Journal of Entomology and Zoology Studies 2017; 5(5): 178-183 E-ISSN: 2320-7078 P-ISSN: 2349-6800 JEZS 2017; 5(5): 178-183 © 2017 JEZS Received: 24-07-2017 Accepted: 25-08-2017 BK Mahapatra a) ICAR-Central Institute of Fisheries Education, Kolkata, India b) 32 GN Block, Sector V, Salt Lake City, Kolkata, West Bengal, India S Bhattacharya a) ICAR-Central Institute of Fisheries Education, Kolkata, India b) 32 GN Block, Sector V, Salt Lake City, Kolkata, West Bengal, India A Pradhan a) ICAR-Central Institute of Fisheries Education, Kolkata, India b) 32 GN Block, Sector V, Salt Lake City, Kolkata, West Bengal, India Correspondence BK Mahapatra a) ICAR-Central Institute of Fisheries Education, Kolkata, India b) 32 GN Block, Sector V, Salt Lake City, Kolkata, West Bengal, India Some aspects of biology of Chiti kankra, Varuna litterata (Fabricius, 1798) from Sundarbans, West Bengal, India BK Mahapatra, S Bhattacharya and A Pradhan Abstract The length-weight relationship and condition factor of Chiti Kankra, Varuna litterata (Fabricius, 1798) was studied from Sundarbans part of West Bengal, India during August 2013 to September 2014. A total of 401 specimens of V. litterata (241 males and 160 females) were used for the study. The weight of female ranged between 2.22g to 22.53g whereas the weight of male ranged between 1.06g to 41.48g. The exponential values (b) for carapace length/width-weight relationship of male were 3.1367 and 3.2187 respectively which suggests positive allometric growth. But in females carapace length-weight relationship showed negative allometric growth (b=2.8058) and carapace width-weight relationship showed positive allometric growth (b=3.0450). The present study showed that the value of condition factor (K) of the studied male crab was 1.21, female 1.19 and for combined sexes 1.20. The sex ratio was 1 female: 1.50 male. The present study reveals that there was a strong co-relation between various morphometric characters viz. carapace length/width, abdomen length/width, chelar propodous length/height and weight. Keywords: Biology, Chiti Kankra, Varuna litterata, Sundarbans 1. Introduction In population studies, morphometric analysis provides a powerful complement to genetic and environmental stock identification approaches [1] and length-weight relationships as well as the condition factors are considered to be useful parameters for assessing the well-being of the individuals and for determining possible differences among different stocks of the same species [2]. It is based on the hypothesis that heavier fish of a particular length are in a better physiological condition [3]. In crustaceans, as growth progresses, certain dimensions of the animal’s body may grow much more than others, resulting in the phenomenon known as relative growth [4]. Work on different biological and ecological aspects of different crabs were done by various workers [5-10] but no such has been done on Varuna litterata. The herring bow crab, V. litterata is very common in low saline water of Sundarbans and popularly known as chiti kankra. They are usually inhabit in the mangroves, estuarine and freshwater environments, in shallow sub tidal regions and usually found under rocks, logs and dead leaves and lives in burrows along the embankments of ponds, creeks and shallow banks [11]. With its legs shaped as paddles used for swimming, it is sometimes called the paddler crab or ocean paddler crab. It has been recorded as commercially important species in India especially in Bengal, where it is eaten by poor people, and its numbers compensate for its small size. Regarding the size and weight range of this crab no specific data available and also morphometrics study as well as condition factors were not done by any workers on V. litterata. The main objective of the current study was to assess the size and weight range of the crab and make a proper relationship between some body dimensions and weight of V. litterata at Sundarbans, West Bengal. Additionally, the variations in the condition factor (K = carapace length/weight) was analysed sex wise as well as for combined sexes. 2. Materials and Methods i) Study area: Sundarbans Biosphere is the largest protruding delta on this planet covering about one million ha in the delta of the rivers Ganga, Brahmaputra and Meghna is shared between Bangladesh (~60 %) and India (~40 %). In the present study we have been working with the Indian Sundarbans (Latitude 21° 32'-22° 40' N, Longitude 88° 22'-89°0' E). ~ 178 ~ Journal of Entomology and Zoology Studies Sundarbans occupy the north east coast of India (9630 square kilometre area) and are bounded by River Hooghly in the West, River Raimangal in the East, Bay of Bengal in the South and Dampier Hodges line in the North. The place located map is cited below (Fig. 1). Fig 1: Image showing the actual position of the Sundarbans in India ii) Specimen collection: A total of 401 specimens of V. litterata (241 males and 160 females) were collected from Indian Sundarbans throughout the August 2013 to September 2014. The crabs were washed thoroughly to remove all mud, sand and epizoic forms and were preserved in 4% formalin. The dorsal and ventral views of the male and female crab are shown hereby (Fig. 2). Fig 2: The identical dorsal and ventral views of male and female Varuna litterata (Fabricius, 1798) iii) Measurement: The specimen weighted to the nearest g by using an electrical balance. The measurements used for morphometric studies in V. litterata are taken by using an accurate scale to the nearest mm (Fig. 3) Fig 3: The measurements used for morphometric studies in Varuna litterata (Fabricius, 1798) iv) Methodology: The L-W data were analysed according to the method mentioned by Le Cren [12]. The equation of the parabolic relationship of the form W = aLb was used where W represents weight of the fish in gram; L being the total length in millimetre; ‘a’ the constant and ‘b’ an exponent to which L can be raised. The equation was calculated for male, female and combined sex sample and a linear relationship between the logarithm length, width and logarithm weight was found from the examination of scatter diagram. Condition Factor was calculated by using the following formula K=100W/L3, where ‘W’ denotes weight of the crab in g and ‘L’ denotes the carapace length of the crab in mm. v) Statistical analysis: The variation between the regression coefficients (b) in male and female crab was calculated using ANOVA (Analysis of covariance). The coefficient of correlation and the regression line was calculated and drawn from the formula given by Spiegel [13]. All data were analysed by using internationally reputed Software Statistical Package for Social Sciences (SPSS-16.0) and MS Excel. ~ 179 ~ Journal of Entomology and Zoology Studies 3. Results It was observed from the above study, that the female possess a broader abdomen than that of the male. The descriptive statistics i.e. minimum, maximum and mean results for widths (mm), lengths (mm), weights (g) and standard deviation (±SD) of carapace, abdomen and chelar propodous used in the analysis of length/width and weight relationships are given (Table: 1). The weight of female ranged between 2.22g to 22.53g whereas the weight of male ranged between 1.06g to 41.48g. It is observed that male crabs are heavy than the female and it found in wider range. Table 1: Length weight characteristics of carapace of categories Male, Female, and Combined of Varuna litterata WT CW CL MAX MIN AVG STDEV 22.53 2.22 7.0578 3.5418 47 24 33.0925 4.7658 44 20 30.1172 4.5802 MAX MIN AVG STDEV 41.48 1.06 7.2437 5.9933 54 16 32.0946 5.9574 AbW AbL ChL ChH 30 14 20.9012 3.4912 36 15 23.6604 3.6677 42 5 15.7716 6.4793 19 3 6.9876 2.0240 Female Male 50 18 37 42 23 14 3 6 6 3 28.9794 8.2386 18.4691 17.2921 9.0370 5.5386 2.1068 3.8207 6.1092 4.0067 Combined MAX 41.48 54 50 30 37 42 23 MIN 1.06 16 14 3 6 5 3 AVG 7.2395 32.4789 29.4218 13.2903 20.5210 16.6476 8.2034 STDEV 5.1553 5.5280 5.2016 6.7800 4.5319 6.2982 3.5010 [Legends: WT = Total body weight; CW = Carapace width; CL = Carapace length; Ab W = Abdominal width; Ab L = Abdominal length; Ch L = Chelar propodus length; Ch H = Chelar propodus height.] The Correlation coefficient r2 was used as an indicator of the quality of the linear regressions [14]. It was observed that a high degree of correlation between r and r2 parameters (Table: 2-4). The result justified the fact that there was a strong significant relationship between length and weight of V. litterata. In the present study higher regression coefficient (b>3) were recorded for both the sexes and combined sex and it was an indication of positive allometric growth. The exponential values (b) for carapace length/width-weight relationship of male which were 3.1367 and 3.2187 respectively showed that is positive allometric growth and there is marked deviation from the isometric growth pattern. But in females carapace length-weight relationship showed negative allometric growth and carapace width-weight relationship showed positive allometric growth. Length-width relationship between chelar propodous and abdomen showed negative allometric growth. Table 2: Relationship between carapace length, width and weight of Varuna litterata Variation Carapace length/weight Carapace width/weight Carapace width/ carapace length Sex Equation Male Female Combined Male Female Combined Male Female Combined Log W = - 3.7947 + 3.1367 L Log W = - 3.3341 + 2.8058 L Log W = - 3.6255 + 3.0136 L Log W = - 4.0581 + 3.2187 L Log W = - 3.8126 + 3.0450 L Log W = - 3.9692 + 3.1549 L Log W = -0.0404 + 0.9970 L Log W = 0.1918 + 0.8978 L Log W = -0.0497 + 1.0042 L Regression statistics R R2 0.9477 0.8981 0.9127 0.8330 0.9418 0.8871 0.9463 0.8955 0.9326 0.8697 0.9358 0.8758 0.9702 0.9414 0.9536 0.9094 0.9654 0.9320 Table 3: Relationship between abdominal length, width and weight of Varuna litterata Variation Sex Equation Abdomen length/weight Male Female Combined Log W = -2.3460 + 2.4767 L Log W = -2.8943 + 2.6999 L Log W = -1.6120 + 1.8383 L Log W = -0.6968 + 1.6251 L 1.625162073 Log W = -2.6112 + 2.5965 L Log W = 0.3391 + 0.4139 L Log W = 0.6991 + 0.6191 L Log W = 0.2375 + 0.8606 L Log W = 0.9324 + 0.3462 L Abdomen width/weight Abdomen width/ Abdomen length Male Female Combined Male Female Combined ~ 180 ~ Regression statistics R R2 0.8371 0.7008 0.9005 0.8110 0.7449 0.5549 0.6907 0.4771 0.9282 0.3859 0.7786 0.9225 0.7965 0.8617 0.1489 0.6062 0.8510 0.6344 Journal of Entomology and Zoology Studies Table 4: Relationship between chelar propodous length, width and carapace length, width of Varuna litterata Variation Sex Equation Chelar propodous length/width Male Female Combined Log W = -0.4121 + 1.0972 L Log W = 0.3653 + 0.3939 L Log W = -0.0888 + 0.8123 L Log W = -0.9210 + 1.4679 L 1.625162073 Log W = -0.7592 + 1.3068 L Log W = -0.7884 + 1.3566 L Log W = -1.7400 + 1.8288 L Log W = -1.1762 + 1.3580 L Log W = -1.4256 + 1.5782 L Log W = -1.0417 + 1.5045 L Log W = -0.9369 + 1.3884 L Log W = -0.9403 + 1.4183 L Log W = -1.9119 + 1.8888 L Log W = -1.4203 + 1.4820 L Log W = -1.6448 + 1.6783 L Carapace length/Chelar propodous length Carapace length/Chelar propodous height Carapace width/ Chelar propodous length Carapace width/ Chelar propodous height Male Female Combined Male Female Combined Male Female Combined Male Female Combined Scatter diagrams each for carapace length/width, abdominal length/width and chelar propodus length/height in respect to V. litterata was obtained of male, female and combined crabs (Fig. 4-7). From the closeness of the scatter diagram and from Regression statistics R R2 0.8856 0.7844 0.5049 0.2549 0.7437 0.5531 0.8608 0.7410 0.5674 0.7064 0.8657 0.7557 0.7524 0.8585 0.5676 0.7100 0.8700 0.7766 0.7692 0.3220 0.4990 0.7494 0.5712 0.5662 0.7371 0.3222 0.5041 0.7570 0.6031 0.5918 the parabolic nature of the plot, it was clear that there is a good relationship between every variables of the crab and also the suitability of fitting the exponential formula, W=aLb to the data. Fig 4: Logarithmic relationships between carapace length/width–weight of Varuna litterata Fig 5: Logarithmic relationship between abdominal length/width–weight of Varuna litterata ~ 181 ~ Journal of Entomology and Zoology Studies Fig 6: Logarithmic relationship between length/width relationship of abdomen, carapace and chelar propodous of Varuna litterata Fig 7: Logarithmic relationship between length/width relationship between carapace and chelar propodous of Varuna litterata The variation of condition factor reflects information on the physiological state of the fish. The mean K value was calculated of male, female and combined sex for carapace length/weight (Table: 5). The condition factor indicates the good physiological condition like well growth, good L-W relationship of the crab. It was observed that the mean K value of male crabs were little better than female crabs. ~ 182 ~ Table 5: K value for carapace length/weight of Varuna litterata Variation Carapace length-weight Sex Male Female Combined sex K value 1.21 1.19 1.20 Journal of Entomology and Zoology Studies 4. Discussion In studying spiny crab species, such as the herring bow crab, measuring the length of the crabs is often somewhat difficult, and during attempts to measure them, sometimes the extremities of the crab can be broken. It is therefore convenient to be able to convert into length (width) when only the weight is known or length-weight regression may be extensively used to estimate length from weight. An overview of literature reveals that the length–weight relationship of crab differs from one species to another in a particular population. Several biological factors like sex, size, physiological condition, seasons, food intensity, gonadal maturity and fatness have significant influence over length-weight relationship on crab [15]. In this study maximum 54mm carapace width and 50mm carapace length are observed in V. litterata. Males presented a higher regression coefficient than females, similar to other brachyuran crabs [16, 17]. The study on the sex ratio showed 1 female: 1.50 male. From the present study it is observed that the allometric relationship between the set of characters studied which is consistent with general scaling trends with body size of animal [18]. Like brachyuran crabs V. Litterata males are larger and heavier than females [19] . In most cases the relationship was positive and highly significant which indicates the good ecological condition of the crab in the Sundarbans Mangrove area. The condition factor of the studied male crab was 1.21, female 1.19 and for combined sexes 1.20 revealed that the good physiological condition of the crabs and male grow better than female [20]. From the data presented, a distinct relationship was found between length, width and total weight, as judged from the closeness of the scatter dots, as well as from the parabolic nature of the plot. 5. Conclusion The result of the study will be useful to the researchers and policy planners. The condition factor of the fish proved that the physiological condition of the crabs of Sundarban area were quite good. The present study also helpful for the fishery managers to implement adequate adaptation-centric regulation for sustainable fisheries management of V. litterata. 6. Acknowledgements Authors wish to express our sincere gratitude to the Director, ICAR-Central Institute Fisheries Education, Mumbai, for his encouragements and providing the facilities for the research work. 7. References 1. 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