An Investigation into the Mechanism Mediating Counterillumination in Myctophid Fishes (Myctophidae)

Authors

Ryan Mullan, Duke University
Alex D. Davis, Duke University
Tracey Sutton, Nova Southeastern UniversityFollow
Sonke Johnsen, Duke University

ORCID

0000-0002-5280-7071

Document Type

Article

Publication Title

The Biological Bulletin

ISSN

0006-3185

Publication Date

4-5-2023

Abstract

Counterillumination is a camouflage strategy employed primarily by mesopelagic fishes, sharks, crustaceans, and squid, which use ventral bioluminescence to obscure their silhouettes when viewed from below. Although certain counterilluminating species have been shown to control the intensity of their ventral emissions to match the background downwelling light, the feedback mechanism mediating this ability is poorly understood. One proposed mechanism involves the presence and use of eye-facing photophores that would allow simultaneous detection and comparison of photophore emissions and downwelling solar light. Eye-facing photophores have been found in at least 34 species of counterilluminating stomiiform fishes and the myctophid Tarletonbeania crenularis. Here, we examined nine phylogenetically spaced myctophid species for eye-facing photophores to assess whether this mechanism is as prevalent in this group as it is in the Stomiiformes. First, microcomputed tomography imaging data were collected for each species, and three-dimensional reconstructions of the fishes were developed to identify potential eye-facing photophores. The fishes were then dissected under a stereomicroscope to confirm the presence of all identified photophores, probe for any photophores missed in the reconstruction analysis, and determine the orientation of the photophores’ emissions. Although photophores were identified near the orbits of all species examined, none of the fishes’ photophores directed light into their orbits, suggesting that myctophids may regulate bioluminescence through an alternative mechanism.

DOI

10.1086/724803

Volume

244

Issue

1

Comments

© 2023 The University of Chicago. All rights reserved.

NSUWorks Citation

Ryan Mullan, Alex D. Davis, Tracey Sutton, and Sonke Johnsen. 2023. An Investigation into the Mechanism Mediating Counterillumination in Myctophid Fishes (Myctophidae) .The Biological Bulletin , (1) . https://nsuworks.nova.edu/occ_facarticles/1331.