208 Bulgarian Journal of Agricultural Science, 12 (2006), 208-217 National Centre for Agrarian Sciences Investigation on Fecundity and Egg Size in Cultured and Natural Crayfish Population of Astacus leptodactylus Esch. in Bulgaria P. VASILEVA, A. ZAIKOV and T. HUBENOVA Institute of Fisheries and Aquaculture, Varna, Branch Plovdiv, BG-4003 Plovdiv, Bulgaria Abstract VASILEVA, P., A. ZAIKOV and T. HUBENOVA, 2006. Investigation on fecundity and eggs size in cultured and natural crayfish population of Astacus leptodactylus Esch. in Bulgaria. Bulg. J. Agric. Sci, 12: 208-217 The objective of the present study was investigation on fecundity (pleopodal egg number) and egg size (weight and diameter) of both a cultured and a natural Narrow-clawed crayfish population (Astacus leptodactylus Eschscholtz, 1823). Further the relationship between these features and the body weight and length, and length and width of the carapace was studied. The investigation was carried out in May 2001 on 71 female crayfish, reared in carp ponds and in May 2002 on 60 females from Piasachnik dam-lake in Bulgaria. It was found out that the fecundity of the pond-reared crayfish population was 162.7+104.1 pleopodal eggs; the average egg weight was 13.62+1.72 mg and the egg diameter was 2.96+0.2 mm. The fecundity of the natural crayfish population in Pyasachnik dam-lake was 200.8+89.2 pleopodal eggs; the average egg weight was 12.36+1.71 mg and the egg diameter was 2.75 + 0.17 mm. There are significant differences between the number of eggs in both investigated populations. The crayfish females from Pyasachnik dam-lake have more pleopodal eggs compared to those reared in ponds (P<0.05). On the contrary, the average values of egg weight and diameter of the pond-reared population were bigger (P<0.001) in comparison to the dam-like ones. A low correlation coefficient (r<0.3) was found between the egg weight and diameter and the investigated morphometric body features, but a considerable correlation (0.6<r<0.7) was proved between the egg number and the same morphometric body features. Key words: Astacus leptodactylus, egg size, exterior body parameters, fecundity Introduction To define the numbers of the generation, the establishment of fecundity is of importance. The study of 11 lake populations of Narrow-clawed crayfish Astacus leptodactylus Esch. in Russia and Belarus shows that fecundity is greatest in the azaikov@yahoo.com
Investigation on Fecundity and Egg Size in Cultured and Natural Crayfish Population... 209 populations of South Russia, where the center of the zoogeographic area of the distribution of this species is, and reduces in number towards to Belarus and Turkey (Alekhnovich and Kulesh, 1996; Koksal, 1988). The body length of the individuals from the 11 populations varies from 7 to 17 cm, the number of the pleopodal eggs being 5-820. The investigation on populations from three crayfish species of the genus Astacus, points out that the ovary and pleopodal fecundity (number of ovary and pleopodal eggs) respectively were as follows: Astacus leptodactylus caspius has from 67 to 437 ovary eggs and from 48 to 264 pleopodal eggs, Astacus pachypus (Rathke, 1837) has from 50 to 110 ovary eggs and from 5 to 52 pleopodal eggs and Astacus kessleri (Schminkewitsch, 1884) has from 51 to 503 ovary eggs and from 37 to 320 pleopodal eggs (Cherkashina, 1970). A positive correlation between the dimensions of the body of female crayfish and the number of the ovary and pleopodal eggs is found out (Jarvelkung, 1958; Abrahamsson, 1971, 1972; Lindqvist and Louerkari, 1975; Lahti and Lindqvist, 1983; Harlioglu et al., 2004). The more the body weight and body length increases, the greater the fecundity becomes, however, when certain dimensions are reached (the latter being different for different populations) the above correlation becomes reverse. This phenomenon were registered mainly for north populations (Alekhnovich and Kulesh, 1996). The egg size of freshwater crayfish varies in relatively great ranges. Differences exist both in separate species and within the framework of a given species and even given individual (Cukerzis, 1989). The dependence between the basic exterior body parameters and the egg size have been investigated for the following species: Astacus astacus (Cukerzis, 1989; Abrahamsson, 1971; Lahti and Lindqvist 1983; Skurdal and Qvenild, 1986), Pacifastacus leniusculus, Dana (Abrahamsson, 1971; Mason, 1978) and for natural populations of Astacus leptodactylus Esch. (Koksal, 1984, 1988; Stucki, 1999; Harlioglu and Turkgulu, 2000, Harlioglu et al., 2004). For Bulgaria a limited data on egg size and their number and also the length of the examined individuals has been published for a couple of samples of Astacus leptodactylus and Astacus astacus (Bulgurkov, 1961). A complete characteristic of the dependence of the size of pleopodal eggs and basic exterior body parameters such as weight and length of the body, length and width of the carapace, as far as a cultivated population is concerned, has been executed (Hubenova et al., 2004). The objectives of the present investigation were the examination of pleopodal fecundity (number of pleopodal eggs) and the dimensions of the pleopodal eggs (weight and diameter) and their correlation with the following exterior parameters: body weight and length, and length and width of carapace, as well as the comparison of the established parameters for two groups of crayfish Astacus leptodactylus Esch.: the cultivated population in the Institute of Fishery and Aquaculture, Branch of Freshwater Fisheries, Plovdiv and the natural population of Piasachnik dame-lake. Materials and Methods The investigation was carried out in May 2001 with 71 female crayfish with pleopodal eggs, reared in carp ponds. The
210 exterior measurements of the body length, the length and width of carapace and abdomen were carried out following a scheme proposed by Skvorcov (1914). By using a tweezers 10 pleopodal eggs were removed from each crayfish, the diameter (with binocular microscope with an allowance of 0.01 mm) and the weight in fresh status (with analytical scales with an allowance of 0.0001 g) were individually measured. The values obtained were compared in 2002 with the respective values of these parameters for 60 female crayfish from the natural population of Piasachnik dame-lake, measured by the same parameters. The data obtained were analyzed by means of statistical software for Windows XP. Results The absolute values of the exterior parameters of the sexually mature female crayfish - body weight and length, and width and length of carapace are shown in Table 1. The body weight of the females from the cultivated population varies from 12.24 to 93.15 g, the average being 33.48 g. This P. Vasileva, A. Zaikov and T. Hubenova parameter indicates a high degree of variation 38.42%, which is being determined by the different weights of the individuals of the examined sample. The body weight of females from the natural population ranges from 26.57 tо 123.39 g, the average being 48.78 g, which analogically shows a high degree of variation 34.21%. The established average number of pleopodal eggs of the Narrow-clawed crayfish from the pond population is 162.7+104.1. The females from the natural population have an average number of 200.8+89.2 pleopodal eggs. Significant differences between the two groups as to this parameter were established. Таble 2 shows the linear equations and correlation coefficients describing the relationship between the number of the pleopodal eggs and basic exterior experiments in the two investigated populations. A considerable correlation between the analyzed results and the pleopodal fecundity (0.6184< r <0.7033) has been established for both groups of Narrow-clawed crayfish. From the individual measurements of the diameter and weight of 710 eggs it has been established that the average egg Table 1 Avarage values of the parameters total wet weight, total length, carapace length and carapace width in various experimental groups Parameter population population n=71 n=60 x+sd Cv, % lim x+sd Cv, % lim Total wet weight, BW,g 33.48+12.86 38.42 12.24-93.1548.78+16.69 34.21 26.57-123.39 Total length, TL, cm 10.71+1.36 12.72 7.7-15.3 12.1+1.3 10.72 10.0-16.7 Carapace length, CL, cm 5.29+0.71 13.47 3.9-7.7 5.9+0.65 10.95 4.9-8.2 Carapace width, CW, cm 2.69+0.36 13.30 1.9-3.8 3.08+0.31 10.12 2.4-4.0
Investigation on Fecundity and Egg Size in Cultured and Natural Crayfish Population... 211 Table 2 The linear regression and correlation coefficient between fecundity (pleopodal eggs, N) and total length (TL), carapace length (CL), carapace width (CW) and body weight (BW) for the two different populations For the cultivated population For the natural population N=47.88TL-350.13, r=0.6267 N=48.355TL-384.12, r=0.7033 N=92.94CL-328.6, r=0.6355 N=96.069CL-365.67, r=0.696 N=180.07CW-321.43, r=0.6184 N=183.47CW-364.88, r=0.642 N=5.228BW-12.297, r=0.646 N=3.54BW-28.108, r=0.6627 weight and diameter for the cultivated population are 0.0136 g and 2.96 mm, respectively; values for the natural population are 0.0124 g and 2.75 mm, respectively (Таble 3). The linear equations describing the relationship between the weight and diameter of the pleopodal eggs and basic exterior body parameters are presented in Table 4. It has been found out that there exists a low correlation between the exterior parameters and the eggs size. The value of the correlation coefficient (r) varies from 0.0883 to 0.2724 for the cultivated and from 0.1131 to 0.2121 for the natural population. Aiming to eliminate the influence of the body weight on the features characterizing the fecundity and the dimensions of the eggs, the individuals from the both populations were divided into four weight groups (Таbles 5-8). The percentage distribution of the females in the weight groups is different for the two examined populations. As far as the cultivated population is distributed, the individuals from the weight group 30-50 g (54.9%) and those from the weight group up to 30 g (39.5%) have the highest percentage. As far as the natural population is distributed, the group with body weight 30-50 g constitute 58.3% from the investigated sample, whereas the next group, the weight of which varies from 50 to 70 g is presented with 30% from the total number of crayfish. Table 3 and diameter of pleopodal eggs in the two investigated groups of sexually mature female crayfish (n=number of the investigated eggs) Parameter of pleopodal eggs (EW, g) Diameter of pleopodal eggs (ED, mm) 0 0 x+sd Cv, % lim x+sd Cv, % lim 0.0136+0.017 12.66 0.0088-0.0202 0.0124+0.017 13.87 0.0082-0.0172 2.96+0.2 6.8 2.4-3.7 2.75+0.17 6.05 2.2-3.4
212 P. Vasileva, A. Zaikov and T. Hubenova Table 4 Linear regressions and correlation coefficients between the egg size (egg weight, EW and egg diameter, ED) of the pleopodal eggs and the total length (TL), carapace length (CL), carapace width (CW) and body wet weight (BW) for the two investigated populations For the cultivated population EW=0.1783TL+11.723, r=0.1568 EW=0.415CL+11.438, r=0.1908 EW=0.7CW+11.75, r=0.1616 EW=0.01BW+13.28, r=0.0883 ED=0.0218TL+2.72, r=0.2133 ED=0.051CL+2.69, r=0.2623 ED=0.098CW+2.69, r=0.2508 ED=0.001BW+2.91, r=0.117 Significant differences in the exterior of the body (body weight and length, and carapace length and width, Tables 5, 6, 9, 10) between the individuals from the both populations by weight groups were established for particular parameters and only in some of the groups. Таble 11 shows the number of pleopodal eggs of the investigated populations by weight groups. As far as the pleopodal fecundity is concerned significant differences between separate weight groups have not been found out. In comparison with the lack of significant differences in the exterior and fecundity between crayfish from the both populations, the pleopodal eggs size (weight and diameter) for each weight group shows significantly higher values in the cultivated population compared to the natural one (Тable 12). The average diameter of the pleopodal eggs for the cultivated population is 2.96 mm, the smallest and biggest eggs being 2.4 and 3.7 mm, respectively. As far as the natural population is concerned the average diameter of the eggs For the natural population EW=0.2403TL+9.455, r=0.1962 EW=0.5092CL+9.36, r=0.2071 EW=0.9056CW+9.569, r=0.178 EW=0.0189BW+11.441, r=0.1985 ED=0.0142TL+2.575, r=0.1575 ED=0.03CL+2.57, r=0.1688 ED=0.06CW+2.57, r=0.1568 ED=0.001BW+2.7, r=0.1386 is 2.75 mm, the boundary values being 2.2 and 3.4 mm (Таble 3). The established data on the egg size of the cultivated population are higher than the results obtained from Stucki (1999) for two Swiss lakes populations of Astacus leptodactylus Esch. (egg diameter 2.77 and 2.76 mm, ranging from 2.34 to 3.33 mm); higher than the data obtained by Harlioglu and Turkgulu (2000) for the Narrow-clawed crayfish population from Keban reservoir (egg diameter 2.59 mm) and higher than the values registered by Koksal (1984) for a natural population of Astacus leptodactylus salinus (egg diameter from 2.21 to 2.67 mm). The average values established by us for the egg diameter from the natural population (2.75 mm) are very close to the ones registered by Stucki (1999) for the natural populations in both Swiss lakes and are higher that the ones established by Koksal (1984) and Harlioglu and Turkgulu (2000) for natural populations in Turky. The data obtained once again supports the dependence established by other au-
Investigation on Fecundity and Egg Size in Cultured and Natural Crayfish Population... 213 Tables 5-8 Average values of the parameters body weight, total length, carapace length and carapace width for the various weight groups of Astacus leptodactylus (n=number of the individuals) Таble 5 group n x+sd Cv, % n x+sd Cv, % up to 30 g 28 22.93+1.07 24.16 2 26.83+0.36 1.34 30-50 g 39 37.35+0.79 13.01 35 39.5+0.84 12.46 50-70 g 2 56.51+6.65 11.76 18 58.31+1.32 9.29 over 70 g 2 82.62+14.9 18.03 5 88.19+10.4 23.59 Таble 6 group n x+sd Cv, % n x+sd Cv, % up to 30 g 28 9.49+0.17 9.2 2 10.1+0.14 1.4 30-50 g 39 11.25+0.08 4.56 35 11.34+0.09 4.45 50-70 g 2 13.2+0.71 5.36 18 13.02+0.1 3.29 over 70 g 2 14.75+0.78 5.27 5 14.9+0.54 7.31 Таble 7 group n x+sd Cv, % n x+sd Cv, % up to 30 g 28 4.67+0.09 9.86 2 5.0+0.14 2.83 30-50 g 39 5.56+0.05 6.06 35 5.52+0.05 4.99 50-70 g 2 6.5+0.57 4.35 18 6.33+0.05 3.25 over 70 g 2 7.35+0.49 6.73 5 7.32+0.27 7.38 Таble 8 Body weight, BW, g Body length, TL, cm Carapace length, CL, cm Carapace width, CW, cm group n x+sd Cv, % n x+sd Cv, % up to 30 g 28 2.38+0.05 11.14 2 2.55+0.21 8.32 30-50 g 39 2.83+0.03 6.07 35 2.91+0.02 4.96 50-70 g 2 3.3+0.14 4.29 18 3.32+0.03 4.17 over 70 g 2 3.6+0.28 7.86 5 3.68+0.13 7.03
214 P. Vasileva, A. Zaikov and T. Hubenova Tables 9-10 Relative values of the parameters carapace length and carapace width for the various weight groups of Astacus leptodactylu (n=number of the investigated individuals) Table 9 group n x+sd Cv, % n x+sd Cv, % up to 30 g 28 49.18+0.27 2.82 2 49.5+0.71 1.43 30-50 g 39 49.4+0.22 2.74 35 48.68+0.14 1.71 50-70 g 2 49.26+0.5 1.01 18 48.19+0.18 0.86 over 70 g 2 49.81+0.73 1.46 5 49.13+0.3 1.24 Таble 10 group Carapace length, CL, % Carapace width, CW, % n x+sd Cv, % n x+sd Cv, % up to 30 g 28 25.08+0.2 4.11 2 25.24+1.75 6.92 30-50 g 39 25.15+0.14 3.43 35 25.66+0.1 2.19 50-70 g 2 25.01+0.27 1.07 18 25.49+0.22 3.6 over 70 g 2 24.39+0.63 2.59 5 24.77+1.03 8.29 Таble 11 Average number of pleopodal eggs of the populations by weight groups (n=number of individuals) Crayfish from ultivated Body weight n x+sd Cv, % n x+sd Cv, % up to 30 g 28 104+64.68 62.2 2 123+67.88 55.19 30-50 g 39 184.9+91.97 49.74 35 155.66+48.65 31.26 50-70 g 2 304.5+115.26 37.85 18 256.72+86.51 33.7 over 70 g 2 410.5+180.31 43.93 5 346.8+51.04 14.72 thors that the trophic level of the habitat (in our case the better trophic conditions in Piasachnik dame-lake and the supplemental feeding with sunflower groats and ground wheat in the pond) exerts a positive impact on the egg size (Koksal,1988; Holdich and Lowery, 1988). According to Koksal (1988) and Stucki (1999) larger female crayfish have bigger eggs, but Koksal (1984) points out that their size variation can be considerable. The data obtained in this study showed a significant increase of the weight and diameter of the pleopodal eggs for every weight
Investigation on Fecundity and Egg Size in Cultured and Natural Crayfish Population... 215 Table 12 and diameter of the pleopodal eggs of the both investigated populations by weight groups (n=number of the investigated eggs) their investigation the authors state that there does not exist any dependence between the size of the female crayfish and the eggs size. Similar conclusion has been also drawn by Ivanova and Vassilenko (1987) while examining the correlation between the egg size and the body length for the species Astacus leptodactylus. This is also true for investigations by Abrahamsson (1971), Lahti and Lindqvist (1983), Skurdal and Qvenild (1986) as regard the Noble crayfish Astacus astacus. On the basis of the data obtained in our investigation it can not be stated that small female crayfish have smaller egg size and vice versa, which is in conformity with Cukerzis s standpoint (1986 ) on Astacus astacus as well. For the examined group of individuals from the cultivated population the small- Body 0 0 n x+sd Cv, % n x+sd Cv, % t-test up to 30 g 280 0.0132+0.11 13.56 20 0.0099+0.12 5.09 *** 30-50 g 390 0.014+0.08 10.86 350 0.0119+0.08 12.48 *** 50-70 g 20 0.0151+0.36 10.5 180 0.0132+0.13 12.86 *** Over 70 g 20 0.0112+0.34 13.4 50 0.0139+0.13 6.66 *** Diameter of the pleopodal eggs, ЕD, mm Body of the pleopodal eggs, ЕW, g 0 0 n x+sd Cv, % n x+sd Cv, % t-test up to 30 g 280 2.92+0.01 6.43 20 2.58+0.02 3.69 *** 30-50 g 390 2.99+0.01 6.86 350 2.72+0.01 5.29 *** 50-70 g 20 3.05+0.03 4.32 180 2.79+0.01 6.15 *** Over 70 g 20 2.76+0.03 4.48 50 2.86+0.02 4.48 *** group. This is also in accordance with the results from Koksal (1988) and Stucki (1999) about the correlation between the body weight of Narrow-clawed crayfish and the egg size. Such positive correlation between eggs size and carapace size were also found out by Mason (1978) for the Signal crayfish Pacifastacus leniusculus. The lineal equations showing the relationship between some exterior parameters and the size of the pleopodal eggs indicate a low positive correlation. The values of the correlation coefficient (r) are in line with the data established by Harlioglu and Turkgulu (2000). The correlation coefficient (r) between the eggs diameter and the carapace length (CL, cm) was 0.2646, while the one between the egg weight and carapace length was 0.1414 (Harlioglu and Turkgulu, 2000). In
216 est egg diameter (2.4 mm) was registered in the crayfish with body weight of 14.82 g and a total length of 8.2 cm, while the biggest diameter (3.7 mm) was established in crayfish with a body weight of 33.74 g and a total length of 11 cm. On the other hand the smallest examined crayfish weighing 12.24 g and with a total length of 7.7 cm had a diameter and weight of pleopodal eggs from 2.7 to 2.9 mm and from 0.0117 to 0.0132 g, respectively. The eggs of the biggest crayfish weighing 94.46 g and with a total length of 15.4 cm have a diameter and weight from 2.8 to 3.0 mm and from 0.0119 to 0.0142 g, respectively. As with regard to the examined group of individuals from the natural population, the smallest diameter of the eggs (2.2 mm) was registered in crayfish weighing 42.6 g and with a total length of 11.4 cm, while the biggest diameter (3.4 mm) was registered in crayfish weighing 60.22 g and with a total length of 13.3 cm. The smallest examined crayfish with a body weight of 26.57 g and a total length of 10 cm had an egg diameter and weight from 2.5 tо 2.7 mm and from 0.0092 tо 0.0106 g, respectively. The biggest animals weighing 123.39 g and with a total length of 16.7 cm have eggs with a diameter and weight from 2.7 tо 3.1 mm and from 0.0123 tо 0.016 g, respectively. Conclusions The average pleopodal fecundity of Narrow-clawed crayfish in the pondreared population was 162.7+104.1 pleopodal eggs. The individuals from the natural population have an average pleopodal fecundity of 200.8+89.2 pleopodal eggs. Significant differences between the two groups have been found out in terms of this parameter. The diameter and weight of the pleopodal eggs for the cultivated population were 0.0136 g and 2.96 mm, respectively, whereas the values of these parameters for the natural population are 0.0124 g and 2.75 mm, respectively. Significantly higher are the corresponding values in the cultivated population both for the entire analyzed sample, and for the different weight groups as well. A considerable correlation between the number of the pleopodal eggs and the weight and length of the crayfish body occurred as well as for the length and width of carapace. A low correlation between the weight and diameter of the pleopodal eggs and the some exterior parameters of the body was obtains. The variation in the weight and diameter of the pleopodal eggs for the examined group of individuals was higher compared to the variation of these features for each particular individual. References P. Vasileva, A. Zaikov and T. Hubenova Abrahamsson, S. A., 1971. Density, growth and reproduction in populations of Astacus astacus and Pacifastacus leniusculus in an isolated pond. Oikos, 22:373-380. Abrahamsson, S. A., 1972. Fecundity and growth of some populations of Astacus astacus Linne in Sweden. Inst. Freshwater Res. Drottningholm, Rep. 52:23-37. Alekhnovich, A. and V. Kulesh, 1996. Comparative analysis of reproduction of Narrow-clawed crayfish, Astacus leptodactylus in its eastern area. Freshwater Crayfish, 11:339-347 Bulgurkov, K., 1961. Systematik, Biologie und zoogeographische Verbreitung der Suesswaterkrebse der Familien Astacidae und Potamonidae in Bulgarien. Procc. Zool. Ins. BAS, 10:165-190.
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