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

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

Sex differences in thermogenesis structure behavior and contact within huddles of infant mice.

Brown adipose tissue (BAT) is a thermogenic effector abundant in most mammalian infants. For multiparous species such as rats and mice, the interscapular BAT deposit provides both an emergency "thermal blanket" and a target for nestmates seeking warmth, thereby increasing the cohesiveness of huddling groups. Sex differences in BAT regulation and thermogenesis have been documented in a number of species, including mice (Mus musculus)--with females generally exhibiting relative upregulation of BAT. It is nonetheless unknown whether this difference affects the behavioral dynamics occurring within huddles of infant rodents. We investigated sex differences in BAT thermogenesis and its relation to contact while huddling in eight-day-old C57BL/6 mouse pups using infrared thermography, scoring of contact, and causal modeling of the relation between interscapular temperature relative to other pups in the huddle (T IS (rel)) and contacts while huddling. We found that females were warmer than their male siblings during cold challenge, under conditions both in which pups were isolated and in which pups could actively huddle in groups of six (3 male, 3 female). This difference garnered females significantly more contacts from other pups than males during cold-induced huddling. Granger analyses revealed a significant negative feedback relationship between contacts with males and T IS (rel) for females, and positive feedback between contacts with females and T IS (rel) for males, indicating that male pups drained heat from female siblings while huddling. Significant sex assortment nonetheless occurred, such that females made more contacts with other females than expected by chance, apparently outcompeting males for access to each other. These results provide further evidence of enhanced BAT thermogenesis in female mice. Slight differences in BAT can significantly structure the behavioral dynamics occurring in huddles, resulting in differences in the quantity and quality of contacts obtained by the individuals therein, creating sex differences in behavioral interactions beginning in early infancy

Granger (causal) analyses of relative T_IS and contact during cold challenge.

<p>The results of Granger analyses on relative T_IS (T_IS^rel) and contact with males and females. Asterisks indicate significant Granger causality, evaluated at <i>α</i> = .05/6 = .0083. Non-significant results (p<.05) are also shown to depict trends in the data. Arrows indicate that a change in one variable at time <i>t_n</i> predicts a change in another variable at <i>t_n+lag</i>. For example, in all but the Female Lag 0 models, T_IS^rel is a stronger predictor of contacts with females than the reverse. Arrows in both directions indicate a feedback relationship between the two variables <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0087405#pone.0087405-Granger3" target="_blank">[65]</a>; for example, our results indicate negative feedback between female T_IS^rel and female contacts with males and positive feedback between the male T_IS^rel and male contacts with females. The coloration of arrows indicates significant lagged Pearson product moment correlations between the two variables (<i>p</i><.001), with positive and negative correlations indicated by green and red, respectively. Tests between T_IS^rel and total contacts were run, but are not shown given that none were statistically significant. Models for Lag 3 were constructed but are not shown. For females, the model was null (no significant Granger causality detected), whereas for males the only significant effect was that male T_IS^rel Granger caused male contacts with males (F = 4.94, <i>p</i><.003).</p

Infrared thermography.

<p>(<b>A</b>) Sample thermograph from Experiment 1, showing 2 male (top and left) and 2 female (bottom and right) pups during cold challenge. (<b>B–C</b>) Sample thermographs of litters during cold challenge in Experiment 2. In (<b>C</b>) the zones used for measuring interscapular (<b>D</b>) and rump (<b>E</b>) temperatures (T_IS and T_rump, respectively) are shown for a pup that has separated from its huddle.</p

Correlation between relative T_IS and contact.

<p>Linear regressions, coefficients of determination (<i>R²</i>), and <i>p</i>-values for Pearson product moment correlations on T_IS relative to huddlemates (T_IS^rel) and (a) total contacts, (b) contacts with females, and (c) contacts with males, during the warm and cool phases of Experiment 2 (left and right, respectively). Asterisks indicate significant correlation, using a criterion of <i>α</i> = .05/6 = 0083. As can be seen, there was no relationship between T_IS^rel and contact during the warm phase, and a significant correlation between T_IS^rel and both total contacts and contacts with females, but not contacts with males, during the cool phase.</p

Scoring of contact behavior.

<p>A depiction of the system used for scoring contact behavior, adapted from that employed by Sokoloff and Blumberg <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0087405#pone.0087405-Sokoloff1" target="_blank">[28]</a>. Each pup in the litter was scored each minute for how many males (blue pups) and females (pink pups) they were in contact with, excluding contacts via tails and outstretched paws. Each combination of contacts was assigned a unique identifier or “contactogon”. For example, 0 M 2 F designates contact with zero males and two females. Contactogons possible for only a single sex (e.g., 3 M 0 F) are not shown, and were collapsed into a single category for the purposes of statistical analysis.</p

Thermal measurements for Experiment 2.

<p>Average temperatures for interscapular (T_IS) and rump (T_rump) regions ± SEM for male (blue lines) and female (red/pink lines) PND8 mouse pups.</p

Granger (causal) analyses of relative T_IS and contact during the warm phase.

<p>The results of Granger analyses on relative T_IS (T_IS^rel) and contact with males and females. Asterisks indicate significant Granger causality, evaluated at <i>α</i> = .05/6 = .0083. Non-significant results (p<.05) are also shown to depict trends in the data. The coloration of arrows indicates significant lagged Pearson product moment correlations between the two variables (<i>p</i><.05), with positive and negative correlations indicated by green and red, respectively. Tests between T_IS^rel and total contacts were run, but are not shown.</p

Consistency of Sex Differences in Thermal and Contact Measures in Experiment 2.

<p><i>Note</i>. Results for Sign tests on thermal and contact measures obtained under identical T_a for the two sexes. <i>Asterisks</i> indicate a significant difference. In all cases of a significant difference this indicated higher female over male values and greater same- versus opposite-sex and female-female over male-male contacts.</p