and insect nets, were used to collect samples from four different habitat typessurface water, water column, macrophytes, and the bottom. The external morphological characters and coloration of each specimen were noted immediately, morph metric measurements were conducted, and photographs were taken. The collected specimens were then counted and preserved in plastic boxes for identification and detailed studies.

Data Analysis
Relative abundance Relative abundance was analyzed following Bisht et al. (2004).

Number of individual species
Relative abundance = Total number of all species in a particular site uC = Uncommon (having relative abundance less than 0.0100) C = Common (having relative abundance of 0.0100 and above but less than 0.0500) vC = Very common (having relative abundance of 0.0500 and above).

Estimation of species diversities
Three indicesspecies richness, Shannon index, and evennesswere used to assess the species diversity of macro invertebrates (Krebs, 2001;Stiling, 1999). Species richness (S) is indicated by the number of species in a sample. The formula of Shannon index of species diversity is as: Where, Pi is the proportion of individuals found in the ith species Ln is the natural logarithm. A high number of species a more even distribution both increase diversity as measured by the Shannon index (Stilling, 1999). The Shannon index has a minus sign in the calculation so the index actually becomes positive. The higher number of species and a more even distribution both increase diversity as measured by the Shannon index. The actual diversity and the maximum possible can be compared by a measurement called the evenness value. The formula is - Where, S is total number of species. Evenness is usually range between 0 and 1.0.

RESULTS: Species Composition
A total number of 30 species of 27 genera belonging to nineteen families and eleven orders under five classes of three phyla of freshwater invertebrates were recorded in Lan-Kuu wetland. The highest number of species was found in phylum Arthropoda (77%) followed by phylum Mollusca (20%) and phylum Annelida (3%) in study site during study period. The highest numbers of orders were found in Hemiptera (23%) and lowest numbers of Hymenoptera, Araneae, Decapoda and Opisthopora (3%, each) in Lan-Kuu wetland ( Table 1,

Occurrence of macro invertebrates
The highest population of macro invertebrates (265 individuals) was recorded in January, closely followed by December (262 individuals), while the lowest (178 individuals) was recorded in June. Dytiscus verticalis was the predominant species (with total 185 individuals), 50 of which were recorded during December-January, while Arocatus rusticus was the rarest (with only two individuals) ( Table 2).

Distribution of macro invertebrates
In the present study, a total of 30 species were recorded in different habitat types of the wetland. Among them, three species each were observed in the surface waters and in the water column, while 17 species were attached to the macrophytes and seven species were recorded from the bottom zone. (Plate 2 and Table 3)

Relative abundance of macro invertebrates
The relative abundance of specimens revealed that nine species were uncommon, 14 were common, and seven were very common in the studied wetland ( Table 2).  Tarebiagranifera  ----2  2  5  3

Species diversity of macro invertebrates
Minimum 20 species were observed in July, while the maximum numbers of species (27 species) were observed in December. The Shannon diversity index was minimum (2.746) in January and maximum (3.016) in December ( Table 4 and Fig 3 to 5). It is interesting to note that while both the species richness and the diversity peaked in December, the evenness peaked in July (0.956) when the diversity was low, and the species richness was the lowest. Both the diversity and the evenness are lowest in January.

Climatic variations at the study site
The monthly temperature (°C) and rainfall (mm) were obtained from the Department of Meteorology, Mingin, for all the months between June 2020 and January 2021. The ambient temperature (maximum) ranged between 30.5°C-39.0°C and ambient temperature (minimum) between 8.7°C-22.0°C. The maximum and minimum temperatures, otherwise reasonably stable over the summer months, declined between November 2020 and January 2021, the winter season. Rainfall was recorded every month, except December 2020, with a maximum of 167 mm in July ( Table 5 & Fig 6).

Physicochemical parameters of water
The water temperature ranged from 30°C to 40°C, the pH values were between 7.4 and 9.0, while dissolved oxygen content ranged from 7.0 to 12.0 mg/l ( Table 6 and Fig 7 to 9). The lowest pH value was recorded in August, whereas the highest value was recorded in September.

DISCUSSION:
Species richness, evenness, and the Shannon diversity remained relatively high throughout the study period in the Lan-Kuu freshwater wetland, with a slight increase in the richness and diversity exhibited during the winter months, particularly in December.     The total macro invertebrate population was also reasonably consistent throughout the study period but peaked in December-January. While the ambient temperature was lower during the winter months, perhaps the lack of rainfall in December 2020 accounts for the increase in total population, species richness, and diversity of macro invertebrates. Water regimes, particularly permanence and hydro periods, are the prime determinants for wetland macro invertebrate diversity (Gleason and Rooney, 2018). The distribution of aquatic macro invertebrates within and among wetlands is also affected by water chemistry, especially pH and salinity, temperature, and oxygen levels. Dissolved oxygen is one of the critical factors affecting invertebrate abundance and diversity (Thorp et al., 1991). Temperature and pH also affect the abundance and diversity of invertebrates (Covich et al., 1999). Of the 30 species encountered, 17 were associated with macrophytes. However, none of these has the potential to become pests. While snails from the genus Pomacea are common in the Lan-Kuu wetland, the potential pests such as the golden apple snail (Pomacea canaliculata) or the island apple snail (Pomacea insularum) are notable by their absence. These pest species, initially introduced in Asia-Pacific from their native habitat in South America around the 1980s, can significantly reduce macrophytes and paddy biomass, shifting the wetlands towards an algal dominated system. It is not just the absence of pests but the presence of diverse species that draw special attention to this wetland. Even at the order level, the dominant group (Hemiptera) constitutes barely more than a quarter of the total macro invertebrate assemblage. The species diversity index combines species richness and evenness indices into a single quantity (Yazdian et al.,  2014). The consistently high values of the macro invertebrate diversity are perhaps best explained by the permanence of the water body, supported by regular pH pH rainfall in the Lan-Kuu freshwater wetland. The lack of rainfall in December supports this idea since there is a marked change in the diversity of macro invertebrates in January.

CONCLUSION:
The Lan-Kuu freshwater wetland has emerged as a mature habitat for diverse macro invertebrates, indicating robust ecosystem functions that merit conservation initiatives. As the base of the ecological food chain is diverse and productive, the possibility of Lan-Kuu freshwater wetland to attract waterfowl is high, opening up possibilities for ecotourism in the region. The introduction of tourism will benefit farmers in the region who may have lost their paddy fields to the wetlands and have shifted to fisheries and waterfowl capture. The key hydrologic driver of the Lan-Kuu freshwater wetland appears to be rainfall, which means that conservation efforts may be limited to protecting it from either over-extraction of biological material or introducing pest species into the system. However, there is a strong need to continue monitoring its biological diversity, particularly those of the macrophysics and the macro invertebrates.

ACKNOWLEDGEMENT:
Firstly, I wish to greatly express my gratitude to my supervisor Dr. Somnath Bandyopadhyay, Associate professor, School of Ecology and Environmental Studies (EES), Nalanda University, India for his guidance, cooperation and advice throughout the study period. Secondly, I am grateful thank to my younger sisters and brothers for helping in collection of specimens. Last, I wish to express my deepest gratitude to my parents for their kindness and helping in collection of specimens throughout the period of this work.

CONFLICTS OF INTEREST:
The author declares there is no conflict of interest to publish it.