Biometric Relationships of the Eared Horse Mussel Modiolus auriculatus (Krauss, 1848)(Bivalvia: Mytilidae)Collected from

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05 1 Advanced Bio Tech. ISSN: 2319-6750 Vol.13 Issue 03 1 September 2013. www.advancedbiotech.in

Biometric Relationships of the Eared Horse Mussel Modiolus auriculatus (Krauss, 1848)(Bivalvia: Mytilidae)Collected from Byndoor, Karnataka, India

1* 1 2 3 3Tenjing Singh. Y , Thippeswamy. S , Krishna. M.P. , Narasimhaiah. N and Vineeth Kumar K

1. Department of Post-graduate Studies and Research in Biosciences, Mangalore University, Mangalagangothri, PIN - 574 199, Karnataka, India.

2. Field Marshal K. M. Cariappa College, Madikeri, PIN - 571 201, Karnataka, India.

3. Department of Applied Zoology, Mangalore University, Mangalagangothri, PIN - 574199, Karnataka, India.

Abstract

A study on the allometry of the eared horse mussel Modiolus auriculatus was carried out from a beach called Byndoor beach along the Karnataka coast, south west coast of India. Large individuals (>26 mm) of this species were absent from the intertidal rocky region of Byndoor. The calculated regression equations between breadth-length and width-length for the entire study period were B = 0.6503 + 0.4026 L and W = -0.1014 + 0.4260 L respectively. The observed values of breadth and width against their respective lengths revealed linear relationships. The monthly b values of breadth-length and width-length relationships ranged from 0.3039 (October 2010) to 0.4593 (July 2010) and 0.3579 (January 2011) to 0.4626 (May 2011) respectively. The data on

2.9260shell weight-length relationship for the entire period (SW = 0.000058L ) showed a non-linear pattern. The coefcient of allometry (b) values ranged from 2.3022 (October 2010) to 3.1196 (May 2011) for length-shell weight relationship. The maximum and minimum sizes of length were 25.91 (March 2011) and 2.64 mm (May 2011) respectively, whereas the maximum and minimum weights of shell weight were 1.0188 (May 2011) and 0.0008 g (May 2011) respectively.

Key words: Allometry; Bivalve; Mussel; Rocky shore; Byndoor.

Recieved: June 2013Accepted: July 2013Published: September 2013

Introduction

The south-west coast of India consists of long sandy beaches which are interspersed with rocky stretches. Modiolus auriculatus Krauss (Bivalvia: Mytilidae) is one of the horse mussels of the genus Modiolus occurring along the west coasts of India (Pati et al., 2011). In India, Modiolus species are well represented along the Karnataka coast (Thippeswamy, 1990; Boominathan et. al., 2008; Hemachandra, 2009). M. auriculatus is dominant among other Modious species at a rocky mussel bed which is very specic in the intertidal zone located at Byndoor (Karnataka). Allometry is the study of the relationship between two variables, or in general sense, allometry is the study of size and its consequences (Mayrat, 1970; Reiss, 1989). Morphometric analysis of mytilid species e.g. Perna viridis based on shell dimensions have been reported by several authors from the Karnataka coast (Thippeswamy, 1990; Hemachandra, 2008). They also studied the allometric weight-length relationship in P. viridis. Literature of allometry on the bivalve, M. auriculatus is scarce. A little information is available on its distribution (Pati et. al., 2011), but to our knowledge there is no information available on its allometry. More information is available on similar species found in other regions. The weight-length relationship, growth and survival rates of M. barbatus (Lok et. al., 2006), shell morphometric and weight-length relationships of M. adriaticus (Gasper et. al., 2001, 2002) and larval development, growth and abundance of M. modiolus (De Schweinitz and Lutz, 1976; Seed and Brown, 1978; Dinesen and Ockelmann, 2006), growth of M. striatulus (Raja, 1963) and growth,

mortality and recruitment pattern of M. metcalfei (Tumanda et. al., 1997) were described in some research articles. In sheries research, measuring weight and length are standard tasks and the data obtained are the backbone of many shery models. The shell weight-length and morphometric relationships of this eared horse mussel collected from a mussel bed are presented in this paper.

Materials and Methods

M. auriculatus were collected from the intertidal rocky zone of the sampling site, near to the Someshwara Temple at Byndoor (13°52' N and 74°36' E) from June 2010 to May 2011. These bivalves attached to a separate rock, but they were not found to other neighbouring rocks during the study period. A few samples were collected in July when sea was rough due to south west monsoon season. After the collection of samples, they were cleaned and dried. A total of 1202 clams ranging in size from 2.64 to 25.91 mm were measured. The length (maximum distance along the long axis of the valves), breadth/height (maximum distance from hinge to ventral margin) and width/depth/thickness (maximum distance between outer edges of two valves) were determined using a digital calliper (Mitutoyo-Digimatic calliper: CD-8"esx) to the nearest of 0.01 mm. The meat was discarded, the shell weight of the bivalve was determined to the nearest of 0.0001g with the help of an electronic balance (Sartorius electronic balance: 224S) after

*Corresponding Author E mail: [email protected]

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Biometric relationships of Modiolus auriculatus , Tenjing Singh. Y et. al.

the shell was dried again. Breadth, width and shell weight were e x a m i n e d t o e s t a b l i s h a r e l a t i o n s h i p w i t h l e n g t h . Morphometric relationship was e s t ima ted us ing the l i nea r equation, Y = a +bX, where a = intercept: initial growth coefcient and b = slope: relative growth rates of the variables, Y is breadth (mm) or width (mm) or and X is length (mm). The shell weight-length relationship was derived by applying the equation SW= aL . b

This equation can be expressed in its linearized from Log SW = Log a + b Log L, where SW = shell weight (g) and L = length (mm). The monthly means of each of the biological parameter (length, breadth, width and shell weight) were analyzed and presented as mean±SD (standard deviation). The biometric relationships between breadth-length (B-L), width-length (W-L) and shell weight-length (L-SW) were determined and represented in the form of graphs using SigmaPlot software (11.0).

Results

The da ta on morphomet r ic relationships (breadth-length and width-length) for the entire period is shown in Figure 1 and on monthly basis in Figure 2. Our data revealed that the variables are linearly related. Further the data depicted that long individuals are

wide (more height) and high (more thickness) and inversely the short individuals are narrow (less height) and low (less thickness). In the present study, the equations of breadth-length and width-length relationships for the entire study period were B = 0.6503 + 0.4026 L (or Log B = -0.1553 + 0.8258 Log L) and W = -0.1014 + 0.4260 L (or Log W = -0.4571 + 1.0751 Log L) respectively. The monthly b values of breadth-length and width-length relationships varied from 0.3039 (October 2010) to 0.4593 (July 2010) and 0.3579 (January 2011) to 0.4626 (May 2011) respectively (Table 1). The correlation coefcient (r) values are given in Table 1. The maximum values of length, breadth, width and shell weight were 25.91 mm, 10.88 mm, 11.44 mm and 1.0188 g respectively, whereas the minimum values of length, breadth, width and shell weight were 2.64 mm, 1.34 mm, 0.96 mm and 0.0008 g respectively (Table 2).

The data on shell weight-length relationship in for the M. auriculatusentire period and on the monthly basis are presented in Figure 3 and 4 respectively. The relationships between these variables showed non-

2.9260linear patterns. It was found that SW = 0.000058L or Log W = -4.2373 + 2.9260 Log L. The data on monthly and and correlation a b

Figure 1. Bivariate scatter diagrams of breadth-length and width-length relationship of M. auriculatus on monthly basisfrom Byndoor. Open circles indicate breadth-length relationship and dark circles indicate width-length relationship.

Figure 2. Bivariate scatter diagrams of breadth-length and width-length

relationships of M. auriculatus for the entire period. Open circles indicate

breadth-length relationship and dark circles indicate width-length relationship.

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coefcient ( ) values are presented rin Table 1. The values ranged from b2.606 (July 2005) to 2.945 (August 2005). The length-breadth and length-width relationships showed the same pattern throughout the study period, but the length-shell we igh t r e la t ionsh ip showed different pattern, i.e. non linear based on the ndings from the present study. According to Figure 3 and 4, short individuals were light and long individuals were heavy, thus indicating the increased weight of eared horse mussels with age.

The monthly variations of means and standard deviations of shell length, breadth, width and shell weight of M. auriculatus are shown i n Ta b l e 2 . F r o m t h e s h e l l dimensions studied, the mean shell length varied from 5.98 mm (August 2010) to 16.87 mm (July 2010) and the mean breadth ranged from 3.12 mm (August 2010) to 8.48 mm (July 2010) in the present study, whereas the mean width ranged from 2.46 mm (August 2010) to 7.08 mm (July 2010). At Byndoor, the values of shell weight were not more than 1.5 g. The mean shell weight of M. auriculatus was found to be in the range of 0.0212 g (September 2010) to 0.3590 g (July 2010).

Discussion

M. auriculatus from the rocky shore of Byndoor showed the shell length increased when the breadth, width and she l l weight increased . Hemachandra and Thippeswamy

(2008) found out that some green mussels (P. viridis) of the same length showed different breadth and width. Our ndings agree with the results of these two authors. The studies on allometric growth in M. adriaticus from the western Algarve coast (Gasper et al., 2001) showed a linear relationship .between shell breadth-shell length (Log B = -0.230 + 0.959 Log L) and shell width-shell length (Log W= -0.405 + 1.018 Log L). The statistics of regression are shown in Table 1. The b values of morphometric relationships are used to compare dimensional growth of M. adriaticus. In our present study, the b values of breadth-length and width-length were 0.8258 and 1.0751 respectively. These values are almost the same as in M. adriaticus from the western Algarve coast (southern Portugal). Hemachandra and Thippeswamy (2008) suggested that the shape of mytilid P. viridis rather than size provides more precise information on dimensional relationships. Growth in marine bivalves is expressed as an increase in weight/volume and body size which are often used as the most appropriate parameters for


Figure 3. Monthly variability in shell weight-length relationship in M. auriculatus

Figure 4. Weight-length relationship of M. auriculatus during the entire study period

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measurements (Seed, 1976; Bayne and Worrall, 1980). The constant b is also known as “coefcient of allometry” and shows the ratio of the growth rate of two variables analysed. The intercept (a) of all the months was negative which indicates a perfect linear relationship between the variables, length and shell weight (Table 1). The regression trends indicated variations in the growth pattern in different months. When the two variables have the same units the b value equal to unity, i.e. the rate of growth of variables is same and the relationship is said to be “isometric”. If the b value is greater than unity, it means the variable Y is increasing faster than the variable X and the relationship is known as positive allometry. The b value less than 1 indicates that the reverse is correct and the relation is known as negative allometry. In such cases the different units of measurements for X and Y are used and different criteria for the allometry is recommended (Gouldi, 1966). On the other hand, the b value generally lies between 2.4 and 4.5 according to Wilbur and Owen (1964) and the relation is said to be isometric when it is equal to 3 (Carlander, 1977). The lack of variation in the allometric relationship of M. auriculatus is due to the natural shell growth pattern. In Figure 1and , the growth generating circles exhibit almost linear growth in 2breadth and width. In spite of considerable economic importance of bearded horse mussel M. barbatus only a little information is available on the live weight (LW)-length (L) relationship (LW=0.0003L ) from Turkey (Lok et al., 2006). In M. adriaticus, 2.803 .the live weight (LW)-length (L) relationship was established to be LW = 0.00006L along the Algarve coast (Gasper et al., 2001).But 3.062

they did not show the shell weight-length relationship in their studies. The parabolic nature of the plot obtained reects the isometric growth of the parameters considered for the shell weight-length relationship. In the present study, some individuals of the same age showed different weights and these differences could be due to the physiological condition of mussels and environmental factors (Seed 1968; Lee 1986). The estimated b value (2.9260) of length-shell weight lies between 2.4 and 4.5 and the relation is isometric. The data on live weight from sh can be used directly in most of the sheries models applied e.g. sh population dynamics. When assessing the availability of food for man, the shell weight of mollusc is meaningless. But our ndings from the length and weight characteristics of the eared horse mussel M. auriculatus will play a small role in the shellsh industry of Karnataka and other states of India.

Conclusion

The relationships between breadth and length and width and length are seen to be of the linear type and that between length and shell weight follows the non linear type.

Acknowledgments

The rst author is thankful to the authorities of Mangalore University for providing facilities and Shashidhara Bhat, Department of Physics, Mangalore University for nding out the sampling site.

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Relationship a b r

Relationship a b r

Relationship a b r

Relationship a b r

Relationship a b r

Relationship a b r

Relationship a b r

Relationship a b r

Relationship a b r

Relationship a b r

Relationship a b r

Relationship a b r

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Breadth-length 0.6431 0.4146 0.9481

Breadth-length 0.4465 0.4264 0.9454

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January 2011

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M. auriculatus during the study period

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Citation: ., 2013. Tenjing Singh, Y., Thippeswamy, S., Krishna, M.P., Narasimhaiah, N and Vineeth Kumar K Biometric relationships of the earedhorse mussel Modiolus auriculatus (Krauss, 1848) (Bivalvia: Mytilidae) collected from Byndoor, Karnataka, India. Adv Bio Tech: 13(03): 05-10.


Biometric Relationships of the Eared Horse Mussel Modiolus auriculatus (Krauss, 1848)(Bivalvia: Mytilidae)Collected from

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