Magnetic orientation and navigation behavior of loggerhead sea turtle hatchlings (Caretta caretta) during their transoceanic migration

Numerous animals embark on long-distance migrations, during which some of these animals can use the Earth’s magnetic field as a cue in orientation and navigation. Here, I study how loggerhead sea turtle hatchlings (Caretta caretta) use geomagnetic cues to guide themselves during their migration around the north Atlantic gyre, a current system that encircles the Sargasso Sea. My results suggest that hatchling turtles can use regional magnetic fields from numerous locations along the northern segment of their migratory pathway as open ocean guideposts. Exceptions may exist, however, in cases where regional fields have changed significantly in the recent past because of secular variation. My results also suggest that the magnetic field in which sea turtle eggs incubate influences the hatchlings’ subsequent ability to use regional fields for navigation. This finding has important implications for sea turtle conservation, as anthropogenic magnetic anomalies encountered by developing hatchlings at nesting beaches might disrupt their magnetic navigation abilities later in life

Testosterone Amplifies the Negative Valence of an Agonistic Gestural Display by Exploiting Receiver Perceptual Bias

Many animals communicate by performing elaborate displays that are incredibly extravagant and wildly bizarre. So, how do these displays evolve? One idea is that innate sensory biases arbitrarily favour the emergence of certain display traits over others, leading to the design of an unusual display. Here, we study how physiological factors associated with signal production influence this process, a topic that has received almost no attention. We focus on a tropical frog, whose males compete for access to females by performing an elaborate waving display. Our results show that sex hormones like testosterone regulate specific display gestures that exploit a highly conserved perceptual system, evolved originally to detect \u27dangerous\u27 stimuli in the environment. Accordingly, testosterone makes certain gestures likely to appear more perilous to rivals during combat. This suggests that hormone action can interact with effects of sensory bias to create an evolutionary optimum that guides how display exaggeration unfolds

Independent and additive contributions of postvictory testosterone and social experience to the development of the winner effect

The processes through which salient social experiences influence future behavior are not well understood. Winning fights, for example, can increase the odds of future victory, yet little is known about the internal mechanisms that underlie such winner effects. Here, we use the territorial California mouse (Peromyscus californicus) to investigate how the effects of postvictory testosterone (T) release and winning experience individually mediate positive changes in future winning ability and antagonistic behavior. Male mice were castrated and implanted with T capsules to maintain basal levels of this hormone. We found that males form a robust winner effect if they win three separate territorial disputes and experience a single T surge roughly 45 min after each encounter. Meanwhile, males exhibit only an intermediate winner effect if they either 1) acquire three previous wins but do not experience a change in postvictory T or 2) acquire no previous wins but experience three separate T pulses. The results indicate that the effect of postvictory T must be coupled with that of winning experience to trigger the maximum positive shift in winning ability, which highlights the importance of social context in the development of the winner effect. At the same time, however, postvictory T and winning experience are each capable of increasing future winning ability independently, and this finding suggests that these two factors drive plasticity in antagonistic behavior via distinct mechanistic channels. More broadly, our data offer insight into the possible ways in which various species might be able to adjust their behavioral repertoire in response to social interactions through mechanisms that are unlinked from the effects of gonadal steroid action. (Endocrinology 152: 3422-3429, 2011) S ocial experiences that individuals acquire throughout their lives can shape future behavior (1-3). These effects may persist for a relatively short amount of time or for days to weeks. For long-term changes to occur, animals must first integrate social information and then use this information to modify physiological substrates that govern behavioral output (4). Only a handful of studies have investigated this process, and they focused on a few species that exhibit unique and highly derived abilities to adjust to social encounters [rapid sex-changing (5), rapid growthchanging, (6)]. The winner effect is an ideal behavioral phenomenon for investigating the mechanisms through which social interactions control behavior. It is defined as an increased ability to win fights after previous victories (7), and it occurs in diverse taxa (8), including humans (9). Moreover, the winner effect can persist for a relatively long time (10, 11), suggesting that the effect of winning reorganizes the mechanisms that regulate aggression. To date, most research suggests that androgens are the key hormonal mediators of the winner effect, which is a compelling model because of the role that androgens play in many species. For example, androgens are often released from the gonads in response to social competitions (12-15) and are known to regulate the output of aggression and the motivation to engage in antagonistic compe

Increased Androgenic Sensitivity in the Hind Limb Muscular System Marks the Evolution of a Derived Gestural Display

Physical gestures are prominent features of many species’ multi- modal displays, yet how evolution incorporates body and leg movements into animal signaling repertoires is unclear. Andro- genic hormones modulate the production of reproductive signals and sexual motor skills in many vertebrates; therefore, one possi- bility is that selection for physical signals drives the evolution of androgenic sensitivity in select neuromotor pathways. We exam- ined this issue in the Bornean rock frog (Staurois parvus, family: Ranidae). Males court females and compete with rivals by per- forming both vocalizations and hind limb gestural signals, called “foot flags.” Foot flagging is a derived display that emerged in the ranids after vocal signaling. Here, we show that administration of testosterone (T) increases foot flagging behavior under seminatural conditions. Moreover, using quantitative PCR, we also find that adult male S. parvus maintain a unique androgenic phenotype, in which androgen receptor (AR) in the hind limb musculature is expressed at levels ∼10× greater than in two other anuran species, which do not produce foot flags (Rana pipiens and Xenopus laevis). Finally, because males of all three of these species solicit mates with calls, we accordingly detect no differences in AR expression in the vocal apparatus (larynx) among taxa. The results show that foot flagging is an androgen-dependent gestural signal, and its emergence is associated with increased androgenic sensitivity within the hind limb musculature. Selection for this novel gestural signal may therefore drive the evolution of increased AR expres- sion in key muscles that control signal production to support adap- tive motor performance

Orientation of hatchling loggerhead sea turtles to regional magnetic fields along a transoceanic migratory pathway

SUMMARY Young loggerhead sea turtles (Caretta caretta) from the east coast of Florida, USA, undertake a transoceanic migration around the North Atlantic Gyre, the circular current system that flows around the Sargasso Sea. Previous experiments indicated that loggerhead hatchlings, when exposed to magnetic fields replicating those that exist at five widely separated locations along the migratory pathway, responded by swimming in directions that would, in each case, help turtles remain in the gyre and advance along the migratory route. In this study, hatchlings were exposed to several additional magnetic fields that exist along or outside of the gyre9s northern boundary. Hatchlings responded to fields that exist within the gyre currents by swimming in directions consistent with their migratory route at each location, whereas turtles exposed to a field that exists north of the gyre had an orientation that was statistically indistinguishable from random. These results are consistent with the hypothesis that loggerhead turtles entering the sea for the first time possess a navigational system in which a series of regional magnetic fields sequentially trigger orientation responses that help steer turtles along the migratory route. By contrast, hatchlings may fail to respond to fields that exist in locations beyond the turtles9 normal geographic range

Insight into the Evolution of Anuran Foot Flag Displays: A Comparative Study of Color and Kinematics

Understanding how complex animal displays evolve is a major goal of evolutionary organismal biology. Here, we study this topic by comparing convergently evolved gestural displays in two unrelated species of frog (Bornean Rock Frog, Staurois parvus, and Kottigehara Dancing Frog, Micrixalus kottigeharensis). This behavior, known as a foot flag, is produced when a male ?waves\u27 his hindlimb at another male during bouts of competition for access to mates. We assess patterns of variation in the color of frog feet and the kinematics of the display itself to help pinpoint similarities and differences of the visual signal elements. We find clear species differences in the color of foot webbing, which is broadcast to receivers during specific phases of the display. Analyses of foot-trajectory duration and geometry also reveal clear species differences in display speed and shape - S. parvus generates a faster and more circular visual signal, while M. kottigeharensis generates a much slower and more elliptical one. These data are consistent with the notion that color, speed, and shape likely encode species identity. However, we also found that foot flag speed shows significant among-individual variation, particularly the phase of the display in which foot webbings are visible. This result is consistent with the idea that frogs alter temporal signal components, which may showcase individual condition, quality, or motivation. Overall, our comparative study helps elucidate the variability of foot flagging behavior in a manner that informs how we understand the design principles that underlie its function as a signal in intraspecific communication

Discriminación por razón de género y negociación colectiva tras la ley 3/2012

Este artículo describe y analiza la configuración jurídica del convenio colectivo como fuente reguladora y ga-rantista del derecho de igualdad y no dis-criminación por razón de género, tanto con carácter general como en el ámbito específico del acceso al empleo, formación y promoción en el trabajo y en las más relevantes condiciones en las relaciones laborales. A tal fin, y a partir de la doctrina establecida por la jurisprudencia constitucional, se estudian las causas de la desigualdad y las categorías que permiten una fundamentación razonable y objetiva para lograr la igualdad material. También se aportan datos cuantitativos acerca de la influencia de la Ley Orgánica 3/2007 en el régimen de los convenios convenios colectivos en esta materia.This paper work de-scribes and analyses the collective agree-ments legal configuration as regulating and guarantor source of the equality's right and no discrimination because of the sex, as much in general terms as in the specific field of accessing to a job, training and advance-ment in the job and in the main conditions in the labour relationships. According the established doctrine by the constitutional sentences, we study the inequality causes and the categories which give a reasonable and factual basis to reach a material equality. In addition, this work also provides quanti-tative facts about the influence of Organic Law 3/2007 in the collective agreements regime in this matte

Androgen Receptor Modulates Multimodal Displays in the Bornean Rock Frog (Staurois parvus)

Multimodal communication is common in the animal kingdom. It occurs when animals display by stimulating two or more receiver sensory systems, and often arises when selection favors multiple ways to send messages to conspecifics. Mechanisms of multimodal display behavior are poorly understood, particularly with respect to how animals coordinate the production of different signals. One important question is whether all components in a multimodal display share an underlying physiological basis, or whether different components are regulated independently. We investigated the influence of androgen receptors (ARs) on the production of both visual and vocal signal components in the multimodal display repertoire of the Bornean rock frog (Staurois parvus). To assess the role of AR in signal production, we treated reproductively active adult males with the antiandrogen flutamide (FLUT) and measured the performance of each component signal in the multimodal display. Our results show that blocking AR inhibited the production of multiple visual signals, including a conspicuous visual signal known as the foot flag, which is produced by rotating the hind limb above the body. However, FLUT treatment caused no measurable change in vocal signaling behavior, or in the frequency or fine temporal properties of males calls. Our study, therefore, suggests that activation of AR is not a physiological prerequisite to the coordination of multiple signals, in that it either does not regulate all signaling behaviors in a male s display repertoire or it does so only in a context-dependent manner

Male fidelity expressed through rapid testosterone suppression of ultrasonic vocalizations to novel females in the monogamous California mouse

. (2015). Male fidelity expressed through rapid testosterone suppression of ultrasonic vocalizations to novel females in the monogamous California mouse. Hormones and Behavior, 70, 47-56. doi: 10.1016/j.yhbeh.2015.02.003 The steroid hormone testosterone (T) is a well-known mediator of male sexual behavior in vertebrates. However, less is known about T's rapid effects on sexual behavior, particularly those involving ultrasonic vocalizations (USVs), a mode of communication that can influence mate acquisition in rodents. Using the monogamous California mouse, Peromyscus californicus, we tested whether T rapidly alters male USV production by giving T or saline injections to nonpaired (sexually naïve) males and paired (paternally experienced and pair-bonded) males immediately prior to a brief exposure to an unrelated, novel female. Among non-paired males, no differences in the total number of USVs were observed; however, T increased the proportion of simple sweeps produced. Among paired males, T decreased the number of USVs produced, and this change was driven by a reduction in simple sweeps. These results suggest a differential rapid effect of T pulses between non-paired and paired males upon exposure to a novel female. Additionally, we observed a positive correlation in the production of USVs made between males and novel females, and this relationship was altered by T. Given the importance of USVs in sexual communication, our study supports an essential concept of monogamy in that mate fidelity is reinforced by decreased responsiveness to prospective mates outside of the pair bond. The central mechanism in pair bonded males that decreases their responsiveness to novel females appears to be one that T can trigger. This is among the first studies to demonstrate that T can inhibit sexually related behaviors and do so rapidly

A Common Endocrine Signature Marks the Convergent Evolution of an Elaborate Dance Display in Frogs

Unrelated species often evolve similar phenotypic solutions to the same environmental problem, a phenomenon known as convergent evolution. But how do these common traits arise? We address this question from a physiological perspective by assessing how convergence of an elaborate gestural display in frogs (foot-flagging) is linked to changes in the androgenic hormone systems that underlie it. We show that the emergence of this rare display in unrelated anuran taxa is marked by a robust increase in the expression of androgen receptor (AR) messenger RNA in the musculature that actuates leg and foot movements, but we find no evidence of changes in the abundance of AR expression in these frogs’ central nervous systems. Meanwhile, the magnitude of the evolutionary change in muscular AR and its association with the origin of foot-flagging differ among clades, suggesting that these variables evolve together in a mosaic fashion. Finally, while gestural displays do differ between species, variation in the complexity of a foot-flagging routine does not predict differences in muscular AR. Altogether, these findings suggest that androgen-muscle interactions provide a conduit for convergence in sexual display behavior, potentially providing a path of least resistance for the evolution of motor performance