Graduate Researcher
Monterey Bay Aquarium Research Institute
7700 Sandholdt Road
Moss Landing, CA 95039
Phone: (831) 775-1920
Fax: (831) 775-1620
email: sbush
My research interests are currently focused on deep sea squid ecology, particularly their defensive behaviors.
Deep-sea squid ink release
Ink release by cephalopods (squid, octopus, cuttlefish) is familiar to many people and it's obvious cloaking abilties has led to a long held assumption that it is primarily a visual defense. We assume the dark ink mass distracts and/or confuses a predator so a cephalopod can escape or hide within the ink. Scientists have historically believed that ink release would be useless as a defense for deep-sea cephalopods because light is attenuated by water so that much of deep sea is nearly dark. In such a habitat, a dark ink cloud must be useless. However, observations by the MBARI Midwater Ecology lab using Remotely Operated Vehicles indicate that midwater squid living primarily below the photic zone do release ink throughout their depth range. I compiled these observations to determine which species released ink, at what depths, in what situations, and what were the concurrent behaviors. This resulted in the article 'Ink utilization by mesopelagic squid' (Bush & Robison, 2007). I am now focusing on chemical analyses of deep-sea squid ink to pick out differences between species and possibly its' composition. I am also conducting laboratory tests utilizing squid and squid predators to deduce it's overall use as a defensive measure.
See videos of deep-sea squid releasing ink here.
Reactions to deep-sea squid ink
If we see a deep-sea squid release ink in response to another animal or watch midwater animals react to squid ink, we could better understand why squids release ink. Unfortunately, observations of species interactions in the deep sea are rare. To determine midwater animal reactions to squid ink, I have to create my own ‘interactions’. With the help of MBARI ROV pilots and technicians, I designed an ‘Ink Ejector’ to release collected deep-sea squid ink in the water column. Encounters with squid and fish allow us to observe whether animals behave differently when ink is released.
Deep-sea squid ink chemistry
Ink is used in different ways by different species; it is released in different forms, at different depths, even has subtle differences in color. One way that ink may function as a defense for deep-sea squid is that it has some important chemical properties. Ink may contain molecules that are distasteful to some predators and/or attractive to some predators. If ink is distasteful, and a predator mistakes an ink pseudomorph for a squid, it may concentrate hunting efforts on another prey type, such as fish. If ink is attractive it may distract a predator while the squid escapes unnoticed. I have collected ink from 15 species of deep-sea cephalopod and several shallow-dwelling species to compare their chemical composition using Liquid Chromatography-Mass Spectroscopy. This method separates molecules within a mixture by type, then gives the molecular mass of each, allowing comparisons of molecules present in inks from different species.
Behaving in the dark
Shallow-water cephalopods are well-known for their body patterning, consisting of changes in skin coloration, skin texture, body posture, and body movement. These are used in visual communication with other cephalopods, potential prey, and predators. Scientists reasoned that body patterning in species living within low-light environments, such as the deep sea, would have limited body patterning. I made the first in depth observations of a deep-sea squid species to test the hypothesis that deep-sea cephalopods have limited coloration, posturing, and movement. Observations of Octopoteuthis deletron indicated this species is capable of many patterns, comparable in number to shallow-water squid species. This research indicates our limited understanding of deep-sea squid ecology with regard to the use of body patterning.
Squid arm autotomy
The midwater squid Octopoteuthis deletron, or 'octopus squid', is so-called because it lacks a pair of feeding tentacles. Individuals develop tentacles, but either lose or resorb them at the paralarval stage. The eight remaining arms, which are tipped with large bioluminescent photophores, function in prey capture. In situ and laboratory observations of O. deletron and its congenerics O. neilseni and O. megaptera (Young & Vecchione 2006) indicate that these squid may be able to autotomize, or voluntarily release, part of an arm. We have observed shed arms continue to move and the arm-tip photophores bioluminesce. This behavior is hypothesized to be defensive, whereby it startles, distracts, or confuses a potential predator. I am using data collected on MBARI Remotely Operated Vehicle expeditions as well as laboratory observations of collected specimens to determine whether arm loss occurs in natural situations, how often individuals are observed with missing arms, what stimuli trigger arm loss, what are the associated behaviors, and whether the animal has control over arm loss. Histological sections of collected specimens' arms are being examined to determine the arm release mechanism.
Other information:
Squid science: Field notes from Stephanie Bush - UC Museum of Paleontology feature
References:
Bush, S. L., and B. H. Robison. 2007. Ink utilization by mesopelagic squid. Marine Biology. 152(3): 485-494.
Young, Richard E. and Vecchione, Michael. 2006. Octopoteuthis Ruppell 1844. Version 24 April 2006. http://tolweb.org/Octopoteuthis/19839/2006.04.24 in The Tree of Life Web Project, http://tolweb.org/
Last updated: Apr. 30, 2008