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Mucus entrapment of particles by a suspension-feeding tilapia (Pisces: Cichlidae)
Abstract:
A miniature fiberoptic endoscope was used to observe the processes of particle encounter and retention inside the buccopharyngeal cavity of suspension-feeding tilapia. Small particles (38 µm to 1.0 mm in diameter) were trapped in strands and aggregates of mucus, which usually slid posteriorly on the ceratobranchials of arches IIV towards the esophagus while the fish pumped water through the buccopharyngeal cavity. During stage 1 of periodic reversals of water flow inside the buccopharynx, mucus-bound particles usually lifted off the arch surfaces and travelled a short distance in an anterior or anterodorsal direction. During stage 2 of a reversal, the mucus usually resumed travel in a posterior or posteroventral direction and exited the field of view. Mucus was present less often during feeding on large particles (310 mm in diameter) than on small particles, and large particles were rarely observed to be attached to mucus. We discuss the advantages to suspension-feeding fishes of using aerosol filtration by mucus entrapment rather than sieving, and predict that many cichlid and cyprinid suspension feeders that consume bacteria and phytoplankton use mucus for aerosol filtration.
Insights
Tilapia suspension feeders use mucus to trap small food particles, aiding in aerosol filtration. This mucus-bound particle transport differs significantly from how larger particles are processed.
Area of Science:
- Ichthyology
- Aquatic Ecology
- Animal Physiology
Background:
- Suspension-feeding fishes utilize various mechanisms for particle capture.
- Mucus plays a role in particle retention in some aquatic organisms.
- Understanding buccopharyngeal processing is key to fish feeding ecology.
Purpose of the Study:
- To observe particle encounter and retention in tilapia buccopharyngeal cavities.
- To investigate the role of mucus in the feeding of suspension-feeding tilapia.
- To compare particle processing of small versus large food items.
Main Methods:
- Utilized a miniature fiberoptic endoscope for in-vivo observation.
- Recorded particle interactions within the buccopharyngeal cavity of tilapia.
- Analyzed particle size, mucus association, and transport dynamics.
Main Results:
- Small particles (38 µm–1.0 mm) were trapped in mucus strands and aggregates.
- Mucus-bound particles exhibited posterior and anterior/anterodorsal movement during water flow reversals.
- Mucus association was less frequent with large particles (3–10 mm).
Conclusions:
- Mucus entrapment is an effective aerosol filtration strategy for small particles in tilapia.
- This mechanism differs from sieving and may be common in other suspension feeders like cichlids and cyprinids.
- Mucus-based filtration offers advantages for consuming bacteria and phytoplankton.