Asiatic Herpetological Research

1999

Vol. 8, pp. 25-28

Size and Shape Description of Oviductal Eggs of Draco obscurus formosus(Squamata: Agamidae)
C.H. Diong

1and S.Y.T. Soon 2

Division of Biology, School of Science, Nanyang Technological University, N1E, 469 Bukit Timah Road,Singapore 259756; -Interactive Math Exploration Center, 02-16, Waterloo Center, Singapore 180261.

Abstract.-Owidactai eggs were obtained by an abdominal dissection from a gravid Draco obscurus formosus

which was captured near the northern
Scientific Expedition toBelum, Temengor Forest Reserve, Ulu Perak, Peninsular Malaysia in 1993 and 1994.

Egg size, shape, the species-specific egg bicone coefficient
isMalaysian Heritage andlimits of this species distribution during the,clutch mass, and clutch volume are described. This

the first report that describes the egg and clutch characters of this species.

Key words,Reptilia, Squamata, Agamidae, Draco obscurus formosus. Peninsular Malaysia, egg shape, biconecoefficent.

Figure 1 A. The adult female Draco obscurus formosus.

(ZRC.2.3693) from Sungei Halong, Temengor Rain Forest, Ulu Perak, Peninsular Malaysia. SVL = 87 mm. B.

A clutch of four fully-shelled oviductal eggs of Draco
obscurus formosus. Note the pinched projections at
both ends of each egg.
shelled eggs. Length and width dimensions of such

eggs change as they absorb or lose water through thesoft parchment shell to produce changes in their size,

shape, volume, and surface area. Consequently, softshelled eggs have to be measured in their oviducts orsoon after they are oviposited. This is in contrast to
rigid-shelled eggs of crocodilians, geckos, birds, andIntroductionsome chelonians which can be measured at any timeSize and shape characteristics of eggs, as well as theafter being laid.

ecological implications of egg parameters, have been

Iverson and Ewert 1991 applied Preston's (1968)
formulation to describe reptile eggs firstly. This for-extensively studied in birds (e.g.. Preston, 1968, 1969.

1974: Paganelli et al., 1974; Hoyt, 1979; Smart, 1991)
but rare in reptiles (IversonEwert, 1991; Maritz&()

mulation was developed to describe the shape of avianand Douglas. 1994). One reason for this neglect lies ineggs and assumed that an egg was axis-symmetric andthe revolved egg outline on the x-axis gives its volume

the fact that most squamate reptiles lay soft, flexible-of revolution. Recently, Maritz and Douglas (1994)

Vol. 8, p.2t

1999

Asiatic Hei-petological Researchy valuebFigure 2. The coordinates and linear dimensions used to describe the shape of Draco obscurus formosus eggs;
the outline of the egg shape, excluding the pinched ends, is generated by Mathematica software program. See
text for details.

employed the Preston formulation to demonstrate theshape of reptile eggs from two linear measurements,
egg length L, maximum width W, and the bicone coefficient c 2.

The bicone coefficient is a species-specificparameter which measures bluntness at both ends ofan egg: c 2 is negative for eggs with pointed ends, positivefor eggs with blunt ends,

and zero when theDuring the Malaysian Heritage and Science Expedition to the Belum Temengor Forest Reserves in 1993

and 1994, a gravid female of Draco o. formosus, asubspecies endemic to southern Peninsular Thailand
1903,1908;

Musters, 1983) was collected (Diong et al. 1995).
This presented an opportunity to collect oviductal

eggs for size and shape quantization for this subspecies.

Material examined

One gravid female (Fig. la) was collected on 9 Dec
1994 from a trunk of a large tree along Sungei [river]
Halong, about 224X

km upstream of Camp Halong (5°101° 18Ti), Temengor Rain Forest Reserve, Ulu

Perak, Malaysia, during the Belum Scientific Expedi-shape is a perfect ellipse.

and Peninsular Malaysia (Boulenger,Material and Methods

tion (Diong et. al. 1995). Specimen was measured anddissected the day after collection. Head and bodyshape, as well as mass of body and egg were mea-

sured to the nearest 0.01
ipers(Mitutoyo)mm and 0.01 g by digital cal-and electronic

respectively. Voucher specimenbalance(Ohaus),

was deposited in theZoological Reference Collection, School of Biological Sciences, National University of Singapore.

Quantization of egg shape
Length (L) and maximum width (W) of each egg were
measured to obtain elongation (E = LAV), bicone
coefficient (c 2 ) and volume (V) using the method
described by Maritz and Douglas ( 1994). The outline

Asiatic Herpetological Research

1999

of the egg was described parametrieally using the Preston formulation, as follows

1(£)-.e<0° <asymmetric. Mean ± SD of L excluding pinched ends
- 12.30
for 4 eggs 11.83 ± 0.53(range: 10.94mm:mm); L including pinched ends 13.00 ± 0.26 mm(range: 12.14- 13.40 mm); W 8.71 ± 0.20 mm (range:8.40 - 8.91 mm); elongation L/W 1.36 ± 0.08 (range:1.23 -1.41); mean egg bicone coefficient c 2 -0.021 ±cos(8).

-+ c2 cos 0),0.008 (range: -0.032 to - 0.010); egg volume 0.487 ±0.022 cm< 360°30.510); egg mass 0.497 ±0.022 g (range: 0.4700.520 g); density 1.0205 ±0.0009 (range: 1.0 196 - 1.0217). Total clutch volume(range: 0.460--

Mathematica (1993) software programme wasused to generate the shape described by the paramet-

1.86

A 35 mm slide of the clutch of eggs was

mass

ric equations.

Vol. 8. p. 27

cm;

total

clutchmass

1.99 g; relative clutch

mass divided by female[clutch(clutch plus

mass
mass
dividedfemaleexclusive[clutchby(body only,in percent,19.86; relative clutch

projected on to a white cardboard mounted on a wallbody) mass]and three lines parallel to the y axis (c.a. 2/3 W) weredrawn to the outline of each egg (Fig. 2) to obtainof clutch) mass) in percent, 24.78

W from the projected

measurements of 1, w, L, andDiscussion

image;
procedure was repeated for the other halfof the egg so that the bicone for each egg was an average of six estimations. The bicone coefficient was

The present specimen has TL/SVL ratio equaled todetermined with the formula, c-, = -I

(1983) report of 1.89 - 1.99 for females of this spe-

this.

1)

,1.92

which

isa middle size compared to Musters'

Musters (1983) while reporting a mean SVL of82 ± 7mm for four females of this lizard and a meancies.

wherer=—,a =~( 7~'•

anc'V =surj se-clutch size of 3.7 for three females of Draco obscurusasformosus, made no reference to egg shape of this lizard. Hendrickson (1966) recorded a mean clutch size^L^(l + |c2 + !4 Clutch vol-of 2 in D. melanopogon (n = 14) and a mean clutch
size of 4 in D. volans (n = 20). This suggests thatquently used to estimate egg volume,
follows:wasI

V (in cm),

ume was defined as the sum of individual egg volume

clutch sizes in D.

in the clutch.

similar, being larger than that in D.

o. formosus

and D. volans may bemelanopogan.

Among these gliding agamid lizards, clutch size isResults

probably constrained by body size and clutch mass asa larger clutch mass is likely to reduce the horizontal

Size of female lizard

displacement covered during gliding. In the presentstudy, the total clutch mass accounted for almost 20

Body mass 10.02 g, snout-vent length (SVL) 87 mm;
taillength (TL) 167 mm; head length (HL) 16.78 mm;percent of female body mass.

jaw length (JL) 16.86 mm, head width (HW) 10.59mm; hind leg length (HLL) 270 mm; hind foot length

The three Draco species, D. obscurus formosus,D. melanopogan, and D. volans, all have contrasting(HFL) 170 mm; fore leg length (FLL) 270 mm; fore

egg shapes. Causility of variation of egg shape in thegenus are unknown. The eggs are distinctly pointed atfoot length (FFL) 9 mm.

both ends

inD. melanopogan but are ellipsoidal,

Clutch size, egg size, and shape quantization

blunt, and smoothly rounded at both ends in D. volansof eggs

(Hendrickson, 1966). Eggs of D. obscurus formosus is

The clutch consisting of 4 oviductal eggs; 2 eggs ina nearly perfect ellipsoid as indicated by the species-

which is very

each oviduct; 2 yolked ova and 4 whitish ova in rightspecific bicone coefficient, c 2 -0.021,ovary, 2 yolked ova and 5 whitish ova inclose to Ci = 0, the value for a perfect ellipse. Addi--yolked ova, 5.07 5.15
- 1.72veloped ova 1.50
shelledleft

ovary;

mm in diameter, white undemm in cross diameter. Eggs

withchalky-white parchment-likemembrane. Egg shape ellipsoidal, ends blunt, but eachturgid,

with pinched cap at ends (Fig. lb, 2). Pinched ends
solid, thick, firm, flat and in same plane, less than halfa semi-circle; outline of lip-like pinched structuretionally, the eggs are much rounder, as indicated by its

elongation factor of 1.36 which is smaller in eggs ofD. volans (E = 1.6) and D. melanopogon (E = 2.06),
as calculated

from Hendrickson's (1966) L andW

measurements of the eggs. The most unusual structureof D. o. formosus eggs is the flat projections pinchedoutwards from both ends. The significance of the cres-Asiatic Herpetological ResearchVol. 8, p. 28

1999

cent-shaped pinched ends is unknown, but they may
function as reserves of parchment shell materials toIverson, J. B. and M. A. Ewert. 1991. Physical charac-

allow the stretching and expansion of the egg during

eggs. Pp. 87-100. In D.C. Deeming and M.W.J. Fer-development.

guson (eds). Egg incubation: its effects on embryonicdevelopment in birds and reptiles. Cambridge Univer-Acknowledgmentssity Press, Cambridge, U.K.

The first author thanks the Malaysian Nature Society
for permission to participate in the Belum Scientificzation and the estimation of volume and surface area

Expedition; to L. S. Tay for field assistance, and to T.
Hikida for identifying the specimen. This study wasof reptile eggs and a comparison with avian

teristicsMaritz, M. F. and R. M. Douglas 1994. Shape quanti-of reptile eggs. Journal of Herpetology 28(3): 281291.

University, Singapore research grant RP10/92 to theMathematica. 1993. Mathematica [computer file]: asystem for doing mathematics by computer. Version

first author.

2.2, Wolfram Research, Champaign, Illinois, U.S.A.

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Draco

partially

supported by the Nanyang TechnologicalMusters, C.

Boulenger, G. A. 1903. Report on the batrachians andreptiles. Fasciculi Malayenses Zoology, 1:130-176,figs.

1-3, pis. 5-10.

Boulenger, G. A. 1908. Report on the Gunong Tahan
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May - Sept 1905. Ill Fishes, batrachians

and reptiles.

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Malay State

Museum, Singapore, 3: 61-69.
Diong, C. H., B. H. Kiew, and B. L. Lim. 1995. AnL.

M. 1983. Taxonomy of the genus

J.

(Agamidae,Lacertilia,Reptilia).

Zoolo-gische Verhandelingen, 199: 1-120.
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Olszowka and A. AR. 1974. The

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Preston,FW. 1968. The shape of birds eggs: mathe-matical aspects.
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AUK 85: 454-463.
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Smart, I.H.M. 1991. Egg-shape in birds. Pp. 101-1 16.

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