Ecomorphology of retinal structures in zooplanktivorous haplochromine cichlids (Pisces) from Lake Victoria |
| |
Authors: | Henny J van der Meer Gerrit Ch Anker Cornelis D N Barel |
| |
Institution: | (1) Research Group in Ecological Morphology, Institute for Evolutional and Ecological Sciences, Rijksuniversiteit Leiden, Postbus 9516, 2300 RA Leiden, The Netherlands |
| |
Abstract: | Synopsis Before the decline of the species flock of haplochromine cichlids of Lake Victoria due to the Nile perch upsurge, there were many co-existing haploehromine species such as the taxonomically and ecologically well-studied zooplanktivores of the Mwanza Gulf. In spite of the scarcely separated niches of some of these species, no sign of competition for space or food could be demonstrated. As is argued in this paper, optical differentiation could well be an aspect of adaptive radiation of these zooplanktivores, particularly among the highly sympatric species. Our hypothesis is based on the morphological modifications of retinal structures in nine zooplanktivorous species. Interspecific variation was observed in composition, size and density of the photoreceptors and ganglion cells. The analyses included the intraretinal variation and size dependency of some of the structural parameters. The optical functions deduced from retinal structure indicate distinct interspecific differences in sensitivity thresholds and a slight differentiation in visual resolution. These functions correlate poorly with the photic conditions of the species-specific habitats. The optical properties can, on the other hand, be connected with the more subtle differentiation in food items and feeding behaviour among these species. It is our concluding hypothesis, that the optical differentiation among the haplochromine zooplanktivores primarily served resource partitioning by different modes of visual prey detection rather than niche partitioning by habitat. |
| |
Keywords: | Functional morphology Niche partitioning Photic environment Sensitivity thresholds Visual prey detection Visual resolution |
本文献已被 SpringerLink 等数据库收录! |
|