Corresponding author: Anh D. Nguyen (
Academic editor: Samuel James
The megascolecid earthworms of the Phu Quoc island are intensively investigated. Twelve species in three genera (
Nguyen TT, Lam DH, Trinh BTK, Nguyen AD (2020) The megascolecid earthworms (Annelida, Oligochaeta, Megascolecidae) in the Phu Quoc island, Vietnam, with descriptions of three new species. ZooKeys 932: 1–25.
Phu Quoc, located in the southernmost part of Vietnam, is the largest island in the country, with an area of 58,923 ha. It is covered largely by typically tropical forests. The earthworms of the Phu Quoc are poorly known with only seven species reported from the island. These include
To improve the knowledge of the earthworms of Vietnam, this study documents the diversity of the family
Earthworms were collected manually in 34 sites in three habitats: natural forests, industrial plantations of
Collecting sites in the Phu Quoc island.
Transverse body sections were processed using the classical method of haematoxylin and eosin. Selected segments were cleaned and dehydrated using graded ethanol concentrations. Segments were treated with paraffin, then cut using a Sakura Accu SRM 200CW microstome. The cut sections were stained using haematoxylin and eosin Y (
Material was examined under a Motic Digital microscope (model DM143-FBGG-C), and dissected from the dorsal side for internal observation. Colour images were taken using a camera attached directly to the microscope. Line drawings and colour images were improved and grouped into finished figures using Photoshop CS6.
All specimens including holotypes and paratypes are housed in the Laboratory of Zoology, Can Tho University. Some are shared with the laboratory of Department of Applied Biology, Kien Giang University.
1 mature (
Medium-sized. Prostomium epilobous. Clitellum within xiv–xvii. Three pairs of spermathecal pores in ventral intersegments 6/7/8/9. No genital markings. Male pores in xviii with penis seta. Spermathecae with two diverticula. Holandric. Intestinal caeca absent. Septa 4/5/6 absent. Oesophageal gizzard within v–vi.
The species is widely distributed in sandy soils in coastal areas of Vietnam (
Giun lampito mauriti.
22 matures (
Medium-sized. Prostomium 2/3 epilobous. First dorsal pore in 12/13. Three pairs of spermathecal pores in lateroventral intersegments 6/7/8/9. Male pores located inside copulatory pouches in xviii. Male region strongly concave to form an ellipsoid or rounded area. Genital markings absent in the spermathecal region, but two pairs present in 17/18 and 18/19, in line with male pores. Intestinal caeca simple. Holandric. Testis sacs separated. Septa 8/9/10 absent.
This species was collected from leaf litter and upper soil layer (0–10 cm).
Giun bahl.
21 matures (
Medium-sized. Prostomium epilobous. First dorsal pore in 12/13. Two pairs of spermathecal pores in lateroventral intersegments 7/8/9. Male pores located inside copulatory pouches in xviii. Genital markings absent in both spermathecal and male regions. Intestinal caeca simple. Holandric. Testis sacs connected. Septa 8/9/10 absent.
The species was found in the residential gardens and natural forests. They live in leaf litter and humid rocks.
Giun
7 matures (
Body cylindrical, medium-sized, length 168–220 mm, diameter 6.50–7.58 mm, segments 99–133, weight 5.5–13.2 g. Body greyish brown, ventrum paler than dorsum, clitellum darkish brown. Prostomium 3/4 epilobous. First dorsal pore in 12/13. Pre-clitellum setae stouter and sparser than post-clitellum setae; setal number: 65–77 in viii, 94–97 in xxx, 4–10 between two male porophores in xviii; setal distance: aa > ab, zz > zy. Clitellum within xiv–xvi, without setae and dorsal pores. Female pore single, in mid-ventral xiv.
Three pairs of spermathecal pores in lateroventral intersegments 6/7/8/9. Four pairs of pad-shaped genital markings in vi–ix, in line with spermathecal pores.
Male pores located inside copulatory pouches in xviii. Ventral distance between two openings of copulatory pouches about 0.3× body circumference. Two pairs of dish-shaped genital markings present in 17/18 and 18/19, in line with the openings of copulatory pouches.
Septa 5/6/7/8 thick, 8/9/10/11 absent, 11/12/13 thick. Oesophageal gizzard within viii–xi. Intestinal origin at xv. Intestinal caeca within xxvii–xxix, ventrally lobuled. Last hearts in xiii. Pharyngeal micronephridia grouped in 5/6/7. Typhlosole lamelliform. Lymph glands lobuled, from 16/17.
Spermathecae paired in vi–ix. Ampulla large, oval-shaped; ducts as long as 1/3 ampulla. Diverticula strongly coiled, attached to the middle of ampulla duct; seminal chamber oval. No accessory glands.
Holandric. Testis sacs in xi, separated. Seminal vesicles well developed in xi and xii. Ovaries in 12/13; ovisacs inviable. Prostate glands deeply lobuled in xvi–xxi; ducts spherical, enlarged basally. Two pairs of large accessory glands present.
The species was found in all habitats, but more in residential gardens. They live in clay soils in the depth of 15–30 cm.
Of all specimens, five differ in that their copulatory pouches are deeply concave inside the body wall (Fig.
10 matures (
Medium-sized. Prostomium epilobous. First dorsal pore in 11/12. Three pairs of spermathecal pores in lateroventral intersegments 6/7/8/9. Male pores located inside copulatory pouches in xviii. Two to four penial setae. Intestinal caeca simple. No genital markings. Holandric. Testis sacs connected. Septa 8/9/10 absent.
The species was found mainly in industrial tree plantations and residential gardens. It was collected in leaf litter and sometimes in upper soil surface (0–10 cm).
The specimens collected in Phu Quoc island have the seta a on segments iii–v being bigger than that on other segments.
Giun houllet.
15 matures (
Medium-sized. Prostomium epilobous. First dorsal pore in 12/13. Three pairs of spermathecal pores in lateroventral intersegments 6/7/8/9. Male pores located inside copulatory pouches in xviii. Male region not concave. Genital markings absent in the spermathecal region, but two pairs disc-shaped in 17/18 and 18/19, in line with the openings of copulatory pouches. Intestinal caeca simple. Holandric. Testis sacs separated. Septa 8/9/10 absent.
The species was found only in the upper soil surface of natural forests.
Of 20 specimens, six have intestinal caeca which are slightly lobuled ventrally.
Giun pegu.
10 matures (
Medium-sized. Prostomium epilobous. First dorsal pore in 11/12. Two pairs of spermathecal pores in lateral intersegments 6/7/8. Male pores located inside copulatory pouches in xviii. Genital markings absent in the male region, but 1–3 located near each spermathecal pore. Intestinal caeca simple. Holandric. Testis sacs separated. Accessory glands present, sac-shaped. Septa 8/9/10 absent.
The species was commonly found in residential gardens and industrial tree plantations. They live in leaf litter and upper soil layer.
Giun plana.
The species has been commonly found in southern Vietnam. However, it was erroneously identified as
3 matures (
Medium-sized. Prostomium epilobous. First dorsal pore in 12/13. Four pairs of spermathecal pores in lateroventral intersegments 5/6/7/8/9. Male pores located inside shallow copulatory pouches in xviii. Two pairs of genital markings present in xvii and xix. Intestinal caeca simple. Holandric. Testis sacs connected. Septum 8/9 thick, 9/10 absent.
The species was only found in the residential gardens.
Giun quắn.
The species is commonly distributed in southern Vietnam, but rarely found in Phu Quoc island.
1 mature (
Small to medium-sized. Prostomium epilobous. First dorsal pore in 12/13. Three pairs of spermathecal pores in dorsal intersegments 6/7/8/9. Male pores located inside copulatory pouches in xviii. No genital markings. Penial setae present. Intestinal caeca simple. Holandric. Testis sacs connected in xi. Septa 8/9/10 absent.
Body cylindrical, small to medium-sized, length 81–118 mm, diameter 3.3–3.7 mm, segments 106–142, weight 0.5–0.8 g. Body uniformly whitish grey, clitellum darkish brown. Prostomium 1/2 epilobous. First dorsal pore in 12/13. Pre-clitellum setae stouter and sparser than post-clitellum setae; setal numbers: 44–47 in viii, 54–58 in xxx, 7–8 between two openings of copulatory pouches; setal distance aa > ab, zz ≥ zy. Clitellum within xiv–xvi, slightly flattened ventrally, without setae and dorsal pores. Female pore single, in mid-ventral xiv.
Three pairs of spermathecal pores in dorsal intersegments 6/7/8/9, located near dorsal line. Genital markings absent in the spermathecal region. Male pores located inside copulatory pouches in xviii; ventral distance between two openings of copulatory pouches about 0.3× body circumference. No genital markings in the male region.
Septa 5/6/7/8 thick, 8/9/10/11 absent, 11/12/13 thin. Oesophageal gizzard within viii–xi. Intestinal origin at xv. Intestinal caeca simple, within xxvii–xxv. Last hearts in xiii. Typhlosole lamelliform. Lymph glands lobuled, from 17/18.
Three pairs of spermathecae in vii–ix. Ampulla clavate; ducts long. Diverticula thin, waved, shorter than ampulla, attached to the base of ampulla; seminal chamber ellipsoid. No accessory glands.
Holandric. Testis sacs in xi, connected. Seminal vesicles xi and xii well developed. Ovaries in 12/13. Ovisacs invisible. Prostate glands racemose, within xvii–xxii; ducts spherical, enlarged basally, ending at bell-shaped copulatory pouches. Each copulatory pouch with a penial seta. Two pairs of accessory glands attached to copulatory pouches.
The species was collected in the depth of 0–10 cm of sandy soils in bushes and residential gardens.
Giun buồng giao phối hình chuông.
Compared to the original description of
Small to medium-sized, length 51–54 mm, diameter 2.2–2.5 mm, segments 85–89. Prostomium epilobous. Four pairs of spermathecal pores in lateroventral intersegments 5/6/7/8/9. Male pores in xviii, without copulatory pouches. Genital markings arranged in two transverse line in front of and behind the setal ring xviii. Intestinal caeca simple. Holandric. Testis sacs in xi and xii, separated. Septa 8/9/10 absent.
“
Body cylindrical, small to medium-sized, length 51–54 mm, diameter 2.2–2.5 mm, segments 85–89, weight 1.2–1.4 g. Body uniformly whitish grey, clitellum darkish brown. Prostomium 1/2 epilobous. First dorsal pore in 5/6. Pre-clitellum setae stouter and sparser than post-clitellum setae; setal numbers: 47–54 in viii, 46–48 in xxx, no setae between two male porophores; setal distance: aa > ab, zz > zy. Clitellum within xiv–xvi, slightly flattened ventrally, without setae and dorsal pores. Female pore single, in mid-ventral xiv.
Four pairs of spermathecal pores in lateroventral intersegments 5/6/7/8/9. No genital markings in the spermathecal region.
Male porophores small in xviii, without copulatory pouches; ventral distance between two male pores about 0.25–0.28× body circumference. About 8–12 small genital markings ventrally arranged in two transverse lines in front of and behind the setal ring xviii.
Septa 5/6/7/8 thick, 8/9/10 absent, 10/11/12 thick. Oesophageal gizzard within viii–x. Intestinal origin at xv. Intestinal caeca simple, within xxvii–xxvi. Last hearts in xiii. Pharyngeal micronephridia in 5/6/7. Typhlosole lamelliform. Lymph glands absent.
Spermathecae paired in vi–ix. Ampulla clavate; ducts not clearly distinct from ampulla. Diverticula slightly waved, attached to the base of ampulla; seminal chamber small, chained-shaped with 2 or 3 parts. No accessory glands.
Holandric. Testis sacs in x and xi, connected. Seminal vesicles well developed in xi and xii. Ovaries in 12/13. Ovisacs invisible. Prostate glands deeply lobuled within xvi–xx; ducts U-shaped. No accessory glands.
The species was only collected under leaf litter in
Giun buồng tinh hình chuỗi.
The new species can be assigned to the
Compared to
Within the
Character comparison between
Characteristics |
|
|
|
---|---|---|---|
Length | 51–54 | 220–350 | 121–126 |
Diameter | 2.2–2.5 | 7–12 | 3–6 |
Segments | 85–89 | 123–186 | 108–112 |
First dorsal pore | 5/6 | 12/13 | 12/13 |
GM in spermathecal region | absent | numerous, vii–viii | numerous, vi–ix |
GM in male region | 8–10, two lines, pre- and post-setal in xviii | 4–10, grouped around male pores in xviii | 5–20, grouped around male pores in xviii |
Septum 8/9 | absent | thin | absent |
Intestinal caeca | simple | lobuled | simple |
Testis sacs | connected | separated | connected |
Shape of ampulla | clavate | oval | oval |
Seminal chamber | chained | twisted | chained |
Source: 1 =
Medium-sized, length 74–145 mm, average diameter 2.5–4.7 mm, segments 116–145. Prostomium epilobous. Two pairs of spermathecal pores in ventral intersegments 7/8/9. Male pores in xviii, without copulatory pouches. Two pairs of genital markings present in ventral 17/18 and 18/19. Intestinal caeca simple. Holandric. Testis sacs in xi, separated. Septa 8/9/10/11 absent.
“
Body cylindrical, medium size, length 74–145 mm, average diameter 2.5–4.7 mm, segments 116–145, weight 0.6–3.7 g. Body uniformly greyish brown except darkish brown clitellum. Prostomium 2/3 epilobous. First dorsal pore in 12/13. Pre-clitellum setae stouter and sparser than post-clitellum ones; setal numbers: 42–61 in viii, 50–77 in xxx, 5–9 between male porophores in xviii; setal distance: aa > ab, zz > zy. Clitellum within xiv–xvi, without setae and dorsal pores. Female pore single, in mid-ventral xiv.
Two pairs of spermathecal pores in ventral intersegments 7/8/9. Genital markings absent in the spermathecal region. Male pores located in the setal ring xviii, without copulatory pouches; ventral distance between two male pores about 0.28× body circumference. Genital markings roundly pad-shaped and variable in the male region, normally with two pairs in 17/18 and 18/19, or a pair in xix (near 19/20).
Septa 5/6/7/8 thick, 8/9/10/11 absent, 11/12/13 thick. Oesophageal gizzard within viii–xi. Intestinal origin at xv. Intestinal caeca simple, within xxvii–xxiv. Last hearts in xiii. Pharyngeal micronephridia in 5/6/7. Typhlosole lamelliform. Lymph lobuled, from 15/16.
Two pairs of spermathecae in viii and ix. Ampulla large, heart-shaped with transverse wrinkles; ducts short and stout. Diverticula waved, attached to the base of ampulla; seminal chamber ellipsoid. Accessory glands bean-shaped, surrounding spermathecal ducts.
Holandric. Testis sacs in xi, separated, the anterior pair poorly developed. Seminal vesicles well developed in xi and xii. Ovaries in 12/13. Ovisacs invisible. Prostate glands deeply lobuled in xvi–xx; ducts strongly coiled. Accessory glands present.
The species was occasionally found in natural forests along the main road to the northern part of Phu Quoc island. They were collected in the upper soil layer (0–10cm).
Giun phú quốc.
The body size and number of genital markings in the male region are variable among collected specimens. Specimens can be divided into two groups based on body size. The group of smaller specimens (
Genital markings are also variable in the male region. Genital markings have two pairs located in 17/18 and 18/19 (Type 1), but reduced to three genital markings (Type 2), one pair either in xvii or in xiv (Type 3 or Type 4), or a single one in xix (Type 5) (Fig.
The new species can be assigned into the
Within the
Regarding the arrangement of genital markings in the male region, the new species is slightly similar to
Variation of genital markings in the male region of
Character comparison between
Characters |
|
|
|
---|---|---|---|
Length (mm) | 118–145 | 76–100 | 88–122 |
Diameter (mm) | 3.7–4.7 | 2.2–4.8 | 3.0–4.1 |
Segments | 143–145 | 99–104 | 82–109 |
Spermathecal pores | lateroventral | lateroventral | ventral |
First dorsal pore | 12/13 | 5/6 | 5/6 |
GM in male region | 17/18 and 18/19 or xvii or xix | 17/18 and 18/19 | 17/18 and xix |
Septum 10/11 | absent | present | present |
Testis sacs | separated in xi | connected, x and xi | connected, x and xi |
Accessory glands in spermathecal region | surrounding spermathecal ducts | no | no |
Accessory glands in male region | present | absent | present |
Source: *:
Character comparison between
Characters |
|
|
|
---|---|---|---|
Length (mm) | 168–220 | 72 | 38–45 |
Diameter (mm) | 6.50–7.58 | 3–4 | 2–3 |
Segments | 99–133 | 100 | 40–51 |
Spermathecal pores | 6/7/8/9, lateroventral | 5/6/7/8, dorsal | 6/7/8, lateral |
First dorsal pore | 12/13 | 12/13 | 4/5 |
GM in spermathecal region | 4 pairs in vi–ix | absent | absent |
Septum 10/11 | absent | present | present |
Intestinal caeca | lobuled | simple | manicate |
Male sexual system | holandric | holandric | holandric |
Testis sacs | xi, separated | x, xi, separated | x, xi, connected |
Source: 1:
Medium-sized, length 139–170 mm, diameter 4.4–5.8 mm, segments 149–151. Prostomium epilobous. First dorsal pore in 12/13. Two pairs of spermathecal pores in ventral intersegments 7/8/9. Male pores located behind the setal ring xviii, on the posterior edge of genital markings. Two pairs of genital markings present in xvii and xviii. Intestinal caeca simple. Holandric. Testis sacs in xi, separated. Septa 8/9/10/11 absent.
“
Body cylindrical, medium-sized, length 139–170 mm, diameter 4.4–5.8 mm, segments 149–151, weight 1.4–2.2 g. Body uniformly greyish brown except darkish brown clitellum. Prostomium 1/2 epilobous. First dorsal pore in 12/13. Pre-clitellum setae stouter and sparser than post-clitellum ones; setal numbers: 56–59 in viii, 84–85 in xxx, 17–20 between two male porophores in xviii; setal distance: aa = ab, zz = zy. Clitellum xiv–xvi, without setae and dorsal pores. Female pore single, in mid-ventral xiv.
Two pairs of spermathecal pores in intersegments 7/8/9. Male pores behind the setal ring xviii, on the posterior edge of genital markings, without copulatory pouches; ventral distance between two male pores about 0.33× circumference. Two pairs of genital markings present in xvii and xviii, slightly concave inside body wall.
Septa 5/6/7/8 thick, 8/9/10/11 absent, 11/12/13 thin. Oesophageal gizzard within viii–xi. Intestinal origin at xv. Intestinal caeca simple, within xxii–xxvii. Last hearts in xiii. Pharyngeal micronephridia in 5/6/7. Typhlosole lamelliform. Lymph glands lobuled, from 15/16.
Two pairs of spermathecae in viii and ix. Ampulla clavate, sometimes constricted; ducts short. Diverticula shorter than ampulla, folded several times, attached to the base of ampulla; seminal chamber oval. Each spermatheca with a bean-shaped accessory gland.
Holandric. Testis sacs in xi, separated. Seminal vesicles well developed in xi and xii. Ovaries in 12/13. Ovisacs invisible. Prostatic glands deeply lobuled in xvi–xxi; ducts long. Two pairs of accessory glands present.
The species was found only in natural forests in northern part of Phu Quoc island. It was collected in the upper soil layer (0–10 cm) of clay soils.
Giun nhú phụ chứa lỗ đực.
The new species can be assigned to the
Character comparison between
Characters |
|
|
|
---|---|---|---|
Length (mm) | 139–170 | 78–100 | 63–77 |
Diameter (mm) | 4.4–5.8 | 4.5–6.0 | 3.0–4.0 |
Segments | 149–151 | 121–136 | 78–101 |
First dorsal pore | 12/13 | 12/13 | 4/5 or 5/6 |
Male pores | behind the setal ring xviii, on the posterior edge of genital marking | on the setal ring xviii | on the setal ring xviii |
Ventral distance between two male pores | 0.35 | 0.24–0.27 | 0.19–0.25 |
Genital markings in the male region | xvii, xviii | xviii, xix | xvii, xviii, xix |
Septum 8/9 | absent | thin | absent |
Septum 10/11 | absent | present | present |
Testis sacs | xi | x, xi | x, xi |
Intestinal origin | xv | xvi | xv |
Accessory glands in spermathecal region | present | absent | absent |
Accessory glands in male region | present | ? | absent |
Source: *:
1 | Clitellum xiv–xvii; each spermatheca with two diverticula |
|
– | Clitellum xiv–xvi; each spermatheca with a diverticulum |
|
2 | Copulatory pouches absent |
|
– | Copulatory pouches present |
|
3 | Four pairs of spermathecal pores in 5/6/7/8/9. First dorsal pore in 5/6 |
|
– | Two pairs of spermathecal pores in 7/8/9. First dorsal pore in 12/13 |
|
4 | Male pores located behind the setal ring xviii. Genital markings strongly concave inside body wall in the male region |
|
– | Male pores in the setal ring xviii. Genital markings not concave |
|
5 | Genital markings present in the male region |
|
– | Genital markings absent in the male region |
|
6 | Four pairs of spermathecal pores in 5/6/7/8/9. Two pairs of genital markings in xvii and xix. Septum 8/9 thick |
|
– | Three pairs of spermathecal pores in 6/7/8/9. Two pairs of genital markings in 17/18 and 18/19. Septum 8/9 absent |
|
7 | Three to four pairs of genital markings in vi–ix. Septum 10/11 absent |
|
– | No genital markings in the spermathecal region. Septum 10/11 present |
|
8 | Genital markings disc-shaped. Male region not concave |
|
– | Genital markings slide-shaped. Male region concave |
|
9 | Two pairs of spermathecal pores in 6/7/8 or 7/8/9 |
|
– | Three pairs of genital markings in 6/7/8/9 |
|
10 | Spermathecal pores in 6/7/8. First dorsal pore in 11/12 |
|
– | Spermathecal pores in 7/8/9. First dorsal pore in 12/13 |
|
11 | Spermathecal pores located dorsally. First dorsal pore in 12/13 |
|
– | Spermathecal pores located lateroventrally. First dorsal pore in 11/12 |
|
As Phu Quoc island has a large area, the 12 species recorded at present may not reflect the true biodiversity of earthworms in this island. More intensive surveys likely will reveal additional new species and result in better understanding of the earthworm biodiversity of Vietnam.
This study is funded in part by the Can Tho University Improvement Project VN14-P6, supported by a Japanese ODA loan.