One of the most striking features of all anglerfish is their peculiar method of predation. Ironically this boney fish is aptly named for its technique of fishing using the jig like structure called the esca. For Ceratias holboelli the esca is bioluminescent, production electromagnetic radiation throughout the visible spectrum, but averaging from 470 nanometers to 490 nanometers. Colors of light can range from pink to purple, including white, yellow, orange, yellow-green, blue and a blue-green. It is the blue green light that gains the most transmittance through deep oceanic water. Therefore organisms that dwell in the deep ocean have developed eyes that are most sensitive to this wavelength or turquoise color of light.

An important distinction is that Ceratias holboelli itself is not bioluminescent, but rather the esca houses luminescent gram negative non-endospore producing bacteria that exist in symbiosis with the Krøyer's anglerfish. Recent research suggests that these bioluminescent bacteria differ from species of ceratioid, done by sequencing the 16s ribosomal RNA. For holboelli the most common type of bacteria is vibrio harveyi, which produces a range of light from 475 nanometers to 510 nanometers. It is currently unknown when or how the anglerfish receives these symbionts. Most certainly from the environment but how or why has eluded researchers thus far.

The esca is a highly specialized structure. Not only must the esca house these bacteria and keep them thriving but it must also control the intensity of light fluoresced. Since often the light given off is not constant but rather a pulsating event, lasting from around 1 second to up to 10-12 seconds, with variation from individual to individual. One of the most interesting observations of these bacteria is when they exist out in the environment no luminescence is observed. Therefore there must be an unknown x-factor produced by the anglerfish allowing or perhaps causing the emission of light. It is hypothesized that the control of escal luminescence is by control the bacterial nutrients through the glandular body. This is thought to be done by controlling the blood supply to the esca, which delivers oxygen to the bacteria and are therefore able to respire. Although outside of the esca these bacteria are able to respire, yet unable to produce light. There must be something key to the anglerfish granting light emission capability to vibrio harveyi. This x-factor is thought be in the secretions from the glandular body.

On the inside of the esca there is a photo-pigment that can absorb light emitted from the bacteria, controlling what wavelength of light is emitted from the esca. Interestingly there is an absence of nervous integration in the glandular body and therefore independent of nervous control. Nonetheless there is certainly more to discovered of these fascinating creatures, which are inherently difficult to observe due to the environment disconnect between us and Ceratias holboelli.

Habitat        Home        Nutrition