Functional impact and trophic morphology of small, sand‐sifting fishes on coral reefs

Oligotrophic tropical coral reefs are built on efficient internal energy and nutrient cycling, facilitated by tight trophic interactions. In the competition for available prey, some small fishes have evolved to feed apparently barren sand patches that connect hard-substratum in many reef habitats. One strategy obtaining prey from a particulate matrix is sift out items sediment (often called ‘winnowing’). Yet, link between winnowing consumers their poorly resolved, let alone morphological specialisations enable this foraging behaviour. We used aquarium-based feeding experiments quantify impact of two sand-dwelling goby species (Valenciennea sexguttata Valenciennea strigata) meiobenthos abundance diversity examined actual ingestion using gut content analysis. To identify potential structures involved winnowing, we investigated gobies' apparatus with electron microscopy (SEM) micro-computed tomography (micro-CT). After 4 days sifting through matrix, significantly reduced meiobenthic 30.7% ± 9.2 SE (V. sexguttata) 46.1% 5.1 strigata), but had little diversity. The most abundant groups (copepods annelids) experienced greatest reduction number, suggesting selection size, shape density items. Furthermore, analysis confirmed gobies can efficiently separate heavier inorganic particles (sand), likely specialised epibranchial lobe, pharyngeal jaws highly papillose taste buds oropharyngeal cavity. Our results provide important background reefs. revealed facilitate sand-sifting behaviour access an otherwise inaccessible niche microscopic prey. By having obtain nutritious seemingly sand, suggest act as conduit sand-derived higher levels. Read free Plain Language Summary article Journal blog.