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Chromosomal description of the rodent genera Oecomys and Nectomys from Brazil

100%

Andrades-Miranda J., Oliveira L. F. B., Zanchin N. I. T., Mattevi M. S.

Acta Theriologica

2001

tom 46

nr 3

We analysed karyotypes of five taxa of the rodent genera Oecomys and Nectomys, trapped in 14 localities in an area ranging from 8° to 29°S on Brazilian territory. Oecomys cf. concolor, collected in the Amazon and in two localities of the Cerrado biome, showed a 2n = 60 karyotype constituted by a pair of large subtelocentric chromosomes, a small metacentric pair and 27 acrocentric pairs. The X chromosome was a large submetacentric and a subtelo-submetacentric, the morphology of the latter showing variable C-banding patterns. In all three localities the Y chromosome was a medium size heterochromatic acrocentric. Two individuals from the Cerrado had a heterochromatic acrocentric B-chromosome. Oecomys cf. bicolor presented two cytotypes, 2n = 80 in the specimens from the Cerrado biome and 2n = 82 in individuals trapped in the Amazon. The 2n = 80 cytotype 1 showed a large subtelocentric, 22 biarmed pairs (medium to small) and 16 acrocentric autosomal pairs. The karyotype of the 2n = 82 cytotype 2 is constituted by 15 biarmed chromosomes (median to small) and 25 acrocentric pairs with heterochromatic blocks at pericentromeric regions. The sexual pairs were the same (large submetacentric X and median acrocentric Y) in both cytotypes. In O. cf. concolor and in both cytotypes of O. cf. bicolor the nucleolar organizer regions were observed in 1-3 pairs, located in the short arms. Nectomys genus presented two cytotypes, 2n = 52-55 (N. rattus, with 0-3 biarmed heterochromatic accessory chromosomes) and 2n = 56-59 (N. squamipes, bearing 0-3 biarmed, hetero- chromatic, B-chromosomes). These 2 cytotypes occupy disjunct regions of South America, with overlapping areas in the Brazilian states of Pernambuco, Bahia, and Mato Grosso do Sul.

Nests and nesting sites of Brazilian forest rodents [Nectomys aquamipes and Oryzomys intermedius as revealed by a spool-and-line device

100%

Briani D. C., Vieira E. M., Vieira M. V.

Acta Theriologica

2001

tom 46

nr 3

Patterns of nest construction and nest site selection of two murid rodents of the Brazilian Atlantic rainforest were described. The animals were captured in an area of about 1.5 ha of primary forest, marked, equipped with a spool-and-line device and released at the capture point. The next day we followed the thread to find their nests. In total 11 nests of Nectomys squamipes (Brants, 1827) and 13 of Oryzomys intermedius (Leche, 1886) were found. They were all egg-shaped, about 15 cm long and 10 cm wide, without any apparent entrance and consisted of dry leaves and grass. The two species differed in the selection of nest sites. The nests of N. squamipes were close to streams and built inside decomposed fallen logs or using natural entrances between the soil and tangled roots or rocky crevices. Nests of O. intermedius were built under or inside fallen logs and inside aerial root systems of palms. The spool-and-line technique used here is useful to provide detailed information on several aspects of the ecology and natural history of small mammals.

Ograniczanie wyników

2 Acta Theriologica

1 Andrades-Miranda J.

1 Briani D. C.

1 Mattevi M. S.

1 Oliveira L. F. B.

1 Vieira E. M.

1 Vieira M. V.

1 Zanchin N. I. T.

2 2001

Wyniki wyszukiwania

Chromosomal description of the rodent genera Oecomys and Nectomys from Brazil

Nests and nesting sites of Brazilian forest rodents [Nectomys aquamipes and Oryzomys intermedius as revealed by a spool-and-line device