The organization of serotonergic fibers in the Pacific angelshark brain: Neuroanatomical and supercomputing analyses

Serotonergic axons (fibers) are a universal feature of all vertebrate brains. They form meshworks, typically quantified with regional density measurements, and appear to support neuroplasticity. The self-organization of this system remains poorly understood, partly because of the strong stochasticity of individual fiber trajectories. In an extension to our previous analyses of the mouse brain, serotonergic fibers were investigated in the brain of the Pacific angelshark (Squatina californica), a representative of a unique (ray-like) lineage of the squalomorph sharks. The fundamental cytoarchitecture of the angelshark brain was examined, including the expression of ionized calcium binding adaptor molecule 1 (Iba1, AIF-1), and serotonergic fibers were visualized with immunohistochemistry. In the forebrain, serotonergic fibers had the tendency to advance toward the dorsal pallium and also accumulated at significantly higher densities at pial borders. Next, a population of serotonergic fiber..., , # The organization of serotonergic fibers in the Pacific angelshark brain: Neuroanatomical and supercomputing analyses

Authors: Skirmantas Janusonis, Ralf Metzler, Thomas Vojta

---

### FILE: PacificAngelshark_CoronalSectionSet_Nissl.zip

This set of images is a series of coronal sections through a Pacific angelshark (*Squatina californica*) adult female brain. The specimen was collected in Santa Barbara County (California, USA) in September 2017.

The brain was embedded in gelatin (in two blocks) and sectioned at 40-micrometer thickness on a freezing microtome. The sections have been stained with a Nissl dye (thionine).

The sections are in the sequential rostro-caudal order, separated by 160 micrometers. The first section (\"PacificAngelshark_Sp24_Thionine_1s1\") contains a scale bar that applies to all sections with no magnification in the name. These images have been imaged in bright field with a 1X objective. Some images have two partially overlapping parts (\"p1\" and \"p2\").

Some d...,