A quantitative and qualitative approach to cuttlefish (Sepia officinalis) body patterning

Culligan, Jay (2017) A quantitative and qualitative approach to cuttlefish (Sepia officinalis) body patterning. Doctoral thesis (PhD), University of Sussex.

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Abstract

Cuttlefish are renowned for their ability to quickly alter the colour and texture of their
skin, for camouflage and communication. This is due to the presence of thousands of
pigment-filled sacs, known as chromatophores, which are distributed across the skin. The
chromatophores are innervated by motoneurons, which dilate the chromatophores to create
the spots, stripes, and other markings, known as chromatic components. There are 34
recognized chromatic components, and it is an interesting question how cuttlefish coordinate
the expression of these components to camouflage and communicate.

The digital age has introduced new, powerful algorithms and methods to tease out
subtle features in the coloration patterns, by means of image registration, segmentation, and
identification, as well as methods for modeling the underlying control systems. These tools
offer major new insights into the mechanisms of visual perception. In addition, powerful
techniques have recently been developed that have yet to be applied to this complex visual
motor control system. These methods have large potential in helping discover what features
between the pattern and the environment are necessary to prevent detection.

Here I present four laboratory experiments, that for the first time use machine learning
models, to investigate cuttlefish pattern formation, implementation, and information.

The first two experimental chapters investigate how cuttlefish orchestrate their
chromatic components for camouflage patterns, and what strategies they employ on diverse
backgrounds. I demonstrate that components are expressed more independently than
previously believed, finding that the range of patterns expressed lie on a continuum, allowing
us to suggest a revised classification scheme for cuttlefish body patterns. The diversity of
patterns seem to imply that a cuttlefish could use its repertoire flexibly to display the
maximally cryptic pattern for a given background, however I show that cuttlefish to not in
fact select a single (possibly optimal) camouflage pattern, continually alter their appearance
on a given background, and that the frequency of change increases in relation to the size of
the objects in the environment.

My third chapter investigated the language-like properties of cuttlefish
communication using human speech recognition models. From our subset of cuttlefish
patterns, I discovered cuttlefish utilize a lexicon of 10 patterns, with language-like properties
such as: they obeyed Zipf’s law, contained around 1.6 bits per display, and interestingly,
while 2 patterns were visually similar, they were displayed in separate contexts. By
implementing a regression onto the patterns, I introduce a basic dictionary of cuttlefish terms
and their meaning.

From my investigations into cuttlefish intraspecific signaling, I discovered two
previously undocumented patterns, used in agonistic encounters between cuttlefish. My final
chapter describes these patterns and the contexts they are displayed.

Item Type: Thesis (Doctoral)
Schools and Departments: School of Life Sciences > Biology and Environmental Science
Subjects: Q Science > QL Zoology > QL0360 Invertebrates > QL0403 Mollusca > QL0430.2 Cephalopoda
Depositing User: Library Cataloguing
Date Deposited: 09 Nov 2017 15:17
Last Modified: 09 Nov 2017 15:17
URI: http://sro.sussex.ac.uk/id/eprint/71107

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