Genome size (or C-value) in benthic polychaetes was studied from both experimental data and literature. Nuclear DNA content variation was analysed as related to both phylogenetic relationships of various families, general life habit of the species (interstitial vs macrobenthic), diploid chromosome number (2n), and mean body size (length). Experimental data on genome size were obtained for 43 lower taxa (genera and species) by means of microdensitometric analysis of the amount of Fuelgen-stained haploid DNA in interphase nuclei. These data, added to those available in the literature (36 taxa studied by Conner et al., 1972) gave a total of 79 taxa (genera and species), representing 30 families and 14 orders. Twenty-one of the species studied belonged exclusively to interstitial (=meiofaunal) families or genera. In the taxa examined genome size ranged from 0.07 to 1.16 pg in the interstitial species, and from 0.4 to 7.2 pg in the macrobenthic ones. This wide range of variation in genome size, of two orders of magnitude, also includes the lowest genome size currently documented for Metazoa. The fact that all the meiofaunal species had lower genome size, regardless of their systematic position, suggests that low genome size is correlated with the interstitial life habit. Comparisons with literature data on nuclear DNA content in other meiofaunal invertebrate groups support this hypothesis. Genome size showed a significant positive correlation (r=0.38; df=69; P<0.01) with mean body length, but was unrelated to diploid chromosome number (r=0.28; df=18; ns). However, regardless of their C-values, interstitial taxa showed comparatively lower chromosome numbers (2n between 6 and 18) than macrobenthic taxa (2n between 18 and 72). This fact may indicate a tendency to reduction in recombination potential in meiofaunal forms.
Variation in genome size in benthic polychaetes: Systematic and ecological relationships
RAMELLA GAL, Liliana;SELLA, Gabriella;E. Aldieri
1997-01-01
Abstract
Genome size (or C-value) in benthic polychaetes was studied from both experimental data and literature. Nuclear DNA content variation was analysed as related to both phylogenetic relationships of various families, general life habit of the species (interstitial vs macrobenthic), diploid chromosome number (2n), and mean body size (length). Experimental data on genome size were obtained for 43 lower taxa (genera and species) by means of microdensitometric analysis of the amount of Fuelgen-stained haploid DNA in interphase nuclei. These data, added to those available in the literature (36 taxa studied by Conner et al., 1972) gave a total of 79 taxa (genera and species), representing 30 families and 14 orders. Twenty-one of the species studied belonged exclusively to interstitial (=meiofaunal) families or genera. In the taxa examined genome size ranged from 0.07 to 1.16 pg in the interstitial species, and from 0.4 to 7.2 pg in the macrobenthic ones. This wide range of variation in genome size, of two orders of magnitude, also includes the lowest genome size currently documented for Metazoa. The fact that all the meiofaunal species had lower genome size, regardless of their systematic position, suggests that low genome size is correlated with the interstitial life habit. Comparisons with literature data on nuclear DNA content in other meiofaunal invertebrate groups support this hypothesis. Genome size showed a significant positive correlation (r=0.38; df=69; P<0.01) with mean body length, but was unrelated to diploid chromosome number (r=0.28; df=18; ns). However, regardless of their C-values, interstitial taxa showed comparatively lower chromosome numbers (2n between 6 and 18) than macrobenthic taxa (2n between 18 and 72). This fact may indicate a tendency to reduction in recombination potential in meiofaunal forms.
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