Photophores in Stomiiform Fishes: Morphology, Distribution, and Putative Behavioral Roles.

Area of Science:

• Marine Biology
• Deep-Sea Ecology
• Ichthyology

Background:

• Bioluminescence is prevalent in deep-sea fishes for various functions like prey attraction and predator avoidance.
• The order Stomiiformes exhibits diverse bioluminescent organs, but some, like complex minute photophores, are poorly understood.
• Understanding photophore diversity is crucial for comprehending deep-sea ecosystems.

Purpose of the Study:

• To synthesize existing literature on four photophore types in Stomiiformes.
• To specifically assess the size, density, and distribution of complex minute photophores in 31 stomiiform species.
• To infer the function of photophores based on light emission orientation in Stomiinae.

Main Methods:

• Literature synthesis of photophore types in Stomiiformes.
• Quantitative assessment of complex minute photophore size, density, and distribution across 31 species.
• Inference of light emission direction from photophore lens placement in 14 Stomiinae species.

Main Results:

• Complex minute photophores were identified in all examined stomiines and one gonostomatid, alongside complex serial photophores.
• Complex minute photophores are significantly smaller and occur at higher densities than complex serial photophores.
• Predicted light emission from complex serial photophores is ventral (counterillumination), while complex minute photophores show variable orientation.

Conclusions:

• Complex minute photophores likely serve multiple functions, including camouflage and communication, due to their variable light emission.
• The findings highlight the underappreciated diversity and functional complexity of bioluminescent organs in deep-sea fishes.
• Further research on stomiiform photophores is essential for understanding their ecological roles.