A Relationship between the Characteristics of the Oval Nucleus of the Mesopallium and Parrot Vocal Response to Playback

Correlations between differences in animal behavior and brain structures have been used to infer function of those structures. Brain region size has especially been suggested to be important for an animal’s behavioral capability, controlled by specific brain regions. The oval nucleus of the mesopallium (MO) is part of the anterior forebrain vocal learning pathway in the parrot brain. Here, we compare brain volume and total number of neurons in MO of three parrot species (the peach-fronted conure, <i>Eupsittula aurea</i>, the peach-faced lovebird, <i>Agapornis roseicollis</i>, and the budgerigar, <i>Melopsittacus undulatus</i>), relating the total neuron numbers with the vocal response to playbacks of each species. We find that individuals with the highest number of neurons in MO had the shortest vocal latency. The peach-fronted conures showed the shortest vocal latency and largest number of MO neurons, the peach-faced lovebird had intermediary levels of both, and the budgerigar had the longest latency and least number of neurons. These findings indicate the MO nucleus as one candidate region that may be part of what controls the vocal capacity of parrots.

Histological characterization of cellular types during Scinax fuscovarius oogenesis (Lutz) (Anura, Hylidae)

This paper describes morphological characteristics of the ovarian germinative cells of the Scinax fuscovarius (Lutz, 1925). The ovary is organized in primordial germinative cells (oogonia) and follicular structures (ovarian follicle) - oocytes surrounded by follicular cells. Oogonia: their nests are peripherically localized, containing cells with large and oval nucleus. Oocytes I: basophilic cytoplasm; the spherical nucleus presents few nucleoli, one or two; the follicular cells (one tenuous layer) surround these previtellogenic cells. Oocytes II: the cell is larger and the cytoplasm becomes more basophilic; the nucleus presents few nucleoli and contains many chromosomes in the periphery (beginning the perinucleolar stage). Oocytes III: the cytoplasm acquires an intense acidophilia; the peripherical region of cytoplasm is filled with yolk and the internal region has no yolk at all; pigment synthesis begins; the follicular envelope presents three tenuous layers: an inner acellular (vitelline envelope) and two cellular layers (follicle cells). Oocytes IV: a characteristic of this stage is the differentiation between the animal and the vegetal poles; the nucleus in the animal hemisphere and the pigments give the oocyte a color dark brown; the vitellogenesis is intense and the yolk occupies the whole cytoplasm.