SENSORY ECOLOGY OF THE EARLY CAMBRIAN CHENGJIANG BIOTA, SOUTHWEST CHINA

The Cambrian radiation is characterized by the profound environmental and biological changes associated with the bilaterian radiation, which markedly increased the spatial complexity of the marine environment. This increased spatial complexity likely drove the evolution of macroscopic sense organs in mobile bilaretians, leading to their first appearance during the Cambrian. This event has been termed the Cambrian Information Revolution (Plotnick et al., 2010), as animals for the first time began processing far field chemical and visual information with macroscopic sense organs. In order to examine in fine detail the sensory ecology of animals during the Cambrian radiation, the macroscopic sense organs (eyes and antennae) of exceptionally preserved specimens in the early Cambrian Chengjiang biota of Yunnan Province, China are being morphometrically studied. Over 1,600 high-resolution digital images have been captured of 737 Chengjiang specimens from 17 genera. Most of these specimens are arthropods and many have well-preserved eyes and/or antennae. Detailed mesurements are being made of putative sense organs and overall body length. Data collected relating to eyes include: 1) Lateral and medial eyes present or absent; 2) Compound eyes present or absent; 3) On carapace or on stalk; if stalked, if they are apparently moveable; 4) Overall size (greatest length and greatest width); 5) Location - e.g., dorsal or ventral, anterior or lateral margin; 6) Separation of lateral eyes; and 7) Adjacent eye lobe or other morphological structures. Data collected relating to chemosensory and mechanosensory structures (i.e., antennae, antennules, chelicerae, "great appendages") include: 1) General form - annular, chelate, etc.; uniramous or biramous; 2) Number or preserved articles and their sizes; 3) Presence or absence of a peduncle; 4) Total length; 5) Basal width; 6) Visible seta, aesthetascs, or setal pits; and 7) Lateral separation. These morphological and morphometric data are being mapped onto relative abundance and trophic data. This mapping will reveal patterns in the environmental distribution of sensory abilities within the benthic and nektonic realms of the Chengjiang biota, furthering our understanding of the selective forces that fostered the evoultion of macroscopic sense organs.