Scan, extract, wrap, compute:a 3D method to analyse morphological shape differences

Quantitative analysis of shape and form is critical in many biological disciplines, as context-dependent morphotypes reflect changes in gene expression and physiology, e.g., in comparisons of environment-dependent phenotypes, forward/reverse genetic assays or shape development during ontogenesis. 3D-shape rendering methods produce models with arbitrarily numbered, and therefore non-comparable, mesh points. However, this prevents direct comparisons. We introduce a workflow that allows the generation of comparable 3D models based on several specimens. Translocations between points of modelled morphotypes are plotted as heat maps and statistically tested. With this workflow, we are able to detect, model and investigate the significance of shape and form alterations in all spatial dimensions, demonstrated with different morphotypes of the pond-dwelling microcrustacean Daphnia. Furthermore, it allows the detection even of inconspicuous morphological features that can be exported to programs for subsequent analysis, e.g., streamline- or finite-element analysis

Facing the Green Threat: A Water Flea’s Defenses against a Carnivorous Plant

Every ecosystem shows multiple levels of species interactions, which are often difficult to isolate and to classify regarding their specific nature. For most of the observed interactions, it comes down to either competition or consumption. The modes of consumption are various and defined by the nature of the consumed organism, e.g., carnivory, herbivory, as well as the extent of the consumption, e.g., grazing, parasitism. While the majority of consumers are animals, carnivorous plants can also pose a threat to arthropods. Water fleas of the family Daphniidae are keystone species in many lentic ecosystems. As most abundant filter feeders, they link the primary production to higher trophic levels. As a response to the high predatory pressures, water fleas have evolved various inducible defenses against animal predators. Here we show the first example, to our knowledge, in Ceriodaphnia dubia of such inducible defenses of an animal against a coexisting plant predator, i.e., the carnivorous bladderwort (Utricularia x neglecta Lehm, Lentibulariaceae). When the bladderwort is present, C. dubia shows changes in morphology, life history and behavior. While the morphological and behavioral adaptations improve C. dubia’s survival rate in the presence of this predator, the life-history parameters likely reflect trade-offs for the defense

Chaoborus and Gasterosteus Anti-Predator Responses in Daphnia pulex Are Mediated by Independent Cholinergic and Gabaergic Neuronal Signals

Many prey species evolved inducible defense strategies that protect effectively against predation threats. Especially the crustacean Daphnia emerged as a model system for studying the ecology and evolution of inducible defenses. Daphnia pulex e.g. shows different phenotypic adaptations against vertebrate and invertebrate predators. In response to the invertebrate phantom midge larvae Chaoborus (Diptera) D. pulex develops defensive morphological defenses (neckteeth). Cues originating from predatory fish result in life history changes in which resources are allocated from somatic growth to reproduction. While there are hints that responses against Chaoborus cues are transmitted involving cholinergic neuronal pathways, nothing is known about the neurophysiology underlying the transmission of fish related cues. We investigated the neurophysiological basis underlying the activation of inducible defenses in D. pulex using induction assays with the invertebrate predator Chaoborus and the three-spined stickleback Gasterosteus aculeatus. Predator-specific cues were combined with neuro-effective substances that stimulated or inhibited the cholinergic and gabaergic nervous system. We show that cholinergic-dependent pathways are involved in the perception and transmission of Chaoborus cues, while GABA was not involved. Thus, the cholinergic nervous system independently mediates the development of morphological defenses in response to Chaoborus cues. In contrast, only the inhibitory effect of GABA significantly influence fish-induced life history changes, while the application of cholinergic stimulants had no effect in combination with fish related cues. Our results show that cholinergic stimulation mediates signal transmission of Chaoborus cues leading to morphological defenses. Fish cues, which are responsible for predator-specific life history adaptations involve gabaergic control. Our study shows that both pathways are independent and thus potentially allow for adjustment of responses to variable predation regimes

Daphnia\it Daphnia carapace

Phänotypische Plastizität bezeichnet die Fähigkeit eines Organismus mit bestimmtem Genotyp unterschiedliche Phänotypen als Reaktion auf sich ändernde Umweltbedingungen auszuprägen. Eine Form der phänotypischen Plastizität sind induzierbare Verteidigungen, die Reaktion einer Art auf Anwesenheit von Prädatoren. Die Süßwasser-Krebs-Gattung $\it Daphnia$ ist bekannt für ihre induzierbaren morphologischen Verteidigungen gegen Prädatoren. $\it Daphnia$ besitzt zudem eine universelle Verteidigung gegen die mechanische Belastung einer Räuberattacke: Den Carapax. In meinem Promotionsprojekt habe ich die Carapaxstruktur mit elektronenmikroskopischen Verfahren untersucht, sowie Änderungen in seiner Steifigkeit als Reaktion auf Räuber mittels Finite Elemente Analyse kombiniert mit biomechanischen Methoden untersucht. Ich konnte, unter anderem, zeigen, dass die Steifigkeitsänderungen auf eine strukturelle Reorganisation der Cuticula zurückzuführen sind.Phenotypic plasticity is the ability of an organism with a given genotype to express different phenotypes as a reaction upon changing environments. One type of phenotypic plasticity are inducible defenses, responses of a species to the presence of predators. The freshwater crustacean $\it Daphnia$ is prominent for its ability to express inducible morphological defenses against predators. $\it Daphnia$ also possesses a general defense trait against the mechanical impact of a predatory attack i.e. the carapace. In my PhD project I investigated the carapace structure using electron microscopy methods. Furthermore, I combined finite element analysis with biomechanical testing in order to analyze its predator induced alterations in stiffness. Amongst other insights, I could show that the stiffness alterations are caused by structural rearrangement of the carapace’s cuticle

Editorial: Sensory Ecology of Phenotypic Plasticity : From Receptors via Modulators to Effectors

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Physostigmine (5 nM) effect on morphological defenses in dependence of <i>Chaoborus</i> and <i>Gasterosteus</i> kairomone (Bonferroni-corrected Mann-Whitney U comparison).

<p>(NT) neckteeth.</p><p>(ns) not significant.</p><p>(Effect) describes the overall increase or decrease of the observed treatment.</p

Life history shifts against <i>Gasterosteus</i> predatory cues at sexual maturity.

<p>A: In dependence of the <i>Gasterosteus</i> kairomone the body length is significantly increased. B: Time to reach maturity is significantly shortened and C: The number of neonates is significantly increased. Plotted are medians and interquartile ranges. Bonferroni corrected significance levels: *p<0.025; **p<0.005; ***p<0.0005.</p

A Tail of Four Fishes: An Analysis of Kinematics and Material Properties of Elongate Fishes

The elongate body plan is present in many groups of fishes, and this morphology dictates functional consequences seen in swimming behavior. Previous work has shown that increasing the number of vertebrae, or decreasing the intervertebral joint length, in a fixed length artificial system increases stiffness. Tails with increased stiffness can generate more power from tail beats, resulting in an increased mean swimming speed. This demonstrates the impacts of morphology on both material properties and kinematics, establishing mechanisms for form contributing to function. Here, we wanted to investigate relationships between form and ecological function, such as differences in dietary strategies and habitat preferences among fish species. This study aims to characterize and compare the kinematics, material properties, and vertebral morphology of four species of elongate fishes: Anoplarchus insignis, Anoplarchus purpurescens, Xiphister atropurpureus, and Xiphister mucosus. We hypothesized that these properties would differ among the four species due to their differential ecological niches. To calculate kinematic variables, we filmed these fishes swimming volitionally. We also measured body stiffness by bending the abdominal and tail regions of sacrificed individuals in different stages of dissection (whole body, removed skin, and removed muscle). Finally, we counted the number of vertebrae from CT scans of each species to quantify vertebral morphology. Principal component and linear discriminant analyses suggested that the elongate fish species can be distinguished from one another by their material properties, morphology, and swimming kinematics. With this information combined, we can draw connections between the physical properties of the fishes and their ecological niches

Atropine (5 µM) effect on morphological defenses in dependence of <i>Chaoborus</i> and <i>Gasterosteus</i> kairomone (Bonferroni- corrected Mann-Whitney U comparison).

<p>(NT) neckteeth.</p><p>(ns) not significant.</p><p>(Effect) describes the overall increase or decrease of the observed treatment.</p

Gabaergically modulated life history parameters.

<p>A: Body length in dependence of increasing <i>Gasterosteus</i> kairomone concentrations and GABA (15 µM). Body length is significantly reduced by GABA stimulation at high <i>Gasterosteus</i> kairomone concentrations (50% and 100%, Mann-Whitney U comparison p<0.01). B: Generation time is significantly increased by GABA stimulation at low and medium <i>Gasterosteus</i> kairomone concentrations (25% and 50%, Mann- Whitney U comparison p<0.01). C: The fecundity (number of eggs in the brood pouch) is significantly reduced by GABA stimulation at high <i>Gasterosteus</i> kairomone concentrations (75% and 100%, Mann- Whitney U comparison p<0.01).</p