Karyology of the Atlantic forest rodent Juliomys (Cricetidae): a new karyotype from southern Brazil

Abstract

Juliomys is a small rodent from the family Cricetidae which inhabits the Atlantic forest and forests from Argentina to eastern Brazil. The three species recognized so far have different karyotypes. In this paper, we describe a new karyotype with 2n = 32, FN = 48 found in Juliomys specimens from a high-altitude area in the Atlantic forest of southern Brazil. The karyotype was analyzed after G-and C-banding and silver staining of the nucleolus organizer regions (Ag-NOR) and its G-banding patterns were compared with those of the newly described species Juliomys ossitenuis (2n = 20, FN = 36). The 2n = 32 karyomorph presented peculiar features and was very different from those of the other species of the genus: J. pictipes (2n = 36, FN = 34), J. rimofrons (2n = 20, FN = 34) and J. ossitenuis (2n = 20, FN = 36). Differences were mostly due to centric and tandem fusions, pericentric inversion and loss of heterochromatin. The karyotype represents a powerful tool to differentiate Juliomys species and our data suggest that the karyotype described herein belongs to a new species.

A New Allopatric Lineage of the Rodent <i>Deltamys</i> (Rodentia: Sigmodontinae) and the Chromosomal Evolution in <i>Deltamys kempi</i> and <i>Deltamys</i> sp.

“…(DSP7 and DSP19) and 1 acrocentric of D. kempi (DKE4). Tandem translocation poly- morphisms are considered to be strongly underdominant compared to other chromosomal rearrangements [see Navarro and Barton, 2003;Rieseberg and Livingstone, 2003], but are recurrent in closely related species of sigmodontine rodents belonging to the genera Akodon, Nectomys, Thaptomys, Sigmodon, Juliomys and Rhipidomys [Yonenaga-Yassuda et al, 1988;Silva and Yonenaga-Yassuda, 1998;Volobouev and Catzeflis, 2000;Ventura et al, 2004Ventura et al, , 2006Ventura et al, , 2009Paresque et al, 2009;Swier et al, 2009]. Both Deltamys forms lack the small metacentric pair, which constitutes a karyotypic characteristic that distinguishes Deltamys from its closely related genus Akodon [Fronza et al, 1981].…”

Small mammal community structure and microhabitat use in the austral boundary of the Atlantic Forest, Brazil

“…Unfortunately, it was not possible to identify the Juliomys specimen captured by us beyond genus. It is possible that it represents a new species, as suggested by PARESQUE et al (2009) for three individuals captured at Aparados da Serra National Park, Rio Grande do Sul. To our knowledge, our records represent the southernmost know distribution points for Juliomys sp.…”

“…It also provides the second record of Juliomys (González, 2000) (first recorded in Rio Grande do Sul by PARESQUE et al 2009) in the state. Unfortunately, it was not possible to identify the Juliomys specimen captured by us beyond genus.…”

First record of Juliomys ossitenuis Costa, Pavan, Leite &amp; Fagundes, 2007 (Rodentia, Sigmodontinae) in Paraná state, southern Brazil

“…However, the most reliable method of identifying species in the genus is via cytogenetics, since J. pictipes has a 2n = 36 and FNa = 34 karyotype (Bonvicino and Otazu 1999), J. rimofrons has 2n = 20 and FNa = 34 (Oliveira and Bonvicino 2002), and J. ossitenuis has 2n = 20 and FNa = 36 (Costa et al 2007). Futhermore, Paresque et al (2009) described a new karyotype with 2n = 32 and FNa = 48 in three specimens of Parque Nacional dos Aparados da Serra, Rio Grande do Sul state, a high-altitude area in the Atlantic forest of southern Brazil, with the possibility of a new species for the genus.…”