Biology subjects

Iglesias, T. L.

Publications and source records attributed to Iglesias, T. L..

6 recordsLinked to original sources

bioRxiv2026

Hierarchical processing and polarization encoding in the cephalopod visual system

Coleoid cephalopods (octopus, cuttlefish and squid, hereafter cephalopods) have evolved a range of complex visually-guided behaviours, from dexterous hunting to skin-pattern based camouflage and communication1. They have also evolved sensitivity to the polarization of light2, an adaptation thought to help detect camouflaged or semitransparent predators and prey in low visibility underwater environments3-10. How visual information is processed by the cephalopod brain to support their behaviours remains unclear. Here, studying the bigfin reef squid Sepioteuthis lessoniana, we performed calcium imaging and electrophysiological recordings from populations of neurons in the large visual center of the cephalopod brain, the optic lobe (OL). We revealed that the retina-recipient superficial OL contains a diversity of functionally distinct cell types, spatially organized into sub-layers, processing spatio-temporal features of light intensity and possessing polarization angle specificity. More complex features, e.g. direction selectivity, are seen in deeper regions of the OL cortex, which also exhibits spontaneous waves of neural activity in the absence of visual input. Neurons in the downstream OL medulla exhibit visual receptive field sizes and spontaneous activity levels which increase with brain depth, consistent with the hierarchical processing of visual information through the medullas tree-like anatomical organization. Medulla neurons exhibit sensitivity to local decreases in the degree of linear polarization (DoLP), which they integrate additively with light intensity information. Underwater imaging in the squids habitat off the coast of Okinawa, Japan, demonstrate that polarization sensitivity confers a robust short-range boost in object-background contrast over a range of objects and environmental conditions. These findings reveal convergent principles of hierarchical visual processing shared between cephalopods and vertebrates, and highlight how cephalopods utilise their distinct adaptation of polarization sensitivity to solve universal visual challenges underwater.

neuroscience↗

bioRxiv2024

Growth generates a hyperdisordered pattern of chromatophores on squid skin

While the physics of disordered packing in non-growing systems is well understood, unexplored phenomena can emerge when packing takes place in growing domains. We study the arrangements of pigment cells (chromatophores) on squid skin as a biological example of a packed system on an expanding surface. We find that relative density fluctuations in cell numbers grow with spatial scale. We term this behavior "hyperdisordered", in contrast with hyperuniform behavior in which relative fluctuations tend to zero at large scale. We find that hyperdisordered scaling, akin to that of a critical system, is quantitatively reproduced by a model in which hard disks are randomly inserted in a homogeneously growing surface. In addition, we find that chromatophores increase in size during animal development, but maintain a stationary size distribution. The physical mechanisms described in our work may apply to a broad class of growing dense systems.

biophysics↗

bioRxiv2021

Reevaluating claims of ecological speciation in Halichoeres bivittatus

Understanding the role of ecological processes in speciation has become one of the most active areas of research in marine population biology in recent decades. The traditional view was that allopatry was the primary driver of speciation in marine taxa, but the geography of the marine environment and the dispersal capabilities of many marine organisms render this view somewhat questionable. One of the earliest and most highly cited empirical examples of ecological speciation with gene flow in marine fishes is that of the slippery dick wrasse, Halichoeres bivittatus. Evidence for this cryptic or incipient speciation event was primarily in the form of a deep north-south divergence in a single mitochondrial locus, combined with a finding that these two haplotypes were associated with different habitat types in the Florida Keys and Bermuda, where they overlap. Here we examine habitat assortment in the Florida Keys using a broader sampling of populations and habitat types than were available for the original study, and find no evidence to support the claim that haplotype frequencies differ between habitat types, and little evidence to support any differences between populations. These results severely undermine claims of ecological speciation with gene flow in Halichoeres bivittatus. We argue that future claims of this type should be supported by multiple lines of evidence that illuminate potential mechanisms and allow researchers to rule out alternative explanations for spatial patterns of genetic differences.

evolutionary biology↗

bioRxiv2020

What makes Hemidactylus invasions successful? A case study on the island of Curacao.

Hemidactylus spp. (House geckos) rank among the most successful invasive reptile species worldwide. Hemidactylus mabouia in particular has become ubiquitous across tropical urban settings in the Western Hemisphere. H. mabouia’s ability to thrive in close proximity to humans has led to the rapid displacement of native geckos in urban areas, however the mechanisms driving this displacement remain understudied. Here we combine data from nitrogen and carbon stable isotopes, stomach contents, and morphometric analyses of traits associated with feeding and locomotion to test alternate hypotheses of displacement between H. mabouia and a native gecko, Phyllodactylus martini, on the island of Curaçao. Consistent with expectations of direct food resource competition, we demonstrate substantial overlap of invertebrate prey resources between the species. Additionally, we found strong evidence from both diet content and stable isotope analyses that H. mabouia acts as a vertebrate predator, preying upon P. martini as well as other native and non-native reptiles. Finally, we show that H. mabouia possesses several morphological advantages, including larger sizes in feeding-associated traits and limb proportions that could offer a propulsive locomotor advantage on vertical surfaces. Together, these findings suggest the successful establishment of H. mabouia likely involves a combination of both exploitative interspecific competition and predation. Given the ubiquity of H. mabouia, illuminating the role of this species as both a competitor and a predator casts new concerns on the ecological and demographic impacts of this widespread urban invader.Competing Interest StatementThe authors have declared no competing interest.View Full Text

zoology↗

bioRxiv2019

Evaluating species distribution models with discrimination accuracy is uninformative for many applications

AimSpecies distribution models are used across evolution, ecology, conservation, and epidemiology to make critical decisions and study biological phenomena, often in cases where experimental approaches are intractable. Choices regarding optimal models, methods, and data are typically made based on discrimination accuracy: a models ability to predict subsets of species occurrence data that were withheld during model construction. However, empirical applications of these models often involve making biological inferences based on continuous estimates of relative habitat suitability as a function of environmental predictor variables. We term the reliability of these biological inferences \"functional accuracy.\" We explore the link between discrimination accuracy and functional accuracy.\n\nMethodsUsing a simulation approach we investigate whether models that make good predictions of species distributions correctly infer the underlying relationship between environmental predictors and the suitability of habitat.\n\nResultsWe demonstrate that discrimination accuracy is only informative when models are simple and similar in structure to the true niche, or when data partitioning is geographically structured. However, the utility of discrimination accuracy for selecting models with high functional accuracy was low in all cases.\n\nMain conclusionsThese results suggest that many empirical studies and decisions are based on criteria that are unrelated to models usefulness for their intended purpose. We argue that empirical modeling studies need to place significantly more emphasis on biological insight into the plausibility of models, and that the current approach of maximizing discrimination accuracy at the expense of other considerations is detrimental to both the empirical and methodological literature in this active field. Finally, we argue that future development of the field must include an increased emphasis on simulation; methodological studies based on ability to predict withheld occurrence data may be largely uninformative about best practices for applications where interpretation of models relies on estimating ecological processes, and will unduly penalize more biologically informative modeling approaches.

ecology↗

bioRxiv2017

Cyclic nature of the REM-like state in the cuttlefish Sepia officinalis

Sleep is a state of immobility characterized by three key criteria: an increased threshold of arousal, rapid reversal to an alert state, and evidence of homeostatic \"rebound sleep\" in which there is an increase of time spent in this quiescent state following sleep deprivation. Common European cuttlefish, Sepia officinalis, show states of quiescence during which they meet the last two of these three criteria, yet also show spontaneous bursts of arm and eye movements that accompany rapid changes in chromatophore patterns in the skin. Here we report that this rapid-eye-movement (REM)-like state is cyclic in nature. Iterations of the REM-like state last 2.42 {+/-} 0.22 min ({+/-}SE) and alternate with 34.01 {+/-} 1.49 min of the quiescent sleep-like state. These states alternate for durations lasting 176.89 {+/-} 36.71 min. We found clear evidence that this REM-like state (i) occurs in animals younger than previously reported; (ii) follows an ultradian pattern; (iii) includes intermittent dynamic chromatophore patterning, representing fragments of normal patterning seen in the waking state for a wide range of signaling and camouflage; and (iv) shows variability in the intensity of expression of these skin patterns between and within individuals. These data suggest that cephalopods, which are molluscs with an elaborate brain and complex behavior, possess a sleep-like state that resembles behaviorally the vertebrate REM sleep state, although the exact nature and mechanism of this form of sleep may differ from that of vertebrates.

animal behavior and cognition↗