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Variability in the shape of the mandibles of grasshopper (Orthoptera: Acrididae) from selected places in Mindanao, Philippines.

INTRODUCTION

The relationship between mouth part structure and diet has been known for years. This connection between mouthpart morphology and specific food types is incredibly pronounced in class insecta [1]. As insects have evolved and adapted to new food sources, their mouthparts have changed accordingly. This is an extremely important trait for evolutionary biologists as well as systematics [2]

The relationship between grasshopper mouthpart and foods is far from precise. Mulkern (1967) was convinced that only the grossed determinations could be made between mandibular structure and diet. (i.e., graminivorous, forbivorous and herbivorous)[3][4][5][6][7]. Occasionally, grasshoppers with forb-feeding mandibles regularly feed on grasses or vice versa [8]. Nevertheless, there is some value in assessing mouthpart structure relative to predicting diet and habitat of grasshoppers, especially for many rare economic species that are unlikely to be studied in detail [1]. It is argued that as grasshopper evolved and adapted to new food sources the mouth parts have changed accordinglythus assessing the variability in the mandibles of will allow us explore the possible factors that contributes to such variations especially those collected from different geographical locations. The study made use of tools in geometric morphometrics (GM) which combine the powerful and flexible tool of multivariate statistics with explicit consideration of spatial relatives of parts and therefore make it possible to investigate morphological variation with different reference to the anatomical context of the structure under study [9][10] [11].

Methodology:

The sample insects collected from Maguindanao, North Cotabato and Lanao Del Norte, Philippines were classified into male and female sexes and the left right mandibles per individual were dissected and mounted in a glass slide. Using forceps and dissecting needles, the head capsules were first removed followed by the separation of mandibles. Individual images of the mandible were captured using a stereomicroscope with Macron Camera attached to its eyepiece. Images were cropped and saved in JPEG format for outlining using 100 points in the structural image.

The shape of the mandible was determined following the tools of GM which combine the powerful and flexible tools of multivariate statistics with explicit consideration of spatial relations of parts making it possible to investigate morphological variation [3]. TPSDig2 ver. 2.12 [12] was used to digitized a total of 100 specified landmark points for outlining the shape of the mandible. After outlining, the TPS curve was then converted into landmark points (XY) using TPSUtil ver 1.44 [12] which served as raw data for the analysis. Data were subjected to statistical analysis using the Past software ver 2.13[13]. Multivariate Analysis of Variance (MANOVA) was used to obtain the Wilk's Lambda and its p value and also the Pillai trace's p value which when will approach near zero would indicate a high discrimination or difference on variation between populations [14].

RESULTS AND DISCUSSION

There was no sexual dimorphism in the mandible shape in the grasshopper (data not shown) but canonical analysis show significant variations within, between and among the left and right mandibles of the populations of the grasshopper (Tables 1-3 and Figure 2).

The observed variation between the left and right mandibles of the grasshopper collected from three geographical regions can be attributed to differences in diet that would simply affect both body sides and therefore contribute to the observed asymmetry [15]. The differences in mandibular shape of the grasshopper between geographical might be associated with differences in biological and environmental factors in the area such as location, altitude, longitude, climatic variables, rainfall, human population density and vegetation [16][17]. Differences in foraging habitat, ecological factors and environmental changes such as destruction or habitat disturbances that could affect their food preferences and patterns of feeding may also explain the variability observed [17]. The observed variations in mandibular shapes might also be a result of genetic differences and phenotypic plasticity of individuals growing in different environments [18].

Conclusion:

Differences in mandible shape of grasshopper found in different areas of Mindanao assessed via outline-based analysis of geometric morphometrics could be due to differences in the consumption of food and foraging locations with varying environmental conditions. The use of geometric morphometric tools in this study contributed to a more quantitative way in describing the differences.

REFERENCES

[1] Smith, 2005. Mandibular Morphology of Some Floridian grasshoppers (Orthoptera: Acrididae). University of Floridan, Department of Entomology and Nematology, Gainesville, FL 32611

[2] Losos, J.B., 1990. Ecomorphy Performance Capability and Scaling of West India Anolis lizard: Ana Evolutionary Ecological Research, 1: 959-970.

[3] Gangwere, S.K., J.C McKinney, M.A. Ernemann and R.G. Bland, 1998. Food selection and feeding behavior in selected Acridoidea.9( insecta: OrtHOPTERA) OF THE Canary Islands, Spain J. Orth.Res, 7: 1-21.

[4] Chapman, R.F., 1964. The structure and wear of the mandibles in some African grasshopper. Proc.Zool.Soc. London, 142: 107-121.

[5] Gangwere, S.K., F.C. A.D. Evans, Nelson, 1976. The food habits and Biolofy Acrididae in an old-field Community. Southeastern Michigan. Great Lakes Entomol, 9: 83-123.

[6] Gangwere, S.K. and D.O. Spiller, 1995. Food selection and feeding behavior in selected Orthopter sen.lat of the Belearic Islands, Spain J.Ortho.Res., 4: 147-160.

[7] Gapud V.P.1968. The external Morphology of the head mouthparts of some Philipine Orthoptera. Philppine Entomol, 1: 47-67.

[8] Gangwere, S.K. and Morales, 1973. Food and selection and feeding behavior Iberian Orthopteroidea. An inst. Nac. Invest. Agrar.Ser.prot., 3: 251-337.

[9] Chapman, R.F., 1964. The structure and wear of the mandibles in some African grasshopper. Proc.Zool.Soc.London, 142: 107-121.

[10] Bookstein, F.L., 1999. Morphometric tool for Landmark data. Geometry and Biology. Cambridge University Press, New York.

[11] Adams, D., 1999. Methods for shape Analysis of landmark dates from articulated structures. Department of Ecology and Evolution. State University of New York at Stony Brook.NY117945245,USA.Evolutionary Ecological Research, 1: 950-970.

[12] Losos, J.B., 1990. Ecomorphy Performance Capability and Scaling of West India Anolis lizard: Ana Evolutionary Ecological Research, 1: 959-970.

[13] Rohlf, J.F., 2008. TPSDig version 2.12. Department of Ecology and Evolution, State University of New York at story Brook, New York.

[14] Hammer, O., D.A.T. Harper, P.D. Ryan, 2001. PAST: Paleontological Statistical software package for education and data analysis. Paleontol Electron, 4(1): 9.

[15] Chricton, N., 2000. Information point. Wilk's lambda. Journal of Clinical Nursing. Blackwell Science Limited, pp: 369-381.

[16] Klingenberg, C.P., 2002. Development and Instability as a research tool: Using patterns of fluctuating asymmetry to infer the development origins of morphological integration.

[17] Demayo, G. Cesar, Paul Quim Palomares and J. Mark Anthony Torres, 2011. Describing Shapes of Mandible in Selected Populations of the Rice Striped Stem Borrers (Chilo suppressalis, Walker, 1863) Associated with Different Rice types. Australian Journal of Basic and Applied Sciences, 5(6): 739-747.

[18] Zahiri, R., A. Sarafrazi, L. Salehi and G.J. Kunkel, 2006. A geometric morphometric study on the populations of Rice Stem Borer, Chilo suppressalis Walker (Lepidoptera: Cambridae) in Northern Iran. Zoology in the Middle East., 38: 70-84.

[19] Albutra, B. Queenilyn, J. Mark Anthony Torres and G. Cesar Demayo, 2012. Shapes of mandibles of white stemborer Scirpophaga innotata (Walker, 1863) larvae associated with different rice varieties. Egypt. Acad.J. Biolog. Sci., 5(1): 45-58.

(1) Graziella M. Barcebal, (2) Kimverly Hazel I. Coronel, (2) Mark Anthony J. Torres, (2) Cesar G. Demayo

(1) Southern Christian College-United Church Of Christ in the Philippines, Midsayap North Cotabato, Philippines

(2) Department of Biological Sciences, College of Science and Mathematics, MSU-Iligan Institute of Technology, Iligan City, Philippines.

ARTICLE INFO

Article history:

Received 23 June 2015

Accepted 25 July 2015

Available online 30 August 2015

Corresponding Author: Kimverly Hazel I. Coronel, Department of Biological Sciences, College of Science and Mathematics, MSU-Iligan Institute of Technology, Iligan City, 9200, Philippines.

E-mail: kimverlyhazelcoronel@gmail.com

Table 1: Canonical variates analysis of RW scores.

Wilk"s Lambda = 0.09744   Pillai trace =1.685
df1 = 75                       df1 = 75
Df2 = 555                      df2 = 595
F = 4.633                      F = 4.032
P (same) = 1.708E-26      P(same) = 4.693E-22

Table 2: Pairwise comparisons between mandibles of
Oxya sp. based on RW scores.

                    left mandible   left mandible    right mandible
                       (North       (Maguinadanao)       (Lanao
                      Cotabato)                        del Norte)

left mandible        0.000401448      0.00052383        0.241781
(Lanao del Norte)

left mandible                         0.00343195      0.000356015
(North Cotabato)

left mandible                                         2.20057E-05
(Maguinadanao)

right mandible
(Lanao del Norte)

right mandible
(North Cotabato)

                     right mandible    right mandible
                    (North Cotabato)   (Maguindanao)

left mandible          0.00185339       2.87432E-05
(Lanao del Norte)

left mandible           0.570868         0.00544924
(North Cotabato)

left mandible          0.0236719         0.0300935
(Maguinadanao)

right mandible        0.000591525       4.82271E-06
(Lanao del Norte)

right mandible                           0.0138552
(North Cotabato)

Table 3: Confusion matrix between mandibles of
Oxya sp. based on RW scores.

                    left mandible   right mandible   left mandible
                       (Lanao           (Lanao          (North
                     del Norte)       del Norte)       Cotabato)

left mandible            17               1                1
(Lanao del Norte)

right mandible            0               14               0
(Lanao del Norte)

left mandible             0               2               15
(North Cotabato)

right mandible            7               1                0
(North Cotabato)

left mandible             1               1                0
(Maguinadanao)

right mandible            0               1                3
(Maguindanao)

                    right mandible   left mandible    right mandible
                        (North       (Maguinadanao)   (Maguindanao)
                      Cotabato)

left mandible             7                0                1
(Lanao del Norte)

right mandible            1                3                1
(Lanao del Norte)

left mandible             0                0                3
(North Cotabato)

right mandible            21               0                1
(North Cotabato)

left mandible             0                16               0
(Maguinadanao)

right mandible            0                0                17
(Maguindanao)

Legend: 1--left mandible (Lanao del Norte); 2--right mandible
(Lanao del Norte); 3--left mandible (North Cotabato);
4--right mandible (North Cotabato); 5--left mandible
(Maguinadanao); 6--right mandible (Maguindanao)
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Article Details
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Author:Barcebal, Graziella M.; Coronel, Kimverly Hazel I.; Torres, Mark Anthony J.; Demayo, Cesar G.
Publication:Advances in Environmental Biology
Article Type:Report
Geographic Code:9PHIL
Date:Aug 1, 2015
Words:1594
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