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The brain in three crustaceans from cavernous darkness.
Martin E J Stegner1, Torben Stemme2, Thomas M Iliffe3
1Allgemeine und Spezielle Zoologie, Institut für Biowissenschaften, Universität Rostock, Universitätsplatz 2, 18055, Rostock, Germany. feuerschwade@yahoo.com.
BMC Neuroscience
|April 17, 2015
Summary
This study reveals significant reductions in optic lobes in blind peracarid crustaceans, indicating a greater reliance on olfactory senses. These findings suggest independent evolutionary adaptations for sensory processing in these unique groups.
Area of Science:
- Crustacean neuroanatomy
- Malacostracan evolution
- Sensory system adaptations
Background:
- Limited neuroanatomical data exists for enigmatic blind peracarid groups (Thermosbaenacea, Spelaeogriphacea, Mictocarididae).
- Reconstructing the malacostracan ground pattern requires understanding these understudied taxa.
- This study provides the first detailed brain description for representatives of these three groups.
Purpose of the Study:
- To describe and compare the brain neuroanatomy of representative species from Thermosbaenacea, Spelaeogriphacea, and Mictocarididae.
- To investigate the extent of optic lobe reduction and the development of other sensory centers in these blind peracarids.
- To infer evolutionary adaptations of the nervous system in relation to sensory input in relict habitats.
Main Methods:
- Serial semi-thin sectioning of brains from representative species.
- Computer-aided 3D-reconstructions of brain structures.
- Immunolabeling (tubulin, nuclear counter-stains) and confocal laser scanning microscopy for Mictocaris halope, including ventral nerve cord analysis.
Main Results:
- All three taxa exhibit a reduced optic lobe and a distal protocerebral neuropil.
- A central complex is present in all studied taxa, most distinct in Spelaeogriphus lepidops.
- Deutocerebral olfactory lobes are large in Mictocaris halope and Spelaeogriphus lepidops, suggesting a dominant olfactory sense; mechanosensory neuropils are reduced.
Conclusions:
- The studied blind peracarids show greater optic lobe reduction than other blind malacostracans, emphasizing olfactory processing.
- The presence of a central complex supports its role in central coordination over visual processing in blind species.
- Independent reductions of optic lobes and hemiellipsoid bodies likely occurred multiple times within Peracarida, not correlated with enhanced mechanosensation.
