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.

Morphological comparison of the detailed structure of gill rakers from three different feeding habits of marine fish species

“…The herbivorous black fish's gill rakers direct water toward the oral cavity roof, where food particles are trapped by the mucous covering before being ingested (Sanderson et al 1991). It was suggested that the gill rakers perform a dual function; they change the direction of the water as a first step and filter food particles as a second (Sanderson et al 1996).…”

Insights into Tissue-Specific Bioaccumulation of Nanoplastics in Marine Medaka as Revealed by a Stable Carbon Isotopic Approach

“…While the δ 13 C value of the gills was decreased by nanoplastic exposure, no significant difference was observed following exposure to microplastics (Figures S1 and S2). In bony fish, including medaka, mucus-covered gill structures (e.g., gill rakers) prevent fouling of the filtering apparatus by retaining undesirable or small dietary particles a few micrometers in diameter. − Entrapped in mucus aggregate, these microsized particles are transported to the esophagus for ingestion, , preventing the accumulation of microplastics. Although nanoplastics may also be entrapped in the mucus, some portion of nanoplastics would likely bioaccumulate in gill epithelium cells due to the permeability of nanoplastics, , as sediment particles (<500 nm) have been identified intracellularly in salmonid gill epithelial cells …”

Biomimetic models of fish gill rakers as lateral displacement arrays for particle separation

“…figure 1(e)) [29,62]. Both mucus and protuberances have been hypothesized or demonstrated in experiments with a diverse variety of live suspension-feeding fish to play key roles in particle retention and fluid dynamics [46,63]. Microridges detected on the leading edge of basking shark gill rakers have recently been demonstrated in CFD simulations to have the potential for profound effects on flow patterns during filtration [47].…”