The present paper deals with the karyometric The present paper deals with the karyometric analysis of popula­tions of the planarian Dugesia benazzii Lepori collected in Corsica (Paradojo and Castello Pino strains) and Sardinia (Giocca strain). Paradojo specimens are diploid (2n = 16; n = 8), sexual and amphimictic; their chromosome complement consists of metacentric elements, whose length gradually decreases (in the seventh pair the centromere borders on a submetacentric position). The Castello Pino population is characterized by diploid and hyperdiploid individuals, that reproduce sexually or by fission. Its karyotype is similar to the one observed in Paradojo strain, except for the fact that, in most samples, the third pair is polymorphic. In diploid specimens, this latter pair consists of two heteromorphous elements, one metacentric and identical to that described in the preceding population and the other submetacentric, at the border of subtelocentric. This heterobrachial chromosome has never been observed in a homozygous condition. On the other hand, hyperdiploid specimens, that are characterized by a gradual increase in chromosome number (up to 30 32 elements), have never been observed with more than two submetacentrics. B-chromosomes are also present in both diploid and hyperdiploid individuals. Specimens from Giocca are tetraploid (or aneutetraploid), sexual and pseudogamous; the third quartet consists of four submefacentric (at the border of subtelocentric) chromosomes. These elements are similar to the heterobrachial chromosome observed in Castello Pino population. The origin (through a pericentric inversion) of the heterobrachial chromosome is put forward and the different conditions (homozygoty and heterozygoty) in Castello Pino and Giocca strains are discussed. A comparative analysis has also been carried out with the data collected by other Authors on Dugesia gonocephala s.s. and different species of the “D. gonocephala group”, which show similar karyological characteristics.

Karyometric analysis on populations of Dugesia benazzii (Turbellaria Tricladida) evidencing a chromosome polymorphism

DERI, PAOLO;PUCCINELLI, ILEANA
1987

Abstract

The present paper deals with the karyometric The present paper deals with the karyometric analysis of popula­tions of the planarian Dugesia benazzii Lepori collected in Corsica (Paradojo and Castello Pino strains) and Sardinia (Giocca strain). Paradojo specimens are diploid (2n = 16; n = 8), sexual and amphimictic; their chromosome complement consists of metacentric elements, whose length gradually decreases (in the seventh pair the centromere borders on a submetacentric position). The Castello Pino population is characterized by diploid and hyperdiploid individuals, that reproduce sexually or by fission. Its karyotype is similar to the one observed in Paradojo strain, except for the fact that, in most samples, the third pair is polymorphic. In diploid specimens, this latter pair consists of two heteromorphous elements, one metacentric and identical to that described in the preceding population and the other submetacentric, at the border of subtelocentric. This heterobrachial chromosome has never been observed in a homozygous condition. On the other hand, hyperdiploid specimens, that are characterized by a gradual increase in chromosome number (up to 30 32 elements), have never been observed with more than two submetacentrics. B-chromosomes are also present in both diploid and hyperdiploid individuals. Specimens from Giocca are tetraploid (or aneutetraploid), sexual and pseudogamous; the third quartet consists of four submefacentric (at the border of subtelocentric) chromosomes. These elements are similar to the heterobrachial chromosome observed in Castello Pino population. The origin (through a pericentric inversion) of the heterobrachial chromosome is put forward and the different conditions (homozygoty and heterozygoty) in Castello Pino and Giocca strains are discussed. A comparative analysis has also been carried out with the data collected by other Authors on Dugesia gonocephala s.s. and different species of the “D. gonocephala group”, which show similar karyological characteristics.
BENAZZI LENTATI, G; Deri, Paolo; Puccinelli, Ileana
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11568/12964
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