Department of Environmental Sciences, P,O,Box 65, FIN-00014, University of Helsinki, Helsinki, Finland.
BMC Evol Biol. 2010 Mar 30;10:86. doi: 10.1186/1471-2148-10-86.
Sloths are slow-moving arboreal mammals inhabiting tropical rainforests in Central and South America. The six living species of sloths are occasionally reported to display a greenish discoloration of their pelage. Trichophilus welckeri, a green algal species first described more than a century ago, is widely believed to discolor the animals fur and provide the sloth with effective camouflage. However, this phenomenon has not been explored in any detail and there is little evidence to substantiate this widely held opinion.
Here we investigate the genetic diversity of the eukaryotic community present in fur of all six extant species of sloth. Analysis of 71 sloth hair samples yielding 426 partial 18S rRNA gene sequences demonstrates a diverse eukaryotic microbial assemblage. Phylogenetic analysis reveals that sloth fur hosts a number of green algal species and suggests that acquisition of these organisms from the surrounding rainforest plays an important role in the discoloration of sloth fur. However, an alga corresponding to the morphological description of Trichophilus welckeri was found to be frequent and abundant on sloth fur. Phylogenetic analysis demonstrated the retention of this alga on the fur of sloths independent of geographic location.
These results demonstrate a unique diverse microbial eukaryotic community in the fur of sloths from Central and South America. Our analysis streghtens the case for symbiosis between sloths and Trichophilus welckeri.
树懒是行动缓慢的树栖哺乳动物,栖息在中美洲和南美洲的热带雨林中。六种现存的树懒偶尔会被报道其皮毛呈现出绿色变色。一百多年前首次描述的绿藻物种 Trichophilus welckeri 被广泛认为会使动物的皮毛变色,并为树懒提供有效的伪装。然而,这种现象并没有被详细探讨,也没有多少证据可以证实这种普遍的观点。
在这里,我们调查了现存六种树懒所有物种皮毛中真核生物群落的遗传多样性。对 71 个树懒毛发样本进行分析,共获得 426 个部分 18S rRNA 基因序列,表明存在多样化的真核微生物组合。系统发育分析表明,树懒皮毛上有许多绿藻物种,表明从周围雨林中获得这些生物在树懒皮毛变色中起着重要作用。然而,在树懒的皮毛上发现了一种与 Trichophilus welckeri 的形态描述相对应的藻类,而且在树懒的皮毛上非常频繁且丰富。系统发育分析表明,这种藻类独立于地理位置保留在树懒的皮毛上。
这些结果表明,中美洲和南美洲的树懒皮毛中存在独特多样的微生物真核生物群落。我们的分析加强了树懒与 Trichophilus welckeri 之间共生关系的案例。