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Copyright of Journal of Neotropical Mammalogy / Mastozoologia Neotropical is the property of Sociedad Argentina para el Estudio de los Mamiferos and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The acute phase response (APR), coordinated by a complex network of components of the immune and neuroendocrine systems, plays a key role in early immune defense. This response can be elicited by a wide variety of pathogens at different intensities (frequencies and doses), hence experimental immune challenges with antigen gradients makes it possible to evaluate sickness progression with a better representation of what occurs in natural systems. However, how infection intensity could shape the APR magnitude in wild species is still poorly understood. Here, the immune response was activated in the subterranean rodent Ctenomys talarum with a gradient of lipopolysaccharide (LPS) doses (0.5, 1, 1.5, and 2 mg/kg of body mass). Changes in body temperature, body mass, and energetic costs were evaluated over time. We also assessed cortisol levels, white blood cells counts and neutrophil: lymphocyte ratios, before and after injection. Results indicated that during the APR, C. talarum shows a hyperthermic response, which is maintained for 6 h, with slight differences among antigen doses in the pattern of thermal response and body mass change. A maximum increase in body temperature of 0.83°C to 1.63°C was observed during the first hour, associated with a metabolic cost that ranged from 1.25 to 1.41 ml O2/gh. Although no clear effects of treatment were detected on leukocyte abundance, we found increments in neutrophil: lymphocyte ratios and gradual increases in cortisol levels corresponding to the intensity of simulated infection, which may indicate redistribution of immune cells and enhancement of immune function. An evident sickness syndrome was observed even at the lowest LPS dose that was characterized by an increase in body temperature, energy expenditure, and N: L ratio, as well as a dose‐dependent increase in cortisol levels. Although in nature, other constraints and challenges could affect the magnitude and costs of immune responses, C. talarum mounts an effective APR with a low increase in their daily energy expenditure, regardless of LPS dose. Research Highlights: Acute‐phase immune response in Ctenomys talarum involves fever and increases in metabolic rate, N:L ratio and cortisol levels. Fever entails a considerable energy cost. The higher the antigen dose, the greater the increase in cortisol levels. [ABSTRACT FROM AUTHOR]

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.anbehav.2010.02.024 Byline: Roxana R. Zenuto Abstract: Individual recognition is expected to enhance fitness by allowing animals to direct appropriate behaviours to specific individuals during interactions with conspecifics. Reduced aggression towards territorial neighbours ('dear enemy phenomenon') is based on the assumption that strangers lacking territories pose a greater threat than territory-holding neighbours. Based on the ability of the subterranean rodent Ctenomys talarum (tuco-tuco) to distinguish between familiar and unfamiliar conspecific odours, I assessed whether males, the more aggressive sex, show dear enemy relationships and whether social experience with odour donors affects the memory of conspecific odours. Male-male contests in the laboratory were used to compare the aggressive behaviour of pairs of males. Familiar male tuco-tucos responded less aggressively during contests than unfamiliar males, providing evidence of the dear enemy relationship in C. talarum. Memory for familiar odours was affected by social experience since discrimination of known from novel odours lasted longer when males encountered each other in dyadic contests following familiarization with odours. Familiarity by odour cues would represent an important mechanism mediating neighbour recognition and territorial behaviour for tuco-tucos in the wild; intruders may represent a threat of great consequence for territory-holding individuals since they represent the potential loss of their burrow system and their priority of access to neighbouring females. Author Affiliation: Laboratorio de Ecofisiologia, Departamento de Biologia, Facultad de Ciencias Exactas y Naturales, Universidad Nacional de Mar del Plata, Consejo Nacional de Investigaciones Cientificas y Tecnicas, Argentina Article History: Received 20 July 2009; Revised 16 September 2009; Accepted 8 February 2010 Article Note: (miscellaneous) MS. number: A09-00484R

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.anbehav.2008.11.018 Byline: Matias E. Mastrangelo (a), Cristian E. Schleich (a)(b), Roxana R. Zenuto (a)(b) Abstract: Spatial memory is important for animals to achieve successful foraging, reproduction, territorial defence and predator avoidance in structurally complex habitats. This cognitive function has been shown to be affected under stress conditions in surface-dwelling rodents. Here we used the Tala's tuco-tuco, Ctenomys talarum, a subterranean rodent that inhabits complex burrow systems, as a study model. This species has a highly developed spatial ability and individuals are regularly exposed to predatory stress while foraging on the surface. We examined the consequences of a single and brief exposure to predatory cues on the spatial working and reference memory performance. We trained wild-caught individuals (32 males, 36 females) in a six-arm radial maze (spatial working memory task) or a longitudinal maze (spatial reference memory task). Once the animals reached a memory performance criterion, they were exposed to a direct predatory cue (immobilization), an indirect predatory cue (cat urine odour) or both cues combined, and their memory performance was evaluated. Exposure to direct and combined predatory cues impaired spatial reference memory, increasing both the latency to achieve the goal and the number of errors during the test. Combined presentation of both predatory cues also negatively affected spatial working memory, but only for latency to achieve the goal. Our results suggest that use of spatial working memory during a predatory attack on the surface allows C. talarum to relocate burrow entries rapidly and hence increases survival probabilities. Author Affiliation: (a) Laboratorio de Ecofisiologia Animal, Facultad de Ciencias Exactas y Naturales, Universidad Nacional de Mar del Plata, Argentina (b) Consejo Nacional de Investigaciones Cientificas y Tecnicas (CONICET), Buenos Aires, Argentina Article History: Received 24 August 2008; Revised 10 October 2008; Accepted 18 November 2008 Article Note: (miscellaneous) MS. number: A08-00555

Abstract: Biological odors that convey cues regarding individual identity are known to alter mating behavior in some rodents. Deposition of chemical signals by males on the substrate could give females [...]

Background: Animal personalities have been studied in a wide variety of taxa, but among rodents, available studies are relatively scarce and have focused mainly on social species. In this study, we evaluated the existence of personality in the solitary subterranean rodent Ctenomys talarum. Specifically, we aimed to test individual differences in behavior that are stable over time and context in males of C. talarum captured in the wild. Methods: Our experimental design included two series of three behavioral tests each, carried out with a 35 day time interval. Each series included an Open Field test, a Social Encounter test, and an Open Field test with a predator stimulus. Results: Of the total recorded behaviors, 55.55% showed temporal consistency. Principal component analysis of consistent behaviors grouped them into four dimensions that explain inter individual behavioral variability, in order of importance: activity, socioaversion, boldness and exploration. Therefore, our results suggest that the concept of animal personality is applicable to C. talarum and the dimensions found are in accordance with the ecological and behavioral characteristics of this species. [ABSTRACT FROM AUTHOR]

Predation is a strong selective force, and prey species may show specific adaptations that allow recognition, avoidance, and defense against predators. Facing a situation of predatory risk, anxiety constitutes a reaction of adaptive value, allowing to evaluate the potential risk of this encounter as well as to generate a physiological and behavioral response. Previous studies in the subterranean rodent Ctenomys talarum revealed that exposure to predator odors (urine or fur) generates an anxiety state and induces behavioral changes. However, no differences between the responses generated by both odor sources were observed, although fur odors may indicate a higher level of predatory immanence. Therefore, the aim of this study was to evaluate the behavioral and physiological responses of C. talarum to different intensities of predator odors (urine and fur) and to the repeated exposition to the same odorous stimulus. When comparing the highest behavioral effects elicited by both predatory odors on C. talarum, our study supports the assumption that fur odors are more anxiogenic than urine, while the former provoked significant changes in the distance traveled, the number of arm entries and time in transparent arms in the elevated plus maze; cat urine only caused slight changes on those behavioral parameters. Furthermore, we also found that the intensity of natural predator odor presented to tuco-tucos has a role on the appearance of defensive behaviors, although an amount-dependent relationship between predator odor and anxiety levels was not observed. Finally, while individuals exposed for 1 day to fur odor displayed an evident anxiety state, those exposed repeatedly for 5 consecutive days did not differ with the control group in their behavioral response, indicating a clear habituation to the predatory cue. In our intensity and habituation experiments, we did not find differences in the measured physiological parameters among control individuals, exposed to different cues intensity (urine and fur odor) and exposed only once or for 5 days to fur odor. These results provide valuable evidence that the types of predatory odor, along with the frequency of exposition, are important determinants of the appearance, strength, and extinction of defensive behaviors in the subterranean rodent C. talarum. [ABSTRACT FROM AUTHOR]

ABSTRACT Magnitude and effectiveness of immune responses vary greatly between and within species. Among factors reported to determine this variation, parasitism is a critical one, although controversial effects of parasites over immunological indices have been reported. Information regarding immune strategies in species with different life histories is crucial to better understand the role of immune defenses in an ecological and evolutionary context. Here, we examine the influence of the parasite community on immune responsiveness of a solitary subterranean rodent, Ctenomys talarum. To do this, we assessed the impact of the natural parasite community and the experimental infection with Eimeria sp. on the phytohemagglutinin (PHA)-response, as well as other immune, condition, nutrition, and stress parameters. PHA-triggered inflammation was similarly impaired by Eimeria sp. infection alone or co-occurring with a number of gastrointestinal nematodes. None of the other physiological parameters studied were affected by parasitism. This indicates that parasitism is a general key factor modulating immune responsiveness of the host, and in particular for C. talarum, it could explain the great inter-individual variation previously observed in the PHA-response. Thus, our results highlight the importance of taking the parasite community into account in ecoimmunological studies, particularly when using immunological indices. J. Exp. Zool. 9999A:XX-XX, 2015. © 2015 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]