Reproductive Potentials of Diploid and Polyploidy Representatives of the Genus Сobitis (Cypriniformes, Cobitidae)

Abstract

Reproductive Potentials of Diploid and Polyploidy Representatives of the Genus Сobitis (Cypriniformes, Cobitidae). Mezhzherin, S. V., Salyy, T. V., Tsyba, A. A. -Comparison of reproductive parameters in severalCobitis forms with diff erent ploidy shows that the maximum fertility is found in diploid Cobitis, the triploids are less fertile and the tetraploids even less fecund. Th e latter reach maximum values of size and weight indicators but minimum number of eggs, the smallest size of the ovaries but the biggest eggs. Nevertheless, the combined reproductive potential of polyploid females is higher than of diploid spiny loaches with equal ratios of males to females in populations. Th e obvious reasons for the successful expansion of polyploid individuals of the spiny loaches are both their higher fertility at the population level and the changes in environmental conditions associated with the regulation of all major rivers in Ukraine in the 1960-1970s. Key words: Сobitis, fertility, polyploidy, invasion.Biological invasion -the spread of a "species" into an area that was not previously occupied by it -can have strong eff ect on ecosystem structure and function. A special case of invasion is the expansion of gynogenetic biotipes of spiny loaches of the genius Сobitis Linnaeus, 1758 from the Danube basin to river systems of Eastern Europe. It is known that most of European triploid and tetraploid spiny loaches of this genus (Bohlen, Rab, 2001;Bohlen et al., 2002;Janko et al., 2007;Mezhzherin, Pavlenko, 2010) occurred as a result of serial hybridization of Danube spiny loach С. elongatoides Băcescu, R. Mayer, 1969 that lives in Danube river system together with the spined loach C. taenia Linnaeus, 1758 and the С. tanaitica Băcescu, R. Mayer, 1969 (originating from Don River). Th e spined loach's range covers northern parts of European range of the genus Сobitis, while С. tanaitica occurs to the south, mostly downstream in rivers of the Azov-Black Sea basin, it is also found in all of the Danube (Bohlen, Rab, 2001;Bohlen et al., 2002;Janko et al., 2007). Th us the contact and hybridization between these species take place in Danube basin and bordering river systems of the North Sea rivers. C. elongatoides and C. tanaitica hybridize downstream (Mezhzherin, Pavlenko, 2007) and in middle reaches (Janko et al., 2007). In the case of hybrids of C. elongatoides × C. tanaitica backcrossing, triploid biotypes C. 2 elongatoides -tanaitica and C. elongatoides -2 tanaitica occur, while triploid biotypes C. elongatoides -tanaitica -taenia and C. elongatoides -tanaitica -2 taenia form upstream in the basin at the point of contact of C. elongatoides and С. taenia (Janko et al., 2007). Th erefore, it is quite correct to consider the Danube to be the place of origin of most European triploid biotypes of spined loaches, from where they have begun to invade other European river systems. Now unisexual polyploid spined loaches are common in Dniester basin, Southern Buh basin, Dnipro basin (Mezhzherin, Lisetskaya, 2004; Mehzhzherin, Pavl...

Genome Size Covaries More Positively with Propagule Size than Adult Size: New Insights into an Old Problem

“…According to this view, small genomes are associated with r-selected traits, such as high colonizing ability, rapid individual and population growth, early maturation, high reproductive output and short lives that are favored in unstable or ephemeral habitats and at low population densities, whereas large genomes are associated with K-selected traits, such as high competitive ability, slower individual and population growth, late maturation, low reproductive output and long lives that are favored in stable habitats and at high population densities. Although the theory of r- and K-selection may help explain some variation in genome sizes (e.g., the association of large genomes with relatively slow growth rates and long lives in some protists, plants and ectothermic animals (e.g., [ 7 , 8 , 15 , 19 , 59 , 60 , 113 , 151 , 177 , 186 , 189 , 195 , 243 , 255 , 293 , 300 , 308 , 309 , 310 , 311 , 312 ]; but not in endothermic vertebrates [ 95 ]), and the association of relatively large genomes with larger, but fewer reproductive propagules ([ 146 , 166 , 217 , 219 , 313 , 314 ]; Table A2 ), it cannot explain why genome size covaries with body size in some taxa, but not others (as observed in Table 1 ).…”

“…Changes in genome size may not only result from life-history changes, but also cause them [ 103 ]. Variation in genome size is often (but not always) associated with changes in various life-history traits, including not only propagule size and number, but also growth rate, duration of developmental periods, and age at sexual maturity ([ 8 , 9 , 10 , 11 , 15 , 16 , 19 , 32 , 48 , 57 , 58 , 59 , 60 , 80 , 97 , 103 , 109 , 113 , 177 , 186 , 189 , 192 , 195 , 255 , 293 , 294 , 308 , 309 , 310 , 311 , 312 , 313 , 314 , 317 ]; see also sources cited in Table 2 ; but for contradictory evidence, see [ 97 , 98 ]). Interspecific correlations between genome size and longevity have also been proposed [ 48 ], but questioned [ 9 , 97 ].…”

Reproductive advantage of parthenogenetic earthworm Aporrectodea trapezoides over the parental amphymictic species A. caliginosa (Oligochaeta, Lumbricidae)

“…Аналогичные исследования по индивидуальной плодовитости апомиктических и амфимиктических видов проводились у рыб [7,8]. Они показали, что число икринок в соответствии с возрастанием их размеров последовательно уменьшается в ряду диплоиды → триплоиды → тетраплоиды.…”