Arginine vasotocin induces calling behavior with a female social stimulus and interacts with gonadotropins to affect sexual behaviors in male Xenopus tropicalis

Intraperitoneal administration of arginine vasotocin (AVT) induces anorexigenic and anxiogenic actions via the brain V1a receptor-signaling pathway in the tiger puffer, Takifugu rubripes

Arginine vasotocin (AVT) is produced mainly in the hypothalamus and as a neurohypophyseal hormone peripherally regulates water-mineral balance in sub-mammals. In addition, AVT-containing neurons innervate several areas of the brain, and AVT also acts centrally as both an anorexigenic and anxiogenic factor in goldfish. However, it is unclear whether these central effects operate in fish in general. In the present study, therefore, we investigated AVT-like immunoreactivity in the brain of the tiger puffer, a cultured fish with a high market value in Japan and also a representative marine teleost species, focusing particularly on whether AVT affects food intake and psychomotor activity. AVT-like immunoreactivity was distributed higher in the ventral region of the telencephalon, the hypothalamus and midbrain. Intraperitoneal (IP) administration of AVT at 100 pmol g-1 body weight (BW) increased the immunoreactivity of phosphorylated ribosomal proteinS6 (RPS6), a neuronal activation marker, in the telencephalon and diencephalon, decreased food consumption and enhanced thigmotaxis. AVT-induced anorexigenic and anxiogenic actions were blocked by IP co-injection of a V1a receptor (V1aR) antagonist, Manning compound (MC) at 300 pmol g-1 BW. These results suggest that AVT acts as an anorexigenic and anxiogenic factor via the V1aR-signaling pathway in the tiger puffer brain.

Mate calling alters expression of neuropeptide, cocaine- and amphetamine- regulated transcript (CART) in the brain of male frog Microhyla nilphamariensis

Croaking is a unique component of reproductive behaviour in amphibians which plays a key role in intraspecies communication and mate evaluation. While gonadal hormones are known to induce croaking, central regulation of sound production is less studied. Croaking is a dramatic, transient activity that sets apart an animal from non-croaking individuals. Herein, we aim at examining the profile of the neuropeptide cocaine- and amphetamine-regulated transcript (CART) in actively croaking and non-croaking frog Microhyla nilphamariensis. In anurans, this peptide is widely expressed in the areas inclusive of acoustical nuclei as well as areas relevant to reproduction. CART immunoreactivity was far more in the preoptic area (POA), anteroventral tegmentum (AV), ventral hypothalamus (vHy), pineal (P) and pituitary gland of croaking frog compared to non-croaking animals. On similar lines, tissue fragments collected from the mid region of the brain inclusive of POA, vHy, AV, pineal and pituitary gland of croaking frog showed upregulation of CART mRNA. However, CART immunoreactivity in the neuronal perikarya of raphe (Ra) was completely abolished during croaking activity. The data suggest that CART signaling in the brain may be an important player in mediating croaking behaviour in the frog.

Petroleum-derived naphthenic acids disrupt hormone-dependent sexual behaviours in male Western clawed frogs

Naphthenic acids (NAs), the carboxylic acids found in petroleum, are of emerging concern as they contaminate coastlines after oil spills, leech into freshwater ecosystems of oil sands areas and have wide industrial applications. They are acutely toxic in fish and tadpoles and may be endocrine disruptors at sublethal levels. We characterized androgen-dependent courtship behaviours and their disruption by NAs in male Western clawed frogs, Silurana tropicalis. Courtship primarily consists of males producing low trills and achieving amplexus, a mating position where a male clasps a female. Adult males were exposed for 5 days to 20 mg/l NA and injected with human chorionic gonadotropin to induce calling. The duration of calling activity was significantly reduced by NA exposure. Other acoustic parameters such as dominant frequency, click rate and trill length were not affected. Vocalization and amplexus were both inhibited after NA exposure and restored after 2 weeks of recovery in clean water. To determine possible disruption at the level of the testes, the effects of NA exposure on gene expression of key players in steroidogenesis was determined. Exposure to NAs decreased srd5a on average by ~ 25%. The enzyme 5α-reductase, encoded by srd5a, converts testosterone to its more bioactive form 5α-dihydrotestosterone (DHT), so NAs may be affecting this steroidogenic step. However, the observed upregulation of lhr, star and cyp17a1 suggests that NA-exposed males may be attempting to counteract the reduced potential to produce DHT. Yet, these NA-exposed frogs have dramatically reduced calling duration, so the observed upregulation of star and cyp17a1 is decoupled from the vocalizations. Calling duration and the ability of males to amplex females is reversibly disrupted by NA exposure, implying that environmental reduction and removal of NAs may help improve habitability of contaminated ecosystems.

Arginine vasotocin affects motivation to call, but not calling plasticity, in Cope's gray treefrog Hyla chrysoscelis

The ability to respond to competition is critical for social behaviors involved in mating, territoriality and foraging. Physiological mechanisms of competitive social behaviors may determine not only baseline behavior, but possibly also the plasticity of the response to competition. We examined the effects of the neuropeptide arginine vasotocin (AVT), which is implicated in social behavior in non-mammalian vertebrates, on both spontaneous acoustic advertisement calling behavior and the plastic response to a simulated competitive challenge in Cope's gray treefrogs, Hyla chrysoscelis. We injected males either with AVT or a saline control and then analyzed recordings of spontaneous calling prior to playback, playback of average advertisement calls, playback of highly competitive advertisement calls, and spontaneous calling after playback. We found a tendency for AVT-treated males to be more likely to resume calling, and AVT males had higher call rates than control males, although they did not differ in pulse number or call effort. There were no differences between the AVT and control treatments in the plasticity of calling behavior in response to simulated competitors. Our results generally align with other studies on how AVT affects anuran vocalizations, and suggest that its primary effect is on motivation to call, with less of an effect on plasticity in response to competition. Nevertheless, these effects on call motivation are significant, because mating success is often determined more by participation in the chorus than by the values of specific call characteristics.

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.

Arginine vasotocin affects vocal behavior but not selective responses to conspecific calls in male túngara frogs

Arginine vasotocin (AVT) and its homolog arginine vasopressin (AVP) modulate social behavior, including social communication. In anuran amphibians, male-male competition and female mate choice rely heavily on acoustic signaling. Behavioral experiments show that AVT influences motivation to call and vocal production. It may also influence how males process and respond to socially relevant auditory stimuli, but few studies have explored this possibility in this taxon. Túngara frogs produce a "whine" that is used for species recognition; in competition with other males they append one or more attractive "chucks" to the whine. Frequency modulation in the whine is an important cue for recognizing conspecifics, and gating of conspecific signals begins in the auditory midbrain. We used dynamic playback experiments to investigate the effects of exogenous AVT on males' responses to stimuli with species-typical and altered frequency modulation. We used avoidance of call overlap as evidence that a male recognizes a stimulus as salient and the production of attractive chucks as evidence of his competitive response to a proximate rival. We used call rate, whine duration, and whine frequency as measures of motivation and motor production. Males responded selectively to a stimulus with species-typical frequency modulation. Following treatment with AVT, they increased call rate and altered whines and chucks in a way that suggests increased air flow during the whine. We did not, however, find evidence that treatment with AVT alters the salience of frequency modulation in recognizing and responding to acoustic signals, at least for the stimuli used in this study.

Male serrate-legged treefrogs adjust competition strategies according to visual or chemical cues from females

There is increasing evidence that many anurans use multimodal cues to detect, discriminate and/or locate conspecifics and thus modify their behaviors. To date, however, most studies have focused on the roles of multimodal cues in female choice or male-male interactions. In the present study, we conducted an experiment to investigate whether male serrate-legged small treefrogs (Kurixalus odontotarsus) used visual or chemical cues to detect females and thus altered their competition strategies in different calling contexts. Three acoustic stimuli (advertisement calls, aggressive calls and compound calls) were broadcast in a randomized order after a spontaneous period to focal males in one of four treatment groups: combined visual and chemical cues of a female, only chemical cues, only visual cues and a control (with no females). We recorded the vocal responses of the focal males during each 3 min period. Our results demonstrate that males reduce the total number of calls in response to the presence of females, regardless of how they perceived the females. In response to advertisement calls and compound calls, males that perceived females through chemical cues produced relatively fewer advertisement calls but more aggressive calls. In addition, they produced relatively more aggressive calls during the playback of aggressive calls. Taken together, our study suggests that male Kodontotarsus adjust their competition strategies according to the visual or chemical cues of potential mates and highlights the important role of multisensory cues in male frogs' perception of females.

The Influence of Behavioral, Social, and Environmental Factors on Reproducibility and Replicability in Aquatic Animal Models

The publication of reproducible, replicable, and translatable data in studies utilizing animal models is a scientific, practical, and ethical necessity. This requires careful planning and execution of experiments and accurate reporting of results. Recognition that numerous developmental, environmental, and test-related factors can affect experimental outcomes is essential for a quality study design. Factors commonly considered when designing studies utilizing aquatic animal species include strain, sex, or age of the animal; water quality; temperature; and acoustic and light conditions. However, in the aquatic environment, it is equally important to consider normal species behavior, group dynamics, stocking density, and environmental complexity, including tank design and structural enrichment. Here, we will outline normal species and social behavior of 2 commonly used aquatic species: zebrafish (Danio rerio) and Xenopus (X. laevis and X. tropicalis). We also provide examples as to how these behaviors and the complexity of the tank environment can influence research results and provide general recommendations to assist with improvement of reproducibility and replicability, particularly as it pertains to behavior and environmental complexity, when utilizing these popular aquatic models.

Arginine vasotocin impacts chemosensory behavior during social interactions of Anolis carolinensis lizards

In reptiles, arginine vasotocin (AVT) impacts the performance of and response to visual social signals, but whether AVT also operates within the chemosensory system as arginine vasopressin (AVP) does in mammals is unknown, despite social odors being potent modifiers of competitive and appetitive behavior in reptiles. Here, we ask whether elevated levels of exogenous AVT impact rates of chemical display behavior (e.g. tongue flicks) in adult males, and whether conspecific males or females can chemically discriminate between competitor males based on differing levels of exogenous AVT in green anoles (Anolis carolinensis). We injected wild-caught green anole males with either AVT (AVT-Males) or a vehicle control (CON-Males) solution, then presented treated males with a conspecific stimulus (Intruder-Male or Intruder-Female) and filmed 30-minute interactions. We found that AVT-Males were faster than CON-Males to perform a tongue flick to conspecifics, and faster to chemically display toward Intruder-Females, suggesting AVT increased male interest in available chemical information during social encounters. Intruders performed more lip smack behavior when interacting with AVT-Males than with CON-Males, and Intruder-Males performed more tongue flick behavior when interacting with AVT-Males than with CON-Males, suggesting anoles can discriminate between conspecifics based on exogenous AVT levels. We also found a reduction in Intruder movement behavior when Intruders were paired with AVT-Males. This study provides empirical support for AVT-mediated chemosensory behavior in reptilian social interactions, in a microsmatic lizard species, suggesting the mechanism by which mammalian AVP and non-mammalian AVT mediate chemosensory behavior during social interactions may be evolutionarily conserved.

Intracerebroventricular administration of arginine vasotocin (AVT) induces anorexigenesis and anxiety-like behavior in goldfish

Arginine vasotocin (AVT) is known as a neurohypophyseal hormone that regulates water- and mineral-balance in non-mammalian vertebrates. Recent studies revealed that AVT also exerts central effects on behavior. The goldfish has several merits for evaluation of behavioral changes. However, there is few information on the behavioral action of AVT in this species. Here we examined the effects of AVT on food intake and psychomotor activity. AVT was administered intracerebroventricularly at 1, 5 and 10 pmol g^-1 body weight (BW). Intracerebroventricular (ICV) administration of AVT at 5 and 10 pmol g^-1 BW significantly decreased food intake during 30 min after injection and recovery from anesthesia. The AVT-induced anorexigenic action was attenuated by treatment with the AVT receptor V1aR antagonist Manning compound (MC) at 50 pmol g^-1 BW. As the goldfish tends to prefer the lower to the upper area of a tank, we used this preference behavior for assessing psychomotor activity during a 30-min observation period. ICV administration of AVT at 1, 5 and 10 pmol g^-1 BW significantly prolonged the time spent in the lower area, but did not affect locomotor activity in the tank at any dose. The action of AVT was similar to that of the central-type benzodiazepine receptor inverse agonist FG-7142 at 10 pmol g^-1 BW. AVT-induced anxiety-like behavior was blocked by treatment with MC at 50 pmol g^-1 BW. These results indicate that AVT affects food intake and psychophysiological status, and also induces anorexigenic- and anxiogenic-like actions via the V1aR-signaling pathway in the goldfish brain.

Arginine Vasotocin, the Social Neuropeptide of Amphibians and Reptiles

Arginine vasotocin (AVT) is the non-mammalian homolog of arginine vasopressin (AVP) and, like vasopressin, serves as an important modulator of social behavior in addition to its peripheral functions related to osmoregulation, reproductive physiology, and stress hormone release. In amphibians and reptiles, the neuroanatomical organization of brain AVT cells and fibers broadly resembles that seen in mammals and other taxa. Both parvocellular and magnocellular AVT-containing neurons are present in multiple populations located mainly in the basal forebrain from the accumbens-amygdala area to the preoptic area and hypothalamus, from which originate widespread fiber connections spanning the brain with a particularly heavy innervation of areas associated with social behavior and decision-making. As for mammalian AVP, AVT is present in greater amounts in males in many brain areas, and its presence varies seasonally, with hormonal state, and in males with differing social status. AVT's social influence is also conserved across herpetological taxa, with significant effects on social signaling and aggression, and, based on the very small number of studies investigating more complex social behaviors in amphibians and reptiles, AVT may also modulate parental care and social bonding when it is present in these vertebrates. Within this conserved pattern, however, both AVT anatomy and social behavior effects vary significantly across species. Accounting for this diversity represents a challenge to understanding the mechanisms by which AVT exerts its behavioral effects, as well are a potential tool for discerning the structure-function relationships underlying AVT's many effects on behavior.