Ontogenetic Variation in the Bony Labyrinth of Monodelphis domestica (Mammalia: Marsupialia) Following Ossification of the Inner Ear Cavities
Article first published online: 20 AUG 2010
Copyright © 2010 Wiley-Liss, Inc.
The Anatomical Record
Volume 293, Issue 11, pages 1896–1912, November 2010
How to Cite
Ekdale, E. G. (2010), Ontogenetic Variation in the Bony Labyrinth of Monodelphis domestica (Mammalia: Marsupialia) Following Ossification of the Inner Ear Cavities. Anat Rec, 293: 1896–1912. doi: 10.1002/ar.21234
- Issue published online: 29 OCT 2010
- Article first published online: 20 AUG 2010
- Manuscript Accepted: 3 JUN 2010
- Manuscript Revised: 7 MAY 2010
- Manuscript Received: 11 FEB 2010
- National Science Foundation. Grant Number: EAR-03457
- bony labyrinth;
- inner ear;
Ontogeny, or the development of an individual from conception to death, is a major source of variation in vertebrate morphology. All anatomical systems are affected by ontogeny, and knowledge of the ontogenetic history of these systems is important to understand when formulating biological interpretations of evolutionary history and physiology. The present study is focused on how variation affects the bony labyrinth across a growth series of an extant mammal after ossification of the inner ear chambers. Digital endocasts of the bony labyrinth were constructed using CT data across an ontogenetic sequence of Monodelphis domestica, an important experimental animal. Various aspects of the labyrinth were measured, including angles between the semicircular canals, number of turns of the cochlea, volumes of inner ear constituents, as well as linear dimensions of semicircular canals. There is a strong correlation between skull length and age, but from 27 days after birth onward, there is no correlation with age among most of the inner ear measurements. Exceptions are the height of the arc of the lateral semicircular canal, the angular deviation of the lateral canal from planarity, the length of the slender portion of the posterior semicircular canal, and the length of the canaliculus cochleae. Adult dimensions of several of the inner ear structures, such as the arcs of the semicircular canals, are achieved before the inner ear is functional, and the non-ontogenetic variation in the bony labyrinth serves as an important source for behavioral, physiological, and possibly phylogenetic information. Anat Rec, 2010. © 2010 Wiley-Liss, Inc.