Abstract
Two species of Cassidinae have been chromosomally analyzed, Cassida humeralis Kraatz, 1874 from France, with 2n = 18, 8 + Xyp meioformula and Anacassis fuscata (Klug, 1829) from Uruguay, with 2n = 30, 14 + Xy meioformula. The karyotype of the former is composed of similar meta/submetacentric autosomes, a small X-chromosome and a tiny y-chromosome, as many other Cassida and tribe Cassidini species, whereas that of the latter has four pairs of acro/telocentric autosomes at least and the remaining meta/submetacentrics including the X-chromosome and a tiny y-chromosome, which points out to its probable apomorphic origin by centric fissions, as found in some other species of the tribe Mesomphaliini.
Highlights
The leaf beetles of subfamily Cassidinae are a very large group with some 6,000 species distributed in 43 tribes (Chaboo 2007)
Cassida humeralis: 1 spermatogonial metaphase with 2n = 18 meta/submetacentric chromosomes, the small X-chromosome is arrowheaded and the tiny y-chromosome pointed by an arrow 2 meiotic diakinesis with a 8 + Xyp meioformula, the Xyp is arrowheaded 3 meiotic metaphase II of X-chromosome class with nine chromosomes 4 meiotic metaphase II of y-chromosome class with nine chromosomes
The range of diploid numbers in the tribe Cassidini is quite large from 2n = 16 in Glyphocassis trilineata (Hope, 1831) to 2n = 42 in Agroiconota inedita (Boheman, 1855), but all out of one checked species in this tribe show the Xyp sex chromosome system in males, a few of them are polymorphic for an additional yp chromosome (De Julio et al 2010)
Summary
The leaf beetles of subfamily Cassidinae are a very large group with some 6,000 species distributed in 43 tribes (Chaboo 2007). The sex-chromosome system in males is the “parachute type” Xyp, as Copyright Eduard Petitpierre. Found in nearly 95% of Cassidinae (De Julio et al 2010) and in most beetles of the suborder Polyphaga (Smith and Virkki 1978). The present paper is a small contribution to the cytogenetics of Cassidinae and a brief discussion on its chromosomal evolution
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