A putative RA-like region in the brain of the scale-backed antbird, Willisornis poecilinotus (Furnariides, Suboscines, Passeriformes, Thamnophilidae)

Jamily L.R De Lima,Fabricio A Soares,Alexandre Aleixo,Ana C.S Remedios,Gregory Thom,Morgan Wirthlin,Claudio V Mello,Maria Paula C Schneider,Patricia N Schneider

doi:10.1590/s1415-475738320150010

Abstract

The memorization and production of song in songbirds share important parallels with the process of speech acquisition in humans. In songbirds, these processes are dependent on a group of specialized telencephalic nuclei known as the song system: HVC (used as a proper name), RA (robust nucleus of arcopallium), LMAN (lateral magnocellular nucleus of the nidopallium) and striatal Area X. A recent study suggested that the arcopallium of the Sayornis phoebe, a non vocal learner suboscine species, contains a nucleus with some properties similar to those of songbird RA, suggesting that the song system may have been present in the last common ancestor of these groups. Here we report morphological and gene expression evidence that a region with some properties similar to RA is present in another suboscine, the Amazonian endemic Willisornis poecilinotus. Specifically, a discrete domain with a distinct Nissl staining pattern and that expresses the RA marker RGS4 was found in the arcopallium where the oscine RA is localized. Our findings, combined with the previous report on the S. phoebe, suggest that an arcopallial region with some RA-like properties was present in the ancestor of both Suboscines infraorders Tyranni and Furnarii, and is possibly an ancestral feature of Passeriformes.

Highlights

Vocal learning is a rare trait present in three clades of birds: hummingbirds (Trochiliformes), parrots (Psitaciformes) and songbirds (Oscines, Passeriformes) (Zigmond et al, 1973, Jarvis et al, 2000, Wilbrecht and Nottebohm, 2003, Arriaga et al, 2012)
To establish whether similar nuclei are present in the antbird W. poecilinotus, we first examined Nissl-stained parasagital brain sections of adult male Pale-breasted Thrush, Turdus leucomelas (Turdidae), a vocal-learning oscine species, thereby establishing a basis for comparison in a similar-sized oscine brain
To characterize the forebrain of W. poecilinotus, we studied the general organization of the brain utilizing Nissl-stained parasagittal sections from adult males

Summary

Introduction

Vocal learning is a rare trait present in three clades of birds: hummingbirds (Trochiliformes), parrots (Psitaciformes) and songbirds (Oscines, Passeriformes) (Zigmond et al, 1973, Jarvis et al, 2000, Wilbrecht and Nottebohm, 2003, Arriaga et al, 2012). The anterior pathway resembles mammalian cortico-basal ganglia-thalamo cortical loops, and is more directly involved in vocal learning and plasticity. It includes two nuclei located rostrally in the telencephalon: Area X of the striatum (Area X) and the lateral magnocellular nucleus of the anterior nidopallium (LMAN) (Jarvis, 2004, Prather, 2013) (Figure 1A). The Passeriformes are composed of two suborders: oscines (songbirds), with the largest number of species, and suboscines. The latter are further divided into two main infraorders: Tyranni and Furnarii. While traditionally viewed as vocal non-learners (Brenowitz et al, 1991, Touchton et al, 2014), there is evidence that some suboscines, espe-

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Discussion