**Morphometric**** geometric study of wing shape in Culex
quinquefasciatus Say (Diptera:
Culicidae) from Tamil Nadu, India**

**K. Manimegalai 1, M. Arunachalam 2 & R. Udayakumari
3**

1,3 Avinashilingam
University for Women, Coimbatore, Tamil Nadu 641043, India

2 Sri Paramakalyani Centre for
Environmental Sciences, Manonmaniam Sundaranar University, Alwarkurichi,
Tamil Nadu 627412, India

Email: 1 manijeysu@gmail.com ; 2 arunacm@gmail.com (corresponding author)

Date
of online publication 26 May 2009

ISSN
0974-7907 (online) | 0974-7893 (print)

**Editor:** R. Ramanibai

**Manuscript
details:**

Ms
# o1982

Received
19 April 2008

Final
received 28 February 2009

Finally
accepted 29 April 2009

**Citation:
**Manimegalai, K., M. Arunachalam & R. Udayakumari
(2009). Morphometric geometric study of wing shape in
*Culex** quinquefasciatus
*Say (Diptera: Culicidae)
from Tamil Nadu, India. *Journal of Threatened Taxa*
1(5): 263-268.

**Copyright:** © K. Manimegalai, M. Arunachalam &
R. Udayakumari 2009. Creative Commons Attribution 3.0
Unported License. JoTT
allows unrestricted use of this article in any medium for non-profit purposes,
reproduction and distribution by providing adequate credit to the authors and
the source of publication.

**Author
Details: **K. Manimegalai, is a Reader and
the fields of specialization are: control of vector species of mosquitoes using
plant extracts, mosquito taxonomy using wing shape analysis.

M. Arunachalam, is a Professor
and his fields of specialization are: stream / river / wetlands ecology, fish
ecology, fish habitat mapping using GIS, fish taxonomy and phylogenetics,
morphometric geometry of shape analysis of the wings
of aquatic insects and mosquitoes and shape analysis of cypriniform
fishes.

R. Udayakumari was a M.Phil.,
Scholar

**Acknowledgements:**
We acknowledge the help from Mr. M. Murugan, Sri Paramakalyani Centre for Environmental Sciences of Manonmaniam Sundaranar
University. We also acknowledge the help from Prof. James R. Rohlf for his reply to our questions while using his programmes.

**Abstract: **The
morphometric geometric study was carried out in 10
males and 10 females of *Culex** quinquefasciatus*.
There are 23 landmarks corresponding to points at which wing veins
either branch or intersect the margin of the wing. Relative warp analysis has
been proved to be very efficient in distinguishing the variation of shape in
male and female wings. The multivariate
analysis of co-variance (MANCOVA) showed a clear separation of the male and
female wings.

**Keywords:** *Culex** quinquefasciatus*,
Geometric morphometrics, Landmarks, MANCOVA, Relative
warp

Landmark based
geometric morphometrics have been increasingly used
to explore systematic, developmental, ecological or pathological differences
among individuals or populations, The approach of morphological landmarks is
more appropriate as it represents advantages of additional information and the
mode of variation is well understood (Bookstein
1989). Study of wing morphology in
Lepidoptera and other insects using the geometric approach of shape variation
provides an insight to taxonomy (Rohlf 1996). The genus *Culex*
is a principal vector species in the peninsular India and the available keys
are inadequate to study the morphological similarity of *Culex*
species in this region and the present study is a pioneering attempt to
distinguish the mosquito species based on wing morphometry.
This paper forms a part of a major work on various aspects of different species
of mosquitoes by the senior author.

Adult mosquitoes were
collected from three localities in the Coimbatore city (the third largest city,
10050’-11002’N & 76056’-77001’E in the Indian state of Tamil Nadu with an
area of 1287 km² with a population of 9,40,000 and the elevation is 442m above
mean sea level). Wings were removed and
photographed with consistent magnification and the digital images were used for
the study. Landmarks (23) of the wings of 10 males and females of *Culex** quinquefasciatus* were used for the
analysis following the method of Rohlf & Slice
(1990). The landmarks are the
intersections of wing veins with the wing margin, intersections of cross veins
with major veins, vein branch points , the apparent anterior attachment of the
wing to the body , and the notch between the posterior wing margin and the alula (Figs. 1-2).
We digitized the photographs with the programme
TPSDIG (Rohlf 1996a) and from the landmark
coordinates we
computed the consensus configuration using the programme TPSRELW (Rohlf 1997)
which implements the algorithms described by Rohlf
& Slice (1990) and Bookstein (1996).

For each wing the
uniform component of shape variation (affine) is estimated and the first
uniform component accounts for the stretching along the x-axis of the
configuration whereas the 2nd uniform component
indicates dilations or compressions along the y-axis. The uniform components were estimated by the Linearized Procrustes method of Bookstein (1996b).
All wings were scaled to unit centroid size
before alignment by the GLS super imposition method.

Thin-plate spline of relative warp analysis was carried out using the
coordinates of all aligned wings (Bookstein 1991; Rohlf 1993) and this will give the display and direction of
shape differences among the two species (herein
the male and female wings of *Culex** quinquefasciatus*).
The Thin-plate splines technique (Bookstein 1989) has the function of interpolation to the
landmark coordinates of each wing against the reference configuration in order
to make the landmarks homologous. The
bending energy matrix resulting from the thin-plate spline
function fitted to the reference configuration will be modified as orthogonal
axes which is called the principal warp which describe shape distortions of the
reference configuration. The projection
of the super imposed wings onto the principal warps produces the partial warp
scores. These scores describe the
deviations from the
reference configuration. The relative
warps are the principal components of the variation among wings (Bookstein 1989 & 1991; Rohlf
1993). The coverage configuration
of landmarks are used as the reference which is aligned to its principal
axis. The relative warps are computed
with the scaling option a = 0, which weights all landmarks equally. Otherwise
all of the principal warps have the same weight and is considered to be more
appropriate for systematic studies (Rohlf 1993; Rohlf et al. 1996).
Weight matrix a = 1 corresponds to the relative warp analysis which
shows variation among wings in the principal warps with larger bending
energies.

Deformation grids using
Thin-plate splines were used to graphically represent
the patterns of shape variation among the landmarks. We analyzed the warp
matrix with multivariate analysis of variance (MANCOVA).

The multivariate
analysis of co-variance (MANCOVA) showed a clear separation of male and female
mosquitoes of *Culex** quinquefasciatus*
based on wing shape. There is no overlap
of any landmark data between the male and the female and the data of selected
pairs of point are the distance measurements used as multidimensional space (Goodall 1991).

The use of a parameter
in this study following Rohlf (1993) is to identify
appreciable changes in the value less than zero which will result in more
weight to the small-scale features. In
taxonomic studies a = 0
gives an equal weighting in the analysis and in growth study to
record the allometry
where differences are more and hence a = 1 is also used. As the present study reveals variations
between male and female of *Culex** quinquefasciatus* the study of using a = 1 is tried to find out any
interesting patterns at different scales.

The bending energy
concept used in the study is the quantity of the physical properties of the
thin metal sheets and used as Thin-plate spline and
the functions used in organisms do not imply biological significance to the
parameter. The use of spline (Rohlf 1993) does not
imply that biological tissues behave like metal sheets but it is simply a
convenient function that is able to express the differences in two
configurations of landmarks as a continuous deformation. This Thin-plate spline
is the assessment of shape deformations such as bio-orthogonal grids (Bookstein et al. 1985).

The Procrustes
plots in the relative levels of variation at different levels are difficult to
find out the displacement of landmarks.
Hence, the method of relative warps has been used to identify the
co-variation very effectively. From this
study one can easily identify the movement of landmark either towards the base
of the wings or towards the tip of the wings.

**Bookstein****,
F.L., B. Chernoff, R.L. Elder, J.M. Humphries, G.R.
Smith & R.E.Strauss (1985).**
*Morphometrics** in Evolutionary Biology*. Special
Publication 15, Academy of Natural Sciences of Philadelphia, Philadelphia,
277pp.

**Bookstein****,
F.L. (1989).** Principal Warps: Thin - plate splines and the decomposition of deformations. IEEE *Transactions
on Pattern* *Analysis and Machine Intelligence* 11: 567-585.

**Bookstein****,
F.L. (1991).** *Morphometric** Tools for Landmark Data*. *Geometry
and Biology*. Cambridge University Press, 435pp.

**Bookstein****,
F.L. (1996a).** A standard formula
for the uniform shape component in landmark data, pp. 153-168. In:
Marcus, L.F., M. Corti, A. Loy, G. Naylor & De
Slice (eds.),* Advances in Morphometrics*. Plenum Publishing Corps. New York.

**Goodall****, C.R. (1991).**
Procrustes
methods in the statistical analysis of shape, *Journal of Royal Statistical
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**Rohlf****, F. J.& D. Slice (1990).** Extensions of the procrustes method for
the optimal super impostion of landmarks. *Systematic
Zoology* 39: 40-59.

**Rohlf****, F.J. (1993).**
Relative warp analysis and an example of its applications to
mosquito wings, pp. 131-159. In: Marcus, L.F., E. Bello, A. Garcia Valdecasas (eds.), *Contributions**
to Morphometrics.* Monografia
del Museo Nacional de Ciencias Naturales 8.Madrid.131-159.

**Rohlf****,
F.J., A. Loy & M. Corti (1996).**
Morphometric analysis of old world Talpidae (Mammalia, Insectivora) using
partial warp scores.

*Systematic Biology*
45: 344- 362.

**Rohlf****.****
F.J. (1996a).** *TPSDIG*.
Program of digitizing images for analaysis by Thin plate splines (Windows) Ver.
1.08, Department of Ecology and Evolution, State University of New York, Stony
Brook.

**Rohlf****, F.J. (1996b).**
Morphometric spaces, shape components and the effects of linear
transformations, pp. 117-129. In: L.F. Marcus, M. Corti,
A. Loy, G. Naylor, D.E. Slice (eds.) *Advances in Morphometrics*.
NATO Advance studies Institute on Morphometrics in II
Ciocco, Italy. Plenum Publishing Corp, New York.

**Rohlf****,
F.J. (1997). ***TPSRELW.*
Program for analyzing landmark data with Thin-plate spline
using relative warps (Windows ) Ver.1.14, Department
of Ecology and Evolution, State University of New York, Stony Brook.