The Daily Going Ons Of Deep-Sea Fish

New cool research from Wagner et al. that despite the lack of “day” and “night”, deep-sea fish experience daily cycles. What is the trigger? Diurnal changes in bottom currents corresponding to tidal fluctuations. The below graphs shows current direction and velocity on deep-sea floor in the NE Atlantic Ocean indicating 12.5 hour tidal cycles.


The researchers followup by measuring pineal and retinal melatonin in two bottom-dwelling fish, a grenadier Coryphaenoides armatus and a deep-sea eel Synaphobranchus kaupii(below). They additionally quantified the release of melatonin in cultures of isolated pineal organs and retinae in S. kaupii.
Coryphaenoides armatus

Synaphobranchus kaupii, Cambraia Duarte, P.M.N. (c)ImagDOP

Both fish exhibited signs or synchronicity an periodicity in melatonin implying an ‘internal clock’ (figure below, click for larger). Furthermore, peak values correspond to the beginning of the lunar day and night with lower values during the second half of lunar day and night and during moonrise and moonset. The researchers suggest that fish “perceive these cyclic cues with the help of their lateral line system and use this information as an alternative to
photic stimuli to synchronise the various endogeous oscillators to the physical environment.”


Dr. M (1801 Posts)

Craig McClain is the Executive Director of the Lousiana University Marine Consortium. He has conducted deep-sea research for 20 years and published over 50 papers in the area. He has participated in and led dozens of oceanographic expeditions taken him to the Antarctic and the most remote regions of the Pacific and Atlantic. Craig’s research focuses on how energy drives the biology of marine invertebrates from individuals to ecosystems, specifically, seeking to uncover how organisms are adapted to different levels of carbon availability, i.e. food, and how this determines the kinds and number of species in different parts of the oceans. Additionally, Craig is obsessed with the size of things. Sometimes this translated into actually scientific research. Craig’s research has been featured on National Public Radio, Discovery Channel, Fox News, National Geographic and ABC News. In addition to his scientific research, Craig also advocates the need for scientists to connect with the public and is the founder and chief editor of the acclaimed Deep-Sea News (, a popular ocean-themed blog that has won numerous awards. His writing has been featured in Cosmos, Science Illustrated, American Scientist, Wired, Mental Floss, and the Open Lab: The Best Science Writing on the Web.

2 Replies to “The Daily Going Ons Of Deep-Sea Fish”

  1. Very interesting, although it begs the question of just what this cyclical pattern might offer in terms of an evolutionary advantage (an alternate hypothesis might be that such a physiological response is simply an extant remnant of a system from the shallows). Vertical movement patterns are common in both epipelagic and mesopelagic teleost fishes. Is it then simply an internal patterning to take advantage of changing prey availability with current velocity and direction? Time to check out the full article, indeed…

    Thanks for the posting, Craig.

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