de Oliveira Edivaldo H C, Gomes Anderson J B, Costa Alexandra F, Emin-Lima Renata, Bonvicino Cibele R, Viana Maria C, Reis Laura M A, Vidal Marcelo D, Cavalcanti Mirella V G, Attademo Fernanda L N, Luna Fábia O, Siciliano Salvatore
ICEN, Universidade Federal do Pará, Belém 66075-110, PA, Brazil.
SEAMB, Instituto Evandro Chagas, Ananindeua 67030-000, PA, Brazil.
Life (Basel). 2022 Apr 20;12(5):616. doi: 10.3390/life12050616.
Two species of manatees are found in Northern Brazil-the Antillean manatee (), which is found along the coast from Florida to Northeastern Brazil, and the Amazonian manatee (), endemic to the Amazon drainage basin. These species show a sympatric distribution in the region of the Marajó Archipelago, an estuarine area surrounding the Amazon River mouth. There is evidence of the occurrence of interspecific hybrids in this area, based on mitochondrial DNA analyses, although the use of nuclear markers has not corroborated this proposal. Considering that these species show very distinct karyotypes, despite being closely related (2 = 48 in and 2 = 56 in ), hybrids would present distinct chromosome numbers. Based on this, we conducted cytogenetic analyses using classic and molecular techniques in three calves found stranded in the Marajó Island and Amapá coast. The results showed that one of them, morphologically classified as , presented the correspondent karyotype, with 2 = 56. However, the other two, which were phenotypically similar to , showed 2 = 49. Despite the same diploid number, their G-banding patterns revealed some differences. The results of the distribution of some microsatellite sequences have also confirmed the heterozygosity of some chromosomal pairs in these two individuals. These results are the first indubitable confirmation of the occurrence of natural hybrids between and , and also brings about some issues concerning the viability of hybrids, considering that these two individuals do not correspond to an F1 hybrid, but instead, both presented a possible F2 karyotype.
在巴西北部发现了两种海牛——安的列斯海牛（），分布于从佛罗里达到巴西东北部的沿海地区，以及亚马逊海牛（），它是亚马逊河流域特有的物种。这两个物种在马拉若群岛地区呈现同域分布，马拉若群岛是围绕亚马逊河河口的一个河口区域。基于线粒体DNA分析，有证据表明该地区存在种间杂交种，尽管使用核标记并未证实这一说法。考虑到这两个物种尽管亲缘关系密切（安的列斯海牛2n = 48，亚马逊海牛2n = 56），但其核型却非常不同，杂交种可能会呈现出不同的染色体数目。基于此，我们对在马拉若岛和阿马帕海岸搁浅的三头幼崽使用经典和分子技术进行了细胞遗传学分析。结果显示，其中一头在形态上被归类为亚马逊海牛，具有相应的核型，2n = 56。然而，另外两头在表型上与安的列斯海牛相似，显示2n = 49。尽管二倍体数目相同，它们的G带模式显示出一些差异。一些微卫星序列分布的结果也证实了这两个个体中一些染色体对的杂合性。这些结果首次确凿地证实了安的列斯海牛和亚马逊海牛之间存在天然杂交种，同时也引发了一些关于杂交种生存能力的问题，因为这两个个体并非F1杂交种，而是都呈现出可能的F2核型。
