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Multimodal displays are a long-standing fascination of behavioural biologists because many signallers can adjust display architecture or switch signalling modality, often to exploit the advantages or avoid the disadvantages of a particular signalling environment. Yet, how such adaptive flexibility occurs remains poorly understood. Here, we argue that studying the endocrine modulation of multimodal signal production can close this knowledge gap. We first highlight a concept well known to behavioural endocrinologists that sex steroid hormones, and in particular androgens, can mediate the integration of multiple signalling traits at the organismal level. We then hypothesize that endocrine responses also play a role in maintaining flexibility in multimodal displays over time and space and may be key in responding quickly to fluctuating environments. To support these ideas, we use as our major example our own work in ‘foot-flagging’ frogs, Staurois parvus. We provide an overview of prior work on multimodal signalling in this species, as well as initial data from network analyses that point to androgen-mediated adaptive shifts in multimodal display architecture. We conclude by suggesting future work to further elucidate the connections between the signalling environment, androgenic hormones and behavioural flexibility in multimodal communication.

This paper deals with the Keller–Segel–Navier–Stokes model with indirect signal production in a three-dimensional (3D) bounded domain with smooth boundary. When the logistic-type degradation here is weaker than the usual quadratic case, it is proved that for any sufficiently regular initial data, the associated no-flux/no-flux/no-flux/Dirichlet problem possesses at least one globally defined solution in an appropriate generalized sense, and that this solution is uniformly bounded in [Formula: see text] with any [Formula: see text]. Moreover, under an explicit condition on the chemotactic sensitivity, these solutions are shown to stabilize toward the corresponding spatially homogeneous state in the sense of some suitable norms. We underline that the same results were established for the corresponding system with direct signal production in a well-known result if the degradation is quadratic. Our result rigorously confirms that the indirect signal production mechanism genuinely contributes to the global solvability of the 3D Keller–Segel–Navier–Stokes system.

Funding: European Commission - European Union’s 8th Framework Programme, Horizon 2020. Two language laws have been identified as consistent patterns shaping animal behaviour, both acting on the organizational level of communicative systems. Zipf's law of brevity describes a negative relationship between behavioural length and frequency. Menzerath's law defines a negative correlation between the number of behaviours in a sequence and average length of the behaviour composing it. Both laws have been linked with the information-theoretic principle of compression, which tends to minimize code length. We investigated their presence in a case study of male chimpanzee sexual solicitation gesture. We failed to find evidence supporting Zipf's law of brevity, but solicitation gestures followed Menzerath's law: longer sequences had shorter average gesture duration. Our results extend previous findings suggesting gesturing may be limited by individual energetic constraints. However, such patterns may only emerge in sufficiently large datasets. Chimpanzee gestural repertoires do not appear to manifest a consistent principle of compression previously described in many other close-range systems of communication. Importantly, the same signallers and signals were previously shown to adhere to these laws in subsets of the repertoire when used in play; highlighting that, in addition to selection on the signal repertoire, ape gestural expression appears shaped by factors in the immediate socio-ecological context. Publisher PDF

Signals often covary with physiological and behavioural traits to form an axis of integrated phenotypic variation associated with reproductive performance. This pattern of phenotypic integration could result from intrinsic between-individual differences that are causally related to signal production, physiology and behaviour. Alternatively, signal expression itself might generate feedback between physiology, behaviour and the experienced social environment, resulting in an integrated phenotype. We manipulated the plumage of female tree swallows, Tachycineta bicolor, to decouple the expression of a social signal from any pre-existing behavioural or physiological differences. We collected a time series of physiological samples, monitored nestbox visiting patterns with a sensor network and tracked reproductive performance. Relative to sham controls, dulled females' nests were visited more by conspecific females and less by males. Dulled females subsequently made fewer trips to other nestboxes and increased nestling provisioning. However, these changes in nestbox visiting patterns depended on both the focal female's pretreatment plumage and on the breeding stage. These differences resulted in an altered internal microbiome and glucose levels and, ultimately, dulled females produced more offspring. Moreover, dulled females produced larger clutches than control females in the year after the manipulation. Thus, signal variation alone – independent from any pre-existing differences – had a sustained causal effect on a suite of integrated traits. This finding suggests that dynamic feedback may play a role in coordinating an integrated signalling phenotype.

Animal communication signals are regulated by multiple hormonal axes that ensure appropriate signal targeting, timing, and information content. The regulatory roles of steroid hormones and many peptide hormones are well understood and documented across a wide range of vertebrate taxa. Two recent studies have reported a novel function for leptin, a peptide hormone central to energy balance regulation: regulating communication signals of weakly electric fish and singing mice. With only limited evidence available at this time, a key question is just how widespread leptinergic regulation of communication signals is within and across taxa. A second important question is what features of communication signals are subject to leptinergic regulation. Here, we consider the functional significance of leptinergic regulation of animal communication signals in the context of both direct and indirect signal metabolic costs. Direct costs arise from metabolic investment in signal production, while indirect costs arise from the predation and social conflict consequences of the signal's information content. We propose a preliminary conceptual framework for predicting which species will exhibit leptinergic regulation of their communication signals and which signal features leptin will regulate. This framework suggests a number of directly testable predictions within and across taxa. Accounting for additional factors such as life history and the potential co-regulation of communication signals by leptin and glucocorticoids will likely require modification or elaboration of this model.

The Keller-Segel-Stokes type system with indirect signal production, as given by { n t + u ⋅ ∇ n = Δ n − ∇ ⋅ ( n S ( n ) ∇ v ) , x ∈ Ω , t > 0 , v t + u ⋅ ∇ v = Δ v − v + w , x ∈ Ω , t > 0 , w t + u ⋅ ∇ w = Δ w − w + n , x ∈ Ω , t > 0 , u t + ∇ P = Δ u + n ∇ ϕ , ∇ ⋅ u = 0 , x ∈ Ω , t > 0 , is considered in a bounded domain Ω ⊂ R N , N ∈ { 2 , 3 } , with smooth boundary, where ϕ ∈ C 2 ( Ω ‾ ) and S ∈ C 2 ( [ 0 , ∞ ) ) . Under the assumption that there exist C S > 0 and α ≥ 0 such that | S ( n ) | ≤ C S ( n + 1 ) − α for all n ≥ 0 , it is shown that for all suitably regular initial data an associated initial-boundary value problem possesses a globally defined bounded classical solution in the case N = 2 . In the case of N = 3 , the conclusion is also true provided α > 1 9 .

Many animals use signals, such as vocalizations, to recognize familiar individuals. However, animals risk making recognition mistakes because the signal properties of different individuals often overlap due to within-individual variation in signal production. To understand the relationship between signal variation and decision rules for social recognition, we studied male golden rocket frogs, which recognize the calls of territory neighbors and respond less aggressively to a neighbor’s calls than to the calls of strangers. We quantified patterns of individual variation in acoustic properties of calls and predicted optimal discrimination thresholds using a signal detection theory model of receiver utility that incorporated signal variation, the payoffs of correct and incorrect decisions, and the rates of encounters with neighbors and strangers. We then experimentally determined thresholds for discriminating between neighbors and strangers using a habituation-discrimination experiment with territorial males in the field. Males required a threshold difference between 9% and 12% to discriminate between calls differing in temporal properties; this threshold matched those predicted by a signal detection theory model under ecologically realistic assumptions of infrequent encounters with strangers and relatively costly missed detections of strangers. We demonstrate empirically that receivers group continuous variation in vocalizations into discrete social categories and show that signal detection theory can be applied to investigate evolved decision rules.

As a kind of convenient, fast, and online analysis technology, point-of-care testing (POCT) technology has been widely used in disease diagnosis, health management, environmental monitoring and emergency response analysis. To date, it is a hot spot to develop novel strategy for the detection of various targets based on the simple, rapid and sensitive signal readout and different signal production, transfer and amplification strategies in the field of POCT. The introduction of some nanozymes and functionalized nanomaterials with special catalytic properties further accelerate the application of simple signal readout such as color, temperature, pressure, weight and distance, which greatly promotes the development of simple readout-based POCT methods, and expands the analytical applications of such methods. In this paper, we summarized the principles, classifications, and the applications of these emerging POCT methods for the analysis of life-related targets and reviewed their current challenges and future application prospects.

This paper deals with a fully parabolic inter-species chemotaxis-competition system with indirect signal production \begin{document}$ \begin{eqnarray*} \label{1a} \left\{ \begin{split}{} u'>under zero Neumann boundary conditions in a smooth bounded domain \begin{document}$ \Omega\subset \mathbb{R}^{N} $\end{document} ( \begin{document}$ N\geq 1 $\end{document} ), where \begin{document}$ d_{u}>0, d_{v}>0 $\end{document} and \begin{document}$ d_{w}>0 $\end{document} are the diffusion coefficients, \begin{document}$ \chi\in \mathbb{R} $\end{document} is the chemotactic coefficient, \begin{document}$ \mu_{1}>0 $\end{document} and \begin{document}$ \mu_{2}>0 $\end{document} are the population growth rates, \begin{document}$ a_{1}>0, a_{2}>0 $\end{document} denote the strength coefficients of competition, and \begin{document}$ \lambda $\end{document} and \begin{document}$ \alpha $\end{document} describe the rates of signal degradation and production, respectively. Global boundedness of solutions to the above system with \begin{document}$ \chi>0 $\end{document} was established by Tello and Wrzosek in [J. Math. Anal. Appl. 459 (2018) 1233-1250]. The main purpose of the paper is further to give the long-time asymptotic behavior of global bounded solutions, which could not be derived in the previous work.

In this work, we consider the quasilinear attraction–repulsion chemotaxis model with nonlinear signal production and logistic-type source. We present the global existence of classical solutions under appropriate regularity assumptions on the initial data. In addition, the asymptotic behavior of the solutions is studied, and our results generalize and improve some well-known results in the literature.

In this paper, we consider the chemotaxis system with indirect signal production and logistic-type source under homogeneous Neumann boundary conditions in a bounded domain with smooth boundary. A unique global classical solution is obtained under a critical parameter condition.

An important goal of synthetic biology is to build biosensors and circuits with well-defined input-output relationships that operate at speeds found in natural biological systems. However, for molecular computation, most commonly used genetic circuit elements typically involve several steps from input detection to output signal production: transcription, translation, and post-translational modifications. These multiple steps together require up to several hours to respond to a single stimulus, and this limits the overall speed and complexity of genetic circuits. To address this gap, molecular frameworks that rely exclusively on post-translational steps to realize reaction networks that can process inputs at a time scale of seconds to minutes have been proposed. Here, we build mathematical models of fast biosensors capable of producing Boolean logic functionality. We employ protease-based chemical and light-induced switches, investigate their operation, and provide selection guidelines for their use as on-off switches. As a proof of concept, we implement a rapamycin-induced switch

This paper deals with a two-chemical reaction type Keller-Segel system coupled with incompressible viscous fluid equations which models the dynamics of cells in fluid in a two dimensional bounded domain $\varOmega $ $$ \left\{ \textstyle\begin{array}{l} \partial _{t}n+\mathbf {u}\cdot \nabla n = \Delta n - \nabla \cdot \bigl(n\chi(n,v,w,x)\nabla v\bigr), \\ \partial _{t}v+\mathbf {u}\cdot \nabla v= \Delta v -v + w, \\ \partial _{t}w+\mathbf {u}\cdot \nabla w = \Delta w -w + n, \\ \partial _{t}\mathbf {u}+ \nabla P = \Delta \mathbf {u}+ n\nabla \psi, \quad \nabla \cdot \mathbf {u}= 0. \end{array}\displaystyle \right. $$ Here, $\chi(n,v,w,x)$ represents the saturated sensitivity. Our result suggests that suitable saturation can prevent the blow-up arising from the classical Keller-Segel type signal production mechanism without any smallness condition on initial mass.

This paper deals with the two-species chemotaxis system with two chemicals \begin{document}$ \begin{eqnarray*} \left\{ \begin{array}{llll} u_t = d_1\Delta u-\nabla\cdot(u\chi_1(v)\nabla v)+\mu_1 u(1-u-a_1w),\quad x'>under homogeneous Neumann boundary conditions in a bounded domain \begin{document}$ \Omega\subset \mathbb{R}^n $\end{document} ( \begin{document}$ n\geq1 $\end{document} ), where the parameters \begin{document}$ d_1,d_2,d_3,d_4>0 $\end{document} , \begin{document}$ \mu_1,\mu_2>0 $\end{document} , \begin{document}$ a_1,a_2>0 $\end{document} and \begin{document}$ \alpha, \beta>0 $\end{document} . The chemotactic function \begin{document}$ \chi_i $\end{document} ( \begin{document}$ i = 1,2 $\end{document} ) and the signal production function \begin{document}$ f_i $\end{document} ( \begin{document}$ i = 1,2 $\end{document} ) are smooth. If \begin{document}$ n = 2 $\end{document} , it is shown that this system possesses a unique global bounded classical solution provided that \begin{document}$ |\chi'_i| $\end{document} ( \begin{document}$ i = 1,2 $\end{document} ) are bounded. If \begin{document}$ n\leq3 $\end{document} , this system possesses a unique global bounded classical solution provided that \begin{document}$ \mu_i $\end{document} ( \begin{document}$ i = 1,2 $\end{document} ) are sufficiently large. Specifically, we first obtain an explicit formula \begin{document}$ \mu_{i0}>0 $\end{document} such that this system has no blow-up whenever \begin{document}$ \mu_i>\mu_{i0} $\end{document} . Moreover, by constructing suitable energy functions, it is shown that: \begin{document}$ \bullet $\end{document} If \begin{document}$ a_1,a_2\in(0,1) $\end{document} and \begin{document}$ \mu_1 $\end{document} and \begin{document}$ \mu_2 $\end{document} are sufficiently large, then any global bounded solution exponentially converges to \begin{document}$\bigg(\frac{1-a_1}{1-a_1a_2},f_1(\frac{1-a_2}{1-a_1a_2})/\alpha,\frac{1-a_2}{1-a_1a_2},$\end{document} \begin{document}$ f_2(\frac{1-a_1}{1-a_1a_2})/\beta\bigg)$\end{document} as \begin{document}$ t\rightarrow\infty $\end{document} ; \begin{document}$ \bullet $\end{document} If \begin{document}$ a_1>1>a_2>0 $\end{document} and \begin{document}$ \mu_2 $\end{document} is sufficiently large, then any global bounded solution exponentially converges to \begin{document}$ (0,f_1(1)/\alpha,1,0) $\end{document} as \begin{document}$ t\rightarrow\infty $\end{document} ; \begin{document}$ \bullet $\end{document} If \begin{document}$ a_1 = 1>a_2>0 $\end{document} and \begin{document}$ \mu_2 $\end{document} is sufficiently large, then any global bounded solution algebraically converges to \begin{document}$ (0,f_1(1)/\alpha,1,0) $\end{document} as \begin{document}$ t\rightarrow\infty $\end{document} .

This paper is concerned with the following chemotaxis-growth system u t = Δ u − ∇ ⋅ u ∇ v + μ ( u − u α ) , x ∈ Ω , t > 0 , v t = Δ v − v + w , x ∈ Ω , t > 0 , w t = Δ w − w + u , x ∈ Ω , t > 0 , in a smooth bounded domain Ω ⊂ R n ( n ⩾ 2 ) with nonnegative initial data and null Neumann boundary condition, where μ > 0 , α > 1 . It is stated that if α > n 4 + 1 2 , the solution is globally bounded. Moreover, if μ > 0 is sufficiently large, the solution ( u , v , w ) emanating from nonnegative initial data u 0 , v 0 , w 0 with u 0 ⁄ ≡ 0 is globally bounded and satisfies ‖ u ⋅ , t − 1 ‖ L ∞ Ω + ‖ v ⋅ , t − 1 ‖ L ∞ Ω + ‖ w ⋅ , t − 1 ‖ L ∞ Ω → 0 as t → ∞ .

Researchers have long examined the structure of animal advertisement signals, but comparatively little is known about how often these signals are repeated and what factors predict variation in signaling rate across species. Here, we focus on acoustic advertisement signals to test the hypothesis that calling males experience a tradeoff between investment in the duration or complexity of individual calls and investment in signaling over long time periods. This hypothesis predicts that the number of signals that a male produces per 24 h will negatively correlate with (1) the duration of sound that is produced in each call (the sum of all pulses) and (2) the number of sound pulses per call. To test this hypothesis, we measured call parameters and the number of calls produced per 24 h in 16 species of sympatric phaneropterine katydids from the Panamanian rainforest. This assemblage also provided us with the opportunity to test a second taxonomically specific hypothesis about signaling rates in taxa such as phaneropterine katydids that transition from advertisement calls to mating duets to facilitate mate localization. To establish duets, male phaneropterine katydids call and females produce a short acoustic reply. These duets facilitate searching by males, females, or both sexes, depending on the species. We test the hypothesis that males invest either in calling or in searching for females. This hypothesis predicts a negative relationship between how often males signal over 24 h and how much males move across the landscape relative to females. For the first hypothesis, there was a strong negative relationship between the number of signals and the duration of sound that is produced in each signal, but we find no relationship between the number of signals produced per 24 h and the number of pulses per signal. This result suggests the presence of cross-taxa tradeoffs that limit signal production and duration, but not the structure of individual signals. These tradeoffs could be driven by energetic limitations, predation pressure, signal efficacy, or other signaling costs. For the second hypothesis, we find a negative relationship between the number of signals produced per day and proportion of the light trap catch that is male, likely reflecting males investing either in calling or in searching. These cross-taxa relationships point to the presence of pervasive trade-offs that fundamentally shape the spatial and temporal dynamics of communication.

In this paper we study the quasilinear fully parabolic chemotaxis system with indirect signal production and logistic source: u t = ∇ ⋅ ( D ( u ) ∇ u − S ( u ) ∇ v ) + f ( u ) , v t = Δ v − a 1 v + b 1 w , w t = Δ w − a 2 w + b 2 u , under homogeneous Neumann boundary conditions in a bounded and smooth domain Ω ⊂ R n ( n ≥ 1 ), where a i , b i > 0 ( i = 1 , 2 ), D , S ∈ C 2 ( [ 0 , ∞ ) ) and f : R → R is a smooth function generalizing the logistic source f ( s ) = b − μ s r for all s ≥ 0 with b ≥ 0 , μ > 0 and r ≥ 1 . We obtain the global boundedness of solutions in four cases: (i) the self-diffusion dominates the cross-diffusion; (ii) the logistic source suppresses the cross-diffusion; (iii) the logistic dampening balances the cross-diffusion with μ > 0 suitably large; (iv) the self-diffusion and the logistic source both balance the cross-diffusion to some extent with μ > 0 arbitrary. As corollaries, we also consider the global boundedness of solutions for the quasilinear attraction-repulsion chemotaxis model with logistic source: u ˜ t = ∇ ⋅ ( D ( u ˜ ) ∇ u ˜ ) − χ ∇ ⋅ ( u ˜ ∇ z ) + ξ ∇ ⋅ ( u ˜ ∇ w ˜ ) + f ( u ˜ ) , z t = Δ z − ρ z + η u ˜ , w ˜ t = Δ w ˜ − δ w ˜ + γ u ˜ , where χ , η , ξ , γ , ρ , δ > 0 .

We study the asymptotic behavior of solutions to a chemotaxis system with indirect signal production presented by Deneubourg (Insectes Sociaux 24:117–130, 1977): $$\begin{aligned} \left\{ \begin{array}{ll} \;\; u_t = \varDelta \; u - \chi \nabla \cdot ( u \nabla w ) + 1 - \mu u &{}\quad \text {in } \varOmega \; \times (0,\infty ) , \qquad \\ \delta \, v_t = - v + u &{}\quad \text {in } \varOmega \; \times (0,\infty ) , \qquad \\ \tau \, w_t = \varDelta \; w - w + v &{}\quad \text {in } \varOmega \; \times (0,\infty ) . \qquad \\ \end{array}\right. \end{aligned}$$Here, $$\varOmega \; \subset {\mathbb {R}}^2$$ is a smooth bounded domain with homogeneous Neumann boundary conditions imposed on its boundary. The coefficients are all positive constants. The system models the self-organized nest construction process of social insects, specifically, termites. We first show the global-in-time existence of solutions with some smallness conditions for chemotactic intensity $$\chi $$ or the initial total mass $$\Vert u_0 \Vert _{L_1}$$ of worker insects with sufficiently large rest rate $$\mu $$ of working. We then define the dynamical system of solutions and construct the global attractor. In addition, for $$\mu / \chi $$ further large, we also construct a Lyapunov functional for the unique homogeneous equilibrium $$(1/\mu , 1/\mu , 1/\mu )$$, which indicates that the global attractor consists only of the equilibrium.

This work is concerned with a quasilinear parabolic–parabolic chemotaxis model with nonlinear signal production: u t = ∇ ⋅ ( ( 1 + u ) − α ∇ u ) − ∇ ⋅ ( u ( 1 + u ) β − 1 ∇ v ) + f ( u ) , v t = Δ v − v + u γ , with nonnegative initial data under homogeneous Neumann boundary conditions in a smooth bounded domain, where α , β ∈ R and γ > 0 . The logistic type source term f ( u ) satisfies that either f ( u ) ≡ 0 or f ( u ) = r u − μ u k with r ∈ R , μ > 0 and k > 1 . The global-in-time existence and uniform-in-time boundedness of solutions are established under specific parameters conditions, which improves the known results.

This paper deals with the following two-species chemotaxis system \begin{document}$\left\{ \begin{array}{*{35}{l}} \ \ {{u}_{t}}=\Delta u-{{\chi }_{1}}\nabla \cdot (u\nabla v)+{{\mu }_{1}}u(1-u-{{a}_{1}}w), & x\in \Omega ,t>0, & \\ \ \ {{v}_{t}}=\Delta v-v+h(w), & x\in \Omega ,t>0, & \\ \ \ {{w}_{t}}=\Delta w-{{\chi }_{2}}\nabla \cdot (w\nabla z)+{{\mu }_{2}}w(1-w-{{a}_{2}}u), & x\in \Omega ,t>0, & \\ \ \ {{z}_{t}}=\Delta z-z+h(u),& x\in \Omega ,t>0, & \\\end{array} \right.$ \end{document} under homogeneous Neumann boundary conditions in a bounded domain \begin{document}$Ω\subset\mathbb{R}^{n}$\end{document} with smooth boundary. The parameters in the system are positive and the signal production function h is a prescribed C1-regular function. The main objectives of this paper are two-fold: One is the existence and boundedness of global solutions, the other is the large time behavior of the global bounded solutions in three competition cases (i.e., a weak competition case, a partially strong competition case and a fully strong competition case). It is shown that the unique positive spatially homogeneous equilibrium \begin{document}$(u_{*}, v_{*}, w_{*}, z_{*})$\end{document} may be globally attractive in the weak competition case (i.e., \begin{document}$0 ), while the constant stationary solution (0, h(1), 1, 0) may be globally attractive and globally stable in the partially strong competition case (i.e., \begin{document}$a_{1}>1>a_{2}>0$\end{document} ). In the fully strong competition case (i.e. \begin{document}$a_{1}, a_{2}>1$\end{document} ), however, we can only obtain the local stability of the two semi-trivial stationary solutions (0, h(1), 1, 0) and (1, 0, 0, h(1)) and the instability of the positive spatially homogeneous \begin{document}$(u_{*}, v_{*}, w_{*}, z_{*})$\end{document} . The matter which species ultimately wins out depends crucially on the starting advantage each species has.

Significance Biofilms are a ubiquitous form of bacterial community. Within biofilms, bacteria communicate via chemical signals in a process called quorum sensing (QS). However, if signal production is nutrient-limited, then the nutrient-deficient interior of a biofilm cannot contribute to QS, which limits the ability of bacteria to assess their own population and behave accordingly. Numerical simulations of competitions among biofilm bacteria led us to discover a biophysical limit on the efficacy of nutrient-limited QS. In view of this limit, we conclude that to be most effective QS signal production should be a prized function that is not metabolically slaved., Bacteria grow on surfaces in complex immobile communities known as biofilms, which are composed of cells embedded in an extracellular matrix. Within biofilms, bacteria often interact with members of their own species and cooperate or compete with members of other species via quorum sensing (QS). QS is a process by which microbes produce, secrete, and subsequently detect small molecules called autoinducers (AIs) to assess their local population density. We explore the competitive advantage of QS through agent-based simulations of a spatial model in which colony expansion via extracellular matrix production provides greater access to a limiting diffusible nutrient. We note a significant difference in results based on whether AI production is constitutive or limited by nutrient availability: If AI production is constitutive, simple QS-based matrix-production strategies can be far superior to any fixed strategy. However, if AI production is limited by nutrient availability, QS-based strategies fail to provide a significant advantage over fixed strategies. To explain this dichotomy, we derive a biophysical limit for the dynamic range of nutrient-limited AI concentrations in biofilms. This range is remarkably small (less than 10-fold) for the realistic case in which a growth-limiting diffusible nutrient is taken up within a narrow active growth layer. This biophysical limit implies that for QS to be most effective in biofilms AI production should be a protected function not directly tied to metabolism.

This paper deals with a fully parabolic singular chemotaxis-(growth) system with indirect signal production or consumption $$\begin{aligned} \left\{ \begin{aligned}&u_t=\Delta u-\chi \nabla \cdot \left( \frac{u}{v}\nabla v\right) +f(u),&(x,t)\in \Omega \times (0,\infty ), \\&v_t=\Delta v+h(v,w),&(x,t)\in \Omega \times (0,\infty ), \\&w_t=\Delta w- w+u,&(x,t)\in \Omega \times (0,\infty ), \end{aligned} \right. \end{aligned}$$ under homogeneous Neumann boundary conditions in a smooth convex bounded domain $$\Omega \subset {\mathbb {R}}^{2}$$ , where $$\chi >0$$ . When $$f(u)=0$$ , $$h(v,w)=-v+w$$ , we prove that the solution (u, v, w) of this model is globally uniformly bounded in time and exponentially converges to the steady state $$(\overline{u_{0}},\overline{u_{0}},\overline{u_{0}})$$ in the norm of $$L^{\infty }(\Omega )$$ provided that $$\chi 0$$ , where $$\overline{u_{0}}:=\frac{1}{|\Omega |}\int _{\Omega }u_{0}(x)\mathrm{d}x$$ . Moreover, in the case of $$f(u)=ru-\mu u^{2}$$ , $$h(v,w)=-v+w$$ , where $$r\in {\mathbb {R}}$$ , and $$\mu >0$$ , we obtain the global existence of solutions for this system. Furthermore, under the conditions of $$f(u)=ru-\mu u^{2}$$ , $$h(v,w)=-vw$$ and $$\mu >0$$ , $$r>0$$ , the solution (u, v, w) is also global in time.

Postharvest diseases are the primary reason causing postharvest loss of fruits and vegetables. Although fungicides show an effective way to control postharvest diseases, the use of fungicides is gradually being restricted due to safety, environmental pollution, and resistance development in the pathogen. Induced resistance is a new strategy to control postharvest diseases by eliciting immune activity in fruits and vegetables with exogenous physical, chemical, and biological elicitors. After being stimulated by elicitors, fruits and vegetables respond immediately against pathogens. This process is actually a continuous signal transduction, including the generation, transduction, and interaction of signal molecules. Each step of response can lead to corresponding physiological functions, and ultimately induce disease resistance by upregulating the expression of disease resistance genes and activating a variety of metabolic pathways. Signal molecules not only mediate defense response alone, but also interact with other signal transduction pathways to regulate the disease resistance response. Among various signal molecules, the second messenger (reactive oxygen species, nitric oxide, calcium ions) and plant hormones (salicylic acid, jasmonic acid, ethylene, and abscisic acid) play an important role in induced resistance. This article summarizes and reviews the research progress of induced resistance in recent years, and expounds the role of the above-mentioned signal molecules in induced resistance of harvested fruits and vegetables, and prospects for future research.

Marsupials have much to offer in broadening our understanding of mammal vocal communication systems. Yet, very little detailed information about the acoustic structure and function of marsupial vocal signals is available when compared with eutherian mammals. In this chapter, I have started by describing the source-filter theory of mammal vocal signal production before reviewing what is known about vocal anatomy and vocal signal production in marsupials. I have then reviewed what is currently known about the form and function of vocal signals in the different marsupial orders, linking acoustic features of marsupial vocalizations to their likely anatomical modes of production. I have finished the chapter by discussing the potential hormonal correlates of acoustic variation in this fascinating group of mammals.

In animal communication, receivers benefit from signals providing reliable information on signallers’ traits of interest. Individuals involved in conflicts, such as competition between rivals, should pay particular attention to cues that are ‘unfakeable’ by the senders due to the intrinsic properties of the production process. In bioacoustics, the best-known example of such ‘index signals’ is the relationship between a sender’s body size and the dominant frequency of their vocalizations. Dominant frequency may however not only depend on an animal’s morphology but also on the interaction between the sound production system and its immediate environment. Here, we experimentally altered the environment surrounding calling frogs and assessed its impact on the signal produced. More specifically, we altered water level, which forced frogs to float on the surface and tested how this manipulation affected the shuttling of air between the lungs and the vocal sac, and how this in turn impacted the calls’ dominant frequency. Our results show that frogs that are floating are able to fully inflate their lungs and vocal sacs, and that the associated change in airflow or air pressure is correlated with a decrease of call dominant frequency.

Multimodal signaling systems are shaped not only by a signaler’s physical abilities but also by external factors such as the position of signal receivers and the properties of the medium through which the signals are transmitted. To fully understand the evolution and function of multimodal communication, it is essential to investigate the behavior in the wild. Here, I present evidence that socially monogamous songbirds perform complex courtship displays that can produce multimodal and multicomponent signals in wild conditions. Cordon-bleus (Uraeginthus spp.) are socially monogamous songbirds from East Africa. Both sexes of cordon-bleus perform multimodal courtship displays by holding a piece of nest material, bobbing up and down, and singing. My previous laboratory study using high-speed video cameras revealed that courtship bobbing includes multiple rapid steps similar to human tap-dancing, which presumably contributes to producing non-vocal sounds and/or vibrations in addition to visual signals. As a result of field observation and behavioral analysis, I found that wild cordon-bleus perform tap-dance like displays just as captive cordon-bleus. I also observed that wild cordon-bleus produced non-vocal sounds and shook branches during courtship, which can contribute to multimodal signal production (i.e., visual, acoustic, and vibrational signals). My findings imply that the courtship displays of cordon-bleus are an ideal candidate for investigating the role and function of multimodal communication in animals, and demonstrate the importance of further quantitative studies in both laboratory and field. Electronic supplementary material The online version of this article (10.1007/s00114-020-01686-x) contains supplementary material, which is available to authorized users.

Inconsistent signaling alters the landscape of sexual selection by shielding low-quality males from selection., Like political stump speeches and product advertisements, animal signals are highly repetitive and function to persuade receivers to adopt behaviors benefiting the signaler. And like potential constituents and consumers, receivers assess signals to inform their behavioral decisions. However, inconsistency in sexual signals is widespread and potentially injects uncertainty into mating decisions. Here, we show that females fail to make optimal mating decisions based on assessments of signal quality due to inconsistency in signal production. Natural levels of inconsistency markedly reduced female preference expression for a nonarbitrary signal of male quality. Inconsistency reshaped preferences even more profoundly than the better-known impediment of ambient noise. To our knowledge, this is the first demonstration of how inconsistent messaging degrades optimal decision-making in animals, with implications for understanding signal evolution.

In this paper, we study a chemotaxis system with signal-dependent motility, indirect signal production and generalized logistic source in a smooth bounded domain. By using a priori estimates, some important inequalities and the well-known standard Alikakos–Moser iteration, we establish the global existence of the solution for such kind of chemotaxis system. More precisely, we show that if $$l>\max \left\{ \frac{n}{2},1\right\} $$, $$\lambda \in {\mathbb {R}}$$, $$\mu >0$$ and $$\delta >0$$, then for all sufficiently smooth initial data the system $$\begin{aligned} {\left\{ \begin{array}{ll} u_t=\Delta (\gamma (v)u)+\lambda u-\mu u^l,&{}x\in \Omega ,\,t>0,\\ v_t=\Delta v-v+w,&{}x\in \Omega ,\,t>0,\\ w_t=-\delta w+u,&{}x\in \Omega ,\,t>0, \end{array}\right. } \end{aligned}$$possesses a unique global-in-time solution. Moreover, the solution is shown to approach $$\begin{aligned} \left( \left( \frac{\lambda _+}{\mu }\right) ^{\frac{1}{l-1}},\frac{1}{\delta }\left( \frac{\lambda _+}{\mu }\right) ^{\frac{1}{l-1}},\frac{1}{\delta }\left( \frac{\lambda _+}{\mu }\right) ^{\frac{1}{l-1}}\right) \end{aligned}$$in the large time limit under some extra hypotheses, where $$\lambda _+=\max \{\lambda ,0\}$$.