khu hệ giun đất ở đồng bằng sông cửu long, việt nam bản tóm tắt tiếng anh

INTRODUCTION
1. THE IMPORTANCE OF PROBLEM
Earthworms are soil invertebrates appeared on the Earth 600 million years ago. Most members of the Earthworms are
terrestrial and least semi-aquatic. They belong to class Oligochaeta of phylum Annelida (Edwards & Bohlen, 1996).
Earthworms play the important roles in soil physical, chemical, and biological characters. The earthworms have high
protein, so they are suitable as feed for fish, poultry and cattle. In the folk medicine of our country and many countries
around the world, earthworms are used to treat certain diseases such as malaria, smallpox, asthma, arthritis, epilepsy,
jaundice, stones in the bladder, They are also indicators of change, the origin of a regional soil and soil characteristics.
Earthworms also hold an important position in the evolution of animals from water to land, that can help us visualize the
formation of species, subspecies and evolution of the system of animal organs. In addition, some earthworms are
intermediate hosts of some parasitic nematodes such as Metastrongylus, Stephanurus dentatus. (Thai Tran Bai, 1983, 1989;
Edwards, 2004; Georgescu et al., 2011).
In Vietnam, earthworms are one of the groups of animals were studied very early (Perrier, 1872, 1875). So far, the
research earthworm fauna in North and Central have nearly completed but only a few studies in The Mekong Delta.
Therefore, we will study “The Earthworm fauna of The Mekong Delta, Viet Nam”.
2. RESEARCH OBJECTIVES
1. To study the species richness, establish catalogue, analyze fauna characteristics, build keys and determined the
relationship of some species earthworms in The Mekong Delta.
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2. To study on distribution characteristics of earthworms in different topography types, biotypes, seasons and stratums
(depths) in the study area.
3. To survey on use of the earthworms in The Mekong Delta and to suggest the direction for the exploitation and use
them in the future.
3. SCOPE AND LIMITATIONS
This study was conducted at The Mekong Delta, not including the islands in the sea. The data in this PhD. thesis are
summarized on the basis of the research from 2009 to 2011 and inherited from the master thesis myself (from 2007 to 2008).
This study has used a classification system of Kinberg (1867) for Pheretima genus, to wait for a new classification system
more satisfactory.
4. PRACTICAL AND SCIENTIFIC SIGNIFICANCE OF RESEARCH
This study will provide fully and accurately about species composition and distribution characteristics of earthworms
of The Mekong Delta that contributes to complete the earthworm fauna of Vietnam. It will provide data about fauna

characteristics, and key to the species of earthworms in The Mekong Delta, that serves well for teaching and scientific
research in the future.
This study will provide an overview of the use and actual needs. On the basis, that will be the exact orientation for the
exploitation and use of earthworms in the Mekong Delta.
This research will provide data about copulatory pouches and molecular biology (DNA barcode) of some earthworms
of genus Pheretima that is a useful source of information to rebuild the classification system for this species group in the
future.
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CHAPTER 1: LITERATURE REVIEW
1.1. RESEARCH SITUATION OF EARTHWORM FAUNA IN THE WORLD
Studies on earthworm fauna have been performed widely in many countries and territories worldwide. According to
Blakemore (2002), the earthworm fauna of Europe and North America have been researched the most complete, followed by
the Australian of earthworm fauna, the Asia of earthworms fauna have also been researched by many authors, especially
Southeast Asia, but the fanua earthworms of Africa are still little known.
Particularly in Southeast Asia, there are also many researches on the earthworm fauna but not uniform in all countries.
Diversity of species and the authors studied earthworms in some neighboring countries of Vietnam are summarized in table
2.1.
Table 2.1: Diversity of species and the authors studied earthworms of some neighboring countries of Vietnam.
No. Countries
Diversity of species
The authors studied earthworms
Family Genus Species
1. China 8 22 248
Stephenson (1912), Michaelsen (1931), Chen (1933, 1935, 1938, 1946),
Gates (1935a, 1935b), Huang & et al. (2007),…
2. Myanmar 10 54 195 Gates (1972), Blakemore (2006),…
3. Thailand 5 7 49
Gates (1939, 1972), Skawsang (2003), Kosavititkul (2005), Chantaravisoot
(2007), Somniyam (2008), Bantaowong & et al. (2011),…
4. Laos - - 73

Thai Tran Bai & Samphon (1988, 1989, 1990a, 1990b, 1991a, 1991b), Hong
(2008), Inkavilay et al. (2009) và Chanabun et al. (2011),…
5. Cambodia - - 15 Thai Tran Bai & Do Van Nhuong (1989, 1993)
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1.1. RESEARCH SITUATION OF EARTHWORM FAUNA IN VIETNAM
The earthworm fauna of Vietnam was started to research in the late 19
th
century by Perrier (1872, 1875). Until the
early 20
th
century, there were more some works of foreign authors. Stephenson (1931) published two new science species
which were collected in the Langbiang Plateau. Michaelsen (1934) presented sixteen species which were found in Da Lat,
Quy Nhon, Da Nang, Phu Quoc Island, Phu Tho, and then is the research of Omodeo (1956). Overall, these works are
scattered, where researchers are often the cities and tourist destinations in the Southern Vietnam.
From 1965 to 1975, the study of earthworms was interrupted by war, and was only conducted limited in some areas.
The collected data was morphology and ecology of several widely distributed species to service for teaching (Thai Tran Bai,
1983).
Since 1979, the earthworm fauna of Vietnam has been studied widely and systematically. The first was the PhD.
Thesis of Thai Tran Bai (1983) “Earthworm of Vietnam (Systematic, Fauna, Distribution and Zoogeographic)”. The results
of this study show that there are 109 species and subspecies, belonging to 6 families and 17 genera for the earthworm fauna
of Vietnam. Among of them there are 39 species and subspecies new for science. Then, he guided several PhD. thesis on the
earthworm fauna in Vietnam (table 2.2).
Table 2.2: The author, location, research results of 6 Ph. D theses on the fauna earthworms of Vietnam.
Year Authors Location
Results New
species*
Species* Genus Family
1985 Tran Thuy Mui The Red Delta 32 12 7 0
1994 Do Van Nhuong Northwest 95 7 6 15
1994 Nguyen Van Thuan Binh Tri Thien 54 9 6 5

1995 Pham Thi Hong Ha Quang Nam Da Nang 48 8 4 6
4
1995 Le Van Trien Northeastern 72 11 5 5
1996 Huynh Thi Kim Hoi South Central 75 14 6 8
* species and subspecies
According to Thai Tran Bai (2000b) and updated, so far the earthworm fauna of Vietnam has been found 204 species
and subspecies, 18 genara, of 7 families. Among them, Family Megascolecidae has most various species with 181 species
and subspecies, followed by Ocnerodrilidae (7 species), Octochaetidae (6 species), Moniligastridae (5 species), Lumbricidae
(2 species) and 2 remaining families (Glossoscolecidae, Microchaetidae) with 1 species of each. There are 25 species of
earthworms and many taxa not identified the scientific name in the South of Vietnam. In particular, the Mekong Delta
mainland only recorded 14 species of earthworms, belonging to 8 genera, 5 families and a few taxon of the genus Pheretima
and Drawida not be identified to species.
Most the earthworm sampling points in Vietnam is shown in Figure 1.1, through which to see the sampling points are
concentrated in the North and Central of Vietnam, The earthworm fauna of Southern has been little studied. In addition, the
sample concentrated mainly in the plain, less than in the hills and very few in the islands.
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Figure 1.1: The sampling earthworms in Vietnam
(According to Stephenson (1931), Michaelsen (1934b), Omodeo (1956), Thai Tran Bai (1983), Tran Thuy Mui (1985), Do Van Nhuong (1994),
Nguyen Van Thuan (1994), Le Van Trien (1995), Pham Thi Hong Ha (1995), Huynh Thi Kim Hoi (2005), Nguyen Thanh Tung (2008), Nguyen Van
Thuan and Nguyen Thi My Hang (2010), )
CHAPTER 2. LOCATION, TIME,
MATERIALS AND METHODS RESEARCH
2.1. LOCATION AND TIME RESEARCH
6
Based on the differences in the impact of hydrology and soil properties (mechanical composition, pH and salinity),
the earthworm sampling points in the Mekong Delta are arranged in 4 topographies: mountainous, river alluvial plains,
down warping far from the river basin and coastal mixed. According to Thai Tran Bai (1983), the Mekong Delta is divided
into biotypes: natural forest, planted forest, mango gardens at the foot of the mountains, wilderness, the edge of the river or
pond, perennial garden, short-day crops garden and livestock.
A total of 187 sampling points were collected of 13 provinces and cities in the Mekong Delta. The sampling points

concentrated in the Tien and Hau River basin, less than down warping far from the river of Dong Thap Muoi, Long Xuyen
Quadrangle and Ca Mau Peninsula for flooded during the year (Figure 2.4).
Earthworm samples were collected quantitatively and qualitatively from 2007 to 2011. Each year collected in two
different seasons: the dry season from January to June, rainy season from July to December, but focus on October and
November is the time of many earthworms has more mature individual (especially in the mountains).
2.2. MATERIALS AND METHODS RESEARCH
2.2.1. Materials
This study was based on analysis of 2,868 individuals earthworms, of which 15,447 individuals collected in 1,109
quantitative pit. The sample is hold at the Laboratory Animals, Can Tho University and Soil Organism Research Center,
Hanoi National University of Education.
Tools and equipment include canvas bags, paper label, measure, GPS (Garmin, Japan), electronic balance (accuracy
0.01 g), microscope and surgical kits, and more instruments and apparatus for DNA extracted and sequenced.
7
Figure 2.4: The sampling earthworms in the Mekong Delta
Chemical fixed earthworms of 2% formaldehyde, formaldehyde 4%, alcohol 96%. In experiments extracted and
sequenced using a variety of different chemicals and primers LCO1490, HCO2198, COI-E to PCR the DNA barcode.
2.2.2. Methods Research
Quantitative samples were collected as soil organism of Ghiliarov (1976). Qualitative sampling were collected in
parallel with quantitative sampling in the same place or can be obtained at any location with a wider range.
The samples were washed in water, killed with 2% formaldehyde solution, to align in the box with 4% formaldehyde
solution about 24 hours for morphological analysis. Samples used for DNA extraction were fixed with 96% alcohol solution.
Earthworms of the Mekong Delta are identified base on keys and descriptions by Thai Tran Bai (1986), Gates (1972),
Blakemore (2002), Sims and Easton (1972), Easton (1979),… In addition, many taxa were questionable about the position
classification which were assessed by Prof. Doctor Thai Tran Bai.
Morphological - ecological groups of earthworm were divided by Thai Tran Bai (1983). The origin and dispersal of the
major terrestrial earthworm families was determined by Hendrix et al. (2008). Oriental divided into two regions and the
provinces on the basis of Thai Tran Bai (1983). The close species composition between the faunas and Radulescu (1961).
The close species composition between the earthworm fauna in the Mekong Delta with other fauna calculated as of Stugren
and Radulescu (1961). Diversity index was calculated according to Shannon and Weiner (1963) and "Eveness index"
according to Pielou (1966).

Taxonomic relationships of earthworm species in the Mekong Delta was determined by morphological characteristics
using numerical phenetics and Cladistics methods based on DNA barcode sequences.
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CHAPTER 3: RESULTS AND DISCUSSION
3.1. THE EARTHWORM FAUNA OF THE MEKONG DELTA
3.1.1. Checklist earthworm of the Mekong Delta
Table 3.1: List and frequency of earthworms in the different topography of the Mekong Delta
No. Taxon
Frequency (C)
VN
ĐBPXVS
BTXS
HHVB
Total
GLOSSOSCOLECIDAE (Michaelsen, 1900)
Pontoscolex Schmarda, 1861
1. Pontoscolex corethrurus (Müller, 1856) 0.75 0.66 0.85 0.62 0.69
MEGASCOLECIDAE (part Rosa, 1891)
Lampito Kinberg, 1866
2. Lampito mauritii Kinberg, 1866 0.08 0.04 0.04 0.44 0.14
Perionyx Perrier, 1872
3. Perionyx excavatus Perrier, 1872 0.12 0.07 0.09 0.10
Pheretima Kinberg, 1867
Coecata
4. Pheretima anomala Michaelsen, 1907 0,63 0,08
5. Pheretima bahli Gates, 1945 0.50 0.13 0.36 0.21
6. Pheretima californica Kinberg, 1867
***
0.13 0.07 0.03
7. Pheretima houlleti (Perrier, 1872) 0.08 0.59 0.25 0.47 0.45

8. Pheretima juliani (Perrier, 1875) 0.10 0.05
9
9. Pheretima peguana Rosa. 1889 0.38 0.09 0.16 0.13
10. Pheretima polychaetifera Thai, 1984 0.27 0.35 0.07 0.21
11. Pheretima posthuma (Vaillant, 1868) 0.13 0.58 0.19 0.56 0.47
12. Pheretima mangophila Nguyen, 2011
*
0.54 0.04 0.09
13. Pheretima thaii Nguyen, 2011
*
0.02 0.01
14. Pheretima sp. 4 0.17 0.02
15. Pheretima sp. 5 0.07 0.02
16. Pheretima sp. 6 0.02 0.01
17. Pheretima sp. 7 0.02 0.01
18. Pheretima sp. 8
(1)
0.54 0.28 0.04 0.18 0.26
19. Pheretima sp. 9 0.13 0.02
20. Pheretima sp. 11 0.63 0.08
21. Pheretima sp. 12 0.25 0.03
22. Pheretima sp. 13 0.13 0.02
23. Pheretima sp. 14 0.04 0.01
24. Pheretima sp. 15 0.13 0.02
Acoecata
25. Pheretima elongata (Perrier, 1872) 0.59 0.35 0.38 0.38
26. Pheretima taprobanae Beddard, 1892
***
0.01 0.01
27. Pheretima sp. 16 0.21 0.03

Pontodrilus Perrier, 1874
28. Pontodrilus litoralis (Grube, 1855) 0.02 0.01
ALMIDAE Duboscq, 1902
Glyphidrilus Horst, 1889
(2)
29. Glyphidrilus papillatus (Rosa, 1890) 0.08 0.01 0.04 0.03
MONILIGASTRIDAE Claus, 1880
Drawida Michaelsen, 1900
30. Drawida barwelli (Beddard, 1886)
**
0.25 0.19 0.12 0.14
31. Drawida sp. 1 0.13 0.22 0.12 0.14
32. Drawida sp. 2 0.17 0.02
OCNERODRILIDAE Beddard, 1891
Gordiodrilus Beddard, 1892
10
33. Gordiodrilus elegans Beddard, 1892 0.20 0.05
OCTOCHAETIDAE Gates, 1959
Dichogaster Beddard, 1888
34. Dichogaster bolaui (Michaelsen, 1891) 0.08 0.25 0.04 0.18 0.18
Total of species 23 19 11 17 34
*: new species for science; **: new species for Vietnam; ***: new species for the Mekong Delta; Frequency calculated by table I 2 – appendix I; (1):
Previously, this species was recorded in Indochina with Ph . campanulata (Rosa, 1890); (2): according to Omodeo (2000) Glyphidrilus belonging to
Glyphidrilidae but now many authors put them to Almidae.
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3.1.3. Property of the fauna earthworm in the Mekong Delta
3.1.3.1. Species composition structure
So far, there have been recorded 34 species of earthworms, belonging to 9
genus, 6 families in the Mekong Delta. In particular, two new species for science
(Ph. thaii and Ph. mangophila), 1 new species for Vietnam (Drawida barwelli), 3

new species were found the first in the study area (Ph. anomala, Ph. californica
and Ph. taprobanae) and 14 taxa are new species waiting publication.
Genus Pheretima has 24 species (70.58%) dominate absolutely which was
consistent with the nature of the earthworm fauna of Indochina, was the original
distribution of the genus Pheretima. Next, Drawida has 3 species (8.82%), the
majority of these species in common in India - Malaysia but the distribution of
them including Vietnam. The remaining genera (Pontoscolex, Lampito, Perionyx,
Pontodrilus, Glyphidrilus, Gordiodrilus and Dichogaster) each have one species,
accounting for 2.94%.
In Pheretima genus, three species of the acoecata group, accounting for
8.82%, this rate is lower than the Quang Nam - Da Nang and South Central but
higher superior to the other fauna have been studied in our country. With 21
species of the coecata group, there are 3 species groups related to the Mekong
River Basin: posthuma species group (including 2 species: Ph. posthuma, Ph.
juliani), houlleti species group (including 4 species: Ph. houlleti, Ph. sp.8, Ph.
thaii and Ph. mangophila), especially peguana species group with 2 known
species Ph. bahli and Ph. peguana has discovered 5 new species is Ph. sp. 4, Ph.
sp. 9, Ph. sp. 11, Ph. sp. 14, Ph. sp.15, Therefore, it is possible to predict the
Mekong Delta is the homeland for this species group. From the data on
morphological, histological structure and molecular biology shows that Ph.
pacseana not belonging to peguana species group.
Based on frequency of the earthworm species in the Mekong Delta is
divided into three different groups: common group 1 species 2.94% (Pontoscolex
corethrurus), rare group 4 species 11.76% (including Ph. houlleti, Ph. posthuma,
Ph. sp. 8, Ph. elongata), the remaining 29 species (85.94%) were classified as
random. By Thai Tran Bai (1987), Ph. bahli background species in the Mekong
12
Delta, but the frequency of this species (C = 21%) is lower than some other
species in the study area.
According to the division of the Thai Tran Bai (1983) about eco-

morphological groups, the earthworm of the Mekong Delta was divided into 3
groups. Litter group at least, there are three species accounted for 8.82%
(Perionyx excavatus, and Ph. thaii and Ph. mangophila). Next, mainly soil group
has 15 species accounted for 44.12% (Ph. elongata, Ph. taprobanea, Ph.
posthuma, Ph. sp. 5, Ph. sp. 7, Ph. sp. 13, Ph. sp . 15, Ph. sp. 16, Pontoscolex
corethrurus, Pontodrilus litoralis, Dichogaster bolaui, Gordiodrilus elegans,
Drawida barwelli, Drawida sp. 1 and Drawida sp. 2). Soils – litter group with 16
species accounted for 47.06% (all remaining species). This is consistent with the
natural characteristics in the Mekong Delta, a large area of plain human habitats
and forest habitat is concentrated in the high-elevation mountains, often eroded, so
the litter floor relatively small and thin. Therefore, the litter a very low percentage
compared to the other systems.
3.1.3.2. The relationship of the earthworm fauna of the Mekong Delta with
neighboring faunas
There are 12 species in the Mekong Delta were widely distributed all over
the world (Pontoscolex corethrurus, Perionyx excavatus, Drawida barwelli, Ph.
californica, Ph. houlleti, Ph. posthuma, Ph. elongata, Ph. taprobanae,
Pontodrilus litoralis, Gordiodrilus elegans, Dichogasterbolaui, Lampito mauritii),
3 species only found in South Asia or Southeast Asia (Glyphidrilus papillatus, Ph.
bahli and Ph. peguana), 2 species only found in Indochina (Ph. juliani and Ph. sp.
8), the remaining 17 species found in Vietnam or only o in the study area.
The earthworm fauna of the Mekong Delta have a relationship from
different to very different with neighboring faunas (R from 0.41 to 0.89).
However, this values only was relative becausse of the scope and level of
research was different from faunas. The earthworm fauna in the Mekong Delta
has 15 species (41.12%) similar with the southern central fauna, 11 species
(32.35%) with Binh Tri Thien and Northwest, 10 species (29.41%) with Thailand
and Quang Nam - Da Nang, 8 species (23.53%) with the fauna of Laos, Northeast
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and Phnom Penh. But the same is plain but the earthworm fauna in the Mekong

Delta only 7 species (20.59%) simalar with the Red River Delta fauna. Earthworm
species composition between the two areas of difference so far, if the Mekong Delta
characterize related species native to the Mekong River Basin (group species
posthuma, houlleti and peguana), the Red River Delta fauna was characteristics by
Ph. aspergillum, Ph. robusta, Ph. triastriata, Ph. morrisi (Thai & Tran, 1982).
Degree of proximity about species composition between faunas can be
considered dependent on many different factors but the most important is the
spreading factor and the ability to adapt of each species. Many species such as
Pontoscolex corethrurus, Ph. elongata, Ph. bahli, Ph. posthuma, high
adaptability to external conditions should be widely distributed in most of the
fauna. In the spreading factor may be noted factor in the flow of the river, this
shows quite clearly separate survey of native species from the Mekong River
Basin, from 4 to 6 species similar between in faunas, where have part of the
Mekong River Basin in passing but only from 1 to 4 species similar in faunas
where have not through the Mekong River Basin. Especially the fauna Red River
Delta and the North East together only 1 species (Ph. posthuma).
3.1.3.3. Zoogeographical nature of the earthworm fauna of the Mekong
Delta
Of the 34 species of earthworms have been found in the Mekong Delta,
about 11 species originated from various parts in the world: 3 species originated
from India (Lampito mauritii, Perionyx excavatus, Drawida barwelli) (Blakemore,
2002), 2 species originated from tropical Africa (Gordiodrilus elegans and
Dichogaster bolaui) (Hendrix & Bohlen, 2002) 1 species originated from tropical
America (Pontoscolex corethrurus), one species originated in the south of China
(Ph. californica) (Blakemore, 2002). Blakemore (2007) confirmed the original
distribution of Pontodrilus litoralis in the Mediterranean. In Pheretima group
without caeca, originating Ph. elongata was confirmed in Sumawa Islands, Lombok,
Bali, East Java (Easton, 1976) and originating Ph. taprobanae was predicted in the
tropics of Papua Guinea.
14

So far, there are no documents to identify the original distribution of
Glyphidrilus papilatus, this species was found very common in Vietnam (Thai,
200b), India, Myanmar, Hainan Island of China but have not found in Africa.
From the data on this can predict the original distribution of Glyphidrilus
papilatus was somewhere in the province of Indo – China or sub-domain
Zoogeographical of Indian - Myanmar.
The earthworm fauna in the Mekong Delta has Zoogeographical factors of
Oriental with 88.23%. This rate is lower than the North West (93.6%) and Quang
Nam - Da Nang (89.6%) but higher than the other fauna were studied in our
country such as: Binh Tri Thien (86.9%), Northeast (79.18 percent), South Central
(82.7%) and the Red River Delta (76%). In general, the Zoogeographical factors of
earthworms in the Mekong Delta follow the general rule of the earthworm fauna
in Vietnam, Oriental factor was predominant (Thai, 1983). In this zoogeographical
factor, Indo-China factors was the highest (24 species, 70.29%), followed by
India, Myanmar factors (4 species, accounting for 11.76%), the lowest factor
Malaysia (2 species, accounting for 5.88%). In addition, the earthworm fauna in
the Mekong Delta has more factors Etiopi 2 species (5.88%) and Neotropical and
Palearctic, 1 species (2.94%) for each. Although these two factors have very low
rates but the species have the ability to spread and wide distribution in the study
area.
According to Easton (1979), limited to the original distribution of the
Acoecata groups of our country only in the Central region but outside the two
exotic species is originating from the Malaysia provinces (Ph. elongata and Ph.
taprobanea) in the Mekong Delta was also found more Pheretima sp. 16, there
were distribution common in some of the mountain of Kien Giang and mountain
of To - An Giang, maybe this is endemic of the Mekong Delta. From that show,
the original distribution of the acoecata group (Polypheretima) at our country can
be expanded further to the South, Vietnam.
3.1.4. Taxonomic relationships between earthworm species in the Mekong Delta
3.1.4.1. Taxonomic relationships based on morphology

15
The dendrogram constructed from the similarity matrix of 34 taxa showed
that 34 species could be grouped into two big groups. Group I: included 5 species
belongs to families Glossoscolecidae, Almidae, Moniligastridae. With 3
earthworm species of the genus Drawida form a separate sub-group with a
similarity index of about 85%. Drawida sp. 1 near with Drawida sp. 2 (93.33%)
than Drawida barwelli (83.33%). Group II consists of the remaining 29 species
belonging to three families Ocnerodrilidae, Octochaetidae, Megascolecidae. Of
these, 2 species of Ocnerodrilidae and Octochaetidae and 3 species genus
Lampito, Perionyx, Pontodrilus of Megascolecidae family form a separate group
(sub-group II.1) distinguished group comprising the species genus Pheretima (sub-
group II. 2) with an average coefficient of similarity between them is about 53%.
Figure 3.37: A dendrogram generated using UPGMA method with arithmetic
average analysis of 34 taxa based on the analysis of morphological traits
On dendrogram constructed of earthworm species in the Mekong Delta,
shows quite clearly relationships of the close of group species. The species in
groups peguana form a sub-group own (except Ph. sp. 14), in which Ph. bahli
close to Ph. sp. 4 and Ph. sp. 11 close to Ph. peguana (similarity coefficient of
16
Nhóm
houlleti
Nhóm
peguana
Nhóm
posthuma
Nhóm không
có manh
tràng
Họ OCNERODRILIDAE
Họ OCTOCHAETIDAE

Họ MEGASCOLECIDAE
Họ GLOSSOSCOLECIDAE
Họ ALMIDAE
Họ MONILIGASTRIDAE
I
II.1
II
Nhóm
houlleti
II.2
Pheretima polychaetifera
96.77%) more than with Ph. 2, Ph. sp. 9, Ph. sp. 15, Ph. posthuma and Ph. juliani
heading posthuma species group form a separate with similar coefficients of up to
93.55%, this group was more close to Ph. sp. 12 than other Pheretima species of
the Mekong Delta. Ph. thaii and Ph. mangophila were predicted group species
houlleti but they separated from 2 species in this group were Ph. houlleti and Ph.
sp. 8, especially Ph. houlleti and Ph. sp. 8 close to the Ph. californica than two
species have been predicted in the same species group, it is important to review
the taxonomic position of the species in this group. However, on dendrogram
constructed acoecata of Pheretima species group create a group completely
separate species are at the coecata. Ph. elongata and Ph. sp. 16 form a separate
group with a similarity coefficient of 83%, Ph. taprobanae separate early and
close to Ph. sp. 13 more than 2 species (Ph. elongata and Ph. sp. 16) group.
3.1.4.2. Taxonomic relationships based on molecular biology
Barcode DNA sequence analysis experiments have been successful on 19
species of earthworms in the Mekong Delta and 1 species of Laos (Ph. pacseana),
Only Ph. taprobanae has been sequenced in previous studies (in the gene bank
database) (Minamiya et al., 2009). The maximum parsimony tree based on DNA
barcodes data are drawn as in figure 3.39 with CI (Consistency Index) = 0.3363,
RI (Retention Index) = 0.3215, this index shows the results relative and

acceptable. According to the maximum parsimony tree shows the earthworm
species in the Mekong Delta can be divided into three major groups with the
bootstrap different indicators.
Group I: included 2 species Pontocolex corethrurus and Pontodrilus
litoralis with 74% bootstrap index. Among them, Pontocolex corethrurus belongs
to Glossoscolecidae assigned to other families in the two groups but Pontodrilus
litoralis unstable position classification, by following on Acanthodrilidae or
Megascolecidae (Blakemore, 2007).
Group II: consist of Glyphidrilus papillatus belongs to Almidae family and
Drawida sp. 1 of Moniligastridae family distinguished with all species belongs to
Megascolecidae in group III with low bootstrap index (23%). However, this group
did not include Drawida sp. 2 were classified in the same group of species of the
17
III
74
23
25
37
27
38
28
5
18
61
64
30
24
32
8
100

4
II
Nhóm
loài
peguana
Nhóm loài
houlleti
Nhóm
không có
manh tràng
Pheretima polychaetifera
I
*
*
*
genus Pheretima, may be to errors in the sequencing process.
Group III: includes all species of the genus Pheretima and Drawida sp. 2. In
this group, the 4 species of peguana group (Ph. sp. 4, Ph. bahli, Ph. peguana and
Ph. sp.15) form a separate group of Ph. sp. 10, with only 28% bootstrap. However,
Ph. sp. 14 was also belongs to peguana species group was not classified in this
group but it and Ph. sp. 13 was group with bootstrap index of up to 100%. In
addition, Ph. houlleti and Ph. sp. 8 classified a group with 61% bootstrap index. Of
3 species of acoecata of Pheretima group, only Ph. elongata and Ph. taprobanae
were classified in the same group (64%) close to Ph. posthuma than Ph. sp.16.
Figure 3.39: Maximum parsimony analysis of a 639 bp fragment of the COI gene
after combination of partial COI sequences from the GeneBank
Figure 3.39 shows coecata of Pheretima group had male pore on the surface
of the body tend to close together but did not form a separate group, but the
relationship of the species group close with coecata of Pheretima group but it was
not clear, this prolem have also been found in several other studies ( Huang et al.,

2007b) . However, from rhe maximum parsimony tree based on DNA barcodes
data also confirmed the taxonomic position of some unidentified taxon names.
3.2. DISTRIBUTION CHARACTERISTICS OF EARTHWORMS IN THE
MEKONG DELTA
18
In the Mekong Delta, density of earthworms was 48 ind/m
2
and biomass
was 35.69 g/m
2
. Although it is an exotic species but Pontoscolex corethrurus
dominant in the fauna with n% = 0.30 and p% = 0.15, followed by Ph. posthuma,
Lampito mauritii, Ph. elongata, Ph. houlleti, Ph. bahli and Ph. sp. 11 (n% = 0.04 -
0.08), the remaining species was low to very low (n% ≤ 0.02).
3.1. Distribution features of earthworms in different topography areas

Figure 3.40. Density, bio-mass and number of earth worm species in different
geographical forms in the Mekong Delta.
Indicator of variety and indicator of average number of earthworms in
mountainous areas are higher than that of delta areas but a reverse situation for the
indicator of biomass. This correlates with previous studies of earthworm
distribution in Vietnam. A comparision among 3 deltaic geographical forms showed
that indicator values of species number, variety, density and biomass gradually
decreased from DBPSVS to HHVB and followed by BTXS. Because the majority
of soil in BTXS and HHVB is aluminous, heavy aluminous and saline, only salt and
pH -adapted earthworm species can survive and grow there. Moreover, the fact that
ground surfaces in BTXS are almost flooded around the year is a factor to limit the
variety of earthworms in this region.
In all earthworm species have been found in the Mekong Delta, 6 species
have been occurred in all geographical forms (Pontoscolex corethrurus, Ph.

houlleti, Ph. posthuma, Ph. sp. 8, Dichogaster bolaui, Lampito mauritii), 10
species only showed up in Vietnam (Drawida sp. 2, Ph. sp. 4, từ Ph. sp. 9 → sp.
16), 2 species only appeared in ĐBPSVS (Ph. sp. 7, Ph. juliani) and 1 species only
19
Mật độ (con/m
2
), sinh khối (g/m
2
)
C
h
ỉ

s
ố

đ
a

d
ạ
n
g
showed up in HHVB (Ph. sp. 6 ). In the remaining species, it is noticeably that
there are some species interruptedly appeared in a specific geographical form such
as: Ph. bahli and Ph. Peguana (not in BTXS, it is likely that they are not aluminous-
adapted species; Drawida barwelli and Drawida sp. (not in HHVB areas, it is likely
that they have low tolerances of salinity. Ph. elongata and Perionyx excavatus and
Ph. polychaetifera are not found in Vietnam. The exchanging of species composition
among different geographical forms is also clearly observed in some cases in The

Mekong Delta, such as: Ph. posthuma, Ph. mangophila and Lampito mauritii.
3.2.2. Distribution features according to season
In The Mekong Delta, with the specific feature of raining and dry season,
the mean of average temperature change is low, about 3 – 3,5
0
C. Therefore
humidity is the main factor that directly influences on seasonal distribution of
earthworms in this area. Density and biomass of earthworms in dry season (n = 38,1
con/m
2
; p = 16,22 g/m
2
) is lower than that in raining season (n = 61,2 con/m
2
; p =
43,35 g/m
2
), generally and specifically for two geographical forms.
Figure 3.42. The changes of species number, desity (individual/m2), biomass (g/m
2
)
(A), mature and immature individuals (B) in different seasons in An Giang
mountainous areas
A specific investigation of seasonal changes of earthworms distributed in
some mountains in An Giang province showed that there is a gradual increase of
species number, density and biomass of earthworms from dry season to end of
raining season (figure 3.42 A). In addition to this, the rate of mature earthworms in
the population also steadily climbed up from the dry to end of the raining season.
20
A B

Especially at the end of raining season, the majority of individuals of the
population are mature (figure 3.42 B). Therefore, it can be showed that there is a
correlation of humidity and life cycle of some earthworm species in The Mekong
Delta. At the end of raining season, when the soil humidity drops down, the
mature individuals start to reproduce and then die. Cocoons will be kept during the
next dry season when soil humidity is lowest. At the early of the raining season,
when the soil humidity gradually increases, cocoons begin to hatch and develop
during the raining season. The above procedure is repeated every year.
From the results and rules of changes in the species number towards
seasons of 7 earthworm species in Cai Rang District-Can Tho city, it has been
showed that earthworm species in The Mekong Delta are divided into two groups:
a group having long life cycle in years and a group having short life time.
3.2.3. Distribution features in biotypes
According to classification system of Thai Tran Bai (1983), The Mekong
Delta is comprised of 7 biotypes: natural forest, artificial forest, fallow, water edge
(river bank, rice field bank, canal bank), long year cultivated land, short time
cultivated land, animal feeding land. Besides, with specific characteristics, the
ecosystem of mango gardens at mountain bases is separated from the ecosystem of
long year cultivated land. When taking the relationship of variety, density and
biomass indicators of 8 above biotypes into account, the result showed that these
values randomly change without rules as indicated in previous studies (Figure
3.44A).
This is reasonable because the majority of biotypes in The Mekong Delta
derived from the separation of artificial biotypes. Therefore, it is challenging to
identify the level of human impact in each ecosystem and among them. From that
reality, it can be grouped some biotypes in The Mekong Delta a bigger group in
accordance with the level of human impact as follows: group of extremely low
human impact (including natural forest and cultivated forest), group of low human
impact (including fallow and water edge), group of average human impact (mango
forest at mountain base), group of high human impact (including long term and

short term cultivated land), group of very high human impact (feeding land).
21
According to the above separation of biotypes, the value of variety indicator
gradually decreases depending on the level of human impact, while density and
biomass increase as indicated in previous studies. One only exception is that the
group of average human impact has lower density (n = 50,3 con/m
2
) than group of
low human impact (n = 53,9 con/m
2
); however this disparity is not significant.
Figure 3.44. The relationship among indicators of variety, density and biomass in
original biotypes (A) and among human impacted biotypes (B).
3.2.4. Distribution features according to stratums
In the Mekong Delta, earthworms can distribute from A1 level to A6 level
(from 0-60 cm) but mainly in A1 level (n = 80,53% – 88,32%; p = 80,06% – 90,37%).
Preliminary studies in Vietnam showed that earthworms can distribute down to A5
level (above 50 cm). In The Mekong Delta, they can spread down to A6 level in spite
of low rate (n = 0,03%; p = 0,21%). In raining season earthworms live from A1-A4
and tend to move down deeper into the ground in dry season (down to A6 level) due to
the decreased humidity in the surface level. Distribution features in accordance with
22
A
B
Mật độ (con/m
2
) và sinh khối
(g/m
2
)

Mật độ (con/m
2
) và sinh khối
(g/m
2
)
C
h
ỉ

s
ố

đ
a

d
ạ
n
g
C
h
ỉ

s
ố

đ
a

d
ạ
n
g
depth of earthworms in the Mekong Delta depends on different factors such as: season,
habit, depth of surface level and development phase (Ph. juliani).
Surface level has influenced on the capability of the Mekong Delta
earthworms to distribute in various depth that can be clearly shown when
comparing among different geographical forms. ĐBPSVS earthworms can dwell
deeply within a range of 10 cm to 60 cm which is the thick surface having good
environmental conditions (this is the area having most orchards in the delta). VN
and HHVB earthworms can live in the level of 10 cm-20 cm because stone
stratums underneath preventing them to move down further. In HHVB area,
salinity would be the main factor to limit the distribution of earthworm in depth,
followed by the iron content which is also a remarkable factor.
3.3. PROBLEM USE EARTHWORMS IN THE MEKONG DELTA
3.3.1. The state of eathworms use in the Mekong Delta
In The Mekong Delta, earthworms have been used widely as fishing bait,
poultry food, traditional medicine,… Currently, Dong Thap pharmaceutical
Company has been imported the so called –“land-dragon” from China to produce
the medicine named Doragon. Recent years, in The Mekong Delta, the model of
earthworm feeding has been also spead in many local areas serving for feeding
common tiger prawn, road clawed crayfish, trionychid turtle, goby, loach, etc…
earthworm excrement is also used to fertilize orchards or to make water color in
aquatic ponds.
3.3.2. Some tendencies in research and use of Mekong earthworms
From previous studies and from data collected in this research, there are 4
directions of using earthworms to be suggested: collecting protein to make bait in
aquaculture and poultry feeding (Perionyx excavatus, Lampito mauritii,…),
improving poor land or polluted land and treating waste (various species depending

on specific contexts), isolating some enzymes to make pharmaceutics (Perionyx
excavatus, Lampito mauritii, Ph. posthuma,…), studying earthworm morphology and
anatomy in practical teaching (Ph. posthuma, Ph. sp. 8 and Ph. polychaetifera).
23
CONCLUSIONS AND RECOMMENDATIONS
1. CONCLUSIONS
Basing on the research results, there are some conclusions about earthworm
habitat (regional flora) as follow:
1. About the quantity of species: 34 species of earthworm are recorded,
belonging to 9 genuses of 6 families. Two new scientific species are Ph. thaii and
Ph. mangophila; 1 new species is firstly recorded in Vietnam (Drawida barwelli), 3
new species are the first time recorded in regional flora (Ph. anomala, Ph.
californica and Ph.taprobanae) and 14 taxon are in the process of publishing of
new scientific species where 19/34 earthworm species in Mekong delta were
identified their DNA barcode. The Pheretima genus has 24 species (70.58%) and
has the absolute dominant (with 3 featured groups including posthuma, peguana,
houlleti), the Drawida has 3 species (8.82%), the each other’s (Perionyx,
Pontodrilus, Lampito, Gordiodrilus, Dichogaster, Glyphidrilus, Pontoscolex) has
one species.
2. About biogeoscientific characteristic: the Oriental factor plays the
mainstream role (88.23%), next is Ethiopian with 2 species (5.88%), and New
Tropical and Old North Poles are shared with only one species each (2.94%). The
original distribution zone of the Polypheretima genus expands wider to the south than
the identified boundary by Easton in 1979.
3. About distribution: the average density of earthworm in the Mekong
Delta is 48 units/m
2
and biomass is 35.69 g/m
2
. Diversified level declined from

Vietnam, to ĐBPSVS, HHVB, lowest in BTXS regions but density and biomass in
mountainous terrain is lower than terrains in delta. Each terrain type has its own
characteristic species groups. In dry season, the number of species, density and
biomass lower than in rainy season, in particular in highly natural terrains.
Earthworm in the Mekong Delta is divided into two different species groups:
group 1-year life cycle and the short life span. Habitat distribution characteristics
of earthworm in the Mekong Delta follow the general rule. Diversified degree is
inversely proportional to human work level whereas density and biomass is in
contrast. Each habitat has its own unique species groups (except for a short
24
woodland habitat). Depth distribution of earthworms in the Mekong Delta depends
on many factors such as: season, way of life of the species, depth of topsoil,
4. About issue of use: in the Mekong Delta, wild earthworm is used as bait for
fishing or use as drugs and provides protein. The applied research of earthworm in
the Mekong Delta was conducted in four main directions that are protein resource,
soil improvement, providing pharmaceuticals, and use in teaching.
2. RECOMMENDATIONS
- To complete the basic research of earthworm fauna of Vietnam, there should
be more studies in the South-Eastern provinces of Vietnam and Vietnam’s islands.
- Continue to promote the intensive research in the field of molecular
biology and histological structure of male bud which will be the solid base for
building new classification system for Pheretima group.
25