Distribution and chromosomal variation in the scincid lizard genus <i>Lygosoma</i> (Reptilia: Squamata) in Thailand

doi:10.4236/ns.2013.59121

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Vol.5, No.9, 993-996 (2013) Natural Science

http://dx.doi.org/10.4236/ns.2013.59121

Distribution and chromosomal va riation in the

scincid lizard genus Lygosoma (Reptilia: Squamata)

in Thailand

Varanya Aranyavalai1*, Kanok Lertpanich2, Warawut Chulalaksananukul3

1Department of Biology, Faculty of Science, Chulalongkorn University, Bangkok, Thailand;

*Corresponding Author: [email protected]

2Department of Agricultural Technique, Faculty of Agricultural Development and Resources Management, King Mongkut’s Institute

of Technology Ladkrabang, Bangkok, Thailand

3Department of Botan y, Faculty of Science, Chulalongkorn University, Bangkok, Thailand

Received 15 July 2013; revised 15 August 2013; accepted 22 August 2013

cense, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

ABSTRACT

The distribution of the scincid lizard genus Ly-

gosoma in Thailand was studied and recorded

on a map. In addition, the studies on chromo-

somes of Lygosoma bowringii, L. khoratense

and L. quadrupes were examined. The karyotype

was determined for each individual on the basis

of at least 10 well spread cells. L. bowringii and

L. khoratense showed the same diploid number

of 2N = 32 and identical chromosome morphol-

ogy. The fundamental number (N.F.) equals 48.

The karyotype of L. quadrupes is almost identi-

cal to that of L. bowringii, but differs from the

latter in having a telocentric p air 9. Thus, the N.F.

value equal to 46. No sex chromosome hetero-

morphisms is evident.

Keywords: Di stribution; Chromosome; Skinks;

Lygosoma; Thailand

1. INTRODUCTION

Skinks are a hyper-diverse group of reptiles, contain-

ing more than 1000 species ranging from temperate to

tropical regions on all continents but Antarctica [1,2 ]. Of

these, about 12 genera are recognized in Thailand [3] and

probably some skinks are waiting for description. The

genus Lygosoma described by Hardwicke & Gray, 1827

in family Scincidae has a long and complicated nomen-

clatural history. The common name, writhing skinks, re-

fers to the way these stubby-legged animals move, sn ake-

like but slower and more awkward. The limbs are par-

tially or almost completely reduced (varying from com-

pletely developed four or five digital to hardly noticeable

unidactylous or adactylous limbs). They are truly cos-

mopolitan, distributed in Africa, Australia, South and

Southeast Asia, Polynesia, and Central America. These

skinks are seldom seen on the surface of the soil or leaf

litter. Lygosoma feeds on insects and small invertebrates.

Most species lay eggs, but a few are live-bearers. Very

few record of this genus was subsequently made, and our

knowledge about this secretive skink and its geographi-

cal distribution remains minimal. Currently, most of the

skink’s data are focused on taxonomic status. There are

very few records of biology of skinks, making it difficult

to available in applied works such as concentrating on

captive breeding, and conserving skink species of pure

genetic quality. Cytotaxonomic studies are especially mea-

ger, despite their possible great contributions to the un-

derstanding of the divergence and relationships of the

species. This is due to the paucity of chromosomal data,

especially for the species of Lygosoma. The aim of this

research is to study sp ecies distribution, chromosome nu m-

ber and describe karyotypes of the scincid genus Ly -

gosoma in Thailand. Results revealed the presence of

considerable intraspecific ch romosomal variations within

the genus.

2. MATERIALS AND METHODS

Field surveys were conducted in Thailand, including

Bangkok, Phra Nakhon Si Ayutthaya, Nakhon Nayok,

Chai Nat, Nakhon Sawan , Uttaradit, Phetchab un , Ph ich it,

Kamphaeng Phet, Tak, Sukhothai, Phrae, Lampang, La m-

phun, Nan, Chiang Mai, Mae Hong Son, Chiang Rai,

Saraburi, Nakhon Ratchasima, Burirum, Khon Kaen,

Ubon Ratchathani, Nongkhai, Nakhon Phanom, Suphan-

V. Aranyavalai et al. / Natural Science 5 (201 3) 993-996

994

buri, Kanchanaburi, Chachoengsao, Rayong, Chan th a bu r i ,

Chumphon, Ranong, Suratthani, Nakhon Si Thammarat,

Phatthalung, Songkhla, Phang-nga, Krabi, Phuket, Trang

and Satun provinces. Specimens were collected by p itfall

traps and using the visual encounter survey method. De-

tailed localities of Lygosoma were recorded and plot-

ted in a map. Specimens of Lygosoma bowringii, L.

khoratense, and L. quadrupes were karyotyped in the

laboratory. They were injected intraperitoneally with

0.1 ml of colchicines solution (2 mg/ml) per gram bo-

dy weight, 16 hr before being sacrificed. Metaphase

mitotic cells taken from femur bone marrow were treat-

ed with 0.075 M hypotonic KCL solution for approxi-

mately 30 min, followed by fixation in 1:3 glacial acetic

acid:absolute methyl alcohol. Mitotic chromosome

preparations were made by an air-dry method and stained

in 10% Giema solution for 10 - 15 min. The karyotype

wa s det ermin ed from at least 10 well-spread cells. Termi-

nology for chromosomal description follows Green and

Sessions [4]. The experimental protocol was approved by

the Animal Care and Use Committee of Faculty of Sci-

ence, Chulalongkorn University (Protocol Review No.

0923003).

3. RESULTS

3.1. Distribution

Three species of skinks in genus Lygosoma, including

L. quadrupes, L. bowringii, and L. khoratense were found

at 28 locations during the field surveys. Localities of

them were shown in Figure 1 and Table 1.

3.2. Description of Species

Lygosoma quadrupes

A slender and very elongate skink with four very short

limbs but still has five digits. The ear-opening is very

small, narrow and partly covered with scales. The lower

eyelid is nearly yellow-white, movable and covered by

two rows of small scales. There is a single frontoparietal

and nasal but the postnasal is absent. The rostral is little

wider than high, while the frontonasal is broader than

long, forming suture with rostral, frontal, and anterior

loreal. The anterior loreal is higher but narrower than the

second loreal. The prefrontals are small and widely sepa-

rated. The frontal is little longer th an its d istan ce from tip

of snout, about as long as single frontoparietal, but smaller.

The interparietal is little smaller than frontal and en-

closed by parietals. There are 24 to 26 scalerows around

middle of body. The color is gray-brown to brown with

dark longitudinal lines, usually visible on edges of all

scalerows, continued onto tailed. The top of head is dar ker

than the body (Figures 2(a) and (b)).

Figure 1. Distribution of Lygosoma quadrupes, L. bowringii,

and L. khoratense in Thailand.

Figure 2. Lygosoma quadrupes (a) from Kanchanaburi Prov-

ince; (b) from Chai Nat Province.

Lygosoma bowringii

A little skin k with short limbs and cannot to uch unless

the body is flexed. The small supranasal scales are pre-

V. Aranyavalai et al. / Natural Science 5 (201 3) 993-996

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Table 1. Locations of skinks in genus Lygosoma observed in the field surveys.

Species No. Province Location

Lygosoma quadrupes

Bangkok

Chai Nat

Chanthaburi

Suphanburi

Kanchanaburi

Pramongkutklao H o s p i t a l a n d C o l l e ge of Medicine

King Mongkut's Institute of Technology Ladkrabang

Amphoe Mueang

Amphoe Kaeng Hang Maeo

Amphoe Song Phi Nong

Amphoe Thong Pha Phum

Lygosoma bowringii

Phra Nakhon Si Ayutthaya

Nakhon Nayok

Uttaradit

Tak

Nan

Chiang Mai

Kanchanaburi

Chachoengsao

Chanthaburi

Saraburi

Nakhon Ratchasima

Ubon Ratchathani

Chumphon

Ranong

Phang-nga

Trang

Satun

Amphoe Mueang

Wangtakrai, Amphoe Mueang

Amphoe Laplae

Amphoe Sam Ng a o

Amphoe Wiang Sa

Amphoe Fang

Amphoe Thong Pha Phum

Amphoe Sanam Chai Khet

Amphoe Tha Takiap

Amphoe Kaeng Hang Maeo

Amphoe Khlung

Amphoe Laem Sing

Amphoe Soi Dao

Amphoe Kaeng Khoi

Amphoe Sikhio

Amphoe Khong Chiam

Amphoe Phato

Amphoe Kapoe

Amphoe Ko Yao

Amphoe Na Yong

Amphoe La-ngu

Lygosoma khoratense 28 Nakhon Ratchasima Amphoe Sikhio

sent and the tympanum is deep ly sunk below th e external

ear opening. The frontonasal is large, laterally touching

the first loreal. The prefrontals are widely separated and

the suture between frontal and frontonasal is nearly a

straight line. The length of frontal is greater than its dis-

tance from tip of snout but less than length of combined

parietals and frontoparietals. The frontoparietal is divided

and the interparietal is enclosed by parietals. There are

two loreals, anterior higher and narrower than the seco nd.

It has smooth or faintly keeled scales, a scaled lower

eye li d , a n d a di s ti n ct iv e dark flank band with white s po t s ,

red behind the arm and yellow bellow. There are 30 sca-

lerows around neck and 31 scalerows around middle of

body. The ventral scales are larger than the laterals but

smaller than the dorsals (Figures 3 (a) and (b)).

Figure 3. Lygo som a bowringii (a) from Satun Province; (b)

from Chanthaburi Province.

are 28 scalerows around neck and 32 to 34 scalerows

around middle of body. The short thick tail suddenly ta-

pers at the tip. The dorsum is brownish, each scale with a

dark brown edge and a vague dark spot at its base. The

flanks are lighter than the dorsum while the venter is pale

grey, and the subcaudals are darker. The scales of head

are slightly darker edges. It is found only in Thailand.

Lygosoma khoratense

An elongate skink with small widely separated penta-

dactyl limbs. The rostral is wider than high and part visi-

ble above considerably is longer than suture between

supranasals. The latter scales are fused to the nasals ante-

riorly. The frontonasal is about twice as broad as long

touching the first loreal. The prefrontals are small and

widely separated, leaving a broad suture between frontal

and frontonasal. The first lo real is higher and shorter than

the second. The frontoparietal are paired. The interparie-

tal is small, enclosed behind by parietals. The ear-open-

ing is very small with small lobules proj ecting from ante-

rior border. Snout scales are somewhat thickened. There

3.3. Chromosome Numbers and Karyotypes

Karyotypes of Lygosoma bowringii and L. khoratense

seem to be identical with each other when treated with

Giemsa: both species have 2N = 32 chromosomes form-

ing three size groups (Figures 4(a) and (b)). Of these,

pairs 1 to 4, composing the largest group, are metacentric

macrochromosomes. There is a size discontinuity between

pairs 4 and 5. The second size group consists of four pair

metacentric chromosomes (pairs 5, 6, 7, and 9), gradu-

ally reducing in size. Of the remainder composing the

smaller size, pair 8 is submetacentric, whereas the smallest

OPEN ACCESS

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996

Figure 4. Karyotypes of (a) Lygosoma bowringii (male) from

Chanthaburi Province, and (b) Lygosoma khoratense (male)

from Nakhon Ratchasima Province. Bar equals 10 µm.

pair appears to be telocentric. The fundamental number

(N.F.) is calculated as 48. The karyotype of L. quadrupes

(Figure 5) is almost identical to that of L. bowringii and

L. khora t ens e , but differs from the latter in having a te-

locentric pair 9. Thus, the N.F. value equals 46. In addi-

tion, in these three Ly gosoma species, secondary con-

strictions are evident on the shorter arms of pair 1 or the

longer arms of pair 2 or both. No sex chromosome het-

eromorphisms are evident.

4. DISCUSSION

During our field surveys, three species of skinks in

genus Ly gosoma were found. The microhabitats of them

are cryptozoic and partially fossorial and are found under

dead tree trunks, in dead wood and in loose, humid soil

where they glid e with agility. L. bowringii, L. khoratense

and L. quadrupes hitherto examined have karyotypes

sharing many similarities with each other such as the

diploid chromosome number (32), large metacentricity in

pairs 1 to 4 and the distinct size-gap between pairs 4 and

5. So, these populations seem to be lacking in chromo-

some changes that could act as reproductive barriers.

However, because speciation in lizards is not always as-

sociated with chromosome repatterning (see [5] for re-

view), and considering that the 2N = 32 karyotype is

plesiomorphic for skinks [6], the lack of karyotypic dif-

ferentiation does not necessarily indicate that the “L.

bowringii” and “L. khora ten se ” fo r ms b e lon g to th e s ame

biological species. Therefore, further C-banding studies

are needed for the inference of its derivation process. In

addition, future detailed an alyses inv olving karyotypes of

the remaining species in genus Ly gosoma are needed to

test in order to clarify intraspecific chromosomal varia-

tions within this genus.

Figure 5. Karyotype of Lygosoma quadrupes (male) from

Chainat Province. Bar equals 10 µm.

5. CONCLUSION

This study reported the distribution of the scincid liz-

ard genus Lygosoma in Thailand. Comparison on chro-

mosomes of Ly gosoma bowringii and L. khoratense

showed the same diploid number of 2N = 32 and identi-

cal chromosome morphology. The karyotype of L. quad-

rupes is almost identical to that of L. bowringii, but dif-

fers from the latter in having a telocentric pair 9. There is

no evidence of heteromorphic sex chromosomes.

6. ACKNOWLEDGEMENTS

This research was supported by the TRF/BIOTEC Special Program

for Biodiversity Research and Training Grant (Grant no. MRG 5080366).

Varanya is also indebted to Dr. Ratchata Phochayavanich, Mr. Chat-

traphas Pongchareon, and Mr. Kasem Theingtham for helping with

field sampling.

REFERENCES

[1] Matsui, M. (1992) Systematic zoology, Vol. 9, vertebrates

IIb2, Reptilia II. Nakayama-Shoten, T ok yo.

[2] Zug, G.R., Vitt, L.J. and Caldwell, J.P. (2001) Herpetol-

ogy. Academic Press, London.

[3] Nabhitabhata, J., Chanard, T. and Chuaynkern, Y. (2000)

Checklist of amphibians and reptiles in Thailand. Office

of Environmental Policy and Planning Bangkok, 80-92.

[4] Green, D.M. and Sessions, S.K. (1991) Nomenclature for

chromosomes. In: Green, D.M. and Sessions, S.K., Eds.,

Amphibian Cytogenetics and Evolution, Academic Press,

San Diego, 431-432.

[5] King, M. (1981) Chromosome change and speciation in

lizards. In: Atchley, W.R. and Woodruff, D.S., Eds., Evo-

lution and Speciation, Cambridge University Press, Ca m-

bridge, 262-285.

[6] Caputo, V., Odierna, G. and Aprea, G. (1994) A chromo-

somal study of Eumeces and Scincus, primitive members

of the Scincidae (Reptilia, Squamata). Bolletino di Zo-

ologia, 61, 155-162. doi:10.1080/11250009409355876