Allometric scaling factors are highly variable in colonial animals, ranging the expectations of Kleiber’s law to isometric scaling. The causes of allometric scaling of respiration rate in colonial animals are unclear, past studies have indicated that colony shape or integration may be important traits related to scaling factor. To test which factors influence allometric scaling in colonial animals we estimated three novel scaling factors for colonial rotifers and collected known scaling factors for 37 colonial animals from the literature. The novel scaling factors were estimated by measuring respiration rate and colony size. Respiration rate was measured using a Loligo microplate system. After oxygen measurement, colony size was determined from photographs with ImageJ. We estimated a scaling factor of 0.5 to 1.0 for colonial rotifers. Scaling factors were collected from the literature focusing on colonies that present some level of physiological or morphological integration, including modular organisms as well as siphonophores and eusocial insects. A linear mixed regression with hierarchical taxonomic ranks as random effects showed that traits significantly related to allometric scaling factor in colonial animals included colony shape, with globular and linear colonies associated with isometric scaling, whereas unattached lifestyle and the presence of shared extra zooidal structures was related to a lower allometric scaling factor (marginal r-squared: 0.40). Our results suggest that a variety of biological traits relate to allometric scaling of respiration rate.

Primary Presenter: Patrick Brown, University of Texas at El Paso (pdbrown3@miners.utep.edu)

Authors:

Elizabeth Walsh, The University of Texas at El Paso  (ewalsh@utep.edu)